Left atrial hyper-strain in dyssynchronous hearts: potential driver for adverse left atrial remodelling

Abstract Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): Institute for Surgical Research, Oslo University Hospital. Introduction It was recently shown that left bundle branch block (LBBB) is associated with risk of developing atrial fibrillation. A potential mechanism is abnormal left atrial (LA) loading caused by LA dyssynchrony. Purpose To investigate if LBBB is associated with abnormal LA loading as reflected in non-uniform segmental strains. Methods In a prospective study of 143 heart failure patients with LBBB, myocardial strain was measured by speckle-tracking echocardiography prior to and after 7±2 months on cardiac resynchronization therapy (CRT). As indicated by brackets in the lower panels in the Figure, LA strain amplitudes were calculated as the difference between minimum and peak strain during the reservoir phase. Results In the Figure, the upper panel shows segmental and average LA strain traces in a representative LBBB patient. This patient illustrates marked spatial non-uniformity in strain amplitude between the interatrial septum and the LA lateral wall during the reservoir phase. For the entire study population, strain amplitudes were 19±9% (mean±SD) for the interatrial septum and 24±11% for the LA lateral wall (p<0.0001). In the quartile of patients with largest differences, strain amplitudes were 16±9 and 32±12%, respectively (p<0.0001). CRT abolished these differences (p = NS). Conclusions Patients with LBBB showed marked spatial non-uniformity of LA strains. Potentially, the excessive LA lateral wall strain amplitudes may stimulate atrial adverse remodelling. Future studies should investigate if abnormal LA strains may be a trigger mechanism for atrial fibrillation in patients with LBBB.