| 1. |
- Bothe, Wolfgang, et al.
(författare)
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Effects of acute ischemic mitral regurgitation on three-dimensional mitral leaflet edge geometry
- 2008
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Ingår i: European Journal of Cardio-Thoracic Surgery. - : Oxford University Press (OUP). - 1010-7940 .- 1873-734X. ; 33, s. 191-197
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Tidskriftsartikel (refereegranskat)abstract
- Background: Improved quantitative understanding of in vivo leaflet geometry in ischemic mitral regurgitation (IMR) is needed to improve reparative techniques, yet few data are available due to current imaging limitations. Using marker technology we tested the hypotheses that IMR (1) occurs chiefly during early systole; (2) affects primarily the valve region contiguous with the myocardial ischemic insult; and (3) results in systolic leaflet edge restriction. Methods: Eleven sheep had radiopaque markers sutured as five opposing pairs along the anterior (A1–E1) and posterior (A2–E2) mitral leaflet free edges from the anterior commissure (A1–A2) to the posterior commissure (E1–E2). Immediately postoperatively, biplane videofluoroscopy was used to obtain 4D marker coordinates before and during acute proximal left circumflex artery occlusion. Regional mitral orifice area (MOA) was calculated in the anterior (Ant-MOA), middle (Mid-MOA), and posterior (Post-MOA) mitral orifice segments during early systole (EarlyS), mid systole (MidS), and end systole (EndS). MOA was normalized to zero (minimum orifice opening) at baseline EndS. Tenting height was the distance of the midpoint of paired markers to the mitral annular plane at EndS. Results: Acute ischemia increased echocardiographic MR grade (0.5 ± 0.3 vs 2.3 ± 0.7, p < 0.01) and MOA in all regions at EarlyS, MidS, and EndS: Ant-MOA (7 ± 10 vs 22 ± 19 mm2, 1 ± 2 vs18 ± 16 mm2, 0 vs 17 ± 15 mm2); Mid-MOA (9 ± 13 vs 25 ± 17 mm2, 3 ± 6 vs 21 ± 19 mm2, 0 vs 25 ± 17 mm2); and Post-MOA (8 ± 10 vs 25 ± 16, 2 ± 4 vs 22 ± 13 mm2, 0 vs 23 ± 13 mm2), all p < 0.05. There was no change in MOA throughout systole (EarlyS vs MidS vs EndS) during baseline conditions or ischemia. Tenting height increased with ischemia near the central and the anterior commissure leaflet edges (B1–B2: 7.1 ± 1.8 mm vs 7.9 ± 1.7 mm, C1–C2: 6.9 ± 1.3 mm vs 8.0 ± 1.5 mm, both p < 0.05). Conclusions: MOA during ischemia was larger throughout systole, indicating that acute IMR in this setting is a holosystolic phenomenon. Despite discrete postero-lateral myocardial ischemia, Post-MOA was not disproportionately larger. Acute ovine IMR was associated with leaflet restriction near the central and the anterior commissure leaflet edges. This entire constellation of annular, valvular, and subvalvular ischemic alterations should be considered in the approach to mitral repair for IMR.
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| 2. |
- Carlhäll, Carljohan, et al.
(författare)
-
Alterations in transmural myocardial strain - An early marker of left ventricular dysfunction in mitral regurgitation?
- 2008
-
Ingår i: Circulation. - 0009-7322 .- 1524-4539. ; 118:14, s. S256-S262
-
Tidskriftsartikel (refereegranskat)abstract
- Background-In asymptomatic patients with severe isolated mitral regurgitation (MR), identifying the onset of early left ventricular (LV) dysfunction can guide the timing of surgical intervention. We hypothesized that changes in LV transmural myocardial strain represent an early marker of LV dysfunction in an ovine chronic MR model. Methods and Results-Sheep were randomized to control (CTRL, n = 8) or experimental (EXP, n = 12) groups. In EXP, a 3.5-or 4.8-mm hole was created in the posterior mitral leaflet to generate "pure" MR. Transmural beadsets were inserted into the lateral and anterior LV wall to radiographically measure 3-dimensional transmural strains during systole and diastolic filling, at 1 and 12 weeks postoperatively. MR grade was higher in EXP than CTRL at 1 and 12 weeks (3.0 [2-4] versus 0.5 [0-2], 3.0 [1-4] versus 0.5 [0-1], respectively, both P < 0.001). At 12 weeks, LV mass index was greater in EXP than CTRL (201 +/- 18 versus 173 +/- 17 g/m(2), P < 0.01). LVEDVI increased in EXP from 1 to 12 weeks (P = 0.015). Between the 1 and 12 week values, the change in BNP (-4.5 +/- 4.4 versus-3.0 +/- 3.6 pmol/L), PRSW (9 +/- 13 versus 23 +/- 18 mm Hg), tau (-3 +/- 11 versus-4 +/- 7 ms), and systolic strains was similar between EXP and CTRL. The changes in longitudinal diastolic filling strains between 1 and 12 weeks, however, were greater in EXP versus CTRL in the subendocardium (lateral:-0.08 +/- 0.05 versus 0.02 +/- 0.14, anterior:-0.10 +/- 0.05 versus-0.02 +/- 0.07, both P < 0.01). Conclusions-Twelve weeks of ovine "pure" MR caused LV remodeling with early changes in LV function detected by alterations in transmural myocardial strain, but not by changes in BNP, PRSW, or tau.
