chapter  78
Pulmonary Hypertension
Pages 22

DEFINITION The pulmonary vascular bed is normally a low-pressure, low-resistance circulation with compliant thin-walled vessels. Pulmonary hypertension (PH) is considered to be present when the pulmonary artery (PA) systolic pressure exceeds 35 mm Hg or the PA mean pressure (mPAP) is over 25 mm Hg at rest. Clinically significant PH is usually associated with substantially higher PA pressures. Although PH can be suspected based on echocardiographic estimates, the diagnosis cannot be established in the absence of invasive measurements.