Background

Isolated pulmonary embolism (PE) appears to be associateds with a specific clinical profile and sequelae compared to deep vein thrombosis (DVT)-associated pulmonary embolism. It is unclear whether isolated PE should be considered a separate clinical entity, requiring alternative therapy.  

Methods

We performed a systematic review and meta-analysis of studies comparing PE phenotypes. A systematic search of the electronic databases PubMed and CENTRAL was conducted, from inception until February 28th, 2021. Exclusion criteria were irrelevant content, inability to retrieve the article, language other than English or German, the article comprising a review or case study/series, and inappropriate study design. Data on risk factors, clinical characteristics and clinical endpoints were pooled using random-effects meta-analyses.

Results

Forty-six studies with 432,124 PE patients were included. In low risk of bias studies, 30% [95% CI 19-42%] of PE were isolated, vs. 45% [38-52%] in all studies. The Factor V Leiden [OR: 0.47, 95% CI 0.38-0.59] and prothrombin G20210A mutations [OR: 0.56, 95% CI 0.41-0.75] were significantly less prevalent among patients with isolated PE. Female sex [OR: 1.28, 95% CI 1.15-1.42], recent invasive surgery [OR: 1.31, 95% CI 1.23-1.40], a history of myocardial infarction [OR: 2.07, 95% CI 1.85-2.32], left-sided heart failure [OR: 1.69, 95% CI 1.34-2.12], peripheral artery disease [OR: 1.36, 95% CI 1.31-1.42] and diabetes mellitus [OR: 1.23, 95% CI 1.21-1.25] were significantly more frequently represented among isolated PE patients. In a synthesis of clinical outcome data, the risk of recurrent VTE in isolated PE was half that of DVT-associated PE [RR: 0.53, 95% CI 0.41-0.68], while the risk of arterial thrombosis was nearly 3-fold higher [RR: 2.93, 95% CI 1.43-6.02].

Interpretation