PVR

Pulmonary Vascular Resistance (PVR) is a measure of the resistance that the blood vessels of the lungs must overcome to facilitate blood flow through the lungs. It is an important parameter in the assessment of cardiac function and is crucial in the diagnosis and management of various cardiovascular diseases, including pulmonary hypertension, heart failure, and congenital heart disease. PVR is calculated based on the difference in pressure between the pulmonary artery and the left atrium of the heart, divided by the cardiac output. The unit of measurement is dynes·sec·cm^−5, though it is often converted to Wood units (WU) for clinical use.

Calculation

The formula to calculate PVR is:

\[PVR = \frac{(Mean Pulmonary Artery Pressure - Left Atrial Pressure)}{Cardiac Output} \times 80\]

where the pressures are measured in millimeters of mercury (mmHg) and the cardiac output in liters per minute (L/min). The factor 80 is used to convert the units to dynes·sec·cm^−5.

Clinical Significance

PVR is a critical parameter in evaluating the pulmonary circulation and is particularly important in the context of diseases that affect the pulmonary arteries, such as pulmonary arterial hypertension (PAH). An elevated PVR indicates increased resistance in the pulmonary vasculature, which can be due to various pathological conditions such as vascular remodeling, vasoconstriction, or thrombosis. Monitoring PVR is essential in assessing the severity of these conditions and in guiding treatment decisions.

Treatment and Management

Treatment strategies for conditions associated with high PVR, such as PAH, focus on reducing the pulmonary vascular resistance to improve symptoms and increase survival. Medications used include vasodilators, endothelin receptor antagonists, phosphodiesterase inhibitors, and prostacyclin analogs. In some cases, surgical interventions such as atrial septostomy or lung transplantation may be considered.

See Also

• Cardiac Output
• Pulmonary Artery Pressure
• Pulmonary Hypertension
• Heart Failure