Radionuclide evaluation of right ventricular wall motion after surgery in tetralogy of Fallot

Regional wall motion patterns in tetralogy of Fallot and its postoperative modifications by electrical and hemodynamic factors were assessed by Fourier analysis of gated radionuclide angiograms in 24 studies performed in children after surgical correction of tetralogy of Fallot. The range of right ventricular (RV) phase angles (standard deviation of the peak [SDP] of RV) as well as the difference between RV and LV (delta MPh) were used as indices of the synchronicity of wall motion and were correlated with RV apical electrical activation time determined by endocardial electrical mapping. Postoperative studies were divided into two groups according to apical activation: (a) those involving right bundle branch block (RBBB) (nine patients), and (b) those involving distal RBBB (15 patients). delta MPh was longer in proximal than in distal RBBB. Best discrimination between the two groups was obtained with SDP of RV (proximal = 24 degrees +/- 3 degrees, and distal = 17 degrees +/- 2 degrees; p less than 0.0001). These results showed that the range of ventricular phases measured by the SD of the phase distribution of the right ventricle is a good index for distinguishing between proximal and distal RBBB after cardiac surgery.