ANATOMY AND IMAGING OF CORONARY ARTERY DISEASE WITH SPECIAL REFERANCE TO CT CORONARY ANGIOGRAPHY

Presented by– SARBESH TIWARI PGT

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Coronary artery

Coronary artery is a vasa vasorum that supplies the heart.

Coronary comes from  the latin ”Coronarius” 

Meaning “Crown”.

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Coronary artery• The coronary artery arises

just superior to the aortic valve and supply the heart

• The aortic valve has three cusps –

#left coronary (LC), #right coronary (RC) #posterior non-coronary

(NC) cusps.3

Right coronary artery

• Originates from right coronary sinus of Valsalva

• Courses through the right AV groove between the right atrium and right ventricle to the inferior part of the septum

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Branches of RCA

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Right coronary artery

Conus artery

Sinu nodal arterySinu nodal artery

Marginal arteryMarginal artery

Post. Descending IV arteryPost. Descending IV artery

AVAV nodalnodal artery-artery-

Conus branch

SINU NODAL BRANCH

AV Nodal BranchAV Nodal Branch

• Conus branch – 1st branch supplies the RVOT

• Sinus node artery – 2nd branch - SA node.(in 40% they originate from LCA)

• Acute marginal arteries-Arise at acute angle and runs along the margin of the right ventricle above the diaphragm. 

• Branch to AV node

• Posterior descending artery : Supply lower part of the ventricular septum & adjacent ventricular walls.

Arises from RCA in 85% of case.

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Right coronary anatomy

AO

LA

RCA

CONUS BR

RCA

SAN

1 2

3 4RCA

AM

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RCA

AMAM

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Area of distributionRT CORONARY ARTERY----

1)Right atrium

2)Ventricles

i) greater part of rt. Ventricle except the area adjoining the anterior IV groove.

ii) a small part of the lt ventricle adjoining posterior IV groove.

3)Posterior part of the IV septum

4)Whole of the conducting system of the heart, except part of the left br of AV bundle

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Left coronary artery

• Arises from left coronary cusps

• Travels between RVOT anteriorly and left atrium posteriorly.

• Almost immediately bifurcate into left anterior descending and left circumflex artery.

• Length – 10-15mm

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LEFT CORONARY ARTERY 12

LT CORONARY ARTERY

1) Left atrium.

2) Ventricles

i) Greater part of the left ventricle, except the area adjoining the posterior IV groove.

ii) A small part of the right ventricle adjoining the anterior IV groove.

3) Anterior part of the IV septum.

4) A part of the left br. Of the AV bundle.

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DOMINANCE• Determined by the arrangement that which artery

reaches the crux & supply posterior descending artery

• The right coronary artery is dominant in 85% cases.

• 8% cases - - circumflex br of the left coronary artery

• 7% both rt & lt coronary artery supply posterior IVseptum & inferior surface of the left ventricle-here it is balanced dominance.

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ATHEROSCLEROSIS

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 Fatty streaks composed of lipid-laden macrophages (foam cells)

Plaque :- Soft necrotic core of lipid with surrounding chronic inflammatory cells covered by fibrous cap.

Fatty streaky progress to plaque

Progressively enlarge causing critical stenosis

Progressively enlarge causing critical stenosis

Ulcerates or ruptures leading to thrombosis and critical ischemia

Ulcerates or ruptures leading to thrombosis and critical ischemia

Pressure atrophy of the media causing

aneurysmal dilatation

Pressure atrophy of the media causing

aneurysmal dilatation

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Coronary pathology in acute coronary syndrome. The evolution of coronary lesions follows a progression from (1) initial plaque formation, (2) plaque growth, (3) plaque vulnerability and rupture, and (4) thrombosis.

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IMAGING MODALITIES

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Coronary Imaging Technique• INVASIVE PROCEDURE:

1. CATHETER CORONARY ANGIOGRAPHY 2. INVASIVE ULTRASOUND

• NON INVASIVE PROCEDURE:

1. CHEST X RAY 2. ECHOCARDIOGRAPHY 3. COMPUTED TOMOGRAPHY ELECTRON BEAM CT (EBCT) MULTIDETECTOR CT (MDCT) 4. MAGNETIC RESONANCE IMAGING 5. NUCLEAR IMAGING.

