Cardiac contractility and conduction: a comparison of antihypertensives. The four classes of first-line antihypertensive agents recommended in the 1988 report of the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure are reviewed here. Particular consideration is given to the effects of these agents on heart rate, atrioventricular nodal conduction, and myocardial contractility in patients with other cardiovascular diseases. Diuretics and angiotensin-converting enzyme inhibitors have no significant direct effects on cardiac function. beta-Blockers inhibit catecholamine stimulation of the heart and may be particularly beneficial in treating patients with a history of myocardial infarction. Calcium channel blockers reduce blood pressure by dilating arterial resistance vessels. They are structurally heterogeneous and highly selective in their sites of action. As a consequence, cardiac effects can be minimized by selecting a calcium channel blocker with more potent peripheral vasodilatory effects. A new calcium channel blocker, isradipine, currently undergoing clinical trials, is highly selective for arterial smooth muscle and appears to be a safe and effective antihypertensive agent. 