Autopsy-proven untreated previous pulmonary thromboembolism: frequency and distribution in the pulmonary artery and correlation with patients' clinical characteristics.

BACKGROUND

This study aimed to evaluate untreated, previous pulmonary thromboembolism (PE) in patients with acute fatal PE.

PATIENTS AND METHODS

We studied 64 patients diagnosed as having died from acute PE by medico-legal autopsy. Previous PE was histologically confirmed on the basis of organized thrombi (OT). The distributions of OT were analyzed in five different sizes of pulmonary artery branches in each of 18 pulmonary segmental arteries (90 in total). The frequency of OT in each patient was evaluated by determining the percentage of examined sections containing OT.

RESULTS

OT were confirmed in 59 of 64 (92%) patients. The mean frequency of OT per patient was 27% of the 90 branches. Among the segmental arteries, the right posterior basal lobe showed the highest frequency of OT; among the five artery branches examined, the subsegmental branch showed the highest frequency of OT. OT were not detected in arterioles. Patients with recent trauma or surgery and inpatients showed significantly lower frequencies of OT than those without these risk factors. The 26 patients with prolonged pre-existing symptoms lasting more than a day showed a higher frequency of OT than the 12 patients who suffered for less than a day and the 26 without pre-existing symptoms.

CONCLUSIONS

Most patients with acute fatal PE have a subclinical history of recurrent PE. The frequency of their untreated PE is suspected to correlate with specific risk factors for venous thromboembolism and their clinical course.