132 PULMONARY THROMBOEMBOLISM AND PRIMARY PULMONARY HYPERTENSION
Harrison’s Manual of Medicine
PULMONARY THROMBOEMBOLISM AND PRIMARY PULMONARY HYPERTENSION
Pulmonary Embolism (PE)
Primary Pulmonary Hypertension (PPH)
Pulmonary Embolism (PE) (See Fig. 132-1)
FIGURE 132-1. Acute PTE management: Risk stratification. RV, right ventricular; IVC, inferior vena cava. (From Goldhaber SZ: HPIM-15.)
NATURAL HISTORY Immediate result is obstruction of pulmonary blood flow to the distal lung. Respiratory consequences include (1) wasted ventilation (lung ventilated but not perfused), (2) atelectasis that occurs 2–24 h following PE, and (3) widened alveolar-arterial PO2 gradient, usually with arterial hypoxemia. Hemodynamic consequences may include (1) pulmonary hypertension, (2) acute RV failure, and (3) decline in cardiac output. These occur only when significant fraction of pulmonary vasculature is obstructed. Infarction of lung tissue is uncommon, occurring only with underlying cardiac or pulmonary disease.
SYMPTOMS Sudden onset of dyspnea most common; chest pain, hemoptysis accompany infarction; syncope may indicate massive embolism.
PHYSICAL EXAMINATION Tachypnea and tachycardia common; RV gallop; loud P2 and prominent jugular a waves suggest RV failure; temperature >39°C uncommon. Hypotension suggests massive PE.
LABORATORY FINDINGS Routine studies contribute little to diagnosis; normal D-dimer level (<500 µg/ml by ELISA) essentially rules out PE, particularly in younger, ambulatory pts, but normal CXR does not exclude PE. Impedance plethysmography and femoral ultrasonography are sensitive tests for deep venous thrombosis when the pt has local symptoms. Likelihood of PE with ventilation-perfusion scan is dependent on clinical suspicion. With high clinical suspicion, high probability scan is very specific (>90%). A normal scan essentially excludes clinically significant PE. Many scans are “intermediate,” necessitating further evaluation. Spiral or helical CT, with a multidetector scanner, has a sensitivity of >90% compared to pulmonary angiography, the definitive test.
(See Fig. 132-1 and Guidelines) IV heparin [18 (U/kg)/h] by continuous infusion is therapy for most pts after an initial bolus of 80 U/kg. Documentation of effectiveness (activated PTT 1.5–2.0 × control) is essential as delay in reaching therapeutic level increases risk of recurrence. Heparin is continued 7 to 10 d for deep venous thrombosis (DVT) and 10 d for thromboembolism. Low-molecular-weight heparin (enoxaparin 1 mg/kg q12h) may be an alternative for DVT and in pts with minimally symptomatic PE. Most pts receive minimum of 3 months of oral coumadin therapy after PE. Thrombolytic therapy hastens resolution of venous thrombi and is probably indicated for pts with massive embolism and systemic hypotension. Surgical therapy is rarely employed for DVT or acute PE. IVC interruption (clip or filter) is used in pts with recurrent PE despite anticoagulants and in those who cannot tolerate anticoagulants. Surgical extraction of old emboli may be helpful in pts with chronic pulmonary hypertension due to repeated PE without spontaneous resolution.
Guidelines for the Treatment of Pulmonary Embolism
Treat DVT or PTE with therapeutic levels of unfractionated intravenous heparin, adjusted subcutaneous heparin, or low-molecular-weight heparin for at least 5 days and overlap with oral anticoagulation for at least 4 to 5 days. Consider a longer course of heparin for massive PTE or severe iliofemoral DVT.
For most patients, heparin and oral anticoagulation can be started together and heparin discontinued on day 5 or 6 if the INR has been therapeutic for two consecutive days.
Continue oral anticoagulant therapy for at least 3 months with a target INR of 2.5 (range 2.0 to 3.0).