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| 3. |
- Itoh, Akinobu, et al.
(författare)
-
Active stiffening of mitral valve leaflets in the beating heart
- 2009
-
Ingår i: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY. - : American Physiological Society. - 0363-6135 .- 1522-1539. ; 296:6, s. H1766-H1773
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Tidskriftsartikel (refereegranskat)abstract
- The anterior leaflet of the mitral valve (MV), viewed traditionally as a passive membrane, is shown to be a highly active structure in the beating heart. Two types of leaflet contractile activity are demonstrated: 1) a brief twitch at the beginning of each beat (reflecting contraction of myocytes in the leaflet in communication with and excited by left atrial muscle) that is relaxed by midsystole and whose contractile activity is eliminated with beta-receptor blockade and 2) sustained tone during isovolumic relaxation, insensitive to beta-blockade, but doubled by stimulation of the neurally rich region of aortic-mitral continuity. These findings raise the possibility that these leaflets are neurally controlled tissues, with potentially adaptive capabilities to meet the changing physiological demands on the heart. They also provide a basis for a permanent paradigm shift from one viewing the leaflets as passive flaps to one viewing them as active tissues whose complex function and dysfunction must be taken into account when considering not only therapeutic approaches to MV disease, but even the definitions of MV disease itself.
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| 4. |
- Nguyen, Tom c., et al.
(författare)
-
The effect of pure mitral regurgitation on mitral annular geometry and three-dimensional saddle shape
- 2008
-
Ingår i: Journal of Thoracic and Cardiovascular Surgery. - : Elsevier BV. - 0022-5223 .- 1097-685X. ; 136:3, s. 557-565
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Chronic ischemic mitral regurgitation is associated with mitral annular dilatation in the septal-lateral dimension and flattening of the annular 3-dimensional saddle shape. To examine whether these perturbations are caused by the ischemic insult, mitral regurgitation, or both, we investigated the effects of pure mitral regurgitation (low pressure volume overload) on annular geometry and shape. Methods: Eight radiopaque markers were sutured evenly around the mitral annulus in sheep randomized to control (CTRL, n = 8) or experimental (HOLE, n = 12) groups. In HOLE, a 3.5- to 4.8-mm hole was punched in the posterior leaflet to generate pure mitral regurgitation. Four-dimensional marker coordinates were obtained radiographically 1 and 12 weeks postoperatively. Mitral annular area, annular septal-lateral and commissure-commissure dimensions, and annular height were calculated every 16.7 ms. Results: Mitral regurgitation grade was 0.4 ± 0.4 in CTRL and 3.0 ± 0.8 in HOLE (P < .001) at 12 weeks. End-diastolic left ventricular volume index was greater in HOLE at both 1 and 12 weeks, end-systolic volume index was larger in HOLE at 12 weeks. Mitral annular area increased in HOLE predominantly in the commissure-commissure dimension, with no difference in annular height between HOLE versus CTRL at 1 or 12 weeks, respectively. Conclusion: In contrast with annular septal-lateral dilatation and flattening of the annular saddle shape observed with chronic ischemic mitral regurgitation, pure mitral regurgitation was associated with commissure-commissure dimension annular dilatation and no change in annular shape. Thus, infarction is a more important determinant of septal-lateral dilatation and annular shape than mitral regurgitation, which reinforces the need for disease-specific designs of annuloplasty rings. © 2008 The American Association for Thoracic Surgery.
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| 5. |
- Bothe, Wolfgang, et al.
(författare)
-
Rigid, complete annuloplasty rings increase anterior mitral leaflet strain in normal beating ovine heart
- 2011
-
Ingår i: Circulation. - 0009-7322 .- 1524-4539. ; 124, s. S81-S96
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Annuloplasty ring or band implantation during surgical mitral valve repair perturbs mitral annular dimensions, dynamics, and shape, which have been associated with changes in anterior mitral leaflet (AML) strain patterns and suboptimal long-term repair durability. We hypothesized that rigid rings with nonphysiological three-dimensional shapes, but not saddle-shaped rigid rings or flexible bands, increase AML strains. METHODS AND RESULTS: Sheep had 23 radiopaque markers inserted: 7 along the anterior mitral annulus and 16 equally spaced on the AML. True-sized Cosgrove-Edwards flexible, partial band (n=12), rigid, complete St Jude Medical rigid saddle-shaped (n=12), Carpentier-Edwards Physio (n=12), Edwards IMR ETlogix (n=11), and Edwards GeoForm (n=12) annuloplasty rings were implanted in a releasable fashion. Under acute open-chest conditions, 4-dimensional marker coordinates were obtained using biplane videofluoroscopy along with hemodynamic parameters with the ring inserted and after release. Marker coordinates were triangulated, and the largest maximum principal AML strains were determined during isovolumetric relaxation. No relevant changes in hemodynamics occurred. Compared with the respective control state, strains increased significantly with rigid saddle-shaped annuloplasty ring, Carpentier-Edwards Physio, Edwards IMR ETlogix, and Edwards GeoForm (0.14 ± 0.05 versus 0.16 ± 0.05, P=0.024, 0.15 ± 0.03 versus 0.18 ± 0.04, P=0.020, 0.11 ± 0.05 versus 0.14 ± 0.05, P=0.042, and 0.13 ± 0.05 versus 0.16 ± 0.05, P=0.009), but not with Cosgrove-Edwards band (0.15 ± 0.05 versus 0.15 ± 0.04, P=0.973). CONCLUSIONS: Regardless of three-dimensional shape, rigid, complete annuloplasty rings, but not a flexible, partial band, increased AML strains in the normal beating ovine heart. Clinical studies are needed to determine whether annuloplasty rings affect AML strains in patients, and, if so, whether ring-induced perturbations in leaflet strain states are linked to repair failure.
