Symmetric dimethylarginine in dogs with pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) causes impaired kidney function in humans. However, this occurrence has not been well investigated in PAH dogs. Serum symmetrical dimethylarginine (SDMA) is one of the early biomarkers of kidney impairment. The present study aims to evaluate SDMA levels of first diagnosed PAH (n=14) compared with healthy dogs (n=12) and to analyze the correlation between SDMA levels and significant echocardiographic parameters of PAH dogs. The mean SDMA of PAH dogs was statistically higher than that of healthy dogs ( P = 0.003), while the mean serum creatine level had no difference among groups ( P = 0.456). Precapillary PAH had a significant increase in SDMA level compared to postcapillary and healthy dogs ( P = 0.010). In PAH dogs, the Pearson correlation coefficient (r value) between SDMA and echocardiographic parameters (cardiac output: CO, cardiac index: CI, stroke volume: SV, and acceleration to ejection time ratio: AT/ET) revealed a negative relationship (r (CO) = -0.555, r( CI) = -0.570, r (SV) = -0.556 and r (AT/ET) = -0.537; overall P < 0.05), whereas a relationship between SDMA and ratio of right to left ventricular internal dimension during diastole (RVIDd/LVIDd) was positive (r (RVIDd/LVIDd) = 0.564; P = 0.018). SDMA and maximal pressure gradient of tricuspid regurgitation (TRmaxPG) had no correlation ( P > 0.05). In conclusion, PAH dogs had a significant increase in SDMA levels, particularly precapillary PAH dogs. The results show SDMA correlated negatively with CO, CI, SV, and AT: ET and positively with RVIDd/LVIDd, suggesting that severe PAH is related to worsening kidney function. More investigations, including urinalysis, kidney ultrasonography, other kidney injury biomarkers, and GFR, are necessary to confirm this phenomenon.