Pulmonary Hypertension
Clinical Snapshot
Pulmonary hypertension (PH) is not a single disease but a hemodynamic state — persistently elevated pressure in the pulmonary arterial circulation — that arises from at least five mechanistically distinct groups of underlying disease, each with a fundamentally different treatment approach (see below). Confirming which group a patient's PH belongs to is the single most consequential step in their work-up, because the disease-modifying, PAH-specific vasodilator therapy detailed in this chapter is appropriate for only one of the five groups and can cause real harm in two of the others (see Choose Initial Treatment and Red Flags & Refer).
The diagnostic threshold — and a recent, genuinely important update
PH is defined hemodynamically by right heart catheterization (RHC), the diagnostic gold standard that cannot be replaced by echocardiography or any other noninvasive test.[1] For decades the diagnostic threshold was a mean pulmonary arterial pressure (mPAP) of 25 mmHg or higher at rest. The 2022 ESC/ERS international guideline lowered this threshold to mPAP greater than 20 mmHg at rest — a change based on normative right heart catheterization data in healthy adults (in whom mPAP averages roughly 14 mmHg) and on prognostic data showing worse outcomes even in this lower range.[2] Pulmonary arterial hypertension (PAH) specifically requires, in addition to mPAP >20 mmHg: a pulmonary arterial wedge pressure (PAWP) of 15 mmHg or less (confirming a precapillary process), and a pulmonary vascular resistance (PVR) greater than 2 Wood units — itself lowered from the historical >3 Wood unit threshold.[2] This refinement better reflects the true upper limit of normal, but the guideline is explicit that it does not yet change who should be treated: the efficacy of PAH-specific therapy in patients who fall only in this newly captured, mildly elevated range (mPAP 21-24 mmHg and/or PVR 2-3 Wood units) remains unknown, and starting therapy on hemodynamics alone in that grey zone is not currently supported.[2]
Epidemiology
PH overall is common — an estimated 1% of the global population, rising to roughly 10% of those aged 65 and older — and in the great majority of these patients it is due to left heart disease or lung disease (Groups 2 and 3 below), not PAH.[1] PAH itself is comparatively rare, with an estimated incidence of up to 7.6 cases per million adults and a prevalence of up to 26-100 per million adults, but its morbidity and mortality are disproportionate to its rarity: a diagnosis of PH of any type confers roughly a sevenfold increase in age- and sex-standardized mortality.[1]
The WHO five-group clinical classification
The current classification, summarized below, is the framework every subsequent section of this chapter refers back to.[1]
| Group | Includes | Core treatment principle |
|---|---|---|
| Group 1 — Pulmonary arterial hypertension (PAH) | Idiopathic; heritable (most often BMPR2); drug- and toxin-induced; associated with connective tissue disease, HIV, portal hypertension, congenital heart disease, or schistosomiasis; long-term calcium-channel-blocker responders; PAH with overt venous/capillary involvement (PVOD/PCH); persistent PH of the newborn | The focus of this chapter — PAH-specific vasodilator therapy targeting the endothelin, nitric oxide-cGMP, and prostacyclin pathways (see Choose Initial Treatment) |
| Group 2 — PH due to left heart disease | Heart failure with preserved or reduced ejection fraction; valvular heart disease; congenital/acquired conditions causing postcapillary PH | Treat the underlying cardiac disease and optimize filling pressures — PAH-specific vasodilators are not recommended and can cause harm (see Choose Initial Treatment) |
| Group 3 — PH due to lung disease and/or hypoxia | Obstructive lung disease, restrictive lung disease, mixed patterns, hypoxia without intrinsic lung disease, developmental lung disorders | Optimize the underlying lung disease and correct hypoxemia — PAH-specific vasodilators are not recommended outside a narrow, specialist-directed exception (see Choose Initial Treatment) |
| Group 4 — PH due to pulmonary artery obstruction | Chronic thromboembolic PH (CTEPH) and other pulmonary artery obstructions | A distinct, potentially curable pathway — pulmonary endarterectomy for operable disease, with riociguat and balloon pulmonary angioplasty for inoperable or residual disease (see Choose Initial Treatment) |
| Group 5 — PH with unclear or multifactorial mechanisms | Hematologic disorders, systemic and metabolic disorders, complex congenital heart disease, and others | Individualized to the underlying cause; PAH-specific therapy is not routinely supported |
Recognize the Condition
Symptoms — nonspecific and easy to miss early
The hallmark early symptom of PH, across every group, is exertional dyspnea — breathlessness disproportionate to exertion that progresses gradually and is easy to misattribute to deconditioning, aging, obesity, or a more common cardiopulmonary diagnosis. Fatigue is similarly common and similarly nonspecific. Because right ventricular reserve can compensate for rising afterload for a long time before symptoms clearly localize to the heart, the interval between symptom onset and a confirmed diagnosis is often measured in months rather than days — which is exactly why unexplained, progressive exertional dyspnea without an obvious alternative explanation deserves a deliberate diagnostic pathway (see Assessment & Diagnosis) rather than a reflexive trial of an inhaler or a reassurance visit.
Symptoms that signal more advanced disease
- Exertional syncope or presyncope — reflects an inability to augment cardiac output during exertion and is a genuinely worrying symptom that should prompt urgent evaluation (see Red Flags & Refer), not reassurance.
- Exertional chest pain/angina — right ventricular ischemia from a mismatch between oxygen demand and a compromised right coronary supply as RV pressure rises.
- Peripheral edema, abdominal distension, and early satiety — signs of right heart failure and hepatic/gut venous congestion as disease advances.
- Palpitations, and in advanced disease, cyanosis.
Examination findings
- A loud, sometimes palpable P2 (pulmonary component of the second heart sound) — the most specific bedside sign of elevated pulmonary artery pressure.
