Myocardial perfusion defects and associated systemic ventricular dysfunction in congenitally corrected transposition of the great arteries

Abstract

Background: Patients with systemic ventricles of right ventricular morphology are 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 patients with uncomplicated congenitally corrected transposition of the great arteries (TGA) by studying myocardial perfusion and function.

Setting: Paediatric and adult congenital cardiac clinics of a tertiary referral centre.

Patients: Five patients with congenitally corrected TGA but without associated structural cardiac defects (aged 3.5 to 34 years).

Interventions: Maximal exercise stress testing using standard or modified Bruce protocols. Sestamibi (technetium-99m methoxy isobutyl isonitrile) scanning after isotope injection at maximal exercise and rest.

Main outcome measures: Maximum exercise capacity; right ventricular myocardial perfusion, regional wall motion, and thickening; right ventricular 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 myocardial ischaemia in four patients and fixed defects indicating infarction in five. Irreversible defects were mostly associated with impaired wall motion and thickening. The ejection fraction was normal (65%) in the youngest patient but < 55% in the others (mean (SD) 47(11)%).

Conclusions: Patients with unoperated congenitally corrected TGA have a high prevalence of myocardial perfusion defects, with consequent abnormalities of regional wall motion and thickening, and impaired ventricular contractility. These data suggest that ischaemia and infarction are important in the pathogenesis of ventricular failure in this condition.

Figures

Figure 1

Standardised right ventricular perfusion images used for segmental analysis in patients with congenitally corrected TGA. (A) Transaxial (cross sectional) view. (B) Vertical long axis view. (C) Horizontal long axis view. S, septum; An, anterior wall; L, lateral wall; I, inferior wall; Ap, apex.

Figure 2

Sestamibi scan of patient 5 showing a fixed defect (indicating infarction) in the anterior wall (small arrowheads) and reversible ischaemia in the septum (large arrowhead). Transaxial views at mid-ventricular to basal level at (A) stress and (B) rest. Vertical long axis views at (C) stress and (D) rest. Horizontal long axis views at stress (E) and rest (F).(Refer to fig 1 for diagram of standard views).

Figure 3

Angiograms of a (non-study) patient with congenitally corrected TGA. (A) Late phase aortogram (left anterior oblique view) showing inverted coronary artery pattern with sparse coronary supply to the right ventricle. (B) Right ventriculogram (left anterior oblique view) showing gross hypertrophy and trabeculation, especially of the apical half of the ventricle.