What is the protocol for administering a Bruce protocol exercise test to an adult with suspected coronary artery disease and a history of cardiovascular risk factors such as hypertension, hyperlipidemia, or smoking?

Bruce Protocol Exercise Testing in Adults with Suspected CAD and Cardiovascular Risk Factors

For adults with suspected coronary artery disease and cardiovascular risk factors (hypertension, hyperlipidemia, or smoking), the standard Bruce protocol should be used for exercise stress testing if the patient can tolerate moderate physical functioning, with continuous 12-lead ECG monitoring throughout exercise and for at least 6 minutes into recovery, measuring blood pressure at each stage. 1

Patient Selection and Pre-Test Considerations

Who requires exercise testing:

• Men >40-45 years old OR women >50-55 years old (or postmenopausal) with ≥1 coronary risk factor should undergo exercise testing before vigorous competitive activities 1, 2
• Risk factors include: total cholesterol >200 mg/dL, LDL >130 mg/dL, HDL <35 mg/dL (men) or <45 mg/dL (women), systolic BP >140 mmHg or diastolic >90 mmHg, current/recent smoking, diabetes mellitus, or family history of MI/sudden death in first-degree relative <60 years old 1
• Any patient with symptoms suggestive of coronary disease regardless of age 1
• All patients ≥65 years old, even without risk factors or symptoms 1

Contraindications to standard Bruce protocol:

• Do NOT use if patient has: Wolff-Parkinson-White syndrome, electronically paced ventricular rhythm, >1 mm ST depression at rest, or complete left bundle-branch block 1
• Do NOT use if patient is taking digoxin 1
• Do NOT use if patient cannot perform moderate physical functioning or has disabling comorbidity 2

Protocol Selection: Standard vs Modified Bruce

Use Standard Bruce Protocol when: 3

• Patient can tolerate initial workload of 3.2-4.7 METs
• No disabling comorbidities present
• Patient reports ability to perform moderate physical functioning

Switch to Modified Bruce Protocol when: 3

• Patient has limitations in activities of daily living
• Elderly, deconditioned, or marked obesity present
• Peripheral artery disease, COPD, or orthopedic limitations exist
• Patient cannot tolerate high initial workload of standard Bruce

The Modified Bruce provides smaller 1-MET incremental stages compared to standard Bruce, which has large interstage workload jumps that can force premature termination in compromised patients 3

Test Administration Protocol

Equipment setup and monitoring:

• Use continuous 12-lead ECG monitoring with multiple-lead waveform display throughout exercise and ≥6 minutes into recovery 1
• Measure blood pressure at every stage minimum, more frequently in high-risk patients 1
• Question patient about symptoms periodically during and after exercise 1

Test execution:

• Precede with 3 minutes baseline and 3 minutes warm-up measurements 1
• Follow with 5-10 minutes recovery measurements 1
• Minimize handrail support, as grasping rails reduces actual workload and creates significant discrepancy between estimated and true oxygen consumption 3
• Target test duration of 8-12 minutes for optimal accuracy 3

Termination criteria - continue to symptom-limited maximal exertion: 3

• Do NOT terminate at 85% age-predicted maximal heart rate, as there is high variability among subjects 3
• Goal is maximal effort regardless of protocol chosen 3

Interpretation of Results

Positive test indicating high risk (requires further evaluation): 1

• ≥1 mm (0.10 mV) horizontal or downsloping ST-segment depression for >80 ms during or in first minutes of recovery
• Hypotensive blood pressure response to maximal exercise relative to baseline
• Complex ventricular ectopy
• Reduced exercise capacity

High-risk features associated with severe CAD and poor prognosis: 1

• Greater degree of ST-segment depression
• Exercise duration <6 minutes on Bruce protocol 1
• Failure to attain ≥90% age-predicted maximal heart rate 1
• Chest pain during maximal exertion 1
• ST changes persisting >5 minutes after exercise 4
• Ischemic changes developing before 6 minutes of exercise 4
• Ischemic changes at heart rate <150 beats/min 4

Prognostic significance:

• Asymptomatic men >40 years with >1 risk factor and ≥2 abnormal exercise features showed 30-fold increment in 5-year cardiac risk 1
• Positive exercise ECG in asymptomatic populations with risk factors increases future coronary events by 15 times in men and 5 times in women 1, 2
• Patients completing 9 minutes of Bruce protocol have extremely low subsequent cardiac risk 3

Critical Pitfalls to Avoid

Common errors that compromise test validity:

• Allowing excessive handrail support invalidates workload estimates 3
• Using 85% age-predicted heart rate as termination criterion misses true maximal effort 3
• Selecting wrong protocol (standard Bruce for deconditioned patient) causes premature termination and indeterminate results 3
• Failure to achieve adequate exercise with negative ECG results in indeterminate estimation of CAD 3

When standard exercise ECG is inadequate:

• If test is indeterminate due to inadequate exercise level, consider pharmacological stress imaging instead 3
• For patients with baseline ECG abnormalities or taking digoxin who can exercise, use exercise perfusion imaging or exercise echocardiography as initial test 1

Post-Test Management

Negative test does NOT rule out coronary artery disease - maximal graded exercise testing serves only as preliminary evaluation to estimate likelihood that CAD is present 1

Positive test necessitates further diagnostic evaluation to establish more definitively the presence and anatomic severity of atherosclerotic arterial narrowing 1

Risk stratification using Duke Treadmill Score: 1

• Duke score = exercise time (minutes) - (5 × ST deviation in mm) - 4 if angina occurs - 8 if angina is reason for stopping
• Low risk (score ≥5): 4-year survival 99%, annual mortality 0.25%
• High risk (score ≤-10): 4-year survival 79%, annual mortality 5%