From the Guidelines
The combination of right bundle branch block (RBBB) with first-degree atrioventricular block (FD-AVB) and alternating left anterior hemiblock (LAHB) and left posterior hemiblock (LPHB) is indeed concerning for progression to complete heart block (CHB) and warrants prompt cardiology consultation and consideration for pacemaker implantation. This patient requires close monitoring, either in an inpatient setting or with ambulatory monitoring if clinically stable. Medications that slow AV conduction (beta-blockers, calcium channel blockers, digoxin) should be discontinued or reduced if possible, as they may exacerbate the condition 1. The patient should be educated about symptoms of worsening heart block, including syncope, pre-syncope, severe fatigue, or shortness of breath, which warrant immediate medical attention.
Rationale for Recommendation
The recommendation is based on the conduction system anatomy, where this combination represents disease affecting multiple fascicles of the cardiac conduction system. With RBBB already present, alternating LAHB and LPHB indicates intermittent disease in both fascicles of the left bundle. Since normal conduction requires at least one intact fascicle, this electrical pattern suggests the patient is at high risk for developing complete heart block, which can cause symptomatic bradycardia or even cardiac arrest 1.
Clinical Implications
According to the 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay, patients with alternating bundle branch block should receive a pacemaker because of the high risk of developing complete atrioventricular block 1. Additionally, the guideline recommends permanent pacing for patients with syncope and HV intervals ≥70 ms or frank infranodal block 1.
Key Considerations
- The patient's clinical stability and symptoms should guide the decision for inpatient versus outpatient monitoring.
- Medications that may worsen AV conduction should be carefully managed.
- Patient education on recognizing symptoms of worsening heart block is crucial for early intervention.
- The decision for pacemaker implantation should be made in consultation with a cardiologist, considering the patient's overall clinical context and risk factors for progression to complete heart block 1.
From the Research
Combination of Background RBBB/FD-AVB with Alternating LAHB/LPHB
- The combination of background RBBB/FD-AVB with alternating LAHB/LPHB is concerning for the potential of complete heart block (CHB) 2, 3.
- CHB is a medical emergency that can be fatal if not urgently treated, and it is often associated with conditions such as acute myocardial infarction 3.
- The presence of certain conduction disturbances, including left bundle branch block, can increase the risk of developing CHB 4, 5.
Risk Factors for Complete Heart Block
- Female gender, bolus injection of ethanol, injecting more than one septal artery, presence of left bundle branch block, and first-degree AV block are independent predictors of CHB after nonsurgical septal reduction therapy 4.
- Patients with ischemic CHB are younger and have a lower ejection fraction, but are less likely to receive a pacemaker compared to non-ischemic CHB patients 6.
- History of coronary artery disease is more common in patients with ischemic CHB compared to non-ischemic CHB patients 6.
Clinical Characteristics and Outcomes
- Patients with non-ischemic CHB are more likely to receive a permanent pacemaker compared to ischemic CHB patients 6.
- There is no statistically significant difference in terms of gender, diabetes, hypertension, thyroid dysfunction, chronic kidney disease, nodal blocking agents, electrolyte abnormalities, or smoking status between ischemic and non-ischemic CHB patients 6.
- Further studies are required to understand the long-term mortality outcomes of patients with CHB 6.