Electrocerebral accompaniments of syncope associated with malignant ventricular arrhythmias.
Level 4 - case-series / case-control
Prospective observational case series of patients undergoing electrophysiological testing
PubMed 3369769 · doi:10.7326/0003-4819-108-6-791
What was done
Fourteen patients with automatic implantable cardioverter defibrillators (implanted for previous cardiac arrest or life-threatening arrhythmias) underwent continuous electrocardiographic, electroencephalographic, and video monitoring during deliberate induction of ventricular dysrhythmias for routine postoperative device testing in a university medical center electrophysiology laboratory.
What was found
A total of 22 episodes of ventricular tachycardia or fibrillation lasting 15 to 126 seconds were induced, resulting in definite loss of consciousness in 15 instances and probable loss in 2. Ten episodes involved motor activity characterized by tonic postures or irregular muscle twitching. Following return of consciousness, patients experienced obtundation or confusion lasting up to 30 seconds. EEG changes varied: background slowing typically preceded relative loss of electrocerebral activity; 2 patients had background attenuation with little prior slowing; and in 5 episodes, EEGs showed no change prior to unconsciousness but slowed afterward in 4. No electrographic seizure activity occurred.
Why it matters
The study demonstrates that acute cerebral hypoperfusion from malignant arrhythmias frequently induces involuntary motor activity and brief post-event confusion, which can clinically mimic epileptic seizures despite showing EEG slowing or suppression without epileptiform discharges.
Limits
The sample size is very small (14 patients, 22 induced episodes) from a single center. The setting of controlled, induced ventricular arrhythmias during electrophysiology testing may not fully reflect the clinical dynamics of spontaneous syncope in outpatient settings.
Cited by
- supports When the heart stops pumping blood to supply oxygen to the brain, human consciousness is lost within 8 to 10 seconds.