Optimization of myocardial strain imaging and speckle tracking for resynchronization after congenital heart surgery in children

Cardiac resynchronization therapy can improve cardiac function in children with heart failure. The optimal method of assessing dyssynchrony has not been established. Newer tissue Doppler techniques such as strain assessment and speckle tracking appear to be promising for optimization of resynchronization. Two children aged 7 weeks and 4 months, with transposition of the great arteries and ventricular septal defect, and double outlet right ventricle with pulmonary stenosis, developed heart block after surgery. Conventional epicardial pacing resulted in heart failure in both. Upgrade to cardiac resynchronization therapy was not associated with normalization of function by echo, necessitating optimization. Baseline ventriculo-ventricular delay was 4 ms. Speckle tracking strain assessment was performed while adjusting ventriculo-ventricular delay. In Patient 1, synchrony was best with left ventricular (LV) activation preceding right ventricular (RV) by 30 ms. In Patient 2, it was best with RV preceding LV by 20 ms. At follow-up, both patients had normalization of function. In each case, optimization and reprogramming could be done live with no need for offline analysis. Speckle tracking strain analysis appears to be successful in the live, on-site optimization of cardiac resynchronization therapy in children. Further studies may help refine this process further.