The purpose of this study was to retrospectively assess the accuracy of the maximal left atrial volume (LAV_max) measured at 75% of the cardiac cycle compared to the 40% measurements and to evaluate this volume according to age and gender.

A total of 150 patients with a mean age of 50±17 (SD) years (range: 21–79 years) were analyzed. There were 78 men and 72 women. LAV_max were measured from retrospective triphasic cardiac-gated multi-detector computed tomography (MDCT) data at the 40% (LAV₄₀) and 75% (LAV₇₅) of the RR cycle phases by a semi-automatic method.

LAV₄₀was 50.7±14mL/m² and LAV₇₅ was 42.5±13mL/m². The difference was statistically significant. Considering the reference range of LAV_max reported in the literature, 33% of the patients had enlarged LA with LAV₄₀ and only 17% with LAV₇₅. These volumes were positively influenced by age but not by gender. The relationship between LAV₇₅ and LAV₄₀ was: LAV₇₅=0.908 LAV₄₀–3.486 (r²=0.92) or LAV₄₀=1.1×LAV₇₅+3.8 (r²=0.92).

LAV_max measured at the 75% of the cardiac cycle phase significantly underestimates actual LAV leading to reconsider normal values. LAV₄₀ can be computed from the measured value of LAV₇₅ obtained on prospective ECG-gated MDCT.