Stress Testing Rajiv 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