To Cath or Not to Cath?

C. Initiate active core rewarming, be prepared for ACLS as this patient is at high risk for ventricular fibrillation

Discussion

EKG reveals Osborn waves (Figure 1.). With active rewarming, the Osborn waves became less pronounced and eventually resolved. Interestingly, normalization of her pH did not affect the EKG changes, as those lingered when her temperature was 30.2 ^oC and her pH was 7.43.

Osborn (or J) waves were named after John Osborn who described their presence as a herald of ventricular fibrillation in hypothermic dogs. They are defined as a positive deflection at the J point (1). Hypothermia increases the ratio of the conduction time to the refractory period, rendering the heart more prone to ventricular fibrillation. Sympathomimetic amines can decrease the conduction time by increasing the conduction velocity. They may be used to decrease the incidence of ventricular fibrillation, although data regarding their use in humans are lacking (2). Finally, Osborn waves can also be seen in early repolarization, increased vagal tone, hypercalcemia, and Brugada syndrome. Their presence can be benign or associated with increased risk for ventricular fibrillation (3). Clinicians should always interpret their presence in the right clinical context, especially since they are frequently interpreted as “ST elevation/acute myocardial infarction” by the ECG machine.

References

1. Osborn JJ. Experimental hypothermia; respiratory and blood pH changes in relation to cardiac function. The American journal of physiology 1953; 175: 389-398.
2. Covino BG, D'Amato HE. Mechanism of ventricular fibrillation in hypothermia. Circulation research 1962; 10: 148-155.
3. Junttila MJ, Sager SJ, Tikkanen JT, Anttonen O, Huikuri HV, Myerburg RJ. Clinical significance of variants of J-points and J-waves: early repolarization patterns and risk. European heart journal 2012; 33: 2639-2643.