Functional analysis of the components of the right ventricle in the setting of tetralogy of Fallot.

BACKGROUND

Anatomic and functional observations suggest that the right ventricle (RV) can be analyzed in terms of its inlet, apical trabecular, and outlet components. Our study was designed to evaluate the regional adaptation of these components to different conditions of loading, with additional analysis of the surgical techniques used for primary repair.

METHODS AND

RESULTS

We studied prospectively 45 patients with tetralogy of Fallot (age, 20.5+/-8.1 years) and 24 control subjects (age, 20.1+/-5.8 years). All subjects were studied by using cardiac MRI. End-diastolic (EDV), end-systolic (ESV), stroke volumes (SV), and ejection fraction (EF) were determined for the overall RV and separately for its inlet, apical trabecular, and outlet components. The patients had pulmonary regurgitant fractions of 33.2+/-11.1%, and RV peak-systolic pressures of 40.7+/-16.1 mm Hg. In controls, the apical trabecular component EDV was 51.5+/-11.1 mL/m(2) (54.3+/-6.8% of the total RV EDV), ESV was 19.2+/-6.3 mL/m(2) (47.6+/-10.5% of RV ESV), and SV was 32.3+/-6.9 mL/m(2) (58.9+/-6.6% of RV SV), resulting in an EF of 63.1+/-7.7%. When considering all patients, the apical trabecular component took up the greatest part of the overload, having an EDV of 76.5+/-18.1 mL/m(2), and an ESV of 31.6+/-12.8 mL/m(2), reflecting an increase of 49 and 67% over controls, respectively (P<0.001). EF was 59.7+/-10.7%, and was maintained at control levels (P=0.132). In controls, the outlet had considerable ejecting force, with an EF of 54.8+/-9.1%, whereas it was decreased in the patients with tetralogy (EF=28.5+/-11.9%). There was significant increase of ESV (P<0.001), but not of EDV, with EF decreased by 45% (P<0.001). The inlet was not significantly affected by overload. The surgical technique did not significantly affect any measured parameter for any component.

CONCLUSIONS

In patients with tetralogy of Fallot, subsequent to surgical correction, the individual components of the RV respond in characteristic fashion to RV overload.