Time-related effects of chronic atenolol treatment on cardiovascular responses to handgrip

To assess the influence of chronic atenolol therapy on the cardiovascular responses to isometric exercise, we evaluated the behavior of blood pressure, heart rate and double product in 75 hypertensive patients treated with atenolol 100 mg once daily for 6 months. During the 1st month of treatment, both systolic blood pressure (SBP) and diastolic blood pressure (DBP) increases rose more than before treatment. SBP increase to handgrip became lower than before treatment on the 2nd months of therapy (p less than 0.05) and fell even more afterwards (p less than 0.01 on the 6th month). On the contrary, DBP increase subsequently steadied on levels not significantly different from those before treatment. Double product increase was inferior to that recorded before atenolol administration; the difference became significant after 2 months and reached its apex after 6 months of treatment. The conclusion was that chronic atenolol therapy affected some cardiovascular responses to handgrip although to a different extent depending on treatment length; it would seem sensible to pay attention to how long a patient has been on beta-blocker when evaluating the response to isometric exercise.