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N-terminal pro-Brain Natriuretic Peptide Levels Predict Left Ventricular Systolic Function in Patients with Chronic Kidney Disease
Jung Eun Lee, MD, So Yeun Choi, MD, Wooseong Huh, MD, Dae Joong Kim, MD, Ha Young Oh, MD, Yoon-Goo Kim, MD
Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea

Background.
N-terminal pro-brain natriuretic peptide (NT-BNP) can be a useful marker for left ventricular (LV) dysfunction in patients without kidney disease. However, renal dysfunction appears to increase NT-BNP levels. This study was conducted to clarify the relationship between NT-BNP and LV systolic function in patients with impaired renal function.

Methods.
We studied 256 CKD (chronic kidney disease) patients referred for echocardiography to evaluate ventricular function. Patients with a glomerular filtration rate (GFR) of 60 mL/min/1.73m2 or greater, or who were on dialysis, were excluded. Medical records were reviewed for cardiac history, laboratory findings, NT-BNP levels, and echocardiographic findings.

Results.
The median GFR value was 24 (13-36) ml/min/1.73m2 and median NT-BNP level was 4849 (1310-19009) pg/mL. There were 118 (46%) patients with LV systolic dysfunction (LV EF < 50%). The prevalence of LV systolic dysfunction increased from the lower to the upper NT-BNP quartiles (quartile I, 17%; quartile II, 34%; quartile III, 61%; and quartile IV, 72%; P < 0.001 for trend). The median NT-BNP level increased as GFR and LV ejection fraction (EF) decreased. Using multiple logistic regression models, the NT-BNP quartile was an independent predictor of LV systolic dysfunction after adjustment for renal function, compared with quartile I: quartile II, odds ratio (OR) 4.24 (95% CI 1.40 to 12.87); quartile III, OR 8.65 (95% CI, 2.92 to 25.64); and quartile IV, OR 34.83 (95% CI, 10.72 to 113.1). The area under the receiver operating characteristic curve and optimal cut points for NT-BNP were 0.78 and 2165 pg/mL, 0.81 and 4740 pg/mL, and 0.75 and 15892 pg/mL in patients with CKD stage 3,4,and 5, respectively.

Conclusion.
The NT-BNP level was a predictor of LV systolic dysfunction in patients with advanced stages of CKD. NT-BNP cut points for LV systolic dysfunction rose progressively as GFR decreased.

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