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CATHETER ANGIOGRAPHY

• A minimally invasive procedure to access coronary circulation and blood filled chambers of the heart using a catheter.

• The technique was first performed by Dr. Mason Sones at the Cleveland Clinic in 1958

• The major epicardial vessels and their 2nd & 3rd order branches can be visualized using coronary angiography.

• It is performed for both diagnostic and interventional (treatment) purposes.

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INDICATION

1. Diagnosis of CAD in clinically suspected pts.

2. Providing peri-interventional information for percutaneous coronary intervention

3. Coronary anomalies

4. To exclude stenoses before non-coronary cardiac surgery (valve surgery after 40 yrs of age)

5. Determine patency of coronary artery bypass grafts

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CONTRAINDICATION Coagulopathy Decompensate congestive heart failure Uncontrolled Hypertension CVA GI Hemorrhage Pregnancy Inability for patient cooperation Active infection Renal Failure Contrast medium allergy

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PROCEDURE PROPER

• PATIENT PREPARATION:

1. Arrives at Cath. Lab at morning with at least 6

hrs. fast

2. Allowed to take all medications as advised by

physician including aspirin except oral hypoglycemic

agents

3.Intravenous access is secured.

4. Sedation with benzodiazipine is recommended.

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• Vascular Access: Seldinger Technique is used. Transfemoral route is MC (transradial & transbranchial routes can also be used).

• Catheter used- MC is Judkins catheter.

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• 3 different types are for Rt & Lt coronary artery & Lt ventricle.(Lt ventriculography is followed usually after cor. angio)

Catherization: Seldinger Technique

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• Contrast media-Low osmolarity, Non-ionic

• Dose-3-10 ml;320-370 mg of iodine/mg, using a hand-held syringe filled from a reservoir.

• Left coronary artery is filled with 6-8 ml, right coronary artery is filled with 3-5 ml usually

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Angiographic projection-

• The heart is oriented obliquely in the thoracic cavity, the coronary circulation is generally visualized in the RAO & LAO projection to furnish true PA & LAT views of the heart. using both cranial & caudal angulations.

• For LCA branches, views - -AP ,RAO, LAO with cranial tilt

• For RCA branches, views reqd. are -AP,RAO ,LAO ĉ or ĉout cranial

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Angiographic view of LCAAngiographic view of LCA

Angiographic view of RCAAngiographic view of RCA 30

Pitfalls of coronary angiography

1. Inadequate vessel opacification- May give impression of ostial stenoses, missing side branches or thrombus.

2. Eccentric stenosis- Coronary atherosclerosis often leads to eccentric or slit–like narrowing than central narrowing; so if the long axis of the vessel is projected, the vessel may appear to have a normal or near normal caliber.

3. Superimposition of branches

4. Foreshortening of the stenotic segment due to projectional defect

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Rotational CA

• X-ray system rotates around the patient during the acquisition of a single run

• Significant reduction in both contrast agent usage and radiation dose of up to 30%, without compromising image quality

• Contrast medium is injected automatically (3 mL /s for the LCA and 2 mL/s for the RCA) range 12-18 cc

• After this preload, rotation of the C-arm was started automatically and X-rays taken

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Complication‐Overall mortality is about 0.2%. # Vascular‐hematoma, false aneurysm, AVF

# Cardiacarrythmia MI cardiac‐arrythmia, MI

#contrastmedia induced‐heart failure, ECG changes,,allergic reaction 

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Tight stenosis noted involving the mid segment of right coronary artery. Distal branches are normal.

A partially obstructive narrowing noted in the proximal segment of

the LAD

CORONARY CT ANGIOGRAPHY (CCTA)

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AVAILABLE TECHNOLOGY• Currently, two competing CT technologies are used- 1. Electron-beam CT and 2. Mechanical multi–detector row CT

Electron beam CT :

# Used specifically for cardiac imaging d/t high temporal resolution

# Uses a rapidly rotating electron beam, which is reflected onto a stationary tungsten target

# Imaging done in sequential mode, where single transverse sections are sequentially acquired.

# However, due to higher cost and limited availability, MDCT is most commonly used.

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CT CORONARY ANGIOGRAPHY

• Coronary computed tomography angiography (CCTA) is an effective noninvasive method to image the coronary arteries

• MDCT has multiple detector rows are placed opposite the x-ray tube which shortens the examination time and improves the temporal resolution

• The new generation 64 detector MDCT system has allowed higher isotropic resolution, with visual clarity of up to fifth- order coronary arterial branches.

