Diagnostic Performance and Pressure Stability of a Novel Myocardial Ischemic Diagnostic Index　― The Intracoronary-Electrocardiogram-Triggered Distal Pressure/Aortic Pressure Ratio ―

Figures

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  Figure 1.. Method of calculation for the intracoronary electrocardiogram (IC-ECG)-based pressure index, and definitions of terms. (A) First, the Q point of the IC-ECG is synchronized with the start points of the systolic phase in the pressure waveform. The IC-ECG-triggered distal pressure (Pd)/aortic pressure (Pa) ratio was defined as the average of Pd/Pa in the period corresponding to the isoelectric line. (B) ∆Pd/Pa is defined as the difference between the minimum and maximum Pd/Pa values during the analysis interval of each index; ∆Pa and ∆Pd are similarly defined as differences between the minimum and maximum values.

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  Figure 2.. Comparison of intracoronary cardiogram-triggered pressure ratio (ICE-T) and surface electrocardiogram-triggered distal pressure/aortic pressure ratio (ECG-T) values with instantaneous flow reserve recorded at rest (iFR-online). ICE-T values were significantly lower than iFR-online values both at rest and during hyperemia. The ECG-T values were lower than those of automatically calculated iFR (iFR-calc), but the difference did not reach statistical significance. DFR, diastolic hyperemia-free ratio.

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  Figure 3.. Scatter plots of resting intracoronary cardiogram-triggered pressure ratio (ICE-T) and instantaneous flow reserve (iFR), as well as resting ICE-T and iFR relative to fractional flow reserve (FFR). There was a good correlation between iFR and ICE-T (r=0.866, P<0.001), and the correlation coefficients of the 2 resting indices relative to FFR were similar (ICE-T, r=0.711; iFR, r=0.718, P<0.001).

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  Figure 4.. Example of an intracoronary electrocardiogram (IC-ECG) and pressure waveform recorded in the left anterior descending coronary artery under maximum hyperemia. The intracoronary cardiogram-triggered pressure ratio (ICE-T) value is smaller than the calculated instantaneous flow reserve (iFR) value by 0.049. The fluctuations in the distal pressure (Pd)/aortic pressure (Pa) ratio, Pa, and Pd during ICE-T analysis intervals are smaller than those based on the wave-free period. The IC-ECG-based analysis could identify the low and stable Pd/Pa phase, even under hyperemia.

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  Figure 5.. Receiver operating characteristic (ROC) curve analysis of resting indices for predicting a fractional flow reserve (FFR) of ≤0.80. The area under the ROC curve (AUC) indicates that the intracoronary cardiogram-triggered pressure ratio (ICE-T) is more accurate than instantaneous flow reserve recorded at rest (iFR-online) for predicting FFR positivity.