Darrin Johnson, MD April 20th, 2005 Radiology of Huntsville Coronary CTA Darrin Johnson, MD April 20th, 2005 Radiology of Huntsville

What is Coronary CTA? Coronary CTA is a non-invasive minimal risk procedure to directly visualize the coronary arteries It is NOT calcium scoring It involves administration of 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)

Not your standard CT Angio of the Chest Requires some patient prep Beta Blockers mandatory Sublingual nitro on table helpful Technically more labor intensive

Patient Preparation No Caffeine for 12 hours prior to exam Everyone gets Beta-Blockers (Verapamil can be substituted) IV Heplock BEFORE they get into the room Antecubital only, left better than right, 18g-20g

Beta-Blocker Protocols Metoprolol 100mg one hour before study. IF HR<62bpm Done If HR 62-70bpm 2nd Dose Metoprolol 50mg and wait 30 min If HR >70bpm 2nd Dose Metoprolol 100mg and wait 30min History of asthma switch to Verapamil 240mg one hour before.

60-75bpm we can do if they have a regular rhythm. Goal Heart Rate <60 bpm makes us happy 60-75bpm we can do if they have a regular rhythm. Acceptable images, but you will have to work harder for them.

Medications at Scan Time Oxygen (2L NC) Nitro Spray (1/150gr sl- one full plunger) ?Sedation (Valium 10mg one hour before) If HR>75 and fail max Beta-Blockers

Nitro Contraindications Allergy Viagra and Like meds

Contraindications Atrial Fibrillation Tachycardia Beta Blockade Contraindication Can use calcium channel blocker (Verapamil 240mg one hour before, can repeat once) Acute chest pain Heart Block Renal Failure (Creat>1.5) Contrast Allergy NO pacemakers

What about Pacemakers? The real problem is artifact from the right atrial appendage lead. Presence of a cardiologist to dial down the heart rate?

Coronary CTA: Why do it? In 2001, 3.51 million cardiac caths performed Only 9% were emergent 1.7 Million caths for diagnosis only (30-40% negative) Every year 150,000 Americans die of sudden death related to acute coronary syndrome and smaller number experience MI as first sign of CAD What is needed is a non-invasive, minimal-risk, outpatient procedure to detect early signs of CAD so that risk factor modification and medical management can be initiated early enough to reduce the number of patients experiencing acute coronary syndromes.

Coronary Atherosclerosis Intimal Thickening Coronary CTA Atheroma Rupture/Erosion Healing Hemorrhage Stress Test Cath Calcified Nodule Fibrocalcified Plaque Thrombus Wall Changes Stenosis Occlusion

Patient Selection: Who should Get it? A Traditional risk factor should be required to have a coronary CTA.

Primary CAD Risk Factors Cigarette Smoking Hypertension ( >140/90 mmHg ) Elevated LDL ( >130 mg/dl ) Low HDL ( < 40 mg/dl ) Diabetes Mellitus Family History

Non-Traditional Risk Factors Homocysteine levels C-reactive protein Small LDL particle size Inherited Syndromes

What about Symptomatic Patients? Initially, as an outpatient procedure, we do not want patients with acute, undiagnosed classic chest pain in our office. Stable angina under a physician’s care and unexplained atypical chest pain is OK.

When do I order Coronary CTA? Asymptomatic patient with traditional risk factors. Strong positive family history. Examine bypass grafts and stents. Prior to cath in patients with atypical symptoms. If HU units are able to be measured- follow up? Before stress nuc med, treadmill or stress echo. These tests measure flow reserve and will be normal in patients with soft plaque and no stenosis. Also higher rate of false positives with these exams cause unnecessary cath’s. Clarify the equivocal stress test.

Business related Issues Potential CPT codes 71275 CT angio chest 71260 CT Chest No ICD-9 code for the work up of asymptomatic patient with risk factors

Business related Issues Potential ICD-9 Codes 786.50 chest pain, unspecified 786.51 precordial pain 786.52 painful respiration 786.59 chest discomfort/tightness 786.7 Abnormal chest sounds

How Do They Compare?

