| 1. |
- Aburawi, Elhadi, et al.
(författare)
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Effects of cardio-pulmonary bypass surgery on coronary flow in children assessed with transthoracic Doppler echocardiography.
- 2007
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Ingår i: American Journal of Physiology: Heart and Circulatory Physiology. - : American Physiological Society. - 1522-1539 .- 0363-6135. ; 293:2, s. 1138-1143
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Tidskriftsartikel (refereegranskat)abstract
- Perturbation of coronary blood flow (CF) is an important contributor to myocardium-related complications. The study was primarily designed to assess the impact of cardiopulmonary bypass (CPB) surgery on CF by aid of transthoracic Doppler echocardiography. Changes in CF after off-pump coarctation surgery were also studied. All ultrasounds were performed before and 5 ± 1 days after surgery. Eighteen children underwent CPB surgery of ventricular left-to-right shunts at the mean age of 6 mo, while off-pump surgery (aortic coarctectomy) was undertaken at the mean age of 10 days in 12 children. After CPB surgery, both left anterior descending coronary artery mean diameter and basal CF increased from 1.7 ± 0.3 to 2.1 ± 0.4 mm (P = 0.001) and 27 ± 10 to 47 ± 15 ml/min (P = 0.0001), respectively. These two coronary variables decreased after off-pump coarctectomy: left anterior descending coronary artery mean diameter from 1.8 ± 0.1 to 1.7 ± 0.1 mm (P = 0.06), and CF from 44 ± 12 to 25 ± 8 ml/min (P = 0.001). The findings are in keeping with the hypothesis that the previously reported impairment of coronary flow reserve after CPB surgery could be due to increase in basal coronary flow after CPB. Off-pump coarctectomy seems to have little impact on CF, as the postsurgical decline in flow in these patients seems to relate to the reduction in cardiac pressure afterload.
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| 2. |
- Akhter, Tansim, 1967-, et al.
(författare)
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Artery Wall Layer Dimensions during Normal Pregnancy : A longitudinal study using non-invasive high-frequency ultrasound
- 2013
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Ingår i: American Journal of Physiology. Heart and Circulatory Physiology. - : American Physiological Society. - 0363-6135 .- 1522-1539. ; 304:2, s. H229-H234
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Tidskriftsartikel (refereegranskat)abstract
- The vascular effects of normal pregnancy were investigated by estimating the intima and media thicknesses of the common carotid artery separately using 22MHz ultrasound (Collagenoson, Meudt, Germany) in 57 healthy women with normal pregnancies and pregnancy outcomes, in all three trimesters and at one year postpartum. A thick intima, thin media and high intima/media (I/M) ratio are signs of a less healthy artery wall. The mean artery wall layer dimensions remained fairly constant during pregnancy but the intima thickness and I/M thickness ratio appeared to improve (decrease) postpartum (p<0.001 for both). The cardiovascular risk parameters age, body mass index (BMI), and blood pressure in the first trimester were associated with higher I/M ratios, especially in the second trimester, whereas higher serum estradiol levels were significantly associated with a lower I/M ratio. Changes from the first to second trimesters in I/M ratio, taking into account differential changes in intima and media thickness, were significantly (p<0.05-0.001) associated with all risk parameters tested except age, which was associated with increased intima thickness (p=0.02). Associations with third trimester values and changes from first to third trimesters were similar but less apparent. Thus, fairly constant mean artery wall layer dimensions during pregnancy appeared to improve postpartum. However, higher age, BMI or blood pressure, and lower serum estradiol levels in the first trimester appeared to negatively affect the artery wall, strongly suggesting that pregnancy has negative vascular effects in some women. A less likely explanation involves possible adaptation to physiological changes during and after pregnancy.
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| 3. |
- Ansar, Saema, et al.
(författare)
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Cerebrovascular ETB, 5-HT1B and AT1 Receptor Upregulation Correlates with Reduction in Regional CBF after Subarachnoid Hemorrhage.