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| 6. |
- Carlhäll, Carljohan, 1973-
(författare)
-
Annular dynamics of the human heart : novel echocardiographic approaches to assess ventricular function
- 2004
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The complex myocardial fiber architecture of the left ventricle (LV) enables long-axis motion (annular excursion), short-axis motion and also a small torsional deformation throughout the cardiac cycle. The contribution of the long-axis motion has proven to be important in generating ventricular filling and emptying, and the analysis of annular excursion has become a well established diagnostic tool for the assessment of ventricular function. Cardiac motion can be accurately described with modem non-invasive imaging teclmiques, and this is important ground for deeper understanding and more reliable diagnosis of cardiovascular disease. The focus of this thesis was to provide new insights into cardiac pump function using variables originating from the annular excursion and dynamic changes in shape, applying both established and novel echocardiographic imaging approaches.The traditional method of evaluating systolic ventricular fimction according to the total annular excursion overestimates the excursion amplitude in relation to true systolic fimction. A novel method presented here, measurement of the systolic annular excursion, more accurately reflects the timing of true systole, and was applied both in patients with heart disease and in healthy subjects. To date, the form of asynchronous myocardial motion called postsystolic shortening (PSS) has mainly been observed in the setting of myocardial ischemia. The significance of PSS in hypertensive heart disease remains incompletely described. We found that a subgroup of hypertensive patients with PSS along the LV long-axis had signs of more severe cardiac involvement unrelated to the level of blood pressure. Endurance trained subjects showed a larger LV long-axis motion as compared to strength trained and untrained controls. Mitral annular (MA) excursion correlated strongly to LV stroke volume, end-diastolic volume and maximal oxygen consumption per body weight, but weakly to LV ejection fraction. These findings provide further evidence of the importance of annular excursion to normal cardiac performance. In order to assess the contribution of MA excursion and shape dynamics to total LV volume change in humans, a novel 4-dimensional transesophageal echocardiography teclmique was developed. The excursion of the annulus accounted for an important portion (19±3%) of the total LV filling and emptying in healthy human subjects. Furthermore, our findings elucidate an atrial influence on MA physiology in humans, as well as a sphincter-like action of the MA. These temporal changes may facilitate ventricular filling by annular expansion during early and mid diastole, and aid competent valve closure during the marked decrease in annular area during late diastole and early systole.
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| 7. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Appendix A Marker Sites and Datafile Columns
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. A.1-A.3
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Datafiles (provided in this Appendix) associated with the six heart (H1-H6) study
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| 8. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Appendix B NAC-MAD Composite Dataset
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. B.1-B.2
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Here, we describe an attempt to model, as accurately as possible in 3-D space, the geometric relationship between the various components of the left ventricle, the mitral valve, and the aortic valve during systole and diastole.
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| 9. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Appendix C Computational Details
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. C.1-C.6
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 10. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Appendix D Mitral Valve Animations
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. D.1-D.1
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The PowerPoint mitral valve animations in this Appendix can be accessed by double-clicking the filenames. Both side view (LEFT PANEL, looking from posterior to anterior) and top view (RIGHT PANEL, looking from base to apex) are provided. All graphs have Marker #22 at the origin, Marker #1 on the Z-axis, and Marker #18 in the X-Z plane. The animations can be stepped forward with the right arrow and backwards with the left arrow with time-steps of 16.67 ms. The left ventricular pressure associated with each time step is indicated by the black dot on the LVP curve imbedded in the graph. Hit Escape to exit each animation. The H1-H6 datasets are located in Appendix A.
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| 11. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Appendix E COM Studies
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. E.1-E.1
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 12. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Appendix P Pull Study Markers, Datasets, Protocal Schematic
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. P.1-P.2
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The PULL STUDY (see results in Chapter 28) was designed to assess the effect of posterior leaflet pressure on anterior leaflet edge geometry in the closed valve. Figure P1 shows the marker array and coordinate system used in this study.
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| 13. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Appendix S SOD and DOS Studies
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. S.1-S.8
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- in two views of S2 sod04r02. Table S.2 defines the DOS marker anatomical locations and Figure S.3 illustrates these locations in D5 dos21r01. Table S.3 defines the markers delineating the space-filling tetrahedral for volume calculations. Figures S.4A-F display these tetrahedral within the left atrium and left ventricle of SOD hearts S1, S2, S3, S7, S9, and S10.
