Can a patient with a normal 24-hour Holter monitor (electrocardiogram (ECG) trace) and a history of two unexplained syncopes, one with reported body jerking, still be at risk for Brugada syndrome, a serious ventricular arrhythmia?

Risk of Serious Arrhythmia with Normal 24-Hour Holter Monitor

Yes, a patient with two unexplained syncopes (one with body jerking) can still have Brugada syndrome or other serious ventricular arrhythmias despite a normal 24-hour Holter monitor, because the diagnostic ECG pattern in Brugada syndrome is transient and intermittent, and life-threatening arrhythmias may not occur during the brief monitoring period. 1

Why a Normal Holter Does Not Exclude Serious Arrhythmia

Transient Nature of Brugada ECG Pattern

• The type 1 Brugada ECG pattern is not continuously present and can be completely absent on standard ECG recordings, appearing only intermittently or after specific triggers 1
• The diagnostic ECG findings may change over time or be present only after provocative maneuvers such as sodium channel blocker administration, fever, or vagotonic states 1
• Serial ECGs are essential because the pattern fluctuates, and a single normal ECG (or 24-hour Holter) does not exclude the diagnosis 1

Arrhythmias Occur Unpredictably

• Ventricular arrhythmias in Brugada syndrome typically occur at rest or during sleep due to increased vagal tone, not necessarily during a 24-hour monitoring period 2, 3
• The annual incidence of arrhythmic events in Brugada patients with syncope is 3.2% per year, meaning most patients will not have an event captured during brief monitoring 1
• In one multicenter study, patients with Brugada syndrome and syncope had appropriate ICD shocks in only 10% during a mean follow-up of 38 months, demonstrating the infrequent but serious nature of these arrhythmias 2

High-Risk Features in This Patient

Clinical Red Flags Present

• Two unexplained syncopes with low episode count (1-2) is associated with cardiac causes rather than benign reflex syncope 2
• Body jerking during syncope suggests possible seizure-like activity from cerebral hypoperfusion due to ventricular arrhythmia, which can mimic epilepsy 2
• Absence of typical vasovagal prodrome (nausea, warmth, specific triggers like pain or crowded environments) makes cardiac arrhythmia more likely 2, 4

Distinguishing Arrhythmic from Non-Arrhythmic Syncope

• Arrhythmic syncope in Brugada syndrome typically has no prodromes and is never triggered by hot/crowded surroundings, pain, emotional stress, seeing blood, or prolonged standing 4
• Urinary incontinence during the event increases the likelihood of arrhythmic cause (relative risk 4.6) 4
• Syncope occurring during exertion, in supine position, or with sudden loss of consciousness without prodrome suggests cardiac etiology 2

Essential Next Steps for Risk Stratification

Mandatory Initial Evaluation

• Obtain 12-lead ECG with high precordial lead placement (V1-V2 in 2nd or 3rd intercostal space) to improve detection of type 1 Brugada pattern 1
• Repeat ECGs serially because the pattern may be intermittent and not present on a single recording 1
• Detailed family history specifically asking about sudden cardiac death <50 years, unexplained drowning, syncope, or seizures in relatives 2, 1

Consider Provocative Testing

• Sodium channel blocker challenge (ajmaline, flecainide, procainamide, or pilsicainide) should be considered if clinical suspicion is high but baseline ECG is normal 1
• The test should be terminated if ventricular arrhythmias develop, marked QRS widening occurs, or type 1 pattern appears 1
• Patients with drug-induced patterns have lower risk than those with spontaneous patterns, but diagnosis can still be established 1

Additional Diagnostic Workup

• Echocardiography to exclude structural heart disease that could cause ventricular arrhythmias 2
• Exercise stress testing if syncope was exertion-related 5
• Electrophysiology study may be considered in patients with structural heart disease and unexplained syncope to assess for inducible ventricular arrhythmias 2

Management Based on Findings

If Brugada Syndrome is Diagnosed

• ICD implantation is Class I recommendation for patients with spontaneous type 1 ECG pattern AND history of syncope presumed arrhythmic 2, 1
• ICD should be considered (Class IIa) for patients with spontaneous type 1 pattern and syncope 1
• Patients with syncope and spontaneous type 1 ECG have 6-fold higher risk of cardiac arrest compared to asymptomatic patients 1

If Brugada Pattern is Only Drug-Induced

• Consider implantable loop recorder (ILR) to capture the rhythm during future events and definitively establish the cause of syncope 2
• Asymptomatic patients with only drug-induced patterns have low risk and do not require ICD 1

Lifestyle Modifications for All Diagnosed Patients

• Avoid fever triggers - aggressively treat any fever with antipyretics as fever can unmask the ECG pattern and precipitate ventricular fibrillation 1
• Avoid large meals and excessive alcohol as these act as vagal triggers 1
• Avoid specific medications including certain psychotropic agents, anesthetic agents, and sodium channel blockers 1

Critical Pitfalls to Avoid

• Do not assume a normal Holter excludes life-threatening arrhythmia - the sensitivity of 24-hour monitoring for capturing infrequent arrhythmic events is extremely low 1, 3
• Do not dismiss syncope as "just vasovagal" without excluding cardiac causes, especially with atypical features like absence of prodrome or body jerking 2, 4
• Do not rely on a single normal ECG - the Brugada pattern is dynamic and requires serial ECGs or provocative testing for diagnosis 1
• Do not overlook family history - approximately 30% of cases are de novo mutations, but family screening can identify affected relatives and strengthen diagnostic probability 6
• Do not confuse non-arrhythmic syncope with low-risk disease - while 57% of syncope in Brugada patients may be non-arrhythmic (vasovagal), the presence of the Brugada ECG pattern itself indicates underlying risk that requires ongoing surveillance 4

Bottom Line

This patient requires immediate referral to an electrophysiologist regardless of the normal Holter result 1. The combination of unexplained syncope with body jerking, low episode count, and absence of typical vasovagal triggers creates sufficient concern for an arrhythmic cause that warrants comprehensive evaluation including serial ECGs with high precordial leads, possible sodium channel blocker challenge, and consideration of implantable loop recorder if initial workup is unrevealing 2, 1, 5. A normal 24-hour Holter provides false reassurance in this clinical context.