Optimal Number of Heartbeats Required for Representing Left Chamber Volumes and Function in Patients with Rate-Controlled Atrial Fibrillation

Background: The optimal number of heartbeats required for representing left heart chamber function in patients with atrial fibrillation (AFib) has not been extensively studied. Methods: To determine the optimal number, we performed an automated quantification analysis of three-dimensional echocardiography (3DE) data sets in 93 patients with AFib for whom 10–20 consecutive one-beat full-volume 3DE data sets were acquired twice. We measured left ventricular end-diastolic volume (LVEDV), left ventricular ejection fraction (LVEF), and maximal left atrial volume (LAVmax) in each heartbeat; each parameter was averaged using a serial number of heartbeats randomly selected, and these values were compared with the averaged value obtained from the entire set of heartbeats. Coverage probability was determined using predefined cutoff values, the relative percentage differences in LVEDV and LAVmax of 5%, and the absolute percentage differences in LVEF of 5%. The optimal number of heartbeats was defined as the minimum number of heartbeats showing coverage probability ≥95%. Results: Out of 93 patients, 73 patients had acceptable left ventricular contour casts (feasibility, 78%), and 79 patients had acceptable left atrial contour casts (feasibility, 85%). Using the aforementioned criteria, the minimum optimal number of heartbeats was nine for LVEDV and six for LAVmax. The corresponding minimum optimal number of heartbeats for LVEF was eight. However, the results varied as a function of the size of the chamber, the left ventricular function, and whether the AFib ventricular rate was controlled. Conclusions: In patients with AFib, the optimal number of heartbeats required to obtain representative chamber volumes and function was six to nine heartbeats randomly selected using 3DE automated quantification software.