We read with great interest the reports by Otani et al. and Yang et al. Both studies were well designed and validated the feasibility of the novel, fully automatic, single-beat three-dimensional quantification software HeartModel in patients with atrial fibrillation (AF). The investigators concluded that HeartModel can be used reliably in patients with AF for the assessment of left-heart chamber size and function and that measurements derived from a single index beat are noninferior to and comparable with the average value obtained by analyzing 10 to 20 consecutive beats. These results indeed represent great progress in the application of three-dimensional echocardiography in patients with AF. However, as it has frequently been a problem to measure time intervals from two-dimensional imaging with most vendors’ software, we wonder how the researchers measured the time intervals of each recorded beat to determine the index beat in patients with AF.