DO REPOLARIZATION ABNORMALITIES IN HYPERTROPHIC CARDIOMYOPATHY REPRESENT IMPAIRED FATTY-ACID UTILIZATION - AN OBSERVATION WITH QRST ISOINTEGRAL MAPS

To identify the clinical significance of the isointegral body surface map of the QRST interval (QRST map) and the occurrence of repolarizati on abnormalities in patients with hypertrophic cardiomyopathy (HCM), t he QRST map and signal-averaged electrocardiogram were evaluated in 50 patients with HCM, in 33 of whom the results were compared with nucle ar images both for radioiodine-labeled fatty acid metabolism and for r adiothallium perfusion. The QRST departure map was used to determine t wo parameters of difference between patient and control recordings: th e subnormal area (the number of lead points at which the departure ind ex values were negative and lay more than 2 SDs from the mean of the n ormal control group) and the subnormal minimum (the absolute value of the minimum in the departure mao). Late potentials were detected in 6 (12%) of the 50 patients; they were observed in 3 of the 5 patients wi th dilated-phase HCM but in only 3 (7%) of the other 45 patients. The subnormal area and minimum values were lower in nonobstructive HCM tha n in dilated-phase HCM. Of the 33 patients examined by myocardial imag ing, 28 (33%) had a filling defect or decreased uptake, as shown on fa tty acid metabolic images, and 10 of the 28 also showed abnormal myoca rdial perfusion images, while the 18 others showed normal perfusion im ages. These 28 patients showed significantly larger values of the subn ormal area and minimum than patients with normal results in both image tests, regardless of whether or not myocardial perfusion imaging abno rmalities were present. The localization of filling defects or of decr eased uptake presented in fatty acid metabolic images corresponded to the position of the minimum on the QRST departure map. These results s uggest that the QRST map is useful for detection of repolarization abn ormalities in HCM and that these abnormalities are highly related to i mpaired fatty acid utilization of the myocardium.