| 1. |
- Björkander, I., et al.
(författare)
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Differential index, a novel graphical method for measurements of heart rate variability
- 2005
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Ingår i: International Journal of Cardiology. - : Elsevier BV. - 0167-5273 .- 1874-1754. ; 98:3, s. 493-499
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Tidskriftsartikel (refereegranskat)abstract
- Background: Commonly used methods to evaluate heart rate variability require extensive filtering of the registrations in order to exclude artefacts and ectopic beats. We developed and validated a novel graphical method for time-domain measurements of heart rate variability, the differential index, which does not require filtering and is simple to use. Methods: The 24-h ambulatory long-term electrocardiogram recordings from 120 patients with angina pectoris and 49 control subjects were computerised without any filtering process. Sample density histograms of differences in the RR interval for successive beats were constructed and the widths of the histograms were used to obtain the differential index. For comparison, the same registrations were analysed by conventional methods. Results: The differential index was most closely related (P < 0.001) to conventional short-term time domain (e.g. percent of differences between adjacent normal RR intervals > 50 ms, pNN50, r = 0.81) and frequency-domain (e.g. high frequency power, r = 0.84) components, but also to long-term time domain (e.g. standard deviation of all normal-to-normal RR intervals for all 5-min segments of the entire registration, SDNNIDX, r = 0.72) and frequency-domain (e.g. low frequency power, r = 0.64) components. Conclusion: The differential index method shows good agreement with established indices of heart rate variability. The insensitivity to recording artefacts and short-lasting disturbances of sinus rhythm make the differential index method particularly suited when data quality is imperfect. The simplicity of the method is valuable when large numbers of registrations are to be evaluated.
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| 2. |
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| 3. |
- Govind, Satish C., et al.
(författare)
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Microalbuminuria and Left Ventricular Functions in Type 2 Diabetes : A Quantitative Assessment by Stress Echocardiography in the Myocardial Doppler in Diabetes (MYDID) Study III
- 2007
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Ingår i: International Journal of Cardiology. - : Informa UK Limited. - 0167-5273 .- 1874-1754. ; 41:6, s. 363-369
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Tidskriftsartikel (refereegranskat)abstract
- Background. Left ventricular (LV) function might be altered in type 2 diabetes (DM) and microalbuminuria (MA) may accentuate the abnormalities. We sought to investigate whether additional LV dysfunction could be unmasked using tissue Doppler (TVE)-enhanced dobutamine stress echocardiography (TVE-DSE) in patients with DM+MA. Methods. Twenty seven DM subjects with MA, (DM+MA), 31 DM subjects without MA (DM-MA), and 13 Controls were evaluated using TVE-DSE. LV basal peak systolic (PSV), early (E') and late (A') diastolic velocities (cm/sec) at rest and peak stress were post-processed. LV filling pressure was assessed using E/E'ratio. Results. PSV and E'velocity at peak stress in the respective three groups were 13.7±1.0, 10.1±1.1, 10.0±1.2 for PSV; and 10.0±1.6, 5.0±1.4, 4.8±1.4 for E' (p < 0.001 for controls vs. both groups). E/E' at rest was 7.9±0.7 in the controls, 10.8±2.4 in DM-MA, and 11.0±2.2 in DM+MA (p < 0.01 Controls vs. both the DM groups). Conclusions. Patients with DM+MA do not have additional LV regional systolic and diastolic dysfunctions compared with DM-MA, as revealed by TVE-DSE, when controlled for glycemia levels, lipids, and treatment strategies.
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| 4. |
- Holzapfel, Gerhard A., et al.
(författare)
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Computational stress-deformation analysis of arterial walls including high-pressure response
- 2007
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Ingår i: International Journal of Cardiology. - : Elsevier BV. - 0167-5273 .- 1874-1754. ; 116:1, s. 78-85
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Tidskriftsartikel (refereegranskat)abstract
- Background: Changes in the mechanical behavior of arteries after balloon angioplasty cause cell reactions that may be responsible for restenosis. Hence, the study of the stress-deforination changes in arterial walls following supraphysiological tissue loading is an essential task. Methods: A normal LAD coronary artery was modeled and computationally analyzed as a two-layer, thick-walled, anisotropic and inelastic circular tube including residual strains. Each layer was treated as a fibre-matrix composite. The tube was subjected to an axial stretch of 1. 1 and a transmural pressure of 750 min Hg. Since overstretch of rerrmant non-diseased tissue in lesions is a primary mechanism of lumen enlargement this model approach represents a reasonable first step. Results: At physiological loading, the residual stresses led to a significant reduction of the high circumferential stress values at the inner wall, and the stress gradients. At low pressure level the media was the mechanically relevant layer, while at supraphysiological loading, the adventitia was the predominant load-carrying constituent providing a stiff support for 'redistribution' of soft plaque components by means of radial compression. After unloading to physiological loading conditions the stress state in the arterial wall differed significantly from that before inflation; the stress gradient in the media even changed its sign. Complete unloading indicated lumen enlargement, material softening and energy dissipation, which is in agreement with experimental studies. Conclusions: This method may be useful to improve interventional protocols for reducing the dilatational trauma, and thereby the adverse biological reaction in arterial walls following balloon angioplasty.
