9.4 Pulmonary Hypertension and Right Ventricular Failure
Key Takeaways
- Pulmonary hypertension is a mean pulmonary artery pressure above 20 mmHg; pre-capillary requires PAOP 15 mmHg or less with PVR above 2 Wood units, isolated post-capillary is PAOP above 15 with PVR 2 or less, and combined pre- and post-capillary PH is PAOP above 15 with PVR above 2.
- PVR in Wood units equals (mean PAP minus PAOP) divided by cardiac output; a diastolic pulmonary gradient of 7 mmHg or more suggests true pulmonary vascular remodeling and is less flow-dependent than the transpulmonary gradient.
- Group 2 PH from left heart disease is the most common form in a cardiac unit and is not treated with PAH-targeted vasodilators, which can precipitate flash pulmonary edema.
- In acute RV failure the treatment order is inverted from LV failure: restore systemic pressure first with norepinephrine or vasopressin to preserve RV coronary perfusion, then unload the pulmonary circulation selectively with inhaled nitric oxide 5-40 ppm or inhaled epoprostenol; phenylephrine raises PVR and is avoided.
- Continuous IV epoprostenol has a 3-6 minute half-life, so an abrupt interruption can cause rebound pulmonary hypertension and death within minutes - the line is dedicated, never flushed, never used for draws, and restarted immediately on the backup pump if it fails.
Defining Pulmonary Hypertension by the Numbers
Test-plan item II.A.4 is one of the most numerically precise items on the CMC blueprint, and it doubles as a pulmonary artery catheter interpretation question — which is why it earns weight in both Domain II and Domain IV.
Pulmonary hypertension (PH) is a mean pulmonary artery pressure (mPAP) above 20 mmHg at rest, measured by right heart catheterization. The threshold moved down from 25 mmHg with the 2022 ESC/ERS guideline and is now standard in US practice as well. An elevated estimated pulmonary artery systolic pressure on echocardiography raises suspicion; it does not establish the diagnosis, because echo systematically over- and under-estimates depending on the tricuspid regurgitant jet quality.
Pre-capillary versus Post-capillary — the High-Yield Distinction
Two additional numbers separate the categories: the pulmonary artery occlusion (wedge) pressure (PAOP) and the pulmonary vascular resistance (PVR).
| Hemodynamic category | mPAP | PAOP | PVR | Meaning |
|---|---|---|---|---|
| Pre-capillary PH | Above 20 mmHg | 15 mmHg or less | Above 2 Wood units | Disease of the pulmonary arterioles or the pulmonary vascular bed (WHO Groups 1, 3, 4) |
| Isolated post-capillary PH (Ipc-PH) | Above 20 mmHg | Above 15 mmHg | 2 Wood units or less | Pure back-pressure from the left heart (WHO Group 2) |
| Combined pre- and post-capillary PH (Cpc-PH) | Above 20 mmHg | Above 15 mmHg | Above 2 Wood units | Left heart disease plus superimposed pulmonary vascular remodeling — worse prognosis, and a decisive variable for LVAD and transplant candidacy |
Supporting calculations:
- PVR (Wood units) = (mPAP - PAOP) / cardiac output in L/min. Multiply by 80 for dyn-s-cm-5; normal is under 2 Wood units, or under about 160 dyn-s-cm-5.
- Transpulmonary gradient (TPG) = mPAP - PAOP. A TPG above 12 mmHg suggests a pulmonary vascular component, but it is sensitive to flow and to PAOP.
- Diastolic pulmonary gradient (DPG) = diastolic PAP - PAOP. A DPG of 7 mmHg or more suggests true pulmonary vascular remodeling and is less affected by stroke volume and by the timing of the PAOP reading.
Traps to avoid at the bedside. Read the PAOP at end-expiration, at the level of the mean of the a-wave, with the transducer at the phlebostatic axis. Over-wedging, reading a mean across the respiratory cycle, high PEEP in a West zone 1 or 2 catheter position, or a large v-wave from mitral regurgitation will all falsify the wedge and can manufacture a false Cpc-PH picture — or hide a true one. When the wedge tracing looks wrong, correlate with the PA diastolic pressure, which normally sits within about 4 mmHg of the PAOP in the absence of pulmonary vascular disease. A PA diastolic-to-wedge gradient that widens over time is itself evidence of a developing pulmonary vascular component.
