Electrocerebral Signature of Cardiac Death

Abstract

Background: Electroencephalography (EEG) findings following cardiovascular collapse in death are uncertain. We aimed to characterize EEG changes immediately preceding and following cardiac death.

Methods: We retrospectively analyzed EEGs of patients who died from cardiac arrest while undergoing standard EEG monitoring in an intensive care unit. Patients with brain death preceding cardiac death were excluded. Three events during fatal cardiovascular failure were investigated: (1) last recorded QRS complex on electrocardiogram (QRS₀), (2) cessation of cerebral blood flow (CBF₀) estimated as the time that blood pressure and heart rate dropped below set thresholds, and (3) electrocerebral silence on EEG (EEG₀). We evaluated EEG spectral power, coherence, and permutation entropy at these time points.

Results: Among 19 patients who died while undergoing EEG monitoring, seven (37%) had a comfort-measures-only status and 18 (95%) had a do-not-resuscitate status in place at the time of death. EEG₀ occurred at the time of QRS₀ in five patients and after QRS₀ in two patients (cohort median - 2.0, interquartile range - 8.0 to 0.0), whereas EEG₀ was seen at the time of CBF₀ in six patients and following CBF₀ in 11 patients (cohort median 2.0 min, interquartile range - 1.5 to 6.0). After CBF₀, full-spectrum log power (p < 0.001) and coherence (p < 0.001) decreased on EEG, whereas delta (p = 0.007) and theta (p < 0.001) permutation entropy increased.

Conclusions: Rarely may patients have transient electrocerebral activity following the last recorded QRS (less than 5 min) and estimated cessation of cerebral blood flow. These results may have implications for discussions around cardiopulmonary resuscitation and organ donation.

Keywords: Brain hypoxia; Cardiac arrest; Consciousness; Death; Encephalography; Hypotension.

Fig. 1

Timeline of three pathophysiologic events. Relationship of electrocerebral silence on EEG (EEG₀) and last QRS complex on ECG (QRS₀) in relation to cessation of cerebral blood flow (CBF₀). The y axis represents the 19 patients in the study and the x axis represents time in minutes. Patients are ordered by magnitude of change in global power 5 min before vs. 5 min after CBF₀. For patient 12, temp_EEG₀ represents time of temporary electrocerebral silence before the return of cerebral activity (EEG₁; see Fig. 3 for details). QRS₀ was not available in two patients (no. 2 and no. 17) because of ECG artifacts following chest compressions and poorly connected ECG leads. ECG electrocardiogram, EEG electroencephalograph, EEG₁ return of cerebral activity

Fig. 2

Change in full-spectrum EEG features after CBF₀. Boxplot showing change in epoch-averaged and channel-averaged full-spectrum EEG features 5 min before vs. 5 min after CBF₀ for all patients. Cohort-wide changes in log power and coherence are statistically significant (p < 0.028). CBF₀ cessation of cerebral blood flow, EEG electroencephalograph

Fig. 3

Raw EEG data and power spectral density in a patient with electrocerebral activity on EEG after CBF₀ and a brief period of isoelectric EEG. Sixty-five-year-old woman who was hospitalized for refractory status epilepticus in the setting of anoxic brain injury. On hospital day 10, the course was complicated by cardiac arrest with PEA. After chest compressions were performed for 20 min, the patient underwent withdrawal of life-sustaining therapies at the request of the family. Power spectral density of her EEG is displayed (a), calculated from channels Fz, Cz, and Pz because these are less frequently affected by muscle and ECG artifact. Colored lines at the bottom indicate nonconvulsive status epilepticus (NCSE), CBF₀, EEG₀, PEA, start of chest compressions (CC), end of chest compressions (CC_end), and return of cerebral activity ( EEG₁). EEG (bipolar montage, sensitivity of 5 μV/mm, 60-Hz notch filter) at the time (temp_EEG₀) demonstrated no clear electrocerebral activity (b). Following the activity after CBF₀ and a brief period of isoelectric EEG, electrocerebral activity returned ( EEG₁) (c) (see Supplemental Fig. 2 for raw EEG data at the remaining events). The power spectral density plot revealed decreased power 36 min before CBF₀. Artifacts are seen throughout in the 20-Hz range, and prominent artifacts due to chest compressions are seen between 18 and 38 min following CBF₀. At CBF₀, median log power was − 4.10 (IQR − 12.08 to − 2.69, range − 16.61 to 2.96), median coherence was 0.23 (IQR 0.01–0.94, range − 0.50 to 0.99), and median permutation entropy was 3.31 (IQR 2.60–3.87, range 1.85–4.45). CBF₀ cessation of cerebral blood flow, ECG electrocardiogram, EEG electroencephalograph, EEG₀ electrocerebral silence on EEG, IQR interquartile range, PEA pulseless electrical activity