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

2. 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)

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

6. 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

7. 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 nd Dose Metoprolol 100mg and wait 30min
History of asthma switch to Verapamil 240mg one hour before.

8. 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.

9. 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

10. Nitro Contraindications
Allergy
Viagra and Like meds

11. 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

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

13. 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.

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

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

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

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

18. 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.

19. 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.

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

21. Business related Issues
Potential ICD-9 Codes
chest pain, unspecified
precordial pain
painful respiration
chest discomfort/tightness
Abnormal chest sounds

22. How Do They Compare?

23. 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

24. 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

25. 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)

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

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

28. 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

29. 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

30. 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!!!

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

32. 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%

33. 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):

34. 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):

35. Atheromatous Plaque

36. 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):

37. 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….

38. 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.

39. 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.

43. 30 year old male with Strong Family History of CAD

44. 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

45. 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.

46. 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.

47. 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.

48. 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

49. The End

52. 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

53. Pulmonary Emboli

54. 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.”

55. EKG Dose Modulation
40%
80%

56. EKG Gated Dose Modulation

57. 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

58. 65yo, wf, diabetic with chest pain and SOB.

59. Mild CAD, and…

60. Pulmonary Emboli

61. 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.

62. 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

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

64. Histology

65. Injectors
Any power injector will do
Dual phase injector preferred

66. Medrad

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

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

69. 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

70. 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 : mA
Lightspeed 16 Pro : mA (800mA)

71. 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 % of the R-R interval
Peak mA between 40-80%
Min mA set at 20-40% of max mA

72. 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

73. Typical Injection Protocol
Manual Timing Bolus= 20cc contrast+20cc Saline
Coronary CTA= cc contrast + 50cc Saline

74. Scan Parameters
16 X 0.625mm, <15 slab, sec 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

75. 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.

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

77. 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.”

78. 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.