Usefulness of the hyperventilation test in stable exertional angina pectoris in selecting medical therapy

To assess the prevalence of abnormal coronary vasoconstriction in stable exertional angina and to evaluate whether the presence of increased coronary tone may have therapeutic implications, we studied 83 consecutive patients with typical exertional angina, positive response to exercise stress testing and documented coronary artery disease. Abnormal coronary vasoconstriction was induced by a hyperventilation test in 16 patients (group I) while the remaining 67 had a negative response (group II). No differences were observed between the 2 groups with regard to clinical, exercise and angiographic data. All group I patients and 16 patients in group II repeated hyperventilation and exercise tests after the administration of dihydropyridine-type calcium antagonists (7 patients nifedipine, 9 patients felodipine). After treatment 15 of 16 group I patients had a negative response to the hyperventilation test. The total exercise duration was significantly increased (278 ± 183 vs 554 ± 248 seconds; p <0.001) with higher values of rate pressure product at peak exercise (168 ± 47 vs 235 ± 67 mm Hg × beats/min/100; p <0.0025). In group II no significant differences were observed between pre- and posttreatment values for total exercise duration (244 ± 210 vs 308 ± 243 seconds) and rate pressure product at peak exercise (170 ± 46 vs 188 ± 56 mm Hg X beats/min/100). These data show that the hyperventilation test can be used to select a subset of patients with stable exertional angina and detectable abnormal coronary vasoconstriction who will improve their exercise tolerance with coronary vasodilator treatment.