Zoll Firm Lecture Series Stress testing 2008 Zoll Firm Lecture Series

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

Zoll Firm Lecture Series Bayesian Theory 2008 Zoll Firm Lecture Series

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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