Comparison of different noninvasive methods of infarct sizing during experimental myocardial infarction

This study evaluated the accuracy of several noninvasive infarct-sizing techniques in 12 awake, unsedated dogs with multivessel coronary obstructions and acute anterior myocardial infarcts. Estimations of infarct size by scintigraphy with technetium-99m Sn pyrophosphate (Tc-PP), serum creatine phosphokinase (CPK) release, peak serum myoglobin levels by radioimmunoassay, and precordial ECG mapping were compared and correlated with histologic measurements of infarct size. The comparisons indicate that precordial ST segments mapping, serum CPK release measurements and peak serum CPK, peak serum myoglobin, and Tc-PPi myocardial scintigraphy all provide approximate estimates of infarct size in this model. Each technique also has certain important limitations, however, including: (A) precordial mapping is relatively insensitive in the identification of small anterior infarcts, (B) serial serum CPK release measurements when obtained for only 24 hr after infarction tend to underestimate large anterior infarct size, and (C) Tc-PPi myocardial scintigrams may fail to recognize anterior infarcts less than 3 gm in size and may overestimate the size of small predominantly subendocardial infarcts. The findings also show that the closest estimate of histologic infarct size in this model was provided by combining two of the noninvasive techniques (precordial mapping to identify sites with 2 or more millimeters of ST segments elevation and Tc-PPi myocardial scintigrams) rather than by relying exclusively on any one technique alone.