Quantitation of size of myocardial infarctions by computerized transmission tomography. Comparison with hot-spot and cold-spot radionuclide scans.

The current study evaluated the ability to quantitate the volume of myocardial infarctions when they are outlined by intravenously administered contrast media in the myocardial perfusion phase and in the phase of delayed contrast enhancement of the infarct. Quantitation by contrast media was assessed from computerized transmission tomography (CTT) scans of the ex situ heart and compared with quantitation by technetium-99m (99mTc)pyrophosphate (99mTc PYP) and thallium-201 (201Tl) scans of the same ex situ hearts. True volume was defined by histochemical morphometry. CTT during the contrast perfusion phase uniformly underestimated infarct size but had a good correlation with true volume (r = 0.87). CTT during enhancement phase correlated closely with true volume (r = 0.98) and most precisely measured true size (y = 1.06 X 0.23). The 99mTc PYP scan overestimated infarct volume (predictive overestimation of 6 to 199%) but had a good correlation with true volume (r = 0.87). 201Tl underestimated infarct volume but correlated well with true volume (r = 0.94). Thus, quantitation of infarct volume from CTT scans performed during either the perfusion or infarct enhancement phase after intravenous contrast media provides a good estimate of true infarct volume. Delineation of the infarct by contrast media in the ex situ heart is more precise during the phase of delayed enhancement of the infarct.