Left atrial structure and function in atrial fibrillation: ENGAGE AF-TIMI 48

Abstract

Aims: The complex relationship between left atrial (LA) structure and function, electrical burden of atrial fibrillation (AF) and stroke risk is not well understood. We aimed to describe LA structure and function in AF.

Methods and results: Left atrial structure and function was assessed in 971 subjects enrolled in the echocardiographic substudy of ENGAGE AF-TIMI 48. Left atrial size, emptying fraction (LAEF), and contractile function were compared across AF types (paroxysmal, persistent, or permanent) and CHADS2 scores as an estimate of stroke risk. The majority of AF patients (55%) had both LA enlargement and reduced LAEF, with an inverse relationship between LA size and LAEF (R = -0.57, P < 0.001). With an increasing electrical burden of AF and higher CHADS2 scores, LA size increased and LAEF declined. Moreover, 19% of AF subjects had impaired LAEF despite normal LA size, and LA contractile dysfunction was present even among the subset of AF subjects in sinus rhythm at the time of echocardiography.

Conclusions: In a contemporary AF population, LA structure and function were increasingly abnormal with a greater electrical burden of AF and higher stroke risk estimated by the CHADS2 score. Moreover, LA dysfunction was present despite normal LA size and sinus rhythm, suggesting that the assessment of LA function may add important incremental information in the evaluation of AF patients.

Clinical trial registration: http://www.clinicaltrials.gov; ID = NCT00781391.

Keywords: Atrial fibrillation; ENGAGE AF-TIMI 48; Echocardiography; Left atrium; Stroke.

Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2013. For permissions please email: journals.permissions@oup.com.

Figures

Figure 1

The relationship between left atrial emptying fraction and left atrial volume index. (A) Left atrial emptying fraction was inversely correlated with left atrial size. Left atrial size was normal (LAVI <29 mL/m2) in 36% of all atrial fibrillation patients and 17% had both normal left atrial size and left atrial emptying fraction (>45%). (B) The inverse relationship between left atrial emptying fraction and left atrial size was similar between subjects in sinus rhythm (n = 321) and atrial fibrillation (n = 650) at the time of echocardiography.

Figure 2

Left atrial size and function according to type of atrial fibrillation. (A) Left atrial size measured by the volume index significantly increased. (B) Left atrial emptying fraction significantly declined. (C) The left atrial expansion index, a measure of reservoir function and left atrial compliance, significantly declined. (D) Among those in sinus rhythm at the time of echocardiography, left atrial contractile function, assessed by tissue Doppler imaging A′ velocities, was lowest in those with permanent atrial fibrillation.

Figure 3

Relationship between left atrial size and function according to type of atrial fibrillation and stroke risk expressed in the CHADS2 score. (A) Increasing left atrial size, measured by left atrial volume index, appears more strongly related to type of atrial fibrillation (P < 0.001) than to stroke risk expressed in the CHADS2 score (P = 0.007). (B) Worsening left atrial emptying fraction appears more strongly related to type of atrial fibrillation (P < 0.001), than to the CHADS2 score (P = 0.041).