Mechanical heart valves between myths and new evidence: a systematic review and meta-analysis

Aims: The use of mechanical valve prostheses in cardiac surgery remains a necessary and indicated intervention in a large number of patients. However, predicted results associated with their use, on which current guideline recommendations have been developed, are based on dated studies at risk of bias (e.g. use of old generation models, very high international normalized ratio regimes). Methods: A comprehensive search in multiple electronic databases was conducted from January 1995 to January 2024 using predefined criteria. The primary outcomes included all-cause death, bleeding events and thromboembolic events (i.e. stroke) at follow-up. Results: Overall, 38 studies were included in the meta-analysis. Cumulative meta-analysis results for mortality, thromboembolic events and bleeding events were initially extremely variable and tended to become more consistent over time. A meta-regression for the impact of age and sex on mortality showed no difference, whereas a meta-regression for the impact of age and sex on thromboembolic events and on bleeding events showed a higher risk in the elderly and in female patients, respectively. Conclusion: The lack of fundamental information on the type of anticoagulant treatment (e.g. dosage, monitoring method) in the studies published to date does not allow us to draw any definitive conclusions on the outcomes of mechanical valve prostheses. The most recent studies have provided more consistent results, which in the past were highly variable, probably due to overcoming the bias in the use of prosthetic models of different generations.