Use of Inverse Probability Weighting in Cardiovascular Surgical Outcomes Research: Principles, Limitations, and Recommendations

This statistical primer presents a comprehensive introduction to the use of inverse probability of treatment weighting (IPTW), a method for rebalancing group confounders at baseline in cardiovascular surgical outcomes research. We leveraged a retrospective study comparing the outcomes of 2 different surgical approaches to aortic arch pathology to illustrate the essential aspects of performing IPTW, including basic theories, application, extreme weights, underestimated variance, heterogeneity of treatment effect, and multicollinearity. The limitations of IPTW were discussed with examples of solutions. Ten practical recommendations are made on avoiding the pitfalls in the use of IPTW. Proper use of IPTW may effectively reduce confounding bias by balancing confounders between different groups at baseline, retain a relatively large sample size, and allow for integration with other statistical methods. However, it is crucial to be fully aware of its limitations and carefully select appropriate methods to avoid improper use and data misinterpretation in cardiovascular outcomes research.