Pulmonary Vascular Resistance (PVR) is a critical hemodynamic measurement used to diagnose and manage Pulmonary Hypertension and right-sided heart failure.
The Pulmonary Circuit
The human circulatory system is divided into two parts. The left heart pumps blood to the entire body at very high pressures (the systemic circuit). The right heart pumps blood only to the lungs at very low pressures (the pulmonary circuit). Because the lungs are a delicate, low-pressure system, the right ventricle of the heart is physically much thinner and weaker than the left ventricle.
Pulmonary Hypertension
If the blood vessels in the lungs become stiff, narrow, or clogged with blood clots (like in a Pulmonary Embolism), the resistance to blood flow spikes. This is an elevated PVR. The right ventricle must suddenly work much harder to push blood through the lungs. Over time, this extreme exertion causes the right ventricle to hypertrophy (thicken), dilate, and eventually fail entirely.
PVR = [80 × (Mean Pulmonary Artery Pressure - PCWP)] / Cardiac Output
By accurately calculating the PVR during a right heart catheterization, cardiologists can determine if a patient requires powerful pulmonary vasodilators (like sildenafil or prostacyclins) to open the lung vessels and save the right heart.