[Clinical application of the alkalosis induction test for coronary artery spasm]

Alkalosis was used for stress testing for coronary artery spasm in 70 patients (average age: 56 years) with resting angina. A rapid intravenous infusion of an alkaline buffer (THAM) immediately followed by 5 minutes' maximal ventilation increased the arterial pH to 7.67 +/- 0.5. Anginal pain and ECG changes were observed in 24 Patients, with ST elevation in 10 cases and ST depression in 14 cases. The ischaemic changes occurred during hyperventilation in 16 cases and in the 3 minutes following the test in 8 cases. The heart rate increased from 66 +/- II to 71 +/- 14 bpm (p less than 0,01) but systolic blood pressure fell from 139 +/- 12 to 130 +/- 12 mm Hg during hyperventilation; there was no significant change in the rate-pressure product (1130 +/- 1750 to 8990 +/- 2690). In all cases, the angina and ischaemic changes regressed after intravenous Trinitrin. Coronary angiography was performed in 56 patients: in the 24 patients with positive responses (Group I) and in 30 of the 46 patients with negative responses (Group II). Significant coronary artery narrowing (greater than 70%) was observed in 21 patients of Group I: in the 3 patients without coronary lesions an intravenous injection of 0.4 mg methylergometrine provoked coronary spasm. In Group II, significant narrowing was demonstrated in 18 patients: in the 12 other patients, coronary spasm could not be induced by methylergometrine. Therefore, in the absence of organic coronary lesions, an excellent correlation has been shown between the alkalosis and methylergometrine tests. This stress test was repeated in 16 of the 24 patients in Group I one hour after administration of 20 mg of Nifedepine: the test was negative in all cases. We conclude that the alkalosis test could be useful in the coronary care unit as a stress test for coronary spasm to determine the antianginal treatment of choice and to evaluate its efficacity.