CTMRI在評價缺血性心臟病中作用

1、CTMRI在評價缺血性心臟病中作用Diagnosis Of Subclinical Atherosclerosis: The Asymptomatic PatientSubclinical Atherosclerosis And Early Abnormalities Of Structure And Function Subclinical Atherosclerosis (Higher Risk) Functional Abnormalities Structural AbnormalitiesCoronary Artery Calcium Score Is Predictive Of D

2、eath And MIGreenland, P. et al. ACC/AHA Expert Consensus, JACC, 2007 Higher CACS, higher event rates*f/u 3-5 yearsCoronary Artery Calcium Score ImprovesRisk Stratification Over Framingham Risk ScoreCACS 400 = CHD Equivalent (10 year risk 20%)Greenland P, ACC/AHA Expert Consensus, JACC, 2007 Can We D

3、o Better Than CACS? CT exposes patients to radiation Calcification appears relatively late Very late in women and young tend not to have Ca ? Significance of progression Progression more related to baseline CACS Ca related to healed not vulnerable plaque Unclear if statin improves Ca 10% inter-scan

4、variabilityFunctional defects appear years earlier and improvement can occur as early as 2 weeks post RxVascular Function TestingAssessment of arterial response to chemical or physical stimuli known to cause vasoreactivityEndothelial-dependent: Ach, shear stress, cold pressorEndothelial-independent:

5、 NTG, adenosineMeasurement in diameter, CSA, velocity, or resistanceNormal: DilationAbnormal: Impaired Dilation, No Response, ConstrictionCoronary and peripheral arteriesXRA, MRI, U/S (brachial artery) Impaired Vasoreactivity To Endothelial Dependent And Independent Stimuli Is Associated With CV Eve

6、ntsSchachinger V, Circulation 2000 147 pts referred for XRA for chest pain or single vessel PCI 43% had no angiographic evidence of CAD All significant after multivariate analysis (RF, atherosclerosis on XRA)More CVD Events With Impaired Vasodilation during 7 Year Follow-UpSchachinger, Circulation 2

7、000MRI Assessment Of Vascular FunctionAcquire long and short axis images at baseline Choose most linear segment of artery for short axis images to yield most circular cross sectionGive stimulus then reacquire high resolution images at “peak” effect of stimulusMeasure % change in CSA in response to t

8、he stimulus CSA Post-Stimulus CSA BL - CSA BL% Vasodilation = Pre NitroPost NitroFeasibility Study Of MRI AssessmentTo determine if MRI can quantify changes in epicardial size in response to NTG12 pts undergoing XRA (6 CAD, 6 Tx) and 20 healthy controls0.4 mg sl NTG with minimal systemic effectsExce

9、llent correlation of lumen area w/ XRA: r = 0.98Terashima, JACC, 2005TxIntra-observer variability 3 2% (r=0.99)Inter-observer variability 5 5% (r=0.96)NlMRI NTG Vasodilation ImpairedIn DM And ESRD Pre Nitro Post NitroNlESRD25.6%17.8%19.8%14.8% 15%15%ESRD20%80%DM62%38%Controls94%6%Nguyen P, JCMR 2008

10、MRI Vasodilation Decreased In Patients With High CAC (ADVANCE)Terashima M, JACC Img, 2008Association significant after adjustment for RFMRI NTG Decreased In Physically Inactive 18.9% (5.7%, 33.4%) for 35 vs. 27.6% (12.6%, 38.7%) for 35 (p=0.03) Positive correlation even after multivariate analysis D

11、ecreased vasodilation in less active men and women but did not reach significance in women % vasodilation related to intensityNguyen, P, in prep. AJPDiagnosis Of CAD And Anatomical Imaging: The Symptomatic PatientCT Coronary Angiography Axial images contain true data CT images can be reformatted in

