[In Process Citation]

Abstract

INTRODUCTION AND AIMS: Transposition of the Major Arteries (TMA) is defined as atrioventricular concordance with ventriculoarterial discordance. Systemic and pulmonary circulation are in parallel and a communication between the two is essential for survival. Progress in echocardiography, cardiac catheterization, treatment with prostaglandin and cardiac surgery have reduced mortality and contributed to the adoption of Jatene's operation as the treatment of choice for TMA. Long term success depends on the continued patency of the coronary arteries and on the preservation of left ventricular function. Reports of significant silent coronary lesions and the uncertainty of long-term growth of the arterial anastomosis lead us to study coronary circulation in TMA. METHODS: Anatomic analysis of 130 heart specimens was followed by a prospective angiographic study in 50 children with TMA to select appropriate views for the diagnosis of the coronary anatomy. Troponin-T was tested as marker of myocardial ischaemia in 54 children and myocardial function was evaluated in 30 children after Jatene's operation with myocardial perfusion scintigraphy, dobutamine-induced stress echocardiography and angiocardiography. Permeability of the coronary arteries was assessed with angiocardiography. RESULTS: The morphologic study led us to conclude that the right-anterior aorta was present in 65% of hearts with TMA, followed by side-by-side great arteries; the pulmonary orifice was of the same size or larger than the aortic orifice in the majority of TMA. Major non-alignment of the aortic and pulmonary comissures was recorded in 14 to 30% of TMA specimens. The diameter of the coronary orifices was larger in TMA when compared to a normal heart. In cases with right anterior aorta, normal coronary pattern was the most frequent, followed by the pattern where the circumflex coronary artery (Cx) emerged from the right coronary (RCA). In cases with side-by-side great arteries, both patterns were equally frequent. In TMA with normal coronary pattern, the angles between the right and left coronary arteries and the aorta at the origin were equal and similar to the RCA angle with the aorta in a normal heart (about 90 degrees). The RCA in TMA was longer than in a normal heart. Although we could not find any publication reporting the angles and lengths of the coronary arteries, these measurements must be considered whenever translocation of the coronary arteries is attempted. A laid-back aortogram led us to the correct diagnosis of the coronary anatomy prior to surgery. Our study confirmed that MBCK had very low specificity for myocardial ischaemia but cTnT values correctly evaluated the extent of the myocardial lesion. Postoperative angiograms showed patent coronary arteries with no stenosis in all cases and myocardial perfusion was well preserved almost three years after surgery. The detection of ischaemic changes in three cases, in perfusion scan with normal function on stress-echo and on left ventriculogram, led us to warrant on-going follow-up.