Should a patient being evaluated for psychogenic non‑epileptic seizures (PNES) with transient first‑degree atrioventricular (AV) block and a documented 2:1 AV block on Holter monitoring undergo a formal cardiac evaluation, and why, despite non‑syncopal loss of consciousness?

Yes, This Patient Absolutely Requires Urgent Cardiac Evaluation

Despite the non-syncopal nature of her loss of consciousness, the documented 2:1 AV block on Holter monitoring mandates immediate specialist cardiovascular assessment because this conduction abnormality carries significant risk for progression to complete heart block, sudden cardiac death, and may actually be the true cause of her symptoms rather than PNES.

Why Cardiac Evaluation Takes Priority

The Critical Conduction Abnormality

The presence of 2:1 AV block is a high-risk finding that cannot be dismissed, even in a patient being investigated for PNES. Here's the algorithmic reasoning:

First-degree AV block alone (prolonged PR interval) is generally benign and requires no intervention. However, 2:1 AV block represents a more advanced conduction disturbance where every other atrial impulse fails to conduct to the ventricles. This pattern:

• Cannot be classified as Mobitz I or II without additional ECG evidence 1
• May be either AV nodal or infranodal in location
• Requires determination of the level of block because infranodal blocks carry high risk and require pacing regardless of symptoms 2

The Guideline-Based Mandate

The NICE guidelines for transient loss of consciousness are unequivocal: "Urgent specialist assessment and treatment must be arranged for patients who have TLoC due to a cardiac condition that may place them at risk for severe adverse events, including sudden death" 1. Specifically:

• Any ECG abnormality in the context of loss of consciousness warrants prompt cardiovascular assessment by a specialist 1
• When conduction abnormalities are present, the guidelines recommend 24-48 hour Holter monitoring to look for asymptomatic severe atrioventricular block, which may require pacing on prognostic grounds 1
• The presence of documented AV block increases the probability that loss of consciousness was due to atrioventricular block 1

Why "Non-Syncopal" Doesn't Matter Here

This is a critical clinical pitfall to avoid. The characterization of loss of consciousness as "non-syncopal" may be:

1. Incorrect: Witnesses often mischaracterize syncopal events, especially when brief seizure-like activity occurs during syncope (which is common with cardiac causes) 1

2. Irrelevant to risk stratification: The 2:1 AV block exists independent of symptom characterization and carries inherent mortality risk

3. Potentially both conditions coexist: Patients can have both PNES and cardiac conduction disease. The documented AV block must be evaluated regardless of the PNES diagnosis 3, 4

The Specific Cardiac Workup Required

Based on the 2004 European Heart Journal guidelines and NICE recommendations, this patient needs:

Immediate Steps:

• Specialist cardiology referral (not just general medicine follow-up)
• 12-lead ECG review by a cardiologist to assess for bundle branch block patterns and determine likely level of block 5
• Echocardiography to exclude structural heart disease 1, 5

Definitive Evaluation:

• Electrophysiological study if the level of block cannot be determined non-invasively 5, 2
  • This will determine if block is AV nodal (potentially benign) or infranodal (requires pacing)
  • Infranodal 2:1 block has high risk of progression to complete heart block

Monitoring Strategy:

• Extended ambulatory monitoring (implantable loop recorder if episodes are infrequent) to capture correlation between symptoms and rhythm 1, 6
• The goal is to document whether loss of consciousness episodes correlate with high-grade AV block

The Evidence for Serious Risk

Research demonstrates that paroxysmal AV block can present with:

• Long histories of unexplained syncope (mean 8 years in one series) with normal baseline ECGs 3
• Abrupt onset of complete heart block without warning signs 3
• Pauses averaging 9 seconds during symptomatic episodes 3
• Masquerading as seizures due to convulsive movements from cerebral hypoperfusion 4

One case series documented that even with normal initial testing including Holter monitoring, persistent symptoms ultimately revealed high-grade AV block requiring pacemaker placement 6.

Common Pitfalls to Avoid

1. Don't assume PNES excludes cardiac disease: These are not mutually exclusive diagnoses
2. Don't dismiss conduction abnormalities because symptoms seem "non-cardiac": AV block causes cerebral hypoperfusion that can mimic seizures
3. Don't delay evaluation: Progression to complete heart block can be sudden and unpredictable 3, 2
4. Don't rely on symptom-rhythm correlation alone: Asymptomatic severe AV block may require pacing on prognostic grounds 1

Bottom Line

The documented 2:1 AV block transforms this from a straightforward PNES evaluation into a potentially life-threatening cardiac conduction disorder requiring urgent specialist assessment. The mortality risk from unrecognized progressive AV block far outweighs any concern about over-investigation. Pacemaker implantation may ultimately be required and could be life-saving 7, 3, 6.