Assessment of ventricular desynchronization in patients with repaired tetralogy of Fallot by strain Doppler echocardiography

Background. Several parameters have recently been proposed to assess mechanical dyssynchrony using tissue Doppler / strain Doppler imaging (TDI/SRI). Few data exist regarding the assessment of inter- and intra-ventricular dyssynchrony in patients after tetralogy of Fallot (TOF) repair in the presence of right bundle branch block. Methods. Eleven patients after TOF repair (aged 17-42 years) with dilated right ventricle (NYHA class II or greater), right bundle branch block (QRS >120ms), and RV fractional area change (RVFAC) <20% were studied with TDI/SRI echocardiography before and after biventricular pacing (BP). Intraventricular dyssynchrony was determined as the difference between the longest and shortest electromechanical coupling times in the basal septal and lateral RV segments. Interventricular dyssynchrony was determined as the difference between electromechanical coupling times in the basal lateral LV segment and the most delayed RV segment. Thirteen age-matched healthy subjects were selected as controls. Results. At six months follow-up after BV implantation, patients functional status improved by one NYHA class or more and RVFAC improved overall from 16.22.7% to 27.39.1%. Interventricular dyssynchrony by SRI was reduced from 74.5 +/- 27 ms to 36.1 +/- 21.4 ms (p<0.005) and intraventricular dyssynchrony from 71 +/- 24.2 ms to 25.9 +/- 14.7 ms (p<0.001). TDI/SRI parameters had optimal predictive accuracy of the effects of BP on RV function and a larger area under the receiver operating characteristic curve than the QRS duration. Conclusions. TDI/SRI dyssynchrony measurements show that biventricular pacing results in significant midterm benefit in TOF pts with poor RV function and broad QRS.