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Cardiac CT Shiva Roy FRACP 2008. Why change current practise? Poor at predicting cardiac events –50% of first cardiac events are MI. –50% events occur.

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Presentation on theme: "Cardiac CT Shiva Roy FRACP 2008. Why change current practise? Poor at predicting cardiac events –50% of first cardiac events are MI. –50% events occur."— Presentation transcript:

1 Cardiac CT Shiva Roy FRACP 2008

2 Why change current practise? Poor at predicting cardiac events –50% of first cardiac events are MI. –50% events occur in low to mod risk patients –>50% patients with MI average lipids Functional testing inaccurate So Im going to live? Expensive business! –Hospital admission / angio $ –Perfusion scan $1000 –Cardiologist / stress echo $500

3 Lipid Management Frequently uncertain who to treat NCEP supports statins in high risk (>20% 10 yr) Moderate risk (10-20% 10yr) group challenging –Akosah et al: Young pts mean age 50 presenting MI 70% in lower risk category and statin ineligible Early plaque detection / lipid lowering therapy

4 Coronary Calcification Misguided bias against technique Proven robust technique in identifying at risk population Coronary Calcium Score >100 or >75 th pecentile identifies a CAD equivalent

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6 New Guidelines From AHA

7 AHA – Circulation 2005 Given the evolving literature since the last ACC/AHA Expert Consensus statement (2000), current data indicate that CAD risk stratification is possible with CAC measures. Specifically, low CAC scores are associated with a low adverse event risk, and high CAC scores are associated with a worse event-free survival. This recommendation to measure atherosclerosis burden, in clinically selected intermediate–CAD risk patients (eg, those with a 10% to 20% Framingham 10-year risk estimate) to refine clinical risk prediction and to select patients for altered targets for lipid-lowering therapies.

8 Original Article Coronary Calcium as a Predictor of Coronary Events in Four Racial or Ethnic Groups Robert Detrano, M.D., Ph.D., Alan D. Guerci, M.D., J. Jeffrey Carr, M.D., M.S.C.E., Diane E. Bild, M.D., M.P.H., Gregory Burke, M.D., Ph.D., Aaron R. Folsom, M.D., Kiang Liu, Ph.D., Steven Shea, M.D., Moyses Szklo, M.D., Dr.P.H., David A. Bluemke, M.D., Ph.D., Daniel H. O'Leary, M.D., Russell Tracy, Ph.D., Karol Watson, M.D., Ph.D., Nathan D. Wong, Ph.D., and Richard A. Kronmal, Ph.D. N Engl J Med Volume 358(13): March 27, 2008

9 Conclusion The coronary calcium score is a strong predictor of incident coronary heart disease and provides predictive information beyond that provided by standard risk factors in four major racial and ethnic groups in the United States. No major differences among racial and ethnic groups in the predictive value of calcium scores were detected

10 Introduction to Coronary CTA Imaging technique accounting for cardiac motion through ECG gating –Early 1980s conventional CT –1987 EBCT –1999 Multi Detector CT Accelerated progression in imaging capability over past decade will continue into forseeable future Diagnostic capability has at times preceded the critical evaluation of clinical application

11 Coronary Motion

12 Technology Cardiac motion – Translational, Rotational and Accordian-type movements Selective coronary angiography gold standard –Whole heart covered, real time imaging –Temporal resolution of 10msec –Spatial resolution 100um –But Lumen only Limited angles No cross sectional reconstruction

13 Technology 64 slice CT pivotal technology Spatial resolution 0.35 mm – isotropic Slice, dice, any angle, cross sectional analysis Temporal resolution msec Detector array 4 cm wide Infinite Grey scale, image vessel wall, characterise plaque Can Do –Sensitivity and Specificity ~95% c.f. invasive angiography, ~5% segments unevaluable

14 Helical Scanning Helical scanning involves continuous x-ray exposure and table movement to acquire the most image data in the shortest time.

15 Snapshot Pulse is most dose efficient Z location Time At Z location, waiting for desired heart phase NO XRAYS

16 METHODS - CTA mm slices Single Breath-hold Imaging 80 cc Non-ionic (IODINATED) contrast Aggressive B blockade

17 Normal Study

18 Accuracy of Noninvasive CT Angiography: Trial exclusions Technically inadequate scans not included in analysis Patient exclusion criteria –Rapid heart rates –Irregular heart beat/arrhythmias –Renal dysfunction –Contrast Allergies –Beta-blocker intolerant Obesity limits interpretation

19 Min J. Radiological Society of North America 2007; November 25-30, 2007; Chicago, IL. Diagnostic accuracy of CTA AnalysisSensitivity (%) Specificity (%) PPV (%) NPV (%) Stenoses > 50%, per patient Stenoses > 50%, per vessel Stenoses > 70%, per patient Stenoses > 70%, per vessel PPV=positive predictive value NPV=negative predictive value

20 Radiation Dose with CT EBCT – calcium scan – 0.7 mSv MSCT – Calcium scan – 1.2 mSv MSCT – Angiogram – 9-18 mSv Dose Modulation – up to 47% savings Coronary Angiogram – mSv Nuclear Imaging – 6-15 mSv

