Research Communications of the 24th ECVIM-CA Congress

No conflicts of interest reported. Azotemia in dogs with chronic heart failure may reflect impaired renal function not only because of inadequate renal perfusion, but also due to organic renal injury. Impaired renal function is observed in 50% of dogs with heart failure. Altered renal hemodynamics due to decreased cardiac output results in renal hypoperfusion, and resultant elevation of blood urea nitrogen and creatinine, defined as azotemia. Azotemia is a prognostic factor in dogs with mitral regurgitation, therefore, preservation and/or restoration of renal function is thought to improve prognosis. Medical treatment for heart failure, however, includes angiotensin converting enzyme inhibitors and loop diuretics, which has been shown to increase the risk of developing azotemia. We hypothesized that mitral valve repair surgery ameliorates renal function by improvement of systemic hemodynamics. The change in renal function in dogs with mitral regurgitation was assessed by evaluating time-dependent changes in glomelular filtration rate by inulin clearance before and after cardiac surgery. Eighteen dogs with severe mitral regurgitation with azotemia (plasma urea nitrogen level > 28 mg/dL, plasma creatinine level >1.9 mg/dL) were included in this study. The glomerular filtration rate in all dogs were evaluated by determining inulin clearance before and 3 months after surgery. Serum atrial natriuretic peptide level, plasma NT-pro brain natriuretic peptide level, plasma urea nitrogen concentration, and plasma creatinine concentration were measured at each time point as well as during the initial staging of heart failure based on the International Small Animal Cardiac Health Council (ISACHC). Left atrial/aorta ratio by echocardiography and vertebral heart size by thoracic radiographs were also measured. Glomerular filtration rate significantly increased 3 months after surgery (40.0 ml/min/m 2 [25.6 -123.0], 2.7 ml/min/kg [1.0 -5.3]) compared to before surgery (38.4 ml/min/m 2 [12.6 -50.3], 2.2 ml/min/kg [0.7 -3.8]) (P < 0.05). The ISACHC stage of heart failure was improved at 3 months after surgery compared to before surgery. In addition, serum atrial natriuretic peptide level, plasma NT-pro brain natriuretic peptide level, plasma urea nitrogen concentration, LA/Ao and VHS significantly decreased after surgery (P < 0.05). The use of diuretics decreased after mitral valve repair surgery and consequently, a decrease in plasma urea nitrogen and creatinine levels were observed. Therefore, this suggests that the main cause of azotemia in dogs with mitral regurgitation may be due to inadequate renal blood flow and exacerbation by the use of diuretics.