MYOCARDIAL PERFUSION DEFECTS AND ASSOCIATED SYSTEMIC VENTRICULAR DYSFUNCTION IN CONGENITALLY CORRECTED TRANSPOSITION OF THE GREAT-ARTERIES

Background-Patients with systemic ventricles of right ventricular morp hology ape at high risk of contractile dysfunction, the cause of which has not been fully elucidated, Objective-To assess whether ischaemia or infarction contributes to ventricular impairment in unoperated pati ents with uncomplicated congenitally corrected transposition of the gr eat arteries (TGA) by studying myocardial perfusion and function, Sett ing-Paediatric and and adult congenital cardiac clinics of a tertiary referral centre. Patients-Five patients with congenitally corrected TG A hut without associated structural cardiac defects (aged 3.5 to 34 ye ars). Interventions-Maximal exercise stress testing using standard or modified Bruce protocols. Sestamibi (technetium-99m methoxy isobutyl i sonitrile) scanning after isotope injection at maximal exercise and re st. Main outcome measures-Maximum exercise capacity; right ventricular myocardial perfusion, regional wall motion, and thickening; right ven tricular ejection fraction. Results-The two youngest patients (3.5 and 11 years) had normal exercise capacity for age, while the others had reduced exercise performance. Sestamibi scanning showed reversible myo cardial ischaemia in four patients and fixed defects indicating infarc tion in five. irreversible defects were mostly associated with impaire d wall motion and thickening. The ejection fraction was normal (65%) i n the youngest patient but < 55% in the others (mean (SD) 47(11)%). Co nclusions-Patients with unoperated congenitally corrected TGA have a h igh prevalence of myocardial perfusion defects, with consequent abnorm alities of regional wall motion and thickening, and impaired ventricul ar contractility. These data suggest that ischaemia and infarction are important in the pathogenesis of ventricular failure in this conditio n.