Images by GE CT-A Color composite image (not intended as diagnostic tool) Used here to show global picture and to focus on two areas of interest: Stent in the RCA which clinically has remained patent Area of apparent disease in LAD at bifurcation of diagonal LAD Stent in RCA

RCA and Stent Stent CTA Fluoroscopy Angiography Stent well delineated by CT-A Note mild proximal narrowing Seen with difficulty on fluoro prior to angiography

LAD by CTA Image appears to show several areas of calcification in vessel (blue arrows) Lesion of borderline significance appears in proximal LAD (green circle) Moderate disease at bifurcation of left main (yellow circle)

How Does Angiogram Compare? LAO angiogram RAO angiogram Angiogram does not clearly show disease in the same areas

IVUS Left Main - NL Ostial LAD - 40% Left Main Ostial LAD Proximal LAD Bifurcation Noninvasive Invasive Proximal LAD - 30% Bifurcation - 50%

Pressure wire/fractional flow reserve Post bifurcation Aorta Distal Pressure wire confirms absence of pressure gradient in proximal LAD With adenosine injection, pressure separation confirms bifurcation lesion of moderate severity (FFR = 0.76) Thus pressure wire confirms physiologic importance of bifurcation lesion Proximal LAD

CCTA vs Invasive Angiography Good IVUS and pressure wire correlation with CT-A Invasive coronary angiography missed most of the important disease IVUS and pressure wire are highly invasive while CT-A is noninvasive

Teaching Points 1. “The current gold standard for detecting coronary artery stenosis is coronary catheterization, but it is not a very shiny gold.” 2. Cath Correlation without IVUS is a poor tool to evaluate Coronary CTA!!!

Stenosis Detection >50% Nieman, et.al. Circulation 2002; 106: 2051-2054. 16 slice CT, 12 for cardiac. Sensitivity = 95% Specificity = 86% PPV = 80% NPV = 97%

Stenosis Detection >50% Ropers, et.al. Circulation 2003. 16 slice CT, 12 for cardiac, slice thickness .75mm. Excluded 12% of vascular segments. Sensitivity = 92% Specificity = 93% PPV = 79% NPV = 97%

Kuettner A, Beck T, Drosch T, et.al. JACC, 4 Jan 2005; (45): 123-27. Diagnostic Accuracy of Noninvasive Coronary Imaging Using 16-Detector Slice Spiral CT with 188ms Temporal Resolution N=72 51% received beta-blockers for HR>65 62/936 segments nondiagnostic but all segments included in the analysis Compared with cath 117 relevant lesions (diameter stenosis 50%) Sensitivity = 82% Specificity = 98% PPV = 87% NPV = 97% Correct clinical diagnosis of significant CAD = 90% All stenoses detected by MDCT = 72% Kuettner A, Beck T, Drosch T, et.al. JACC, 4 Jan 2005; (45): 123-27.

Improved diagnostic accuracy with 16-row Multislice CT Coronary Angiography All had stable angina or atypical chest pain Beta-blockers used for HR>75 64 significant lesions Sensitivity = 95% Specificity = 98% PPV = 87% NPV = 99% Mollet N, Cademartiri F, Krestin G, et.al. JACC, (45): 128-32.

Atheromatous Plaque

CCTA v. IVUS 58 vessels 78% sensitive for hypoechoic plaque (HU 49 +/-22) 78% sensitive for hyperechoic plaque (HU 91 +/- 22) 95% sensitive for calcified plaque (HU 391 +/- 156) Leber et.al., J Am Coll Cardiol, 2004; 43(7): 1241-7.

CCTA v. IVUS 83 coronary segments Any plaque = 78% sens, 87 spec. Ca++ plaque = 94% sens, 94% spec. NonCa++ plaque = 78% sens, 87% spec. But….

CCTA v. IVUS If limited to proximal vessels: Any plaque = 92% sens, 88% spec. Ca++ plaque = 95% sens, 91% spec. NonCa++ plaque = 91% sens, 89% spec. Achenbach, et.al., Circulation, 2004; 109:14-7.

What can the past tell us about the future? Natural history of CTA abdomen, neck and intracranial arteries. Period of time when older and newer technologies will overlap and both be used to diagnosis until confidence in new technology strengthens.

30 year old male with Strong Family History of CAD

How is it Different from other heart tests? Calcium Scoring: only measures quantity of calcium, not stenosis or soft plaque PET/ Stress Test: myocardial perfusion only, no anatomy. Echocardiography: Wall motion and real time anatomic evaluation of the four chambers Cardiac Cath: Lumen only-no wall information. Evaluate stenosis. Cannot characterize plaque. Better delineates small vessels

Coronary CTA- Strengths Noninvasive. Only NONINVASIVE study that visualizes the vulnerable plaque. Identifies significant disease in patients with zero or near zero Calcium Scores. Better sensitivity and specificity than nuclear medicine stress tests, stress echo and standard treadmill studies.

Coronary CTA- Strengths Can measure HU of plaques and characterize them as fatty, atheroma, fibrosis, calcium. Can evaluate status of bypass grafts. Can determine stent patency. Future- measure the thickness of the fibrous cap, functional CT. Evaluates portions of mediastinum and lungs.

