Pulmonology · Pulmonary Vascular Disease
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Pulmonary hypertension is defined by a mean pulmonary artery pressure (mPAP) > 20 mmHg measured via right heart catheterization.
The gold standard for diagnosing and classifying pulmonary hypertension is right heart catheterization to distinguish between pre-capillary and post-capillary disease.
Group 1 pulmonary arterial hypertension (PAH) is characterized by a pulmonary artery wedge pressure (PAWP) ≤ 15 mmHg and pulmonary vascular resistance (PVR) ≥ 2 Wood units.
Group 2 pulmonary hypertension is the most common etiology and is caused by left-sided heart disease resulting in an elevated PAWP > 15 mmHg.
Physical examination findings often reveal a loud pulmonic component of the second heart sound (P2) and signs of right-sided heart failure such as jugular venous distension and peripheral edema.
Echocardiography is the initial screening test of choice, typically demonstrating right ventricular hypertrophy, right atrial enlargement, and an estimated pulmonary artery systolic pressure (PASP).
Vasodilator challenge during right heart catheterization is mandatory for patients with idiopathic PAH to determine eligibility for calcium channel blocker therapy.
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A 34-year-old woman presents with progressive exertional dyspnea and fatigue over the past six months. Physical examination reveals a loud P2, a parasternal heave, and 3+ pitting edema in the lower extremities. An electrocardiogram shows right axis deviation and right ventricular hypertrophy. A transthoracic echocardiogram demonstrates a dilated right ventricle and an estimated pulmonary artery systolic pressure of 75 mmHg. A subsequent right heart catheterization reveals a mean pulmonary artery pressure of 42 mmHg, a PAWP of 10 mmHg, and a PVR of 5 Wood units.
What is the most likely classification of this patient's pulmonary hypertension?
Group 1 Pulmonary Arterial Hypertension (PAH)
The patient meets the criteria for Group 1 PAH because the mPAP is > 20 mmHg, the PAWP is ≤ 15 mmHg (indicating pre-capillary disease), and the PVR is ≥ 2 Wood units.
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Etiology / Epidemiology
Group 1 (PAH) is idiopathic or associated with connective tissue disease and portal hypertension. Group 2 is left-sided heart disease.
Clinical Manifestations
Dyspnea on exertion and loud P2. Right ventricular heave indicates advanced disease.
Diagnosis
Right heart catheterization confirms mean pulmonary artery pressure >20 mmHg.
Treatment
Group 1 PAH requires Endothelin receptor antagonists or PDE5 inhibitors. Avoid calcium channel blockers in non-responders.
Prognosis
Progressive right heart failure is the primary cause of death. Mean survival without transplant is poor.
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Epidemiology & Etiology
Classified into 5 groups; Group 1 (PAH) often affects young women with autoimmune disease or HIV. Group 2 is the most common, driven by left ventricular dysfunction or valvular disease. Group 3 is associated with COPD and interstitial lung disease.
Pertinent Anatomy
Increased resistance in the pulmonary vasculature leads to increased afterload on the right ventricle. Chronic pressure overload causes right ventricular hypertrophy and eventual dilation.
Pathophysiology
Vascular remodeling involves endothelial dysfunction and proliferation of smooth muscle cells. This leads to vasoconstriction and *in situ* thrombosis. The resulting increased pulmonary vascular resistance forces the right heart to work against high pressure, leading to cor pulmonale.
Clinical Manifestations
Patients present with progressive dyspnea, fatigue, and syncope during exertion. Physical exam reveals a loud P2 (pulmonic component of S2) and a parasternal heave. Signs of right-sided heart failure include peripheral edema, ascites, and jugular venous distension.
Diagnosis
Right heart catheterization is the gold standard for diagnosis. Diagnostic threshold is a mean pulmonary artery pressure >20 mmHg at rest. Echocardiogram is the initial screening tool to estimate pulmonary artery systolic pressure.
Treatment
Management depends on the WHO group; Group 1 PAH is treated with Bosentan or Sildenafil. Calcium channel blockers are only indicated for patients with a positive vasoreactivity test. Advanced cases require prostacyclin analogs or lung transplantation.
Prognosis
The disease is progressive, leading to right-sided heart failure and death. Patients require regular 6-minute walk tests and serial echocardiograms to monitor functional status.
Differential Diagnosis
COPD: history of smoking and obstructive spirometry
Left heart failure: elevated PCWP on catheterization
Pulmonary embolism: acute onset with S1Q3T3 pattern
Mitral stenosis: diastolic murmur and left atrial enlargement
Interstitial lung disease: restrictive pattern on PFTs