Quantitative CMR may independently Predict Adverse Outcomes in In patients with Prior CABG

Quantitative myocardial perfusion indices predict outcomes in native vessel disease, but their prognostic performance in patients with prior CABG is unknown. Therefore, Dr Andreas Seraphim and his team conducted a study to evaluate whether global stress MBF and MRF derived from perfusion mapping CMR independently predict adverse outcomes in patients with prior CABG.

It was a retrospective analysis of 341 patients with prior CABG referred for adenosine stress perfusion CMR. The researchers performed perfusion mapping in line with automated quantification of MBF. The major outcome assessed was a composite of all-cause mortality and major adverse cardiovascular events defined as nonfatal myocardial infarction and unplanned revascularization. They further evaluated the associations with the use of Cox proportional hazards models after adjusting for comorbidities and CMR parameters.

Key findings of the study:

• Upon median follow-up of 638 days, the researchers observed that 81 patients (24%) among 341 reached the primary outcome.
• They found that both stress MBF and MPR independently predicted outcomes after adjusting for known prognostic factors (regional ischemia, infarction).
• They noted that the adjusted hazard ratio (HR) for 1 mL/g/min of decrease in stress MBF was 2.56 (95% CI: 1.45-4.35) and for 1 unit of decrease in MPR was 1.61.

The authors concluded, "Global stress MBF and MPR derived from perfusion CMR independently predict adverse outcomes in patients with previous CABG. This effect is independent from the presence of regional ischemia on visual assessment and the extent of previous infarction."

In an accompanying editorial, Dr Raymond Y. Kwong wrote, "the findings by Seraphim et al, demonstrate that reduced MBF and MPR according to quantitative stress CMR identify high-risk patients beyond clinical history alone. Future studies with CMR-derived flow quantification in patients after CABG should also be considered in patients with other disease states, such as post-transplantation allograft vasculopathy or diastolic dysfunction, in whom epicardial stenoses, nonobstructive disease, and microvascular dysfunction also play a role in adverse outcomes."

For further information:

DOI: https://www.jacc.org/doi/10.1016/j.jacc.2021.12.037

Keywords:

Perfusion reserve, CABG, Mapping, Blood flow, myocardial blood flow, myocardial infarction, cardiac magnetic resonance, MACE, revascularization, Adverse Cardiac outcomes, Journal of the American College of Cardiology