[Thallium-201 myocardial imaging in cases involving transposition of the great arteries after arterial switch operation]

Abstract Forty patients, including 39 with complete transposition of the great arteries and one with double outlet right ventricle, after arterial switch operation were studied with thallium myocardial imaging (TMI). In patients who had post-operative cardiac catheterization, the TMI findings were compared to those of catheterization studies. The right ventricular to left ventricular up-take ratio (RV/LV ratio) shown by TMI correlated well with the right-to-left ventricular systolic pressure ratio. Supravalvular pulmonic stenosis with significant pressure gradient was found in 14 patients, and all of them were noted to have an elevated RV/LV ratio. This ratio was noted to increase progressively on serial TMI studies in most patients who had significant pulmonic stenosis on first postoperative catheterization. Three patients had significant perfusion defects indicating the presence of myocardial damage. Two of them had occlusion of the coronary artery, but the other one had no coronary abnormalities able to be found by coronary arteriography. Air embolism or some other intra-operative transient insults to the myocardium were most likely to have been responsible for the perfusion defects. Thus, TMI was valuable as one of the noninvasive tools for follow-up of patients after arterial switching, particularly for those with late complications such as supravalvular pulmonic stenosis and coronary problems.