Background:
Instantaneous wave-free ratio (iFR) is a vasodilator free index calculated using trans-lesional pressure ratio during a specific period of diastole that is called “wave-free period”, and reported to have a good correlation with fractional flow reserve (FFR). In patients with severe aortic valve stenosis (AS), evaluation of intermediate coronary stenosis by FFR using vasodilators is thought to be a contraindication in some situations. Moreover, previous studies reported unique coronary flow pattern during diastolic phase in patients with AS. To date, there is no report claiming the correlation of iFR and FFR in this population. The purpose of the present study was to examine the clinical value of iFR in patients with AS.
Method and Results:
We examined consecutive 154 patients (with 214 stenosis) whose iFR and FFR were measured simultaneously. The mean age of AS patients (n=10, mean aortic valve area: 0.75 ± 0.42cm2) was higher than non-AS patients (n=144). Other patients’ characteristics are shown in Table 1. The mean iFR value in AS patients was significantly lower than that of non-AS patients, despite no significant difference was observed in the mean FFR value and % diameter stenosis (Table 2). iFR showed a good correlation with FFR in AS patients (Figure 1) and the best cut-off value of iFR in receiver operator curve analysis to predict FFR ≤ 0.8 was 0.73 in AS patients (AUC 0.84, sensitivity 0.8, specificity 0.86, p=0.016; Figure 2), whereas, 0.90 in non-AS patients.
Conclusion:
The present study demonstrated the good correlation between iFR and FFR in AS patients. Besides, the value below 0.73 of iFR was thought to be a predictor of myocardial ischemia in AS patients, which was lower than standard predictive range of ischemia in iFR. Vasodilator-free assessment by iFR may have potential benefits in evaluating intermediate coronary stenosis in patients with AS.
DETERMINANTS OF DISCORDANCE BETWEEN FRACTIONAL FLOW RESERVE AND DIASTOLIC PRESSURE RATIO IN ANGIOGRAPHICALLY INTERMEDIATE CORONARY STENOSIS