Left atrial strain and the risk of arrhythmias on extended ambulatory cardiac monitoring: the Multi-Ethnic Study of Atherosclerosis

Background: Abnormalities in left atrial (LA) function can be identified before the development of overt LA structural changes. Little is known about the relationship between LA function and the risk of subclinical atrial and ventricular arrhythmias.Methods: 1,441 participants of the Multi-Ethnic Study of Atherosclerosis completed speckle-tracking echocardiography and cardiac monitoring during 2016-2018 (mean age 73 years, 52% female); participants in atrial fibrillation (AF) during echocardiography or during the entire cardiac monitoring period were excluded. Absolute values of LA reservoir, booster pump, and conduit strain were measured. We evaluated associations of LA strain with atrial arrhythmias (monitor-detected AF, premature atrial contractions [PACs], supraventricular tachycardia [SVT]) and with ventricular arrhythmias (premature ventricular contractions, non-sustained ventricular tachycardia [NSVT]). Primary analyses adjusted for demographics, blood pressure, smoking, diabetes, and clinical cardiovascular disease. Results: Cardiac monitoring (median 14 days) detected AF in 3%. Each standard deviation (4.0 %-units) lower LA booster pump strain was associated with 84% higher risk of monitor-detected AF (95% CI 30-162%), 39% higher PAC frequency (95% CI 27-53%), and 19% higher SVT frequency (95% CI 10-29%). Additional adjustment for kidney function, NT-proBNP, LA volume, tissue Doppler a’ peak velocity, left ventricular (LV) ejection fraction, and global longitudinal strain had little impact on associations. Findings were similar for LA reservoir strain and null for LA conduit strain. Associations of LA booster pump and reservoir strains with ventricular arrhythmias were completely attenuated after adjustment for LV structure and function. Conclusions: In a multi-ethnic cohort, impaired LA strain was an important correlate of subclinical atrial arrhythmias, even after adjustment for echocardiographic measures of LA structure and function.