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| 14. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 01 Anatomy and Marker Sites
- 2016
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Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 1.1-1.3
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Figure 1.1 is a view from a 3-D rendering of systolic geometry for the left ventricle, mitral valve, and aortic valve, computed as a composite from two experiments involving precise measurement of 83 marker sites. The methods used to obtain this 3-D dataset, including the full dataset file, are outlined in Appendix B. Note that in this systolic rendering, the aortic valve is open and the mitral valve is closed.
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| 15. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 02 Fibrous Mitral Annulus
- 2016
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Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 2.1-2.2
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- A fibrous collagen wedge, pointing toward the left ventricle, separates the mitral valve and left atrium from the aortic valve. The portion of this wedge between the mitral and aortic valves is known as the aortic mitral curtain or the intervalvular fibrous curtain.
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| 16. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 03 Fibrous Annulus-Papillary Tip-LV Relationship
- 2016
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Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 3.1-3.12
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Figure 3.1 illustrates the geometric relationships between the LFT (Marker#29), APT (Marker#31), SH (Marker#22), RFT (Marker#24), and PPT (Marker#33) for diastole (left panel) and systole (right panel).
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| 17. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 07 Anterior Leaflet Chordal Safety Net
- 2016
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Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 7.1-7.4
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In this chapter, we provide evidence for another important role for the strut chordae, namely, to prevent the anterior mitral leaflet, particularly its leading edge, from encroaching beyond a certain point into the LV outflow tract during LV filling.
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| 18. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 12 Mitral LV Relationship
- 2016
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Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 12.1-12.7
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Figures 12.1-12.6 show the geometric relationships between the left ventricle and the mitral valve components for hearts H1-H6. The view is from the right fibrous trigone towards the left fibrous trigone, i.e., from the posterior wall of the LV towards the anterior wall. The best fit anterior leaflet plane is clamped to the X-Y axis for both the top frame (maximum LV inflow) and the bottom frame (maximum left ventricular pressure). LV markers #1-4 and # 8-13 are subepicardial; septal markers #5-7 are endocardial. The outflow tract is at lower right in each figure.
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| 19. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 14 Annular Size Variation
- 2016
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Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 14.1-14.3
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In this chapter, we visualize the valve along the Z-axis for the six hearts H1-H6, looking from the left atrium toward the left ventricle, clamping the best-fit annular plane to the X-Y axis. All scales are in mm.
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| 20. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 15 Annular and Anterior Leaflet Area and Perimeter
- 2016
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Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 15.1-15.4
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Figure 15.1 shows mitral annular and anterior leaflet areas throughout sequential cardiac cycles for hearts H1-H6. The mitral annular area displayed in these figures is the projected annular area in the X-Y plane with the best-fit annular plane clamped to the X-Y axis for each frame. It is calculated as the sum of all the triangular areas from adjacent annular marker projections to the projection of the annular midpoint in that frame.
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| 21. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 16 LV-Mitral Annular Coupling
- 2016
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Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 16.1-16.8
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The mitral leaflets hinges define the mitral annulus, thus changes in mitral annular dimensions impact leaflet opening, closing, and coaptation. At least six forces influence mitral annular dimensions, including left ventricular pressure, left atrial pressure, left heart blood flow, left atrial contraction, left ventricular contraction, and mitral chordae. In this chapter we postulate a working hypothesis concerning the impact of these forces on mitral annular dimensions throughout the cardiac cycle.
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| 22. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 18 Annular and Leaflet Shape and Planarity
- 2016
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Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 18.1-18.3
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Annular shape change in each heart was quantified by fitting (as described in Appendix C) a best-fit plane to all annulus markers (#15-#30) for each frame (f) during the three consecutive beats studied. The distance (Z) from each annulus marker (m) to this plane in each frame Z(f,m) was then obtained and the standard deviation of Z(f,m) computed for that frame as ZSD(f). This process was repeated for just the contractile annulus markers (#16-#20; #24-#29). A systolic average, Zavg(m), was then obtained for all annulus markers using all frames from mitral valve closing (MVC) to opening (MVO) for all three beats. For each frame, and each marker, the difference Z(f,m)-Zavg(m) was then computed and squared. The square root of the mean of these differences for all markers was then obtained for each frame as Zrms(f).
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| 23. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 19 Hinge Chordae
- 2016
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Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 19.1-19.7
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Each posterior leaflet annular radiopaque marker was surgically placed under direct observation at the posterior leaflet hinge points, where tissues associated with the left atrium and left ventricle meet the base of the leaflets. In this book, we define the mitral annulus as the locus of these hinge points, as did Angelini, et al.
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| 24. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 20 Papillary Vectors
- 2016
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Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 20.1-20.11
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In this chapter (and the next) we analyze papillary mechanics for the F-series of experiments (See Appendix F), where papillary tip and base markers were placed inside the ventricle under direct visualization during cardiopulmonary bypass, allowing better measurement of papillary muscle lengths. In these hearts (F1-F11) the anterior papillary tip was assigned Marker #31, its base #32; the posterior papillary tip #33, its base #34. Muscle fibers are aligned along the long axes of papillary muscles, thus papillary muscle contractile force is exerted primarily along these axes. In this chapter, because the papillary muscle tips are connected via hinge chordae to the mitral annulus, we explore the orientation of these axes with respect to sites around the mitral annulus.
