DIFFERENTIATING SYNDROME-X FROM CORONARY-ARTERY DISEASE BY TREADMILL EXERCISE TEST IN PATIENTS WITH CHEST PAIN AND EXERCISE-INDUCED MYOCARDIAL-ISCHEMIA

Even though the underlying mechanisms of myocardial ischemia may be di fferent, it is difficult to differentiate syndrome X from coronary art ery disease (CAD) by means of the treadmill exercise test in elderly p atients with chest pain and exercise-induced myocardial ischemia. One hundred sex-and age-matched patients-42 with syndrome X and 58 with CA D-were studied. Another 10 subjects with atypical chest pain, negative treadmill exercise test, and normal-appearing coronary angiograms ser ved as controls. We evaluated the difference in exercise performance b etween patients with syndrome X and CAD, and the treadmill exercise te st was undertaken with modified Bruce protocol within 2 weeks before c oronary angiography. Parameters including time to 1 mm ST segment depr ession (STD), exercise duration (ED), heart,rate (HR), systolic blood pressure, rate-pressure product (RPP), and percentage of age-predicted maximum HR (% HR) at different stages of the test were measured and t hen compared among the three groups of patients. Compared with CAD pat ients, syndrome X patients had significantly higher HR, % HR, and RPP at the time of 1 mm STD and at peak exercise. The time to 1 mm STD and ED were longer in syndrome X than in CAD patients. However, ED was sh orter and HR, % HR, and RPP at peak exercise were similar in syndrome X patients as compared with control subjects. The new criterion of com bined ED (greater than or equal to 315 seconds) and RPP at peak exerci se (greater than or equal to 24,000 beats x mmHg/min) was found to be highly specific (86%) and moderately sensitive (64%) in differentiatin g syndrome X from CAD patients. The positive likelihood ratio for this criterion was 4.57 and negative likelihood ratio was 0.42. In conclus ion, syndrome X patients had better exercise performance than CAD pati ents, but less ED and similar workload when compared with control subj ects. The new criterion proposed in this study may provide a quick and simple way to differentiate syndrome X from CAD in a group of-aged an d predominantly male patients with chest pain and positive treadmill e xercise test.