Pulmonary hypertension (PH) is a broad topic encompassing primary and secondary etiologies. Like systemic hypertension, PH refers to elevated pressures in the pulmonary vessels. It’s essential to understand how PH is classified and which specific vessels are involved: pulmonary arteries → pulmonary capillaries → pulmonary veins.
PRE-capillary PH refers to elevated pulmonary ARTERIAL pressures, and POST-capillary refers to pulmonary VENOUS hypertension. For example, it makes sense that WHO Group 2 PH (caused by left heart issues) will initially increase pulmonary venous pressures as blood flow is directed backward. In reality, many patients with PH have both arterial and venous problems.
Symptoms can initially be relatively nonspecific and include exertion dyspnea and fatigue. As the severity worsens, signs of overt right heart failure may predominate. The history/physical exam combined with echocardiography, labs, EKG, and cardiac catheterization can help hone in on the diagnosis. In addition, the functional classification helps me ascertain the day-to-day limitations a patient’s PH has incurred to help me gauge how “sick” they might be in the ICU or OR when faced with other clinical situations (septic shock, complex cardiac surgeries, etc.)
I remember the PH groups by writing the number and looking at its mirror or flipped image. For example, ‘1’ looks like a blood vessel (pulmonary arterial hypertension). ‘2’ mirrored on itself looks like a heart (left heart disease). ‘3’ mirrored on itself resembles a pair of lungs (chronic pulmonary disease). ‘4’ flipped vertically looks like a chair suggestive of stasis and clot formation (CTEPH). ‘5’ is everything else!
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