- 2007
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Ingår i: American Journal of Physiology: Heart and Circulatory Physiology. - : American Physiological Society. - 1522-1539 .- 0363-6135. ; 293:6, s. 3750-3758
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Tidskriftsartikel (refereegranskat)abstract
- We hypothesize that cerebral ischemia leads to enhanced expression of endothelin (ET), 5-hydroxytryptamine (5-HT), and angiotensin II (ANG II) receptors in the vascular smooth muscle cells. Our aim is to correlate the upregulation of cerebrovascular receptors and the underlying molecular mechanisms with the reduction in regional and global cerebral blood flow (CBF) after subarachnoid hemorrhage (SAH). SAH was induced by injecting 250 µl blood into the prechiasmatic cistern in rats. The cerebral arteries were removed 0, 1, 3, 6, 12, 24, and 48 h after the SAH for functional and molecular studies. The contractile responses to ET-1, 5-carboxamidotryptamine (5-CT), and ANG II were investigated with myograph. The receptor mRNA and protein levels were analyzed by quantitative real-time PCR and immunohistochemistry, respectively. In addition, regional and global CBFs were measured by an autoradiographic method. As a result, SAH resulted in enhanced contractions to ET-1 and 5-CT. ANG II [via ANG II type 1 (AT1) receptors] induced increased contractile responses [in the presence of the ANG II type 2 (AT2) receptor antagonist PD-123319]. In parallel the ETB, 5-HT1B, and AT1 receptor, mRNA and protein levels were elevated by time. The regional and global CBF showed a successive reduction with time after SAH. In conclusion, the results demonstrate for the first time that SAH induces the upregulation of ETB, 5-HT1B, and AT1 receptors in a time-dependent manner both at functional, mRNA, and protein levels. These changes occur in parallel with a successive decrease in CBF. Thus there is a temporal correlation between the changes in receptor expression and CBF reduction, suggesting a linkage.
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| 4. |
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| 5. |
- Arvidsson, Per M., et al.
(författare)
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Hemodynamic forces using four-dimensional flow MRI : An independent biomarker of cardiac function in heart failure with left ventricular dyssynchrony?
- 2018
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Ingår i: American Journal of Physiology - Heart and Circulatory Physiology. - : American Physiological Society. - 0363-6135 .- 1522-1539. ; 315:6, s. 1627-1639
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Tidskriftsartikel (refereegranskat)abstract
- Patients with heart failure with left ventricular (LV) dyssynchrony often do not respond to cardiac resynchronization therapy (CRT), indicating that the pathophysiology is insufficiently understood. Intracardiac hemodynamic forces computed from four-dimensional (4-D) flow MRI have been proposed as a new measure of cardiac function. We therefore aimed to investigate how hemodynamic forces are altered in LV dyssynchrony. Thirty-one patients with heart failure and LV dyssynchrony and 39 control subjects underwent cardiac MRI with the acquisition of 4-D flow. Hemodynamic forces were computed using Navier-Stokes equations and integrated over the manually delineated LV volume. The ratio between transverse (lateral-septal and inferior-anterior) and longitudinal (apical-basal) forces was calculated for systole and diastole separately and compared with QRS duration, aortic valve opening delay, global longitudinal strain, and ejection fraction (EF). Patients exhibited hemodynamic force patterns that were significantly altered compared with control subjects, including loss of longitudinal forces in diastole (force ratio, control subjects vs. patients: 0.32 vs. 0.90, P < 0.0001) and increased transverse force magnitudes. The systolic force ratio was correlated with global longitudinal strain and EF (P < 0.01). The diastolic force ratio separated patients from control subjects (area under the curve: 0.98, P < 0.0001) but was not correlated to other dyssynchrony measures (P > 0.05 for all). Hemodynamic forces by 4-D flow represent a new approach to the quantification of LV dyssynchrony. Diastolic force patterns separate healthy from diseased ventricles. Different force patterns in patients indicate the possible use of force analysis for risk stratification and CRT implantation guidance. NEW & NOTEWORTHY In this report, we demonstrate that patients with heart failure with left ventricular dyssynchrony exhibit significantly altered hemodynamic forces compared with normal. Force patterns in patients mechanistically reflect left ventricular dysfunction on the organ level, largely independent of traditional dyssynchrony measures. Force analysis may help clinical decision making and could potentially be used to improve therapy outcomes.
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| 6. |
- Arvidsson, Per M., et al.