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| 25. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 23 Posterior Mitral Leaflet Anatomy and Marker Sites
- 2016
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Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 23.1-23.3
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In this and the next several chapters we conduct a more complete study of the dynamics of the posterior leaflet(s) employing datasets from hearts with 9 markers on the posterior leaflet edges and 10 markers on the anterior leaflet. These datasets and animations arising from them are given in Appendix E.
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| 26. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 24 Posterior Leaflet Open
- 2016
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Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 24.1-24.3
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- We begin by examining the maximum extent of posterior leaflet opening relative to the mitral annulus. To view this, in each sample frame we performed a translation to place Marker #22 at the origin, perform 2 rotations to place Marker #18 on the x-axis, then performed a final rotation to place anterior commissure Marker #16 into the x-y plane. This placed the mitral annulus into the x-y plane (to very close approximation) at each sample time. We then view the resulting mitral valve geometry along the z-axis, looking from the left atrium toward the left ventricle. Appendix E provides frame-by-frame animations showing the geometry of the mitral valve as described by three-dimensional cubic splines passing through connected marker locations during a representative beat (from maximum LVP in one beat to maximum LVP in the following beat) for the hearts studied in this fashion.
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| 27. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 27 Coaptation
- 2016
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Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 27.1-27.3
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In Chapter 26 we identified two major pleats at the P1/P2 and P2/P3 junctions of the posterior leaflet, characterized their kinematics throughout the cardiac cycle, and approximated their surfaces with two filled (red and blue) triangular surfaces. These triangles, however, are only intended as a visualization device; we know that the actual pleats in the closed valve would bow inward toward one another as systolic left ventricular pressure acts on their outer ventricular surfaces to press their convex faces tightly together. We cannot appreciate such curvature in these studies, however, because of the limited spatial resolution of our sparse marker arrays.
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| 28. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 30 Active Anterior Leaflet
- 2016
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Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 30.1-30.3
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Mitral valve leaflets have long been considered as passive flaps. The findings described in Chapter 29 suggest otherwise, but the possibility that the large stiffness of the anterior leaflet arises simply from leaflet residual strains that place passive leaflet elastic elements into the post-transitional nonlinear region of their stress-strain curves must be considered. In the nonlinear stress-strain curves obtained by May-Newman and Yin1 from excised mitral leaflets (Figure 29.1) this requires residual stretch of roughly 15% or more for the anterior leaflet.
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| 29. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 31 Valvular Interstitial Cells
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 31.1-31.1
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The stiffening "twitch" of the annular half of the anterior mitral leaflet at the beginning of each beat likely arises from P-wave-stimulated, β-dependent, neurally-insensitive myocytes located in this region. The source of the ubiquitous, β-independent, neurally-sensitive, steady-state stiffness "tone" of the entire anterior leaflet is less clear, but may involve contractile Valvular Interstitial Cells (VICs) bound to leaflet collagen by α2β1 integrins, as discussed by Stephens et al.
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| 30. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 33 Leaflet Angles and Separation
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 33.1-33.2
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In this chapter we explore the opening and closing behavior of the anterior and posterior leaflets whose hinge regions define the mitral annulus.
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| 31. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 34 Left Ventricular Flow
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 34.1-34.5
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In this chapter we examine the relationship of anterior and posterior leaflet edge mobility to left ventricular inflow (quantified as described in Appendix C) and pressure.
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| 32. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 36 Coaptation Repeatability and Rigidity
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 36.1-36.8
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Competent mitral valve closure requires tight coaptation of the edge surfaces of the anterior and posterior leaflets. This chapter explores the precision with which specific sites on these surfaces are geometrically aligned at the beginning of each beat (repeatability) and the precision with which this alignment is maintained throughout left ventricular ejection (rigidity).
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| 33. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 37: Four Balloons
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 37.1-37.7
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In this chapter, we metaphorically characterize the mitral leaflets as segments of four inflated balloons pressed together on the ventricular side of the mitral annulus in such a geometric configuration as to preclude their crowding through the mitral annulus into the left atrium. The greater the inflation pressure (LVP), the more firmly the balloon interfaces press together, the more impossible it becomes to crowd this assemblage through the annulus.
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| 34. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 38 The Commissures
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 38.1-38.5
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The anterior commissure is the junctional region between the anterior leaflet and the P1 scallop of the posterior leaflet (Markers 1, 2, 3, and 16 in Figure 38.1; fold 3 in Figure 27.1). Figures 38.2 and 38.3 show individual frames from an animation of anterior commissure data during a representative heartbeat in COM07R04 with the valve closed, and open, respectively.The posterior commissure is the junctional region between the anterior leaflet and the P3 scallop of the posterior leaflet (Markers 12, 13, 14, and 20 in Figure 38.1; fold 4 in Figure 27.1). Figures 38.4 and 38.5 show Individual frames from an animation of posterior commissure data during the same heartbeat in COM07R04 with the valve closed, and open, respectively.
