Nuclear Perfusion Imaging of Angina

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1 January 2002 Nuclear Perfusion Imaging of Angina Davin Quinn HMS III Beth Israel Deaconess Medical Center Radiology Department

2 Goals of Presentation Understand what a perfusion scan is Understand what it can tell us when a patient has chest pain 2

3 Introduction Mr. O Pt. is a 66 y.o. male IDDM x 28 yrs. HTN Hypercholesterolemia 80 pack-year smoker No previous cardiac hx 3

4 HPI Band-like chest pain, 10/10 Increasing in severity over last 2 months Brought on with exertion In ED, relieved with sublingual NTG Perfusion scan was ordered. 4

5 What is a Nuclear Perfusion Scan? Injection of radioactive isotopes that accumulate in heart tissue and are detected by a gamma ray sensor. The distribution of the isotope corresponds to the amount of blood reaching a given area. The test can be done under exercise stress, or at rest (90% occlusion detected at rest; 50% occlusion detected stressed) 5

6 Who should get a Scan? Step 1: Take history/perform exam Step 2: Assess CRFs Step 3: Obtain resting EKG Step 4: If nl. EKG and low risk, STOP Step 5: If med/high risk, get exercise EKG Step 6: If exercise EKG nl, STOP Step 7: If exercise EKG abnl, go to scan 6

7 Mr. O s Stressed Perfusion Scan Modified Bruce protocol treadmill 4 min. duration 87% of max HR obtained Sx: 10/10 chest pain Pain resolved after 6 min. EKG: 3 mm. horizontal ST depressions in V4-V6 (lateral territory) 7

8 EKG Changes Pre-stress Post-stress 8

9 Modified Bruce Protocol Bruce protocol: Begin walking at 1.7 mph and 10% grade (5 METS), gradually increase q3min. up to 5.5 mph, 20% grade. Modified = 2 x 3 min. warm up periods at 1.7 mph and 0% grade, and 1.7 mph and 5% grade respectively. Modified for pts. with exercise limitations due to cardiac disease. 9

10 METS? 3-5 METS = easy walking 5-7 METS = raking leaves, singles tennis 7-9 METS = running 6-7 mph 13 METS =? 10

11 METS? 3-5 METS = easy walking 5-7 METS = raking leaves, singles tennis 7-9 METS = running 6-7 mph 13 METS =? 11

12 Gamma Ray Tracing Step 1: Thallium injection at the door Step 2: 15 min. Step 3: Exercise stress 60 min. Step 4: MIBI 1 min. prior to quitting Step 5: 90 min. Three agents: Thallium Sestamibi Tetrofosmin 12

13 Thallium Potassium analogue High extraction fraction Thallium uptake dependent on cell viability, intact Na/K ATPase pump 13

14 Thallium Disadvantages Low energy emission (70-80 kev) Low energy rays scatter and attenuate easily Long half-life (74 hrs), which limits dose, count rate and efficiency Redistribution of tracer to ischemic areas 14

15 Sestamibi/Tetrofosmin Tc99m 2-methoxyisobutylisonitrile Uptake not related to Na/K ATPase activity. Passive diffusion across and binding to intact sarcolemmal & mitochondrial membranes. No redistribution mibi stays in cells, gives snapshot of perfusion at time of ischemia. 15

16 Sestamibi/Tetrofosmin Less total radiation than Thallium Shorter half-life (6 hrs) 16

17 Head to Head Thallium 70 kev t1/2 = 74 hrs Rad dose = 0.21 mci Sestamibi 140 kev t1/2 = 6 hrs Rad dose = 0.02 mci 17

18 Best of Both Worlds Current protocol: dual-tracer Give thallium for rest imaging Give sestamibi for exercise imaging Brings test time under 3 hours Single-tracer takes 6-24 hours 18

19 Epidemiology Sensitivity ~ 90% for CAD Specificity ~ 90% for CAD False positives Breast tissue ~ anterior wall defect Diaphragm ~ inferior wall defect LBBB ~ perfusion defect Upward creep: apparent reversible defect in the inferior and basal inferoseptal walls as heart returns to nl. position following exercise. 19

20 Mr. O s Scintigraphy Results Severe defects in: inferior portion of lateral wall lateral portion of inferior wall Lateral reversible Inferior partially reversible 20

