Characterizing Left Atrial Failure via the Atrial Booster Preload-Performance Relationship

BackgroundLeft atrial (LA) remodeling, a hallmark of chronically elevated LA pressure, is characterized by enlargement and functional impairment. While global and reservoir LA functions are well described, the role of LA booster function and its failure remains poorly defined. ObjectivesTo characterize LA booster function using cardiac computed tomography angiography (CCTA) and to evaluate the relationship between LA preload, booster performance, remodeling, and clinical outcomes. MethodsWe retrospectively analyzed 975 patients who underwent spiral CCTA between 2010 and 2018. Phasic LA and LV volumes were obtained, from which LA reservoir and booster functions were derived. LA performance curve was constructed by plotting LA pre-A volume (preload) against LA booster stroke volume. Clinical outcomes (heart failure, stroke, or cardiovascular death) were analyzed based on the LA performance curve. ResultsLA pre-A volume strongly correlated with LA end-systolic volume (r=0.92, p<0.001). The LA booster stroke volume displayed an inverted U-shaped relation to LA pre-A volume (linear coefficient 0.64, P<0.0001; squared coefficient-0.0029, P<0.0001). The atrial booster function curve reached its vertex at 107 mL (95% CI 90 to 113 mL), indicating that the booster pump response for the increased preload is exhausted at this point. Booster dysfunction was associated with impaired reservoir function (r=0.77, p<0.001) and reduced LA systolic flow rates (-0.79, P<0.001). Patients with increased LA pre-A volume but reduced booster volume ("LA failure") exhibited the highest event rate of the combined endpoint of heart failure, stroke or cardiovascular mortality (43.2%, 95% CI 33.6-54.2%). ConclusionsLA enlargement predominantly serves to increase LA pre-A volume to sustain booster function. LA contractile dysfunction affects global LA function via a concomitant reduction in LA reservoir volume. LA failure can be defined as reduced booster contraction despite elevated preload, portending poor clinical outcomes.