Comparative clinical and cost effectiveness of non-ST elevation myocardial infarction management strategies in patients living with kidney impairment during the COVID-19 pandemic: protocol for a target trial emulation using English routinely collected health data

Introduction: Recent national and international guidelines recommend an invasive cardiac investigation and treatment strategy for people at high risk of cardiovascular events, regardless of kidney function status. These guidelines are based on observational evidence suggesting that the benefits of invasive cardiac investigation and treatment versus conservative management for non-ST elevated myocardial infarction (NSTEMI) outweigh the risks for people with kidney impairment. Despite this, among people with kidney impairment there is substantial variation in the proportions who have early invasive versus conservative NSTEMI management across hospitals in England. The impact of the COVID-19 pandemic on this variation is unknown. This protocol describes a study to investigate this variation and any changes during the COVID-19 pandemic, and how this variation will be used to evaluate the comparative clinical and cost-effectiveness of alternative NSTEMI treatment strategies among people with reduced kidney function.

Methods and analysis: The CVD-COVID-UK/COVID-IMPACT British Heart Foundation (BHF) Data Science Centre Secure Data Environment, which contains nationally representative linked data on over 50 million people living in the United Kingdom, will be used to define a cohort of people hospitalised for NSTEMI. We will use linked secondary care data (Hospital Episode Statistics and National Institute for Cardiovascular Outcomes Research Audit) for cases with recent evidence of kidney impairment in primary care data (General Practice Extraction Service Data for pandemic planning and research) between 2019 and 2024. First, we will describe variation in early invasive versus conservative NSTEMI management at the hospital-level before and during the COVID-19 pandemic. Second, we will emulate a hypothetical trial using the target trial emulation framework to evaluate the comparative and cost-effectiveness of early invasive versus conservative NSTEMI management among people with reduced kidney function. We will use advanced analytical methods (clone-censor-weighting and instrumental variable analyses) to minimise the risk of bias due to immortal time and confounding by indication.

Ethics and dissemination: This study was reviewed and approved by the BHF Data Science Centre Scientific and Public Panels. Results will be published in peer-reviewed journals, presented at conferences, and shared at patient and public panels. Analysis code will be shared in line with the BHF Data Science Centre’s code-sharing procedures.