12、multiple 2D views and with 3D reconstructionHigh Grade LAD LesionMhlenbruc G, Eur Radio 2006Sensitivity And Specificity: 64 MDCTn% Unevaluable SegmentsSensitivitySpecificityNPVLeschka67-949799Raff7012869598Leber59-73-889799Mollet522999599Ropers824959399Fine666959695Schujf*39649295-Stein*670100100- F

13、rom 4 to 64 MDCT Decrease in number of unevaluable segments Improved sensitivity and specificity Similar NPVStep Artifacts Beta blockers given to reduce heart rate Should not be performed in patients with significant arrhythmias Improved temporal resolution with dual source systemBlooming Artifact I

14、mpairs Evaluation Of Calcified Segments 29 patients with 65 lesions, 45% complex lesions 25% of lesions non-evaluable (15% motion/image noise, 10% severe Ca) Overestimation and underestimation of plaque, especially on a per segment analysisSheth J, AJC, 2006High Negative Predictive Value With 64 MDC

15、T For In-Stent Restenosis XRA vs. CTA (64 slice MDCT) in 81 patients Sensitivity 91%, Specificity 93% PPV 77%, NPV 98%, Predictive Accuracy 93% 12% segments not assessable Grade 1: none Grade 2: mild w/ 75% stenosis occlusionLewis B, JACC 2007In-Stent RestenosisNeointimal hyperplasia without signifi

16、cant stenosis Complete stent occlusionOncel D, Am. J. Roentgenol 2008Dx Of High Grade Lesions: CT Angiography XRA remains the gold standard Indicated only if intermediate pretest probability and if ACS: enzymes and ECG must be negative Chest pain syndrome/Chronic ischemic dz (ECG un- interpretable,

17、cannot exercise or equivocal stress test) Evaluation of new onset heart failure Not recommended for in stent restenosisRadiation dose is 5 to 13 mSv (1 yr background radiation) and 100 cc of contrast requiredMR Coronary Angiography Promising But Complex Acquisition With Lower Spatial ResolutionDiagn

18、osis And Risk Assessment In The Symptomatic Patient : Functional Imaging by MRIMRI Assessment Of Resting Function Is “Gold Standard”MRI Stress Perfusion: Areas With Significant Stenosis Enhance Less And More SlowlyStressRest Sensitivity, Specificity And AccuracynSensitivitySpecificityAccuracySchwitt

19、er (2001)488785-Nagel (2003)84889089Wolf (2004)99937585MRI Perfusion Alternative To Stress Echo On A Case by Case BasisComparable sensitivity and specificity for stress echo and MRI perfusionDue to cost, versatility and patient comfort, stress echo is preferred If image quality impaired in echo, MRI

20、 perfusion is a good alternativeAbnormal Microvascular Function In Syndrome XPainting, NEJM, 2002Guiding Revascularization Post MI And Prognosis: Myocardial Viability MRI Assessment Of Viability Infarct (Gd)NormalImaging Sequence (SE, FSE, GRE)Normal myocardium signal is null (dark)Infarct has parti

21、ally recovered (bright)TI Gd is injected. Wait 10 - 15min. Gd accumulates in infarcted tissue A 180 RF pulse inverts all the spins. Tissues return to nl at different rates. At time TI, imaging sequence begins. 180Inversion Pulse Low Chance Of Recovery If Delayed Enhancement 75%Kim, R et al, NEJM 200

22、0 No hyperenhancement =78% segments improved Only 1 out of 58 segments improved if hyperenhancement 75% Less certain outcome for segments between 25-50% Same relationship in segments with most dysfunction Recent studies have also shown increased areas of DE indicates worse prognosisDelayed Enhanceme

23、nt Compared To Available TechniquesComparable sensitivity to DBA echo but slightly lower specificity MRI preferred in patients with severe baseline hypokinesisComparable sensitivity and specificity to PET and SPECTAbility to detect small, subendocardial infarcts better than PET or SPECTMRI Detects Small Infarcts Better Than SPECTIbrahim T, JACC 2007Microvascular Obstruction After AMI Is Marker Of Poor