Potential Pathophysiologic Mechanisms of Action

\s=b\Twenty patients with refractory rest angina pectoris were treated with intravenously (IV) administered nitroglycerin (mean dosage, 72.4 \g=m\g/min;range, 15 to 226 \g=m\g/min).There was a considerable reduction or abolition in the number of ischemic episodes in 85% of patients without overall substantial changes in heart rate, mean arterial BP, pulmonary capillary wedge pressure (PCWP), and pulmonary arterial mean pressure. However, those patients with an initial PCWP of more than 12 mm Hg or a systolic pressure of more than 130 mm Hg had a substantial reduction in PCWP and systolic BP following IV nitroglycerin. We conclude that IV nitroglycerin may relieve rest angina by different pathophysiologic mechanisms. In some patients, IV nitroglycerin favorably altered the hemodynamic determinants of myocardial oxygen consumption. In others, however, no change in these determinants occurred, suggesting a direct effect on the coronary circulation. (Arch Intern Med 1982;142:1806-1809) T ntravenously (IV) administered nitroglycerin has been reported to be useful in the management of patients with unstable angina pectoris1"4 with rapid attainment and main¬ tenance of therapeutic blood levels by continuous infusion.5 We prospectively evaluated the use of IV nitroglycerin in the treatment of 20 patients with refractory rest angina, and addressed the potential pathophysiologic mechanisms involved in its action.