Role of cardiac CT in coronary artery diseases Dr. Ahmed Refaey MBBCh, MS, FRCR

Format of the lecture Normal anatomy of coronary arteries MSCT coronary angio Clinical application of CTA Illustrated cases

Coronary arteries anatomy

LCA “ left coronary artery “ Normally arises from the left sinus of Valsalva Courses posterior to the right ventricular outflow tract (RVOT), and bifurcates into the left anterior descending (LAD), and the left circumflex (LCX) branches.

Right Coronary Artery (RCA) Normally arises from the right coronary sinus (CS) and courses in the right AV groove toward the crux of the heart

Of CAD Diagnosis Clinical Presentation ECG Echocardiography Stress Test Thallium Study Coronary cathetrization Multislice Coronary CT Scan

Methods of imaging of coronary arteries

Coronary catheterization Multislice cardiac CT

Coronary catheterization

CORONARY CATHETERIZATION Advantages High resolution Option for intervention Disadvantages X-ray exposure Hospitalization Invasive complications

Figure 21.8d Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Multislice CT coronary angiography

What is Coronary CTA? Coronary CTA is a non-invasive minimal risk procedure to directly visualize the coronary arteries through administration of IV contrast It allows visualization of the coronary arteries similar to a cardiac catheterization with additional information about the WALL of the artery and composition of plaque (calcified or non-calcified)

Clinical application of CTA Diagnosis of CAD * intermediate liklihood of disease * after equivocal/discordant stress imaging * coronary anomalies * before vascular surgury * nonischemic vs ischemic cardiomyopathy * acute chest pain * bypass graft patency / location

Patient Preparation No Caffeine for 12 hours prior to exam Everyone gets Beta-Blockers (Verapamil can be substituted)

Goal Heart Rate < 60 bpm makes us happy

Contraindications Atrial Fibrillation Tachycardia Beta Blockade Contraindication Heart Block Renal Failure (Creat>1.5) Contrast Allergy

The Examination

Computed Tomography (CT) X-ray tube and detector rotate around the patient, transversal slices are constructed following each rotation by computer

continuous scanning instead separated slices Spiral multislice CT continuous scanning instead separated slices

Entire heart imaged in 5-15 seconds CT images that are used come from mid to end diastole due to relative motion free period

CT Angiography

Timing

CT-Angio Advantage Excellent for Coronary vessel, bypass vessels, LV wall thickness and function, cardiac anatomy and pericardium assessment

Coronary Vessel Analysis

Maximum Intensity Projection Soft Plaque in Proximal LAD

Curved Planar Image

3-D Volume Rendered Image

Effective Radiation Doses for Various Tests Bone Density 0.01 mSv CXR: 0.02 mSv Mammogram: 0.7 mSv CT of the head: 2 mSv CT colonoscopy 5 mSv CT of the abdomen: 10 mSv Stress Gated Myocardial Perfusion Scan SPECT: 10-11 mSv CT chest: 13 mSv MSCT angiogram: 15 mSv Coronary angiography: 30mSv CT chest/abd/pelvis: 35 mSv Dose allowed for radiological personnel: 20 mSv/year

CLINICAL APPLICATION OF CARDIAC CT ANGIO Examine plaque components Evaluate coronary vessels Evaluate stent patency Assess cardiac function

Examine plaque components

Plaque Characterization Calcified vs. Soft Plaque composition rather than the degree of lumen stenosis determines the risk of plaque rupture. Vulnerable or “high-risk” plaques have thin fibrous cap with extracellular lipid core. Not visible by catheterization, but is being explored with CT angio. Plaques initially grow extrinsic and bulge adventitia, then grow into the lumen resulting in stenosis

Coronary Artery Plaque: approximate amounts of lipid rich, fibrotic and calcified plaque Fibrotic & Calcified 20% 66% The “Tip of the Atherosclerotic Iceberg” Fibrotic 80% 33% Lipid Rich

What does coronary calcification mean? Calcium score correlates extremely well with coronary event risk If multi-vessel CAC, then risk increases Zero calcification suggests a very low probability of obstructive disease Curved MPR reformatted image of Right Coronary 17

Calcium Scoring “ Agatston score”

The Calcium Scale 1–99 mild 100–400 moderate >400 severe The calcium scale is a linear scale with 4 calcium score categories: 0 none 1–99 mild 100–400 moderate >400 severe *Calcium score correlates directly with risk of events and likelihood of obstructive CAD*

Agatston-90

Examples of Coronary Artery Scans NO CALCIFICATION MODERATE CALCIFICATION SIGNIFICANT CALCIFICATION Images courtesy of HeartScan San Frasco 15

Coronary Artery Calcium Scans Task: Detect Calcium in Coronary Artery 130 kVp 625 mA .1 sec 3 mm

Coronary Artery Calcium Scans

Coronary Artery Calcium Scans

Coronary Artery Calcium Scans

Coronary Artery Calcium Scans

Coronary Artery Calcium Scans

Coronary Artery Calcium Scans

Coronary Artery Calcium Scans

Coronary Artery Calcium Scans

Coronary Artery Calcium Scans

Calcification in LAD 13

Calcification in RCA 15

EVALUATING CORONARY VESSELS

It can look even better than a conventional angiogram

Left Main Coronary Artery

Left Main, LAD, & Circumflex Obtuse Marginal

Diagonal Branch off LAD

Right Coronary Artery Acute Marginal Right Coronary Artery Sinoatrial

Right Coronary Artery

Evaluate stent patency

LAD Stent from Top to Bottom (1 mm)

LAD Stent from Front to Back (1 mm)

Cardiac function Recent studies show good correlation between function parameters derived from MDCT and levocardiography. DETERMINING EJECTION FRACTION

FUTURE OF CARDIAC CT One-stop shopping— ( cardiac function, coronary artery evaluation, plaque analysis, calcium quantification.) Non-invasive

Illustrated cases

High-resolution Imaging 1 LM LAD 1 2 2 3 4 3 RCA LCx LM 4 DSCT 74

Significant stenosis of the left anterior descending artery

Soft Plaque Visualization

stent in LAD,LCx & RCA I

Aortic Coarctation Visualized Fröhlich, G et al. Circulation. 2005;112:e81.

Pericardial Calcification Multi-Slice CT Scanning Superior to MRI Hoffmann et al. Circulation 108 (7): 48e Figure IG1

Mild CAD, and…

Pulmonary Emboli

Teaching Points

Cardiac Cath: Lumen only-no wall information. Evaluate stenosis Cardiac Cath: Lumen only-no wall information. Evaluate stenosis. Cannot characterize plaque. Better delineates small vessels What is needed is a non-invasive, minimal-risk, outpatient procedure to detect early signs of CAD

Coronary CTA- Strengths Noninvasive. Can measure HU of plaques and characterize them as fatty, atheroma, fibrosis, calcium. Can evaluate status of bypass grafts. Can determine stent patency. Evaluates portions of mediastinum and lungs.

Coronary CTA- Weaknesses Cannot accurately measure stenosis with heavy, calcified plaque burden. Occlusions can be missed by brisk collateral flow.

What do I do with this information? Reports will be classified in one of four categories of severity: Normal Mild Plaque with No stenosis Moderate Plaque with mild/Mod stenosis Severe Plaque and stenosis: Cardiac Cath

Thank you