Question 5: What is the role of venous imaging in the evaluation of patients with suspected pulmonary embolism?

• Level A recommendations. None specified.
• Level B recommendations. When a decision is made to perform venous ultrasound as the initial imaging modality, a positive finding in a patient with symptoms consistent with pulmonary embolism can be considered evidence for diagnosis of VTE disease and may preclude the need for additional diagnostic imaging in the emergency department. Examples of situations in which a venous ultrasound may be considered as initial imaging may include patients with obvious signs of DVT for whom venous ultrasound is readily available, patients with relative contraindications for CT scan (e.g., borderline renal insufficiency, CT contrast agent allergy), and pregnant patients.
• Level C recommendations. (1) For patients with an intermediate pretest probability for pulmonary embolism and a negative CT angiogram result, for whom a clinical concern for pulmonary embolism still exists and CT venography has not already been performed, consider lower-extremity venous ultrasound as an additional test to exclude VTE disease (see question 4). (2) In patients with a high pretest probability for pulmonary embolism and a negative CT angiogram, and CT venography has not already been performed, perform additional testing to exclude VTE disease (see question 4). As one of these additional tests, consider lower-extremity venous ultrasound to exclude VTE disease (see question 4).

As discussed in Question 4, it is recommended that high-risk patients with a negative CT angiogram have additional diagnostic testing prior to exclusion of VTE disease. Both venous ultrasound and CT venography have been demonstrated to be reliable modalities. The advantage of CT venography is that it can be performed concurrently with the CT angiography. The advantage of venous ultrasound is that it does not result in any additional radiation exposure to the patient. In select patients with suspected pulmonary embolism in whom it would be advantageous to avoid CT scanning (e.g., renal insufficiency, CT contrast agent allergy, pregnancy), a positive venous ultrasound can be considered diagnostic of VTE disease, thus potentially obviating the need for additional testing.

Question 6. What are the indications for thrombolytic therapy in patients with pulmonary embolism?

• Level A recommendations. None specified.
• Level B recommendations. Administer thrombolytic therapy in hemodynamically unstable patients with confirmed PE for whom the benefits of treatment outweigh the risks of life-threatening bleeding complications. (In centers with the capability for surgical or mechanical thrombectomy, procedural intervention may be used as an alternative therapy.)
• Level C recommendations. (1) Consider thrombolytic therapy in hemodynamically unstable patients with a high clinical suspicion for pulmonary embolism for whom the diagnosis of PE cannot be confirmed in a timely manner. (2) At this time, there is insufficient evidence to make any recommendations regarding use of thrombolytics in any subgroup of hemodynamically stable patients. Thrombolytics have been shown to result in faster improvements in right ventricular function and pulmonary perfusion, but these benefits have not translated to improvements in mortality.
  Despite proven benefit of thrombolytic therapy in patients with ST-segment elevation acute myocardial infarction and select patients with acute strokes, indications for use of thrombolytic therapy in patients with pulmonary embolism remain controversial despite more than 40 years of experience. Overwhelming consensus opinion is to treat hemodynamically unstable patients with confirmed PE when the benefits of treatment outweigh the risks. As it is doubtful that any randomized study in the treatment of hemodynamically unstable patients will ever be performed, future studies should focus on the hemodynamically stable patients at higher risk of adverse outcome.
  Although there has been an explosion of research in pulmonary embolism and in VTE disease, there are still many unanswered questions. With the advent of electronic charting, studies must be performed integrating decision support tools that utilize pretest probability assessment with standardized algorithms in order to make the best use of the available diagnostic and treatment modalities. Outcome studies are also needed that investigate the utility of the newest generation of CT scanners that have much higher resolution than the 4- to 64-channel detectors utilized in the studies that form the basis of the recommendations in this clinical policy. Finally, randomized studies investigating which populations of hemodynamically stable patients with diagnosed pulmonary embolism will benefit from thrombolytic therapy must be performed. The Pulmonary Embolism Thrombolysis Study (PEITHO) is an ongoing randomized, controlled trial of tenecteplase versus placebo in pulmonary embolism patients with right ventricular dysfunction on echocardiography and an elevated troponin level. It is hoped that this study will identify a specific subgroup who will benefit from thrombolytic therapy.

Dr. Fesmire is Professor and Clinical Research Director in the Department of Emergency Medicine, University of Tennessee College of Medicine Chattanooga; and Medical Director of the Chest Pain Center, Erlanger Medical Center, Chattanooga.