1. Zoll Firm Lecture Series
Stress testing
2008
Zoll Firm Lecture Series

2. Zoll Firm Lecture Series
Stress tests
Performed on patients with intermediate pretest probability of coronary artery disease.
In patients with low pre-test probability, a stress tests does not help to further clarify diagnosis or prognosis.
In patients with very high pre-test probability of CAD, a cardiac catheterization provides definitive information about coronary anatomy and the opportunity for intervention.
Provides diagnosis but more importantly prognosis.
2008
Zoll Firm Lecture Series

3. Zoll Firm Lecture Series
Bayesian Theory
2008
Zoll Firm Lecture Series

4. Zoll Firm Lecture Series
Source of “stress”
Exercise
Pharmacologic
Adenosine
Dobutamine
Pharmacologic stress tests will be addressed in another lecture.
2008
Zoll Firm Lecture Series

5. Zoll Firm Lecture Series
Detection of Ischemia
EKG
Nuclear perfusion imaging
Echocardiography
Later two methods will be addressed in another lecture.
2008
Zoll Firm Lecture Series

6. Zoll Firm Lecture Series
Exercise
Prefer method of “stress”
Reproduce symptoms in “real-life” context.
The amount of exercise one can perform provides a lot of prognostic information.
Bruce, modified Bruce (3 minutes of easy time + Bruce), Naughton/Gervino protocols.
Usually, ask the patient to exercise close to their maximal effort. Would like them to reach 85% MPHR or RPP >20,000. Stop if there are very high risk features (hemodynamic compromise, signs/symptoms of severe ischemia, serious arrythmias)
2008
Zoll Firm Lecture Series

7. Fitness strong predictor of survival
6213 men referred for exercise testing who were followed for a mean of 6.2 years., M, Froelicher, V, et al, N Engl J Med 2002; 346:793
In both subject with and without cardiovascular disease, exercise capacity strongly predicts survival (in fact, more than the presence or absence of CVD).
For each one MET increase in exercise capacity there was a 12 percent improvement in survival.
2008
Zoll Firm Lecture Series

8. Why not always exercise the patient?
Often, patients cannot exercise to the workload necessary for a diagnostic test due to arthritis, PVD, poor functional status…etc.
Sometimes useful to assess just how poor is the functional status.
Exercise stress test is contraindicated:
Within 2 days of myocardial infarction or high risk unstable angina (known ST depression…etc).
Decompensated heart failure, acute PE, known or suspected dissecting aneurysm.
Severe stenotic valvular disease relatively contraindicated.
2008
Zoll Firm Lecture Series

9. Zoll Firm Lecture Series
Hemodynamic response
With exercise, both the blood pressure and heart rate goes up.
Failure to increase the SBP >120, sustained decrease >10mmHg or decrease in BP below standing value during exercise is a high risk feature
Usually reflects LMCA, 3vd, or severe AS where cardiac output declines with stress
2008
Zoll Firm Lecture Series

10. Zoll Firm Lecture Series
Hemodynamic response
For diagnosis of CAD, would like the patient to reach 85% of maximal predicted heart rate or rate pressure product of >20,000
Maximal predicted HR (220-age)
Rate pressure product (BP x HR)
Should medicines (beta-blockers…etc.) be withheld prior to the test?
For the diagnosis of CAD, yes
For the assessment of the efficacy of medical mngt, no need to withhold drugs.
2008
Zoll Firm Lecture Series

11. Zoll Firm Lecture Series
EKG response
ST depression (0.8ms after the J point- usually read on 3 consecutive beats)
Shape (upsloping, flat, down-sloping)
Amount
Positive test considered 1mm horizontal or down-sloping depression in 2 neighboring leads.
Location does not localize ischemia.
ST elevation-
In leads with prior q waves, not a concern
In leads with no q waves- ACS, sent to cath lab, location predicts ischemia. Uncommon- 1%
2008
Zoll Firm Lecture Series

12. Zoll Firm Lecture Series
EKG response
Can also develop arrythmias-
VT can develops in setting of ischemia.
Supraventricular tachycardia
Heart block in the case of infranodal conduction disease.
The heart rhythm abnormalities can sometimes explain the patient’s symptoms.
2008
Zoll Firm Lecture Series

13. Diagnosis and prognosis
Sensitivity and specificity in patients selected for angiography is 68% and 77%, respectively
referral bias exaggerate false positives, eliminates false negatives (falsely improves sensitivity and worsens specificity)
Duke Treadmill score:
Exercise time- (5x ST deviation)- 4x treadmill angina index)
Angina index- 0= none, 1= typical angina, 2= angina reason patient stopped exercising.
2008
Zoll Firm Lecture Series

14. Zoll Firm Lecture Series
Duke Treadmill Score
Low risk- >+5
Intermediate- +4 to -10
High risk- <-11
The five year survival was
65 percent in high risk patients
90 percent in moderate risk patients
over 97 percent in low risk patients
A study with 70% men
Shaw, LJ, Peterson, ED, Shaw, LK, et al. Circulation 1998; 98:1622
2008
Zoll Firm Lecture Series

15. Some limitations of EKG
Uninterpretable in the setting of LBBB or IVCD.
Accuracy goes down in the setting of LVH or otherwise abnormal resting EKG.
Less accurate in women compared to men (more false positives)
2008
Zoll Firm Lecture Series

16. Potential complications
In general, exercise stress test is a very safe test.
1 cardiac arrest per 565,000 person/hour of exercise, about 10 fold higher in the population with CAD (still very low).
2008
Zoll Firm Lecture Series

17. How to interpret a stress test?
Look for:
Duration of exercise
High risk hemodynamic features- fall in blood pressure…etc
Symptoms
Heart rate and blood pressure response (HR 85% MPHR and RPP >20000)
EKG results- presence of ischemic changes, ectopy
Can calculate Duke treadmill score
2008
Zoll Firm Lecture Series

18. Zoll Firm Lecture Series
Case 1:
53 year old man with hyperlipidemia was referred to an exercise stress test for chest pain. He exercised 13 minutes of the Bruce protocol, developing mild chest pain at minute 11, EKG shows 1mm ST horizontal ST depression that resolved 5 minutes after recovery. What do you think of is his:
Diagnosis?
Prognosis?
2008
Zoll Firm Lecture Series

19. Zoll Firm Lecture Series
Case 2:
74 year old woman with diabetes, hypertension, and hyperlipidemia who exercised for 2 minutes of the Bruce protocol and developed severe, crushing chest pain. EKG monitoring shows 4mm downsloping ST depression and intermittent NVST. What is her:
Diagnosis?
Prognosis?
2008
Zoll Firm Lecture Series