Abstract 13819: Delayed Enhancement Cardiac Magnetic Resonance Imaging Predicts Response to Cardiac Resynchronization Therapy

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Introduction: Primary predictors of cardiac resynchronization therapy (CRT) are based on conduction system characteristics, such as QRS duration and morphology. The ability of MRI to predict CRT response is less understood. Methods: We studied 83 patients who received cardiac MRI with gadolinium delayed enhancement (DE) prior to CRT. Patients had preCRT EF ≤ 40%, preCRT QRS ≥ 120ms, and paired ~1 year postCRT echocardiograms. MRIs were read without knowledge of patient characteristics or CRT outcomes and echocardiograms were read in a core-lab blinded to MRI results. Results: Patients were classified as having no DE (n=27), only septal midwall DE (n=20), or scar / DE (transmural, subendocardial, or subepicardial) (n=36). Prior to CRT, those with septal midwall DE (25 ± 7) had lower EFs than those with scar / DE (31 ± 6, p=0<0.01), but not statistically different from those without DE (29 ± 6). Those without DE had better (p<0.001) EF (14.2 ± 10 units) and LVESV improvements (-42 ± 21%) following CRT than those with midwall DE (EF: 2.1 ± 9 units; LVESV: -3 ± 35%) or those with scar / DE (EF: 1.4 ± 8 units; LVESV: -5 ± 25%). There was no difference in CRT response between non-ischemics with septal midwall DE and patients with scar / DE. In univariate regression models LBBB tended (p=0.12) to predict a beneficial EF response to CRT while presence of midwall DE was highly significant (p<0.001) for predicting a lack of response in the 47 patients without scar. In a multivariate model including many baseline characteristics, septal midwall DE provided predictive value (p<0.001) for EF response whereas the common predictors of gender (p=0.693) and LBBB (p=0.913) did not. Conclusions: DE cardiac MRI is a good predictor of response to CRT. The absence of any DE predicts a significant improvement in EF and LV volumes. In the idiopathic non-ischemic population the presence of septal midwall DE was a better negative predictor of response than more traditional characteristics of LBBB and gender. In addition, the presence of transmural, subendocardial, or subepicardial scar also predicted lack of improvement in LV function and volumes with CRT. The information obtained from DE MRI could help determine which patients would be best helped by CRT.