- A right ventricular heave along the left sternal border.
- A holosystolic tricuspid regurgitation murmur at the left lower sternal border that characteristically increases with inspiration.
- Elevated jugular venous pressure with a prominent "a" wave (reflecting a stiff, hypertrophied right ventricle), progressing to signs of overt right heart failure — peripheral edema, ascites, hepatomegaly, a pulsatile liver — as disease advances.
Risk Factors
Risk factors specific to PAH (Group 1)
- Heritable PAH — most often due to a BMPR2 mutation; offer genetic counseling, and consider a cascade-screening discussion for affected families once heritable PAH is identified.
- Drug- and toxin-induced PAH — recognized associations include appetite-suppressant drugs (the fenfluramine-class agents withdrawn decades ago remain relevant to a remote history), methamphetamine use, and specific targeted cancer therapies including the tyrosine kinase inhibitor dasatinib.
- Connective tissue disease — especially systemic sclerosis, which carries the highest PAH prevalence of any CTD and is the only condition with a dedicated, validated screening algorithm (DETECT; see Assessment & Diagnosis).[1]
- HIV infection, portal hypertension (portopulmonary hypertension), and congenital heart disease — each carries a meaningfully higher PAH prevalence than the general population and may warrant targeted echocardiographic screening.[1]
- Schistosomiasis — a leading global cause of PAH, most relevant with a history of residence in or travel to endemic regions.
Risk factors for the other, far more common PH groups
- Group 2 (left heart disease) — hypertension, coronary artery disease, valvular heart disease, obesity, diabetes, and obstructive sleep apnea are all risk factors for the heart failure and valvular disease that drive this — by far the most common — cause of PH.
- Group 3 (lung disease/hypoxia) — COPD, interstitial lung disease, obstructive sleep apnea and other sleep-disordered breathing, chronic hypoventilation, and chronic residence at high altitude.
- Group 4 (CTEPH) — a prior acute pulmonary embolism is the single most important risk factor, though a substantial proportion of CTEPH patients have no documented prior PE.[1]
Red Flags & Refer
Any of the following moves a patient from routine outpatient follow-up to urgent, PH-centre-level assessment:
- Exertional or unexplained syncope/presyncope in a patient with known or suspected PH — reflects an inability to augment cardiac output and marks high-risk disease, not a benign vasovagal event.
- New or worsening signs of right heart failure — peripheral edema, ascites, rapid weight gain, or a distended, pulsatile liver — can represent decompensated RV failure requiring urgent reassessment and possible hospitalization.
- Rapidly progressive dyspnea or new hypoxemia — do not attribute this to gradual disease progression without urgent assessment; it may reflect decompensation, a new pulmonary embolism, an arrhythmia, or infection.
- New pulmonary edema shortly after starting a calcium channel blocker or a PAH-specific vasodilator — a genuinely important, easy-to-miss red flag for occult pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis (PVOD/PCH), a PAH subtype in which these same therapies can precipitate life-threatening pulmonary edema. Do not simply increase the dose — stop escalation and arrange urgent PH-centre reassessment (see Special Populations).
- Any unplanned interruption in a continuous parenteral prostacyclin infusion (epoprostenol or treprostinil) — treat this as a medical emergency; the extremely short half-life of these agents means abrupt cessation can cause rapid, severe rebound PH and death (see Choose Initial Treatment).
- Suspected new CTEPH — persistent dyspnea or exercise intolerance beyond 3 months of appropriately anticoagulated acute pulmonary embolism warrants echocardiography and a ventilation/perfusion scan.[1]
Assessment & Diagnosis
Step 1 — Echocardiography establishes the initial probability of PH
Transthoracic echocardiography (TTE) is recommended as the initial test in every patient with clinically suspected PH or otherwise-unexplained dyspnea.[1] A complete assessment estimates systolic pulmonary artery pressure from the tricuspid regurgitation jet velocity and estimated right atrial pressure, and evaluates "secondary" signs of PH — right atrial and right ventricular enlargement, right ventricular hypertrophy, interventricular septal flattening, and right ventricular dysfunction.[1] TTE is also central to distinguishing a precapillary from a postcapillary process: left ventricular hypertrophy, systolic or diastolic dysfunction, significant aortic or mitral valve disease, and an enlarged left atrium all point toward Group 2 (left heart disease) PH, while a severely dilated, remodelled right ventricle without left-sided pathology points toward a precapillary cause.[1] A normal echocardiogram does not reliably exclude postcapillary PH related to left heart disease, which is one of several reasons TTE alone can never substitute for right heart catheterization.[1]
Step 2 — Excluding the more common causes before landing on PAH
PAH is, in practice, a diagnosis reached by systematically excluding the far more common causes of PH: pulmonary function testing and HRCT chest to evaluate for significant lung disease (Group 3), the echocardiographic and clinical assessment above for left heart disease (Group 2), and ventilation/perfusion (V/Q) scanning to screen for CTEPH (Group 4) — the single most sensitive test for this purpose, where a normal perfusion scan effectively rules out CTEPH but a negative CT pulmonary angiogram does not.[1] Serologic screening for connective tissue disease and a directed history for HIV risk, portal hypertension, congenital heart disease, drug/toxin exposure, and family history complete the initial work-up.
Step 3 — Right heart catheterization confirms the diagnosis
RHC is required in every patient with suspected PAH or CTEPH to confirm the hemodynamic diagnosis of precapillary PH and to establish its severity, and should be performed only in centres with the technical expertise to avoid measurement error that can alter both PH classification and treatment choice.[1] Rigorous technique matters: the pressure transducer should be positioned at mid-thoracic height, and pressures — including wedge pressure — should be read at end-expiration from several respiratory cycles rather than relying on a device's automated digital estimate, since this alone can change PH classification in 25-30% of patients.[1] Thermodilution is the preferred method for cardiac output because it correlates best with right ventricular function and outcomes.[1] See Clinical Snapshot for the current mPAP >20 mmHg, PAWP ≤15 mmHg, PVR >2 Wood unit hemodynamic definition of PAH.
