Right ventricular myocardial activation delay in adult patients with right bundle branch block late after repair of Tetralogy of Fallot.

Electromechanical interaction, with prolonged QRS duration due to right ventricular (RV) overload, has been described as a predictor of unfavorable outcome in patients late after correction of Tetralogy of Fallot (TOF). Aim of our study was to evaluate myocardial function and activation delay of both left and right ventricles in TOF patients. Doppler echo, treadmill test and pulsed Tissue Doppler (TD) were performed in 25 healthy subjects and in 30 adult patients who had undergone surgery for TOF, all with right bundle branch block on ECG. Exclusion criteria were evidence of residual pulmonary either stenosis or regurgitation. By use of TD, the level of both LV mitral and RV tricuspid annulus were measured: systolic (Sm), early- and late-diastolic (Em and Am) regional peak velocities. The indexes of myocardial systolic activation were calculated: precontraction time (PCTm) and interventricular activation delay (InterV-del) (difference of PCTm between RV and LV segments). The two groups were comparable for LV diameters and for Doppler indexes, while QRS duration was prolonged and RV end-diastolic diameter was increased in TOF. By TD analysis, only at the level of tricuspid annulus TOF patients had lower Sm and Em, and increased RV PCTm ( p<0.001 ) and InterV-del ( p<0.0001 ), even after adjustment for heart rate (HR) and QRS duration. By treadmill test, TOF showed reduced cardiac functional reserve. In seven patients non-sustained ventricular tachycardia was documented during physical effort. By multivariate analysis, RV Em ( p<0.001 ), and InterV-del ( p<0.01 ) were independently associated to maximal workload at peak effort. The same InterV-del was an independent determinant of risk of ventricular arrhythmias during effort ( p<0.01 ). A cut-off point of Em peak velocity of tricuspid annulus <0.13 m/s at rest showed a sensitivity of 91% and a specificity of 88% in identifying TOF patients with submaximal exercise test. A cut-off point of InterV-del >55 ms showed 87% sensitivity and 88% specificity to detect increased risk of ventricular arrhythmias during effort. In TOF patients, TD analysis at rest may be taken into account as a non-invasive and easy-repeatable tool to predict cardiac performance during physical effort, and to select subgroups of patients at increased risk of ventricular arrhythmias.