Characterizing left atrial failure via the booster preload-performance relationship

Background

Left 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 remain poorly defined.

Objectives

To characterize LA booster function using cardiac computed tomography angiography (CCTA) and to evaluate the relationship between LA preload, booster performance, remodeling, and clinical outcomes.

Methods

We 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.

Results

LA 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 (Figure 1). Booster volume was associated with reservoir volume (r=0.77, p<0.001) indicating that impaired booster function is associated with impaired reservoir function.

Based on the LA pre-A volume and the LA booster volume, 4 different groups were created: Group 1 (LAVpre-A < 110 mL and LA booster volume < 25 mL), Group 2 (LAVpre-A < 110 mL and LA booster volume ≥ 25 mL) the reference group, Group 3 of patients with appropriate booster response to the increased booster preload (LAVpre-A ≥ 110 mL and LA booster volume ≥ 25 mL) consistent with appropriate response to increased preload, and Group 4 of patients with reduced booster function despite increased booster preload (LAVpre-A ≥ 110 mL and LA booster volume < 25 mL), indicating LA failure (Figure 1).

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 (Figure 2).

Conclusions

LA 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.Pre-A wave volume and atrial kick volumeKM estimates of the combined endpoint