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| 35. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 39 Suspends, Belt
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 39.1-39.7
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In Chapter 36 we noted that the anterior leaflet edge is roughly fixed in position throughout systole and in Chapter 28 that this edge position is almost independent of its interaction with the posterior leaflet. This suggests that effective coaptation requires the posterior leaflet to conform tightly to the edge of the stiff anterior leaflet. In this chapter, again employing the data in Appendix E, we suggest that the posterior leaflet folds are important for this task.
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| 36. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 40 Leaflet Tent
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 40.1-40.3
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The concept of the closed mitral valve forming a tent-like structure is well-known in the literature. The mitral annulus forms the "floor" of the tent and the leaflets form the tent "walls" that extend from the annulus into the LV. In this chapter we build on this concept, utilizing concepts developed from our findings in earlier chapters based on 4-D marker data.
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| 37. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 41 P2 Shape and Tertiary Chords
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 41.1-41.5
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter tests the hypothesis that the central belly of the P2 posterior leaflet deforms as an unsupported elastic membrane subjected to left ventricular pressure in the closed valve. This hypothesis produces at least three marker-testable predictions: first, that radial leaflet curvature is concave to the left ventricle throughout ejection; second, that this curvature changes very little during the nearly constant systolic pressure during ejection; and third, that this curvature flattens as LVP falls precipitously during isovolumic relaxation.
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| 38. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Chapter 43 The Normal Valve-Concept Summaries
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. 43.1-43.5
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The following are brief summaries of concepts underlying normal mitral valve mechanics that we find most compatible with the currently available data. Chapters developing and supporting these concepts are identified at the end of each summary.
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| 39. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Introduction
- 2016
-
Ingår i: Mitral Valve Mechanics. - : Linköping University Electronic Press. - 9789176859520 ; , s. i-viii
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The goal of this book is to develop a working hypothesis for mitral valve function in the beating heart. We have been studying the 4-D dynamics of the heart using biplane radiography of surgically implanted radiopaque markers for the past forty years,1 with emphasis on the mitral and aortic valves during the past 20 years, and dense leaflet and annular marker arrays during the past several years. Data from the control runs in these studies comprise the substrate for this book.
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| 40. |
- Ingels, Jr, Neil B, et al.
(författare)
-
Mitral Valve Mechanics
- 2016
-
Bok (övrigt vetenskapligt/konstnärligt)abstract
- The goal of this book is to develop a working hypothesis for mitral valve function in the beating heart. We have been studying the 4-D dynamics of the heart using biplane radiography of surgically implanted radiopaque markers for the past forty years,1 with emphasis on the mitral and aortic valves during the past 20 years, and dense leaflet and annular marker arrays during the past several years. Data from the control runs in these studies comprise the substrate for this book.
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| 41. |
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| 42. |
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| 43. |
- Kindberg, Katarina, 1977-, et al.
(författare)
-
Myocardial strains from 3D DENSE magnetic resonance imaging
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The ability to measure and quantify myocardial motion and deformation provides a useful tool to assist in the diagnosis, prognosis and management of heart disease. The recent development of magnetic resonance imaging methods, such as harmonic phase and displacement encoding with stimulated echoes (DENSE), make detailed non-invasive 3D transmural kinematic analyses of human myocardium possible in the clinic and for research purposes. As data acquisition technologies improve, quantification methods for cardiac kinematics need to be adapted and validated on the new types of data. In the present paper, a previously presented polynomial method for cardiac strain quantification is extended to quantify 3D strains from DENSE magnetic resonance imaging data. The method yields accurate results when validated against an analytical standard, and is applied to in vivo data from a healthy human heart. The polynomial field is capable of resolving the measured material positions from the in vivo data, and the obtained in vivo strains agree
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| 44. |
- Kindberg, Katarina, et al.
(författare)
-
Myocardial strains from 3D displacement encoded magnetic resonance imaging
- 2012
-
Ingår i: BMC Medical Imaging. - : BioMed Central. - 1471-2342. ; 12:9
-
Tidskriftsartikel (refereegranskat)abstract
- BackgroundThe ability to measure and quantify myocardial motion and deformation provides a useful tool to assist in the diagnosis, prognosis and management of heart disease. The recent development of magnetic resonance imaging methods, such as harmonic phase analysis of tagging and displacement encoding with stimulated echoes (DENSE), make detailed non-invasive 3D kinematic analyses of human myocardium possible in the clinic and for research purposes. A robust analysis method is required, however.MethodsWe propose to estimate strain using a polynomial function which produces local models of the displacement field obtained with DENSE. Given a specific polynomial order, the model is obtained as the least squares fit of the acquired displacement field. These local models are subsequently used to produce estimates of the full strain tensor.ResultsThe proposed method is evaluated on a numerical phantom as well as in vivo on a healthy human heart. The evaluation showed that the proposed method produced accurate results and showed low sensitivity to noise in the numerical phantom. The method was also demonstrated in vivo by assessment of the full strain tensor and to resolve transmural strain variations.ConclusionsStrain estimation within a 3D myocardial volume based on polynomial functions yields accurate and robust results when validated on an analytical model. The polynomial field is capable of resolving the measured material positions from the in vivo data, and the obtained in vivo strains values agree with previously reported myocardial strains in normal human hearts.
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| 45. |
- Kindberg, Katarina, 1977-, et al.
