[Clinical-hemodynamic correlation of the NYHA/WHO system in idiopathic pulmonary artery hypertension. Clinical, therapeutic and long-term prognosis implications].

Background: The most often used functional classification for categorizing the degree of cardiac disability in patients with chronic left ventricular failure is the NYHAN/WHO system. In Idiopathic Pulmonary Arterial Hypertension [I-PAH], this system although used, has not been studied in detail regarding pulmonary hemodynamic parameters association and for long-term prognosis in each of the NYHA/WHO classes.

Methods: We retrospectively, studied the NYHA/ WHO system in 83 I-PAH patients.

[Calculated pulmonary vascular resistance, is definitively a worthless variable. Current methods for a better definition].

The term pulmonary vascular resistance [PVR] describes, in part, the forces opposing the flow across the pulmonary vascular bed. The equation traditionally used is based on the assumption that the pulmonary capillaries, as well as some others vessels in series behave like a Poiseuille resistance. This assumption implies a laminar type of flow of a homogeneous Newtonian fluid, however blood is not a Newtonian fluid and flow is pulsatile in the pulmonary circulation.