Provocative testing with prolonged hyperventilation and ergometrine in patients suspected of coronary artery spasm: a comparative study.

We induced coronary vasoconstriction by hyperventilation for 6 minutes (arterial pH = 7.6 +/- 0.06) and ergometrine (0.4 mg) in 24 patients suspected of coronary vasospasm. ST deviation greater than or equal to 1 mm was induced in 12 patients by hyperventilation and in 10 by ergometrine. Using spontaneous ST deviation as the independent reference the sensitivity of hyperventilation was 86% and the sensitivity of ergometrine 77%. Ergometrine caused sinus bradycardia and hypotension in 3 patients; hyperventilation caused no untoward reactions. In 12 of the patients coronary angiogram and wedge pressure were obtained during provocative testing. A computer-assisted analysis of coronary diameters in 43 arterial segments (3-4 per patient) showed a 16 +/- 12.6% and 14 +/- 16.7% reduction after hyperventilation and ergometrine, respectively. The maximal coronary diameter reduction induced by hyperventilation and ergometrine was 26 +/- 13.9% and 28 +/- 15.0%, respectively, and showed a significant correlation between the two tests (r = 0.77, N = 12, P less than 0.01). The wedge pressure increase induced by hyperventilation correlated to the maximal coronary diameter reduction (r = 0.63, N = 12, P less than 0.05), while no such correlation was found by ergometrine testing. We conclude that hyperventilation leading to arterial pH about 7.6 has essentially the same potency as 0.4 mg ergometrine, but the hyperventilation test appears to be safer.