Pulmonary arterial hypertension (PAH) is a progressive, obliterative disease of the small pulmonary arteries driven by endothelial dysfunction, smooth muscle proliferation, and in situ thrombosis. Unlike systemic hypertension, it is not amenable to conventional antihypertensives; effective treatment requires agents that specifically target the three vasoactive pathways dysregulated in the pulmonary vasculature.
Pulmonary arterial hypertension (PAH) is defined hemodynamically as a mean pulmonary arterial pressure (mPAP) greater than 20 mmHg at rest, measured by right heart catheterization (RHC), with a pulmonary arterial wedge pressure (PAWP) at or below 15 mmHg and a pulmonary vascular resistance (PVR) greater than 2 Wood units, the last criterion distinguishing precapillary from postcapillary pulmonary hypertension.1 These hemodynamic thresholds were updated in the 2022 European Society of Cardiology (ESC) and European Respiratory Society (ERS) guidelines, which lowered the mPAP threshold from the prior value of 25 mmHg to the current 20 mmHg based on outcome data showing elevated mortality above this level in otherwise healthy individuals. PAH is classified as Group 1 in the World Health Organization (WHO) clinical classification of pulmonary hypertension, which encompasses five groups based on etiology and pathophysiology; PAH-specific therapies are approved for Group 1 only and should not be used empirically across other groups without careful consideration.
The underlying pathology of PAH involves three interrelated processes operating simultaneously in the small pulmonary arteries. First, endothelial dysfunction produces an imbalance between vasodilatory mediators, principally prostacyclin (PGI2) and nitric oxide (NO), and vasoconstrictive mediators, primarily endothelin-1 (ET-1), shifting the vascular tone toward sustained constriction. Second, abnormal proliferation and survival of pulmonary arterial smooth muscle cells (PASMCs) and endothelial cells produces progressive intimal thickening, medial hypertrophy, and adventitial fibrosis, collectively termed pulmonary vascular remodeling. Third, in situ microthrombosis within obliterated vessels further increases PVR. The net result is a fixed, progressive increase in PVR that forces the right ventricle (RV) to generate higher pressures to maintain forward cardiac output, eventually leading to right ventricular failure (RVF) as the RV hypertrophies and then dilates under sustained afterload.2
The three vasoactive pathways that current PAH pharmacotherapy targets are each defined by a key mediator whose production or signaling is abnormal in PAH. The prostacyclin pathway is deficient in PAH: endothelial prostacyclin synthase (PGIS) expression is reduced, leading to decreased PGI2 production, which normally activates prostacyclin receptors (IP receptors) on smooth muscle cells to raise cyclic adenosine monophosphate (cAMP), promote vasodilation, and inhibit platelet aggregation and pulmonary arterial smooth muscle cell (PASMC) proliferation. The endothelin pathway is overactive: ET-1 production is increased in PAH, driving vasoconstriction via the endothelin receptor type A (ETA receptor) on smooth muscle and contributing to vascular remodeling; the endothelin receptor type B (ETB receptor) has a more complex role, mediating both vasoconstriction on smooth muscle and ET-1 clearance and prostacyclin release on endothelium. The nitric oxide (NO) pathway is also deficient: reduced endothelial nitric oxide synthase (eNOS) activity lowers NO production, which normally diffuses into smooth muscle to activate soluble guanylate cyclase (sGC), producing cyclic guanosine monophosphate (cGMP) that activates protein kinase G (PKG) to relax smooth muscle; phosphodiesterase-5 (PDE-5) normally degrades cGMP in pulmonary smooth muscle, making PDE-5 inhibition an effective way to amplify residual NO-cGMP signaling.3
The WHO functional classification (WHO-FC) system grades PAH severity by symptom burden and is central to both risk stratification and treatment decisions. WHO-FC I denotes no symptoms with ordinary activity; WHO-FC II denotes slight limitation with ordinary activity; WHO-FC III denotes marked limitation with less than ordinary activity; WHO-FC IV denotes symptoms at rest or inability to carry out any activity without discomfort. Most patients present at WHO-FC II or III. Risk stratification using the European Society of Cardiology (ESC) and European Respiratory Society (ERS) three-strata model integrates WHO-FC, 6-minute walk distance (6MWD), N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels, and echocardiographic and hemodynamic parameters to categorize patients as low, intermediate, or high risk of one-year mortality, a classification that drives both the intensity of initial therapy and the target of treatment response.4
PAH-specific therapies (prostacyclin analogues, endothelin receptor antagonists, phosphodiesterase-5 inhibitors, soluble guanylate cyclase stimulators) are approved only for WHO Group 1 pulmonary hypertension. Prescribing them for Group 2 (left heart disease) or Group 3 (lung disease/hypoxia) can cause harm by selectively vasodilating the pulmonary vasculature and worsening ventilation-perfusion mismatch or unmasking elevated left-sided filling pressures. Confirm the WHO group and obtain right heart catheterization before initiating PAH-specific therapy.
