Combined thallium 201/technetium 99m-labeled pyrophosphate tomography for identification of the "culprit" vessel in acute myocardial infarction.

BACKGROUND

Many previous investigations have used the presence of transient ischemic 201Tl perfusion defect to localize coronary artery stenosis. This study reports the results of 201Tl tomography alone and combined 201Tl/99mTc-labeled pyrophosphate (99mTc PYP) tomography employed to identify the infarct-related vessel in patients with acute myocardial infarction (AMI).

METHODS AND RESULTS

All short-axis images were evaluated by dividing each left ventricular slice into eight equal sectors. In addition, for combined 201Tl/99mTc PYP tomography, two sectors were added to evaluate involvement of the right ventricle. In a preevaluation phase of the study, the sectors were assigned to the supplying coronary arteries in 75 patients with single chronic myocardial infarction related to the left anterior descending coronary artery (LAD), left circumflex artery (LCX), or right coronary artery (RCA). In this pilot phase, 201Tl tomograms were reviewed in conjunction with the angiographic data. This assignment was then tested prospectively in 117 patients with AMI. As confirmed by angiography, the AMI was related to the LAC, LCX, and RCA in 54, 17, and 46 patients, respectively. Sensitivity and specificity for 99mTc PYP accumulation on combined 201Tl/99mTc PYP tomography were 98% a nd 100% for the LAD, 88% and 99% for the LCX, and 98% and 96% for the RCA, respectively. For 201Tl tomography, sensitivity and specificity for identification of the culprit vessel were 94% and 89% for the LAD, 82% and 91% for the LCX, and 72% and 96% for the RCA, respectively.

CONCLUSION

This prospective study demonstrates that combined 201Tl/99mTc PYP tomography is highly accurate for identification of the infarct-related artery in AMI, even in patients with multivessel disease. Positive contrast visualization of myocardial necrosis in both the left and right ventricle allows for reliable differentiation between AMI related to the LCX or RCA territory. In comparison, for 201Tl tomography the sensitivity to detect the culprit vessel, particularly the LCX and RCA, appears to be lower than for 201Tl 99mTc PYP imaging, particularly in patients with prior infarction or right dominant coronary artery.