Synergistic interaction between right ventricular mechanical dyssynchrony and pulmonary regurgitation determines early outcome following tetralogy of Fallot repair.

OBJECTIVE The ability of the right ventricle to tolerate acute pulmonary regurgitation (PR) following tetralogy of Fallot (TOF) repair is variable and the mechanisms that underlie this are not completely understood. We hypothesise that dyssynchronous wall mechanics affects the RV tolerance to postoperative PR with adverse effect on early surgical outcome. METHODS Twenty-four TOFs (mean age 19.5+/-15.5 months) undergoing elective repair were prospectively recruited. Ventricular wall mechanics was studied by tissue Doppler echocardiography following induction (preop) and postoperative day one (POD1) and compared with a control group (10 VSD/AVSD). Segmental dyssynchrony, defined as out-of-phase peak myocardial contraction, was determined at the base, mid, apical segments of the septum, RV and LV free walls and scored by the total number of affected segments. PR was graded from absent to severe and RV dimension was quantified by end-diastolic area index (RVEDAI). Cardiac index (CI) was measured by pulse contour cardiac output analysis. Outcome measures were CI, mixed venous oxygen saturation (SvO2), lactate, and duration of ventilation and critical care stay. RESULTS Preoperatively, biventricular free-wall motion was synchronous in both groups. Following surgery, TOF developed RV-septal dyssynchrony (>2 segments in 11 (46%) vs none in control, p=0.01), while the LV free wall remained normal in both groups. RV-septal dyssynchrony correlated with the ventilation time (rho=0.69, p=0.003), critical care stay (rho=0.58, p=0.02) in the presence of PR (n=16), but not with other outcome measures. The relationships between dyssynchrony and early outcome were not seen when PR was absent. In the presence of PR, median RVEDAI was greater with higher dyssynchrony score (>3 segments; p=0.009). The degree of PR did not affect critical care/ventilation time or RVEDAI. The presence of transannular patch (p=0.007) or at least moderate PR (p=0.01) was associated with a more severe dyssynchrony. CONCLUSIONS Dyssynchronous RV-septal wall mechanics occurs early after Fallot repair. The magnitude of dyssynchrony appears to interact synergistically with pulmonary regurgitation to influence RV dimension and early outcome.