AbstractCardiac compartmental size depends on sex, with smaller values found in (healthy) women compared to a matched group of men. Various types of heart disease may cause dilation of the affected chamber. For example, atrial fibrillation (AF) is associated with enlarged left atrial (LA) size, often also implying increased left ventricular (LV) size. Sex‐specific differences appear to persist during disease states. Thus, chamber volumes depend on both sex and the severity of the underlying disorder, and require quantification to evaluate the effect of interventions. Often, we rely on the popular performance metric ejection fraction (EF) which refers to the ratio of the minimum and maximum LV or LA volumetric values observed during the cardiac cycle. Here we discuss a sex stratified analysis of LVEF and LAEF in AF patients as treated by LA appendage closure, while comparing those with or without device‐related thrombosis. Also, an alternative analysis based on primary data is presented while emphasizing its attractiveness. In any event, age‐ and sex‐specific reference values as broadly documented for various imaging modalities should be applied to LA and LV.