Acute vasodilator testing
Acute vasodilator testing at the time of RHC — using inhaled nitric oxide, intravenous epoprostenol, or adenosine — is essential in patients with suspected idiopathic, heritable, or drug/toxin-induced PAH, since it identifies the roughly 10-15% of these patients with marked short-term hemodynamic responsiveness (a fall in mPAP of at least 10 mmHg to below 40 mmHg with a stable or increased cardiac output) who are candidates for high-dose calcium channel blocker therapy instead of standard PAH-targeted therapy (see Choose Initial Treatment).[1]
Targeted screening in high-risk groups
Annual echocardiography and DLCO measurement is recommended to screen for PH in every patient with systemic sclerosis, given the disproportionate PAH prevalence in this group; the DETECT algorithm — a validated two-step decision tree incorporating clinical, serologic, and pulmonary-function variables — improves the sensitivity of identifying PAH in scleroderma from roughly 71% to 96% compared with unstructured screening.[1] Echocardiography is also recommended in every patient with portal hypertension being assessed for liver transplantation, since moderate-to-severe portopulmonary hypertension is a contraindication to transplant (see Special Populations).[1]
Treatment Targets
Framing what PAH-specific therapy can and cannot achieve avoids a difficult later conversation: for most patients with PAH, current pharmacotherapy is not curative. The treatment goal is to reduce symptoms, improve functional capacity and exercise tolerance, delay clinical worsening (hospitalization, need for treatment escalation, or death), and — most central to the modern treatment paradigm — achieve and then maintain a low-risk clinical profile using the multiparametric risk-stratification tools in Choose Initial Treatment, since patients who reach and sustain low-risk status have consistently better long-term survival than those who do not.[1]
- The genuine exception: the roughly 10-15% of idiopathic, heritable, or drug/toxin-induced PAH patients with a marked acute vasodilator response can achieve long-term survival exceeding 95% at 5 years on high-dose calcium channel blocker therapy alone — a meaningfully better prognosis than the general PAH population, and a strong reason acute vasodilator testing is performed in every eligible patient (see Assessment & Diagnosis and Choose Initial Treatment).[1]
- For Group 2 and Group 3 PH, the treatment target is entirely different: optimizing the underlying left heart or lung disease, not treating the pulmonary pressure itself (see Choose Initial Treatment).
- For Group 4 CTEPH, pulmonary endarterectomy offers a realistic prospect of cure in operable disease — a genuinely different, more optimistic target than for Group 1 PAH.
Choose Initial Treatment
Every patient with confirmed or strongly suspected PAH should be assessed in a recognized PH centre to confirm the diagnosis, direct the choice of PH-targeted therapy, and evaluate the response to treatment.[1] These medications are expensive, carry real toxicity, and — as detailed below — can cause serious harm if started in the wrong patient (the wrong PH group, or a non-vasoresponder given high-dose calcium channel blockers). This is not a drug class to initiate empirically outside specialist care.
High-dose calcium channel blockers (amlodipine or diltiazem) are appropriate only for the roughly 10-15% of idiopathic, heritable, or drug/toxin-induced PAH patients who demonstrate a marked acute vasodilator response on RHC — a fall in mPAP of at least 10 mmHg to below 40 mmHg with a stable or increased cardiac output.[1] Initiation, uptitration, and confirmation of a sustained low-risk clinical and hemodynamic response all require a PH expert centre; the same high-dose therapy is dangerous and contraindicated in a non-responder, where it can precipitate hypotension and right ventricular failure.[1] Do not start a calcium channel blocker for "pulmonary hypertension" without a documented positive vasodilator response — this is one of the most consequential and avoidable errors in PAH management (see Common Errors to Avoid).
For patients who are not acute vasodilator responders, a multiparametric risk assessment at diagnosis — combining functional class, exercise capacity, natriuretic peptides, and hemodynamic/imaging measures of right heart function — stratifies patients into low, intermediate, and high risk, and is the single most important determinant of how intensively to start treatment.[1] Parameters used include WHO/NYHA functional class, presence of clinical right heart failure, syncope, rate of symptom progression, 6-minute walk distance, BNP/NT-proBNP, right atrial pressure, cardiac index, mixed venous oxygen saturation, echocardiographic/CMR right atrial area, pericardial effusion, and cardiopulmonary exercise testing parameters where available.[1] The 2022 ESC/ERS international guideline formalizes this into a comprehensive 3-strata model at diagnosis (up to 18 parameters, mapping to estimated 1-year mortality of under 5%, 5-20%, and over 20% for low, intermediate, and high risk respectively) and a simplified 4-strata model — low, intermediate-low, intermediate-high, and high risk, based on functional class, 6-minute walk distance, and BNP/NT-proBNP — for use at follow-up visits.[2] The REVEAL 2.0 risk score and its abridged version, REVEAL Lite 2, are validated alternative numeric calculators developed from North American PAH registry data and are increasingly used alongside the ESC/ERS-based approach.[3][4]
Low risk, treatment-naive: initial oral monotherapy with an endothelin receptor antagonist (ERA), a PDE5 inhibitor, or the soluble guanylate cyclase (sGC) stimulator riociguat is an acceptable, guideline-supported starting point.[1]
Intermediate risk, treatment-naive: initial dual oral combination therapy — an ERA plus a PDE5 inhibitor — is now recommended rather than starting with a single agent.[1] This is a genuine, evidence-driven shift from the historical monotherapy-first approach: the randomized AMBITION trial found that initial combination therapy with ambrisentan and tadalafil reduced the risk of a composite clinical-failure endpoint (death, hospitalization for worsening PAH, disease progression, or unsatisfactory long-term response) by roughly 50% compared with pooled monotherapy.[5] No head-to-head trials define one combination as superior to another, and other ERA/PDE5-inhibitor pairings are reasonable, though less directly supported by trial evidence than ambrisentan plus tadalafil specifically.[1]
High risk, including WHO/NYHA functional class IV: initial combination therapy that includes a parenteral prostacyclin is recommended — intravenous epoprostenol carries the stronger recommendation, with subcutaneous or intravenous treprostinil as an alternative.[1] This population should not be started on oral therapy alone.
