Electroencephalography (EEG) for neurological prognostication after cardiac arrest and targeted temperature management; rationale and study design

Table 1 Previous publications describing malignant EEG patterns are presented

Described malignant EEG patterns in previous publications	Features of the ACNS EEG terminology included in the hypotheses of the present study	Number of previous publications:
		Treated with TTM			Not treated with TTM
		FPR = 0	FPR < 5	FPR > 5	FPR = 0	FPR < 5	FPR > 5
		PPV = 100	PPV > 95	PPV < 95	PPV = 100	PPV > 95	PPV < 95
“Burst-suppr”	Burst-suppr (suppr >50%)	3 [10],[33],[34]	1 [35]	0	5 [36]-[40]	1 [41]	0
“Discontinous background with suppr >1 sec”	Discontinuous background (suppr >10%)	0	0	0	3 [22],[39],[42]	0	0
“Low voltage background (<20 μV)”	Low voltage background (most activity <20 μV)	1 [33]	1 [10]	0	8 [22],[36]-[42]	0	0
“Alfa coma pattern”	Reversed anterior-posterior gradient	1 [33]	0	0	5 [22],[36],[37],[43],[44]	1 [45]	3 [39],[46],[47]
“PDs on a flat background”	Continuous PDs and Voltage = suppressed (<10 μV)	0	0	0	2 [22],[36]	0	0
“Continuous Epileptiform Activity or Electrographic Status Epilepticus (broad definition)”	Abundant PDs or Abundant Polyspike-/Spike-/Sharp-and-Waves	3 [14],[33],[48]	1 [10]	0	1 [39]	0	1 [38]
“Electrographic seizure activity”	Unequivocal seizures	1 [33]	0	0	0	0	0
“Unreactive background”	Reactivity absent or SIRPIDs only	3 [33],[49],[50]	0	0	1 [39]	0	1 [51]

Malignant EEG patterns after cardiac arrest described in previously published studies [10],[14],[22],[33]-[51] are presented according to their predicting values (PPV) and false positive ratio (FPR) and whether target temperature management (TTM) were applied or not. We have listed the features (or combinations of features) of the American Clinical Neurophysiology Society’s critical care EEG terminology, that we consider correspond to the previously published malignant patterns, which are chosen to be tested in the hypotheses of this study. They were chosen since at least one previous study reported FPR < 5% or PPV > 95% for corresponding EEG patterns. The patterns were thus considered to have a potential to become markers for poor prognosis. For some studies the described malignant patterns were part of an EEG grading system and therefore the prevalence of these patterns could not be decided. PDs = Periodic Discharges, SIRPIDs = Stimulus-induced rhythmic, periodic, or ictal discharges.

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