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Which ? MDCT is optimum

• 4/8-slice –For detection CAD sensitivity: 86% and ruled out in 64 of 80 patients (specificity: 81%).

• 16 slice MDCT -sensitivity: 96% ,specificity: 83

• 64 slice CT -sensitivity: 97% ,specificity: 92%

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• High-quality source images are the most important prerequisite for the diagnostic assessment of coronary CTA.

• Image quality depends on:

1. Heart rate – Image quality improves with heart rate less than 65.

2. Proper coronary CTA scan and post processing protocol.

3. The synchronization of raw image data with electrocardiography (ECG) information

4. Breath Holding : 45 sec (4 detector) to 9 sec (64 detector)

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INDICATION• Screening high risk patients

• Evaluation of chest pain

• Post procedural study

Post CABG

Post stent

• Dilated Cardiomyopathy

• Non-cardiac surgery evaluation

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CONTRAINDICATIONS

• Absolute contraindication : 1. Hypersensitivity to iodinated contrast agent 2. Pregnancy Relative contraindication Irregular rhythm Renal insufficiency (sr. creatinine > 1.5 mg/ml) Hyperthyroidism Inability to hold breath for 10 sec History of allergy to other medication Metallic interference (e,g: pacemaker,

defibrillator wires)

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PATIENT PREPARATION

• Avoid caffeine and smoking 12 hours prior to the procedure to avoid cardiac stimulation.

• B- blocker : Oral or I.V B-blocker is used in patient with heart rate greater than 60 bpm

oral 50- 100 mg metaprolol administered 45 min to 1 hr before procedure.

or I.V Metaprolol 5 to 20 mg at the time of procedure

Sublingual Nitrates or Nitroglycerine: given immediately before the procedure to dilated the coronary arteries.

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Patient Positioning and Preparation for Scanning

• Patients are positioned on the CT examination table in the supine position

• ECG leads are attached to obtain an adequate ECG tracing.

• Intravenous access via a large intravenous line (18 gauge cannula) is necessary to ensure easy injection of the viscous contrast agent at a flow rate of 5 mL/s

• Training of patients with repeated breath holds

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ECG gating protocols

• For ECG synchronized scanning of the cardiac region, two different approaches are taken

1. Prospective ECG gating

2. Retrospective ECG gating

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PROSPECTIVE ECG GATING

• Scan acquisition is triggered by the ECG signal at the prospected mid-diastolic phase of the cardiac cycle.

• Between 40% and 80% of the R-R interval

• Benefits: Smaller patient radiation dose

• Limitation: Reconstruction of image in different cardiac phase for functional analysis of ventricle is not feasible

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RETROSPECTIVE ECG GATED SCANNING

Heart region is scanned continuously

Contiguous data of cardiac region are acquired

Patient’s ECG is recorded at the same time

Scan data with least cardiac motions , usually the diastolic phase , are selected later for image reconstructionAdvantage:

•Entire volume is acquired continuously and gapless•Image may be reconstructed with overlap

Disadvantage:• Higher patient radiation exposure 46

Diagram showing effect of ECG dose modulation. In Fig 1- continuous scanning throughout the cardiac cycle with full tube current , resulting in high radiation dose. In Fig 2- ECG dose modulation is turned on and full tube current is applied only during 40-80% of cardiac cycle, where cardiac motion is least. In Fig 3- To further decrease radiation, a single phase of cardiac cycle is selected for scanning during which full tube current is applied.