(författare)
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Left and right ventricular hemodynamic forces in healthy volunteers and elite athletes assessed with 4D flow magnetic resonance imaging
- 2017
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Ingår i: American Journal of Physiology - Heart and Circulatory Physiology. - : American Physiological Society. - 0363-6135 .- 1522-1539. ; 312:2, s. 314-328
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Tidskriftsartikel (refereegranskat)abstract
- Intracardiac blood flow is driven by hemodynamic forces that are exchanged between the blood and myocardium. Previous studies have been limited to 2D measurements or investigated only left ventricular (LV) forces. Right ventricular (RV) forces and their mechanistic contribution to asymmetric redirection of flow in the RV have not been measured. We therefore aimed to quantify 3D hemodynamic forces in both ventricles in a cohort of healthy subjects, using magnetic resonance imaging 4D flow measurements. Twenty five controls, 14 elite endurance athletes, and 2 patients with LV dyssynchrony were included. 4D flow data were used as input for the Navier-Stokes equations to compute hemodynamic forces over the entire cardiac cycle. Hemodynamic forces were found in a qualitatively consistent pattern in all healthy subjects, with variations in amplitude. LV forces were mainly aligned along the apical-basal longitudinal axis, with an additional component aimed toward the aortic valve during systole. Conversely, RV forces were found in both longitudinal and short-axis planes, with a systolic force component driving a slingshot-like acceleration that explains the mechanism behind the redirection of blood flow toward the pulmonary valve. No differences were found between controls and athletes when indexing forces to ventricular volumes, indicating that cardiac force expenditures are tuned to accelerate blood similarly in small and large hearts. Patients’ forces differed from controls in both timing and amplitude. Normal cardiac pumping is associated with specific force patterns for both ventricles, and deviation from these forces may be a sensitive marker of ventricular dysfunction. Reference values are provided for future studies. New & Noteworthy Biventricular hemodynamic forces were quantified for the first time in healthy controls and elite athletes (n = 39). Hemodynamic forces constitute a slingshot-like mechanism in the right ventricle, redirecting blood flow toward the pulmonary circulation. Force patterns were similar between healthy subjects and athletes, indicating potential utility as a cardiac function biomarker.
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| 7. |
- Axelsson, Karl-Jonas, et al.
(författare)
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Adaptation of ventricular repolarization time following abrupt changes in heart rate: comparisons and reproducibility of repeated atrial and ventricular pacing.
- 2021
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Ingår i: American journal of physiology. Heart and circulatory physiology. - : American Physiological Society. - 1522-1539 .- 0363-6135. ; 320:1
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Tidskriftsartikel (refereegranskat)abstract
- Adequate adaptation of ventricular repolarization (VR) duration to changes in heart rate (HR) is important for cardiac electromechanical function and electrical stability. We studied the QT and QTpeak adaptation in response to abrupt start and stop of atrial and ventricular pacing on two occasions with an interval of at least 1 mo in 25 study subjects with permanent pacemakers. Frank vectorcardiography was used for data collection. Atrial or ventricular pacing was performed for 8min aiming at a cycle length (CL) of 500ms. We measured the immediate response (IR), the time constant (τ) of the exponential phase, and T90 End, the time to reach 90% change of QT and QTpeak from baseline to steady state during and after pacing. During atrial pacing, the CL decreased on average 45% from mean (SD) 944 (120) to 518 (46) ms and QT decreased on average 18% from 388 (20) to 318 (17) ms. For QT, T90 End was 103 (24) s and 126 (15) s after start versus stop of atrial pacing; a difference of 24 (27) s (P = 0.006). The response pattern was similar for τ but IR did not differ significantly between pacing start and stop. The response pattern was similar for QTpeak and also for QT and QTpeak following ventricular pacing start and stop. The coefficients of variation for repeated measures were 7%-21% for T90 End and τ. In conclusion, the adaptation of VR duration was significantly more rapid following increasing than decreasing HR and intraindividually a relatively reproducible process.NEW & NOTEWORTHY We studied the duration of ventricular repolarization (VR) adaptation and its hysteresis, following increasing and decreasing heart rate by abrupt start and stop of 8-min atrial or ventricular pacing in study subjects with permanent pacemakers and repeated the protocol with ≥1 mo interval, a novel approach. VR adaptation was significantly longer following decreasing than increasing heart rate corroborating previous observations. Furthermore, VR adaptation was intraindividually a reproducible and, hence, robust phenomenon, a novel finding.
