Lab interpretation: interpret arterial blood gases and calculate the alveolar-arterial oxygen gradient; recognize CXR and EKG findings associated with PE.
Opinions regarding the diagnosis and management of venous thromboembolic disease. ACCP Consensus Committee on Pulmonary Embolism, Chest 1998;113:499-504.
Clinically relevant questions related to the diagnosis and management of acute pulmonary embolism and deep venous thrombosis were addressed. The data on which the opinions of the committee were based were sparse. The consensus opinions were often based on experience or intuition rather than firm data. Below are some of the questions that were addressed.
QUESTION: What is the utility of the D-dimer in combination with V/Q scans?
In a study of 10 patients who had a low probability interpretation of the lung scan and a plasma D-dimer level <500 ng/mL (a low value), the negative predictive value for acute PE was 100%. Other studies used different cut-off values for D-dimer.
The ELISA for D-dimer has a high negative predictive value for PE. Additional studies are needed to standardize the testing.
QUESTION: What is the role of contrast-enhanced helical (spiral) CT?
Pooled data from helical CT imaging compared to conventional pulmonary angiography or autopsy showed a sensitivity of 72% and a specificity of 95%. For PE in central pulmonary arteries, pooled data show a sensitivity of 94% which fell to 13% for PE in subsegmental pulmonary arteries.
Helical CT is most useful for PE in the central arteries. However, this diagnostic modality is still under investigation. A normal contrast-enhanced CT scan does not exclude PE, particularly in subsegmental arteries. If only a limited amount of contrast material can be given safely to a particular patient (e.g., a renal failure patient), then it may be wise to select the single most definitive test such as pulmonary angiography.
QUESTION: Can low molecular weight heparin (LMWH) be recommended for the outpatient treatment of deep venous thrombosis or PE at this time?
The home treatment of DVT with LMWH compared to inpatient administration of continuous IV heparin showed that there were no differences in recurrent thromboembolic events and bleeding complications. No study has investigated the outpatient use of LMWH for the treatment of PE.
In the USA, LMWH has not been approved for the treatment of DVT and PE. The outcome of studies now in progress will determine the safety and efficacy of LMWH in an outpatient setting.