Coronary CTA- Weaknesses Cannot accurately measure stenosis with heavy, calcified plaque burden. Measured stenosis is different from cardiac catheterization which is an intra-arterial pressure injection with nitroglycerin on board. Occlusions can be missed by brisk collateral flow. Physician time intensive.

What do I do with this information? Reports will be classified in one of four categories of severity: Normal Mild Plaque with No stenosis: Risk factor modification. Consider statin or ASA therapy. Moderate Plaque with mild/Mod stenosis: Statin/ASA therapy and myocardial perfusion study. Severe Plaque and stenosis: Cardiac Cath

The End

Why a radiologist? 10%-35% of all studies have significant other chest findings (Nodules, dissection, nodes etc) Currently, we are scanning the chest completely for a cardiac study (this may change) Radiation Currently, the dose for this study is in the range of a cardiac catheterization EKG dose modulation

Pulmonary Emboli

You must know Chest CT before you can read Coronary CTA.” Teaching Point “Looking at the entire image is critical. Ancillary findings do occur on CCTA. You must know Chest CT before you can read Coronary CTA.”

EKG Dose Modulation 40% 80%

EKG Gated Dose Modulation

The Vulnerable Plaque The chemical composition of a plaque determines it’s vulnerability to rupture Cholesterol is key part of the makeup Plaques are an inflammatory process Plaques initially grow extrinsic and bulge adventitia, then grow into the lumen resulting in stenosis

65yo, wf, diabetic with chest pain and SOB.

Mild CAD, and…

Pulmonary Emboli

Coronary CTA- Advantages over Nuclear Stress Tests High Negative Predictive Value. “Negative is negative.” Positive Predictive Value equal or better with CTA. Data will DEFINITELY improve with 16 channel CT. Detects subclinical disease.

Why is this Technology available only now? Heart and coronary arteries in constant motion. CT scan speed has increased and EKG dose modulation Decrease radiation during systolic phase when imaging of coronary circ is non-diagnostic

Clinical Presentations of CAD Coronary CTA Clinical Presentations of CAD Acute Coronary Syndrome Myocardial Infarction Sudden Death Angina Pectoris Stable Unstable

Histology

Injectors Any power injector will do Dual phase injector preferred

Medrad

Image Comparison Contrast in left heart Saline in right heart RCA clear of artifact

Image Comparison Contrast in Left heart Contrast in right heart RCA more difficult to Visualize Leads to tracking problems

Visipaque 320 on all Coronary CTA’s Contrast Density is NOT the dominant issue! HR is always the dominant issue Decrease in iodine load results in decrease symptoms Decrease symptoms results in decrease in HR variability Decrease recon time and better image quality Visipaque 320 on all Coronary CTA’s

LightSpeed Pro 16 Improve small vessel visualization Increase gantry speed (.4sec c/w .5sec) EKG Dose modulation. Decrease radiation exposure Increased mA: decreased artifacts related to surgical clips and calcification. Lightspeed 16 : 400-440mA Lightspeed 16 Pro : 400-670mA (800mA)

EKG Gated Dose Modulation Decreases radiation exposure during the time in the cardiac cycle where you are unlikely to reconstruct the coronary arteries. Never reconstruct 0-30% and 81-100% of the R-R interval Peak mA between 40-80% Min mA set at 20-40% of max mA

EKG Gated Dose Modulation Always reconstruct 70-80% of the R-R interval by 5’s With variable HR’s or motion reconstruct 40-80% by 5’s

Typical Injection Protocol Manual Timing Bolus= 20cc contrast+20cc Saline Coronary CTA= 80-100 cc contrast + 50cc Saline

Scan Parameters 16 X 0.625mm, <15 slab, 15-20sec breath hold, 120 kvp, > 400mA Large Patients = 16 X 0.625mm, <15 slab, 15-20sec breath hold, 120kvp, >400 mA. Retrospectively thicken to 1.25mm if needed. COPD = 16 X 1.25mm, <15 slab, 8-10 sec breath hold, 120 kvp, >400mA

Pearls Watch HR during all breath holds to adjust scan parameters as needed. HR normally decreases 5-10 bpm during breath hold COPD patients get hypoxic and HR increases with breath hold switch to COPD protocol On large patients, opt for increasing slice thickness to 1.25mm rather than decreasing mA.

These studies were NOT done on a high mA, EKG dose modulated system.

Teaching Point “CCTA is outstanding for determining who does NOT have CAD. These patients can be safely evaluated at the primary care level. In some circumstances CCTA over calls disease but it still outperforms stress tests.”

Summary Coronary CTA is not just a modified CT Pulmonary angiogram study. Requires more active technologist and radiologist involvement and modification. Tremendous potential to detect significant CAD earlier. The technology will only continue to improve.