(författare)
-
Strain based estimation of time dependent transmural myocardial architecture in the ovine heart
- 2010
-
Ingår i: Biomechanics and Modeling in Mechanobiology. - : SpringerLink. - 1617-7959 .- 1617-7940. ; 10:4, s. 521-528
-
Tidskriftsartikel (refereegranskat)abstract
- Left ventricular myofibers are connected by an extensive extracellular collagen matrix to form myolaminar sheets. Histological cardiac tissue studies have previously observed a pleated transmural distribution of sheets in the ovine heart, alternating sign of the sheet angle from epicardium to endocardium. The present study investigated temporal variations in myocardial fiber and sheet architecture during the cardiac cycle. End diastolic histological measurements made at subepicardium, midwall and subendocardium at an anterior-basal and a lateral-equatorial region of the ovine heart, combined with transmural myocardial Lagrangian strains, showed that the sheet angle but not the fiber angle varied temporally throughout the cardiac cycle. The magnitude of the sheet angle decreased during systole at all transmural depths at the anterior-basal site and at midwall and subendocardium depths at the lateral-equatorial site, making the sheets more parallel to the radial axis. These results support a previously suggested accordion-like wall thickening mechanism of the myocardial sheets.
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| 46. |
- Krishnamurthy, Gaurav, et al.
(författare)
-
Stress-strain behavior of mitral valve leaflets in the beating ovine heart
- 2009
-
Ingår i: JOURNAL OF BIOMECHANICS. - : Elsevier BV. - 0021-9290. ; 42:12, s. 1909-1916
-
Tidskriftsartikel (refereegranskat)abstract
- Excised anterior mitral leaflets exhibit anisotropic, non-linear material behavior with pre-transitional stiffness ranging from 0.06 to 0.09 N/mm(2) and post-transitional stiffness from 2 to 9 N/mm(2). We used inverse finite element (FE) analysis to test, for the first time, whether the anterior mitral leaflet (AML), in vivo, exhibits similar non-linear behavior during isovolumic relaxation (IVR). Miniature radiopaque markers were sewn to the mitral annulus, AML, and papillary muscles in 8 sheep. Four-dimensional marker coordinates were obtained using biplane videofluoroscopic imaging during three consecutive cardiac cycles. A FE model of the AML was developed using marker coordinates at the end of isovolumic relaxation (when pressure difference across the valve is approximately zero), as the reference state. AML displacements were simulated during IVR using measured left ventricular and atrial pressures. AML elastic moduli in the radial and circumferential directions were obtained for each heartbeat by inverse FEA, minimizing the difference between simulated and measured displacements. Stress-strain curves for each beat were obtained from the FE model at incrementally increasing transmittal pressure intervals during IVR. Linear regression of 24 individual stress-strain curves (8 hearts, 3 beats each) yielded a mean (+/- SD) linear correlation coefficient (r(2)) of 0.994 +/- 0.003 for the circumferential direction and 0.995 +/- 0.003 for the radial direction. Thus, unlike isolated leaflets, the AML, in vivo, operates linearly over a physiologic range of pressures in the closed mitral valve.
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| 47. |
- Nguyen, Tom, et al.
(författare)
-
Functional uncoupling of the mitral annulus and left ventricle with mitral regurgitation and dopamine
- 2008
-
Ingår i: Journal of Heart Valve Disease. - 0966-8519 .- 2053-2644. ; 17, s. 168-178
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The mitral annulus and left ventricle are generally thought to be functionally coupled, in the sense that increases in left ventricular (LV) size, as seen in ischemic mitral regurgitation (MR), or decreases in LV size, as seen with inotropic stimulation, are thought to increase or decrease annular dimensions in similar manner. The study aim was to elucidate the functional relationship between the mitral annulus and left ventricle during acute MR and inotrope-induced MR reduction.METHODS: Radiopaque markers were implanted on the left ventricle and mitral annulus of five adult sheep. A suture was placed on the central scallop of the posterior mitral leaflet and exteriorized through the atrial-ventricular groove. Open-chest animals were studied at baseline (CTRL), at seconds after pulling on the suture to create moderate-severe 'pure' MR (PULL), and after titration of dopamine until the MR grade was maximally reduced (PULL+DOPA). This process was repeated two to three times for each animal.RESULTS: The MR grade was increased with PULL (from 0.5 +/- 0.01 to 3.4 +/- 0.4, p < 0.01) and decreased after PULL+DOPA (from 3.4 +/- 0.4 to 1.5 +/- 0.9, p < 0.001). PULL resulted in an increase in mitral annular (MA) area, predominantly by an increase in the muscular mitral annulus. PULL+DOPA caused a decrease in MA area, but the LV volume and dimensions were not altered with either PULL or PULL+DOPA.CONCLUSION: The acute geometric response to 'pure' MR and inotrope-induced MR reduction was limited to the mitral annulus. Surprisingly, the LV volume and dimensions did not change with acute MR or with inotrope-induced MR reduction. This suggests that, under these two conditions in an ovine model, the mitral annulus and left ventricle are functionally uncoupled.
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| 48. |
- Rausch, Manuel K., et al.
