How do you interpret ECG (Electrocardiogram) stress test results in patients with Right Bundle Branch Block (RBBB)?

From the Guidelines

ECG stress test results in patients with Right Bundle Branch Block (RBBB) can be interpreted by focusing on specific ECG changes beyond the baseline RBBB pattern, particularly in the lateral leads. When interpreting ECG stress test results in patients with RBBB, it is essential to compare the exercise ECG to the baseline ECG, as RBBB causes a secondary ST-segment depression and T-wave inversion in leads V1-V3 that should not be confused with ischemic changes 1. Some key points to consider when interpreting ECG stress test results in patients with RBBB include:

• Focus on the lateral leads (I, aVL, V5-V6) for ischemic changes, as these are less affected by RBBB
• Exercise-induced ST depression in these leads is more specific for ischemia
• Look for additional ST depression beyond the baseline pattern, particularly if it exceeds 1 mm in the lateral leads
• The development of angina symptoms during the test significantly increases the likelihood of coronary artery disease, regardless of ECG changes
• RBBB reduces the sensitivity of stress ECG for detecting ischemia, with false negative rates up to 40% Consider adding imaging modalities like stress echocardiography, nuclear perfusion imaging, or cardiac MRI to improve diagnostic accuracy in RBBB patients 1. Also, evaluate functional capacity, heart rate response, blood pressure response, and recovery time as these provide valuable prognostic information independent of ECG changes. While the provided evidence primarily discusses Left Bundle Branch Block (LBBB), the principles of ECG interpretation can be applied to RBBB, although the specific criteria may differ 1.

From the Research

ECG Stress Test Interpretation in Patients with RBBB

• The interpretation of ECG stress test results in patients with Right Bundle Branch Block (RBBB) can be challenging due to the altered electrocardiographic patterns 2.
• Studies have shown that exercise electrocardiography and dipyridamole stress echocardiography can be used to diagnose coronary artery disease in patients with RBBB, but with varying degrees of accuracy 2.
• Dipyridamole stress echocardiography has been found to be more effective than exercise electrocardiography in diagnosing coronary artery disease in hypertensive patients with RBBB, due to its higher specificity 2.
• Dobutamine stress echocardiography can be used for prognostic stratification of patients with RBBB, with abnormal results being a strong predictor of cardiac events 3.

Specific ECG Criteria for RBBB

• Prolonged R' duration in lead V1 has been found to be an indicator of right ventricular systolic dysfunction in patients with RBBB 4.
• A V1 R' duration ≥ 100 ms has been found to be predictive of right ventricular systolic dysfunction in patients with RBBB, with a sensitivity of 39.0% and specificity of 82.9% 4.
• The presence of a QR pattern in V1 on ECG has been found to be a predictor of sudden cardiac arrest due to pulmonary embolism in patients with RBBB 5.

Limitations and Considerations

• The presence of RBBB can limit the interpretability of ECG stress test results, and alternative diagnostic methods such as stress echocardiography may be necessary 6.
• The accuracy of ECG stress test interpretation in patients with RBBB can be affected by various factors, including hypertension and the presence of other electrocardiographic abnormalities 2.