Pulmonary hypertension is a rare disease that progressively affects the pulmonary vasculature and subsequently the heart. The initial insult is the pulmonary vasculature; but the survival is closely related to the heart, specifically in the RV function.
Pulmonary hypertension is simply a mPAP>25. It is broad group with many facets underneath it. It can be caused by increased pulm vascular resistance, pulmonary artery stiffness, left atrial HTN, incr pulm blood flow, and combinations thereof.
15-50 cases per 1 million people
REVEAL Registry - US registry of PAH (~3000 patients), 4:1 female predominance
It is hard to diagnose and is often diagnosed very late - it takes a high level of suspicion to diagnose early. To diagnose pulmonary hypertension you must do a right heart cath (RHC); doing this you will get these values:
Mean arterial pulmonary artery pressure (mPAP)
mPAP = 1/3 systolic PAP + 2/3 diastolic PAP
Pulmonary artery occlusion pressure (PaOP/wedge pressure) = RHC or swan, a surrogate for your LAP
Pulmonary Vascular Resistance = you must calculate it
PVR = mPAP - wedge pressure/CO (unit: woods)
Types of PH
Group 1 : Pulmonary arterial hypertension is a diagnosis of exclusion. It is type of pulmonary hypertension but not all PH patients have PAH; you must exclude group 2-5.
mPAP <25 + PVR >3 woods units + wedge <15, excluding other cause
Generally their PVR will be pretty high (5-6 wood units compared to ~3 in other causes)
Idiopathic PAH, Heritable PAH (BMPR2, ALK1, CAV1, etc), drug and toxin induced PAH
Associated with CTD, HIV, portal HTN, congenital heart diseases, shistosomiasis (uncontrolled HIV esp)
Very difficult to differentiate primary PAH in cirrhotics vs high PAH due to increased volume/high CO; important issue, must have mPAP<35 for transplant
Group 2 - Pulmonary hypertension due to left heart disease
Pulmonary venous hypertension (PVH) is by far the most common cause PH. It is especially important to differentiate patients with PH due to left heart congestion from patients with PVD; the diagnostic and treatment strategies differ.
LV systolic dysfunction, diastolic dysfunction
Valvular disease; Congenital/acquired left heart inflow/outflow obstruction
Group 3 - PH due to lung diseases and/or hypoxia
COPD, ILD, Other pulmonary diseases w/mixed restrictive and obstructive pattern
Sleep disordered breathing (i.e. OSA), alveolar hypoventilation disorders, chronic exposure to high altitude, developmental lung diseases
To Exclude: check PFTs, alpha 1, sleep study
Group 4 - chronic PE (CTEPH)
To exclude: V/Q scan
Group 5 - Idiopathic - unclear multifactorial mechanisms
Heme d/o, systemic d/o (sarcoidosis/vasculitis), metabolic d/o (thyroid), chronic renal failure and more
To exclude: super difficult. Liver serologies and more
But can you have multiple types of pulmonary hypertension?
A good way to think of this is by thinking of pulmonary hypertension as pre-capillary and post-capillary. You can check a diastolic pulmonary gradient (DPG) by looking at your pulmonary diastolic pressures and your wedge pressures. If the difference is minimal (<7) you know that the majority of the issues are coming from the L side of your heart, if there is a bigger discrepancy (i.e. >7) it may be two causes.
Transpulmonary gradient used to be used (mPAP - wedge>12 - may be pre-cap component to post-cap) but has been replaced by DPG.
Group 1 PAH: Most important pre-capillary
Group 2 (2/2 Left Heart): Post-capillary most of time
Group 3 (2/2 lung disease): Predominantly pre-capillary
Group 4: (CTEPH): Predominantly pre-capillary
Group 5: a mess, can be anything