The authors would like to acknowledge David A. Miller for his contributions that remain unchanged from the first edition.
PULMONARY HYPERTENSION
I. Etiology
A. Increased pulmonary vascular resistance
1. Vasoconstriction (e.g., due to hypoxemia, acidosis)
2. Loss of vasculature (e.g., due to emphysema, lung resection)
3. Occlusion of the pulmonary vasculature (e.g., due to pulmonary embolism)
4. Relative stenosis of the pulmonary vasculature (vasculitis)
B. Increased pulmonary venous pressure
1. Left ventricular failure or hypertrophy
2. Valvular heart disease (e.g., mitral valve stenosis, aortic valve stenosis)
3. Constrictive pericarditis
C. Increased pulmonary blood flow (left-to-right shunt)
D. Polycythemia (primary or secondary; e.g., from hypoxemia)
E. Primary (idiopathic) pulmonary hypertension, seen most often in young women
II. Incidence
Note: The incidence of secondary pulmonary hypertension is related to the incidence of the cause of pulmonary hypertension.
III. Clinical manifestations
A. Symptoms
1. Dyspnea with exertion and later at rest
2. Those related to the cause of the pulmonary hypertension
3. Substernal discomfort
4. Fatigue
5. Syncope
B. Physical examination findings
1. Splitting of the second cardiac sound; pulmonic valve component of the second heart sound (P2) is increased in intensity.
2. Peripheral edema related to right ventricular failure
3. Ascites
C. Laboratory
1. CBC: increase in hemoglobin and hematocrit, if hypoxemia is present
2. ECG: right axis deviation
D. Chest x-ray
1. Increased size of the pulmonary arteries
2. Visible narrowing of the pulmonary arteries in the medial third of the lung (typically seen in emphysema)
E. Two-dimensional echocardiogram is used to diagnose pulmonary hypertension; cardiac catheterization is used to confirm the diagnosis.
F. Echocardiogram to rule out valvular heart disease and left atrial myxoma
G. Pulmonary function testing
1. To assess for obstructive and restrictive ventilatory defects
2. Primary pulmonary hypertension is a diagnosis of exclusion.
IV. Treatment
A. Treatment of underlying disorders that contribute to hypoxemia, including the following:
1. Chronic obstructive pulmonary disease (COPD)
2. CHF
3. Obstructive sleep apnea (OSA)
B. Supplemental oxygen during the night
C. Consider anticoagulation if the risk of small, recurrent pulmonary emboli is present.
D. If polycythemia is severe, with hematocrit above 60%, therapeutic phlebotomy should be considered to yield a hematocrit of about 55%.
E. Primary pulmonary hypertension is treated with calcium channel blockers and anticoagulation.
I. Pulmonary Embolism (PE)
A. Definition
1. Clot (thromboembolus) or other undissolved solid, liquid, or gaseous material that has traveled to the lung via the venous system, lodged in the pulmonary arterial circulation, and interrupted blood flow
2. Extent of lung tissue injury is determined by the size of the embolus, which is considered massive if more than 50% of flow is obstructed.
3. Accurate diagnosis is the key to reducing associated mortality.
4. Death occurs as a result of right ventricular failure.
B. Etiology/Incidence/Predisposing factors
1. Predisposing factors for thrombotic emboli (Virchow’s triad) include the following:
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a. Venous stasis: Deep venous thrombosis in lower extremities and pelvis leads to 90% to 95% of pulmonary emboli.
i. Prolonged immobility or surgery involving general anesthesia longer than 30 minutes
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