Left atrial strain predicts subclinical atrial fibrillation detected by long-term continuous rhythm monitoring in elderly high-risk individuals
Authors: Olsen FJ , Diederichsen SZ , Jorgensen PG , Jensen MT , Dahl A , Landler NE , Haugan KJ , Kober L , Hojberg S , Svendsen JH , Biering-Sorensen T 
Published: February 2021

Abstract

Funding Acknowledgements
Type of funding sources: Foundation. Main funding source(s): he Innovation Fund Denmark (grant no.: 12-135225), The Research Foundation for the Capital Region of Denmark, The Danish Heart Foundation (grant no.: 11-04-R83-A3363-22625 and 18-R125-A8534-22083), Aalborg University Talent Management Programme, Arvid Nilssons Fond, Skibsreder Per Henriksen, R. og Hustrus Fond, and Medtronic

Background
Left atrial (LA) speckle tracking is a novel technique that provides detailed information on atrial function. Its utility for predicting subclinical atrial fibrillation (SCAF) is, however, not well-established.
Purpose
To investigate whether LA speckle tracking measures are associated with SCAF as detected by long-term continuous rhythm monitoring.

Methods
This was an echocardiographic substudy of a randomized controlled clinical trial that enrolled elderly individuals (≥70 years) with a CHADS2-score≥2 to either no intervention or implantation of a loop recorder (Reveal LINQ) to detect SCAF (≥6 minutes). A subset of the participants receiving a loop recorder was included in this analysis. An echocardiographic examination was performed, which included conventional measurements and LA speckle tracking. LA speckle tracking allowed for assessment of reservoir, conduit, and contraction strain. Multivariable proportional hazards Cox regression was applied to adjust for the clinical risk score (CHARGE-AF) and net reclassification index (NRI) was used to assess prognostic improvement of this score. Incidence rate curves were constructed using Poisson models.
Results
Overall, 976 participants were eligible for analysis. Median follow-up time was 3 years (interquartile range: 1.7-4.0 years), during which 284 (29%) were diagnosed with SCAF. The mean age was 74 years, 56% were male, median CHA2DS2-VASc-score was 4. A dilated LA (LA volume≥34ml/m2) was observed in 152 (16%).
LA speckle tracking revealed that both LA reservoir strain and contraction strain were univariable predictors of SCAF (HR = 1.05 (1.03-1.06) and HR = 1.07 (1.05-1.10), p &lt; 0.001, per 1% decrease), such that decreasing reservoir and contraction strain were linearly associated with an increased risk of SCAF (figure). LA conduit strain was not a predictor of SCAF. These findings were unchanged after adjusting for the CHARGE-AF score, and both LA strain measures significantly improved the NRI when added to the CHARGE-AF score by 23% and 33%, respectively.
Even in participants with normal LA size, both reservoir and contraction strain were independent predictors of SCAF after multivariable adjustment (HR = 1.03 (1.01-1.05), p = 0.001 and HR = 1.06 (1.04-1.09), p &lt; 0.001, per 1% decrease).

Conclusion
Decreasing left atrial reservoir and contraction strain are independently associated with an increased risk of SCAF as detected by long-term continuous monitoring and provide incremental prognostic value in addition to clinical risk score.
Abstract Figure.