The effect of high-dose intravenous nitroglycerin on cardiovascular hemodynamic features and left ventricular function at rest and during exercise in patients with exertional angina

Intravascular pressures, cardiac output and left ventricular function were measured at rest and during exercise in 14 patients with stable angina pectoris before and during an intravenous nitroglycerin infusion. Nitroglycerin was infused at a rate sufficient to reduce mean arterial pressure at rest by 15 to 25 mm Hg.At rest, the end-diastolic volume index decreased from 57 ± 13 to 39 ± 3 ml/m², stroke volume index from 32 ± 6 to 24 ± 5 ml/m² and mean arterial pressure from 112 ± 16 to 91 ± 14 mm Hg. The cardiac output was maintained by an increase in heart rate from 73 ± 9 to 92 ± 37 beats/min. The left ventricular ejection fraction increased from 57 ± 7 to 62 ± 9% because the stroke volume decreased less than the end-diastolic volume.All 14 patients were limited by angina in the prenitroglycerin exercise study, and the mean ST-segment depression at maximal work load was 2.2 ± 1.2 mm. At identical work loads in the nitroglycerin study, only 4 patients had angina, and the mean ST-segment depression was 0.3 ± 0.5 mm. Ten of the 14 patients improved their exercise performance by at least 30 W.Comparing the 2 exercise studies at the maximal work load achieved in the prenitroglycerin study, the mean pulmonary artery wedge pressure was decreased from 23 ± 6 to 6 ± 4 mm Hg, the end-diastolic volume index from 38 ± 15 to 27 ± 12 ml/m², and the mean arterial pressure from 132 ± 8 to 114 ±13 mm Hg. The stroke volume index and the heart rate were not significantly altered and the ejection fraction increased from 56 ± 8% to 66 ± 8%.Thus, in the high dose administered, nitroglycerin decreased left ventricular filling pressure, heart size, and stroke volume at rest and increased the ejection fraction. During exercise, nitroglycerin decreased myocardial ischemia and improved exercise tolerance. An increase in exercise ejection fraction was associated with an increase in the ratio of systolic pressure to end-systolic volume, suggesting that there was an improvement in contractile performance.