Atrial Fibrillation in Hypothermia

Report:

Atrial fibrillation with average ventricular response 97/min

J (Osborn) waves suggest hypothermia

Prolonged QT interval

Comment:

The QT interval is only mildly prolonged for 30oC; the prolongation is most obvious in short cycles, where QT should be about 0.30”. The rate is also faster than usual, but still slow for untreated atrial fibrillation.

AF is the commonest arrhythmia in hypothermia, seen in about 50% patients. In Woden Valley Hospital (and in this Library), the incidence is only about 10%. I cannot account for this without further study.

Below is a trace taken hour and a half later, at 32.6oC (Fig 117a). The hypothermic humps (J, Osborn waves) are noticeably smaller. Their height correlates with the degree of hypothermia. It is not known whether they represent early repolarisation or delayed repolarisation86. This patient’s QRS could have also been prolonged by the (tricyclic) antidepressants, but this is unlikely: the only prolongation is attributable to the J waves.

Alcohol intoxication is a major predisposing factor in hypothermia. It’s may cause AF – the “holiday heart” as well87.

117a.

118. 53 year old lady with pleuritic chest pains. She had a long history of hypertension, but the ECGs were always normal.