Electrocardiographic changes during induced therapeutic hypothermia in comatose survivors after cardiac arrest

Table 1 Baseline characteristics of study population

Patients	47
Age (median, range)	65.9 (19-85)
Male	40 (85.1%)
Cardiogenic shock at admission	15 (31.9%)
Urgent coronary angiography	28 (59.6%)
Left ventricular ejection fraction	43.2 (15.3%)
Initial Rhythm, n (%)
Ventricular Fibrillation	30 (63.8)
Asystole	14 (29.8)
Pulseless Electrical Activity	3 (6.4)
Rhythm at admission, n (%)
Sinus rhythm	31 (66)
Atrial fibrillation	8 (17)
AV block/nodal rhythm/paced rhythm	8 (17)
TH protocol
Temperature at admission	35.7 (0.7)
Induction time (from admission to TH, h)	4.8 (2.6)
Time in TH (median, range, h)	20.8 (5-28.5)
Temperature during TH	32.8 (0.5)
Rewarming time (from TH to 36 °C, h)	11.3 (7.4)
Cause of CA, n (%)
Acute coronary syndrome	21 (44.7)
Chronic coronary disease1	8 (17.0)
Chronic heart failure	4 (8.5)
Others/unknown2	14 (29.8)

¹This group represents those patients with known preexisting coronary disease but without an acute coronary syndrome diagnosis at admission. Presumed cause were ventricular arrhythmias secondary to chronic coronary disease;

²No final diagnosis of the cardiac arrest could be made for this group, all of these patients died during admission. TH: Therapeutic hypothermia. Data are number (percentage) or mean (standard deviation).

Table 2 Changes in electrocardiograms intervals, represented as means, standard deviation (in brackets) and P for difference

	Admission(ECG A)	During MTH(ECG B)	After MTH(ECG C)	P for difference(A to B)	P for difference(B to C)	P for difference(A to C)
RR interval (ms)	653.8 (174.6)	818.1 (222.6)	656.9 (114.4)	< 0.0005a	< 0.0005a	0.9
Heart rate (bpm)	97.9 (24.9)	78.3 (19.8)	94.2 (17.4)	< 0.0005a	< 0.0005a	0.3
PR interval (ms)	169.2 (42.7)	179.3 (37.5)	161.2 (37.0)	0.090	0.003a	0.2
QRS duration (ms)	108.8 (23.2)	118.7 (37.9)	102.0 (22.9)	0.041a	< 0.0005a	0.029a
QT interval (ms)	353.8 (58.1)	448.1 (106.1)	374.9 (72.0)	< 0.0005a	< 0.0005a	0.042a
QTc interval (ms)	441.7 (50.7)	499.2 (95.5)	463.9 (76.4)	< 0.0005a	0.017a	0.046a

Indicates statistical significance (^aP < 0.05); ms: Milliseconds; ECG: Electrocardiograms.

Table 3 Changes in ST segment and T wave, represented as means, standard deviation (in brackets) and P for difference

	Admission(ECG A)	During MTH(ECG B)	After MTH(ECG C)	P for difference(A to B)	P for difference(B to C)	P for difference(A to C)
ST deviation lead II	+ 0.05 (1.4)	- 0.20 (1.4)	- 0.12 (0.7)	0.2	0.3	0.4
ST deviation lead v2	+ 0.39 (3.2)	+ 0.08 (0.6)	+ 0.32 (1.0)	0.4	0.06	0.9
ST deviation lead v5	- 0.25 (1.9)	- 0.38 (0.8)	- 0.16 (0.8)	0.6	0.036a	0.7
T wave lead II	+ 1.0 (1.8)	+ 0.63 (1.1)	+ 0.38 (1.2)	0.2	0.1	0.036a
T wave lead v2	+ 2.0 (3.6)	+ 2.10 (3.2)	+ 1.62 (2.4)	0.8	0.3	0.5
T wave lead v5	+ 1.60 (2.9)	+ 0.84 (2.3)	+ 0.04 (2.4)	0.1	0.013a	< 0.0005a

Indicates statistical significance (^aP < 0.05). Units are millivolts. +: ST segment elevation or T-wave positive deflection; -: Descent in ST segment or T-wave negative deflection.

Table 4 Incidence of arrhythmias or rhythm changes during hypothermia

New arrhythmias during TH	38.3%
Non sustained monomorphic VT	19.1%
Bradycardia < 50 bpm/paced rhythm	10.6%
Accelerated nodal rhythm	8.5%
Atrial fibrillation	6.4%
Sustained VT	0%
Polymorphic VT or VF	0%
Change to sinus rhythm with TH	12.8%
Atrial fibrillation to sinus rhythm	6.4%
Accelerated nodal rhythm to sinus rhythm	6.4%

TH: Therapeutic hypothermia; VT: Ventricular tachycardia; VF: Ventricular fibrillation.