Vasodilator therapy for heart failure. Concepts, applications, and challenges.

Vasodilators are widely used in the treatment of heart failure patients even though the drugs are incompletely understood. Vasodilators oppose the excessive vasoconstriction of heart failure, but factors that control excessive vasomotor tone are poorly understood. Possible physiological benefits include more favorable distribution of blood flow and blood volume, but exact effects on blood vessels have been incompletely explored. As a result of vasodilation, preload and afterload reduction can improve cardiac performance, but the role of the blood vessels in the performance of the failing heart is not well understood. Clinical benefits include relief of dyspnea, improvement in tissue metabolism, and increase in exercise tolerance (in patients who have chronic heart failure). However, the degree of effectiveness among various causes of heart failure, different degrees of cardiovascular compensation, and different durations of failure is unknown.