Abnormal left atrial body stiffness is predicted by appendage size: impact of appendage occlusion on left atrial mechanics assessed by pressure-volume analysis

Abstract

Atrial cardiomyopathy has been recognized as having important consequences for cardiac performance and clinical outcomes. The pathophysiological role of the left atrial (LA) appendage and the effect of percutaneous left atrial appendage occlusion (LAAO) upon LA mechanics is incompletely understood. We evaluated if changes in LA stiffness due to endocardial LAAO can be detected by LA pressure-volume (PV) analysis and whether stiffness parameters are associated with baseline characteristics. Patients undergoing percutaneous endocardial LAAO (N = 25) were studied using a novel PV analysis using near-simultaneous 3D LA volume measurements by transesophageal echocardiography (TEE) and direct invasive LA pressure measurements. LA stiffness (dP/dV, change in pressure with change in volume) was calculated before and after LAAO. Overall LA stiffness significantly increased after LAAO compared to baseline (median, 0.41 to 0.64 mm Hg/mL; p <<0.001). LA body stiffness after LAAO correlated with baseline LA appendage size by indexed maximum depth (Spearman's rank correlation coefficient Rs = 0.61; p <0.01). LA stiffness change showed an even stronger correlation with baseline LA appendage size by indexed maximum depth (Rs = 0.70; p <0.001). We found that overall LA stiffness increases after endocardial LAAO. Baseline LA appendage size correlates with the magnitude of increase as well as LA body stiffness. These findings document alteration of LA mechanics after endocardial LAAO and suggest that the LA appendage modulates overall LA compliance.

Linkage of Left Atrial Function to Heart Failure with Preserved Ejection Fraction

“…Stiff LA syndrome is known to be caused by the loss of LA compliance, characterized by LA diastolic dysfunction and associated pulmonary hypertension. [49][50][51][52] The normal LA dilates during exercise to augment reservoir function and receives greater venous return from pulmonary veins, protecting the lung capillaries from barotrauma. However, in stiff LA syndrome, atrial and pulmonary venous pressure increases dramatically as the atrium fills to the steeper portion of its compliance curve, leading to the development of so-called "giant V waves" found in pulmonary capillary wedge pressure waveforms.…”