Vasodilatation of small and large arteries in hypertension.

In patients with essential hypertension, vasodilating antihypertensive drugs act differently on small and large arteries. For similar blood pressure reductions, the diameter of the brachial artery may be unchanged (alpha- and beta-blocking drugs), decreased (dihydralazine), or increased (nitrates, renin-angiotensin and calcium-entry inhibitors). Increase in blood flow is due preferentially to an increase in blood flow velocity and is caused additionally by an increase in the diameter of the large artery. Increase in arterial compliance is observed only with nitrates, calcium-entry, and renin-angiotensin inhibitors. It is concluded that blood pressure reduction due to arteriolar vasodilatation may have various effects on the conducting function and the buffering function of large arteries, a point of importance in the prognosis of hypertensive cardiovascular disease.