1. Update in Cardiac Stress Testing and Nuclear Cardiology
Matthew Schumaecker, MD, FACC, FASNC
Medical Director, Nuclear Cardiology Division of Cardiology, Carilion Clinic
Assistant Professor of Medicine VTC School of Medicine

2. Objectives After 50 minutes, the awake audience member should have:
A renewed conceptual framework of cardiac stress testing
A better understanding of the epidemiology behind stress testing, particularly nuclear cardiac testing
An introduction to novel technologies in nuclear cardiology with emphasis on low-radiation techniques

3. Part I: What is Cardiac Stress Testing

4. Overview of Stress Modalities
Stress Modality
Imaging Modality
Exercise
Treadmill
Bicycle
Pharmacological
Dobutamine
Atropine
Adenosine
Dipyridamole
Surface electrocardiography
Echocardiography
Myocardial Perfusion Imaging:
SPECT
PET

5. Stress Modality: Exercise
Disadvantages:
Cannot perform in patients with significant functional limitations
ECG uninterpretable in LBBB, LVH, resting ST abnormalities, WPW, PPM and SPECT can be false positive in LBBB and patients with PPM
Advantages:
Least expensive stress modality
Lowest concern for adverse reaction
Produces physiologic ischemia in CAD
Threshold of reproduction of ischemic symptoms
Derived functional data is strongly predictive of cardiac mortality

6. Stress Modality: Exercise-Treadmill
Treadmill is most commonly used for exercise
Bicycle is used mostly in echo lab for valve cases (i.e., mitral stenosis) and to assess for exercise-induced pulmonary hypertension.
Patients are put on a standardized protocol which can predict performance based on age and gender (i.e., Bruce, Cornell, Naughton)

7. Stress Modality: Exercise-Treadmill
Bruce Protocol - Treadmill
Most commonly used protocol.
Very well-studied and validated with good prognostic data.
Each stage lasts three minutes
Patient exercises to symptomatic maximum
Stage
Speed (mph)
Gradient (%) I
1.7 10 II
2.5 12
III
3.4 14 IV
4.2 16 V
5.0 18 VI
5.5 20

8. Stress Modality: Exercise
MET = Metabolic equivalent
1 MET = amount of energy expended at supine rest
1 MET ≈ (kcal/hour)/kg
1 MET ≈ 3.5 ml/kg/min VO2
Average maximum exercise threshold in healthy middle-aged male ~ 10 METS

9. Stress Modality: Exercise-Treadmill

10. Stress Modality: Exercise-Treadmill

11. Stress Modality: Exercise - Bicycle
Can obtain respiratory data if equipped
Advantages
More direct measurement of work (i.e., watts)
Disadvantages
Can be cumbersome to set up.
Echocardiographic images obtained during exercise
Takes longer to reach MPHR
Not widely used in US for cardiac stress testing
Useful for evaluating mitral stenosis and exercise induced pulmonary hypertension
Can complement vasodilator stress by producing better images and minimizing symptoms

12. Stress Modality: Dobutamine
Beta agonist
Simulates exercise by positive chronotropy and inotropy.
Can be difficult to achieve 85% MPHR with dobutamine alone
May need to augment chronotropic response with atropine up to 1 mg.
Can cause SAM and LVOT obstruction in patients with significant septal hypertrophy.

13. Stress Modality: Vasodilator
Slide by Dr. Robert Hendel. ASNC 7/07

14. Stress Modality: Vasodilator
Slide by Dr. Robert Hendel. ASNC 7/07

15. Stress Modality: Adenosine
Causes coronary arteriolar vasodilation
Extremely short half life
Given in a four or six minute infusion
Tracer is injected halfway through the protocol
Can cause flushing, diaphoresis, chest pain. Usually resolves within minutes after infusion

16. Stress Modality: Regadenoson Four Types of Adenosine Receptors
A1 – AV Block
A2A – Vasodilate small coronary vessels
A2B – Mast cell degranulation
A3 - Bronchoconstriction

17. ADVANCE MPI-2
Mahmarian et al. JACC Imaging; Aug 2009

18. Stress Modality: Dipyridamole
Trade Name: Persantine
Acts by blocking the cellular uptake of adenosine
Four to ten times less expensive than adenosine
Comparable to adenosine with respect to sensitivity; specificity may be lower
Much longer half life so adverse reactions tend to be more severe
Not used very much in clinical practice

19. Imaging Modalities
Slide by Dr. Robert Hendel. ASNC 7/07

20. Surface ECG Obtained during every stress modality.
Determine underlying rhythm
Assess for arrhythmic response to stress
Assess for ischemic response to stress
ST segment is monitored during all phases of stress to look for significant deviation.
Sensitivity and specificity alone are lower than other modalities (especially in women) but can be complementary to other modalities.

