Heart disease claims the lives of many patients with chronic kidney disease (CKD). Now a new study suggests a potential avenue: thickening of the heart’s left ventricle spurred, in part, by excess sodium consumption and retention.
In a novel experiment, Markus Schneider, MD, of the University of Erlangen-Nurnberg in Erlangen, Germany, and colleagues used Na-magnetic resonance imaging (MRI) to measure sodium stores in skin at the calf in 99 white patients with mild to moderate CKD. Urinary sodium excretion, employed in previous studies, less reliably reflects daily sodium intake, they suggested.
The investigators also assessed overhydration by examining total body water via bioimpedence spectroscopy and tracked 24-hour blood pressure. Cardiac MRI was used to measure left ventricular mass (LVM). Left ventricular hypertrophy was found in 30% of men and 26% of women (median age 65). In addition, 28% of patients had diabetes and 92% arterial hypertension.
CKD patients exhibited a wide range of skin sodium and total water values, according to results published online ahead of print in the Journal of the American Society of Nephrology. Although skin sodium and total body water correlated to a degree, skin sodium demonstrated a much stronger relationship with systolic blood pressure and LVM. Skin sodium emerged as a telling variable for LVM, independent of blood pressure and overhydration, after linear regression analysis.
“We believe that skin sodium reflects deposition of excess sodium,” Dr Schneider stated in a news release. “Our finding of a strong relationship between skin sodium and changes in the structure of the heart suggests that interventions that reduce skin sodium content — for example dietary sodium restriction or medications that lead to increased sodium excretion — may have beneficial effects on the heart in patients with kidney disease.”
CARVIDA (CARdioVascular In Depth Assessment), a substudy of the GCKD (German Chronic Kidney Disease) study, had several limitations. It was cross-sectional, involved few patients, and did not assess dietary sodium intake. Future studies are needed to clarify whether increased sodium content precedes the development of LVH and, if so, whether interventions slow or prevent LVH. The investigators also suggested examining the role of sodium in LVH in patients with more advanced CKD.
2. Skin Sodium Content Linked to Heart Problems in Patients With Kidney Disease. American Society of Nephrology. February 2, 2017. [press release]