Hedde van de Vooren

Validation of ECG Indices of Ventricular Repolarization Heterogeneity: A Computer Simulation Study

Introduction: Repolarization heterogeneity (RH) is functionally linked to dispersion in refractoriness and to arrhythmogenicity. In the current study, we validate several proposed electrocardiogram (ECG) indices for RH: T‐wave amplitude, ‐area, ‐complexity, and ‐symmetry ratio, QT dispersion, and the Tapex‐end interval (the latter being an index of transmural dispersion of the repolarization (TDR)).

Exercise training increases oxygen uptake efficiency slope in chronic heart failure.

Background and aim The oxygen uptake efficiency slope (OUES) is a novel measure of cardiopulmonary reserve. OUES is measured during an exercise test, but it is independent of the maximally achieved exercise intensity. It has a higher prognostic value in chronic heart failure (CHF) than other exercise test-derived variables such as V . O 2 peak or V . E / V . CO 2 slope. Exercise training improves V . O 2 peak and V . E / V . CO 2 in CHF patients. We hypothesized that exercise training also improves OUES. Methods and results We studied 34 New York Heart Association (NYHA) class II–III CHF patients who constituted an exercise training group T (N = 20; 19 men/1 woman; age 60 ± 9 years; left ventricular ejection fraction 34 ± 5%) and a control group C (N = 14; 13 men/one woman; age 63 ± 10 years; left ventricular ejection fraction 34 ± 7%). A symptom-limited exercise test was performed at baseline and repeated after 4 weeks (C) or after completion of the training program (T). Exercise training increased NYHA class from 2.6 to 2.0 (P [ 0.05), V . O 2 peak by 14% [P(TvsC)[0.01], and OUES by 19% [P(TvsC) [ 0.01]. Exercise training decreased V . E / V . CO 2 by 14% [P(TvsC) [ 0.05]. Conclusion Exercise training improved NYHA class, V . O 2 peak , V . E / V . CO 2 and also OUES. This finding is of great potential interest as OUES is insensitive for peak load. Follow-up studies are needed to demonstrate whether OUES improvements induced by exercise training are associated with improved prognosis.

Rehabilitation: Periodic somatosensory stimulation increases arterial baroreflex sensitivity in chronic heart failure patients

BACKGROUND One of the beneficial effects of exercise training in chronic heart failure (CHF) is an improvement in baroreflex sensitivity (BRS), a prognostic index in CHF. In our hypothesis-generating study we propose that at least part of this effect is mediated by neural afferent information, and more specifically, by exercise-induced somatosensory nerve traffic. OBJECTIVE To compare the effects of periodic electrical somatosensory stimulation on BRS in patients with CHF with the effects of exercise training and with usual care. METHODS We compared in stable CHF patients the effect of transcutaneous electrical nerve stimulation (TENS, N = 23, LVEF 30 ± 9%) with the effects of bicycle exercise training (EXTR, N = 20, LVEF 32 ± 7%). To mimic exercise-associated somatosensory ergoreceptor stimulation, we applied periodic (2/s, marching pace) burst TENS to both feet. TENS and EXTR sessions were held during two successive days. RESULTS BRS, measured prior to the first intervention session and one day after the second intervention session, increased by 28% from 3.07 ± 2.06 to 4.24 ± 2.61 ms/mmHg in the TENS group, but did not change in the EXTR group (baseline: 3.37 ± 2.53 ms/mmHg; effect: 3.26 ± 2.54 ms/mmHg) (P(TENS vs EXTR) = 0.02). Heart rate and systolic blood pressure did not change in either group. CONCLUSIONS We demonstrated that periodic somatosensory input alone is sufficient and efficient in increasing BRS in CHF patients. This concept constitutes a basis for studies towards more effective exercise training regimens in the diseased/impaired, in whom training aimed at BRS improvement should possibly focus more on the somatosensory aspect.

Hypertensive Stress Increases Dispersion of Repolarization

Several electrocardiographic indices for repolarization heterogeneity have been proposed previously. The behavior of these indices under two different stressors at the same heart rate (i.e., normotensive gravitational stress, and hypertensive isometric stress) was studied. ECG and blood pressure were recorded in 56 healthy men during rest (sitting with horizontal legs), hypertensive stress (performing handgrip), and normotensive stress (sitting with lowered legs). During both stressors, heart rates differed <10% in 41 subjects, who constituted the final study group. Heart rate increased from 63 ± 9 beats/min at rest to 71 ± 11 beats/min during normotensive, and to 71 ± 10 beats/min during hypertensive stress (P < 0.001). Systolic blood pressure was 122 ± 15 mmHg at rest and 121 ± 15 mmHg during normotensive stress, and increased to 151 ± 17 mmHg during hypertensive stress (P < 0.001). The QT interval was larger during hypertensive (405 ± 27) than during normotensive stress (389 ± 26, P < 0.001). QT dispersion did not differ significantly between the two stressors. The mean interval between the apex and the end of the T wave (Tapex‐Tend) of the mid‐precordial leads was larger during hypertensive (121 ± 17 ms) than during normotensive stress (116 ± 15 ms, P < 0.001). The singular value decomposition T wave index was larger during hypertensive (0.144 ± 0.071) than during normotensive stress (0.089 ± 0.053, P < 0.001). Most indices of repolarization heterogeneity were larger during hypertensive stress than during normotensive stress. Hypertensive stressors are associated with arrhythmogeneity in vulnerable hearts. This may in part be explained by the induction of repolarization heterogeneity by hypertensive stress.

Exercise-resembling effects of periodic somatosensory stimulation in heart failure ☆

BACKGROUND The mechanism of the beneficial effects of exercise training on autonomic derangement and neurohumoral activation in chronic heart failure (CHF) is largely unexplained. In our here-presented hypothesis-generating study we propose that part of these effects is mediated by the exercise-accompanying somatosensory nerve traffic. To demonstrate this, we compared the effects of periodic electrical somatosensory stimulation in patients with CHF with the effects of exercise training and with usual care. METHODS In a randomized controlled study we measured, in CHF patients, changes in blood pressure, baroreflex sensitivity (BRS), neurohormones, exercise capacity and quality of life (QOL) in response to periodic somatosensory stimulation in the form of 2 Hz transcutaneous electrical nerve stimulation (TENS) at both feet, in response to conventional exercise training (EXTR) and, as control (CTRL), in patients with usual care only. RESULTS Group sizes were N=31 (TENS group), N=25 (EXTR group) and N=30 (CTRL group), respectively. Practically all improvements in BRS, neurohormone concentrations, exercise capacity and QOL in the TENS group were comparable to, or sometimes even better than in the EXTR group. These improvements were not observed in the CTRL group. CONCLUSIONS This study demonstrates that periodic electrical somatosensory stimulation is as effective as exercise training in improving BRS, neurohormone concentrations, exercise capacity and QOL in CHF patients. These results encourage exploration of exercise modalities that concentrate on rhythm rather than on effort, with the purpose to normalize autonomic derangement and neurohumoral activation in CHF.