The Case

61yo M PMH HTN, AUD, HFpEF, CAD, hypothyroidism, anemia is brought in by EMS after being found down at his shelter in the middle of winter. He was discovered surrounded by empty alcohol bottles and covered in feces. Per shelter staff, the patient was last seen 7 days ago and appeared well at that time. On arrival to the ED, the patient is not responding to questions or commands and is intermittently combative. Vital signs are notable for hypotension with systolic blood pressures in the 70s. He is cold to the touch.

EKG

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EKG Characteristics

  • Rate

    118 bpm

  • Rhythm

    Irregularly irregular rhythm without discernible p-waves

  • Intervals

    Normal PR and QRS, prolonged QTc at 549ms

  • Axis

    Normal Axis

  • ST Segments

    No significant ST elevations or depressions

  • Additional Features

    Positive J-point deflection in leads II, III, aVF, V3, V4

Diagnosis

What Is the Diagnosis?

Hypothermia with Osborne (J) waves

Questions

  1. What is the differential diagnosis for this patient?

    Sepsis, unstable Afib with RVR, myxedema coma, environmental hypothermia, ACS, adrenal insufficiency, alcohol withdrawal

Discussion

Case Discussion:

  • In this case, a temperature-sensing foley was placed on arrival and the patient’s core temperature was noted to be 79 degrees Farenhiet. Active rewarming was initiated with warm IV fluids and patient was placed on the bairhugger warming device. A central line and A-line were placed for central rewarming access and accurate BP management and the patient was admitted to the MICU for refractory shock and continued rewarming.

Osborne (J) Waves

  • Osborne waves are positive deflections at the junction of the QRS complex and ST segment
    • Generally sharp, dome-like appearance as opposed to the slurred or notched
  • J-point (“fish-hook” appearance) of benign early repolarization
  • Most commonly seen in moderate to severe hypothermia (typically <32°C)
  • Often best visualized in inferior and lateral precordial leads
  • Amplitude generally increases as core temperature decreases
  • Presence does not correlate with prognosis, but signals significant hypothermia

Pathophysiology

  • Hypothermia alters myocardial repolarization and creates a transmural voltage gradient between epicardial and endocardial layers which results in the characteristic J-point deflection.

Differential Diagnosis of J Waves

  • Osborne waves are not specific to hypothermia. Other causes include:
  • Hypercalcemia
  • Brugada syndrome
  • Early repolarization
  • Acute neurologic injury (e.g., SAH)
  • Post–cardiac arrest states

Clinical context and core temperature are critical

Management Pearls

  • Treat the patient, not the EKG
  • Hypothermic patients are extremely arrhythmia-prone, especially with rapid electrolyte shifts during rewarming
    • Atrial fibrillation common
    • Ventricular dysrhythmias possible with minimal stimulation
      • Rough handling, intubation, or invasive procedures can precipitate arrest
  • Primary treatment is rewarming
    • Passive external (blankets, warm environment)
    • Active external (forced-air warming)
    • Active internal if severe (warm IV fluids, lavage, ECMO in select cases)
  • Avoid unnecessary movement and invasive procedures
  • Osborne waves may be misread as ST elevation, especially in patients with CAD
  • Bradycardia and atrial fibrillation often resolve with rewarming
    • Aggressive pharmacologic rate control or electrical cardioversion in hypothermic patients can precipitate malignant ventricular arrhythmias. The primary treatment remains correction of the underlying hypothermia.
  • Remember, many medications (such as pressors) may be ineffective until temperature improves

Pearls

  • Osborne (J) waves are a classic ECG finding in moderate to severe hypothermia
  • They appear as dome-like (camel’s hump) elevations at the J-point, not true ST-elevation MI
  • Always interpret ECG findings in clinical and temperature context
  • The definitive treatment is rewarming, not antiarrhythmics or cath lab activation

Sources