Author + information
- David A Kassa
Bertella et al. have highlighted the importance of abnormal diastolic properties in the elderly, as well as the potential value of lowering heart rate to prolong filling time. They suggest that this mechanism likely played a more important role in the improved aerobic exercise capacity observed after acute intravenous verapamil administration in healthy elderly individuals than we had credited. Although we agree that increasing diastolic filling time would likely be helpful, this mechanism did not appear to play an important role in our study.
First, verapamil did not slow rest heart rate (p = 0.14), did not significantly alter heart rate at 25-W work loads (96.8 ± 14.1 vs. 92.6 ± 19.0 beats/min at 25 W, p = 0.256) and only modestly slowed heart rate at maximal exercise levels (mean ± SD 134.1 ± 25.8 vs. 126.8 ± 21.1 beats/min, p = 0.018). The heart rate values reported in Table 2 were the mean values ± SEM, and perhaps this confusion led to the incorrect p value calculations determined by Bertella et al. Second, of the 19 study patients, verapamil slowed heart rate at maximal exercise in 12 but raised it in the others. However, none of the exercise performance variables were significantly different between these two subgroups. For example, V̇o2 at the anaerobic threshold was 13.7 ± 21% in patients with a slowed heart rate as compared with 12.3 ± 20% in the others (p = 0.887), and total exercise time also increased similarly by 6.1% and 5.5%, respectively (p = 0.926). Lastly, the effects of improved diastolic filling should have been reflected, in part, in the early peak filling rate normalized to preload (PFREDV). Yet, as we reported, PFREDV did not significantly change with verapamil, and none of the exercise performance variables significantly differed between the subgroups with increased versus decreased PFREDV after the administration of verapamil.
Recent evidence (1) suggests that the elderly may not have the marked deficiencies of diastolic suction or early elastic recoil that Bertella et al. propose. These studies have utilized tagged magnetic resonance imaging to quantify early diastolic untwisting, a behavior generally accepted to reflect recoil properties. Rather than being absent, ventricular untwisting appears to be similar if not even slightly enhanced in the elderly. Clearly, diastolic abnormalities occur in the aged heart, but their cause is multifactorial and may not be due to an absence diastolic suction. As our study suggests, these changes are not necessarily the primary limiting factors in determining exertional efficiency and performance in the elderly.
- American College of Cardiology
- ↵Dong SJ, Buffer SA, Fleg JL, Hees PS, Weiss JL, Shapiro EP. Recoil rate and early diastolic function are coupled in the young but not the elderly. Circulation 1996;94 Suppl I:I-681.