Effect of long-term beta-adrenergic-blockade on calf blood flow in hypertensive patients

The effect of a four-week treatment with propranolol and metoprolol on blood pressure and regional haemodynamics of the lower extremity at rest, after exercise and during reactive hyperaemia was studied in 34 patients with essential hypertension, but without peripheral arterial disease, in a randomized placebo-controlled trial. No significant difference in side-effects recorded during the trial was observed between these two drugs. Treatment with beta-adrenergic blocking drugs reduced systemic blood pressure. Calf blood flow during vasodilatation was also decreased. The most marked changes were observed during reactive hyperaemia; mean calf blood flow was reduced from about 250 ml/min/litre of tissue to 200 ml/min/litre of tissue (P less than 0.01) by propranolol and to 214 ml/min/litre of tissue (P less than 0.01) by metoprolol. Both drugs caused a significant increase in peripheral resistance above the initial level during reactive hyperaemia (P less than 0.05). No significant difference in peripheral resistance was observed, however, when the active drugs were compared with the placebo. There was no difference between propranolol and metoprolol in any of the parameters. Thus, the flow reduction can mainly be attributed to the diminished perfusion pressure due to the decreased cardiac output caused by beta-blockade of the heart.