(författare)
-
Characterization of mitral valve annular dynamics in the beating heart
- 2011
-
Ingår i: Annals of Biomedical Engineering. - New York : Springer-Verlag New York. - 0090-6964 .- 1573-9686. ; 39:6, s. 1690-1702
-
Tidskriftsartikel (refereegranskat)abstract
- The objective of this study is to establish a mathematical characterization of the mitral valve annulus that allows a precise qualitative and quantitative assessment of annular dynamics in the beating heart. We define annular geometry through 16 miniature markers sewn onto the annuli of 55 sheep. Using biplane videofluoroscopy, we record marker coordinates in vivo. By approximating these 16 marker coordinates through piecewise cubic splines, we generate a smooth mathematical representation of the 55 mitral annuli. We time-align these 55 annulus representations with respect to characteristic hemodynamic time points to generate an averaged baseline annulus representation. To characterize annular physiology, we extract classical clinical metrics of annular form and function throughout the cardiac cycle. To characterize annular dynamics, we calculate displacements, strains, and curvature from the discrete mathematical representations. To illustrate potential future applications of this approach, we create rapid prototypes of the averaged mitral annulus at characteristic hemodynamic time points. In summary, this study introduces a novel mathematical model that allows us to identify temporal, regional, and inter-subject variations of clinical and mechanical metrics that characterize mitral annular form and function. Ultimately, this model can serve as a valuable tool to optimize both surgical and interventional approaches that aim at restoring mitral valve competence.
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| 49. |
- Swanson, Julia C., et al.
(författare)
-
Electro-Mechanical coupling between the atria and the mitral valve
- 2011
-
Ingår i: American Journal of Physiology. - : American Physiological Society. - 0002-9513 .- 2163-5773. ; 300:4, s. H1267-H1273
-
Tidskriftsartikel (refereegranskat)abstract
- Anterior leaflet (AL) stiffening during isovolumic contraction (IVC) may aid mitral valve closure. We tested the hypothesis that AL stiffening requires atrial depolarization. Ten sheep had radioopaque-marker arrays implanted in the left ventricle, mitral annulus, AL, and papillary muscle tips. Four-dimensional marker coordinates (x, y, z, and t) were obtained from biplane videofluoroscopy at baseline (control, CTRL) and during basal interventricular-septal pacing (no atrial contraction, NAC; 110-117 beats/min) to generate ventricular depolarization not preceded by atrial depolarization. Circumferential and radial stiffness values, reflecting force generation in three leaflet regions (annular, belly, and free-edge), were obtained from finite-element analysis of AL displacements in response to transleaflet pressure changes during both IVC and isovolumic relaxation (IVR). In CTRL, IVC circumferential and radial stiffness was 46 ± 6% greater than IVR stiffness in all regions (P < 0.001). In NAC, AL annular IVC stiffness decreased by 25% (P = 0.004) in the circumferential and 31% (P = 0.005) in the radial directions relative to CTRL, without affecting edge stiffness. Thus AL annular stiffening during IVC was abolished when atrial depolarization did not precede ventricular systole, in support of the hypothesis. The likely mechanism underlying AL annular stiffening during IVC is contraction of cardiac muscle that extends into the leaflet and requires atrial excitation. The AL edge has no cardiac muscle, and thus IVC AL edge stiffness was not affected by loss of atrial depolarization. These findings suggest one reason why heart block, atrial dysrhythmias, or ventricular pacing may be accompanied by mitral regurgitation or may worsen regurgitation when already present.
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| 50. |
- Swanson, Julia C., et al.
(författare)
-
Multiple mitral leaflet contractile systems in the beating heart
- 2011
-
Ingår i: Journal of Biomechanics. - : Elsevier BV. - 0021-9290 .- 1873-2380. ; 44:7, s. 1328-1333
-
Tidskriftsartikel (refereegranskat)abstract
- Mitral valve closure may be aided by contraction of anterior leaflet (AL) cardiac myocytes located in the annular third of the leaflet. This contraction, observed as a stiffening of the annular region of the AL during isovolumic contraction (IVC), is abolished by beta-blockade (βB). Sub-threshold rapid pacing in the region of aorto-mitral continuity (STIM) also causes AL stiffening, although this increases the stiffness of the entire leaflet during both IVC and isovolumic relaxation (IVR). We investigated whether these contractile events share a common pathway or whether multiple AL contractile mechanisms may be present. Ten sheep had radiopaque-markers implanted: 13 silhouetting the LV, 16 on the mitral annulus, an array of 16 on the AL, and one on each papillary muscle tip. 4-D marker coordinates were obtained from biplane videofluoroscopy during control (C), βB (esmolol) and during βB+STIM. Circumferential and radial stiffness values for three AL regions (Annular, Belly, and free-Edge), were obtained from inverse finite element analysis of AL displacements in response to trans-leaflet pressure changes during IVC and IVR. βB+STIM increased stiffness values in all regions at both IVC and IVR by 35 ± 7% relative to βB (p<0.001). Thus, even when AL myocyte contraction was blocked by βB, STIM stiffened all regions of the AL during both IVC and IVR. This demonstrates the presence of at least two contractile systems in the AL; one being the AL annular cardiac muscle, involving a β-dependent pathway, others via a β-independent pathway, likely involving valvular interstitial cells and/or AL smooth muscle cells.
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