Patients with reversible or time-limited risk factors can be treated for 3 to 6 months. Patients with a first episode of idiopathic DVT should be treated for at least 6 months. Patients with recurrent venous thrombosis or a continuing risk factor such as cancer, inhibitor deficiency states, or antiphospholipid antibody syndrome should be treated indefinitely.
Isolated calf vein DVT should be treated with anticoagulation for at least 3 months.
The use of thrombolytic agents continues to be highly individualized, and clinicians should have some latitude in using these agents. Patients with hemodynamically unstable PTE or massive iliofemoral thrombosis are the best candidates.
Inferior vena caval filter placement is recommended when there is a contraindication to or failure of anticoagulation, for chronic recurrent embolism with pulmonary hypertension, and with concurrent performance of surgical pulmonary embolectomy or pulmonary endarterectomy.
*Modified from TM Hyers et al: Antithrombotic therapy for venous thromboembolic disease. chest 114:561S, 1998.
Primary Pulmonary Hypertension (PPH)
HISTORY Uncommon condition. Typical pt is female aged 20–40. At presentation, symptoms are usually of recent onset, and natural history is ordinarily <5 years. Familial clusters occur. Early symptoms are nonspecific— hyperventilation, chest discomfort; anxiety, weakness, fatigue. Later, dyspnea develops and precordial pain on exertion occurs in 25–50%. Effort syncope occurs very late and signifies ominous prognosis.
PHYSICAL EXAMINATION Prominent a wave in jugular venous pulse, right ventricular heave, narrowly split S2 with accentuated P2. Terminal course is characterized by signs of right-sided heart failure. CXR: RV and central pulmonary arterial prominence. Pulmonary arteries taper sharply. PFT: usually normal or mild restrictive defect. ECG: RV enlargement, right axis deviation, and RV hypertrophy. Echocardiogram: RA and RV enlargement and tricuspid regurgitation (Fig. 132-2).
FIGURE 132-2. An algorithm for the workup of a pt with unexplained pulmonary hypertension. (Adapted with permission from Rich S: HPIM-15.)
DIFFERENTIAL DIAGNOSIS Other disorders of heart, lungs, and pulmonary vasculature must be excluded. Lung function studies will identify chronic pulmonary disease causing pulmonary hypertension and cor pulmonale. Interstitial diseases (PFTs, CT scan) and hypoxic pulmonary hypertension (ABGs, SaO2) should be excluded. Perfusion lung scan should be performed to exclude chronic PE. Spiral CT scan, pulmonary arteriogram, and even open- lung biopsy may be required to distinguish PE from PPH. Rarely, pulmonary hypertension is due to parasitic disease (schistosomiasis, filariasis). Cardiac disorders to be excluded include pulmonary artery and pulmonic valve stenosis. Pulmonary artery and ventricular and atrial shunts with pulmonary vascular disease (Eisenmenger reaction) should be sought. Silent mitral stenosis should be excluded by echocardiography.
Course is usually one of progressive deterioration despite treatment; therapy is palliative, but treatment has improved in recent years. Main focus of therapy is vasodilator drugs. Must lower pulmonary artery pressure and pulmonary vascular resistance while preserving systemic pressure. High doses of calcium channel antagonists (e.g., nifedipine, 120–240 mg/d, or diltiazem, 540–900 mg/d) may reduce pulmonary pressure and resistance, but fewer than half of pts with PPH respond. Proof of vascular reactivity with a short-term drug trial (prostacyclin, inhaled nitric oxide, or adenosine) can help identify candidates for pharmacologic therapy. Recent evidence suggests prostacyclin is effective in selected pts, but treatment requires a continuous infusion. Some experts recommend anticoagulation for all pts. Pts who fail medical therapy may be considered for transplantation.
For a more detailed discussion, see Rich S: Primary Pulmonary Hypertension, Chap. 260, p. 1506; and Goldhaber SZ: Pulmonary Thromboembolism, Chap. 261, p. 1508, in HPIM-15.