Intravenous nitroglycerin suppresses exercise-induced arrhythmias in patients with ischaemic heart disease: implications for long-term treatment

We studied 20 patients with ischaemic heart disease, who consistentlydeveloped complex ventricular arrhythmias during exercise testing.Treadmill exercise was performed twice, both during the placeboinfusion and then during intravenous administration of nitroglycerin,titrated to reduce systolic blood pressure by 10 mmHg. Exerciseduration in those administered placebo was 7·8 ±1·7 and 7·9 ± 1·5 min, respectively(ns): angina developed in five patients and ischaemic ST changesin 10. In those administered nitroglycerin, exercise durationincreased to 8·4 ± 2 mm (P<0·05). DiagnosticST segment depression was observed in only two patients andonly one had angina. Ventricular arrhythmias, consistently presentduring both tests on those administered placebo, were dramaticallyreduced by nitroglycerin in all 20 patients. There were 455(mean 35·8± 16·8) and 4l8 (mean 34·4±11·1)ventricular ectopic beats in the two exercise tests on thoseadministered placebo and 11 in those receiving the nitroglycerininfusion (mean 0·6 ± 0·1 (P<0·001).There were 28 and 29 couplets in those receiving placebo (ns)and none in those receiving nitroglycerin (P<0·001).Ventricular tachycardia was present in six and eight patientswho received placebo but in none in those administered nitroglycerin(P<0·001). Abolition of exercise-induced arrhythmiaswas maintained during chronic treatment with oral coronary vasodilators.Prevention of exercise-related arrhythmias by nitroglycerinappears a good indicator of their ischaemic origin and may providevaluable information for long-term prophylaxis with oral vasodilators,thus avoiding antiarrhythmic agents with their potential sideeffects.