Comparison of clinical features and outcome in massive and non-massive pulmonary embolism

Background: Acute pulmonary embolism (PE) continues to be a challenge because of diagnostic uncertainty and high mortality. Massive PE (M-PE), furthermore, carries a more severe outcome than non-massive PE (NM-PE). We designed this case-control study to examine the complementary roles of non-imaging and imaging studies in early differentiation of M-PE from NM-PE. Methods: From 1998 to 2002, 301 consecutive patients admitted from the Emergency Room of Mackay Memorial Hospital with acute chest pain or dyspnea were screened for possible PE. Diagnosis of PE was considered confirmed by high-probability lung perfusion scan or positive pulmonary angiography. Screened patients with hypotension or shock were classified as having M-PE and the remaining as having NM-PE. All patients underwent both non-imaging and imaging studies. Results: Sixty-five of the 301 patients, ranging in age from 25 to 84 years and fulfilling the criteria for PE, were enrolled in the study. Twenty-five were classified as having M-PE, and the remaining 40 as having NMPE. Predisposing factors, and age and sex distributions were similar in both groups. Compared with NM-PE patients, M-PE patients were more likely to present with: syncope or cyanosis; sinus tachycardia or new-onset right bundle branch block on ECG; and cardiomegaly or an engorged hilum on chest radiograph (p < 0.05). Profound hypoxemia and a wide alveolar-arterial oxygen gradient (AaDO₂) were more common in patients with M-PE (p < 0.01). Subsequent transthoracic echocardiography (TTE) demonstrated a higher occurrence rate of right ventricular dysfunction with regional wall-motion abnormalities in those with M-PE (p < 0.01); they also had a higher mortality rate and experienced more bleeding events during hospitalization (p < 0.05). Conclusions: Given the high mortality of M-PE, when patients are suspected of having a PE and have any of the manifestations that we found to be associated with M-PE, aggressive diagnostic and therapeutic intervention is warranted. TTE is important in diagnosis as well as risk stratification. Further, large cohorts are necessary to define more precisely the usage of non-imaging or imaging techniques to differentiate M-PE from NM-PE.