At every risk level: reassess within 3-4 months of starting or changing therapy, and regularly thereafter (every 6-12 months once low-risk status is achieved and maintained, depending on access to a PH centre).[1] If low-risk status is not achieved, escalate rather than waiting (see Treatment Failure/Next Step).
Mechanism: PAH is associated with elevated endothelin-1, a potent vasoconstrictor and smooth-muscle mitogen; ERAs block its receptor-mediated effects.[1] Three oral agents are available in Canada.
Bosentan: 62.5 mg PO twice daily for 4 weeks, then increase to the 125 mg PO twice daily maintenance dose.[6] Bosentan is the one ERA that requires mandatory monthly liver aminotransferase monitoring for the full duration of treatment, reflecting a dose-dependent hepatotoxicity risk (ALT/AST rising to at least 3 times the upper limit of normal in roughly 11% of trial patients).[6] It is contraindicated with cyclosporine (co-administration increased bosentan trough levels roughly 30-fold in a formal interaction study) and with glyburide (increased risk of liver enzyme elevation with both agents together) — confirm the full medication list before starting.[6]
Ambrisentan: 5 mg PO once daily, may be increased to 10 mg PO once daily. Peripheral edema/fluid retention is more prominent with ambrisentan than with the other ERAs.
Macitentan: 10 mg PO once daily, a single fixed dose with no titration required.[7] Macitentan is the one ERA with randomized-trial evidence of a reduction in a composite morbidity/mortality endpoint (the SERAPHIN trial, comparing macitentan against placebo in an event-driven design).[8]
Class effects: all three ERAs are teratogenic and contraindicated in pregnancy — confirm a negative pregnancy test before starting in anyone of reproductive potential, repeat monthly during treatment, and ensure effective, non-hormonal-inclusive contraception is in place and reviewed at every visit (see Non-Pharmacologic Treatment and Special Populations). Anemia is a recognized class effect and hemoglobin should be checked periodically.
Mechanism: both act on the nitric oxide-cGMP pathway, which is deficient in PAH. Phosphodiesterase type-5 (PDE5) inhibitors — sildenafil (20 mg PO three times daily) and tadalafil (40 mg PO once daily) — block the breakdown of cGMP generated downstream of endogenous nitric oxide.[1] Riociguat works differently and more directly: it is a soluble guanylate cyclase (sGC) stimulator that both sensitizes sGC to low levels of endogenous nitric oxide and stimulates it directly, independent of nitric oxide availability — part of why it also has a distinct, dedicated indication in CTEPH (see below).[1] Riociguat requires a careful, individualized uptitration: starting at 1 mg PO three times daily, increased by 0.5 mg three times daily no more often than every 2 weeks based on systolic blood pressure and tolerability, up to a maximum of 2.5 mg three times daily (maximum total daily dose 7.5 mg), typically over about 8 weeks.[9][1]
The critical interaction: a PDE5 inhibitor and riociguat must never be used together — both converge on the same NO-cGMP pathway, and the combination is contraindicated because of a real risk of clinically significant, symptomatic systemic hypotension.[1][9] If switching a patient from a PDE5 inhibitor to riociguat, discontinue sildenafil at least 24 hours, or tadalafil at least 48 hours, before the first riociguat dose.[9] Both classes are separately contraindicated with organic nitrates and with recreational nitrate use ("poppers") for the same additive-hypotension reason — ask directly, since patients may not volunteer recreational drug use unprompted.[9]
Mechanism: patients with PAH have deficient endogenous prostacyclin; these agents replace that pathway, producing vasodilation along with antiplatelet and antiproliferative effects.[1]
Intravenous epoprostenol is the preferred agent for high-risk, including WHO/NYHA functional class IV, patients, and remains the only PAH-targeted agent with randomized-trial evidence of an overall survival benefit as monotherapy in this sickest population.[1] Its extremely short half-life (roughly 6 minutes) is a double-edged feature: it allows rapid, careful dose titration, but also means the drug must be delivered by continuous infusion through a permanent central venous catheter, and any unplanned interruption — a pump failure, a delayed line change, a missed prescription refill — is a genuine medical emergency, since abrupt cessation can cause rapid, severe rebound PH and death.[1] Dosing starts low (approximately 2 ng/kg/min) and is titrated upward based on symptom control and tolerability (flushing, headache, jaw/bone pain, nausea, diarrhea, and catheter-related complications), with no fixed ceiling — many patients are eventually maintained well above 20-40 ng/kg/min after months to years of uptitration.[1]
Treprostinil offers more flexibility across the severity spectrum: continuous subcutaneous infusion avoids the infection risk of an indwelling central catheter (though infusion-site pain is common and can itself limit tolerability), continuous intravenous infusion is available where subcutaneous delivery is not feasible, and inhaled and oral extended-release formulations extend the prostacyclin pathway to patients who are not candidates for continuous parenteral therapy.[1] Subcutaneous/intravenous dosing typically starts around 1.25 ng/kg/min and is titrated by symptoms and tolerability, the same way as epoprostenol.
