Post-PCI Angiographic Microcirculatory Resistance and 3-Year Cardiac Events in FAVOR III ChinaHigh blood vessel resistance after heart procedure linked to higher heart attack risk

This study is a post hoc analysis of the FAVOR III China trial, a randomized controlled trial conducted in a Chinese setting. The population included 3,404 patients undergoing percutaneous coronary intervention (PCI). The analysis focused on the prognostic value of Angiographic Microcirculatory Resistance (AMR), a measure of coronary microcirculation, which was measured both before and after PCI. The primary outcome was the 3-year risk of major adverse cardiac events, defined as a composite of all-cause death, myocardial infarction, or ischemia-driven revascularization. The median follow-up period was 36.0 months.

The intervention in this analysis was the measurement of AMR. The comparator was defined as a percentage change in AMR before and after PCI of less than 85%. The analysis stratified patients based on their post-PCI AMR values to explore differential outcomes. The study aimed to determine if AMR, particularly after intervention, could predict long-term cardiovascular risk in this patient cohort.

For the primary outcome, the 3-year risk of major adverse cardiac events was found to be similar between groups defined by the percentage change in AMR. The risk was 14.8% in one group versus 12.4% in the other. The effect size was a hazard ratio (HR) of 1.18, with a 95% confidence interval (CI) of [0.95-1.45]. The result was not statistically significant, as indicated by a log-rank p-value of 0.064. This suggests that, overall, the percentage change in AMR did not significantly predict the primary outcome.

Key secondary outcomes, derived from subgroup analyses, revealed important risk stratification. In a subgroup of patients with a post-PCI AMR ≥250, there was a significant increase in the risk of major adverse cardiac events. The event rate was 16.3% in this subgroup compared to 10.8% in the reference group. The hazard ratio was 1.52, with a 95% CI of [1.14-2.04], indicating an increased risk. Conversely, in the subgroup with a post-PCI AMR <250, there was no significant difference in risk. The event rate was 12.3% versus 13.4%, with an HR of 0.89 (95% CI [0.63-1.25]).

The analysis did not report on adverse events, serious adverse events, discontinuations, or overall tolerability, as these were not part of the post hoc analysis scope. The safety profile of the AMR measurement procedure itself is therefore not detailed in these findings.

Several key methodological limitations must be considered. The study is explicitly noted as a post hoc analysis, which increases the risk of bias and limits definitive conclusions. Furthermore, the prognostic significance of AMR in patients undergoing PCI remains insufficiently established. The findings are from a single trial (FAVOR III China), which may limit generalizability to other populations or healthcare settings. The lack of reported secondary outcomes beyond the subgroup analyses and the absence of safety data are also notable limitations.

The clinical implications of these findings are nuanced. While a general elevation in AMR pre- or post-PCI did not predict outcomes, a specific threshold of post-PCI AMR (≥250) identified a patient subgroup at increased 3-year cardiovascular risk. This suggests that post-PCI AMR could be a potential tool for risk stratification, but its prognostic significance is not yet fully established for routine practice. The association between AMR and major adverse cardiac events does not imply causality.

Several questions remain unanswered. The prognostic significance of AMR in patients undergoing PCI needs to be established in prospective studies. It is unknown if interventions based on AMR values would improve outcomes. The generalizability of these findings to populations outside of China requires investigation. Further research is needed to validate the AMR threshold of 250 and to understand the clinical utility of this measurement in guiding post-PCI care.