Value of negative spiral CT angiography in patients with suspected acute PE: analysis of PE occurrence and outcome.

The aim of this study was to analyze pulmonary embolism (PE) occurrence and retrospective clinical outcome in patients with clinically suspected acute PE and a negative spiral CT angiography (SCTA) of the pulmonary arteries. Within a 35-month period, 485 consecutive patients with clinical symptoms of acute PE underwent SCTA of the pulmonary arteries. Patients with a negative SCTA and without anticoagulation treatment were followed-up and formed the study group. Patient outcome and recurrence of PE was evaluated retrospectively during a period of 6 months after the initial SCTA, and included a review of computerized patient records, and interviews with physicians and patients. Patients were asked to fill out a questionnaire concerning all relevant questions about their medical history and clinical course during the follow-up period. Special attention was focused on symptoms indicating recurrent PE, as well as later confirmation and therapy of PE. Of the 485 patients, 325 patients (67%) had a negative scan, 134 (27.6%) had radiological signs of PE, and 26 (5.4%) had an indeterminant result. Of 325 patients with a negative scan, 269 (83%) were available for follow-up. The main reasons for loss to follow-up were change of address, name, or phone number, or non-resident patients who left abroad. Of 269 patients available for follow-up, 49 patients (18.2% of 269) received anticoagulant treatment because of prior or recent deep venous thrombosis (32.6%) or a history of PE (34.7%), cardiovascular disease (18.4%), high clinical probability (8.2%), positive ventilation-perfusion scan (4.2%), and elevated D-dimer test (2%). The remaining 220 patients, who did not receive anticoagulant medication, formed the study group. Of this study group, 1 patient died from myocardial infarction 6 weeks after the initial SCTA, and the postmortem examination also detected multiple peripheral emboli in both lungs ( p=0.45%; 0.01-2.5, 95% confidence interval). The PE did not occur in any other patient. In patients with suspected PE and negative SCTA without anticoagulant therapy, the risk of recurrent PE in this study was less than 1% and similar to that in patients after a negative pulmonary angiogram. Therefore, we conclude that patients can be managed safely without anticoagulation therapy; however, this approach may not be appropriate for critically ill patients and those with persistent high clinical suspicion of acute PE.