ST-SEGMENT HEART-RATE LOOP ANALYSIS ON TREADMILL EXERCISE TESTING CANPROVIDE DIAGNOSTIC AND PROGNOSTIC INFORMATION IN PATIENTS WITH STABLEEFFORT ANGINA

Background: In the assessment of myocardial ischemia and its severity using treadmill exercise testing (TMET), the magnitude of ST-segment d epression is conventionally used. It is often difficult to distinguish false-positive from true ST-segment depression and to assess the seve rity of coronary artery disease (CAD). The purpose of the present stud y was to assess the ability of ST-segment/heart rate loop (ST/HR loop) analysis to provide diagnostic and prognostic information in patients with stable effort angina. Methods: ST/HR loop analysis was studied i n 118 patients with stable effort angina without previous myocardial i nfarction who were taking medication. ST/HR loop patterns were classif ied into four types: type A (n = 38), simple clockwise rotation; type B (n = 34), clockwise rotation with quick ST recovery in the first hal f; type C (n = 21), ST-segment depression that recovered at a constant rate; and type D (n = 25), simple counter-clockwise rotation. The con trol group consisted of 40 patients who had no ST-segment depression b ut were proved to have significant stenosis on coronary angiography. T he ST/HR loop types were compared with (1) the conventional TMET param eters, (2) findings of coronary angiography, (3) severity of ischemia evaluated by exercise thallium-201 myocardial single-photon emission c omputed tomography (exercise Tl-201 myocardial SPECT), and (4) short-t erm prognosis by follow-up study. Results: The value of the simple hea rt-rate-adjusted ST-segment depression index (Delta ST/HR index) in th e type A group (6.1+/-5.8 mu V/bpm) was higher (P<0.05) than in the ty pe C and D groups (2.7+/-2.0 mu V/bpm and 1.7+/-1.2 mu V/bpm, respecti vely). In the type A group, 68% of the patients had multiple diseased coronary arteries. In the type D group, 88% of the patients had either no significant coronary artery stenosis or significant stenosis in a single coronary artery. The ischemic size calculated by exercise Tl-20 1 myocardial SPECT was higher (P<0.05) in the type A group (47.6+/-24. 6%) than in the type B, C, and D groups (21.4+/-16.6%, 14.9+/-15.8% an d 7.8+/-7.4%, respectively). During the follow-up study nine cardiac e vents occurred in the type A group, three in the type B group, and one in the type C group. The prognosis of the type A patients was signifi cantly worse than that of the type D and control patients (P<0.01). Co nclusion: We conclude that the ST/HR loop analysis is a simple and use ful parameter for providing diagnostic and prognostic information for patients with stable effort angina.