NPPB and mitral valve insufficiency: Previous investigations showed that serum concentrations of NT-proBNP act as an excellent biomarker for the diagnosis and monitoring of congestive heart failure and, indirectly, the myocardial function of dogs and cats [12, 13], and elevated NT-proBNP concentrations have been described in dogs with post-capillary PH due to left heart failure secondary to severe mitral regurgitation [14].