Cor Pulmonale

Cor pulmonale is right ventricular (RV) dysfunction caused by lung disease that results in pulmonary artery hypertension. The most common cause of cor pulmonale is chronic obstructive pulmonary disease. Dyspnea is the usual presenting symptom. Clinical findings include signs of right-sided heart failure and hypoxemia. While right cardiac catheterization is the gold standard test, most patients are diagnosed clinically and through the use of noninvasive testing. Echocardiography shows RV enlargement and elevated pulmonary arterial systolic pressure. Management is first focused on the underlying disease. Oxygen therapy improves disease progression, while diuretics reduce RV filling pressure. Lung transplantation is an option for those refractory to therapy.

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Overview

  • Also known as pulmonary heart disease
  • Characterized by structural alteration and dysfunction of the right ventricle (RV) caused by primary lung disease
  • Can be acute or chronic:
    • Acute cor pulmonale is most commonly caused by massive pulmonary embolism. 
    • Chronic cor pulmonale has a slow and progressive course resulting from worsening lung disease.
  • Chronic lung disease with cor pulmonale indicates a poor prognosis.

Etiology and Epidemiology

Etiology

  • Cor pulmonale develops from increased right-sided filling pressures from long-term pulmonary hypertension (PH) associated with lung disease.
  • Pulmonary hypertension is defined as:
    • Increased blood pressure in pulmonary arteries
    • Mean pulmonary arterial pressure of > 20 mm Hg (at rest, measured by right heart catheterization; normal = 14–20 mm Hg)
    • For pre-capillary PH (disease confined to pulmonary arterial bed), criteria include pulmonary vascular resistance (PVR) of ≥ 3 Wood units).
  • PH Classification (based on the 6th World Symposium of Pulmonary Hypertension proceedings):
    • Group 1: Pulmonary arterial hypertension
    • Group 2: PH due to left heart disease
    • Group 3: PH due to lung disease and/or hypoxia
      • Obstructive lung disease
      • Restrictive lung disease
      • Mixed obstructive/restrictive pattern
      • Hypoxia (without lung disease)
      • Developmental lung disorders
    • Group 4: PH due to pulmonary artery obstructions
    • Group 5: PH with unclear and/or multifactorial mechanisms
  • RV dysfunction resulting from left-sided heart disease and congenital heart disease (group 2 PH) is not cor pulmonale.
Etiologies of chronic cor pulmonale
Primary lung diseaseDiseases causing chronic hypoxiaPrimary pulmonary vascular disease
  • Chronic obstructive pulmonary disease
  • Interstitial lung diseases
  • Cystic fibrosis
  • Obesity hypoventilation syndrome
  • Central hypoventilation syndrome
  • Neuromuscular respiratory failure
  • Kyphosis
  • Chronic high-altitude hypoxia
  • Idiopathic or associated pulmonary arterial hypertension
  • Chronic thromboembolic disease

Epidemiology

  • Prevalence: limited data; right heart catheterization is not regularly performed for patients at risk
  • Cor pulmonale: 6%–7% of all types of adult heart disease in the United States
  • Half of the cases in North America are due to chronic obstructive pulmonary disease (COPD).

Pathophysiology

  • Hypoxic pulmonary vasoconstriction
    • To limit blood flow to hypoxic alveoli, low oxygen leads to pulmonary vasoconstriction, diverting blood to the better-ventilated alveoli.
    • Changes in vascular mediators: 
      • ↑ Endothelin-1 (vasoconstrictor, smooth muscle proliferation)
      • ↓ Endothelial nitric oxide synthase production: ↓ nitric oxide (vasodilator)
      • ↓ Prostacyclin (vasodilator)
    • Changes in ion channels:
      • Chronic hypoxia reduces expression of potassium channels, increases intracellular calcium ⇒ pulmonary artery muscle contraction
  • Pulmonary vascular remodeling
    • Vascular alterations occur: neomuscularization of arterioles, intimal thickening, medial hypertrophy
    • Inflammation and effects of cigarette smoking are potential mechanisms, as COPD-afflicted patients without hypoxemia have also been found to have endothelial dysfunction in pulmonary arteries. 
  • Above factors lead to increased pulmonary vascular resistance. 
    • As resistance increases, as does pulmonary artery pressure and, eventually, RV afterload.
    • RV adapts to slowly increasing pulmonary artery pressure initially by dilation; leads to hypertrophy.
    • Consequent effect is RV dysfunction and failure.
  • RV hypertrophy does not occur with acute cor pulmonale.
Cor Pulmonale Pathophysiology

Pathophysiology of cor pulmonale

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Clinical Presentation

Symptoms

  • Dyspnea: caused by the underlying pulmonary disease and resulting cor pulmonale
  • Chest pain: from increased oxygen demand and increased stress on the RV
  • Syncope: inability to increase cardiac output with exertion or exercise
  • Peripheral edema and increased abdominal girth: from right-sided heart failure and hepatic congestion
  • Anorexia, nausea/vomiting, right upper quadrant pain: from hepatic congestion

Signs

Inspection

  • Signs of high right-sided filling pressures:
    • RV heave
    • Elevated jugular venous pressure
    • Prominent V waves due to tricuspid regurgitation (jugular vein exam)
  • Signs of hepatic congestion from right-sided heart failure:
    • Hepatomegaly and/or pulsatile liver
    • Ascites
    • Lower-extremity edema
  • Signs of hypoxemia:
    • Increased respiratory rate
    • Cyanosis
    • Clubbing

