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Heart rate–lowering drugs such as verapamil improve aerobic exercise performance in healthy elderly individuals: a new way to look at left ventricular diastolic function in the elderly
Mauro Bertella, MDa,
Patrizia Valentini, MDa and
Romano Valentini, MDa
a Operative Unit of Cardiology, General Hospital, 20059 Vimercate, Italy
Chen et al. (1) demonstrated that early administration of intravenous verapamil reduces ventricular-vascular stiffening and improves aerobic exercise performance in healthy elderly individuals. Previously Arrighi et al. (2) reported that verapamil can induce selective enhancement of the left ventricular (LV) diastolic filling in middle-aged and elderly subjects, compared with young adults. When looking closer at the action of verapamil in determining its beneficial effect, an important result of Chen’s study appears to be insufficiently considered by the authors.
When comparing heart rate variations by using the Student two-tailed paired t test, we observed, in Chen’s study, that significant differences exist in placebo versus verapamil treatment at peak stress (134.1 ± 5.9 vs. 126.8 ± 5.9 beats/min, p < 0.0001), at 25-W exercise (96.8 ± 3.2 vs. 92.6 ± 4.4 beats/min, p = 0.003) and before exercise (69.8 ± 2.0 vs. 67.9 ± 2.4 beats/min, p = 0.028). To unravel the importance of the heart rate–lowering effect of verapamil in improving abnormalities of diastolic function in elderly individuals, one must carefully study how ventricular filling occurs in young as compared with old patients. We recently suggested that LV diastolic function can be correctly studied only when the functional interaction between the LV and aorta is considered (3). In young patients, systolic contraction of the interventricular septum and longitudinal fibers of the LV cause the following: 1) movement of the mitral annulus toward the cardiac apex and 10% prolongation of the ascending aorta (4); and 2) a clockwise torsion (twisting) of the base of the heart, which moves the aortic root forward (5). Color M-mode Doppler echocardiography with the cursor positioned on a pulmonary vein (longitudinal long-axis view) can detect an increase in blood flow from the pulmonary veins into the left atrium owing to these movements (3). In early diastole, an opposite movement (untwisting) brings the annulus and the aortic root back to their initial position (6). Untwisting creates a favorable situation for "ventricular suction," a phenomenon that explains "LV rapid filling" and the improved tolerance of exercise-induced tachycardia in the young as compared with the elderly (7).
In elderly individuals, the aorta loses its elasticity and the base of the interventricular septum becomes hypertrophic, thus developing into a sigmoid shape (8). It is possible to observe with two-dimensional echocardiography that the basal septum tries, in vain, to distend the ascending aorta toward the apex; as it contracts just before ventricular ejection, it acts like a lever by making the aorta snap forward, thus increasing the anteroposterior diameter of the left atrium (3). In some elderly patients in whom the ascending aorta is particularly elongated, a reduction of the end-diastolic angle between the interventricular septum and the aortic root may be observed. In these cases, the LV, by reducing its longitudinal diameter during systole, causes a forward movement of the aortic bulb and also a shift toward the apex of the part of annulus that is not connected to the aortic root. These movements expand the left atrium and draw blood from the pulmonary veins as long as the heart rate is not high (3).
It has been proven that ventricular diastolic suction is not present in the elderly (9). In these conditions, even a healthy elderly individual needs an adequate diastolic filling time to achieve satisfactory exercise performance. The heart rate–lowering effect of verapamil could be important to explain the improved LV diastolic function in elderly patients, even after a single intravenous dose of the drug.
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1. Chen HC, Nakayama N, Talbot M, et al. Verapamil acutely reduces ventricular-vascular stiffening and improves aerobic exercise performance in elderly individuals. J Am Coll Cardiol. 1999;33:1602–1609[Abstract/Free Full Text]
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