Selexipag is an oral, non-prostanoid prostacyclin (IP) receptor agonist — mechanistically in the same pathway, but chemically distinct and taken as a tablet, meaningfully lowering the delivery burden compared with the parenteral and inhaled options.[1] Start at 200 mcg PO twice daily, increasing in 200 mcg twice-daily increments approximately weekly, as tolerated, to the individualized highest tolerated maintenance dose, up to a maximum of 1600 mcg twice daily.[10] The randomized GRIPHON trial demonstrated a reduction in a composite morbidity/mortality endpoint with selexipag; adverse effects (headache, jaw/bone pain, flushing, diarrhea, nausea) are dose-related, prostacyclin-class-typical, and generally most prominent during uptitration.[11]
Inhaled iloprost is a further option in this pathway, though its short duration of action requires 6-9 nebulized doses daily — a genuinely significant adherence burden compared with the other agents in this class.
Group 2 (left heart disease): there is no evidence to support PAH-targeted therapy in PH due to left heart disease, and PAH-specific agents have instead been associated with systemic hypotension, fluid retention, pulmonary edema, and increased mortality when used in this population.[1] Management should instead focus on optimizing ventricular filling pressures and treating the underlying cardiac disease — valvular intervention, cardiac resynchronization therapy, guideline-directed heart failure therapy, and volume management, as applicable.[1]
Group 3 (lung disease/hypoxia): published experience with PAH-targeted drugs in this group is scarce, and there is no evidence of improved clinical outcomes; because these agents are not selective for the pulmonary vasculature supplying well-ventilated lung units, a real potential risk is worsening ventilation-perfusion matching and therefore worsening hypoxemia.[1] This is not merely a theoretical concern — the randomized RISE-IIP trial of riociguat in patients with PH associated with idiopathic interstitial pneumonia (a common Group 3 substrate) was stopped early because of an increased risk of serious adverse events and death in the riociguat arm, a genuine demonstration of harm rather than simple lack of benefit.[12] Routine RHC and PAH-targeted therapy are not recommended in mild-to-moderate Group 3 PH without right ventricular failure; refer moderate-to-severe Group 3 PH, or Group 3 PH with RV failure, to a PH centre for individualized assessment rather than either ignoring it or empirically starting PAH therapy.[1] The 2022 ESC/ERS guideline carves out one narrow, evolving exception — a PDE5 inhibitor may be considered specifically in severe PH associated with interstitial lung disease, with individualized decision-making at a PH centre — but this is a specialist-directed exception, not a default approach.[2]
Chronic thromboembolic PH is common, under-recognized when a prior pulmonary embolism history is absent (as it is in 30-50% of CTEPH patients), and — unlike Groups 2 and 3 — treatable and potentially curable, which is why it must always be actively excluded (with V/Q scanning) rather than assumed away.[1] Pulmonary endarterectomy (PEA), performed by a multidisciplinary team including an experienced PEA surgeon, is the treatment of choice for operable disease and now carries a mortality of only 1-2% at experienced centres.[1] For patients with inoperable disease, or with residual/recurrent PH after PEA, riociguat monotherapy is recommended — riociguat's other, distinct Health Canada indication, and an important nuance: this is the one situation outside Group 1 PAH where a PAH-class drug is guideline-recommended, precisely because CTEPH has its own dedicated trial evidence that Groups 2 and 3 do not.[1] Balloon pulmonary angioplasty is a reasonable option for patients ineligible for, or declining, PEA. Lifelong anticoagulation is required in every CTEPH patient regardless of which of these treatments is used.[1]
Anticoagulation: warfarin (INR target 2-3) is a reasonable, guideline-supported option in selected idiopathic, heritable, or drug/toxin-induced PAH patients without an elevated bleeding risk, reflecting evidence of in-situ pulmonary arterial thrombosis in this population — though no randomized trial has confirmed benefit, and registry data have raised questions about the practice.[1] Anticoagulation is specifically not recommended in PAH associated with connective tissue disease, congenital heart disease, portal hypertension, or HIV, given an unfavourable bleeding-risk balance in these subgroups.[1] There are no studies supporting a direct oral anticoagulant for PAH-specific anticoagulation — warfarin remains the guideline-supported choice where anticoagulation is indicated for PAH itself (see Common Errors to Avoid).[1]
Diuretics: carefully titrated diuretic therapy — furosemide is typical — reduces fluid overload from right heart failure; individualize to volume status and renal function rather than a fixed dose.[1]
Oxygen: long-term oxygen therapy is recommended for resting hypoxemia, and should be reassessed for exertional hypoxemia as well; treat this the same as any other chronic hypoxemic lung/cardiac condition rather than a PAH-specific consideration.[1]
Non-Pharmacologic Treatment
General supportive measures and education
Every PAH patient should receive disease-specific education, psychosocial support, and structured, supervised exercise rehabilitation, which improves functional capacity and health-related quality of life.[1]
Contraception and pregnancy planning — a genuinely high-stakes counseling point
Pregnancy in PAH carries a well-documented, high maternal mortality risk and is generally strongly discouraged; reliable contraception should be discussed proactively with every patient of reproductive potential, not deferred until pregnancy is raised by the patient.[1] This is inseparable from the pharmacotherapy in Choose Initial Treatment: ERAs, riociguat, and selexipag are all teratogenic, and women of childbearing age taking any of them should stop the medication before attempting conception and use effective, non-hormonal-inclusive contraception in the meantime.[2]
Vaccination and infection prevention
Keep routine immunization current, with particular attention to annual influenza and age-appropriate pneumococcal vaccination — a respiratory infection is a recognized precipitant of acute right heart decompensation in a patient with limited RV reserve.
