Subclinical left atrial enlargement (LAE) is highly prevalent in patients with stage 3-5 chronic kidney disease (CKD) and it is strongly associated with plasma sodium concentration, according to a newly published report.

In a study of 261 stage 3-5 CKD patients not on dialysis and free of symptomatic cardiovascular disease, 109 (41.8%) had subclinical LAE found on two-dimensional echocardiography, Angela Yee-Moon Wang, MD, of Queen Mary Hospital, University of Hong Kong, and colleagues reported online ahead of print in Nephrology Dialysis Transplantation.

Compared with patients in the lowest tertile of plasma sodium levels, those in the highest tertile had a 23% increased odds having LAE in a fully adjusted model. The importance of elevated plasma sodium appears to outweigh other factors well known to be associated with LAE, such as systolic hypertension, anemia, and hypoalbuminemia, according to the researchers.

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The study also found that the prevalence of LAE increased with the presence of left ventricular (LV) hypertrophy and increased with increasing severity of CKD. The researchers observed mild/moderate LAE and severe LAE in 22.9% and 41.3% of patients with LV hypertrophy compared with 13.2% and 12.5% of those without LV hypertrophy.

 “To our knowledge, this study is the first ever to demonstrate a strong, positive relationship between plasma sodium concentration and subclinical LAE in CKD patients,” the authors wrote.

The investigators pointed out that, contrary to a previous study by another team, they did not observe any association between plasma sodium concentration and estimated glomerular filtration rate in their study population. “This suggests that the association between high plasma sodium concentration and subclinical LAE is unlikely to be explained by worsening kidney function,” they stated.

Dr. Wang’s group commented that the left atrium serves as a contractile pump that delivers up to 30% of the LV filling. “With increasing stiffness or non-compliance of the left ventricle,” they explained, “left atrial pressure increases to maintain adequate LV filling and that gradually leads to atrial remodeling and chamber enlargement.”