The prostacyclin pathway represents the most potent pharmacological target in pulmonary arterial hypertension (PAH). Prostacyclin analogues and the selective prostacyclin receptor (IP receptor) agonist selexipag all raise cyclic adenosine monophosphate (cAMP) in pulmonary arterial smooth muscle cells (PASMCs) to produce vasodilation, antiproliferative effects, and inhibition of platelet aggregation. The four available agents differ markedly in route, half-life, and receptor selectivity.
Epoprostenol is synthetic prostacyclin (prostaglandin I2, or PGI2) and remains the reference standard against which all other PAH therapies are benchmarked. It binds prostacyclin receptors (IP receptors) on pulmonary arterial smooth muscle cells (PASMCs) to activate adenylyl cyclase via the Gs protein, raising intracellular cyclic adenosine monophosphate (cAMP), which activates protein kinase A (PKA) and produces vasodilation, pulmonary arterial smooth muscle cell (PASMC) antiproliferation, and inhibition of platelet aggregation. Epoprostenol has an extremely short plasma half-life of approximately 2 to 5 minutes at physiological pH and must be administered as a continuous intravenous (IV) infusion via a tunneled central venous catheter and ambulatory infusion pump. Rebound PAH crisis can occur with sudden interruption; patients and caregivers must be trained rigorously in pump management and line care, and backup medication and pump supplies must be immediately accessible at all times.5 The pivotal randomized controlled trial (RCT) by Barst and colleagues in 1996 demonstrated that continuous IV epoprostenol improved 6-minute walk distance (6MWD), hemodynamics, and survival compared with conventional therapy in severe PAH, establishing it as the only PAH agent with a demonstrated survival benefit from a randomized trial in the modern treatment era.
Treprostinil is a stable tricyclic benzindene prostacyclin analogue with a plasma half-life of approximately 4 hours, which permits multiple routes of administration: continuous subcutaneous (SC) infusion via an implanted pump, continuous IV infusion, inhaled nebulization four times daily, and an extended-release oral formulation. The subcutaneous route is the most commonly used; infusion site pain is the primary tolerability limitation, affecting the majority of patients and leading to discontinuation in a subset. The inhaled formulation (Tyvaso) delivers drug directly to ventilated lung regions, theoretically optimizing ventilation-perfusion matching, and was expanded to include group 3 pulmonary hypertension associated with interstitial lung disease (ILD) based on the INCREASE (INhaled TReprostinil in patients with pulmonary hypertension due to rEstricted lung diSease and Compromised gazE) trial. The oral formulation requires dose titration over weeks and has a higher gastrointestinal adverse effect burden than parenteral routes.6
Iloprost is a prostacyclin analogue with a half-life of approximately 20 to 30 minutes delivered exclusively by inhalation via a specialized nebulizer device, dosed six to nine times daily to maintain clinical effect. The inhalation route preferentially delivers drug to ventilated lung units, reducing the systemic vasodilatory adverse effects (flushing, jaw pain, headache, diarrhea) that accompany parenteral prostacyclin therapy. The frequent dosing schedule is the principal barrier to adherence. Iloprost is generally used as add-on therapy in patients already on an oral regimen rather than as monotherapy, and its role has become more limited as inhaled treprostinil has demonstrated longer-acting efficacy in the same administration niche.
