Assessment of Patients Requiring Stress Testing
Patients with suspected coronary artery disease who have normal initial cardiac biomarkers and ECG should undergo stress testing within 72 hours for low-risk patients or after 8-12 hours of observation if they remain pain-free, with exercise testing preferred over pharmacological stress whenever functional status permits. 1
Pre-Test Clinical Evaluation
Essential Clinical Assessment
Identify absolute contraindications that preclude stress testing: acute coronary syndrome, decompensated heart failure, severe/symptomatic aortic stenosis, uncontrolled arrhythmias (including second- or third-degree AV block without pacemaker, sinus node disease), severe systemic arterial hypertension, acute aortic dissection, pericarditis/myocarditis, acute pulmonary embolism, severe pulmonary hypertension, and known/suspected bronchoconstrictive or bronchospastic lung disease 1, 2
Assess functional capacity to determine exercise capability: patients with ≥4 METs functional capacity generally do not require further cardiac evaluation if they have low perioperative risk 1, 3
Evaluate resting ECG abnormalities: patients with complete left bundle branch block, pre-excitation syndrome, left ventricular hypertrophy, digoxin therapy, >1 mm resting ST-segment depression, or electronically paced ventricular rhythm should undergo stress imaging rather than standard exercise ECG 4
Risk Stratification Framework
Determine urgency of clinical situation: emergency cases proceed immediately with appropriate monitoring; urgent cases require assessment for acute coronary syndrome before proceeding 3
Calculate perioperative risk if applicable: patients with <1% risk of major adverse cardiac events require no further testing 1, 3
Identify high-risk features requiring hospitalization rather than outpatient stress testing: ongoing chest pain, hemodynamic instability, or high-risk ECG changes 4
Selection of Stress Testing Modality
Exercise vs. Pharmacological Stress
Exercise stress testing is the preferred initial test for patients with normal or near-normal resting ECG who are capable of adequate exercise, as it provides functional capacity assessment and is less expensive than imaging modalities 4, 1, 5, 6
Pharmacological stress testing should be used for patients unable to exercise adequately due to orthopedic limitations, peripheral vascular disease, deconditioning, or other comorbidities 1, 3, 5
Adenosine or dipyridamole are the preferred pharmacological agents for vasodilator stress, with adenosine administered at 0.14 mg/kg/min infused over six minutes 2, 7
Dobutamine stress is an alternative pharmacological option, starting at 0.5-1.0 μg/kg/min and titrating up to 2-20 μg/kg/min (occasionally up to 40 μg/kg/min) based on patient response 8, 7
Standard Exercise ECG vs. Stress Imaging
Standard exercise ECG is appropriate for patients with normal resting ECG not taking digoxin, as it is almost as accurate as imaging modalities for identifying left main or three-vessel disease in this population 5
Stress imaging (nuclear perfusion or echocardiography) is indicated for patients with prior revascularization, uninterpretable ECG, inability to exercise adequately, abnormal resting ECG, or when localization and characterization of ischemia extent is needed 4, 1, 5, 6
Nuclear myocardial perfusion imaging has been well validated for detecting left main and three-vessel disease, assessing prognosis, and detecting ischemia in patients with abnormal left ventricular function at rest 5, 7
Stress echocardiography is less expensive than nuclear imaging and provides ancillary information about valvular function and wall motion, though it has not been as extensively validated for severe coronary disease assessment 5
Specific Clinical Scenarios
Post-Myocardial Infarction
Submaximal stress testing at 4-6 days post-discharge is recommended for prognostic assessment, activity prescription, and evaluation of medical therapy 4
Symptom-limited stress testing at 14-21 days if predischarge testing was not performed, or at 3-6 weeks if early testing was submaximal 4
Vasodilating agents are particularly advantageous in post-MI patients, allowing testing as early as 2 days after the event 7
Preoperative Evaluation
Stress testing should only be ordered when patients have elevated MACE risk (≥1%), poor functional capacity (<4 METs), AND when results will actually change perioperative management 3
Do not order stress testing for low-risk surgery regardless of patient risk factors, patients with excellent functional capacity (≥4 METs) even with multiple risk factors, or asymptomatic patients after coronary revascularization with good exercise capacity (≥7 METs) 3
Diabetes and Asymptomatic Patients
Evaluation of asymptomatic persons with diabetes who plan to start vigorous exercise is a Class IIa indication for stress testing 4
Do not routinely order stress tests in asymptomatic low-risk patients without risk factors, as this represents inappropriate testing 1
Special Populations
Young patients (<40 years) without known cardiac disease or abnormal ECG have extremely low 30-day cardiovascular event rates (0.4%), and routine stress testing in this population should be reconsidered 9
Older patients (>40 years for men, >50 years for women) planning vigorous exercise or in occupations affecting public safety represent Class IIb indications for stress testing 4
Preparation and Safety Measures
Pre-Test Requirements
Ensure appropriate resuscitative equipment and personnel are immediately available, as fatal cardiac events including cardiac arrest, ventricular arrhythmias, and myocardial infarction have occurred during stress testing 2
Verify medication history: methylxanthines (caffeine, aminophylline, theophylline) interfere with adenosine activity and should be withheld; dipyridamole increases adenosine activity 2
Screen for contraindications to pharmacological agents: adenosine is contraindicated in patients with bronchoconstrictive lung disease, second- or third-degree AV block without pacemaker, sinus node disease, and known hypersensitivity 2
Monitoring During Testing
Continuous ECG monitoring with assessment for ST-segment changes, arrhythmias, and heart rate response 4
Blood pressure monitoring at regular intervals to detect hypotension (requiring discontinuation if persistent or symptomatic) or severe hypertension (≥250 mmHg systolic or ≥125 mmHg diastolic) 4, 2
Clinical assessment for chest discomfort, dyspnea, dizziness, or other symptoms suggesting inadequate cardiac output 4
Interpretation and Risk Stratification
High-Risk Findings
- Exercise EF ≤0.50 or rest EF ≤0.35, stress-induced moderate perfusion defect with LV dilation or increased lung uptake, or echocardiographic wall-motion abnormality involving >2 segments at low-dose dobutamine indicate high risk 1
Intermediate-Risk Findings
- Mild/moderate resting LV dysfunction, intermediate-risk treadmill score, stress-induced moderate perfusion defect without LV dilation, or limited stress echocardiographic ischemia 1
Low-Risk Findings
Low-risk treadmill score, normal or small myocardial perfusion defect, and normal stress echocardiographic wall motion indicate favorable prognosis 1
Normal perfusion imaging has a high negative predictive value with <1% annual incidence of cardiac events, effectively ruling out obstructive coronary disease 10, 7, 6
Common Pitfalls to Avoid
Do not delay urgent surgery (such as hip fractures) for stress testing, as delays increase morbidity and mortality 3
Avoid stress testing in patients with moderate-to-severe aortic stenosis due to risk of complications 3
Do not fail to consider pharmacologic stress when patients cannot achieve adequate exercise levels, as this leads to inaccurate results 1
Recognize that false positive rates for stress ECG are approximately 10-30%, particularly in women, and normal perfusion imaging definitively excludes obstructive disease 10