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I read with great interest the study by Kato et al. (1). In their study, they found that in patients with known or suspected coronary artery disease (CAD), a lower coronary flow reserve measured by phase-contrast cine magnetic resonance imaging of the coronary sinus predicted the occurrence of major adverse cardiac events. The difference in flow reserve in their patients with major adverse cardiac events compared with all patients appears to be solely on the basis of higher resting flows (37% in patients with known CAD and 45% in patients with suspected CAD). There were no significant differences in the peak flows after adenosine triphosphate infusion in either group.
Similarly, I found that a fall in resting coronary blood flow to be the sole factor responsible for higher significant flow reserve, whereas peak flows were not significantly changed. Resting flow predicted successful revascularization in 23 consecutive patients. I studied by positron emission tomography scan with rubidium. Resting flow fell by 25.00 ± 3.06% following revascularization in 19 patients (p < 0.05). Resting flow went up in only 4 patients, and 3 of those had residual ischemia demonstrated on their perfusion study.
My findings and those of Kato et al. (1) suggest that resting coronary blood flow is more important than peak flow in the calculation of coronary flow reserve. Compensatory decreases in microvascular resistance in response to epicardial disease cause resting flow to increase in dogs (2) and in humans (3). After successful intervention (percutaneous coronary intervention or coronary artery bypass graft), the microvasculature returns to near baseline levels and resting coronary flow goes down.
Please note: Dr. Lichtenberg has reported that he has no relationships relevant to the contents of this paper to disclose.
- 2017 American College of Cardiology Foundation