Regression of left ventricular hypertrophy after a reduction
in blood pressure has been reported with most
antihypertensive medications. However, the effects
of prolonged exercise on ventricular structure and function
are not clear. The rigorous exercise endured by
athletes can provoke cardiac enlargement. The “athlete’s
heart,” as it is commonly called, is exercise-specific.
Purely aerobic exercises induce enlargement of
the left ventricular cavity, with no changes in left-ventricular-wall
thickness. In contrast, combined isotonic
and isometric exercise (e.g., weight training and rowing)
may lead to substantial hypertrophy of the left ventricular
wall. Nevertheless, exercise-induced left ventricular
hypertrophy is considered a normal physiologic
adaptation to the particularly rigorous training of athletes.
It is not associated with diastolic dysfunction,
arrhythmias, or an adverse prognosis, as is hypertension-induced
left ventricular hypertrophy, and it regresses
quickly with detraining.
In contrast to athletes, our patients exercised at a relatively
low intensity and duration. After 16 weeks of
such training, we observed a significant reduction in
the thickness of the interventricular septum and 12 percent
reductions in left ventricular mass and left-ventricular-mass
index. The reduction in left ventricular mass
was similar to the reduction of 8 to 15 percent in overall
left ventricular mass that has been reported in drug
studies. There were no changes in any echocardiographic
measurements in the no-exercise group. Our
findings and those of studies of highly trained athletes
suggest that the intensity and duration of exercise
may have an important effect on left ventricular
structure.
The mechanisms involved in the regression of left
ventricular hypertrophy in the patients in our exercise
group are not readily apparent. It is likely that the reduction
in blood pressure has played a part. In general,
most antihypertensive regimens that lower blood pressure
induce various degrees of reduction in left ventricular
mass without any drug-specific effects.Other
factors, however, such as levels of angiotensin II and
catecholamines, may be involved.38 Prolonged physical
activity decreases plasma catecholamines in some hypertensive
patients.
In conclusion, we found that African-American men
with severe hypertension and left ventricular hypertrophy
benefit from a combined regimen of regular, moderately
intense aerobic exercise and antihypertensive
drug therapy. The antihypertensive effects of exercise
substantially reduced the amount of medication required
to control blood pressure.