The Osborn wave, not just for cardiologists!

Abstract

The Osborn wave, named in the honor of John Osborn after his elegant work in 1953 1, is well known to cardiologists. It manifests as a deflection at the R-ST junction of the ECG, is usually more evident in the inferior and lateral leads 2, and has an amplitude that is inversely correlated with the core body temperature 3 (Fig. 1). It is the result of a transient, outward, potassium-mediated current in the ventricular epicardium, but not in the endocardium, creating a transmural voltage gradient during early repolarization that is reflected as the J wave. Although characteristic of hypothermia, there are other nonhypothermic precursors for Osborn waves, including severe hypercalcemia 4, subarachnoid hemorrhage 5, myocardial ischemia 6, Brugada syndrome 7, and following cardiac resuscitation 8.Fig. 1: (a) ECG of a head trauma victim recorded at a temperature of 36°C revealing sinus bradycardia, 55 beats/min without evident J waves. (b) ECG recorded at 29.6°C revealing sinus bradycardia, 48 beats/min; prolonged PR interval at 0.24 s, prolonged QRS interval at 0.16 s, a corrected QT interval of 0.5 s, and classic high-amplitude J waves. Reproduced from Omar and Abdelmalak3 with permission and modification from the Cleveland Clinic Foundation, ©2011 The Cleveland Clinic Foundation. All rights reserved.Osborn waves can be encountered in stroke units and neurocritical care, where patients are at times offered therapeutic hypothermia for its neuroprotective role. Mild to moderate hypothermia has been found to reduce ischemic brain edema in the setting of massive ischemic strokes 9,10. Therapeutic hypothermia has also led to a better outcome in patients with aneurysmal subarachnoid hemorrhage 11. Another valuable use of the Osborn wave for neurologists and neurosurgeons is its ability to raise suspicion for brain death in cases with severe head trauma after the exclusion of other hypothermic causes. An important clue is provided when the Osborn waves are unaccompanied by shivering artifacts in the ECG (and the patient is not on any sedation). In brain death, the Osborn wave is attributed to hypothermia because of the impaired thermoregulatory ability resulting from hypothalamic dysfunction 12. ICU physicians are widely exposed to the Osborn wave in their daily practice mostly as a consequence of therapeutic hypothermia frequently attempted to improve the neurological outcome in postcardiopulmonary resuscitation patients. Other causes for encountering the Osborn wave in the ICU include sepsis 13, alcohol consumption, drug intoxication 14, and cardiac arrest 8. Anesthesiologists encounter hypothermic patients in cases of cerebral aneurysm surgery when therapeutic hypothermia is occasionally utilized 15 or because of inadvertent core hypothermia that is often observed in the immediate postoperative period especially in the elderly and high-risk surgical patients secondary to the effects of anesthesia 16,17. Emergency room physicians are also exposed to the Osborn waves through a variety of clinical presentations including multitrauma patient 18, submersion 19, and exposure to cold weather 20. Endocrinologists can encounter the Osborn wave in certain scenarios. Sheikh and Hurst 21 reported the occurrence of Osborn waves in a patient with diabetic ketoacidosis-induced severe hypothermia. Hypercalcemia is another endocrinal cause for the Osborn waves. Otero and Lenihan 4 reported the occurrence of Osborn waves in a nonhypothermic patient because of hypercalcemia resulting from a parathyroid adenoma. Sridharan and Horan 22 reported the occurrence of Osborn waves in two hypercalcemic patients secondary to malignancy. Hypothermia can also be encountered in patients with anorexia nervosa 23 and malnutrition 24,25. Other endocrinal causes of hypothermia include hypothyroidism, hypopituitarism, and hypoadrenalism. Interestingly, in most instances, the physicians likely to encounter the Osborn wave work in the emergency room, ICU, operating room, or stroke units, rather than as cardiologists. Identification of Osborn waves has several clinical implications. In most instances, it is a marker of severe hypothermia and a sign of overcooling 26 that is associated with various complications including hemodynamic instability. The Osborn wave has a poor prognostic significance, where it is found to be a precursor for the occurrence of ventricular fibrillation 27. The presence of the Osborn wave unaccompanied by shivering artifacts in the surface ECG provides a clue to raise a suspicion for brainstem death in head trauma victims after exclusion of other causes of hypothermia. We aim to emphasize the importance of recognizing the Osborn wave and its implications among the various specialities expected to encounter it and not just cardiologists. Acknowledgements Conflicts of interest There are no conflicts of interest.