Perfusable Tissue Index Obtained by Positron Emission Tomography as a Marker of Myocardial Viability in Patients With Ischemic Ventricular Dysfunction

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In areas of severe asynergy, the clinically important task is to identify functionally recoverable myocardium. Fourteen patients with asynergy were investigated by H₂ ¹⁵O dynamic positron emission tomography imaging before revascularization. Regional myocardial blood flow (MBF) was determined and the water-perfusable tissue fraction (PTF) for each region of interest and the total anatomical tissue fraction (ATF) were estimated. The PTF/ATF was analyzed as the water perfusable tissue index (PTI). Asynergy was defined as segments with wall motion more than 2 SD below than that of a normal population. An increase of >0.8 SD in anterior wall segments with asynergy and an increase of >0.6 SD in inferior wall asynergy were defined as significant improvements of wall motion indicative of viable myocardium. Fifteen segments with wall motion abnormalities less than -2 SD and 10 control segments were identified; 7 segments recovered and 8 segments did not. MBF was similar in both groups of segments before revascularization (0.78 ±0.27 vs 0.73±0.18 ml · min ^-1 · g^-1, NS). The PTI in the recovered segments was significantly higher than that in the unimproved segments (0.734±0.058 vs 0.592 ±0.038, p<0.0001) and was similar to that of the control segments. After revascularization, the PTI correlated with the SD of wall motion (p<0.05, r=0.58). PTI may be a good predictor of contractile recovery after revascularization. (Circ J 2002; 66: 341 - 344)