Studies of patients with massive pulmonary embolism in haemodynamic shock that reported results of treatment with modern catheter-directed therapy (in at least three consecutive patients) were eligible for inclusion. In studies that included patients without hypotension or that used outdated catheter-directed therapy techniques, data pertaining to hypotensive patients that received modern catheter-directed therapy was included.
Modern catheter-directed therapy was defined as: use of low-profile catheters and devices (10F or less, i.e. 0.33 mm diameter or less); catheter-directed mechanical fragmentation and/or aspiration of emboli using any catheter type, and intra-clot thrombolytic injection if a local drug was infused. Clinical success was defined as stabilisation of haemodynamics, resolution of hypoxia, and survival of a massive pulmonary embolism, as reported in the primary study.
The included studies were performed in a variety of countries in Europe, Asia, South America and in the USA. The mean age of the included patients ranged from 33 to 68 years. The majority of included patients did not receive systemic thrombolytic therapy and were treated with catheter-directed therapy as the first adjunct to heparin anticoagulation. Catheter-directed therapy was initiated by mechanical means alone in one third of patients (where reported). Local thrombolysis used was tissue-type plasminogen activator, tenecteplase, urokinase or streptokinase. The most common mechanical intervention used was rotating pigtail fragmentation of emboli with/without other catheter manoeuvres.
Study selection was performed by more than one reviewer and there were no disagreements.