1. Cardiac Stress Testing: Who, when, why, and how
Ross S. Pacini, M.D.

2. Objectives
Understand basic indications and contraindications to stress testing
Understand the differences between types of stress tests and know which one to order
Learn about some of the newer data on stress testing, especially in regards to “screening” stress tests

3. Background
ETT has been around for a long time; Dr. Bruce originally published his protocol in 1963
Nuclear SPECT imaging was developed in the 1980’s
Stress echocardiography developed concurrently but became more popular in the 1990’s

4. Background
Indications and implications have changed dramatically with improvements in medical therapy
ASA was novel in the 1980’s; first statin was marketed in 1987
Key Point: Stress testing is not designed to detect any CAD, but to detect obstrucive CAD
>50% LM; >70% epicardial artery

5. Background
Fundamental to understanding stress testing or any diagnostic test is this man’s work.

6. Bayes’ Theorem
Bayes work in the 1700’s is what drives our stress testing model today
His theory basically says that the post-test probability of an event is driven dramatically by the pre-test probability
The usefulness of a test is in the intermediate pre-test probability

7. An example
A new blood test can determine the likelihood that a person will produce intelligent children
Who needs the test?
A MENSA scholar with a known IQ of 160
An accountant with a college degree but some dyslexia
An Oakland Raiders fan who sits in the Black Hole (my example of an incredibly dumb person )

8. In the same way also… Who needs a stress test?
55 y/o male with DM, HTN, HL, 50 pack-year smoking hx, and typical angina
62 y/o female with right-sided chest pain q 2-3 days that is brought on by exertion
25 y/o male with a single episode of chest pain after eating a spicy meal?

9. Interpretation of results
1st pt: Pre-test is 95%; with a positive test, it is 99%. With a negative test, it is 90%
3rd pt: Pre-test is 3%; with a positive test, it is 10%; with a negative test, it is 1%
2nd pt: Pre-test is 45%; with a positive test, it is 87%; with a negative test, it is 10%

10. So…
Key Point: The determination of your pre-test probability is the key to deciding who needs a stress test.

11. Determining Risk
Exercise stress test guidelines* tell us to quantify angina using 3 characteristics
Substernal location of chest pain
Provoked by exertion or emotional stress
Relieved by rest or NTG
Typical/Definite angina: 3/3
Atypical/Probable: 2/3
Nonanginal Chest Pain: 1/3
Asymptomatic: 0/3
* Gibbons, et al. Journal American Collge of Cardiology, 2002.

12. Determining Risk
-Note that testing is appropriate for intermediate risk
-Also note that asymptomtatic folks are all LOW risk

13. More simply
You all are obviously very capable of determining general cardiac risk, but if you need help, check Framingham risk score
<10% is low risk
10-20% is intermediate
>20% is high-risk
Very low risk, reassure; very high risk, call me! Stress those in between.

14. Once you’ve decided to stress
Each stress test can be broken down into a stress component and an “imaging” component
Stress component include exercise (preferred), dobutamine, Persantine (dipyridamole), adenosine, Lexiscan (regadenoson), and pacing.
“Imaging” components include EKG (first line), echo, and nuclear.

15. Stress Component Exercise is preferred method of stress
Get physiologic data including BP, heart rate recovery, arrythmia evaluation, etc
Don’t exercise pt’s who can’t exercise 
Those with significant leg or back issues
Those who are unsteady
Those who can’t reach 85% of MPHR
There are protocols other than Bruce that can be considered

16. Stress Component
Dipy, Adenosine, and Regadenoson are all vasodilator stress agents
Vasodilate coronaries creating a steal phenomenon in stenosed vessels
Most important contraindications are severe reactive airway disease and serious bradyarrhythmias/AV conduction defects
Caffeine interferes with effects; pt must have at least 12 hours (24 preferred) without caffeine

17. Stress Component
Dobutamine is a beta-agonist, causing elevated heart rate and contractility
Most important contraindication is the presence of serious ventricular arrythmias
B-blockers will interfere with effect, so should be held

18. Stress component
It is possible to stress using atrial or esophogeal pacing
Obviously, not done routinely; I’ve done it once, and I did it incorrectly 

