Coronary flow reserve (CFR) decreases in the presence of significant coronary stenosis. Hence, CFR can be used for the detection of restenosis after percutaneous coronary intervention (PCI). However, because CFR can also be affected by other conditions such as endothelial dysfunction, microvascular damage, and left ventricular hypertrophy, the absolute value of CFR is not routinely used for detection of coronary restenosis. We hypothesized that changes in the value of CFR, rather than the absolute CFR value, are better correlated with restenosis in various clinical settings.

We studied 99 patients (71 males/28 females, mean age 58±11 years) who underwent successful PCI of the left anterior descending artery. Pre-PCI diagnoses were as follows: 37 unstable angina, 35 stable angina, 27 acute myocardial infarction. CFR using transthoracic Doppler was measured at 48 hours after PCI and at the time of follow-up angiography (6.0±1.5 months later). Coronary flow velocity was measured in the distal left anterior descending artery with a 7 MHz transducer (HDI 5,000, Philips, The Netherlands) at baseline and during intravenous infusion of adenosine (140 µg·kg^-1·min^-1). Mean diastolic coronary flow velocities from at least three cardiac cycles were averaged.

CFRs in 69 patients without restenosis were 2.55±0.99 at 48 hours after PCI and 2.93±1.00 at follow-up (p<0.005). CFRs in 30 patients with restenosis (>50% in diameter stenosis) decreased significantly from 2.70±1.01 at 48 hours after PCI to 1.98±0.91 at follow-up (p<0.001). There was a significant difference in CFR change (ratio of CFR_followup/CFR_initial) between the two groups. CFR change had a better receiver operating characteristics (ROC) curve than absolute CFR for prediction of restenosis [area under the curve (AUC) for absolute CFR=0.76, AUC for CFR change=0.82].

Restenosis after PCI leads to a significant decrease in CFR, even in the presence of variable baseline CFR values. Serial measurements of CFR can be used to detect restenosis after PCI.