Paradoxical electrocardiographic effects of amyl nitrite in coronary artery disease.

i had angina with normal coronary arteries. This group was compared with i5 patients who had angiographically proven coronary artery disease and positive treadmill tests but negative amyl nitrite tests: the group with positive amyl nitrite tests responded to drug inhalation with a significantly greater heart rate increase (47% vs. 34%, P< o.oI), and a significantly greater fall in systolic blood pressure (42% vs. 31%, P< o'o5) and diastolic blood pressure (42% vs. 29%, P< o os). Atrial pacing studies in 4 patients suggested that the amyl nitrite induced ischaemic changes were not due to tachycardia alone. No patient with a negative treadmill test had a ,positive amyl nitrite test; positive amyl nitrite tests became negative after revascularization surgery, propranolol therapy, or clinical improvement. The paradox of ischaemic electrocardiographic changes caused by amyl nitrite is probably explained by the observed acute reduction of coronary perfusion pressure and abbreviation of diastole. Amyl nitrite may have clinical application in the diagnostic and therapeutic evaluation of coronary artery disease.