Stress TestingRajiv Perinbasekar

Stress Testing• Electrocardiographic (ECG) stress testing • Standard

• Echocardiographic (echo) stress testing• Pharmacologic Stress Testing• Nuclear Imaging Studies

ECG Stress Testing• The test is used to • Diagnose ischemic heart disease (most commonly)

• Discover any limitations in exercise and detect typical ECG signs of myocardial ischemia and establish their relationship w/ chest discomfort

• Estimation of risk and prognosis of IHD• Diagnose arrhythmias• Assess efficacy of current treatment regiment/guide treatment of

heart disorder (IHD, arrhythmias, valvular heart disease, etc.)• Record 12-lead ECG before, during, and after exercise on a

treadmill or stationary bicycle

Stress Testing Algorithm

ECG Stress Testing (2)• Consists of standardized incremental increases in external workload

while symptoms, ECG, and arm blood pressure are monitored• Stop test w/ evidence of:• Chest discomfort• Severe shortness of breath• Dizziness• Severe fatigue• ST segment depression > 0.2 mV (2mm)• Fall in systolic BP > 10 mm Hg• Development of a ventricular tachyarrhythmia• Or when reaching the maximal predicated heart rate (MHR)

• Must reach 85% of the maximal predicted heart rate (MHR) for age and sex to consider a negative test diagnostic• MHR = 220 beats/min – patient’s age

METs• Metabolic Equivalent Tasks (METs)• Physiological measure expressing the energy cost of physical

activities• Ratio of metabolic rate (energy consumption) during physical

activity to a reference metabolic rate (3.5 ml O2 kg-1 min-1)• Used as an index of intensity of physical activity• Walking a slow pace (MET = 2) requires twice the energy than an

average person consumes at rest (MET = 1)• MET = 7 (jogging, general)

ECG Stress Testing (3)• Positive test:• Typical chest discomfort is reproduced• ECG abnormalities consistent w/ ECG develop

• > 1 mm horizontal or downsloping ST segment depression

• Sensitivity (65-70%), Specificity (75-80%)• Markedly positive w/ 1 or more of the following• 1) Ischemic ECG changes develop in first 3 min of exercise or

persist 5 min after exercise stopped• 2) Magnitude of ST segment depression > 2mm• 3) Systolic BP abnormally falls during exercise• 4) High-grade ventricular arrhythmias develop• 5) Patient cannot exercise for at least 2 min b/c of

cardiopulmonary limitations

Echo Stress Testing• Justin Ngeow

Pharmacologic Stress Testing• For patients unable to exercise (knee or hip problems) • Use various agents in place of exercise including:• Dobutamine • Dipyridamole and adenosine (vasodilators)

• Coupled with nuclear imaging or echocardiography

Nuclear Imaging Studies• Standard stress test relies on ischemia-related changes, so it is

less useful in patients w/ baseline abnormalities of ST segments (LV hypertrophy)

• Also, standard stress test sometimes is inconclusive• Can use radionuclide imaging to increase sensitivity and

specificity of the exercise test

Nuclear Imaging Studies• Inject a radionuclide (technetium-99m or thallium-201 labeled

compound) intravenously at peak exercise, afterward performing imaging

• Radionuclide accumulates based on degree of perfusion• High perfusion areas appear “hot”• Low perfusion areas (regions of ischemia/infarcts) appear “cold”

• Imaging is performed at rest to differentiate between areas of transient ischemia and infarction• Transient ischemia: cold spot fills in• Infarction: cold spot is unchanged

• 80 to 90% sensitivity and 80% specificity for IHD• Cardiac PET Scans have ~90% sensitivity and ~90% specificity

References• Harrison’s Principles of Internal Medicine• Chapter 243: Ischemic Heart Disease

• Lilly• Chapter 6: Ischemic Heart Disease

Electrocardiographic (3)• Ischemic ST-segment response:• Flat or downsloping depression of the ST segment > 0.1 mV

below baseline (PR segment) and lasting longer than 0.08s