CHANGES IN MYOCARDIAL LACTATE METABOLISM DURING RAMP EXERCISE IN PATIENTS WITH EFFORT ANGINA AND MICROVASCULAR ANGINA

Changes in myocardial lactate metabolism during ramp exercise were inv estigated through great cardiac vein catheterization in 15 patients wi th effort angina (EA) and 7 patients with microvascular angina (MVA). The exercise test was performed using a supine bicycle ergometer. Bloo d samples were obtained from the great cardiac vein (GCV) and the radi al artery each minute during exercise. Patients in the EA group showed a point at which the lactate extraction ratio (LER) and the ST level decreased rapidly during exercise. This point was clearly recognized i n 12 of 13 patients, and may represent the ischemic threshold. Both th e LER and ST level showed similar changes during exercise, and these v alues were significantly different between the ischemic threshold and peak exercise (p < 0.01). Both the LER and ST level were strongly corr elated with the duration of exercise until the threshold (r = 0.703). In the MVA group, both the LER and ST level during exercise continuous ly decreased throughout exercise without an ischemic threshold in all of the subjects, Endomyocardial biopsy revealed sclerosis of small art eries in the myocardium in all of the patients. In both effort angina and microvascular angina, a close correlation was noted between the ch ange in ST and that in the myocardial lactate extraction ratio.