Chest auscultation

  • Lungs: depends on underlying pulmonary disease
  • Heart: accentuated P2, blowing holosystolic murmur at the left lower sternal border (tricuspid regurgitation murmur), and S3 gallop

Diagnosis

Right heart catheterization

  • Gold standard to confirm pulmonary hypertension, but not required in all patients
  • Indications affected by:
    • Severity of PH
    • Potential for PH–specific treatment
    • Life expectancy of patient
    • Possibility of lung transplantation
  • Results: mean pulmonary arterial pressure (mPAP) ≥ 20 mm Hg

Doppler echocardiography

  • Initial test of choice 
  • RV enlargement (dilation and/or hypertrophy)
  • Paradoxical movement of interventricular septum 
    • The septum is shifted toward the left ventricle, resulting in flattening of the ventricular septum during systole.
  • Increased pulmonary artery systolic pressure 
  • Tricuspid regurgitation with a high-velocity regurgitant jet by Doppler
  • Rules out left-sided heart failure

Laboratory studies

  • Arterial blood gases: possible hypoxia ± hypercarbia and acidosis depending on degree of lung disease
  • Elevated B-type natriuretic peptide (BNP) and N-terminal BNP
  • CBC may show ↑ hemoglobin, ↑ hematocrit (from secondary erythrocytosis caused by hypoxia)

Electrocardiogram

  • P pulmonale
  • Right axis deviation, right ventricular hypertrophy

Chest X-ray

  • Central pulmonary artery and hilar enlargement
  • Cardiomegaly (from RV enlargement)
  • Changes consistent with underlying pulmonary disease

Pulmonary function test

  • Shows obstructive and/or restrictive defects depending on underlying lung diseases

Chest computed tomography (CT) scan

  • High-resolution: signs of interstitial lung disease or emphysema
  • Angiogram: acute pulmonary embolism in the case of acute cor pulmonale; enlarged pulmonary artery

Ventilation-perfusion scan

  • Preferred initial test for chronic thromboembolism
  • Greater sensitivity for chronic pulmonary thromboembolism than CT angiogram

Cardiac magnetic resonance imaging (MRI)

  • Not routinely used but shows increased RV size

Management

Management is first focused on the underlying cause of cor pulmonale.

  • Smoking cessation
  • Oxygen therapy:
    • Only treatment that slows down progression of PH in COPD
    • Relieves pulmonary vasoconstriction, thereby improving cardiac output and tissue perfusion
    • Indications:
      • PaO2 ≤ 55 mm Hg or oxygen saturation < 88% in general
      • PaO2 ≤ 59 mm Hg or oxygen saturation ≤ 89% for patients with cor pulmonale, right heart failure, or hematocrit > 55% 
  • Pharmacotherapy:
    • For chronic right heart failure or elevated RV filling pressures: diuretics (but monitor for volume depletion)
    • For primary pulmonary arterial hypertension or group 1 PH: 
      • Calcium channel blockers (leads to pulmonary artery vasodilation), prostaglandin analogs, endothelin-receptor antagonists, phosphodiesterase-5 (PDE-5) inhibitors
      • These medications have limited benefit in group 3 PH and in some cases may be harmful.
    • Treatment of venous thromboembolism: anticoagulants
  • Surgical management:
    • COPD patients with hematocrit ≥ 65%: phlebotomy
    • Surgical embolectomy in massive pulmonary embolism with acute cor pulmonale (if thrombolysis fails or is contraindicated)
    • Lung ± heart transplantation: for patients who failed therapy

References

  1. Elwing, J.; Panos, R. (2008). Pulmonary hypertension associated with COPD. Int J Chron Obstruct Pulmon Dis. 3(1), 55–70. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2528217/
  2. Garrison, D.; Pendela, V.; Memon, J. (2020). Cor Pulmonale. https://www.ncbi.nlm.nih.gov/books/NBK430739/
  3. Klings, E.; Mandel, J.; King, T. & Finlay, G. (Eds.). (2019). Pulmonary hypertension due to lung disease and/or hypoxemia (group 3 pulmonary hypertension): Epidemiology, pathogenesis and diagnostic evaluation in adults. UpToDate. Retrieved Aug 15, 2020, from https://www.uptodate.com/contents/pulmonary-hypertension-due-to-lung-disease-and-or-hypoxemia-group-3-pulmonary-hypertension-epidemiology-pathogenesis-and-diagnostic-evaluation-in-adults
  4. Leong, D.; Ooi, H. (Ed). (2017). Cor pulmonale. Medscape. https://emedicine.medscape.com/article/154062-overview
  5. Ryu, J.; Frantz, R.; King, T; Mandel, J. & Finlay, G. (Eds.). (2020). Pulmonary hypertension due to lung disease and/or hypoxemia (group 3 pulmonary hypertension): Treatment and prognosis. UpToDate. Retrieved Aug 15, 2020, from https://www.uptodate.com/contents/pulmonary-hypertension-due-to-lung-disease-and-or-hypoxemia-group-3-pulmonary-hypertension-treatment-and-prognosis

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