Diagnosis of Bundle Branch Block
Diagnosis of bundle branch block is typically made using an electrocardiogram (ECG), which records the electrical activity of the heart. A confirmed diagnosis requires identifying specific changes in the ECG pattern that show delayed conduction in one of the heart’s bundle branches.
During an ECG, the doctor looks for a widened QRS complex — greater than 120 milliseconds — along with other characteristic patterns. The exact shape of the waveform helps distinguish between:
- Right bundle branch block (RBBB): often shows an “RSR’” pattern in leads V1–V3
- Left bundle branch block (LBBB): typically shows a broad, notched QRS in leads I, aVL, V5 and V6, with absent Q waves
Once a bundle branch block is identified, doctors assess whether it’s isolated or related to a broader cardiac issue.
Additional tests may include:
- Echocardiogram to evaluate heart structure and function, particularly the pumping efficiency of the left ventricle
- Stress testing if there’s concern about coronary artery disease
- Cardiac MRI or CT scan for structural evaluation
- Holter monitoring or event recorders to track intermittent arrhythmias or unexplained symptoms
Diagnosis of Bundle Branch Block
Blood tests may be ordered to assess for causes such as infection, electrolyte imbalances, or myocardial injury (troponins).
A detailed history is essential — including questions about chest pain, exertion, breathlessness, and family history of cardiac issues.
The purpose of a diagnosis is not only to confirm the conduction delay but also to assess its clinical significance and underlying cause, which will guide further treatment or monitoring.
[Next: Treatment of Bundle Branch Block →]