Selexipag is an orally bioavailable, non-prostanoid selective IP receptor agonist that is chemically distinct from prostacyclin analogues. Its active metabolite ACT-333679 (the selective IP receptor-binding compound) binds the IP receptor with high selectivity and raises cAMP in PASMCs without the off-target effects of non-selective prostanoid receptor binding that contribute to some of the adverse effects of prostacyclin analogues. The pivotal GRIPHON (Selexipag for the Treatment of Pulmonary Arterial Hypertension) trial enrolled 1156 patients and demonstrated a 40 percent reduction in the composite primary endpoint of morbidity and mortality events compared with placebo over a median follow-up of 63 weeks, including reduction in disease progression and PAH hospitalization.7 Selexipag is taken twice daily, titrated to the maximum tolerated dose, and is approved as add-on therapy in patients already on endothelin receptor antagonist (ERA) and/or phosphodiesterase-5 (PDE-5) inhibitor therapy, or as monotherapy in patients not on those agents.
Abrupt interruption of continuous IV epoprostenol infusion can cause fatal rebound PAH crisis within minutes. Patients must carry emergency supplies including backup cassettes and battery-powered backup pump. Accidental line disconnection or pump malfunction requires immediate reconnection or bridging with inhaled iloprost until IV access is restored. Never leave a patient without a trained companion when traveling. Educate emergency department staff: epoprostenol must be restarted immediately; delay is life-threatening.
Endothelin receptor antagonists (ERAs) block the vasoconstrictive and proliferative effects of endothelin-1 (ET-1), which is produced in excess by dysfunctional pulmonary endothelium in pulmonary arterial hypertension (PAH). Three oral agents are approved: bosentan (dual ETA/ETB antagonist), ambrisentan (selective ETA antagonist), and macitentan (dual ETA/ETB antagonist with superior tissue penetration), each with a distinct receptor selectivity profile and safety signal that influences prescribing choice.
Endothelin-1 (ET-1) is a 21-amino-acid peptide produced by pulmonary endothelial cells and is the most potent endogenous vasoconstrictor yet characterized. In pulmonary arterial hypertension (PAH), ET-1 plasma and tissue levels are elevated and correlate with disease severity. ET-1 exerts its effects through two G protein-coupled receptors: the endothelin receptor type A (ETA receptor), expressed on pulmonary arterial smooth muscle cells (PASMCs), mediates vasoconstriction and cellular proliferation; and the endothelin receptor type B (ETB receptor), expressed on both smooth muscle and endothelium, mediates vasoconstriction when activated on smooth muscle but mediates ET-1 clearance and promotes prostacyclin and nitric oxide (NO) release when activated on endothelium. The net effect of dual receptor blockade versus selective ETA blockade on the ETB-mediated beneficial endothelial actions remains a theoretical concern that has not translated into clinically meaningful outcome differences between agents.8
Bosentan was the first oral endothelin receptor antagonist (ERA) approved for PAH and blocks both ETA and ETB receptors with approximately equal affinity. The pivotal BREATHE-1 (Bosentan Randomized trial of Endothelin Antagonist tHErapy) trial demonstrated improvements in 6-minute walk distance (6MWD) and time to clinical worsening compared with placebo in patients with WHO functional class (WHO-FC) III and IV PAH. Bosentan carries a hepatotoxicity risk, with dose-dependent elevations in alanine aminotransferase (ALT) and aspartate aminotransferase (AST), collectively liver aminotransferases, occurring in approximately 11 percent of patients; liver function tests (LFTs) must be monitored monthly throughout therapy. Bosentan is a potent inducer of cytochrome P450 (CYP) isoforms CYP3A4 (a major hepatic drug-metabolizing enzyme) and CYP2C9 (the isoform responsible for warfarin and some NSAID metabolism), which significantly reduces plasma concentrations of co-administered drugs metabolized by these pathways, including cyclosporine, glyburide, warfarin, and hormonal contraceptives. Bosentan is absolutely contraindicated in pregnancy (teratogenicity category X equivalent) and requires mandatory enrollment in the REMS (Risk Evaluation and Mitigation Strategy) program in the United States, which mandates monthly pregnancy testing and liver function test (LFT) monitoring.9