21 43 year old man commenced a new exercise program Left side chest discomfort on exertion Cholesterol 6.0, LDL 3.6, HDL 1.3 No smoking, diabetes, HT or family history of IHD BMI 26 kg/m2 Medications – nil Resting ECG – normal What next ? CIA Mar 08

22 Objectively negative stress echocardiogram – 13 minutes However, vague left sided chest pain at peak exercise Is my heart OK ? CIA Mar 08

23 LAD

24 Case 2 48 yr old man Consistent exertional bilateral arm tightness like the compression of a blood pressure cuff Chol 7.8, LDL 5.1. Father and brother IHD in their 50s. On no medical therapy at time of presentation Negative Stress Echo after 12 minutes of Bruce protocol. No symptoms with stress test Worrying symptoms and CV risk factors, but negative functional test

25 Volume rendered image of Coronary CT Severe LAD and Diagonal branch stenosis

26 Outcome This patient had a concerning history and risk factor profile. He declined the offer of an invasive angiogram given his negative stress test. He agreed to have a CT coronary angiogram which detected severe proximal LAD disease which required revascularisation.

27 37 yr old pastry chef- referred Aug 05 Sudden death of 40 yr old first cousin Background SVT 3 episodes over last 15 years Ex smoker 1year (since age 20) FH of IHD father CABG at 63 Chol 5.4, LDL 3.4, HDL 1.2, TG 1.9 Chol/HDL ratio 4.5 Overweight at 100kg (BMI 33) Case 3

28 SR 86bpm BP 130/90 ECG ECHO Exercise stress test (echo assisted) 11.5 mins of Bruce protocol Normal haemodynamic response Limited by fatigue no CP No ECG or ECHO evidence of ischaemia

29 Lifestyle changes Stay off cigarettes weight loss dietary and exercise advice Further investigation ? (asymptomatic) novel risk factors Hs CRP, Lp(a), homocysteine GTT ambulatory BP monitor ? Sleep study Pharmacological intervention ?

30 Assessment of 5-10 year risk of coronary event Framingham risk score (10 year risk) NZ risk calculator ( 5 year risk) Pharmacological intervention if risk >2%/yr or 20%/10yrs

31 (assume still smoking) (12%/10yrs)

32 Aspirin…recommended when 10yr risk> 10% per 1000 people treated per year prevent 14 AMI at expense of 4 bleeds Statins.. NHF Risk > 20%/10yrs PBS subsidy ineligible

33 Known CHD, PVD or CVD AAA DM CRF Familial Hyperlipidaemia Absolute risk of >2%/yr

34 Increased absolute risk: LDL > 4.0 or Chol > any 2 or more risk factors HDL< 1.0 FH HT Overweight Smoking IGT Microalbuminuria Age> 45

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36 Referred by GP June 2006 Calcium score 360

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38 Coronary Calcification (CAS) Non-invasive Coronary Angiography Aortic Assessment (anuerysm, dissection) Pulmonary Embolism Pericardial disease Congenital heart disease Cardiac thrombi & tumor Quantification cardiac anatomy & volumes, global & regional function Venous Anatomy – Pulmonary and Coronary veins pre-procedure CT – Cardiac Applications

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40 Open Bypass Grafts

41 Coronary aneurysms

42 Apical Thrombus and Infarction

43 Left Atrial Appendage Thrombus

44 ASD

45 Patent Ductus Arteriosus Ao PA

46 Pericardial Thickening

47 Pulmonary Veins

48 Placement of LV Lead

49 Appropriateness criteria for Cardiac CT CCT/CMR writing group JACC 2006:48(7):1-21 Appropriate/uncertain/inappropriate indications for cardiac CT based on symptom status/ECG/biomarkers/ability to exercise/pre-test risk profile Pre PV isolation/BiV pacing Anomalous coronary anatomy/pericardial disease/cardiac masses/cardiomyopathy/non- coronary cardiac surgery Possible Pulmonary embolus/aortic dissection

50 Triple Rule In

51 In the ER? High negative predictive value, therefore CT may help avoid unnecessary hospital admissions, however… Patient preparation 24hr scan workup usually not logistically feasible Scanner availability Coronary physiology and other investiagations(ECG and biomarkers) well validated for prognosis All coronary segments may not be visible Apparent non-flow limiting lesion potentially unstable Triple rule out –high radiation and contrast doses High volume centre usually provides high quality service

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53 Potential use of CT Coronary Angiography Intermediate Risk Low risk High Risk No Investigation or Functional testing (Stress ECG/Echo/Nuclear) MSCT Suspicious pain/Neg FT Atypical pain/Pos FT Poorly compliant with Lifestyle or med Rx angina, ECG +ve Troponin +ve, functional test +ve Mild atheromaModerate atheroma Severe atheroma Functional test No ischaemia Ischaemia Medical therapy Angio / revascularisation Medical therapy Risk as calculated by conventional vascular risk factors: Low 20% Asymptomatic?/atypical pain


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