Activity, altitude, and travel
Encourage regular, moderate activity within symptom limits (formal rehabilitation above is preferred where available) while counseling against strenuous isometric exertion; discuss oxygen planning for air travel and avoidance of unpressurized high-altitude exposure given the added hypoxic stress on an already-compromised pulmonary circulation.
Genetic counseling
Offer genetic counseling, and discuss cascade testing of first-degree relatives, once heritable PAH (most often a BMPR2 mutation) is identified.
Advance care planning
Despite genuine treatment advances, prognosis remains guarded for many patients, particularly those who do not achieve a sustained low-risk profile; integrate goals-of-care conversations and palliative care alongside disease-directed therapy as risk status and functional class decline, rather than reserving these conversations for the final stages of disease.
Special Populations
Pregnancy
PAH carries a well-documented, high maternal mortality risk, and pregnancy is generally strongly discouraged; when pregnancy does occur, management requires a specialized, multidisciplinary high-risk obstetric/PH-centre team.[1] ERAs, riociguat, and selexipag are teratogenic and should be stopped, with any switch to a therapy with more reassuring (though still limited) safety data — chiefly the PDE5 inhibitors — made under specialist direction rather than as a default choice.[2]
Connective-tissue-disease-associated PAH (especially systemic sclerosis)
The highest-prevalence PAH subgroup, and the only one with a dedicated, validated screening algorithm (DETECT; see Assessment & Diagnosis).[1] Anticoagulation is specifically not recommended in this group, in contrast to idiopathic/heritable/drug-toxin PAH (see Choose Initial Treatment).[1]
Portopulmonary hypertension
Associated with poor prognosis if untreated, with 5-year survival reported as low as 14% in some series in the absence of medical therapy.[1] Moderate-to-severe portopulmonary hypertension is a contraindication to liver transplantation — a genuinely high-stakes, easy-to-miss fact — which is why echocardiographic screening is recommended in every portal hypertension patient being assessed for transplant.[1] Anticoagulation is not recommended in this group given bleeding risk from portal-hypertension-related varices.[1]
HIV-associated and congenital-heart-disease-associated PAH
HIV-associated PAH has a prevalence of roughly 0.5%, still meaningfully above the general population, and echocardiography is reasonable in patients with unexplained dyspnea or multiple HIV-PAH risk factors.[1] Nearly 10% of adult congenital heart disease patients may have PAH, and screening should be performed at centres with adult CHD expertise.[1] Anticoagulation is not recommended in either subgroup (see Choose Initial Treatment).[1]
Pulmonary veno-occlusive disease/pulmonary capillary hemangiomatosis (PVOD/PCH)
A PAH subtype that can closely mimic idiopathic PAH clinically but carries a distinct, dangerous risk: standard PAH vasodilator and calcium-channel-blocker therapy can precipitate life-threatening pulmonary edema in these patients. New or worsening pulmonary edema shortly after starting either class of therapy should prompt urgent reassessment for PVOD/PCH rather than dose escalation (see Red Flags & Refer).
Lung and heart-lung transplantation
Refer PAH or CTEPH patients with persistent severe PH (WHO/NYHA functional class III-IV and/or right ventricular failure) despite maximal medical therapy for lung transplant assessment, and consider extracorporeal life support as a bridge in patients with refractory RV failure or hemodynamic instability.[1] Unlike some other progressive cardiopulmonary diseases, PAH-directed pharmacotherapy is not itself curative for most patients outside the calcium-channel-blocker-responder subgroup, so transplant referral timing should not be deferred while additional medical options are still being tried indefinitely.
Monitoring & Follow-Up
- Reassess within 3-4 months of starting or changing any PAH-targeted therapy, and every 6-12 months once a low-risk profile is achieved and sustained, depending on access to a PH centre.[1]
- Repeat the multiparametric risk assessment (functional class, 6-minute walk distance, natriuretic peptides, and hemodynamic/imaging measures where available) at each visit — track the trajectory toward or away from low-risk status rather than relying on a single snapshot.[1]
- Bosentan: monthly ALT/AST for the entire duration of treatment — this is a mandatory, not optional, monitoring requirement.[6]
- Ambrisentan and macitentan: periodic liver enzyme and hemoglobin monitoring is reasonable clinical practice, though not mandated to the same monthly schedule as bosentan.
- Riociguat: monitor blood pressure closely throughout the uptitration period, particularly with any background vasodilator use.[9]
- Selexipag: anticipate and proactively manage dose-related, prostacyclin-class adverse effects (headache, jaw/bone pain, flushing, GI upset) during uptitration rather than treating them as a reason to abandon therapy.[10]
- Epoprostenol and treprostinil: meticulous, ongoing monitoring of the infusion system, catheter site, and pump — including a confirmed backup plan for pump failure or line change — is part of routine follow-up, not a one-time education session at initiation.[1]
- Monthly pregnancy testing for anyone of reproductive potential taking an ERA, riociguat, or selexipag, alongside a standing contraception review at every visit.[2]
- Routine INR monitoring for any patient on warfarin for PAH-specific anticoagulation.
- Resting and exertional oxygen saturation at follow-up visits to guide oxygen therapy.
- Confirm annual influenza and age-appropriate pneumococcal vaccination status.