Ambrisentan is a selective ETA receptor antagonist with minimal ETB receptor activity. The ARIES-1 (Ambrisentan in Pulmonary Arterial Hypertension, Randomized, Double-Blind, Placebo-Controlled, Multicenter, Efficacy Study 1) and ARIES-2 (Ambrisentan in Pulmonary Arterial Hypertension Study 2) trials demonstrated dose-dependent improvements in 6MWD and time to clinical worsening. Ambrisentan has a hepatotoxicity risk substantially lower than bosentan; post-marketing data prompted label changes removing the mandatory monthly LFT monitoring requirement, though baseline and periodic monitoring remain clinically reasonable. Ambrisentan does not significantly induce CYP enzymes, reducing the drug interaction burden compared with bosentan. It carries the same absolute teratogenicity contraindication as all ERAs and requires REMS enrollment. A clinically important drug combination to avoid is ambrisentan with cyclosporine: cyclosporine inhibits the organic anion transporting polypeptide (OATP1B1) transporter responsible for ambrisentan hepatic uptake, increasing ambrisentan plasma concentrations substantially; bosentan is contraindicated with cyclosporine via a distinct pharmacokinetic mechanism involving CYP3A4 induction.
Macitentan is a dual ETA/ETB antagonist distinguished by its highly lipophilic structure, which confers enhanced tissue penetration and prolonged receptor occupancy compared with bosentan and ambrisentan. The SERAPHIN (Study with an Endothelin Receptor Antagonist in Pulmonary arterial Hypertension to Improve cliNical outcome) trial, published by Pulido and colleagues in 2013, was the first PAH trial powered for a morbidity-mortality composite endpoint and enrolled 742 patients in a randomized, double-blind design with a median follow-up of 115 weeks.10 Macitentan 10 mg reduced the primary composite endpoint of death or worsening PAH by 45 percent relative to placebo, driven by reductions in worsening events (hospitalization for PAH, need for additional PAH therapy) as well as a trend toward reduced mortality. Macitentan carries a lower hepatotoxicity signal than bosentan and does not require monthly LFT monitoring per labeling, though baseline assessment is standard practice. Hemoglobin reduction (anemia) occurs in approximately 8 percent of patients, attributed to plasma volume expansion and hemodilution from the drug's vasodilatory effect. Macitentan is now the most widely prescribed ERA in PAH based on its morbidity-mortality data, once-daily dosing, and more favorable drug interaction profile than bosentan.
All three endothelin receptor antagonists (ERAs) are absolutely contraindicated in pregnancy. Animal studies demonstrate severe teratogenicity at doses below the human therapeutic range. Women of childbearing potential must use two reliable forms of contraception throughout ERA therapy and for one month after discontinuation. Monthly pregnancy testing is required per REMS protocol for bosentan; ambrisentan and macitentan also require REMS enrollment with pregnancy testing. A positive pregnancy test during ERA therapy requires immediate drug discontinuation and urgent obstetric consultation.
Two pharmacological approaches amplify nitric oxide (NO)-driven cyclic guanosine monophosphate (cGMP) signaling in the pulmonary vasculature: phosphodiesterase-5 (PDE-5) inhibitors prevent cGMP degradation, and soluble guanylate cyclase (sGC) stimulators directly activate the enzyme that produces cGMP. Both approaches relax pulmonary vascular smooth muscle and inhibit proliferation, but they are mechanistically complementary rather than interchangeable, and their concurrent use is absolutely contraindicated due to risk of severe hypotension.