21 Mr. O s Perfusion Scan Images stress resting 21

22 Mr. O s Perfusion Scan Images stress resting 22

Imaging Views (From the Cardiovascular Imaging Committee, American College of Cardiology; the Committee on Advanced Cardiac Imaging and Technology, Council of Clinical Cardiology, American Heart

23 Imaging Views (From the Cardiovascular Imaging Committee, American College of Cardiology; the Committee on Advanced Cardiac Imaging and Technology, Council of Clinical Cardiology, American Heart Association; and the Board of Directors, Cardiovascular Council Society of Nuclear Medicine: ACC/AHA/SNM Policy Statement: Standardization of cardiac tomographic imaging. J Nucl Cardiol 1:117, 1994.) 23

24 Mr. O s Transverse Section RV LV Filling defect 24

25 Perfusion Territories (Modified from Port SC (ed): Imaging Guidelines for Nuclear Cardiology Procedures, Part 2. J Nucl Cardiol 6:649, 1999.) 25

26 Mr. O s Vertical Long Section LV Base Apex Filling defect 26

27 Mr. O s Horizontal Long Section Apex LV Base 27

28 Mr. O s Polar Map of LV Filling defect 28

29 Perfusion (From Wackers FJTh: Exercise myocardial perfusion imaging. J Nucl Med 35:726, 1994.) 29

30 Why Bother with Nukes? Non-invasive Digital images are quantifiable Highly reproducible Findings on perfusion scan correlate well with disease outcomes, better than cath alone. Able to risk-stratify pts into low/med/high risk groups for future cardiac events, and be aggressive/conservative on this basis 30

31 Why not go straight to cath? >10,000 subjects w/ chest pain 5000 had a scan before cath 5000 had cath only Result: no difference in outcome, but total cost and follow-up cost were 30-40% lower for scan group. (Shaw LJ, Miller DD, Romeis JC, et al: Gender differences in the nonivasive evaluation and management of patients with suspected coronary artery disease. Ann Intern Med 120:559, 1994.) Supported by the EMPIRE study 31

32 Mr. O s Cardiac Catheterization EF 45% LMCA: 60% occluded, mod. calcification LAD: 70%, mod. calc. pcx: 90%, ostial calcific lesion RCA: 90% mrca: 70%, with thrombus 32

33 Coronary Anatomy http-- 33

34 Mr. O s Cardiac Catheterization Images RAO Caudal LM LAD C 34

35 Cardiac Catheterization Images RAO Caudal 70% LM LAD C 90% 35

36 Mr. O s Cardiac Catheterization Images LM LAD D 36

37 Mr. O s Cardiac Catheterization Images LM 40% LAD D 37

38 Mr. O s Cardiac Catheterization Images LM LAD 38

39 Mr. O s Cardiac Catheterization Images 60% LM LAD 39

40 Mr. O s Cardiac Catheterization Images LAD LM C 40

41 Mr. O s Cardiac Catheterization Images LAD LM C 41

42 Mr. O s Cardiac Catheterization Images LM C 42

43 Mr. O s Cardiac Catheterization Images LM C 43

44 Mr. O s Cardiac Catheterization Images RCA PDA 44

45 Mr. O s Cardiac Catheterization Images RCA Filling defects = thrombi Distal occlusion 90% PDA 45

46 Hospital Course Dx: severe 4-vessel CAD Admitted to Farr 3, seen by CT Surgery Tx: 4V-CABG asap 46

47 Summary Nuclear perfusion scans are highly diagnostic and prognostic tests that are minimally invasive. They demonstrate physiologically significant perfusion deficits, often above what anatomical studies can show. Cost-effective for med/high risk patients. 47

48 The End 48

49 References Braunwald E: Heart Disease: A Textbook of Cardiovascular Medicine, 6 th edition. WB Saunders Co., Link KM and Lesko NM: The Radiologic Clinics of North America: Cardiac Imaging, Vol. 32, 3. Philadelphia, WB Saunders Co., May

50 Acknowledgements Pamela Lepkowski Larry Barbaras and Cara Lyn D amour, our webmasters 50

Radiologic Assessment of Myocardial Viability

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