From the Guidelines
Trifascicular block workup should include a comprehensive cardiac evaluation to assess the risk of progression to complete heart block, with a focus on symptoms like syncope, presyncope, dizziness, or fatigue, and should be guided by the most recent guidelines, such as the 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1. The workup should begin with a thorough history and physical examination, and obtain a 12-lead ECG to confirm the presence of trifascicular block (right bundle branch block with left anterior or posterior fascicular block and first-degree AV block). Some key points to consider in the workup include:
- Laboratory tests, such as electrolytes, particularly potassium and magnesium levels, complete blood count, cardiac enzymes, and thyroid function tests
- Ambulatory ECG monitoring with a 24-48 hour Holter monitor or 14-30 day event recorder to detect intermittent high-degree AV block
- An echocardiogram to assess structural heart disease, ventricular function, and valvular abnormalities
- Exercise stress testing to evaluate chronotropic competence and exercise-induced conduction abnormalities
- Electrophysiology study should be considered in patients with unexplained syncope to assess HV interval prolongation, as a prolonged HV interval (>100 ms) is highly predictive of the development of high-grade AV block 1 Patients with symptomatic trifascicular block, particularly those with syncope or documented pauses >3 seconds, generally require permanent pacemaker implantation, as recommended by the European Society of Cardiology 1 and the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines 1. Asymptomatic patients with trifascicular block should be monitored closely with regular follow-up ECGs, as the risk of progression to complete heart block is significant, and pacing has been found to have no beneficial effect on survival in these patients 1. It is essential to note that the management of trifascicular block should be individualized, taking into account the patient's symptoms, underlying heart disease, and other comorbidities, and should be guided by the most recent and highest quality evidence, such as the 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1.
From the Research
Trifascicular Block Workup
The workup for trifascicular block involves several diagnostic steps and considerations for treatment.
- Diagnosis of trifascicular block can be made using clinical evaluation, ECG monitoring, and His bundle electrogram (HBE) 2.
- Patients with trifascicular block can be classified into different groups based on the severity and acuteness of the condition, including acute transient, acute advanced, chronic, and chronic advanced trifascicular block 2.
- The risk of adverse cardiovascular outcomes, such as syncope, pacemaker implantation, and complete heart block, increases with the complexity of the fascicular block 3.
- Treatment with pacemakers is often indicated for patients with severe symptoms, and can lead to significant improvement in outcomes 2, 3.
- In some cases, trifascicular block may be associated with underlying conditions such as myocardial infarction, and the long-term prognosis may depend on the residual coronary and myocardial function rather than the risk of recurrent heart block 4.
- The decision to implant a pacemaker should be based on the individual patient's condition and symptoms, as well as the presence of other underlying health conditions 2, 3, 4.
- Patients with trifascicular block should be closely monitored for signs of worsening condition, such as syncope or Adams-Stokes syndrome, and treated promptly if necessary 2, 3.