Phosphodiesterase-5 (PDE-5) is the dominant cGMP-degrading enzyme in pulmonary arterial smooth muscle and is overexpressed in pulmonary arterial hypertension (PAH), making it a well-validated therapeutic target. Sildenafil and tadalafil are selective PDE-5 inhibitors that prevent cGMP breakdown, thereby amplifying the vasodilatory and antiproliferative signaling initiated by endothelial nitric oxide (NO) production via endothelial nitric oxide synthase (eNOS). Sildenafil is dosed three times daily at 20 mg per dose for PAH, a regimen distinct from its erectile dysfunction dosing. The SUPER-1 (Sildenafil Use in Pulmonary Arterial Hypertension) trial demonstrated dose-dependent improvements in 6-minute walk distance (6MWD), pulmonary hemodynamics, and WHO functional class (WHO-FC) compared with placebo.11 Tadalafil at 40 mg once daily was studied in the PHIRST (Pulmonary arterial Hypertension and ReSponse to Tadalafil) trial and demonstrated a 33-meter improvement in 6MWD versus placebo in treatment-naive patients and significant reductions in time to clinical worsening; its once-daily dosing provides a convenience advantage over sildenafil. Both agents share the adverse effect profile of PDE-5 inhibition: headache, flushing, rhinitis, and visual color disturbance (from PDE-6 (phosphodiesterase-6) inhibition in the retina at higher concentrations). Both are contraindicated with nitrates of any formulation, including organic nitrates used for angina and nitric oxide donors, due to the risk of severe, potentially fatal hypotension from synergistic cGMP accumulation.
Riociguat is a soluble guanylate cyclase (sGC) stimulator that operates by a mechanism distinct from PDE-5 inhibitors. Rather than preventing cGMP degradation, riociguat directly stimulates sGC via two complementary mechanisms: it sensitizes sGC to endogenous NO, shifting the enzyme to its active conformation at lower NO concentrations than would otherwise be required; and it independently activates sGC through a NO-independent binding site, producing cGMP even in the setting of severely reduced NO bioavailability characteristic of advanced PAH endothelial dysfunction. The PATENT-1 (Pulmonary Arterial Hypertension Soluble Guanylate Cyclase-Stimulator Trial 1) trial demonstrated a 36-meter improvement in 6MWD, significant improvements in pulmonary hemodynamics, and improvements in WHO-FC and time to clinical worsening compared with placebo.12 Riociguat is also approved for inoperable or recurrent or persistent chronic thromboembolic pulmonary hypertension (CTEPH, WHO Group 4) based on the CHEST-1 (Chronic Thromboembolic Pulmonary Hypertension Soluble Guanylate Cyclase Stimulator Trial 1) trial, making it unique among PAH vasodilatory agents in having a CTEPH indication. The most clinically important safety restriction is the absolute contraindication with PDE-5 inhibitors: combined use produces additive sGC activation and cGMP accumulation, causing severe symptomatic hypotension that has resulted in deaths in clinical trials. This drug interaction is the defining safety constraint governing the use of riociguat in multidrug PAH regimens.
The practical implication of the riociguat-PDE-5 inhibitor contraindication is that a patient's PAH regimen can include an endothelin receptor antagonist (ERA) plus a PDE-5 inhibitor, or an ERA plus riociguat, but never a PDE-5 inhibitor plus riociguat simultaneously. When switching a patient from a PDE-5 inhibitor to riociguat, a washout period is required: sildenafil requires a minimum of 24 hours washout, and tadalafil requires a minimum of 48 hours washout given its longer half-life, before riociguat can be initiated. Careful hemodynamic monitoring during the transition is mandatory. Riociguat also carries a teratogenicity contraindication comparable to that of the ERAs, with mandatory contraception and monthly pregnancy testing required under the ADEMPAS (riociguat brand name) Risk Evaluation and Mitigation Strategy (REMS) program.
