Abstract 451: Central Hemodynamics Constitutes the Link Between Microalbuminuria and Elevated B-type Natriuretic Peptide Level

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Abstract

Recent research has noted a pathological link between the heart and kidney, known as cardio-renal syndrome. However, little is clear about the pathophysiological mechanism behind it. A relationship of altered central hemodynamics to microalbuminuria in hypertension has been demonstrated (Hypertension 2011;58:839-846). The present study was conducted to investigate two hypotheses: 1) a link between albuminuria and plasma B-type natriuretic peptide (BNP); and 2) involvement of central hemodynamics in this link. In 392 patients with uncomplicated hypertension (age, 56±12 years), the radial pressure waveforms were recorded with applanation tonometry to estimate the central aortic pressure parameters. The pulse wave velocity (PWV) was measured in carotid-femoral (aortic) and carotid-radial (peripheral) regions. Albuminuria was defined as urinary albumin/creatinine ratio (UACR) ≥30 mg/g of creatinine. The log-transformed BNP (median, 14 pg/ml) was correlated (P≤0.006) with aortic systolic (r=0.31) and pulse (r=0.46) pressures, aortic forward (r=0.41) and augmented (r=0.26) pressures, mean arterial pressure (r=0.14), and aortic (r=0.39) but not peripheral (r=–0.09) PWV. The correlation with the aortic pulse pressure tended to be closer than the brachial pulse pressure (P=0.07). The BNP was correlated (P<0.001) positively with UACR (r=0.34), and negatively with estimated glomerular filtration rate (eGFR, r=–0.39). The presence of albuminuria was associated with an elevation of BNP (≥40 pg/ml) in a stepwise logistic model adjusted for age, body mass index, diabetes, eGFR, use of renin-angiotensin inhibitors and β-blockers (odds ratio: 2.74; P=0.007). Of note, however, additional adjustment for the aortic pulse pressure rendered this association statistically insignificant, and the aortic pulse pressure emerged as the strongest predictor of the BNP elevation (odds ratio: 1.41 per 10mmHg increase; P=0.003). In each patient subgroup with normo-, micro-, and macro-albuminuria, wider aortic pulse pressure was always associated with higher BNP level. In conclusion, albuminuria and elevated BNP are closely connected in hypertension. The central hemodynamics plays a pivotal role in mediating this cardio-renal connection.

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