From the Guidelines
Yes, someone can have left bundle branch block (LBBB) intermittently, as stated in the 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1.
Intermittent LBBB Characteristics
Intermittent LBBB occurs when the conduction abnormality appears and disappears on different ECG recordings. This condition is often rate-dependent, meaning it may appear when the heart rate exceeds a certain threshold (typically above 100-120 beats per minute) and disappear when the heart rate slows down. Some key points to consider:
- Intermittent LBBB can be triggered by exercise, stress, electrolyte abnormalities, or certain medications.
- It may also occur spontaneously without any identifiable trigger.
- The clinical significance of intermittent LBBB varies depending on the underlying cause and associated symptoms.
Clinical Significance and Monitoring
For patients with intermittent LBBB, monitoring is important, especially if symptoms like dizziness, shortness of breath, or chest pain occur during episodes. Some monitoring options include:
- A 24-hour Holter monitor or event recorder may be used to capture these intermittent episodes.
- In some cases, intermittent LBBB may progress to permanent LBBB over time, which could indicate worsening of the underlying cardiac conduction system disease, as noted in the European Heart Journal study 1.
Evaluation and Management
According to the 2018 ACC/AHA/HRS guideline, in patients with newly detected LBBB, a transthoracic echocardiogram to exclude structural heart disease is recommended 1. Additionally, ambulatory electrocardiographic monitoring is useful in symptomatic patients with conduction system disease, in whom atrioventricular block is suspected 1.
From the Research
Intermittent Left Bundle Branch Block (LBBB)
- Intermittent LBBB is a condition where the left bundle branch block pattern appears on an electrocardiogram (ECG) intermittently, rather than continuously 2, 3, 4.
- This condition can mimic high-grade stenosis of the left anterior descending coronary artery, leading to false-positive ECG changes 2.
- Studies have shown that intermittent LBBB can occur in patients without substantial coronary artery disease, and may be caused by other factors such as cardiac memory or conduction system abnormalities 2, 3, 4.
Mechanism and Characteristics
- The mechanism of intermittent LBBB is not fully understood, but it is thought to involve abnormalities in the conduction system of the heart 3.
- Intermittent LBBB can be characterized by ECG changes such as ST- and T-wave changes during normal ventricular conduction, which can mimic anterior ischemia due to high-grade stenosis 2.
- Echocardiography can also be used to diagnose LBBB, and strict criteria have been established for diagnosing LBBB by echocardiography 5.
Clinical Significance
- Intermittent LBBB can have significant clinical implications, including the potential for misdiagnosis of coronary artery disease 2.
- However, intermittent LBBB can also be a benign condition, and may not always be associated with underlying cardiac disease 4.
- Further research is needed to fully understand the clinical significance and implications of intermittent LBBB 6.