HYPERVENTILATION TEST IN SYNDROME-X

The hyperventilation (HV) test has been extensively used in different forms of coronary artery disease. The purpose of this work was to inve stigate the response to HV in patients with syndrome X and compare HV with exercise (EX) test. The authors studied 20 patients with syndrome X (angina, a positive EX test, and normal coronary angiogram) and 20 healthy subjects who underwent HV and EX tests. In 7 patients, all wom en, angina and electrocardiographic (ECG) changes occurred during HV b ut in none of the controls. Patients with syndrome X and controls had a similar rate-pressure product (RPP) at rest and achieved a similar R PP with HV. The RPP achieved with HV in patients with syndrome X witho ut ECG changes was significantly lower, 121.8 +/-29.1 (mean +/-SD), th an what was achieved by those with changes, 167.9 +/-42.9, P < 0.01. I n patients with an abnormal response to HV the RPP at which angina and ECG changes occurred was similar to that where similar changes were o bserved during EX. There was a significant correlation of the RPPs bet ween the two tests, r=0.82, P < 0.02. In contrast, in patients in whom no angina or ECG changes occurred, the RPP they achieved with HV was significantly lower than the anginal threshold during EX 204 +/-47.4, P < 0.0001. In conclusion, a significant proportion of patients with s yndrome X, mainly women, who achieve a high RPP with HV, develop angin a and ECG changes during overbreathing. The close relation between EX and HV RPPs where these changes occur suggests an increased myocardial oxygen demand as the most likely underlying mechanism for this behavi or.