Jaana J. Karjalainen

Physical activity and heart rate variability measured simultaneously during waking hours

Heart rate (HR) variability (HRV) during ambulatory recordings may be affected by individual differences in daily physical activity (PA). However, the influence of various levels of PA on different measures of HRV is not exactly known. We examined the association between simultaneously measured HRV and objective PA data obtained with an accelerometer during waking hours among 45 healthy adults. Bouts of PA were identified from minute-by-minute accelerometer data as metabolic equivalent (METs) values and calculated as mean METs for 30 min. HRV was analyzed concurrently. Within-individual correlation analyses and sign tests were performed to study the relationships between various HRV indexes and PA. The mean PA time was 15:44 +/- 1:01 h, and the mean MET was 1.91 +/- 0.14. HR and sample entropy, but not the other measures of HRV, had a significant relationship with PA, as shown by both correlation analyses (r = 0.64, P = 0.021, and r = -0.55, P = 0.022, respectively) and sign tests (P < 0.0001 for both). Beat-to-beat R-R interval fluctuation expressed as SD1 also demonstrated a significant relation to PA according to the sign test (P = 0.037) and a trend of association according to the correlation analysis (r = -0.40, P = 0.129). The complexity measure of HRV, in addition to average HR and the short-term index of HRV (SD1), is significantly influenced by the level of PA during ambulatory conditions. Long-term HRV indexes remained relatively stable at various activity levels, making them the most robust indexes for the assessment of cardiac autonomic function during free-running ambulatory conditions.

Effects of exercise prescription on daily physical activity and maximal exercise capacity in coronary artery disease patients with and without type 2 diabetes

Promotion of and adherence to increased physical activity (PA) is an important part of the prevention and treatment of coronary artery disease (CAD). We hypothesized that individually tailored home‐based exercise prescriptions will increase long‐term PA and maximal exercise capacity among CAD patients without and with type 2 diabetes (CAD+T2D).

Effects of Physical Activity and Exercise Training on Cardiovascular Risk in Coronary Artery Disease Patients With and Without Type 2 Diabetes

OBJECTIVE Leisure-time physical activity (LTPA) and exercise training are essential parts of current guidelines for patients with coronary artery disease (CAD). However, the contributions of LTPA and exercise training to cardiovascular (CV) risk in CAD patients with type 2 diabetes (T2D) are not well established. RESEARCH DESIGN AND METHODS We examined the effects of LTPA (n = 539 and n = 507; with and without T2D, respectively) and 2-year controlled, home-based exercise training (n = 63 plus 64 control subjects with T2D and n = 72 plus 68 control subjects without T2D) on the CV risk profile and composite end point among CAD patients. RESULTS During the 2-year follow-up, patients with reduced LTPA at baseline had an increased risk of CV events (adjusted hazard ratio 2.3 [95% CI 1.1–5.1; P = 0.033], 2.1 [1.1–4.2; P = 0.027], and 2.0 [1.0–3.9; P = 0.044] for no LTPA, LTPA irregularly, and LTPA two to three times weekly, respectively) compared with those with LTPA more than three times weekly. Among patients who completed the 2-year exercise intervention, exercise training resulted in favorable changes in exercise capacity both in CAD patients with T2D (+0.2 ± 0.8 vs. −0.1 ± 0.8 MET, P = 0.030) and without T2D (+0.3 ± 0.7 vs. −0.1 ± 0.5 MET, P = 0.002) as compared with the control group but did not have any significant effects on major metabolic or autonomic nervous system risk factors in CAD patients with or without T2D. CONCLUSIONS There is an inverse association between habitual LTPA and short-term CV outcome, but controlled, home-based exercise training has only minor effects on the CV risk profile in CAD patients with T2D.

Heart rate dynamics after exercise in cardiac patients with and without type 2 diabetes

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.

Impact of type 2 diabetes on cardiac autonomic responses to sympathetic stimuli in patients with coronary artery disease

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±6 years, 14 women) and without T2D (T2D-, n=68, 62±6 years, 17 women). The effect of T2D at rest and in responses to TILT and HG was examined. In T2D+, the normalized low-frequency (0.04-0.15 Hz) power of R-R intervals was higher at rest (44±17 vs. 38±17 nu, p=0.015) and its response to TILT and HG was lower than that in T2D- (8±21 vs. 2±17 nu, p=0.041 and 3±18 vs. -4±15 nu, 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.

Determinants of heart rate recovery in coronary artery disease patients with and without type 2 diabetes

Cardiovascular autonomic dysfunction, which is a common complication of diabetes, is associated with increased mortality in patients with coronary artery disease (CAD). However, the reasons of autonomic dysfunction in CAD patients with or without diabetes are not well known. We examine the association between heart rate recovery (HRR) and other potential factors among CAD patients with and without type 2 diabetes (T2D). Correlations between HRR 60s after exercise (HRR(60)), characteristics, laboratory and echocardiographic variables, exercise capacity and physical activity were assessed in 50 CAD patients with T2D and 55 patients with CAD alone. HRR(60) had the closest univariate correlation with physical activity and exercise capacity in patients with T2D (r=0.38, p=0.006 and r=0.37, p=0.008, respectively). Age, exercise capacity and high-density lipoprotein cholesterol level explained 30% of the HRR(60) in patients with T2D (p=0.001), while the high intensity physical activity was the only predictor of HRR(60) in CAD patients (12%, p=0.010). HRR(60) was reduced in patients with T2D as compared with those without (34±9 vs. 39±9bpm, p=0.005), but the difference was no longer significant after adjustments for physical activity, exercise capacity, body mass index and the use of calcium antagonists and nitrates (p=0.273). In conclusion, blunted HRR is more common among CAD patients with T2D than in those without, and this is more closely related to physical activity and obesity than to the duration of T2D or associated co-morbidities.

Peak exercise capacity prediction from a submaximal exercise test in coronary artery disease patients

The purpose of this study was to determine whether a rating of perceived exertion scale (RPE) obtained during submaximal exercise could be used to predict peak exercise capacity (METpeak) in coronary artery disease (CAD) patients. Angiographically documented CAD patients (n = 124, 87% on β blockade) completed a symptom-limited peak exercise test on a bicycle ergometer, reporting RPE values at every second load on a scale of 6–20. Regression analysis was used to develop equations for predicting METpeak. We found that submaximal METs at a workload of 60/75 W (for women and men, respectively) and the corresponding RPE (METs/RPE ratio) was the most powerful predictor of METpeak (r = 0.67, p < 0.0001). The final model included the submaximal METs/RPE ratio, body mass index (BMI), sex, resting heart rate, smoking history, age, and use of a β blockade (r = 0.86, p < 0.0001, SEE 0.98 METs). These data suggest that RPE at submaximal exercise intensity is related to METpeak in CAD patients. The model based on easily measured variables at rest and during “warm-up” exercise can reasonably predict absolute METpeak in patients with CAD.

EFFECTS OF CONTROLLED EXERCISE REHABILITATION ON QRS/T ANGLE IN CAD PATIENTS WITH AND WITHOUT DIABETES

methods: Diabetic (n=20) and non-diabetic patients (n=22) with angiographically proven CAD were selected from ARTEMIS exercise study, a twoyear randomized and controlled exercise trial. Patients were matched on age, sex, prior myocardial infarction and revascularization. Holter recordings (24h) were performed before and after 12-month training. Linear regression was used to calculate a predicted QRSTA at 60bpm.