21. ECG Positivity
Tak and Gutierrez. Postgraduate Medicine Online June 2004

22. Stress Echo Pro Con No radiation Higher specificity
Can assess other cardiac chambers and valves.
Can assess valve disease
Can assess pulmonary hypertension
Operator-dependent
Lower sensitivity
No vasodilator option
Non-quantitative

23. Stress Nuclear Pro Con Higher sensitivity Vasodilator option
Quantitative support
Less inter-operator and inter-reader variability
Radiation concern
Does not evaluate valves or other cardiac processes other than myocardial perfusion

24. Part II: Why Do We Stress Test?

25. Part II: Why Do We Stress Test?
Rule out CAD?
Reassure patients?
Reassure ourselves?
Avoid lawsuits?

26. Imaging Modalities: Sensitivity and Specificity

27. Why Do We Stress Test?
To provide a physiologically-based risk assessment in selected individuals which is adjunctive and additive to traditional risk assessment from H&P and models such as Framingham or Reynold’s Risk Score

28. Cardiac Death and MI by SPECT Degree of Normalcy
Hachamovitch R, Berman DS, Shaw LJ, et al. Circulation Feb 17;97(6):
Black boxes– Cardiac death
White boxes – Myocardial infarction

29. Cardiac Death Rate Stratified by Revascularization vs
Cardiac Death Rate Stratified by Revascularization vs. Medical Therapy and by SPECT Degree of Normalcy
Hachamovitch R, Berman DS, Shaw LJ, et al. Circulation Feb 17;97(6):
Black boxes – Medical Therapy
White boxes – Revascularization

30. Part III: Which Patients Do We Stress Test?

31. Part III: Which Patients Do We Stress Test?
Patients at high risk for CAD?
Abnormal ECG
Hyperlipidemia
Hypertensives
Smokers

32. Why Detecting (asymptomatic) CAD Might Not Matter

33. Why Detecting (Asymptomatic) CAD Might Not Matter

34. Is there any role to stress testing asymptomatic individuals?
NOT USUALLY

35. “Special” Asymptomatic Indications
Consideration for class Ic antiarrhythmic
Newly diagnosed cardiomyopathy
CT calcium score > 400 Agatston units
Chemotherapy
MAYBE – high risk (>20%/10 year) diabetics

36. Appropriate Use Criteria

37. Appropriate Use Criteria

38. Part IV: Radiation Safety and Advances in Nuclear Imaging Technology

39. Danger of increased radiation
“ Myocardial perfusion imaging … now accounts for more than 10% of the entire cumulative effective (radiation) dose to the US population from all sources except radiotherapy.”
Einstein AJ. Effect of radiation exposure from cardiac imaging. J Am Coll Cardiol 2012; 59:

40. Society Mandate for Lower Radiation Exposure
The American Society of Nuclear Cardiology has set a goal that accredited nuclear cardiology laboratories should reduce radiation levels to 9 mSv in half of patients by 2014
Journal Nuclear Cardiology 2010; 17:

41. 82,861 patients studied after MI.
77% had cardiac imaging or procedure
For every 10 mSv of low-dose ionizing radiation, there was a 3% increase in the risk of age- and sex-adjusted cancer over a mean follow-up period of five years (hazard ratio per mSv, 95% confidence interval 1.002–1.004).

42. At Carilion, closer to 15.2 mSv
Imaging procedures and their approximate effective radiation doses*
Procedure
Average effective dose (mSv)
Range reported in the literature (mSv)
Bone density test+
0.001
0.00–0.035
X-ray, arm or leg
0.0002–0.1
X-ray, panoramic dental
0.01
0.007–0.09
X-ray, chest
0.1
0.05–0.24
X-ray, abdominal
0.7
0.04–1.1
Mammogram
0.4
0.10–0.6
X-ray, lumbar spine
1.5
0.5–1.8
CT, head 2
0.9–4
CT, cardiac for calcium scoring 3
1.0–12
Nuclear imaging, bone scan
6.3 �
CT, spine 6
1.5–10
CT, pelvis
3.3–10
CT, chest 7
4.0–18
CT, abdomen 8
3.5–25
CT, colonoscopy 10
4.0–13.2
CT, angiogram 16
5.0–32
CT, whole body
variable
20 or more
Nuclear imaging, cardiac stress test
40.7
Source: Mettler FA, et al. "Effective Doses in Radiology and Diagnostic Nuclear Medicine: A Catalog,"Radiology (July 2008), Vol. 248, pp. 254–63.
At Carilion, closer to 15.2 mSv

43. Spectrum Dyamics D-SPECT
Uses CZT (Cadmium Zinc Telluride) crystal instead of tradition NaI
This makes it much more sensitive to photon emissions
Analagous to taking a picture with very high speed film – you need less “light” to get a picture
This allow us to get clear pictures:
More quickly
With less radiation
On more obese patients (weight limit 531 lbs)

44. Solid State SPECT Imaging: Low Dose
Recent data shows that an excellent quality scan could be accomplished with 5 mCi of Technetium.
This would provide about 1.6 mSv of radiation per scan

45. Stress First/Only 60-70% nuclear studies normal
If stress images are normal, rest images are not clinically valuable
In lower risk patients, we could do stress imaging and only if abnormal bring back for rest

46. Radiation Exposure Normal BMI
Procedure
Radiation Exposure
Dual Isotope Imaging traditional SPECT
24mSv
Same Isotope (Tc-Tc) Imaging/ traditional SPECT
12mSV
Same Isotope (Tc-Tc) Imaging / D-SPECT
4 mSv
Stress Only (Tc) / D-SPECT
1 mSv

47. Questions
Matthew Schumaecker
Blackberry: