Intravenous Nitroglycerine in Refractory Unstable Angina Pectoris

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Abstract
Sixteen patients with severe coronary artery disease and unstable angina, refractory to standard therapy with nitrates [isosorbide dinitrate] .beta.-blockers [propranolol, metoprolol and pindolol] or Ca antagonists [verapamil], were given i.v. nitroglycerin (500 .mu.g/ml) in an open trial. The infusion was started at 0.17 ml/min. The final infusion rate ranged from 0.17 ml/min to 2.04 ml/min, depending on the symptomatic and hemodynamic response of the individual patient. At the slow infusion rates, the actual dose was probably only 15% of the delivered dose because of the adsorption of nitroglycerin to PVC [polyvinyl chloride] tubing. There was significant pain relief in all patients. In 6 patients, pain relief was complete; in 10 patients, occasional episodes occurred during the nitroglycerin infusion but they were less frequent and less severe and few were associated with ST segment changes. Systolic blood pressure fell by a mean of 100 mmHg at the commencement of therapy but there was no significant change in heart rate. Apart from mild headaches, no other adverse effects were observed. The mean treatment time was 3.2 days (range 1-8 days). Eight patients were discharged on oral and/or cutaneous nitrate therapy and 8 patients had coronary artery surgery. Nitroglycerin i.v. is useful for controlling symptoms in patients with unstable angina refractory to conventional therapy and may be particularly valuable for settling these patients before coronary arteriography and during preparation for coronary surgery.