Tc-99m technegas ventilation and perfusion lung scintigraphy for the diagnosis of pulmonary embolus

Lung scintigraphy is used widely for diagnosis of pulmonary embolus (PE). T echnegas ventilation imaging has many advantages over other methods, but li ttle outcome data exists on this technique. The aims of this study were to better define the role of lung scintigraphy in the management of patients w ith suspected PE and to evaluate technegas ventilation imaging by following patient outcomes. Methods: A group of 717 out of 834 consecutive patients, referred to a university teaching hospital for lung scintigraphy to confir m or refute the diagnosis of PE, was followed for 18-30 mo to determine cli nical outcome. The follow-up endpoints were death as a result of PE, death as a result of hemorrhage after treatment for PE, uncomplicated survival, s urvival with subsequent PE, nonfatal hemorrhage after treatment for PE and recurrence of PE in treated patients. Ventilation imaging was performed usi ng technegas, and perfusion imaging was performed using intravenous Tc-99m macroaggregated albumin. The modified PIOPED (Prospective Investigation of Pulmonary Embolism Diagnosis) diagnostic criterion was used for interpretat ion of lung scintigraphy. Results: Diagnostic results included 3.5% normal studies, 67.4% assessed as low probability for PE, 10% as moderate probabil ity for PE and 19.1% as high probability for PE. A total of 231 patients re ceived therapy with heparin, followed by warfarin, including those receivin g anticoagulation therapy for other conditions. Ninety-six percent of patie nts with normal and low probability studies (n = 508) had good outcomes, 6 patients died as a result of PE and 12 subsequently developed PE. The odds ratio for death by PE in this group was 0.2. Of the 72 moderate probability studies, 39 patients were untreated. In this group there was 1 death due t o PE, and PE subsequently developed in 2 patients. None of the remaining 33 treated patients died, but 4 patients experienced bleeding complications. The odds ratio for death by PE in the moderate probability group was 0.7. I n those patients with high-probability studies, there were 8 deaths by PE, 6 deaths by hemorrhage, 11 nonfatal hemorrhages and 7 patients who experien ced recurrences of PE. The odds ratios in this group were 6 and 10 for deat h by PE, or death by PE and the treatment of PE, respectively. Conclusion: The use of the modified PIOPED diagnostic classification is valid for techn egas lung scintigraphy. Using technegas, normal/low-probability and high-pr obability results are highly predictive of respective outcomes. Technegas l ung scintigraphy reduces the number of indeterminate studies.