Article Abstract

The paradox of choice in the surgical management of congenitally corrected transposition: what should we do with all of these options supported by little evidence?

Authors: Catherine Deshaies, Paul Khairy

Abstract

Despite the conceptually proper physiology consisting of independent in-series pulmonary and systemic circuits, the prognosis in patients with unoperated congenitally corrected transposition of the great arteries (ccTGA) is reserved, even in the absence of associated defects. This is attributable to several factors. Although reports have described unoperated patients with normal or near-normal systemic right ventricular (RV) function in their 60s and beyond (1,2), it is the exception rather than the rule. Faced with a systemic circulation, the morphologic RV fails in one third of patients with no associated lesions by the fifth decade of life, and in two thirds with prior surgery for concomitant defects by 45 years of age (3). When confronted with chronic pressure overload, the systemic RV invariably undergoes hypertrophic remodelling. Owing to its limited coronary reserve from the concordant predominantly single right coronary circulation, myocardial oxygen/supply mismatch can promote subendocardial ischemia, progressive fibrosis, and ultimately, overt heart failure (4-6). Second, the tricuspid valve, again part of the systemic circulation, frequently displays Ebsteinoid features with propensity for regurgitation. While the direction of the causal relationship between tricuspid insufficiency and RV dysfunction remains debated, RV failure often follows systemic atrioventricular (AV) regurgitation (7,8). Incompetence of the tricuspid valve correlates with excess mortality, with poorer outcomes following AV valve replacement when the pre-operative RV ejection fraction is ≤40% (9). In addition, the AV conduction system is displaced and susceptible to AV block (10,11). Longterm studies report a prevalence of complete AV block of 24–39% (3,12), with an annual incidence estimated to be approximately 2% per year (13). Pacemakers are, therefore, frequently indicated. In the absence of cardiac resynchronization therapy, pacing of the subpulmonary left ventricle can alter the ventricular depolarization pattern thereby precipitating systemic AV valve regurgitation and heart failure (14). This confluence of factors contributes to the risk for ventricular arrhythmias and sudden death (15).

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