Association between plasma phosphate/pyrophosphate ratio and computed tomography-derived aortic valve calcification...

Inorganic pyrophosphate (PPi) is an endogenous inhibitor of soft tissue calcification. A disturbed equilibrium between pro- and anti-mineralization agents, like extracellular phosphate (Pi) and PPi, has been implicated in the mechanism of aortic valve calcification (AVC). We aimed to investigate the association of the plasma PPi concentration and Pi/PPi ratio with the degree AVC in cardiovascular patients.

One hundred and fifty-four patients referred for cardiac computed tomography (CT), including 43 individuals with severe aortic stenosis, were prospectively enrolled. The aortic valve calcium score (AVCS) was measured on non-contrast CT images. Plasma PPi level was determined enzymatically. Of the entire population (age: 67 ± 12 years, 42.5% female), 42% had some degree of AVC (range 9-6641 AU). Plasma PPi showed a significant positive association with plasma Pi and LDL cholesterol (LDL-C) concentration and was inversely related to alkaline phosphatase activity. When controlled for age, female patients had higher PPi levels. In univariate analysis, plasma PPi level did not show an association with AVCS; however, the Pi/PPi ratio was significantly positively associated with the degree of AVC [estimate: 1508.1; standard error (SE) 616.0, P = 0.015], along with age, hypertension, plasma lipoprotein(a) concentration, and statin treatment, whereas estimated glomerular filtration rate and LDL-C level showed significant negative associations. In multivariate analysis, only age and Pi/PPi ratio remained significant determinant of the AVCS (estimate: 1128.6; SE 562.5, P = 0.047).

This is the first study to investigate the association between PPi homeostasis and AVC in humans. The plasma Pi/PPi ratio was significantly positively associated with the AVC load even after adjustment for traditional risk factors.