Morris TA; University of California San Diego, La Jolla, CA, USA
Dakaeva K; Alotaibi M; McGuire WC; et al

European Respiratory Journal. 68(2), 2026 Aug.

BACKGROUND: Chronic dyspnoea and exercise impairment are common after
acute pulmonary embolism (PE) but poorly characterised. We performed a
prospective observational study to validate an algorithm to diagnose
discrete post-PE outcomes, including chronic thromboembolism phenotypes.

METHODS: Six pulmonologists independently reviewed records from 150
consecutive patients >=3 months after acute PE who had undergone a
stepwise diagnostic algorithm (SEARCH), which incorporates Symptom
screening, cardiopulmonary Exercise testing, pulmonary Arterial perfusion
scans, Resting echocardiography, Confirmatory imaging, and Haemodynamic
measurements by rest and exercise right heart catheterisation (RHC).
Clinical data were reviewed after the first post-PE evaluation and then 6
months later.

RESULTS: Symptomatic recovery was most common and occurred in 66.2% of
patients during the final evaluation. Dyspnoea without discernible
physiological defects occurred in 2.1% and dyspnoea from alternative
diagnoses in 19.7%. Chronic thromboembolism phenotypes were diagnosed in
12.0% of patients. Chronic thromboembolism with ventilatory inefficiency
and/or small stroke volume augmentation during exercise was seen in 6.3%:
2.1% without pulmonary hypertension on RHC and 4.2% in whom RHC was not
performed. Chronic thromboembolic pulmonary hypertension and chronic
thromboembolism with exercise-induced pulmonary hypertension occurred in
2.1% and 3.5%, respectively. Krippendorff’s alpha among the readers was
0.984 (95% CI 0.9663-0.9960), signifying very high diagnostic reliability.
No patient developed chronic thromboembolism between the first and final
evaluations.

CONCLUSIONS: Dyspnoea from chronic thromboembolism is common after acute
PE, most of which is not associated with pulmonary hypertension. The
SEARCH protocol reliably identifies chronic thromboembolism phenotypes
after acute embolism. Validation of the SEARCH algorithm offers clinicians
a straightforward method to diagnose post-PE conditions that are rarely
distinguished clinically. Improved categorisation and definition of
post-PE conditions will enhance clinical follow-up and allow more precise
end-point adjudication in clinical trials of acute PE treatment.