Diagnostic Performance Of Detecting Specific Ischemia In Patients With Intermediate Coronary Stenosis:CT-derived Fractional Flow Reserve Versus CT Myocardial Perfusion Imaging

Objective:To compare the diagnostic accuracy of CT-derived fractional flow reserve（CTFFR）with CT myocardial perfusion imaging（CTMPI）for detecting the specific ischemia of moderate（intermediate）coronary stenosis（50%-70%）,using fractional flow reserve（FFR）under the guidance of invasive coronary angiography（ICA）as reference standard,and formulate a preliminary optimal application strategy.Materials and Methods:Between April 2019 and March 2022,consecutive patients with suspected or known coronary artery disease were prospectively enrolled.All participants underwent coronary computed tomography angiography（CCTA）+CTMPI and ICA+FFR within 10 days.Inclusion criteria:The intermediate coronary arteries stenosis was confirmed by ICA quantitative analysis and FFR was measured.CCTA and adenosine stress dynamic CTMPI were performed with a third generation dual-source CT.CTFFR andΔCTFFR（the difference between proximal and distal of stenosis）value of coronary artery stenosis was calculated by Siemens CTFFR prototype software.The incremental heart rate of adenosine loading was 16.85±10.70 bmp during CTMPI.American Heart Association（AHA）17-segment myocardial model was used to measure myocardial blood flow（MBF）and calculate relative MBF（r MBF）.FFR≤0.80 was used as the reference standard for myocardial ischemia,and ROC curve was used to assess the diagnostic performance of CTFFR,ΔCTFFR,CTMPI（MBF）and CTMPI（r MBF）for detecting the specific ischemia of intermediate coronary artery stenosis.Results:A total of 35 patients（including 28 males and 7 females,aged 58.94±7.93 years old）was included.33 patients had one coronary artery intermediate stenosis and 2 patients had two coronary artery intermediate stenosis.A total of 37 coronary arteries in 35patients（27 left anterior descending,5 left circumflex and 5 right coronary arteries）had intermediate stenosis（ICA quantitative analysis showed that the degree of stenosis was65.20%±8.40%）.Among them,the FFR≤0.80（indicating myocardial ischemia）was29,and the FFR>0.80（indicating no myocardial ischemia）was 8.In the 29 intermediate coronary stenosis with FFR≤0.80,19 intermediate stenosis had FFR<0.75,and 10intermediate stenosis in the"gray zone"（0.75-0.80）.（1）In 37 intermediate stenosis coronary arteries,CTFFR was lower for hemodynamically significant lesions than for hemodynamically nonsignificant lesions（P<0.001）,0.56±0.18 and 0.89±0.06,respectively.There was a moderate correlation between CTFFR and FFR（r=0.48,P=0.001）.The intraclass correlation coefficient was high（ICC=0.838）.（2）The MBF value of the myocardial area supplied by intermediate stenotic vessels was lower than the reference myocardial segment,107.84±22.91 ml·100 ml^-1·min^-1 and 171.13±17.56ml·100 ml^-1·min^-1,respectively,P<0.001.The intraclass correlation coefficient was high（ICC=0.998）.（3）Among the 10 coronary stenosis with FFR in the"gray zone"（0.75-0.80）,CTFFR made a false-negative diagnosis for one stenotic lesion,ΔCTFFR had no false-negative diagnosis,CTMPI（MBF）made a false-negative diagnosis for four stenotic lesions,and CTMPI（r MBF）made a false-negative diagnosis for one stenotic lesion.（4）With FFR≤0.80 as a positive event,the area under the curve（AUC values）of CTFFR,ΔCTFFR,CTMPI（MBF）and CTMPI（r MBF）were 0.886,0.856,0.720 and 0.836,respectively.The diagnostic performance of CTFFR was slightly better thanΔCTFFR,CTMPI（MBF）and CTMPI（r MBF）,but there was no statistical significance（P=0.676,0.278 and 0.699,respectively）.The diagnostic performance of CTMPI（r MBF）was higher than CTMPI（MBF）（P=0.018）.（5）On a per-vessel basis,the sensitivity,specificity,negative predictive value,positive predictive value and accuracy of CTFFR for detecting specific ischemia of intermediate coronary artery stenosis were 89.66%,87.50%,70.00%,96.30%and 89.19%with FFR as the reference standard,respectively.The optimal cut-off value ofΔCTFFR was 0.04.The sensitivity,specificity,negative predictive value,positive predictive value and accuracy ofΔCTFFR for detecting specific ischemia of intermediate coronary artery stenosis were 96.55%,62.5%,83.33%,90.32%and 89.19%,respectively.The optimal cut-off value of MBF was 115.15 m L·100 m L^-1·min^-1.The sensitivity,specificity,negative predictive value,positive predictive value and accuracy of CTMPI（MBF）for detecting specific ischemia of intermediate coronary artery stenosis were 75.86%,75.00%,46.15%,91.67%and 75.68%,respectively.The optimal cut-off value of r MBF was 0.736.The sensitivity,specificity,negative predictive value,positive predictive value and accuracy of CTMPI（r MBF）for detecting specific ischemia of intermediate coronary artery stenosis were 96.55%,75.00%,85.71%,93.33%and 91.89%,respectively.（6）The effective radiation dose of CCTA in 35 patients was4.13±1.76 m Sv.The effective radiation dose of CTMPI was 4.05±1.53 m Sv.Conclusions:1.The diagnostic performance of CTFFR for detecting specific ischemia in patients with intermediate coronary stenosis is comparable toΔCTFFR,and both can be used for it.2.The diagnostic performance of CTMPI（r MBF）for detecting specific ischemia in patients with intermediate coronary stenosis is higher than CTMPI（MBF）.r MBF could be used as the preferred index for CTMPI.3.The diagnostic performance of CTFFR and CTMPI for detecting specific ischemia in patients with intermediate coronary stenosis is comparable.For investigating specific ischemia in patients with intermediate coronary stenosis from CCTA,CTFFR should be the preferred method because of its unique advantages（calculated based on CCTA data,without additional CT examinations and without using adenosine）,and CTMPI can be chosen if CTFFR is not applicable for various reasons.