ECG controlled dose modulation

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Image acquisition and reconstruction

• The acquisition of the dataset for coronary CTA consists of 3 steps :

1. Topogram

2. Contrast medium protocol : to ensure homogeneous contrast enhancement of the entire coronary artery tree

3. Coronary CTA scan

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TOPOGRAM

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• Native coronary arteries # Begin above carina # Tortuous aorta or

prominent upper left heart border – begin scan 1-2cm higher

• Bypass Grafts Veins: top of arch LIMA: above clavicles

SCAN START POSITION

SCAN ENDING POSITION

Image acquisition end 2 cm below the diaphragm

Contrast Medium Protocol

• Optimal coronary artery opacification depends on :

1. The iodine medium concentration – (300-400 mg iodine/ ml is used)

2. The volume and rate of contrast administration

3. Timing of the contrast medium delivery.

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Volume and rate of contrast administration

Using 64 detector MDCT technology:

• 80ml of contrast agent is injected at 6 ml/sec f/b 40ml saline solution at 4ml/sec

Using 16 detector MDCT technology:• 100- 120 ml of contrast agent @ 4 to 5 ml

per sec.

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• Delivery of contrast medium s/b timed to ensure that the scan of cardiac region will occur at the peak of opacification of the coronary tree.

• It can be assessed by two techniques-

1. Automated contrast bolus tracker technique- the ROI is placed on ascending aorta. When ct value of ROI is greater than predetermined threshold of 100- 150 HU, the scan begins.

2. Test bolus scan – here a small bolus of contrast is injected to determine contrast transit time. The time from the start of the injection to the peak contrast enhancement in the ascending aorta determines the scan delay after the initiation of contrast material administration.

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• After contrast administration, CT is obtained in single breath-hold

• Scan volume covers the entire heart from the proximal ascending aorta (approximately 1–2 cm below the carina) to the diaphragmatic surface of the heart

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Scanning protocol

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Post processing protocol• The axial source images obtained are utilized for

multiplanar reconstructions in at least 2 planes

• Commonly used techniques are : Maximum intensity projection (MIP), Volume rendering (VR), Multiplanar reconstruction (MPR) or Curved planar reconstruction (CPR

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Curved multiplanar reconstruction (MPR) image

"Ribbon" multiplanar reconstruction (MPR)

Maximum intensity projection (MIP)3D Volume-rendering 56

RADIATION DOSE• Ranges between 12-16 mSv depending on CT

scanner and type of ECG gating used.

• ECG-controlled dose modulation systems allows reduction of radiation exposure by upto 50%

• Lower the KVP to 100 causes significant dose reduction.

• A prospective gate window of 20% over diastole in patients with HR of 60, can reduce total dose by 80%.

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Coronary artery assessment The best evaluated coronary artery is the LAD

as it runs along the axis of the scan and is not significantly affected by cardiac movements

The LAD is well visualized in 76-96% of cases

The left CX artery may be affected by cardiac motion artifacts and can be assessed in 52-95% of cases

RCA is most affected by cardiac movement

Proximal coronary segments are better visualized than distal ones.

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ADVANTAGES OF MDTC• Non invasive procedure without any hospital stay.

• MDCT CA can precisely identify total occlusion, indicate cause and extent.

• Morphology of the occluded segment and the time the artery was occluded

# In acute obstruction, low density intraluminal defect caused by thrombosis with an increase in luminal area and diameter are seen.

# In chronic cases , the obstruction shows calcified or mixed plaques with the artery lumen with normal or slightly narrowed lumen

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• Predictors of failure to open an occluded artery include

1.occlusion length greater than 15mm 2.Presence of severe calcification in the

compromised segment.

• Vessel distal to the completely obstructed segment is visualized , not possible with catheter angio.

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Calcium scoring

• Coronary calcium screening is intended to detect calcified atherosclerotic plaque burden as a surrogate marker for coronary atherosclerosis.

• Based on the principle that– # Obstructive atherosclerotic

plaques are calcified – so called “Hard Plaque”

# Calcium is not present within the wall of a normal coronary artery

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INDICATION• Women over the age of 55 and men over the

age of 45 should consider the coronary calcium scan, if they have coronary artery disease risk factors: 

---- Family history of heart disease ---- High cholesterol level

(hypercholesteremia) ---- High blood pressure ---- Smoking, Obesity ---- Diabetes ---- High-stress lifestyle

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Minimum requirement for calcium scoring

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HOW THE PROCEDURE IS DONEPreparation:

# No special preparation is necessary

# Avoid caffeine and smoking four hours before the exam.

# Heart rate ＞ 90/min → β- blocker

Protocol :

# No contrast used

# 2.5 mm to 3 mm slice thickness

# Prospective ECG –gated acquisition for calcium scoring.

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• The threshold for calcification is set at an attenuation value of ≥ 130 HU, for an area of > 1mm2

along the course of the coronary arteries.