Co-administration of a phosphodiesterase-5 (PDE-5) inhibitor (sildenafil or tadalafil) with riociguat is absolutely contraindicated. The combination produces additive cyclic guanosine monophosphate (cGMP) accumulation via complementary mechanisms, resulting in severe symptomatic hypotension that has caused deaths. Before initiating riociguat, confirm the patient is not taking sildenafil or tadalafil. If switching from a PDE-5 inhibitor to riociguat, observe a minimum 24-hour washout for sildenafil or 48-hour washout for tadalafil before the first riociguat dose.
Contemporary pulmonary arterial hypertension (PAH) management has moved from sequential add-on monotherapy to upfront combination of agents from two pathway classes in most newly diagnosed patients. The goal is to achieve and maintain low-risk status, defined by a composite of favorable functional, biomarker, and hemodynamic parameters, rather than simply stabilizing disease.
The rationale for combination therapy is mechanistic: the three vasoactive pathways are biologically distinct, and targeting multiple pathways simultaneously produces additive or synergistic pulmonary vasodilation and antiproliferative effects not achievable with any single agent. Evidence for upfront combination comes primarily from the AMBITION (Ambrisentan and Tadalafil in Patients with Pulmonary Arterial Hypertension) trial, published by Galie and colleagues in 2015, which randomized 500 treatment-naive patients with WHO functional class (WHO-FC) II or III PAH to ambrisentan plus tadalafil versus either agent alone.13 The combination arm demonstrated a 50 percent reduction in the primary composite endpoint of time to first clinical failure event (death, hospitalization for PAH, disease progression, or unsatisfactory long-term clinical response) compared with the pooled monotherapy arms, with a number needed to treat of approximately 6 to prevent one clinical failure event over the study period. This trial established upfront dual oral combination as the evidence-based standard for treatment-naive patients with WHO-FC II or III PAH who are not at high risk.
The three-strata risk model from the 2022 European Society of Cardiology (ESC) and European Respiratory Society (ERS) guidelines categorizes patients as low, intermediate, or high risk of one-year mortality based on a validated panel of variables: WHO-FC (I or II, low; III, intermediate; IV, high), 6-minute walk distance (6MWD) above 440 meters, intermediate 165 to 440 meters, below 165 meters, N-terminal pro-B-type natriuretic peptide (NT-proBNP) below 300 ng/L low, right ventricular (RV) function on echocardiography, and invasive hemodynamics including right atrial pressure (RAP) and cardiac index (CI). The treatment algorithm is risk-driven: newly diagnosed low- or intermediate-risk patients receive upfront dual oral combination (endothelin receptor antagonist (ERA) plus phosphodiesterase-5 (PDE-5) inhibitor is the evidence-based choice); high-risk patients receive upfront triple combination including a parenteral prostacyclin analogue. Re-assessment at 3 to 6 months determines whether the patient has achieved low-risk status; those who have not met treatment targets step up to triple therapy.4
The treatment target in PAH is explicit: the goal is to achieve low-risk status, not merely to prevent deterioration. A patient who remains at intermediate risk after 3 to 6 months of dual combination therapy has not achieved an adequate response and should be escalated regardless of subjective symptom stability. The clinical inertia that characterized the sequential monotherapy era, in which patients remained on a failing regimen for years while slowly deteriorating, has been replaced by a proactive re-assessment model that treats persistent intermediate risk as a treatment failure requiring escalation. Escalation options for patients failing dual oral combination include adding an inhaled or subcutaneous prostacyclin agent, adding selexipag, or transitioning to continuous IV epoprostenol in those who remain at high or intermediate-high risk after oral triple therapy.
Specific prescribing considerations govern PAH pharmacotherapy across all classes. All approved PAH vasodilator therapies require expert center management and are not suitable for initiation by clinicians without PAH training. Before initiating any PAH-specific therapy, right heart catheterization (RHC) is mandatory to confirm the hemodynamic diagnosis and exclude Group 2 or 3 disease. Vasoreactivity testing (VRT) with inhaled nitric oxide (NO) or IV epoprostenol at the time of RHC identifies the small minority of patients (typically those with idiopathic PAH with WHO-FC I or II disease and no features of right heart failure) who have a sustained acute vasodilator response, defined as a reduction in mean pulmonary arterial pressure (mPAP) by at least 10 mmHg to an absolute mPAP below 40 mmHg with increased or unchanged cardiac output; these vasoreactive patients can be treated with high-dose calcium channel blockers (CCBs), specifically nifedipine, diltiazem, or amlodipine, as first-line monotherapy and have markedly better prognosis than non-vasoreactive patients.4 All other patients should receive guideline-directed PAH-specific combination therapy as described above.