Common Errors to Avoid
- Combining a PDE5 inhibitor with riociguat — this is contraindicated and can cause serious symptomatic hypotension (see Choose Initial Treatment).[9]
- Prescribing a PDE5 inhibitor or riociguat without asking directly about nitrate use, including recreational nitrate ("poppers") use — the interaction is the same additive-hypotension mechanism, and patients may not volunteer this history unprompted.[9]
- Starting a high-dose calcium channel blocker for "pulmonary hypertension" without a documented positive acute vasodilator response on RHC — this can be dangerous, even fatal, in a non-responder (see Choose Initial Treatment).[1]
- Starting any PAH-specific vasodilator in a patient whose PH is actually due to left heart disease (Group 2) or lung disease/hypoxia (Group 3) without RV failure — there is no evidence of benefit and real evidence of harm in both groups (see Choose Initial Treatment).[1][12]
- Prescribing a direct oral anticoagulant (apixaban, rivaroxaban, or similar) as PAH-specific anticoagulation — there is no supporting evidence for this in PAH; warfarin remains the guideline-supported choice where anticoagulation is indicated specifically for PAH.[1]
- Anticoagulating connective-tissue-disease-, HIV-, portal-hypertension-, or congenital-heart-disease-associated PAH the same way as idiopathic PAH — the guideline recommends against routine anticoagulation in these specific subgroups (see Special Populations).[1]
- Treating new pulmonary edema after starting a vasodilator or calcium channel blocker as simple drug intolerance rather than a red flag for occult PVOD/PCH.
- Allowing any interruption in a continuous IV epoprostenol infusion to go unaddressed — its roughly 6-minute half-life means abrupt cessation can cause rapid, severe rebound PH and death.[1]
- Skipping bosentan's mandatory monthly liver enzyme monitoring, or applying its monthly schedule loosely to ambrisentan or macitentan (or vice versa) — the monitoring intensity genuinely differs by agent.[6]
- Listing a portopulmonary hypertension patient for liver transplant without addressing moderate-to-severe PH first — it is a contraindication to transplant until adequately treated.[1]
- Treating oral monotherapy as a permanent, "set and forget" plan — low-risk patients still need scheduled reassessment, and most contemporary intermediate- or high-risk patients need initial combination therapy rather than a monotherapy trial first.[1]
- Deferring lung transplant referral until no medical options remain, rather than referring once persistent severe PH or RV failure is established despite maximal therapy.[1]
Clinical Decision Algorithm
Drug Tables
Endothelin Receptor Antagonists (ERAs)
Block endothelin-1-mediated vasoconstriction and smooth-muscle proliferation. All three are teratogenic and require monthly pregnancy testing and effective contraception in anyone of reproductive potential. See Choose Initial Treatment for the full risk-based combination-therapy rationale.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Bosentan | 62.5 mg PO twice daily x4 weeks, then 125 mg PO twice daily maintenance | Dose-dependent hepatotoxicity (ALT/AST at least 3x ULN in ~11% of trial patients), peripheral edema, anemia, teratogenicity | Contraindicated with cyclosporine (bosentan levels increased ~30-fold) and glyburide (increased hepatotoxicity risk); reduces hormonal contraceptive and warfarin effect via CYP3A4/CYP2C9 induction | The only ERA with a mandatory monthly liver-enzyme monitoring requirement for the full duration of treatment |
| Ambrisentan | 5 mg PO once daily, may increase to 10 mg once daily | Peripheral edema/fluid retention (more prominent than other ERAs), anemia, teratogenicity | Fewer clinically significant CYP interactions than bosentan | The ERA studied together with tadalafil in the AMBITION upfront-combination trial |
| Macitentan | 10 mg PO once daily — single fixed dose, no titration | Anemia, headache, nasopharyngitis, teratogenicity | Fewer clinically significant CYP interactions than bosentan | The only ERA with randomized-trial evidence of a reduced composite morbidity/mortality endpoint (SERAPHIN) |
Nitric Oxide-cGMP Pathway: PDE5 Inhibitors and the sGC Stimulator Riociguat
PDE5 inhibitors and riociguat both act on the nitric oxide-cGMP pathway and must never be combined with each other or with any nitrate — the combination carries a real risk of severe, symptomatic systemic hypotension.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Sildenafil | 20 mg PO three times daily | Headache, flushing, dyspepsia, epistaxis, visual disturbance | Contraindicated with riociguat and with any nitrate (severe hypotension); avoid with strong CYP3A4 inhibitors | PDE5 inhibitor — combination-therapy backbone alongside an ERA for intermediate-risk PAH |
| Tadalafil | 40 mg PO once daily | Headache, flushing, myalgia, back pain, dyspepsia | Contraindicated with riociguat and with any nitrate (severe hypotension) | Once-daily PDE5 inhibitor; the agent studied together with ambrisentan in the AMBITION trial |
| Riociguat | Start 1 mg PO three times daily; titrate by 0.5 mg three times daily no more often than every 2 weeks, by systolic BP and tolerability, to a maximum of 2.5 mg three times daily (maximum total daily dose 7.5 mg) | Hypotension, headache, dyspepsia, peripheral edema, hemoptysis, gastritis | Contraindicated with any PDE5 inhibitor and with any nitrate/nitric oxide donor (severe hypotension); switching from a PDE5 inhibitor requires a washout (24h+ sildenafil, 48h+ tadalafil) | The one PAH-class agent with a second, distinct indication in inoperable or residual/recurrent CTEPH |
Prostacyclin Pathway Agents
