NPPB and pulmonary arterial hypertension: PTT has been demonstrated to be altered in various diseases, including HF,26,27 pulmonary hypertension,28,29 chronic lung disease,30 and to correlate with cardiac function.17 Similarly, elevated levels of NT-proBNP are a marker of haemodynamic stress and NT-proBNP may be elevated due to various factors such as volume overload and ventricular or valvular dysfunction.