19. Imaging Component
EKG is first-line for those who have an interpretable EKG
LBBB
WPW
Dig Effect
LVH
Paced rhythm
>1 mm ST depression on resting ECG

20. Imaging component Most ECG’s are interpretable
RBBB
Minor ST-T wave changes
Occasional PVC’s
Caveat: Location of ST depression does not correlate with area of ischemia

21. Imaging Component
Stress ECG is also very useful for determining functional capacity and efficacy of therapy
We can evaluate more than just the ECG

22. Imaging Component
Echocardiography looks at several views of all walls of the LV and compares them at rest and stress, looking for hypokinesis of affected wall
Requires good echo windows
Not obese
No bad COPD

23. Imaging component
Pt must be able to transfer quickly after exercise (time-dependent study)
Important caveat: ordering a stress echo does not mean that valves or other structures will be evaluated; we only look at 4 basic views of LV cavity, so if need other evaluation, please order a standard echo.

24. Imaging Component
Nuclear perfusion imaging evaluates blood flow to various walls, comparing rest and stress
Probably the most versatile test, though obesity and bowel interference can be a problem
Caveat: long test (pt’s should plan for 2-3 hours)

27. Putting it together
Need to pick both a stress and an imaging component that fits your patient
Vasodilators OK for either nucs or echo, but most often used with nucs
Dobutamine can be used with either echo or nucs
Again, exercise is preferred modality

28. Putting it together
For most patients, a standard exercise treadmill test is first line and preferred
Pt’s who can exercise and have interpretable ECG’s
Use imaging for those who cannot exercise, have uninterpretable ECG, or have non-diagnostic or suspicious ETT

29. What about accuracy? ETT: Sens=68%; Spec=77%
Exercise Echo1: Sens=88%; Spec=79%
Dobs Echo1: Sens=81%; Spec=80%
Exercise Nuc2: Sens=87%; Spec=73%
Vasodilator Nuc2; Sens=89%; Spec=75%
1: Heart January; 89(1): 113–118
2: Circulation. 2003; 108:

30. My personal bias (No evidence)
ETT is first line; if it correlates with my suspicion, I’m done; if not, I pursue imaging
If I want the test to be positive, I will pursue a nuc (probably overcalls)
If I want the test to be negative, I will pursue a stress echo (probably undercalls)

31. What about cost?
Obviously, hospitals charge much more than this, but here are Medicare reimbursements* for each test:
ETT: $89
Stress Echo: $208 + cost of stress agent
Nuc: $503 + cost of stress agent
Most cost effective to start with ETT *

32. Special Considerations
Yes, women have a higher false positive ETT rate; guidelines still say it is first line.
B-blockers, CCB’s: Generally, if trying to diagnose CAD, I recommend holding. If trying to evaluate success of therapy, I recommend continuing

33. Special Considerations
In pt’s with a LBBB, preferred test is a vasodilator nuclear scan
In pt’s with previous CAD, some sort of imaging test is preferred (ie, not just a standard treadmill).

34. Contraindications
Almost nothing is absolute, but two key areas to avoid/ask cardiology:
Severe outflow tract obstruction: HCM, Aortic Stenosis (can be done, but must be done very carefully)
Key Point: Unstable Coronary Symptoms. These people can die on the treadmill

35. Screening Stress Tests
Remember what I said in the beginning; a stress test is there to detect hemodynamically significant CAD, not just any CAD
As a general rule, you should approach asymptomatic patients with standard risk stratification using Framingham Risk Score and family history; most of the time, a stress test is not needed

37. Asymptomatic Adults
Recently published guidelines* give excellent guidance, and I will just quote them:
An exercise ECG may be considered for cardiovascular risk assessment in intermediate-risk asymptomatic adults (including sedentary adults considering starting a vigorous exercise program), particularly when attention is paid to non-ECG markers such as exercise capacity. (Class IIb, LOE B)
*J Am Coll Cardiol. 2010;56(25):e50-e103

38. Asymptomatic Adults
Stress echocardiography is not indicated for cardiovascular risk assessment in low- or intermediate-risk asymptomatic adults. (Exercise or pharmacologic stress echocardiography is primarily used for its role in advanced cardiac evaluation of symptoms suspected of representing CHD and/or estimation of prognosis in patients with known coronary artery disease or the assessment of patients with known or suspected valvular heart disease). Class III, LOE C