The Five WHO Groups
| Group | Basis | Hemodynamics | Cardiac-unit examples | Targeted PAH drug therapy? |
|---|---|---|---|---|
| 1 — Pulmonary arterial hypertension (PAH) | Pulmonary arteriopathy | Pre-capillary | Idiopathic, heritable, connective tissue disease (scleroderma), congenital left-to-right shunt and Eisenmenger physiology, drug/toxin (methamphetamine, fenfluramine), HIV, portopulmonary | Yes — this is the group the drugs are approved for |
| 2 — PH due to left heart disease | Back-pressure | Post-capillary, isolated or combined | HFrEF, HFpEF, mitral stenosis and regurgitation, aortic stenosis, restrictive cardiomyopathy — by far the most common PH in a cardiac unit | No — treat the left heart. PAH drugs can precipitate flash pulmonary edema by increasing flow into a ventricle that cannot accept it |
| 3 — PH due to lung disease and/or hypoxia | Hypoxic vasoconstriction, parenchymal loss | Pre-capillary | COPD, interstitial lung disease, obstructive sleep apnea and obesity hypoventilation, chronic high altitude | Generally no; inhaled treprostinil is approved for PH associated with interstitial lung disease |
| 4 — PH due to pulmonary artery obstruction (CTEPH) | Chronic organized thromboembolism | Pre-capillary | The patient still dyspneic 3-6 months after PE — screen with a V/Q scan, not CTPA | Pulmonary thromboendarterectomy is potentially curative; riociguat and balloon pulmonary angioplasty for inoperable or persistent disease |
| 5 — Multifactorial or unclear | Mixed | Variable | Sarcoidosis, hemolytic anemia including sickle cell disease, chronic kidney disease and dialysis, metabolic disorders, fibrosing mediastinitis | Individualized; treat the underlying disorder |
Right heart catheterization in a patient with long-standing heart failure with reduced ejection fraction being evaluated for transplant shows a mean pulmonary artery pressure of 38 mmHg, a pulmonary artery occlusion pressure of 22 mmHg, and a cardiac output of 3.8 L/min. How should the nurse interpret these hemodynamics?
Right Ventricular Failure: Why the Rules Are Different
The right ventricle is a thin-walled (3-5 mm), crescentic, highly compliant volume pump. It generates roughly a quarter of the left ventricle's stroke work at about a fifth of the pressure, is supplied predominantly by the right coronary artery, and — uniquely — is normally perfused during both systole and diastole because RV systolic pressure is far below aortic pressure.
Those features produce three consequences that CMC tests repeatedly:
- The RV tolerates volume far better than pressure. A normal, unconditioned RV cannot acutely generate a mean PA pressure much above 40 mmHg. Acute afterload is what kills it.
- Absolute PA pressure does not tell you how sick the RV is. A chronic PAH patient with a PA systolic pressure of 90 mmHg has a hypertrophied, adapted RV and may be walking the hallway; an acute PE patient with a PA systolic of 55 mmHg may be in extremis. Look instead at RV function, cardiac index, right atrial pressure, the RA/PAOP ratio (above about 0.63 predicts RV failure after LVAD implantation), and the pulmonary artery pulsatility index, PAPi = (PA systolic - PA diastolic) / RA pressure, where low values (roughly under 1.0 in acute MI and under about 1.85 pre-LVAD) predict RV failure.
- When systemic pressure falls, RV perfusion fails. As RV systolic pressure rises toward systemic pressure, RV perfusion becomes diastole-dependent like the LV, and the gradient between aortic root pressure and RV pressure collapses. Systemic hypotension therefore directly causes RV ischemia.
The Spiral and the Findings
Rising afterload leads to RV dilation, tricuspid annular dilation and functional regurgitation, leftward septal shift with pericardial constraint, LV underfilling, falling systemic pressure, reduced RV coronary perfusion, RV ischemia, and further loss of contractility.
Clinical picture: elevated jugular venous pressure with a prominent v-wave, Kussmaul sign, RV heave, loud P2, a systolic murmur that increases with inspiration (Carvallo sign), hepatomegaly with right-upper-quadrant tenderness, ascites and peripheral edema out of proportion to pulmonary congestion, congestive hepatopathy with rising bilirubin and INR, venous-congestion acute kidney injury, and clear lungs with hypoxemia (often from a reopened patent foramen ovale). Hemodynamics: CVP frequently above 15 mmHg and approaching or exceeding the PAOP, low cardiac index, low SvO2, low PAPi.
