EEG Artifact Versus Subclinical Status Epilepticus in a Patient Following Cardiac Arrest

A challenge in ICU EEG interpretation is identifying subclinical status epilepticus versus patterns on the ictal-interictal continuum versus other repetitive patterns. In the electrically noisy intensive care unit, identifying and eliminating interference and artifact allow accurate diagnoses from the EEG, avoiding unnecessary treatment or sedation.

We present a case during Impella (Abiomed Inc, Danvers, MA) continuous flow left ventricular assist device use where the EEG artifact was initially misinterpreted as seizure by the resident and treated as status epilepticus because of the "focal" sharply contoured repetitive pattern. During percutaneous coronary intervention (PCI), an 88-year-old developed ventricular tachycardia followed by ventricular fibrillation requiring chest compressions for 10 min, multiple defibrillations, and treatment with epinephrine, amiodarone, calcium, bicarbonate, and magnesium. The patient had an Impella placed during PCI with therapeutic hypothermia initiated after the cardiopulmonary arrest. His neurological exam demonstrated preserved pupillary, corneal, gag and cough reflexes and spontaneous respirations.

Long-term video EEG monitoring is included in our institution's hypothermia protocol. Initial baseline EEG performed 2 h after PCI showed a persistent rhythmic sharp discharge from the left central temporal region resembling left hemisphere status epilepticus. The sharp waves have an alternating repeating 2:1 relationship with the EKG rhythm strip. This is best seen in the left hemisphere, which we posit is related to the Impella's positioning across the aortic valve pointing toward the patient's left side. A chest x-ray confirmed the device's position immediately before EEG monitoring. Arterial pressure tracings were not available in the chart.

There is a low-amplitude spiky artifact; however, there was no pacing at that time. It is possible that synergistic flow with systole/diastole reinforced the pulsatility with movement of the Impella, resulting in the alternating pattern. The patient's hemodynamic instability precluded extensive troubleshooting with the Impella device, but after EEG repositioning, the artifact was eliminated.