Treatment of Pulmonary Hypertension

Pulmonary hypertension (PH) is defined hemodynamically as a resting mean pulmonary arterial pressure (mPAP) >20 mmHg. Management is heavily determined by the WHO group classification and clinical risk stratification.

WHO Classification (Groups 1–5)

Group	Etiology
1 – PAH	Idiopathic, heritable, drug/toxin-induced, connective tissue disease, HIV, portal hypertension, congenital heart disease
2	Left heart disease (most common cause of PH)
3	Lung disease / hypoxia (COPD, ILD, OSA)
4	Chronic thromboembolic PH (CTEPH)
5	Multifactorial / unclear mechanisms

Targeted PAH-specific drug therapy applies primarily to Group 1 (PAH). Groups 2–5 are managed by treating the underlying condition.

General/Supportive Measures (All Groups)

Diuretics — relieve right heart volume overload, reduce peripheral and ascitic edema
Supplemental oxygen — target SpO₂ >90–92%; essential in Group 3
Anticoagulation — historically used in IPAH; now selectively applied (clear indication in CTEPH on warfarin/rivaroxaban)
Digoxin — may support right ventricular function in selected patients
Avoid: high-altitude travel, vigorous exertion, pregnancy (high maternal mortality), vasodepressant medications (e.g., NSAIDs, non-selective beta-blockers)
Supervised exercise/rehabilitation — improves functional capacity

Vasoreactivity Testing (Group 1 / PAH)

Before initiating therapy, right heart catheterization (RHC) with vasoreactivity testing is performed using inhaled nitric oxide (or IV adenosine/epoprostenol).

Positive responders (<5% of PAH patients): defined as a decrease in mPAP ≥10 mmHg to ≤40 mmHg with unchanged/increased cardiac output → treat with high-dose calcium channel blockers (CCBs) (amlodipine, diltiazem, nifedipine) with favorable prognosis
Negative responders: the vast majority → require PAH-targeted therapy

PAH-Targeted Drug Therapy (Group 1)

Three major pathways are targeted:

1. Prostacyclin Pathway (IP Receptor Agonists / Prostanoids)

Promote vasodilation and inhibit platelet aggregation and vascular remodeling.

Drug	Route	Notes
Epoprostenol (Flolan, Veletri)	Continuous IV	Gold standard for high-risk PAH; requires central line; short half-life (~3 min)
Treprostinil	SC, IV, inhaled, oral	More stable; subcutaneous infusion common
Iloprost	Inhaled	6–9 inhalations/day
Selexipag	Oral	IP receptor agonist (non-prostanoid)

2. Endothelin Receptor Antagonists (ERAs)

Block endothelin-1-mediated vasoconstriction and remodeling.

Drug	Receptor selectivity	Notes
Ambrisentan	ETA-selective	Once daily; less hepatotoxicity than bosentan
Bosentan	ETA + ETB (dual)	LFT monitoring required
Macitentan	ETA + ETB (dual)	Once daily; improved morbidity/mortality (SERAPHIN trial)

3. Nitric Oxide–cGMP Pathway

Phosphodiesterase-5 Inhibitors (PDE5i)

Prevent cGMP degradation → sustained NO-mediated vasodilation.

Drug	Dosing
Sildenafil	20 mg TID
Tadalafil	40 mg once daily

Soluble Guanylate Cyclase (sGC) Stimulators

Riociguat — first-in-class; also approved for CTEPH; cannot be combined with PDE5i (hypotension risk)

Risk Stratification and Treatment Algorithm

According to Harrison's Principles of Internal Medicine (p. 7838):

Treatment-naïve PAH patients undergo vasoreactivity testing at RHC. Positive responders → high-dose CCBs. Negative responders → risk-stratified:

Risk	Clinical Features	Initial Therapy
Low/Intermediate	WHO FC I–III, no syncope, preserved 6MWD	Combination oral therapy (ERA + PDE5i)
High	WHO FC IV, syncope, advanced RV failure, rapid progression	Triple combination including IV epoprostenol + ERA + PDE5i/sGC stimulator

Upfront combination therapy (ambrisentan + tadalafil) is the standard of care for most PAH patients, supported by the AMBITION trial, which showed superiority over monotherapy.

Group-Specific Management

Group 2 (Left Heart Disease)

Optimize heart failure therapy (ACEi/ARB, beta-blockers, diuretics)
PAH-targeted drugs are not recommended (may worsen outcomes)

Group 3 (Lung Disease / Hypoxia)

Treat underlying lung disease; long-term O₂
Inhaled treprostinil (Tyvaso) has some evidence in PH-ILD (INCREASE trial)

Group 4 (CTEPH)

Surgical pulmonary endarterectomy (PEA) — curative in operable patients; treatment of choice
Balloon pulmonary angioplasty (BPA) — for inoperable or residual CTEPH
Riociguat — only approved PAH drug in CTEPH
Lifelong anticoagulation

Group 5 (Multifactorial)

Treat underlying cause (sarcoidosis, myeloproliferative disease, etc.)

Interventional and Surgical Options

Intervention	Indication
Atrial septostomy	Bridge to transplant; high-risk, refractory PAH
Pulmonary endarterectomy	CTEPH (Group 4) — potentially curative
Lung transplantation	End-stage PAH/PH refractory to maximal therapy; bilateral lung transplant preferred

Monitoring and Follow-Up

Key parameters tracked at every visit:

WHO/NYHA functional class
6-minute walk distance (6MWD)
NT-proBNP / BNP
Echocardiography (RV function, estimated RVSP)
RHC — reassessed if clinical deterioration or to guide escalation
REVEAL risk score — guides therapy escalation

Therapy is escalated (add-on drug, transition to IV prostanoid, or transplant listing) if patients remain at intermediate or high risk at follow-up.

Key Points

PAH is not cured by current drugs but functional class, exercise capacity, and survival are significantly improved
Combination therapy is superior to monotherapy
IV epoprostenol remains the only drug shown to improve survival in a randomized trial in PAH
CTEPH is the only potentially curable form of PH (via PEA)
Pregnancy carries very high mortality and should be avoided

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