Physiologic Assessment by Cardiac CT Mouaz Al-Mallah, MD MSc FACC Associate Professor of Medicine Division Head, Cardiac Imaging King Abdul-Aziz Cardiac Center National Guard Health Affairs Riyadh, Saudia Arabia
The Current State of CAD Dx Noninvasive functional testing does not accurately identify obstructive CHD ~2/3 of patients with positive stress tests in reality have no obstructive CAD 1 28% of patients with negative stress tests actually do have CAD 1 Only 24% of all non-invasive tests accurately predict the presence of CAD 80% of patients with positive non-invasive tests in reality have no obstructive CAD 2 49% of patients with negative non-invasive tests actually do have CAD 2 1 Patel, M. et al. NEJM 2010,362:10 2 Chinnaiyan, et al. JACC 2012, 59: 688 2
Cardiac CT has emerged as a superb noninvasive method for imaging coronary anatomy and identifying obstructive CAD Al-Mallah, M Current cardiovascular Imaging Reports 2016
Source: Cheng et al. JACC CV Imaging 2008 Is there a severe stenosis? Stenosis Severity 0-24% 25-49% 50-69% >70% 100%
Limitations to Diagnostic Performance of CCTA Parameters % Sensitivity 94 Specificity 83 PPV 48 NPV 99 Se = TP/ (TP + FN) Sp = TN/ (TN + FP) PPV = TP/ (TP + FP) NPV = TN/ (TN + FN) Rates of false positive CCTAs are unnaceptably high. Al-Mallah, M Current cardiovascular Imaging Reports 2016
CCTA and FFR do not correlate well CCTA correlates favorably with angiographic estimate of coronary stenosis but unreliably estimates hemodynamic significance of lesions as determined by FFR FFR 75% false positives The anatomical assessment of the hemodynamic significance of coronary stenoses determined by visual CTCA, CCA, or QCT or QCA does not correlate well with the functional assessment of FFR. 1 1. Meijboom et al. J Am CollCardiol 2008;52:636 43
CCTA and stress testing do not correlate well Source: Schuijf JACC 2006
Assessment of Physiology by CT Angiography FFR CT CT Perfusion Transluminal Gradient
LAD (Equivocal CCTA, Positive cffr) P Coronary P Aorta 0.70 0.74 True Positive
LAD (Positive CCTA, Positive cffr) 0.79 P Coronary P Aorta 0.78 0.78 0.57 0.58 0.58 True Positive
FFR CT CLINICAL DATA
NXT: Per-Patient Diagnostic Performance vs. CT CT (>50%) FFR CT ( 0.80) *p<0.001 * * * % Nørgaard et al, JACC 2014: epub ahead of print; DOI: 10.1016/j.jacc.2013. 11.043
FFR CT reclassification FFR CT reclassified 68% of CT false positives as true negatives Nørgaard et al, JACC 2014: epub ahead of print; DOI: 10.1016/j.jacc.2013. 11.043
Diagnostic performance of diagnostic tests for functionallyimportant (FFR 0.80) coronary disease
FFRCT Clinical Utility. The PLATFORM Trial Douglas P, et al. EHJ 2015
FFRCT Clinical Utility. The FFRCT RIPCORD Trial Curzen N et al. JACC Imag 32016
CT vs Point of Care CT FFR
Diagnostic Accuracy of Point of Care CT FFR 100.0% CCTA vs CT FFR 90.0% 87.3% 82.5% 85.7% 80.0% 70.0% 60.0% 59.3% 62.5% 60.7% 71.5% 50.0% 40.0% 44.8% 47.9% 30.0% 20.0% 21.0% 10.0% 0.0% Sensitivity Specificity PPV NPV Accuracy CCTA CCTA and CT FFR
Summary of diagnostic accuracy of FFR CT on a per-patient and per-vessel basis using invasive FFR as Gold Standard: Point of Number of Per-patient Per-vessel Care Patients Vessels Sensitivity Specificity Sensitivity Specificity DISCOVER-FLOW study [21] DEFACTO study * [22] No 103 159 92% 82% 88% 82% No 252 615 90% 54% 80% 61% Yoon et al.[55] No 65 82 - - 81% 94% NXT Trial $ [56] No 251 484 86% 79% 84% 86% Al-Mallah, M Current cardiovascular Imaging Reports 2016
Summary of diagnostic accuracy of FFR CT on a per-patient and per-vessel basis using invasive FFR as Gold Standard: Point of Number of Per-patient Per-vessel Care Patients Vessels Sensitivity Specificity Sensitivity Specificity DISCOVER-FLOW study [21] DEFACTO study * [22] No 103 159 92% 82% 88% 82% No 252 615 90% 54% 80% 61% Yoon et al.[55] No 65 82 - - 81% 94% NXT Trial $ [56] No 251 484 86% 79% 84% 86% Renker et al.[30] Yes 53 67 94% 84% 85% 85% Coenen et al.[27] Yes 106 189 - - 88% 65% Kruk et al.[29] Yes 90 96 76% 71% 76% 72% Al-Mallah, M Current cardiovascular Imaging Reports 2016
Challenges for FFR CT : Low Quality Studies Cost in other regions Target Population Accuracy in Routine Clinical Practice Workflow of FFR CT Patients with Stents and CABG Al-Mallah, M Current cardiovascular Imaging Reports 2016
CT Perfusion
Scout Images Test Bolus Stress Perfusion (Retrospective) ~ 5 Minutes Rest Scan (Prospective) ~ 7 Minutes Delayed Enhancement (Prospective) Adenosine Contrast Contrast Start ~ 20 Minutes End Blankstein et al, JACC 2009
(A) CT Perfusion (stress) (B) Coronary CT Angiography Stress (C) SPECT MPI (D) Invasive Angiography Rest Blankstein et al, JACC 2009
Example of false positive CT perfusion Stress Stress Rest Rest Blankstein et al, JACC 2009
Average Dose (msv) Radiation Exposure of Stress Cardiac CT vs. SPECT MPI p = NS 14.0 12.0 10.9 12.2 12.0 10.0 8.0 8.9 8.7 6.0 4.0 3.4 2.0 2.1 1.3 0.0 CT Stess Perfusion CT Rest Perfusion CT Delayed Enhancement CT Stress & Rest Perfusion CT Total SPECT Rest SPECT Stress SPECT Total Blankstein et al, JACC 2009
Conclusions FFR CT demonstrated improved accuracy over CT for diagnosis of patients and vessels with ischemia FFR CT superior to CT for intermediate stenoses CT Perfusion appears to be a promising tool in the evaluation of myocardial ischemia More studies are needed to identify its clinical role