Implications of Indeterminate and Determined Etiologies Leading to Small Left Atria

Background: Small left atria (LA) is associated with an increased risk of mortality. Objectives: To determine whether the attributed risk of mortality is influenced by the underlying etiologies leading to decreased volumes. Methods: We retrospectively evaluated patients with an available LA volume index (LAVI) as measured by echocardiography who came to our institution between 2011 and 2016. Individuals with small LA (LAVI < 16 ml/m²) were included and divided according to the etiology of the small LA (determined or indeterminate) and investigated according to the specific etiology. Results: The cohort consisted of 288 patients with a mean age of 56 ± 18 years. An etiology for small LA was determined in 84% (n=242). The 1 -year mortality rate of the entire cohort was 20.5%. Patients with indeterminate etiology (n=46) demonstrated a lower mortality rate compared with determined etiologies (8.7% vs. 22.7%, P= 0.031). However, following propensity score adjustments for baseline characteristics, there was no significant difference between the groups (P= 0.149). The only specific etiology independently associated with 1-year mortality was the presence of space occupying lesions (odds ratio 3.26, 95% confidence interval 1.02-10.39, P= 0.045). Conclusions: Small LA serve as a marker for negative outcomes, and even in cases of undetected etiology, the prognosis remains poor. The presence of small LA should alert the physician to a high risk of mortality, regardless of the underlying disease.