• For MDCT the threshold value for calcification is 90 HU ( because of high signal to noise ratio )

• Automated measurement of the lesion area in mm2

and maximum CT No. (HU) of each lesions are recorded.

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• Density score of the lesions are determined as

• The total as well as individual coronary artery calcium score is calculated using special software at the workstation

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Methods• Quantitative calcium scores are calculated

according to the method described by Agatston et al .

Calcium score= density score x volume

• CAC scores are typically reported for each major coronary artery (left main, left anterior descending, circumflex, right coronary artery) separately

• The total score is achieved by adding up each of the scores for all the slices

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WHAT DOES THE CALCIUM SCORE REPRESENT

• Detection of any degree of coronary calcium on CT indicates that CAD is present

• It provides a quantitative estimation of plaque burden. Higher the score the larger the plaque burden & higher the subsequent cardiac events.

• Score of zero indicates unlikely chance of CAD, does not eliminate the possibility.

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CALCIUM SCORING GUIDELINESCALCIUM SCORES

IMPLICATION RISK OF CORONARY ARTERY DISEASE

0 No identifiable plaque Very low, less than 5%

1 – 10 Minimal identifiable plaque

Very unlikely, less than 10%

11 – 100 Definite, at least mild atherosclerotic plaque

Mild or minimal coronary narrowing likely

101 - 400 Definite, at least moderate plaque

Mild coronary artery disease highly likely, significant narrowing possible

401 or higher

Extensive atherosclerotic plaque

High likelihood of at least one significant coronary narrowing

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GUIDELINES FOR THE PHYSICIANS IN INTERPRETING A PATIENTS SCORE

Presence of any detectable calcium

Implies presence of CAD

More aggressive BP control, lipid lowering

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GUIDELINES cont….

Patients with high scores (>400)

likelihood of harboring a significant stenosis

Should undergo stress testing to evaluate for inducible ischemia

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GUIDELINES cont…. Patients with intermediate scores

Require further testing based on other factors like age etc.

Score of zero

No need for further imaging tests for

Coronary disease

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Advantages of Coronary calcium scoring

• Gives an idea of whether CAD is present, despite a lack of symptoms or is likely to develop in next few years develop in next few years.

• Non invasive and less time consuming.

• No contrast required needed.

• The examination can suggests the presence of CAD even when the coronary arteries are <50% narrowed.

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LIMITATIONS

• Not all calcium deposits mean there is a blockade and not all blocked arteries contain calcium.

• The earliest form of CAD soft plaque, cannot be detected by cardiac CT.

• A high heart rate interferes with the test.

• Men <35 yrs and women <40 yrs are not likely to benefit from cardiac CT for calcium scoring unless there is risk factors such as diabetes or a strong family history of heart disease.

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Transthoracic echocardiography imaging of coronary arteries

• With available technique, it is possible completely evaluated left anterior descending and a part of posterior descending artery.

• It is nowadays possible to investigate LAD in 98% of patients and PDCA in 60–70% of patients

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Transthoracic positioning of probe in order to highlight the two major coronary arteries

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Transducer beam orientations to the LAD and to posterior descending CA with the corresponding echocardiography images of the mid-distal tract of LAD.Pulse-wave flow and posterior descending coronary artery (PDCA).

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Stress Echocardiography

• Echo combined with exercise or pressor agents like Dobutamine.

• There are two techniques for performing stress echo:-

a) Detection of wall motion abnormalities induced with exercise/ dobutamine.

b) Measurement of altered myocardial perfusion on contrast ECHO.

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• The hallmark of myocardial ischemia during stress echo is the occurrence of reduced systolic wall thickening

• Precedes chest pain and ST-T wave changes, which makes stress echo more sensitive than exercise treadmill ECG testing.

• Limitation- a) Poor inter-observer agreement b) Optimal acoustic window may not be

present in every patient.

