Study objective: To examine the electrocerebral and clinical accompaniments of syncope associated with malignant ventricular cardiac arrhythmias.
Design: Survey of clinical and electroencephalographic changes during induced cardiac dysrhythmia.
Setting: Clinical electrophysiology laboratory of a university medical center.
Patients: Fourteen patients with automatic cardioverter defibrillators due to previous cardiac arrest or life-threatening cardiac arrhythmia.
Intervention: Deliberate induction of cardiac dysrhythmia for routine, postoperative testing of the automatic implantable cardioverter defibrillator. Continuous electrocardiographic, electroencephalographic, and video recording.
Measurements and main results: Twenty-two episodes of ventricular tachycardia or fibrillation, lasting 15 to 126 seconds, were induced with definite loss of consciousness in 15 instances and probable loss in 2. In 10 episodes, there were motor accompaniments to the unconsciousness characterized by tonic activity or irregular muscle twitching. On regaining consciousness, patients were usually obtunded or confused for up to 30 seconds, depending on duration of induced cardiac dysrhythmia and unconsciousness. Electroencephalographic changes were variable. Background slowing was usually followed by relative loss of electrocerebral activity. In 2 patients, attenuation of background electrocerebral activity followed little or no change in background rhythms. In 5 episodes, electroencephalograms showed no change before loss of consciousness, but slowed thereafter in 4.
Conclusions: Conspicuous motor activity may accompany syncope due to malignant ventricular arrhythmia and complicate the clinical distinction of syncope from seizures. Post-syncopal confusion generally lasts for less than 30 seconds. The electroencephalographic accompaniments of acute cerebral anoxia leading to syncope, and of the motor accompaniments of syncope, are more variable than previously appreciated, but electrographic seizure activity does not occur.