Correlation between exercise-induced ischemic ST-segment depression and myocardial blood flow quantified by positron emission tomography.
BACKGROUND
Ischemic ST-segment depression (horizontal or downsloping) is the most common manifestation of exercise-induced myocardial ischemia. The mechanisms responsible for these types of ST-segment depression are largely unknown. We investigated the relation of these 2 types of exercise-induced ST-segment depression to changes in regional myocardial blood flow (RMBF) by using exercise positron emission tomography (PET).


RESULTS
The RMBF was measured with nitrogen-13 ammonia PET both at rest and during low-level supine bicycle exercise in 27 patients with angiographically proven coronary artery disease and in 6 healthy volunteers. ST-segment depression was measured from the isoelectric PR segment 80 ms after the J point. Exercise-induced horizontal ST-segment depression > or =0.1 mV was observed in 9 patients and downsloping depression > or =0.1 mV was observed in 18 patients. Multivessel disease was more frequent and areas of exercise-induced ischemia were larger in patients with downsloping depression than in patients with horizontal depression (P < .02, P < .05). In patients with horizontal ST-segment depression, RMBF in ischemic areas and in surrounding areas increased by a similar amount (31%+/-29% and 32%+/-16%) with exercise. In patients with downsloping ST-segment depression, RMBF was unchanged or decreased in ischemic areas (10%+/-24%) but increased in surrounding areas (46%+/-27%) with exercise. In healthy volunteers, RMBF increased in all areas (56%+/-30%) with exercise.


CONCLUSIONS
Compared with horizontal changes in ST-segment morphology, downsloping changes may better indicate severe ischemia and greater differences in the increase of blood flow with exercise in the ischemic myocardium and in the surrounding areas.
Watanabe
T
T
Third Department of Internal Medicine, Fujigaoka Hospital, Tokyo, Japan.
Harumi
K
K
Akutsu
Y
Y
Yamanaka
H
H
Michihata
T
T
Okazaki
O
O
Katagiri
T
T
D000328:Adult; D000368:Aged; D000818:Animals; D001642:Bicycling; D015986:Confounding Factors, Epidemiologic; D017023:Coronary Angiography; D003326:Coronary Circulation; D004562:Electrocardiography; D005080:Exercise Test / Q000379:methods; D005260:Female; D006329:Heart Conduction System; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D014055:Tomography, Emission-Computed / Q000379:methods