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INTRAVASCULAR ULTRASOUND.

• Intravascular ultrasound (IVUS) is catheter based imaging technique, using a specially designed catheter with a miniaturized ultrasound probe attached to the distal end of the catheter

• Allows the application of ultrasound technology to see inside of coronary artery.

• Used in the coronary arteries to determine the amount of atheromatous plaque

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Procedure

Carried out during coronary catheterization procedure

A miniature transducer within a catheter is introduced in vessel lumen as distal as possible

Automatically pulled back @ 0.5 mm/sec

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IVUS contd….Advantage : 1. visualization of complete circumference of

vessel wall as well as the plaque 2. allows stenosis measurement with direct

planimetry 3. evaluation of diffusely calcified ostial or

bifurcation stenosis.

Disadvantage : 1. Invasiveness 2. Cost.

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MAGNETIC RESONANCE IMAGING IN CAD

• Coronary MRA has not gained acceptance for screening of CAD.

• Difficulties for MRA- # Small caliber of coronary artery- LMCA- 4-6 mm LAD, LCA & RCA- 3-4mm # Tortuous course # Respiratory motion Artifacts # Coronary artery motion artifacts during cardiac

cycle

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• When properly executed, the breath-hold technique with cardiac gating yields extremely good quality images of the coronary arteries

• Navigator-echo Sequence makes up for the respiratory movements with some degradation of image quality

• Accuracy of MRA in these proximal segments was approximately 90%

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MAGNETIC RESONANCE IMAGING

• First choice in evaluation of proximal coronary pathology in young and in particular if associated congenital anomalies are present

• The limitations for imaging the distal coronary arterial segments remain

• The use of contrast agents improve the signal-to-noise ratio in these distal coronary branches

• In future with the advent of shorter scan times better post processing software -the diagnostic accuracy of 3D, navigator-echo MR angiography will increase

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Advantages of Coronary MRI

No radiation and minimal invasiveness (IV injection)

3-dimensional anatomic images (3D coronary artery and myocardial imaging)

Comprehensive functional imaging - Myocardial mechanical work

- Myocardial perfusion - Myocardial oxygenation - Myocardial Viability

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Detailed view on the right coronary artery in the atrioventricular groove between the right ventricle (RV) and atrium (RA). The arrows indicate stenoses in the proximal and mid segment. (B) Corresponding conventional coronary angiogram.

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Example of a significant stenosis (arrow head) in the left anterior descending coronary artery (LAD). (A) Conventional coronary angiogram. (B) Magnetic resonance imaging. Ao, aorta; LM, left main; LV, left ventricle; RVOT, right ventricular outflow tract.

MYOCARDIAL PERFUSION IMAGING• Thallium-201/Technetium 99m labelled agents

like Tc99m-sestamibi are used in MPI.

• Principle- During stress, blood flow increases in normal coronary arteries but not in stenosed artery. As a result, myocardium distal to the stenosis remains hypoperfused.

• Represented as regions of decreased perfusion on stress images.

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Coronary artery anomalies

• Occurs in 0.3 to 1% of general population

• Important cause of sudden cardiac death.

• Can be hemodynamically significant (Malignant) or insignificant (Benign).

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Congenital variation of coronary anatomy• Angelini has suggested classifying coronary

anomalies into three categories: 1. Abnormalities of the coronary ostia: a) High Take off b) Multiple ostia c) Single coronary artery d) Anomalous origin of coronary artery from

pulmonary trunk e) Origin of coronary artery or branch from

opposite or noncoronary cusp with abnormal course

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2. Anomalous course: a) Myocardial bridging b) Duplication of arteries

3. Anomalies of termination: a) Coronary artery fistula b) Coronary arcade c) Extra cardiac termination.

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Single coronary artery .(a)Oblique VR image of the top of the heart shows only one coronary artery arising from the left coronary sinus. The RCA (arrow) courses between the aorta(A)and the pulmonary artery(PA).(b)On a sagittal oblique VR image, the single coronary artery demonstrates a high takeoff (arrowhead) above the sinotubular junction.

