What is the severity of a trifascicular block and is it reversible?

From the Guidelines

Trifascicular heart block is a serious cardiac conduction disorder that requires prompt medical attention and often necessitates permanent pacemaker implantation to prevent progression to complete heart block and potential sudden cardiac arrest. This condition involves impairment in all three fascicles of the heart's electrical conduction system: the right bundle branch and both divisions of the left bundle branch. The severity of trifascicular heart block stems from its potential to progress to complete heart block, which can cause sudden cardiac arrest, as noted in the guidelines for cardiac pacing and cardiac resynchronization therapy 1.

Key Considerations

• The condition typically doesn't resolve on its own and requires medical intervention.
• Treatment depends on symptoms and ECG findings, with syncope, presyncope, or significant pauses on monitoring necessitating immediate hospitalization and temporary pacing while awaiting permanent pacemaker placement.
• Some reversible causes, such as medication effects, electrolyte abnormalities, or acute cardiac events, may resolve the conduction issue if addressed promptly.
• Most cases, especially those related to age-related fibrosis or degenerative changes in the conduction system, are permanent and progressive, emphasizing the need for regular cardiac follow-up.

Diagnostic and Therapeutic Approach

• An electrophysiological study may be helpful in evaluating the risk of progression to high-degree AV block, particularly if it demonstrates an HV interval >100 ms or intra- or infra-Hisian block during incremental atrial pacing 1.
• The use of an implantable loop recorder has shown that most syncopal recurrences in patients with bundle branch block are due to prolonged asystolic pauses, mainly attributable to sudden-onset paroxysmal AV block, supporting the consideration of pacemaker implantation in such cases 1.
• Guidelines suggest that in patients with syncope and bundle branch block, pacemaker implantation is recommended if there are definite abnormalities of the His-Purkinje conduction, predicting the development of stable AV block in a significant proportion of patients 1.

Prognosis and Management

• The prognosis for patients with trifascicular heart block depends on the presence of symptoms, the degree of conduction disturbance, and the underlying cardiac condition.
• Regular follow-up with a cardiologist, including periodic ECGs and possibly Holter monitoring, is crucial to track the progression of the condition and adjust treatment as necessary.
• The 2012 ACCF/AHA/HRS focused update incorporated into the ACCF/AHA/HRS 2008 guidelines for device-based therapy of cardiac rhythm abnormalities provides further guidance on the management of bifascicular and trifascicular block, emphasizing the role of pacing in preventing symptoms and potentially reducing the risk of sudden death 1.

From the Research

Seriousness of Trifascicular Heart Block

• Trifascicular heart block is a serious condition that can lead to severe symptoms such as syncope and Adams-Stokes syndrome 2.
• The condition can be acute or chronic, and its severity can vary depending on the individual case 2, 3.
• In some cases, trifascicular heart block can be a sign of underlying heart disease, such as coronary artery disease or cardiomyopathy 2, 4.

Reversibility of Trifascicular Heart Block

• In some cases, trifascicular heart block can be reversible, especially if it is caused by a temporary condition such as acute myocarditis or myocardial infarction 2, 4.
• Surgical closure of a congenital atrial septal defect can also lead to the resolution of trifascicular heart block 3.
• However, in other cases, trifascicular heart block can be a permanent condition that requires treatment with a pacemaker 2, 5.

Treatment and Outcomes

• Treatment of trifascicular heart block often involves the implantation of a pacemaker, which can help to alleviate symptoms and improve quality of life 2, 5.
• The prognosis for individuals with trifascicular heart block varies depending on the underlying cause of the condition and the presence of other health problems 2, 4.
• In general, individuals with trifascicular heart block are at increased risk of adverse cardiovascular outcomes, including syncope, pacemaker implantation, and death 5.