Background
Anatomical considerations suggest the supraventricular crest (SC) is important for right ventricular free-wall to septum (RV FW-S) inward motion and may importantly influence overall right ventricular (RV) function. The influence of approximation of the FW-S on overall RV function, and implicitly the importance of the SC, may be judged from patients with repaired tetralogy of Fallot (rToF), where the components of this muscular bridge are separated.

Methods
RV functional parameters were determined from magnetic resonance imaging (CMR) and related to RV FW-S approximation in 106 rToF patients, compared to CMR parameters in 30 normal subjects and with echocardiography in another 39 normal subjects.

Results
In normal subjects, the SC shortened 41 ± 5% during systole and basal FW-S distance shortened significantly more than mid-ventricular FW-S distance (47 ± 17% vs. 23 ± 12%; p < 0.05). In rToF patients, resection of SC resulted in a divided muscular bridge in 42.5%. Resection of SC was associated with lowered basal FW-S approximation (21 ± 13% vs. 39 ± 9%; both p < 0.0001) and lower RVEF (45 ± 8% vs. 54 ± 8% both p < 0.0001). Even if a muscular bridge was present, basal RV FW-S shortening in rToF patients was correlated with relative shortening of the SC (r = 0.61; P < 0.0001) and with RVEF (r = 0.42; p < 0.0001). There was no association between resection of SC and RV diastolic volumes or regurgitation fractions of the pulmonary or tricuspid valves.

Conclusions
As demonstrated in rToF patients, the basal right ventricular free-wall-to-septum approximation is of importance for overall RV function. Our finding suggests that the supraventricular crest secures this function.