Aims: Late after surgical repair, adults with Tetralogy of Fallot (TOF) commonly present with right ventricular (RV) dysfunction and right bundle branch block (RBBB). We aimed at (i) investigating whether this prolonged RV conduction induced detrimental electromechanical dyssynchrony in both RV and left ventricle (LV) and (ii) determining the acute haemodynamic effects of pacing at different RV sites.
Methods and results: A total of 42 adults with surgically repaired TOF and RBBB were investigated by echocardiography. Intra-RV dyssynchrony (IRVD) and intra-left ventricular dyssynchrony (ILVD) were compared with measurements performed in 30 healthy matched control subjects. An acute haemodynamic study was subsequently performed in a subgroup of 10 patients with New York Heart Association functional class II or class III and echocardiographic signs of RV dysfunction. Cardiac index was measured by a thermodilution technique during spontaneous rhythm (SR) and during atrio-synchronized RV pacing at four different sites (infundibulum, apex, septal, and lateral walls). Fifty-five per cent of the patients with repaired TOF demonstrated abnormal RV and/or LV dyssynchrony. We observed an increased IRVD (37 +/- 12 vs. 18 +/- 8 ms; P= 0.02) and ILVD (34 +/- 12 vs. 20 +/- 10 ms; P= 0.04) in TOF patients when compared with control subjects. We did not observe any significant acute improvement in the cardiac output during atrio-synchronized ventricular pacing vs. SR. Similarly, RV pacing did not induce any significant reduction in the QRS duration.
Conclusion: Some TOF adults with RBBB exhibit biventricular electromechanical dyssynchrony. However, in symptomatic patients with RV dysfunction, atrio-synchronized RV pacing does not induce significant acute haemodynamic improvement.