Left atrial coupling index and undiagnosed atrial fibrillation in elderly high-risk individuals

Abstract Background Left atrial volumetric/mechanical coupling index (LACi) is a novel measure, which combines information on LA size and function in one variable and may therefore be capable of predicting atrial fibrillation (AF). Its association to undiagnosed AF has not yet been investigated. Purpose We aimed to investigate the association between LACi and undiagnosed AF in an elderly population. Methods This was a substudy based on a large, randomized, clinical trial of elderly population (≥ 70 years), no history with AF, with a CHA2DS2-VASc score≥2 (at least one of the risk factors: DM, hypertension, heart failure or previous stroke). Participants were randomized (1:3) to implantable loop recorder (ILR) screening for AF or usual care. This analysis presents findings for participants randomized to an ILR and with available echocardiographic left atrium (LA) measures (n=1020). LACi was calculated as the ratio of left atrial maximal volume index (LAVI) and mean peak tissue velocity at late diastole measured using tissue Doppler of the left ventricle. The outcome assessed was AF episodes lasting ≥6 minutes and ≥24 hours. Regression models were adjusted for CHARGE-AF, a risk score based on clinical parameters developed to predict risk of AF in the general population. Results A total of 955 individuals were included in the analysis. The mean age was 74 ± 4 years, 44% were female, and median LACi was 3.0 (IQR: 2.3, 3.9). During a median follow-up of 35 (20-40) months, a total of 277 participants were diagnosed with AF. In unadjusted analysis, LACi was significantly associated with both AF ≥6 minutes and ≥24 hours (Figure 1 and 2, respectively). Multivariable regression models adjusted for CHARGE-AF risk score revealed LACi to be independently associated with AF ≥6 minutes (HR 1.16, 95% CI [1.11-1.20], p<0.001, per 1 unit increase) and ≥24 hours (HR 1.14, 95% CI [1.08-1.20], p<0.001, per 1 unit increase). Participants with a LACi above 3.0 had a significantly increased risk of AF ≥6 minutes (HR 1.82 95% CI [1.42-2.33]) and ≥24 hours (HR 2.71 95% CI [1.29-5.26]). Conclusion In elderly high-risk individuals, increasing LACi was significantly associated with incident AF as detected by continuous long-term monitoring.