Why the Treatment Order Is Inverted
In acute LV failure you unload aggressively and a modest fall in blood pressure is acceptable. In acute RV failure systemic hypotension is the enemy, because it removes the RV's own coronary perfusion. So you support the systemic circulation first and unload the pulmonary circulation selectively.
| Goal | Intervention | Doses and targets | Nursing cautions |
|---|---|---|---|
| Optimize — not maximize — preload | Diurese if CVP is high; small 250 mL boluses only if truly hypovolemic | Aim CVP roughly 8-12 mmHg; stop boluses if CVP rises without a rise in cardiac index | Volume loading a dilated RV worsens septal shift, worsens tricuspid regurgitation and lowers output |
| Maintain systemic pressure and RV coronary perfusion | Norepinephrine 0.02-0.5 mcg/kg/min; vasopressin 0.01-0.04 units/min as an adjunct | MAP 65 mmHg or higher, often targeted 70-80 in severe PH | Vasopressin at low dose supports systemic pressure without raising PVR; phenylephrine raises PVR and causes reflex bradycardia and is generally avoided |
| Selectively reduce RV afterload | Inhaled nitric oxide 5-40 ppm or inhaled epoprostenol 10-50 ng/kg/min | Follow PA pressures, PVR, cardiac index and oxygenation | Monitor methemoglobin with nitric oxide; never abruptly discontinue either agent (rebound pulmonary hypertension and collapse); inhaled epoprostenol inhibits platelets and clogs expiratory filters, which must be changed on schedule |
| Inotropic support | Dobutamine 2-10 mcg/kg/min; milrinone 0.125-0.5 mcg/kg/min | Rising cardiac index and SvO2 | Milrinone vasodilates systemically and is renally cleared with a long half-life, so it is usually paired with norepinephrine; dobutamine above 10 mcg/kg/min provokes tachyarrhythmia and ischemia |
| Eliminate pulmonary vasoconstrictors | Correct hypoxemia (SpO2 above 92%), hypercarbia (PaCO2 35-45 mmHg), acidosis (pH above 7.35), pain, agitation, hypothermia | Continuous monitoring | Every one of these raises PVR; this is often the cheapest and fastest intervention available |
| Ventilator strategy | Lowest effective PEEP, tidal volume 6 mL/kg predicted body weight, avoid auto-PEEP, avoid atelectasis and hypoventilation | Plateau under 30, driving pressure under 15 | High mean airway pressure raises PVR and reduces RV preload simultaneously; intubation of a severe PH patient is a high-mortality event requiring a vasopressor running first |
| Preserve rhythm and AV synchrony | Maintain sinus rhythm; early cardioversion of new atrial fibrillation or flutter | Rate control without negative inotropy | The atrial contribution to filling is disproportionately important in a stiff, failing RV; amiodarone is generally preferred over agents with strong negative inotropy |
| Escalate before organ failure | Right ventricular assist device (percutaneous RV support or dual-lumen cannula), VA-ECMO, transplant or pulmonary endarterectomy referral, balloon atrial septostomy in refractory PAH | Triggers: rising lactate, escalating vasopressor dose, falling urine output | Late escalation after multi-organ failure has markedly worse outcomes — the nurse's trend data drives the timing |
A patient with severe idiopathic pulmonary arterial hypertension is admitted with pneumonia. The nurse finds the ambulatory infusion pump delivering intravenous epoprostenol alarming for occlusion; the display shows the infusion stopped approximately 10 minutes ago. The patient is dyspneic with a blood pressure of 88/56 mmHg. What is the nurse's priority action?
Chronic PAH Therapy and the One Rule You Cannot Break
Group 1 PAH is treated by pathway. Know the classes, the monitoring, and the interactions — CMC asks about the nursing implications, not the mechanism.
