ASSESSMENT OF MYOCARDIAL VIABILITY IN PATIENTS WITH PREVIOUS MYOCARDIAL-INFARCTION BY USING SINGLE-PHOTON EMISSION COMPUTED-TOMOGRAPHY WITHA NEW METABOLIC TRACER - [I-123] 16-IODO-3-METHYLHEXADECANOIC ACID (MIHA) - COMPARISON WITH THE REST-REINJECTION TL-201 TECHNIQUE

Objectives. We compared the ability of rest single-photon emission com puted tomography (SPECT) with [I-123] 16-iodo-3-methylhexadecanoic aci d (MIHA) and the thallium-201 (Tl-201) rest-reinjection technique to d etect myocardial viability after infarction. Background. After myocard ial infarction, MIHA frequently shows increased uptake in the areas wi th exercise Tl-201 defects (mismatch), even in patients with an irreve rsible Tl-201 reinjection defect. Whether such increased uptake is ind icative of ischemic but viable myocardium is not known. Methods. We st udied 38 patients who 1) underwent exercise SPECT Tl-201 with rest-rei njection and rest SPECT with MIHA before undergoing percutaneous trans luminal coronary angioplasty (PTCA) of an infarct-related coronary art ery, and 2) were found to have successful revascularization at follow- up angiography. The relation between SPECT results before PTCA and sub sequent improvement in left ventricular wall motion was assessed. Resu lts. A mismatch was evident before PTCA in 51 of 76 infarct-related se gments and correlated with subsequent improvement in wall motion (over all accuracy 71%), even for the 27 segments whose exercise defects rem ained irreversible after Tl-201 reinjection (overall accuracy 81%). Th e finding of a mismatch clearly enhanced the results provided by the f inding of greater than or equal to 50% Tl-201 uptake as determined at redistribution (p < 0.05), but not as determined at reinjection, altho ugh there was a trend toward a better specificity for the findings of a mismatch. Conclusions. MIHA is an efficient marker of viability insi de exercise underperfused areas after infarction, even in patients wit h irreversible Tl-201 reinjection defects. Assessment by conventional SPECT of a mismatch between results obtained with a metabolic tracer ( MIHA) and a flow tracer analyzed at exercise (Tl- 201) as a marker of myocardial viability is a promising area of research. (C) 1997 by the American College of Cardiology.