Diagnostic Accuracy of Endocardial-to-Epicardial Myocardial Blood Flow Ratio for the Detection of Significant Coronary Artery Disease With Dynamic Myocardial Perfusion Dual-Source Computed Tomography

Abstract

limited response to vasodilator stress, resulting in globally reduced hyperemic MBF. 15 Because the endocardial layer is most susceptible to ischemia, 16,17 the ratio of endocardial MBF and epicardial MBF might be a more useful indicator of flow-limiting CAD.The purpose of this study was to investigate whether the transmural ratio of absolute MBF can improve the accuracy of CTP when compared with absolute MBF for the detection of flow-limiting CAD, as defined by fractional flow reserve (FFR). We also explored the prevalence of myocardial scar in candidates for CTP and its effect on the diagnostic performance of CTP. Methods Study PopulationIn the comprehensive cardiac CT registry at Mie University C oronary computed tomography angiography (CCTA) allows noninvasive assessment of the morphology of coronary artery stenosis and is highly useful for ruling out the presence of obstructive coronary artery disease (CAD). 1,2 However, because obstructive stenosis identified by CCTA is a poor predictor of the presence of myocardial ischemia, a functional test is generally recommended to investigate the hemodynamic significance of the stenotic lesion. 3 Stress dynamic CT perfusion (CTP) with absolute quantification of myocardial blood flow (MBF) is a new noninvasive technique for the assessment of myocardial ischemia. 4,5 Previous CTP studies used absolute MBF thresholds in mL/100 g/min to discriminate flow-limiting CAD, 6-10 but the absolute MBF can vary because of factors other than the degree of coronary artery stenosis. Yoshitaka Goto, MD; Kakuya Kitagawa, MD; Mio Uno, MD; Shiro Nakamori, MD; Tatsuro Ito, MD; Naoki Nagasawa, PhD; Kaoru Dohi, MD; Hajime Sakuma, MD Background: Previous dynamic stress computed tomography perfusion (CTP) studies used absolute myocardial blood flow (MBF in mL/100 g/min) as a threshold to discriminate flow-limiting coronary artery disease (CAD), but absolute MBF can be vary because of multiple factors. The aim of this study was to compare the diagnostic performance of absolute MBF and the transmural perfusion ratio (TPR) for the detection of flow-limiting CAD, and to clarify the influence of CT delayed enhancement (CTDE) on the diagnostic performance of CTP.

Clinical quantitative cardiac imaging for the assessment of myocardial ischaemia

“…Future developments. Two-compartment analysis might reduce underestimation of MBF by CT 163,164 , and the semiquantitative transmural perfusion ratio might improve diagnosis of myocardial ischaemia compared with using the MBF 165 . Low kilovolt scanning (70-80 kV) enables a substantial reduction in radiation dose, while increasing contrast-to-noise ratio 166 .…”

Dynamic CT Perfusion Imaging: State of the Art

“…Diagnostic performance of dynamic CTP has been validated against different reference standards including MRI [42][43][44][45], SPECT [43,46,47], and coronary angiography with FFR measurement [21,27,[48][49][50][51][52][53]. Available data are scarce on the diagnostic performance of dynamic CTP for detecting perfusion defects determined by MRI or SPECT.…”

“…In addition, hyperemic MBF in remote myocardium can be influenced by other factors such as age, gender, race, BMI, insulin resistance, arteriolar response to vasodilators, and presence of collateral vessels [54][55][56][57]. Debatably, relative MBF normalized by remote MBF may provide more accurate identification of hemodynamically significant CAD than abso-lute MBF [49,53]. We should also recognize that FFR is a measure of lesion specific hemodynamic significance of stenosis, not a measure of myocardial perfusion, which is governed by not only epicardial coronary stenosis, but also microvascular environment and collateral circulation.…”

“…Unfortunately, CTDE is not widely used due to low contrast-to-noise ratio; however, its quality has been significantly improved with the recent advancement in image acquisition, reconstruction, and postprocessing [67][68][69]. Assessment of myocardial delayed enhancement appears to be especially important in the delineation of ischemic but viable myocardium in patients with history of myocardial infarction and/or prior stent implantation [53]. Moreover, CTDE may be used to estimate extracellular volume fraction of the left ventricular myocardium [70,71].…”

“…Vessel-based diagnostic accuracy of dynamic CT perfusion compared with invasive coronary angiography with fractional flow reserve for the diagnosis of hemodynamically significant coronary artery disease MBF was presented in mL/100 mL/min. *best diagnostic performance was achieved based on relative MBF cut-off (Kono et al[49] MBF ratio of 0.85; Goto et al[53] transmural perfusion ratio of 0.899), † conversion factor=0.017, ‡ conversion factor=0.014. N: number of patients, MBF: myocardial blood flow, NPV: negative predictive value, PPV: positive predictive value, SE: sensitivity, SP: specificity…”