Echocardiographic evaluation of systolic and diastolic left ventricular function following arterial switch operation in the neonatal period for transposition of the great arteries. Midterm results.

BACKGROUND: Neonatal arterial one-stage switch operation (ASO) for transposition of the great arteries (TGA) is currently the procedure of choice for TGA. There is a potential risk of myocardial damage related to coronary artery reimplantation and sudden pressure overload imposed on the left ventricle after discontinuation of the cardiopulmonary bypass.

OBJECTIVES: This study was carried out in order to evaluate left ventricular systolic and diastolic function in children following ASO.

METHODS: We studied 32 children (22 M, 10 F), mean age 23.7 +/- 24.6 months (range 0.5-97.2) following ASO, without any hemodynamically significant residual stenosis by 2D- and Doppler-echocardiography. Twenty-five had TGA with intact ventricular septum and 7 with ventricular septal defect. Mean age at time of one-stage repair was 8.9 +/- 6.9 days (range 2-30) and the mean time of follow-up 23.5 +/- 24.6 months (range 0.3-96). At the time of evaluation all the children were asymptomatic. Regional wall motion of the left ventricle was assessed by 2D-echo. Volumes, mass index, M/V ratio, afterload, systolic function (FS% and VCFc), contractility (stress-velocity SVI and stress-shortening SSI relations) and preload (functional preload index FPI = SSI-SVI) of the left ventricle were determined by m-mode echo together with non-invasive blood pressure monitoring. Left ventricular diastolic function was determined by PW Doppler of transmitral flow. All parameters were compared with those of 32 normal controls matched for age, sex and body surface area.

RESULTS: Left ventricular regional wall motion was normal in all but 5 cases who showed a slight reduction of the septal systolic motion. Volumes and EF% did not differ in post-ASO group vs controls. There was a small increase of the mass index in the post-ASO group vs controls (62.8 +/- 14.1 vs 56.2 +/- 6.5 g/m2; p = 0.02) and the M/V ratio did not differ. FS% and VCFc were not different between the 2 groups. Peak and end-systolic meridional stress also did not differ in the 2 groups. A normal contractile state was present in the post-ASO group. The preload was slightly reduced in the post-ASO children (FPI -0.6 +/- 0.94 vs 0.07 +/- 0.63; p = 0.001). Parameters of left ventricular diastolic function were not significantly different between the 2 groups.

CONCLUSIONS: In conclusion in children undergoing neonatal ASO for TGA with intact septum or ventricular septal defect, evaluated after a mean post-surgical follow-up of 2 years, systolic and diastolic performance of the left ventricle was normal. Regional wall motion abnormalities with slightly reduced septal motion were detected in 5 cases. The reason for the small increase in mass index is unknown. The slight reduction of the preload is related to the routine drug therapy in the patients studied early after surgical repair.