Heart Rate Dynamics after Exercise in Cardiac Patients with and without Type 2 Diabetes
ABSTRACT Purpose: The incidence of cardiovascular events is higher in coronary artery disease patients with type 2 diabetes (CAD + T2D) than in CAD patients without T2D. There is increasing evidence that the recovery phase after exercise is a vulnerable phase for various cardiovascular events. We hypothesized that autonomic regulation differs in CAD patients with and without T2D during post-exercise condition. Methods: A symptom-limited maximal exercise test on a bicycle ergometer was performed for 68 CAD + T2D patients (age 61 ± 5 years, 78% males, ejection fraction (EF) 67 ± 8, 100% on β-blockade), and 64 CAD patients (age 62 ± 5 years, 80% males, EF 64 ± 8, 100% on β-blockade). Heart rate (HR) recovery after exercise was calculated as the slope of HR during the first 60 s after cessation of exercise (HRRslope). R–R intervals were measured before (5 min) and after exercise from 3 to 8 min, both in a supine position. R–R intervals were analyzed using time and frequency methods and a detrended fluctuation method (α1). Results: BMI was 30 ± 4 vs. 27 ± 3 kg m2 (p < 0.001); maximal exercise capacity, 6.5 ± 1.7 vs. 7.7 ± 1.9 METs (p < 0.001); maximal HR, 128 ± 19 vs. 132 ± 18 bpm (p = ns); and HRRslope, −0.53 ± 0.17 vs. −0.62 ± 0.15 beats/s (p = 0.004), for CAD patients with and without T2D, respectively. There was no differences between the groups in HRRslope after adjustment for METs, BMI, and medication (ANCOVA, p = 0.228 for T2D and, e.g., p = 0.030 for METs). CAD + T2D patients had a higher HR at rest than non-diabetic patients (57 ± 10 vs. 54 ± 6 bpm, p = 0.030), but no other differences were observed in HR dynamics at rest or in post-exercise condition. Conclusion: HR recovery is delayed in CAD + T2D patients, suggesting impairment of vagal activity and/or augmented sympathetic activity after exercise. Blunted HR recovery after exercise in diabetic patients compared with non-diabetic patients is more closely related to low exercise capacity and obesity than to T2D itself.
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ABSTRACT: Cardiovascular risk can be calculated using the Framingham cardiovascular disease (CVD) risk score and provides a risk stratification from mild to very high CVD risk percentage over 10 years. This equation represents a complex interaction between age, gender, cholesterol status, blood pressure, diabetes status, and smoking. Heart rate variability (HRV) is a measure of how the autonomic nervous system (ANS) modulates the heart rate. HRV measures are sensitive to age, gender, disease status such as diabetes and hypertension and processes leading to atherosclerosis. We investigated whether HRV measures are a suitable, simple, noninvasive alternative to differentiate between the four main Framingham associated CVD risk categories. In this study we applied the tone-entropy (T-E) algorithm and complex correlation measure (CCM) for analysis of HRV obtained from 20 min. ECG recordings and correlated the HRV score with the stratification results using the Framingham risk equation. Both entropy and CCM had significant analysis of variance (ANOVA) results [F (172, 3) = 9.51; <0.0001]. Bonferroni post hoc analysis indicated a significant difference between mild, high and very high cardiac risk groups applying tone-entropy (p < 0.01). CCM detected a difference in temporal dynamics of the RR intervals between the mild and very high CVD risk groups (p < 0.01). Our results indicate a good agreement between the T-E and CCM algorithm and the Framingham CVD risk score, suggesting that this algorithm may be of use for initial screening of cardiovascular risk as it is noninvasive, economical and easy to use in clinical practice.Frontiers in Physiology 01/2013; 4:186. DOI:10.3389/fphys.2013.00186
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ABSTRACT: BACKGROUND:: Heart rate recovery (HRR) after exercise cessation is thought to reflect the rate of reestablishment of parasympathetic tone. Relatively little research has focused on improved HRR in women after completing cardiac rehabilitation (CR) exercise training. OBJECTIVE:: We examined the influence of exercise training on HRR in women completing a traditional CR program and in women completing a CR program tailored for women. METHODS:: A 2-group randomized clinical trial compared HRR between 99 women completing a traditional 12-week CR program and 137 women completing a tailored CR program. Immediately upon completion of a symptom-limited graded exercise test, HRR was measured at 1 through 6 minutes. RESULTS:: Compared with baseline, improvement in 1-minute HRR (HRR1) was similar (P = 0.777) between the tailored (mean [SD], 17.5  to 19.1 ) and the traditional CR program (15.7 [9.0] to 16.9 [9.5]). The amount of change in the 2-minute HRR (HRR2) for the tailored (30  to 32.8 [14.6]) and traditional programs (28.3 [12.8] to 31.2 [13.7]) also was not different (P = 0.391). Similar results were observed for HRR at 3 through 6 minutes. Given these comparable improvements of the 2 programs, in the full cohort, the factors independently predictive of post-CR HRR1, in rank order, were baseline HRR1 (part correlation, 0.35; P < 0.001); peak exercise capacity, estimated as metabolic equivalents (METs; 0.24, P < 0.001); anxiety (-0.17, P = 0.001); and age (-0.13, P = 0.016). The factors independently associated with post-CR HRR2 were baseline HRR2 (0.44, P < 0.001), peak METs (0.21, P < 0.001), and insulin use (-0.10, P = 0.041). CONCLUSIONS:: One to 6 minutes after exercise cessation, HRR was significantly improved among the women completing both CR programs. The modifiable factors positively associated with HRR1 included peak METs and lower anxiety, whereas HRR2 was associated with insulin administration and peak METs. Additional research on HRR after exercise training in women is warranted.The Journal of cardiovascular nursing 11/2012; DOI:10.1097/JCN.0b013e31827324e2 · 1.81 Impact Factor
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ABSTRACT: Type 2 diabetes (T2D) has shown limited impact on cardiac autonomic function in patients with cardiac disease at rest. The effect of T2D on autonomic responses to sympathetic stimuli, such as passive tilt and static exercise, is not well known in patients with coronary artery disease (CAD). Heart rate, arterial pressure, and their variability along with baroreflex sensitivity (BRS) were analyzed at supine rest and during passive head-up tilt (TILT) and static handgrip exercise (HG) in CAD patients with (T2D+, n=68, 61±6years, 14 women) and without T2D (T2D-, n=68, 62±6years, 17 women). The effect of T2D at rest and in responses to TILT and HG was examined. In T2D+, the normalized low-frequency (0.04-0.15Hz) power of R-R intervals was higher at rest (44±17 vs. 38±17nu, p=0.015) and its response to TILT and HG was lower than that in T2D- (8±21 vs. 2±17nu, p=0.041 and 3±18 vs. -4±15nu, p=0.019, respectively). Vagally mediated heart rate variability indices and BRS were not different between T2D+ and T2D-. We concluded that T2D has a specific impact on low-frequency oscillation of R-R interval among patients with angiographically documented CAD. This may indicate increased basal sympathetic modulation of sinoatrial node and lower sympathetic responsiveness to sympathetic activation by baroreceptor unloading and exercise pressor response. Limited effects of T2D on vagally mediated heart rate variability and baroreflex were observed in the patients with CAD.Autonomic neuroscience: basic & clinical 08/2013; 179(1-2). DOI:10.1016/j.autneu.2013.08.068 · 1.37 Impact Factor