Thanks to Rohan Laging for the details of this case.
This 21 year old man was found lying on the ground next to a bus stop at 0620 hours on a Sunday morning where the minimum overnight temperature was 6 degreesC. An ambulance was called, and their findings on arrival were: GCS 9 (E2, V2, M5) with pupils that were 3 mm in size and non reactive to light. There were no signs of head trauma.
The heart rate was 68 beats per minute, the blood pressure was 110/70 mm Hg, the respiratory rate was 12 breaths per minute and the SaO2 was 98% on room air. The tympanic temperature was 31.2 C. There were no signs of seizure (no tongue biting or urine incontinence) or signs of injection sites in the veins. There was a small plastic bottle containing a clear odourless fluid in the patient's pocket.
The patient was taken to a nearby Emergency Department (ED), arriving at 0645 hours. Thefindings on arrival were: GCS 8, the heart rate was 60 beats per minute, the blood pressure was 120/70 mm Hg, the respiratory rate was 12 breaths per minute and the SaO2 was 99% on room air. The patient's temperature was 29.4 C.
The results of blood tests were:
- Blood glucose was 6.5 mmol/L
- Hb 163 g/L; white cell count was 14.48 x 109/L; haematocrit was 0.50 (N 0.40-0.54)
- Ethanol concentration was < 2 mmol/L
- Venous blood gases: pH 7.29 pCO2 51 mm Hg pO2 32 Base excess -3
- Serum electrolyte concentrations: Na+ 141 mmol/L K+ 3.8 mmol/L Cl- 105 mmol/L, Bicarbonate 22 mmol/L Urea 4.6 mmol/L Creatinine 80 mmol/L
- Creatinine kinase (CK) concentration was 132 U/L (N 60-220 U/L)
- Serum troponin I was 3 ng/L (N <15 ng/L)
A 12 lead ECG was taken at 0703 (Figure 1)
The main findings are: sinus bradycardia (ventricular rate of about 58 beats per minute) with aPR interval of 204 msec. The QT interval is prolonged (500 msec), and Leads II, III, aVF V5 and V6 have a J wave and slight (1-2 mm) ST elevation. Leads V2 to V4 have a elevated J point; there is horizontal ST elevation in Leads V2 and V3, and an up-sloping ST elevation in Lead V4. There are no artefacts due to shivering, but there is baseline wander in the frontal leads. The bradycardia and the J waves are consistent with hypothermia, but the associated ST elevation suggested the possibility of other (non hypothermic) diagnoses e.g. early repolarization syndrome or drug induced myocardial injury.
The patient was treated with external rewarming. At 0720 his temperature was 35.3 C and his GCS was 10. At 0800 his GCS was 13, and by 1000 his temperature was 36.1 C and his GCS was 15.
Figure 2 shows the ECG at 0801
The heart rate of about 70 beats per minute. The J waves and ST elevation persist in the inferolateral leads. The QT interval remains prolonged.
Figure 3 shows the ECG at 0856 and Figure4 shows the ECG at 1046
The ECG at 1046 shows sinus rhythm with a PR interval of 153 msec and a normal QT interval. The J waves in the inferior leads have nearly disappeared, and are no longer seen in Leads V5 and V6. The ST segments in the inferolateral leads are nearly isoelectric. There is slight J point elevation in Leads V2 and V3, and the ST segment is slightly concave in these leads. A repeat troponin I at 1025 was < 2 ng/L (N <15 ng/L).
The hypothermia in this case developed over a relatively short time (probably 6 hours or less) and responded rapidly to external rewarming. The ECG changes due to hypothermia are variable, and can be influenced by the cause of the hypothermia and the rapidity of onset of the hypothermia.
The ECG changes due to hypothermia include:
- Effects on rate and rhythm: sinus bradycardia, atrial fibrillation, heart block, junctional rhythms, idioventricular rhythms or ventricular fibrillation.
- Effects on QRS intervals: prolongation of the PR interval and the QT interval
- Artefacts due to shivering
- Appearance of the J wave (or Osborne wave), a slow upright deflection between the end of the QRS complex and the early portion of the ST segment. The J wave is most commonly seen in the inferolateral leads, and increases in amplitude as the body temperature falls. It seen in one third of patients with a core temperature below 30 C.
- Elevation of the J point
Less well appreciated is the effect of hypothermia on the ST segment or T wave. As this case and other reports show hypothermia can cause reversible ST segment elevation (1,2). A retrospective study of therapeutic hypothermia in survivors of out of hospital cardiac arrest noted ST-segment elevation during hypothermia in 12 percent of patients (2). An example of the ECG changes in one of these cases is shown in Figure 5.
Widespread (reversible) ST segment depression and T wave inversion can also be caused by hypothermia (3).
The J wave or Osborne wave is an enigmatic and intriguing ECG finding that has also been called s “camel-hump sign”, “late delta wave”, “hathook junction”, “hypothermic wave”, “J point wave”, “K wave”, “H wave” and “current of injury”(4). A J wave like deflection (J wave mimics) may also be seen in other conditions that are not associated with hypothermia:
- Early repolarization syndrome (ERS)
- Marked hypercalcaemia
- Brugada syndrome
- Coronary artery spasm
- Acute pulmonary oedema
- Cerebrovascular disease
- Epsilon wave - associated with arrhythmogenic right ventricular cardiomyopathy
Additional Case 1
The J wave and ST elevation in the first ECG of this case are similar to those seen in ERS. Coincidently, several days after the case discussed here, we treated a 77 year old man who had fallen into a empty bath and spent 12 hours lying in the bath. His temperature was 33 C on arrival, and his ECG is shown in Figure 6. His blood tests showed moderate rhabdomyolysis and a normal serum potassium concentration. A brain CAT scan was normal. The patient's temperature returned to normal within three hours with external rewarming.
The ECG shows ST elevation in multiple leads and notching of the J point in Leads V4 and V5. Serial troponin concentrations were normal and there was no change in serial ECG. The ECG changes are consistent with ERS. Unlike the changes seen in R_0048 the QT interval is normal and the ascending limb of the elevatedST segments are concave.
Arrhythmias may be associated with the ERS pattern in the inferior leads or mid- to lateral precordial leads, in hypothermia and in the Brugada syndrome. Some researchers have proposed that these conditions are part of a "J Wave Syndrome" (5).
Additional Case 2
Most cases of hypothermia that are seen in the ED differ from R_0048 because they occur in older patients, and the hypothermia has been present for much longer. Case 2 is a 85 year old woman who had been lying in a unheated room for 24 hours.
- Yilmaz S, Cakar MA, Vantan MB et al. ECG changes due to hypothermia developed after drowning: case report Turk J Emerg Med 2014;14:37-40
- Rolfast CL, Lust EJ, de Cock CC. Electrocardiographic changes in therapeutic hypothermia Critical Care 2012 16:R100. doi:10.1186/cc11369
- Hao Wang H, Hollingsworth J, MahlerS, Arnold T. Diffuse ST segment depression from hypothermia. Int J Emerg Med (2010) 3:451- 454 DOI 10.1007/s12245-010-0211-y
- Maruyama M, Kobayashi Y,Kodani E et al. Osborn waves: history and significance. Indian Pacing and Electrophysiology Journal 2004; 4: 33-39
- Antzelevitch C, Yan G-X. J wave syndromes Heart Rhythm. 2010; 7: 549 - 558. doi:10.1016/j.hrthm.2009.12.006.