A normal and particularly small (<35 mm) left atrial size measured during echocardiography suggests low likelihood of moderate or severe left ventricular systolic dysfunction.

Introduction: The left atrium (LA) size can change due to cardiac pathologies like heart failure and aging. While the link between LA enlargement and left ventricular (LV) dysfunction is acknowledged, this study aims to assess the negative predictive value of normal LA size concerning the severity of LV systolic function in a large cohort undergoing diagnostic echocardiography.

Methods: This retrospective cohort study, conducted at the University of California, Irvine Medical Center from 1984 to 1998, aimed to elucidate the negative predictive value of normal LA size measured by M-mode and two-dimensional echocardiography in a large cohort undergoing diagnostic assessment.

Results: In the analysis of 22,390 echocardiograms, 55.1% exhibited normal LA size (<40 mm), while 44.9% showed abnormal LA size (≥40 mm). Within the normal LA size group, only 2.4% demonstrated abnormal LV systolic function, with 1.1% mildly depressed, 0.7% moderately depressed, and 0.6% severely depressed LV function. The negative predictive value of normal LA size for abnormal LV systolic function was calculated at 97.5%, rising to 99.3% and 99.4% for moderate or severely decreased LV systolic function, respectively. In patients with small LA size (<35 mm), moderate to severely depressed LV systolic function was observed in only 0.8%, with severe LV systolic dysfunction in 0.3%, yielding an overall prevalence of 1.5% for all systolic dysfunction in the small LA size group.

Conclusion: Our findings underscore the clinical significance of normal LA size as a reliable indicator of preserved LV function.