Abstract
We hypothesized that in patients with QT prolongation, resistance might not decrease in the wave-free period, because QTU prolongation cannot be detected by instantaneous wave-free ratio (iFR) analysis software. We investigated whether corrected QTU (QTUc) prolongation affects the hyperemic iFR value. Forty-two consecutive patients with intermediate stenosis (≥ 50%) in the left anterior descending coronary artery (LAD) were analyzed. Fractional flow reserve (FFR) and hyperemic iFR were simultaneously and continuously recorded with intravenous adenosine triphosphate (ATP) and papaverine infusions. In 17 patients with stenosis in the proximal LAD, coronary flow was measured. Patients were divided into two groups according to the median absolute deviation of the QTUc by ATP administration/QTUc by papaverine administration. FFR, hyperemic iFR, and flow data were compared between each stimulus and group. Moreover, influences of pressure and electrocardiogram parameters on differences in iFR values under ATP and papaverine administration were compared between the following two groups (group 1: the absolute difference of hyperemic iFR values between ATP and papaverine administration is ≤ 0.05; group 2: that is > 0.05). The paired t test and t test were used in analysis. Hyperemic iFR values of patients under the use of papaverine were lower than those of patients under the use of ATP when QTUc was more prolonged by papaverine administration than by ATP administration (ATP 0.74 ± 0.14, papaverine 0.71 ± 0.15, P = 0.025). No significant differences were observed in the FFR value and flow data between the groups. Regarding QTU, QTUc, and QTUc by ATP/QTUc by papaverine, significant differences were observed between group 1 and group 2. Pressure parameters did not induce significant differences. QTUc prolongation induced by papaverine was associated with lower hyperemic iFR values. An iFR-based assessment might lead to inappropriate treatment of patients with QTUc prolongation.
Highlights
Fractional flow reserve (FFR) is recognized as the primal assessment in determining whether a stable stenotic coronary artery lesion should be interventionally treated [1,2,3,4,5,6]
FFR values were comparable between adenosine triphosphate (ATP) and papaverine administration (Fig. 2a)
FFR and hyperemic instantaneous wave-free ratio (iFR) values were comparable between ATP and papaverine administration, respectively, in the patients who did not show QTUc prolongation after papaverine administration
Summary
Fractional flow reserve (FFR) is recognized as the primal assessment in determining whether a stable stenotic coronary artery lesion should be interventionally treated [1,2,3,4,5,6]. Under minimized flow resistance, the FFR value calculated from the coronary artery distal pressure (Pd) and aortic pressure (Pa) as Pd/Pa over the whole cardiac cycle is used as the index of flow of the lesion [7,8,9]. A coronary revascularization strategy guided by the instantaneous wave-free ratio (iFR), which can be measured without the need of administering hyperemic. Regarding the FFR-based diagnosis, diastolic FFR has attracted attention for improving accuracy, because high coronary blood flow occurs during diastole in the left anterior descending coronary artery (LAD). Some reports showed that diastolic FFR calculated using electrocardiography or left-ventricular pressure might improve diagnostic accuracy of ischemia in comparison with FFR [14,15,16]. The iFR value is calculated as the ratio of mean Pd/Pa during the diastolic wave-free period (WFP). We hypothesized that in patients with QT prolongation after intracoronary papaverine, microvascular resistance might not decrease enough even in the mid-to-end-diastolic phase, because T and U waves represent repolarization of the ventricular muscle [18,19,20]
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