What cardiac arrhythmias can cause seizures?

Cardiac Arrhythmias That Can Cause Seizures

Bradyarrhythmias, particularly severe sinus bradycardia and asystole, are the most common cardiac arrhythmias that can cause seizures due to cerebral hypoperfusion. 1, 2

Types of Arrhythmias Associated with Seizures

Primary Causes (Arrhythmias Leading to Seizures)

1. Bradyarrhythmias

   • Severe sinus bradycardia: Can lead to cerebral hypoperfusion resulting in seizure-like activity 2
   • Asystole: Complete absence of electrical activity causing profound cerebral hypoperfusion 1
   • High-grade AV blocks: Significant conduction delays leading to inadequate cerebral perfusion 3

2. Tachyarrhythmias

   • Ventricular tachycardia (VT): Particularly sustained VT can reduce cardiac output and cerebral perfusion 3
   • Ventricular fibrillation (VF): Chaotic ventricular activity causing ineffective cardiac output 3
   • Torsades de pointes: A specific form of polymorphic VT associated with QT prolongation 3

Secondary Associations (Seizures Leading to Arrhythmias)

While not directly answering the question, it's important to note the bidirectional relationship:

• Post-ictal atrial fibrillation: Can occur following seizures 4, 1
• Ictal sinus tachycardia: Most common cardiac manifestation during seizures 1

Pathophysiological Mechanism

The primary mechanism by which cardiac arrhythmias cause seizures is cerebral hypoperfusion. When cardiac output falls below the threshold needed to maintain adequate cerebral blood flow, seizure activity can occur as a manifestation of brain hypoxia. This is particularly common with:

• Arrhythmias causing prolonged pauses (>6 seconds)
• Severe bradycardia with heart rates <30 bpm
• Sustained ventricular arrhythmias reducing effective cardiac output

Clinical Considerations

Diagnostic Challenges

• Arrhythmia-induced seizures may be misdiagnosed as primary epileptic events 3
• Epilepsy patients with unexplained seizures despite optimal anti-seizure medication should undergo cardiac evaluation 2

High-Risk Populations

• Elderly patients with conduction system disease
• Patients with structural heart disease
• Those taking medications that can prolong QT interval or affect cardiac conduction 3
• Patients with electrolyte abnormalities (particularly hypokalemia, hypomagnesemia) 5

Medications Associated with Arrhythmogenic Seizures

• QT-prolonging medications: Can induce torsades de pointes 3
• Tricyclic antidepressants: Can cause QRS prolongation and ventricular arrhythmias 3
• Certain antipsychotics: Particularly thioridazine and haloperidol can prolong QT 3

Management Approach

1. Immediate management:

   • Treat the underlying arrhythmia
   • For bradyarrhythmias: Consider temporary pacing 2
   • For tachyarrhythmias: Appropriate anti-arrhythmic therapy or cardioversion 3

2. Definitive treatment:

   • Permanent pacemaker implantation for recurrent bradyarrhythmias 2
   • ICD consideration for ventricular arrhythmias
   • Withdrawal of offending medications
   • Correction of electrolyte abnormalities 3

Prevention Strategies

• Medication review: Avoid combinations of drugs that may prolong QT interval or affect cardiac conduction 3
• Electrolyte monitoring: Maintain normal levels of potassium, magnesium, and calcium 3
• Cardiac screening: Consider in patients with unexplained seizures, especially if they occur during sleep or with exercise 3

In patients presenting with seizures of unclear etiology, particularly when conventional anti-seizure medications fail, cardiac arrhythmias should be considered in the differential diagnosis, and appropriate cardiac monitoring should be performed to identify potential arrhythmic causes.