1. Fifteen patients with essential hypertension, class I, II WHO, nine males and six females, whose mean age was 46 years, were given atenolol, 100 mg a day, for 1 year.
2. After 1 month, compared with control, systolic and diastolic blood pressures, heart rate and cardiac output were reduced, whereas left ventricular end-diastolic dimension and stroke volume were increased and total vascular resistances, wall stress, left ventricular mass and h/diastolic radius (R) ratio were unchanged.
3. After 1 year, compared with control, systolic and diastolic blood pressures, heart rate and cardiac output were still reduced, total vascular resistance and wall stress were unchanged. End-diastolic dimension and stroke volume reverted to previous values; left ventricular mass and h/R ratio were significantly decreased.
4. These results show that left ventricular hypertrophy in essential hypertension can revert after 1 year of treatment with atenolol, at least in relatively young people. Since the left ventricle wall stress was not changed after atenolol, the regression of left ventricle hypertrophy seems prevalently to be related to the decrease of adrenergic activity of the heart.