Combined identification of septal flash and absence of myocardial scar by cardiac magnetic resonance imaging improves prediction of response to cardiac resynchronization therapy.

BACKGROUND AND AIMS OF STUDY: Septal flash (SF) describes early inward motion of the ventricular septum in patients with left bundle branch block (LBBB), and correction corresponds to increased response to cardiac resynchronization therapy (CRT). SF has traditionally been assessed by echocardiography. We sought to determine if cardiac magnetic resonance (CMR) imaging could identify SF and if the additional assessment of scar would improve the ability of CMR to predict CRT response.
METHODS: Fifty-two patients with LBBB and heart failure underwent prospective CMR scanning prior to CRT implantation. The presence of SF was assessed visually and by using endocardial contour-tracking software. Presence and extent of myocardial scar was assessed by delayed enhancement imaging during CMR. The association between SF, scar and reverse remodelling (RR) at 6 months was explored.
RESULTS: RR rate to CRT at 6 months was 52%. CMR-derived SF was identified in 24 (46%) patients. RR was seen in more patients with SF than those without (88% vs 21%; P < 0.001). The absence of scar combined with the presence of SF had 96% specificity for predicting RR. In a multivariate regression model, the presence of SF was the only independent predictor of RR.
CONCLUSION: SF can be assessed by CMR and predicts increased response to CRT. The additional value of CMR is the assessment of scar. The presence of SF with no scar is a highly specific predictor of CRT response.