Left atrial total emptying fraction is the main predictor of atrial fibrillation in patients with hypertrophic cardiomyopathy

Background Given the negative impact of atrial fibrillation (AF) in patients (pts) with hypertrophic cardiomyopathy (HCM), finding new and better predictors of AF occurrence is clinically important. Over time, numerous parameters have been tested in this regard, but a systematic comparison of them has not been provided. Purpose We aimed to identify predictors of new-onset AF in a cohort of HCM patients comprehensively assessed at rest and during stress echocardiography. Methods We prospectively evaluated 52 consecutive patients diagnosed with HCM (mean age 50 ± 16 years; 31 males), in sinus rhythm and with no prior history of AF. Each participant underwent a comprehensive transthoracic echocardiogram. The following parameters were assessed: maximal and minimal indexed left atrial volumes (LAVi max and LAVi min), total left atrial emptying fraction (LAEF, calculated as (LAVi max-LAVi min)/LAVi max), maximal left ventricular wall thickness (LVWT), left ventricular ejection fraction (LVEF), and the left atrioventricular coupling index (LACI, defined as the ratio between LAVi min and LV end-diastolic volume). Additionally, global longitudinal LV strain (GLS), LA strain (LASr, LAScd, LASct), E/e′ ratio, and the left atrial stiffness index (LASI, calculated as E/e′ divided by LASr), peak LV outflow tract gradient (LVOT G) and mitral regurgitation (MR) severity were assessed at rest (r) and during exercise (e). All patients were monitored for new-onset AF using 24- to 48-hour ambulatory ECG recordings during follow-up. Results During a median follow-up of 29 (6–155) months, 13.5 % patients developed AF. rE/e’ (19 ± 7.3 vs 14 ± 4.5, p=0.03), eE/e’ (24 ± 13.4 vs 14 ± 4.5, p=0.001), LACI (1.3 ± 0.6 vs 0.6 ± 0.2, p<0.0001), rLASI (1.3 ± 0.7 vs 0.5 ± 0.3, p<0.0001), eLASI (1.8 ± 1.4 vs 0.5 ± 0.4, p<0.0001) were significantly higher, while rLASr (17 ± 6.9 vs 34 ± 11, p<0.0001), eLASr (19 ± 10.2 vs 32 ± 14.3, p=0.03) and LAEF (31 ± 12.6 vs 50 ± 9.7, p<0.0001) were significantly lower in pts with AF compared to pts without AF. There were no significant differences between pts with and without AF regarding: age, LVWT, rGLS, eGLS, LAVi, rLVOT G, eLVOT G, rMR, eMR (p>0.05 for all). Multivariable Cox regression analysis showed LAEF (≤48 %; HR, 0.81; 95% CI, 0.715–0.922; p=0.001) as independent AF predictor. Patients with LAEF >48% versus ≤48% had superior 5-year AF-free survival of 100% versus 64% (p=0.006). Conclusions Patients with new-onset AF had lower LA emptying fraction and LA reservoir strain and higher LA stiffness and LV filling pressures both at rest and during exercise. While LA reservoir strain is a well-established marker strongly associated with new-onset AF, our findings highlight that total left atrial emptying fraction (LAEF)—a simpler and more accessible parameter that also reflects reservoir function—emerged as the strongest independent predictor of new-onset AF.