Replace deficient endogenous prostacyclin, producing vasodilation plus antiplatelet and antiproliferative effects. Reserved for higher-risk PAH; delivery method (continuous parenteral, inhaled, or oral) is itself a major treatment decision — see Choose Initial Treatment.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Epoprostenol | Continuous IV infusion via a permanent central venous catheter; start ~2 ng/kg/min, titrate upward by symptoms/tolerability with no fixed ceiling | Flushing, headache, jaw/bone pain, nausea, diarrhea, catheter-related infection, rebound PH with interruption | Additive hypotension with other vasodilators | ~6-minute half-life — any unplanned infusion interruption is a medical emergency; the only PAH agent with RCT-demonstrated survival benefit as monotherapy in the highest-risk population |
| Treprostinil | SC/IV: start ~1.25 ng/kg/min, titrate by symptoms; also available as inhaled and oral extended-release formulations | Infusion-site pain (SC, often treatment-limiting), flushing, headache, jaw pain, diarrhea | Additive hypotension with other vasodilators | SC delivery avoids the infection risk of an indwelling central catheter; the most delivery-flexible agent in this pathway |
| Selexipag | Start 200 mcg PO twice daily; increase by 200 mcg twice-daily increments approximately weekly, as tolerated, to a maximum of 1600 mcg twice daily | Headache, jaw/bone pain, flushing, diarrhea, nausea — dose-related, most prominent during uptitration | Avoid strong CYP2C8 inhibitors/inducers, which affect levels of the active metabolite | Oral, non-prostanoid IP-receptor agonist; reduced a composite morbidity/mortality endpoint in the GRIPHON trial |
| Iloprost | Inhaled, 2.5-5 mcg via nebulizer, 6-9 times daily | Flushing, headache, jaw/bone pain, cough, nausea | Additive hypotension with other vasodilators | Short duration of action requires frequent daily nebulized dosing — a genuine adherence burden; not currently published in the Pharmasist Drug Database |
Calcium Channel Blockers — Confirmed Acute Vasodilator Responders Only
Appropriate only for the roughly 10-15% of idiopathic, heritable, or drug/toxin-induced PAH patients with a documented positive acute vasodilator response on RHC. Dangerous and contraindicated in a non-responder.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Diltiazem | High-dose, individualized and uptitrated in a PH expert centre | Hypotension, bradycardia, peripheral edema — dangerous in a non-vasoresponder | Additive bradycardia/hypotension with other rate- or pressure-lowering agents | Appropriate only for confirmed acute vasodilator responders (see Choose Initial Treatment) |
| Amlodipine | High-dose, individualized and uptitrated in a PH expert centre | Hypotension, peripheral edema — dangerous in a non-vasoresponder | Additive hypotension with other vasodilators | An alternative to diltiazem for confirmed vasoresponders; not currently published as a standalone monotherapy entry in the Pharmasist Drug Database |
Supportive Therapy
Anticoagulation, diuretics, and oxygen are individualized to PAH subtype and clinical status rather than given routinely to every patient — see Choose Initial Treatment for which PAH subgroups should, and should not, receive anticoagulation.
| Drug | Dosage | Adverse effects | Drug interactions | Comments |
|---|---|---|---|---|
| Warfarin | Individualized to target INR 2-3 | Bleeding | Numerous — confirm the full medication list, including any interacting ERA (bosentan reduces warfarin effect via CYP induction) | Reasonable only in selected idiopathic, heritable, or drug/toxin-induced PAH without elevated bleeding risk; not recommended in CTD-, HIV-, portal-hypertension-, or CHD-associated PAH |
| Furosemide | Individualized to volume status and renal function | Electrolyte disturbance, renal function changes, hypotension | Additive hypotension with PAH-specific vasodilators | Titrate carefully — both under- and over-diuresis can worsen right ventricular filling and cardiac output |
References
- Canadian Cardiovascular Society/Canadian Thoracic Society Position Statement on Pulmonary Hypertension — Canadian Cardiovascular Society/Canadian Thoracic Society Pulmonary Hypertension Committee (Hirani N, Brunner NW, Kapasi A, Chandy G, Rudski L, Paterson I, Langleben D, Mehta S, Mielniczuk L). Can J Cardiol 2020;36(7):977-992
- 2022 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension — European Society of Cardiology/European Respiratory Society (Humbert M, Kovacs G, Hoeper MM, et al.). Eur Heart J 2022;43(38):3618-3731
- Therapy for Pulmonary Arterial Hypertension in Adults: Update of the CHEST Guideline and Expert Panel Report — American College of Chest Physicians (Klinger JR, Elliott CG, Levine DJ, et al.). Chest 2019;155(3):565-586
- Predicting Survival in Patients With Pulmonary Arterial Hypertension: The REVEAL Risk Score Calculator 2.0 and Comparison With ESC/ERS-Based Risk Assessment Strategies — Benza RL, Gomberg-Maitland M, Elliott CG, et al.. Chest 2019;156(2):323-337
- Initial Use of Ambrisentan plus Tadalafil in Pulmonary Arterial Hypertension (AMBITION) — AMBITION Investigators (Galie N, Barbera JA, Frost AE, et al.). N Engl J Med 2015;373(9):834-844
- APO-BOSENTAN (bosentan) Product Monograph — Apotex Inc.. Health Canada Drug Product Database
- OPSUMIT (macitentan) Product Monograph — Janssen Inc.. Health Canada Drug Product Database
- Macitentan and Morbidity and Mortality in Pulmonary Arterial Hypertension (SERAPHIN) — SERAPHIN Investigators (Pulido T, Adzerikho I, Channick RN, et al.). N Engl J Med 2013;369(9):809-818
- ADEMPAS (riociguat) Product Monograph — Bayer Inc.. Health Canada Drug Product Database
- UPTRAVI (selexipag) Product Monograph — Janssen Inc.. Health Canada Drug Product Database
- Selexipag for the Treatment of Pulmonary Arterial Hypertension (GRIPHON) — Sitbon O, Channick R, Chin KM, et al.. N Engl J Med 2015;373(26):2522-2533
- Riociguat for idiopathic interstitial pneumonia-associated pulmonary hypertension (RISE-IIP): a randomised, placebo-controlled phase 2b study — Nathan SD, Behr J, Collard HR, et al.. Lancet Respir Med 2019;7(9):780-790
Professional reference only. Apply clinical judgment and verify patient-specific decisions against current authoritative guidance and product information.