Vasodilators in left ventricular failure.

Vasodilator drugs are generally classified according to their prevalent site of action: arteriolar vasodilators (e.g. phentolamine, hydralazine, nifedipine) which reduce peripheral resistance and, therefore, increase stroke volume and cardiac output; venodilators (e.g. nitrates), which decrease filling pressure, redistributing intravascular blood volume from the central to the peripheral reservoirs and therefore relieve signs and symptoms of congestion; "balanced" vasodilators (e.g. nitroprusside, prazosin, captopril) which present both effects. Vasodilator therapy is indicated in heart failure caused by impaired contractility (congestive cardiomyopathy, ischemic heart disease) and volume overload (mitral and aortic regurgitation, ventricular septal defect). Hemodynamic studies of acute pharmacological effects are necessary for a correct drug choice, even if they are not always predictive of the long-term efficacy. Non-invasive studies (in particular echocardiography) don't seem actually adequate for vasodilator therapy evaluation. Finally it is not known if vasodilator treatment influence prognosis of chronic heart failure (especially survival), but there is evidence that it can lessen symptoms and increase effort tolerance.