39. Asymptomatic Adults
Stress MPI may be considered for advanced cardiovascular risk assessment in asymptomatic adults with diabetes or asymptomatic adults with a strong family history of CHD or when previous risk assessment testing suggests high risk of CHD, such as a CAC score of 400 or greater (Class IIb, LOE C)

40. Asymptomatic Adults
Stress MPI is not indicated for cardiovascular risk assessment in low- or intermediate-risk asymptomatic adults (Exercise or pharmacologic stress MPI is primarily used and studied for its role in advanced cardiac evaluation of symptoms suspected of representing CHD and/or estimation of prognosis in patients with known CAD). Class III, LOE C

41. What about diabetics?
In 2009, we got the DIAD trial* (Detection of Ischemia in Asymptomatic Diabetics)
Enrolled pt’s y/o with DM dx’d after age 30 and no h/o DKA or CAD
Important exclusion criteria: h/o angina, stress test or heart cath in last 3 years, abnormal EKG, or other indication for stress testing
*JAMA. 2009;301(15):

42. DIAD trial
A total of 1,123 patients were eventually randomized: 50% to usual care; 50% to receive an adenosine MPI (nuclear) scan.
Primary endpoint was a composite of cardiac death and non-fatal MI.
Patients were followed for a median of 5 years

43. DIAD trial
Overall event rate was 2.9% giving an average event rate of 0.6%/yr.
Total events were 32: 15 in the screening group and 17 in the non-screening group [HR 0.88 ( ), p=0.73]

44. DIAD trial
Interestingly, event rate in those with normal or only small defects was 2%, while in those with medium or large defects, it was 12.1%.
In other words, NPV of normal MPI was 98%; PPV for all positive MPI was 6%; for medium or large defects, it was 12%.

45. DIAD trial
Conclusion of authors was that asymptomatic diabetic patients do not benefit from screening stress tests
A few notable caveats
Very low event rate (0.6%)
Probably low-risk patients
Significant amount of long-term crossover
Excellent medical control of risk factors

46. DIAD trial The key points here for me are twofold:
1. Risk factor modification is the key, not stress testing
2. Risk factor modification works! (ie, not everyone needs a stent…but that’s a separate talk)

47. What about Pre-Op Patients?
Pre-operative evaluation for non-cardiac surgery is a whole separate talk in itself
An evolving field, but recent guidelines* are pretty clear on this point: most patients do not need a stress test prior to surgery
*J Am Coll Cardiol 2009;54

48. Pre-op evaluation
To the best of my knowledge, no recent trial has shown any benefit of pre-operative stress testing or revascularization
There are no class I recommendations for pre-operative stress testing; the best the guidelines will give you is a IIa recommendation for pt’s with 3 risk factors who cannot do 4 METs and are undergoing vascular surgery…do you see a lot of those patients? 

49. It’s positive…now what?
First rule is, don’t panic (haven’t seen this yet here in Grand Junction)
Second, treat those patients like you would any CAD patient
Start ASA
Check Lipids and treat to LDL <100 (<70)
Control BP
Separate out stable from unstable symptoms to the best of your ability

50. It’s positive…now what?
Most patients probably deserve a cath, but not all need it and some aren’t candidates (multiple comorbidities, etc)
Now is a good time to consult cardiology

51. Local Resources
One member of Western Slope Cardiology is at CH 8-11 M-F
Offer ETT, Nucs, and now stress echos
Sit in office outside RT; available for questions, consults, guidance
St. Mary’s offers all tests
Western Slope Cardiology Diagnostic Center
ETT, Exercise Echo, all Nucs

52. Contact information
Main office line is for both scheduling stress tests and to speak to any cardiologist
Again, cardiologist on site at CH from 8-11 each weekday
We are more than happy to help you choose the proper test

53. Key Points Stress tests aim to detect obstructive CAD
Determining pre-test probability is fundamental to deciding who to stress
A standard exercise treadmill test is first line for most patients
“Screening” stress tests should be rare events (? Pilots, very high risk DM, very high risk surgery)

54. Questions…or complaints?