med 18

 

CLINICAL PRESENTATION

� History

The classic triad of chest pain, dyspnea, and hemoptysis is

present in fewer than 20% of patients. Dyspnea is the most

common symptom associated with PE, occurring in up to

80% of confirmed cases, with 67% experiencing rapid

onset of shortness of breath. Pleuritic chest pain is present

in 52% of patients, but substernal chest pain is present in

<20%. Other symptoms include fainting, cough, palpitations, hemoptysis, and calf/thigh pain or swelling.

Risk factors for deep vein thrombosis (DVT) and PE are

inherited or acquired and continue to follow Virchow's triad

described in 1 856: venous stasis (eg, bed rest >48 hours,

long-distance auto or air travel, recent hospitalization),

alterations in coagulation ( eg, malignancy, previous PE/

DVT, pregnancy, or protein C deficiency), and vascular

injury (eg, trauma, recent surgery, central lines, IV drug

use) . Ninety-four percent of all patients with PE have one

or more risk factors.

� Physical Examination

Tachypnea (� 20/min) is one of the most sensitive clinical

findings, with a prevalence of 70% in PE confirmed cases.

1 08

PULMONARY EMBOLISM

Tachycardia (�100/min) has a prevalence of 26%. Pulse

oximetry is frequently normal in patients with a PE and

cannot be used to exclude the diagnosis. Lung examination

may be clear or may reveal rales, whereas extremity examination is useful only if signs of a DVT are present. Rectal

examination for blood is useful to assess bleeding risk if

anticoagulation becomes necessary.

DIAGNOSTIC STUDIES

...... Laboratory

Although many patients with PE are hypoxic (PaO 2 <

80 mmHg), this is not universally true. The A-a gradient

can be used as an indirect measure of ventilationperfusion V/Q abnormalities, although 1 5% of patients

with PE have a normal A-a gradient.

D-dimer is a fibrin degradation product that circulates

in a patient with a dissolving fibrin thrombus. It is found

in the serum within 1 hour and stops circulating after

7 days. Multiple d-dimer tests exist with varying sensitivities and specificities, but a negative d-dimer t est (enzymelinked immunosorbent assay or turbidimetric) in patients

with a low pretest probability implies a risk for PE of less

than 1%.

Troponin and brain natriuretic peptide have been stud ­

ied in the context of PE, and at this time their value may be

limited to risk stratification only.

...... Electrocardiogram

An electrocardiogram (ECG) is useful to rule out a primary

cardiac etiology and is neither specific nor sensitive for PE.

Approximately 30% of patients with PE have a normal ECG.

Sinus tachycardia is present in up to 36% of patients with

PE. The classic S 1Q3T3 combination of findings (S wave in

lead I, Q wave in lead III, and T wave inversion in lead III) is

present in <20% of patient with confirmed PE. Right-sided

heart strain seen as T-wave inversions in the anterior leads

(v1-v4) may be present in massive PE.