Exercise training and heart rate variability in older people.

PURPOSE: Heart rate variability (HRV), a characteristic that is potentially increased by physical activity, has been associated with incidence of cardiac events and total mortality. Since the incidence of cardiac events among older people is high and their physical activity levels and HRV are generally low, it is important to investigate whether regular physical activity can modify HRV in this age group. The purpose of the study was to investigate the effect of regular physical activity on HRV in older men and women. METHODS: In a randomized controlled trial, the effect of six months' training on HRV was investigated in a group of 51 older men and women (67.0 +/- 5.1 yr). The training group gathered three times per week for 45 min supervised training. RESULTS: At the end of the intervention period, HRV was higher primarily during the day. During daytime, the SD of all normal intervals (+6%) as well as the low frequency component (+ 15%) and the very low frequency component (+ 10%) of HRV were significantly increased (P < 0.05) as compared with the control group. Effects of training were most pronounced in subjects inactive in sports at baseline. CONCLUSION: This study demonstrates that regular physical activity increases HRV (specifically in the very low and low frequency components) in older subjects. Hence, in older subjects, physical training may be an effective means to modify positively a factor that is associated with increased incidence of cardiac events.

On the clinical value of conventional and new exercise electrocardiographic criteria: a comparative study.

We have evaluated the clinical value of new electrocardiographic criteria in exercise testing. In this study, we compared both ST-segment and R-wave amplitude criteria, separately and in combination with the findings from coronary arteriography in 122 patients. In these selected patients application of conventional ST-segment criteria gave a sensitivity of 31% and a specificity of 100%; with application of the slow upsloping ST-segment criteria the sensitivity was 51% and the specificity 82%. Analysis of R-wave amplitude changes alone led to a sensitivity of 50% and a specificity of 61%. In combined interpretation of ST-segment and R-wave amplitude changes the sensitivity was 51% and the specificity 93%. We conclude that slow upsloping ST-segment criteria constitute the most important recent improvement in interpreting exercise test results and that the value of R-wave amplitude changes during exercise in diagnosing significant coronary artery disease is rather low in the individual patient. R-wave amplitude changes, however, may have value in patients with a previous myocardial infarction and in reducing false-negative and false-positive responses according to ST-segment criteria. Combined interpretation of ST-segment and R-wave amplitude criteria is useful but not very efficient.

Clinical significance of upsloping ST segments in exercise electrocardiography.

Conventional exercise electrocardiographic criteria usually involve patterns with a horizontal or downsloping ST segment. In the present study we present criteria based on upsloping ST segments and compared these criteria with the conventional criteria. Using upsloping ST-segment criteria, the amount of ST-segment depression at 80 msec after the end of the QRS complex is used as a parameter (ST criterion E, with a depression of 100 mV, and ST criterion F, with a depression of 200 mV). In the graded exercise test a bicycle ergometer was used. The ECG leads were CM5 and CC5. The results of exercise electrocardiography were compared with the findings from coronary arteriography. In 623 selected patients (565 males and 58 females), application of conventional ST criteria gave a sensitivity of 56% and a specificity of 94%; with application of the ST criteria E or F, sensitivity was 75% and specificity 90%. In the 58 females use of these new criteria resulted in a sensitivity of 76% and specificity of 88%. Ninety-three patients (15%) could be classified as positive exercise responders by the sole presence of an upsloping ST segment (type E or F). Sixty-eight percent of the patients with type E and 75% with type F had two- or three-vessel disease (coronary obstructions greater their or equal to 50%). We conclude that ST criteria based on upsloping ST segments significantly increase the diagnostic yield of the exercise ECG.

Effect of physical training on QTc interval in elderly people.

In order to assess whether heart rate-adjusted QT duration (QTc) is reduced by physical activity in an elderly population, a randomized, controlled intervention study of the effect of a 6-month intensive training program on QTc was undertaken. The participants were 229 healthy men and women, aged 60-80 years. The subjects of the intervention group trained three to four times a week at a work load of about 70% of their maximum capacity for 6 months, while the control subjects maintained their habitual activities. The main outcome measures were change in QTc and resting heart rate. For women, the mean QTc interval (ms) of the intervention group changed by -6.7 (SE 2.8) versus 0.6 (SE 2.4) in the control group (P = .05), while for men, the change in the intervention group subjects was -2.7 (SE 2.2) versus 0.4 (SE 3.1) in the control subjects (P = .39). Also, resting heart rate (beats/ min) changed in intervention group women by -4.6 (SE 1.7) as against -0.06 (SE 1.1) in the control subjects (P = .02), and in intervention group men it changed by -3.2 (SE 1.2) versus -0.9 (SE 1.5) in the control subjects (P = .25). These data indicate that regular physical activity favorably affects QTc in elderly women. A similar, but not significant, trend was observed in men. The beneficial shift in QTc may be caused by a more favorable autonomic balance through increased parasympathetic activity. The reduced resting heart rate in subjects of the intervention group supports this view. Although the reduction was relatively small, it may represent a favorable effect on cardiovascular risk.