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| 5. |
- Kronander, Håkan, et al.
(författare)
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Analysis of ST/HR hysteresis improves long-term prognostic value of exercise ECG test.
- 2011
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Ingår i: International Journal of Cardiology. - : Elsevier BV. - 0167-5273 .- 1874-1754. ; 148:1, s. 64-9
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: ST/HR hysteresis is one of the better diagnostic exercise ECG variables for coronary artery disease. This study evaluates the long-term prognostic value of ST/HR hysteresis in predicting acute myocardial infarction (AMI) and all-cause mortality in men and women. METHODS: The study population consisted of 8317 patients who had undergone routine exercise test on bicycle ergometer at one Swedish centre. Information on AMI and all-cause mortality was obtained from national Swedish registers covering a mean follow-up period of 9.5 years. RESULTS: The adjusted hazard ratio for AMI at a diagnostic cut point of ≤-20 µV for ST/HR hysteresis was 1.88 (95% CI, 1.62-2.17) in men and 2.31 (95% CI, 1.83-2.91) in women. For all-cause death the adjusted hazard ratio was 1.72 (95% CI, 1.52-1.96) in men and 1.90 (95% CI, 1.57-2.29) in women. The corresponding hazard ratios for ST-segment depression with horizontal or down-sloping ST-segment, ST-segment depression, ST/HR index, and ST/HR slope were lower. For comparison, the adjusted hazard ratio for AMI using maximal workload in percent of predicted was 2.02 (95% CI, 1.77-2.32) in men and 2.14 (95% CI, 1.71-2.67) in women. Area under the ROC curves for prediction of AMI was significantly larger using ST/HR hysteresis than using any of three other evaluated ECG indicators. CONCLUSIONS: ST/HR hysteresis appears to improve the prognostic ability of an exercise ECG test for AMI and all-cause mortality in a long-term perspective compared to conventional ST-segment and ST/HR indicators in both genders and clearly more markedly in women.
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| 6. |
- Manouras, Aristomenis, et al.
(författare)
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The value of E/E(m) ratio in the estimation of left ventricular filling pressures : Impact of acute load reduction A comparative simultaneous echocardiographic and catheterization study
- 2013
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Ingår i: International Journal of Cardiology. - : Elsevier BV. - 0167-5273 .- 1874-1754. ; 166:3, s. 589-595
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The ratio of the early transmitral flow velocity to the early diastolic tissue velocity (E/E(m)) has been suggested as a reliable estimate of left ventricular diastolic pressures (LVDP). However, the evidence regarding the ability of E/E(m) to detect LVDP changes is relatively equivocal. Our aim was to evaluate the validity of the ratio following acute load reduction. METHODS AND RESULTS: 68 consecutive patients referred for coronary angiography underwent LV catheterization and echocardiography simultaneously. Doppler signals of transmitral flow and spectral TD signals at the level of the mitral annulus were obtained before and directly after intravenous administration of nitroglycerin (NTG). The predictive ability of E/E(m) to identify elevated LVDP was modest (area under curve=0.71±0.08, p<0.01). The index was more strongly associated with LVDP in patients with reduced ejection fraction (EF)<55% (r=0.68; p<0.01) than in patients with normal EF. Following NTG, E/E(m) lacked any predictive potential for elevated LVDP whereas changes LVDP could not be reliably tracked using E/E(m). CONCLUSION: The predictive capacity of E/E(m) for elevated LVDP was weak and declined significantly following acute reduction in LV load. Changes in LVDP were not reliably predicted by E/E(m). The current findings derived from a real-world patient population with relatively high filling pressures indicate that E/E(m) may not be sufficiently robust to be employed as a single non-invasive estimate of LVDP nor for monitoring load reducing medical therapy.
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