Diagnostic Approach

Suspect PE in a patient presenting with unexplained chest pain, dyspnea, tachypnea, syncope, or shock. Figure.52-3 is an algorithm for the approach to patients with suspected PE.

FIG. 52-3. A. Evaluation of stable patients with suspected PE.

*Refer to text and Chap 55.

fRefer to text.

B. Further evaluation of patients with suspected PE whose earlier tests have been negative. *Perform these studies only if not previously obtained.

fThe clinician may proceed directly to pulmonary arteriography depending on local availability and practice.

Historical evidence of risk for DVT, physical findings suggestive of DVT or PE and findings from ECG, CXR, and ABG are used to determine a pretest probability of PE.

Patients whose signs and symptoms remain unexplained should undergo further diagnostic evaluation, taking into account their clinical stability ( Fig 52-3). Stable patients should be studied for leg DVT (DUS, IPG, or venography) or PE (V/Q scan). If DVT is confirmed, the patient should be admitted for anticoagulation therapy.

If a V/Q scan is of high probability and clinical suspicion for PE is high, admission for anticoagulation is warranted. If the V/Q scan is of low probability and the pretest suspicion also low, another diagnosis should be sought. A normal V/Q scan reliably excludes PE regardless of clinical suspicion. All other combinations of V/Q probabilities and clinical suspicion require further evaluation, whether pulmonary angiography, spiral CT, or MRI angiography.

For unstable patients suspected of having PE, transthoracic or transesophageal echocardiography is especially useful. Evidence of proximal pulmonary artery emboli or right ventricular embolus in transit is sufficient evidence to justify thrombolytic therapy without pulmonary angiography. 18 Echocardiography has the additional benefit of identifying patients with acute right ventricular dysfunction and normal systemic hemodynamics—a group at risk for catastrophic clinical deterioration. Sending an unstable patient to the nuclear medicine or angiography suite is potentially hazardous, requires intensive nursing and physician support, and should be done only as a last resort.

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Essentials of Human Physiology

Essentials of Human Physiology

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