The Impact Of Left Atrial Appendage Ablation And Exclusion On Left Atrial Function
Ali J. Khiabani, Alessandro Montecalvo, Joshua L. Manghelli, Richard B. Schuessler, Marc R. Moon, Ralph J. Damiano, Jr.
Washington University School of Medicine, St. Louis, MO, USA.
BACKGROUND: Left atrial (LA) function is divided into three integrated phases: reservoir, conduit and booster pump. The left atrial appendage (LAA) is the source of most emboli in patients with atrial fibrillation (AF), and its exclusion is an integral component of most surgical ablation strategies. In this study, canine LA function and its contribution to left ventricular (LV) filling was assessed following LAA ablation and subsequent exclusion. METHODS: Ten canines underwent sternotomy. Continuous LA and LV pressure-volume (PV) measurements were obtained using separate conductance catheters. A bipolar ablation clamp (AtriCure, Inc, Cincinnati, OH) was used to electrically isolate the LAA. A clip (AtriCure, Inc, Cincinnati, OH) was then used to mechanically exclude the LAA. Baseline, post-ablation, and post-clip LA and LV PV loops were analyzed to determine LA function. RESULTS: LA booster pump function was significantly reduced following LAA ablation (25% ± 18% vs 10% ± 8%, p = 0.02) (Figure). No further reduction of booster pump function was seen following LAA exclusion (10% ± 8% vs 10% ± 6%, p = 0.86). There were no significant changes in LA conduit and reservoir functions after LAA ablation. However, following LAA exclusion, conduit function was significantly increased (31% ± 14% vs 44% ± 21%, p = 0.04), while reservoir function was significantly reduced (59% ± 13% vs 46% ± 22%, p = 0.03). The slope of the LA end-systolic pressure-volume relationship (LAESPVR) was used as an index of atrial contractility. There was no change in the LAESPVR following LAA ablation (1.89 ± 0.62 mmHg/mL vs 1.75 ± 0.91 mmHg/mL, p = 0.71) and exclusion (1.75 ± 0.91 mmHg/mL vs 2.10 ± 0.80 mmHg/mL, p = 0.40). CONCLUSIONS: Electrical and/or mechanical isolation of LAA caused a significant reduction in LA booster pump function. This is most likely secondary to the loss of LAA contraction. Conduit function increased while the reservoir function decreased following LAA exclusion, but not following ablation alone. This is most likely explained by the loss of both the more compliant LAA tissue and volume. Despite the decrease in booster pump and reservoir functions, the overall LA contractility remained unchanged. "LEGEND:" Figure. Left atrial contribution to left ventricular filling following left atrial appendage ablation and left atrial appendage exclusion. LAA, left atrial appendage; LV, left ventricle; LABPV, percent contribution of left atrial booster pump volume to left ventricular stroke volume; LACV, percent contribution of left atrial conduit volume to left ventricular stroke volume; LARV, percent contribution of left atrial reservoir volume to left ventricular stroke volume.
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