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Toronto Notes 2019 Approach to ECGs Stress Testing
EXERCISE TESTING
• description:cardiovascularstresstestthatusestreadmillorbicycleexercisewithelectrocardiographic and blood pressure monitoring
• indications
■ patientswithintermediate(10-90%)pretestprobabilityofCADbasedonage,gender,andsymptoms ■ ST depression <1 mm at rest, no left bundle branch block, no digoxin or estrogen use
■ exercise test results stratify patients into risk groups
1. low risk patients can be treated medically without invasive testing
2. intermediate risk patients may need additional testing in the form of exercise imaging studies or
cardiac catheterization
3. high risk patients should be referred for cardiac catheterization
• contraindications
■ acute myocardial infarction (within 2 days)
■ unstable angina pectoris
■ uncontrolled arrhythmias causing symptoms of hemodynamic compromise
■ symptomatic severe valvular stenosis
■ uncontrolled symptomatic heart failure
■ active endocarditis or acute myocarditis or pericarditis
■ acute aortic dissection
■ acute pulmonary or systemic embolism
■ acute non-cardiac disorders that may affect exercise performance or may be aggravated by exercise ■ termination of exercise testing
◆ patient’s desire to stop
◆ drop in systolic blood pressure of >10 mmHg from baseline despite an increase in workload,
when accompanied by other evidence of ischemia
◆ moderate to severe angina
◆ ST elevation (>1 mm) in leads without diagnostic Q-waves (other than V1 or aVR)
◆ increasing nervous system symptoms (e.g. ataxia, dizziness, or near syncope)
◆ signs of poor perfusion (cyanosis or pallor)
◆ technical difficulties in monitoring ECG or systolic blood pressure ◆ sustained ventricular tachycardia
• risks:death,myocardialinfarction,arrhythmia,hemodynamicinstability,andorthopedicinjury(<1- 5/10,000 supervised tests)
NUCLEAR CARDIOLOGY
• description
■ myocardial perfusion imaging (MPI) with ECG-gated single photon emission computed
tomography (SPECT), using radiolabelled tracer
■ evaluates myocardial viability, detects ischemia, and assesses perfusion and LV function
simultaneously
■ predicts the likelihood of further cardiac event rates independent of the patient’s history,
examination, resting ECG, and stress ECG
■ often denoted as MIBI scan with reference to radiolabelled tracer (sestamibi)
■ stress with either treadmill or IV vasodilator stress (dipyridamole, adenosine, regadenoson)
■ images of the heart obtained during stress and at rest 3-4 h later
■ tracers
◆ Thallium-201 (201Tl, a K+ analogue)
◆ Technetium-99 (99Tc)-labeled tracer (sestamibi/Cardiolite® or hexamibi/Myoview®) • indications
■ exercise MPI
◆ when ECG cannot be interpreted appropriately
◆ intermediate pre-test probability with normal/equivocal exercise ECG ◆ in patients with previous imaging whose symptoms have changed
◆ to diagnose ischemia
■ dipyridamole/adenosine MPI
■ to diagnose CAD in possible ACS patients with non-diagnostic ECG and negative serum
biomarkers
■ when ECG is cannot be interpreted appropriately due to LBBB or V-paced rhythm among patients
unable to exercise, with the same indications as exercise MPI • contraindications
■ contraindications to exercise testing
■ vasodilators (i.e. adenosine, regadenoson, and dipyridamole) are contraindicated in patients with
hypotension, sick sinus syndrome, high-degree AV block (in the absence of backup pacemaker
capability), and reactive airways disease ■ pregnancy
• risks: radiation exposure
STRESS ECHOCARDIOGRAPHY
• seeEchocardiography,C12
Cardiology and Cardiac Surgery C13
Most Commonly Used Treadmill Stress Test Protocols
• The Bruce Protocol: 7 stage test with each
stage lasting 3 min. With each successive stage, the treadmill increases in both speed (2.7 km/h to 9.6 km/h) and grade (10% with a 2% increase per stage up to 22%)
• The Modified Bruce, Modified Naughton Protocol: for older individuals or those with limited exercise capacity
Important Contraindications to Exercise Testing
• Acute MI, aortic dissection, pericarditis,
myocarditis, PE
• Severe AS, arterial HTN
• Inability to exercise adequately
Important Prognostic Factor
Duke Treadmill Score (DTS) Weighted Index Score
• Treadmill exercise time using standard
Bruce protocol
• Maximum net ST segment deviation
(depression or elevation)
• Exercise-induced angina provides
diagnostic and prognostic information
(such as 1 yr mortality)
DTS = exercise time – (5 x MaxST) –
(4 x angina index)
Angina index: 0 (no angina), 1 (angina but not exercise-limiting), 2 (exercise-limiting angina) DTS ≥5: 0.25% 1 yr mortality
DTS 4 to -10: 1.25% 1 yr mortality
DTS ≤ -11: 5.25% 1 yr mortality
Ann Intern Med 1987;106:793-800
Patients with normal imaging (nuclear perfusion or stress echo) studies at peak stress have a <1%/yr incidence of death or nonfatal MI and are thus often spared further invasive evaluation