Giselle Y. Revah MD, Presenter: Nothing to Disclose

Vincent Wu BS, Abstract Co-Author: Nothing to Disclose

James S. Babb PhD, Abstract Co-Author: Nothing to Disclose

Janice Chyou, Abstract Co-Author: Nothing to Disclose

Leon Axel MD, PhD, Abstract Co-Author: Nothing to Disclose

There is scant information about MRI of mechanical features of left bundle branch block (LBBB). Several findings have been described in the echo literature, including: septal flash (SF), early inward motion followed by outward motion of the septum once the lateral wall begins to contract; apical rocking (AR), abnormal motion of the left ventricular (LV) apex perpendicular to the LV long axis; delayed opening of the aortic valve; and delayed lateral wall contraction. This study aims to assess the MRI features of LBBB.  

We retrospectively identified cardiac MRIs from 43 patients with LBBB on EKG and 43 age and gender matched controls. Two cardiac radiologists assessed the MRIs for the presence of SF, AR and timing of lateral wall contraction. Timing of aortic valve opening was assessed on phase-contrast velocity flow maps and three different conventional cine planes.  

According to Fisher’s exact test, LBBB was significantly associated with SF and AR (p<0.0001). Since SF and AR were seen exclusively in LBBB, they showed 100% specificities and PPVs for LBBB. Using logistic regression, the delayed timing of both the lateral wall contraction and the aortic valve opening as compared to controls were significant predictors of LBBB (p<0.0001). The timing of aortic valve opening assessed on phase-contrast images had the best sensitivity (86%) and specificity (100%) in predicting LBBB, compared to conventional cine images. Among LBBB patients, 79.1% (34/43) had SF. Ejection fraction (EF) was a significant predictor of SF (p=0.041, OR= 0.93) but QRS duration was not a significant predictor of SF (p=0.437). EF was also a significant predictor of delayed opening of the aortic valve (p=0.041), in patients with LBBB. Inter-reader agreement was assessed by kappa (κ) coefficients, which showed concordant opinions between the readers in identifying SF (κ=1.0) and AR (κ=0.55).  There was good inter-reader agreement in timing measurements of delayed aortic valve opening on phase-contrast (ICC = 0.90) and 3 chamber cine SSFP (ICC =0.88).  

MRI can be used as an adjunct to EKG to assess patients with mechanical dyssynchrony. SF, AR and delayed opening of the aortic valve are highly specific predictors of LBBB that can reliably be detected by MRI. 

MRI can act as an adjunct to EKG and identify patients with mechanical dyssynchrony (LBBB), who may benefit from resynchronization therapy.

Revah, G, Wu, V, Babb, J, Chyou, J, Axel, L, Can MRI Be Used to Assess Mechanical Dyssynchrony? The Features of Left Bundle Branch Block on MRI.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14004633.html