| Class | Representative agents | Route | Key nursing points |
|---|---|---|---|
| Endothelin receptor antagonists (ERA) | Bosentan, ambrisentan, macitentan | Oral | Highly teratogenic — REMS enrollment with monthly pregnancy testing and two forms of contraception; bosentan requires monthly liver function tests; fluid retention and worsening edema, and anemia; bosentan induces CYP3A4 and lowers levels of warfarin, sildenafil and hormonal contraceptives |
| Phosphodiesterase-5 inhibitors | Sildenafil 20 mg three times daily, tadalafil 20-40 mg daily | Oral (IV sildenafil available) | Absolutely contraindicated with any nitrate — nitroglycerin, isosorbide, nitroprusside exposure, amyl nitrite — because of profound refractory hypotension; caution with alpha-blockers; expect headache, flushing, epistaxis and visual color changes |
| Soluble guanylate cyclase stimulator | Riociguat | Oral | Never combine with a PDE5 inhibitor or with nitrates; REMS program, contraindicated in pregnancy; approved for PAH and for inoperable or persistent/recurrent CTEPH; monitor for hypotension and syncope during titration |
| Prostacyclin pathway agents | Epoprostenol (continuous IV), treprostinil (IV, subcutaneous, inhaled, oral), iloprost (inhaled), selexipag (oral IP-receptor agonist) | Multiple | Jaw pain, flushing, diarrhea, headache, leg pain; site pain with subcutaneous treprostinil; catheter-related bloodstream infection risk with IV therapy. See the rule below |
| Activin signaling inhibitor | Sotatercept subcutaneously every 3 weeks | Subcutaneous | Newer agent added to background therapy in Group 1 PAH; monitor hemoglobin for erythrocytosis, platelet counts, bleeding and telangiectasia |
| Adjuncts | Diuretics, supplemental oxygen for SpO2 under 90%, anticoagulation in selected patients, high-dose calcium channel blockers only in the small minority with a positive acute vasoreactivity test | Starting a calcium channel blocker "for pulmonary hypertension" in a non-vasoreactive patient can cause acute RV failure and cardiovascular collapse — vasoreactivity must be documented at right heart catheterization |
The Prostacyclin Rule
Continuous intravenous prostacyclin infusions are never interrupted. Epoprostenol has a half-life of roughly 3-6 minutes; intravenous treprostinil roughly 4 hours. An abrupt interruption of epoprostenol can produce rebound pulmonary hypertension, acute RV failure and death within minutes. Operationalize this:
- The infusion runs through a dedicated lumen on a tunneled catheter. Nothing else goes into it. No piggyback, no flush, no blood draws, no contrast injection.
- The infusion does not stop for transport, CT, MRI, procedures or code situations. It travels with the patient with the pump and backup supplies.
- The patient's own pump, cassettes, diluent and backup pump come with them to the hospital, and experienced patients generally continue to manage their own dose.
- Never adjust or titrate the rate without direction from the pulmonary hypertension center.
- If the pump fails or occludes, restart the infusion immediately using the backup pump and cassette at the same dose and call the PH center — do not wait for pharmacy, and do not attempt to clear the line first.
- Suspected catheter-related bloodstream infection is treated aggressively with antibiotics; the line is not removed reflexively, because losing access is life-threatening.
Nursing Priorities
- Congestion assessment. Daily weights and strict intake and output are more reliable than examination in RV failure. Track jugular venous pressure or CVP, right-upper-quadrant tenderness, abdominal girth, and the surrogates of venous congestion — rising creatinine, rising bilirubin and transaminases, and worsening diuretic resistance.
- Perfusion assessment. SvO2 or ScvO2 trends, lactate, capillary refill, urine output and mentation. In RV failure the cardiac index falls before the blood pressure does.
- Prevent avoidable pulmonary vasoconstriction. Keep SpO2 above 90-92%, treat pain and anxiety, prevent hypothermia, avoid hypoventilation with sedatives, and correct acidosis.
- Prevent Valsalva. Straining raises intrathoracic pressure, abolishes venous return and causes syncope in severe PH. Provide aggressive bowel management, avoid heavy lifting, and coach the patient through position changes made slowly, with assistance, because exertional and post-exertional syncope in PAH is a sign of critically limited output and a marker of sudden death risk.
- Procedural and sedation risk. Every sedative causes systemic vasodilation and hypoventilation. A severe PH patient going for a "simple" cardioversion or endoscopy needs pre-procedure planning: arterial monitoring, a vasopressor prepared at the bedside, inhaled pulmonary vasodilator availability, and the anesthesia and PH teams involved in advance.
- Recognize that arrest in severe PAH has dismal survival — resuscitation rarely restores a failing, ischemic, pressure-overloaded RV. Prevention, early escalation, and honest advance care planning are the interventions that change outcomes.
A patient with known pulmonary arterial hypertension decompensates with sepsis. Hemodynamics show a MAP of 55 mmHg, CVP 20 mmHg, cardiac index 1.7 L/min/m2, SvO2 48%, and echocardiography shows a severely dilated hypokinetic right ventricle with leftward septal shift. Which initial supportive intervention is most appropriate?