Coronary anomaliesCoronary anomalies

A. Benign or Minor Coronary Anomalies 1. Left Cx artery arising from right aortic

sinus – Most common

2. Independent origin of LAD artery and Cx from the left aortic sinus –

The absence of LMCA is the common anomaly of the left coronary vessel system.

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1. RCA arising from left coronary sinus: Most common malignant coronary anomaly. Present in 20—25% of cases. RCA has inter-arterial course and prone for compression

Malignant or major coronary Anomalies

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2. LMCA arising from right aortic sinus :LMCA courses between aorta and pulmonary artery. 60 % die before are 20 during sternous exercise.

Contd…..

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3. Anomalous origin of LMCA, LAD or RCA from the pulmonary trunk: Anomalous origin of LMCA is called Blant-White-Garland syndrome, whereas if anomalous origin of RCA is called reverse Blant-White-Garland syndrome.

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4. Coronary Artery fistula: communication between one or two coronary arteries and a cardiac chamber or systemic vein. Large AV communication produce myocardial perfusion deficit.

5. Myocardial bridging: Epicardial segment of a coronary artery  tunnels through a portion of myocardium.Involves middle segment of LAD.

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CORONARY ARTERY DISEASES

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What is coronary artery disease ?• Coronary artery disease (CAD) is a complex

disease due to reduced or absent blood flow in one or more of the arteries that supply the heart. 

• Excluding congenital anomalies , it is usually caused by atherosclerosis.

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1. Atheromatous coronary artery disease

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• Typical major coronary artery branches have internal diameter of 2.5-3.5 mm; LCA having internal diameter of about 4mm.

• Atheromas due to chronic endothelial injury

• Flecks of calcification - indicate obstructive atheromatous disease.

• Calcification is the rationale for using CT to detect asympt. CAD.

• A reduction in lumen diameter >60% is enough to represent a hemodynamically significant stenosis.

• Chronic increase of size of plaque leads to stable angina or ischemic cardiomyopathy.

• Acute changes, especially plaque rupture lead to a variety of “acute coronary syndrome” most imp. are unstable angina & MI.

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Conditions result from CAD is :-

1. Angina Pectoris

2. Myocardial Infarction

ANGINA PECTORIS: Symptom complex caused by transient myocardial ischemia d/t fixed atheromatous stenosis of one or more arteries.

Types : It has 3 types :-- 1.Stable Angina 2. Un stable angina & 3.Variant Angina (Prinzmetal’s or

resting angina) 105

Myocardial Infarction• Irreversible necrosis of heart muscle secondary to

prolonged ischemia

• Presents with prolonged chest pain, anxiety, breathlessness and collapse

• Sudden cardiac death can occur d/t ventricular fibrillation.

• Diagnosed by raised cardiac biomarker

• Role of imaging comes after initial stabilization of the pt.

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Coronary Artery Disease

2) Aneurysm of coronary artery

# Atheromatous-may lead to localized or part of generalized ectasia.

Symptom or death by rupture or pressure on the parent artery or by distal embolisation.

# Inflammatory -‘Kawasaki Syndrome’(mucocut. L.N.syndrome)-Aneurysm & stricture of cor. artery in children

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Imaging of coronary arterial and heart disease

X-Ray findings

i) Coronary artery calcification :Best seen in proximal LCA & may be identified near the aortic root on both PA & Lat. commonly in pts. >70 yrs.

In pts <50yrs calcification -calcified atheromatous plaque.

ii) Acute MI ----- CXR is normal in acute phase(within 24 hrs) ----- Later changes – # Upper lobe diversion PVH, Septal thickening # Alveolar pulmonary edema MC feature

identified. # Pleural effusion if there is prolonged left heart

failure. Progressive cardiomegaly occur more often in

anterior MI it is a bad prognostic sign.108

iii) Acute MR: # It is usually due to dilatation of mitral valve

annulus or papillary muscle rupture. # Cardiomegaly with or without PVH. # CXR feature is same as in other cause of MR

iv) Rupture of IV septum: rare complication. # It is between 4-21 days infarction. # Pulmonary plethora & pulmonary edema.

v) Lt ventricular rupture: it is a common complication.

# Pericardial tamponade occurs-leads to death

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vi) Lt ventricular aneurysm: MC complication in clinical practice.

