Correlation between left atrium fractal dimension and cardiac function in patients with atrial fibrillation

Objective To investigate the correlation between left atrial (LA) morphology and left ventricular (LV) systolic function in patients with atrial fibrillation (AF). Methods We studied 1066 patients admitted to our institution between December 2018 and December 2022 for AF. All patients underwent cardiac computed tomography angiography (CTA) and transthoracic echocardiography. LV systolic function was assessed using transthoracic echocardiography. On cardiac CTA images, we measured the LA diameter (LAD) and quantified LA morphology using the fractal dimension (FD). The primary focus was association between the novel LA FD and LV systolic function, while LAD was included as a conventional comparator. Results Correlation analysis showed that LAD was negatively associated with the ejection fraction (EF) (r=-0.175, P < 0.001) and fractional shortening (FS) (r=-0.172, P < 0.001) and positively associated with end-systolic volume (ESV) (r = 0.090, P = 0.003). LA FD was negatively correlated with the EF (r=-0.092, P = 0.003) and FS (r=-0.083, P = 0.007) and positively correlated with end-diastolic volume (EDV) (r = 0.086, P = 0.005) and ESV (r = 0.094, P = 0.002). The restricted cubic spline (RCS) curves with four knots demonstrated a nonlinear correlation between LA FD and ESV (overall P = 0.046, nonlinear P = 0.035) and EDV (overall P = 0.002, nonlinear P < 0.001) and a linear relationship with EF (P = 0.037, P = 0.125). Specifically, EF demonstrated a continuous inverse linear association with increasing LA FD, whereas EDV and ESV followed a complex multiphasic pattern rather than a simple monotonic trend. Conclusions The correlation between LV systolic function and LA FD suggests that LA shape may also be used as a tool to assess LV systolic function in patients with AF. Advances in knowledge In addition to the LAD, the LA FD may also provide clues to altered LV systolic function in this patient population.