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| 8. |
- Back, M, et al.
(författare)
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Leukotriene B4 is an indirectly acting vasoconstrictor in guinea pig aorta via an inducible type of BLT receptor
- 2004
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Ingår i: American journal of physiology. Heart and circulatory physiology. - : American Physiological Society. - 0363-6135 .- 1522-1539. ; 287:1, s. H419-H424
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Tidskriftsartikel (refereegranskat)abstract
- Leukotriene B4(LTB4) is a potent leukocyte chemoattractant recently implicated in the pathogenesis of atherosclerosis. The aim of this study was to assess the effects of LTB4on isolated aortic preparations. Rings of guinea pig aorta were challenged with LTB4for recording mechanical responses and measurements of mediator release, and LTB4receptor (BLT1) expression was assessed by RT-PCR. Single concentrations of LTB4induced concentration-dependent contractions that were inhibited by treatment with antihistamines, indomethacin, or the thromboxane receptor antagonist BAYu3405 as well as by denudation of endothelium. In addition, LTB4increased the release of histamine and thromboxane in the bath. The contractions induced by LTB4were inhibited by either the unselective BLT receptor antagonist ONO-4057 or the selective BLT1receptor antagonist U-75302. Pretreatment with all -trans-retinoic acid enhanced the contractions and the release of histamine induced by LTB4, without affecting either the contractions induced by histamine or the histamine release evoked by calcium ionophore A23187. Analysis by RT-PCR indicated the expression of a BLT1receptor in the guinea pig aorta and that BLT1receptor mRNA was upregulated after treatment with retinoic acid. These results suggest that LTB4contracts the guinea pig aorta via an indirect mechanism involving the release of histamine and thromboxane and that this BLT1receptor-mediated response can be upregulated by all -trans-retinoic acid.
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| 9. |
- Berger, D., et al.
(författare)
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Effect of PEEP, blood volume, and inspiratory hold maneuvers on venous return
- 2016
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Ingår i: American Journal of Physiology. Heart and Circulatory Physiology. - : American Physiological Society. - 0363-6135 .- 1522-1539. ; 311:3
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Tidskriftsartikel (refereegranskat)abstract
- According to Guyton’s model of circulation, mean systemic filling pressure (MSFP), right atrial pressure (RAP), and resistance to venous return (RVR) determine venous return. MSFP has been estimated from inspiratory hold-induced changes in RAP and blood flow. We studied the effect of positive end-expiratory pressure (PEEP) and blood volume on venous return and MSFP in pigs. MSFP was measured by balloon occlusion of the right atrium (MSFPRAO), and the MSFP obtained via extrapolation of pressure-flow relationships with airway occlusion (MSFPinsp_hold) was extrapolated from RAP/pulmonary artery flow (QPA) relationships during inspiratory holds at PEEP 5 and 10 cmH2O, after bleeding, and in hypervolemia. MSFPRAO increased with PEEP [PEEP 5, 12.9 (SD 2.5) mmHg; PEEP 10, 14.0 (SD 2.6) mmHg, P = 0.002] without change in QPA [2.75 (SD 0.43) vs. 2.56 (SD 0.45) l/min, P = 0.094]. MSFPRAO decreased after bleeding and increased in hypervolemia [10.8 (SD 2.2) and 16.4 (SD 3.0) mmHg, respectively, P < 0.001], with parallel changes in QPA. Neither PEEP nor volume state altered RVR (P = 0.489). MSFPinsp_hold overestimated MSFPRAO [16.5 (SD 5.8) vs. 13.6 (SD 3.2) mmHg, P = 0.001; mean difference 3.0 (SD 5.1) mmHg]. Inspiratory holds shifted the RAP/QPA relationship rightward in euvolemia because inferior vena cava flow (QIVC) recovered early after an inspiratory hold nadir. The QIVC nadir was lowest after bleeding [36% (SD 24%) of preinspiratory hold at 15 cmH2O inspiratory pressure], and the QIVC recovery was most complete at the lowest inspiratory pressures independent of volume state [range from 80% (SD 7%) after bleeding to 103% (SD 8%) at PEEP 10 cmH2O of QIVC before inspiratory hold]. The QIVC recovery thus defends venous return, possibly via hepatosplanchnic vascular waterfall. © 2016 the American Physiological Society.
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