Among patients who had undergone previous coronary artery bypass graft (CABG) surgery, low global stress myocardial blood flow and myocardial perfusion reserve were found to be independent predictors of adverse outcomes, according to results of a study published in the Journal of the American College of Cardiology.

This single-center, retrospective cohort study was conducted at Barts Heart Centre in the United Kingdom. Patients (N=341) who had undergone previous CABG surgery and had adenosine stress myocardial perfusion cardiac magnetic resonance imaging data available were included. The primary outcome was a composite of death and major adverse cardiovascular events (MACE, including nonfatal myocardial infarction and unplanned coronary revascularization).

The patient cohort comprised 86% men, mean age was 67±10 years, median body mass index (BMI) was 28 (interquartile range [IQR], 25-31) kg/m2, left ventricular ejection fraction was 61% (IQR, 50-68), the interval between CABG and cardiac magnetic resonance imaging was 9 (IQR, 3-15) years, and the most common indication for undergoing the imaging study was typical chest pain (48%).


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During cardiac magnetic resonance imaging, median stress myocardial blood flow was 1.49 (IQR, 1.18-1.90) mL/g/min and median myocardial perfusion reserve was 2.03 (IQR, 1.63-2.57). Stratified by the presence of an inducible visual perfusion defect, those with a defect had significantly lower stress myocardial blood flow (median, 1.44 vs 1.73 mL/g/min; P <.001) and myocardial perfusion reserved (median, 1.99 vs 2.21; P =.007).

In multivariate regression analysis, stress myocardial blood flow was independently associated with age (b, -0.013; P <.001), global late gadolinium enhancement (b, -0.008; P =.003), and female sex (b, 0.149; P =.045), and myocardial perfusion reserve was associated with age (b, -0.019; P <.001) and diabetes (b, -0.241; P <.001).

During a median follow-up of 638 days, 81 patients (24%) experienced 85 primary endpoint events. In total, 36 unplanned revascularizations, 25 deaths, and 24 myocardial infarctions were reported among the study population.

Male sex, previous percutaneous coronary intervention, visual perfusion defect, lower global stress myocardial blood flow, lower stress myocardial blood flow in segments without late gadolinium enhancement, and lower global myocardial perfusion reserve (all P £.038) were factors associated with an outcome event.

In the final model, every one standard deviation decrease in stress myocardial blood flow (adjusted hazard ratio [aHR], 1.59; 95% CI, 1.20-2.08; P <.001) or myocardial perfusion reserve (aHR, 1.35; 95% CI, 1.05-1.75; P =.020) increased the risk for the primary outcome.

A cutoff of stress myocardial blood flow £1.48 mL/g/min (P <.001) or myocardial perfusion reserve £2.12 (P =.041) was associated with significantly lower event-free survival.

This study was limited as the cause of death was unknown for the majority of patients.

This study found that global stress myocardial blood flow and myocardial perfusion reserve as detected by cardiac magnetic resonance imaging were independent predictors of mortality and MACE among patients who had undergone previous CABG surgery. These results suggest that quantitative perfusion measures should be investigated further in this patient population.

Reference

Seraphim A, Dowsing B, Rathod KS, et al. Quantitative myocardial perfusion predicts outcomes in patients with prior surgical revascularization. J Am Coll Cardiol. 2022;79(12):1141-1151. doi:10.1016/j.jacc.2021.12.037