Duration of Pulmonary Embolism Presence
Pulmonary arterial patency is restored in the majority of PE survivors within the first few months following the acute episode, with lung perfusion abnormalities persisting in approximately 35% of patients at one year, though the degree of vascular obstruction is typically minimal (<15%) in 90% of these cases. 1
Natural Resolution Timeline
The resolution of pulmonary thrombi follows a predictable pattern after acute PE:
First few months: The pulmonary arterial bed patency is restored in most PE survivors during this period, which is why routine follow-up CTPA imaging is not recommended in patients treated for PE 1
One year post-PE: Lung perfusion scintigraphy demonstrates persistent abnormalities in 35% of patients, though the degree of pulmonary vascular obstruction remains <15% in 90% of cases 1
Incomplete resolution: In some patients, thrombi become persistent and organized rather than fully resolving 1
Risk of Chronic Complications
The incidence of chronic thromboembolic pulmonary hypertension (CTEPH) after unprovoked PE is approximately 1.5%, with most cases appearing within 24 months of the index event. 1
CTEPH represents a rare but potentially life-threatening obstructing vasculopathy that develops when thrombi fail to resolve and become organized 1
This condition is distinct from acute PE and, if untreated, is usually fatal within 2-3 years following initial detection 1
Clinical Implications for Follow-Up
The goals of post-PE follow-up should address two key concerns 1:
Persistent symptoms management: Provide appropriate care (exercise rehabilitation, treatment of comorbidity, behavioral education, risk factor modification) to patients with persisting dyspnoea or poor physical performance over several months after acute PE
Early CTEPH detection: Ensure timely identification of CTEPH to refer patients for further diagnostic workup and specific treatment
Between 20-75% of patients report that their health status is worse at 6-month follow-up than at the time of PE diagnosis, with 47% demonstrating reduced maximal aerobic capacity (peak oxygen consumption <80% predicted) at one year 1
Recurrence Timeline Without Treatment
Historical data on untreated PE demonstrates the natural history of recurrent events 1:
Untreated PE mortality: 25-30% mortality rate, primarily due to recurrent embolic events 1
Multiple emboli at autopsy: 15-60% of fatal PE cases show multiple PEs and infarcts of different ages (recent, organizing, and organized), indicating successive emboli over preceding weeks 1
Preceding smaller PEs: The onset of massive PE is often preceded in recent weeks by smaller PEs that escape clinical attention 1