Effects of isosorbide dinitrate on the response to atrial pacing in coronary heart disease

To study the efficacy of isosorbide dinitrate in prevention of myocardial ischemia, 20 patients with angiographically proved coronary artery disease underwent atrial pacing (mean rate 138/min) before (P1), 10 minutes after (P2) and 65 minutes after (P3) sublingual administration of 5 mg of isosorbide dinitrate. The symptomatic, hemodynamic and metabolic responses were evaluated at rest and during each pacing period. Angina occurred in all subjects during P1. Angina did not recur or was less severe in 17 of 19 patients during P2 and in 19 of 20 patients during P3. Resting left ventricular end-diastolic pressure for the group was normal at 11 plus or minus 4 mm Hg (mean plus or minus standard deviation). On interruption of pacing at 4.5 minutes during P1, average end-diastolic pressure during sinus rhythm was abnormal (18 plus or minus 6 mm Hg). After administration of isosorbide dinitrate mean left ventricular end-diastolic pressure was significantly decreased at rest and remained normal when pacing was interrupted during P2 and P3. Brachial arterial pressure, cardiac index, tension-time index, left ventricular stroke work index and maximal rate of rise of left ventricular pressure were all diminished at rest before and during P2 and P3. S-T segment depression was less during P2 and P3 than during P1. Before isosorbide dinitrate was given, resting myocardial lactate extraction was 15 plus or minus 11 percent during P1 lactate extraction decreased to minus2 plus or minus 25 percent. Lactate extraction was significantly greater during P2 and P3 than during P1. This study demonstrates that sublingual administration of 5 mg of isosorbide dinitrate has a significant protective effect against pacing-induced myocardial ischemia at 10 and 65 minutes after administration.