ISA--vasodilatation: improvement of organ perfusion.

1. In almost all forms of established hypertension the increase in blood pressure can be attributed to increased total peripheral vascular resistance. 2. beta-adrenoceptor blocking compounds, which are frequently used as first-line therapy in hypertension, may compromise blood flow to vital organs in view of the fact that they reduce cardiac output both acutely and during long-term treatment. 3. beta-adrenoceptor blocking agents with a marked intrinsic sympathomimetic activity (ISA) such as pindolol differ in this respect by lowering arterial pressure without lowering cardiac output while causing a reduction in total peripheral resistance. 4. Direct vascular effects of beta-adrenoceptor blockers with marked ISA could contribute to the normalisation of hypertension-induced structural arteriolar changes. The effect appears to be dissociated from the effect caused by the lowering of blood pressure per se.