Intravenous isosorbide dinitrate during open-heart surgery and its role in the treatment of right-sided congestive heart failure.

Recent awareness of the importance of the functional integrity of the right ventricle and the effect of raised pulmonary vascular resistance on cardiac output after cardiopulmonary bypass has focused attention on means of protecting right ventricular myocardium and reducing right ventricular afterload during open-heart surgery. A study of the acute effects of bolus intravenous isosorbide dinitrate (ISDN) has shown that after cardiopulmonary bypass, bolus intravenous ISDN produced highly significant (p less than 0.001) decreases in mean pulmonary arterial pressure (13%), pulmonary vascular resistance (23%) and the ratio of pulmonary to systemic vascular resistance (20%), indicating that active pulmonary vasodilation had occurred in the absence of other hemodynamic changes. The results suggest that possibly the acute effect of low-dose ISDN after cardiopulmonary bypass is predominantly exerted on the right ventricular afterload if systemic arterial pressure is not elevated. Two different clinical situations are described in which intravenous ISDN proved beneficial, one being acute pulmonary hypertension after protamine sulphate and the second being acute right-sided congestive heart failure with systemic hypotension unresponsive to conventional therapeutic measures. Thus, ISDN may prove a useful agent for alleviating right ventricular dysfunction at a time of not infrequent cardiovascular instability, the period after bypass.