# Occurs if the infarcted segment is large. # Most Commonly in the cardiac apex in assoc.

with anterior infarct. # Localized bulge on the left heart border on

CXR, but may not be seen if aneurysm is not well demarcated.

# Curvilinear calcification in the walls of aneurysm after several yrs.

vii) Pericardial effusion: Most commonly associated with partial ventricular rupture.

Mild cardiomegaly on CXR.110

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ECHOCARDIOGRAPHY

Ostia of main coronary arteries may be imaged.Helps in distinguishing anomalous origin of

coronary arteries presenting with lt ventricular disease, dilated cardiomyopathy, or myocarditis.

Useful in detecting coronary artery aneurysm e.g. Kawasaki disease.

Transthoracic & transesophageal USG can be helpful in imaging proximal rt & lt coronary artery.

Echo is the tech. of choice for detection & quantification of ventricular aneurysm & detection of concomitant thrombus.

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STRESS ECHO:A stressor stimulus e.g. exercise or a

pharmaceutical agent like Dobutamine is applied & then followed be echo.

Improves sensitivity for detecting CAD.

MYOCARDIAL PERFUSION IMAGING:Radioactive tracer (Thallium201, Technitium-

99m labeled tracer) is injected and scintigrams are obtained at rest and during stress.

A perfusion defect during stress but not at rest provides e/o reversible myocardial ischemia.

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Coronary CT angiography• Best non invasive modality for depiction of

coronary artery anatomy and disease

• Evaluates the plaque burden and morphology accurately

• Important “ rule –out” modality in patients with atypical chest pain

• Technique of choice to evaluate bypass graft.

• Dose limiting techniques, coupled with adherance to ALARA principle may shift the risk-benefit ratio in favour of this modality.

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CARDIAC MRICardiac MRI is a established tool in assessing

congenital heart disease & diseases of aorta & pericardium, but role in coronary artery evaluation is not very significant.

—These noninvasive techniques are useful in initial screening for coronary artery stenosis , evaluating bypass grafts and determining the patency of infarct related artery after coronary thrombolysis.

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Imaging in post bypass surgery and stent patients

• CCTA is highly recommended for follow up evaluation of CABG.

• Unlike invasive coronary angiograms, MDCT does not require accurate localization of Ostia of venous graft for selective contrast injection.

• Sensitivity of 97-100 % for graft stenosis/occlusion

• However, surgical metallic clips may lead to artifact

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• Routine application of CT to assess patients with coronary stents is currently not recommended.

• Visualization of the stent lumen is often affected by artifacts, and especially the PPV is low.

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Fig. LAD thrombus demonstrated with MDCTA. A: Patient with a thrombus in the LAD (arrow). B: Multiplanar reformatting of the same data set demonstrating the extent of the thrombus formation in the LAD. C: In the coronary angiogram, only slightly diminished enhancement is visible at the corresponding location

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Fig. Stenosis of LAD demonstrated with MDCTA. A: 55-year-old male patient with a single-vessel disease in the LAD (arrow). B: Finding of CTA confirmed by cardiac catheter with a high-grade stenosis in the midsegment of the LAD.

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Fig. Acute coronary syndrome. anterior wall perfusion deficits on short axis was noted(A) and vertical long axis (B) reconstructions are seen, including subendocardial components (thin arrows). C: A reconstructed image to detail the coronary arteries shows a filling defect (yellow arrows) occluding the LAD and smaller nonocclusive plaques (white arrows) in a large diagonal branch. Note the cardiac vein (blue arrowhead) immediately posterior to the diagonal branch. 121

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Conclusion

• Non- invasive cardiac imaging is now central to diagnosis and management of CAD patients, however cannot replace existing modalities

• ECHO c/be performed bedside and is advantageous for acutely ill patients

• Cardiac catheterization offers the option of intervention

• Myocardial perfusion scanning and MDCT can be offered to patients with intermediate likelihood of CAD

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• MDCT c/become investigation of choice for evaluation of bypass graft in CABG patients

• Currently CMR lags behind CTA for non invasive coronary angiography, it is already emerged as a highly effective method for assessing ventricular function , myocardial mass and myocardial viability.

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