From the Guidelines
Left anterior fascicular block (LAFB) is a cardiac conduction abnormality that typically does not require specific treatment, but patients should undergo a thorough cardiac evaluation to identify any underlying heart disease. The evaluation should include a thorough medical history, assessment of symptoms, blood tests, echocardiography, and electrocardiographic findings, as recommended by the 2024 ESC guidelines for the management of atrial fibrillation 1. Key aspects of the evaluation include:
- Identifying the presence and nature of symptoms associated with AF, as well as the clinical type of AF (paroxysmal, persistent, or permanent) 1
- Assessing the impact of AF-related symptoms before and after major changes in treatment to inform shared decision-making and guide treatment choices 1
- Using a transthoracic echocardiogram to guide treatment decisions in patients with an AF diagnosis 1
- Managing risk factors and comorbidities, such as hypertension, heart failure, diabetes mellitus, obesity, obstructive sleep apnoea, physical inactivity, and high alcohol intake, as recommended by the 2024 ESC guidelines 1 Electrocardiographic findings of LAFB include left axis deviation (typically -45° to -90°), small Q waves in leads I and aVL, and small R waves in leads II, III, and aVF. While LAFB itself is generally benign, it may be a marker for progressive conduction disease, particularly when combined with right bundle branch block, which can increase the risk of developing complete heart block, as noted in the 2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation 1. Regular cardiac follow-up is recommended, especially if there are other conduction abnormalities present or if the patient has underlying structural heart disease. The prognosis is generally determined by any associated cardiac conditions rather than by the fascicular block itself. In terms of management, the focus should be on controlling heart rate and reducing symptoms, as recommended by the 2024 ESC guidelines, using medications such as beta-blockers, diltiazem, verapamil, or digoxin 1. Overall, the management of LAFB should prioritize the identification and treatment of underlying heart disease, as well as the control of heart rate and symptoms, to improve morbidity, mortality, and quality of life.
From the Research
Left Anterior Fascicular Block (LAFB) Overview
- LAFB is a heart disease identifiable from an abnormal electrocardiogram (ECG) 2
- It has been reported that LAFB is associated with an increased risk of heart failure 2
Association with Coronary Artery Disease (CAD)
- LAFB subjects had more pathological CAD (66.3% vs 54.6%, P = 0.039) and myocardial infarction (MI) (53.3% vs 37.9%, P = 0.007) 3
- However, logistic regression showed CAD had no independent relevance with LAFB 3
Clinical Significance and Prognosis
- LAFB was an independent risk factor of all-cause death (HR = 1.552,95% CI = 1.208-1.994, P = 0.001) and cardiac death (HR = 2.287,95% CI = 1.545-3.386, P < 0.001) 3
- The major death cause of LAFB was cardiac death (46.7%), including more MI (28.3% vs 13.4%, P = 0.008) and myocarditis (4.3% vs 1.0%, P = 0.042) 3
Treatment and Management
- β-Blockers remain essential in the treatment of heart failure with reduced ejection fraction (HFrEF), but limited evidence supports their use in heart failure with midrange ejection fraction (HFmEF) or heart failure with preserved ejection fraction (HFpEF) 4
- β-Blockers should still be considered routinely following acute coronary syndrome, but there is a need for contemporary trials that re-examine this in patients without left ventricular dysfunction, as well as in patients with stable CAD 4