Initial treatment: upfront dual oral combination (ERA plus PDE-5 inhibitor) for WHO-FC II/III; upfront triple combination including parenteral prostacyclin for WHO-FC IV or high-risk patients. Re-assess at 3 to 6 months using the three-strata risk model (WHO-FC, 6MWD, NT-proBNP, echo, hemodynamics). If patient achieves low-risk status: continue current regimen and re-assess every 3 to 6 months. If patient remains intermediate or high risk: escalate therapy. Do not wait for clinical deterioration to act; persistent intermediate risk is a treatment failure.
Humbert M, Kovacs G, Hoeper MM, et al. 2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension. Eur Heart J. 2022;43(38):3618–3731.
doi:10.1093/eurheartj/ehac237Rabinovitch M. Molecular pathogenesis of pulmonary arterial hypertension. J Clin Invest. 2012;122(12):4306–4313.
doi:10.1172/JCI60658Tuder RM, Archer SL, Dorfmuller P, et al. Relevant issues in the pathology and pathobiology of pulmonary hypertension. J Am Coll Cardiol. 2013;62(25 Suppl):D4–D12.
doi:10.1016/j.jacc.2013.10.025Humbert M, Kovacs G, Hoeper MM, et al. 2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension. Eur Heart J. 2022;43(38):3618–3731.
doi:10.1093/eurheartj/ehac237Barst RJ, Rubin LJ, Long WA, et al. A comparison of continuous intravenous epoprostenol (prostacyclin) with conventional therapy for primary pulmonary hypertension. N Engl J Med. 1996;334(5):296–302.
doi:10.1056/NEJM199602013340504Channick RN, Olschewski H, Seeger W, Staub T, Voswinckel R, Rubin LJ. Safety and efficacy of inhaled treprostinil as add-on therapy to bosentan in pulmonary arterial hypertension. J Am Coll Cardiol. 2006;48(7):1433–1437.
doi:10.1016/j.jacc.2006.05.070Sitbon O, Channick R, Chin KM, et al. Selexipag for the treatment of pulmonary arterial hypertension. N Engl J Med. 2015;373(26):2522–2533.
doi:10.1056/NEJMoa1503184Dupuis J, Hoeper MM. Endothelin receptor antagonists in pulmonary arterial hypertension. Eur Respir J. 2008;31(2):407–415.
doi:10.1183/09031936.00078207Rubin LJ, Badesch DB, Barst RJ, et al. Bosentan therapy for pulmonary arterial hypertension. N Engl J Med. 2002;346(12):896–903.
doi:10.1056/NEJMoa012212Pulido T, Adzerikho I, Channick RN, et al. Macitentan and morbidity and mortality in pulmonary arterial hypertension. N Engl J Med. 2013;369(9):809–818.
doi:10.1056/NEJMoa1213917Galie N, Ghofrani HA, Torbicki A, et al. Sildenafil citrate therapy for pulmonary arterial hypertension. N Engl J Med. 2005;353(20):2148–2157.
doi:10.1056/NEJMoa050010Ghofrani HA, Galie N, Grimminger F, et al. Riociguat for the treatment of pulmonary arterial hypertension. N Engl J Med. 2013;369(4):330–340.
doi:10.1056/NEJMoa1209655Galie N, Barberena-Ruiz A, Teal S, et al. Initial use of ambrisentan plus tadalafil in pulmonary arterial hypertension. N Engl J Med. 2015;373(9):834–844.
doi:10.1056/NEJMoa1413687