The J-wave (Osborn wave) appearing at the QRS-ST junction on ECG is most characteristically associated with:

• A Hyperkalemia causing peaked T-waves and conduction block
• B Hypothermia (core temperature <30°C) due to inhomogeneous early repolarization from augmented transient outward K+ current (Ito) ✓
• C Hypercalcemia causing shortened QT interval and J-waves
• D Brugada syndrome type 1 with right precordial ST elevation

Explanation

The Osborn (J) wave is a positive deflection at the J-point (junction of QRS and ST segment), most prominent in hypothermia when core temperature falls below 32°C and classic at <30°C. The mechanism involves heterogeneous augmentation of the transient outward K+ current (Ito) in ventricular epicardium relative to endocardium at low temperatures. Ito is denser in epicardial cells and accelerates early repolarization there, creating a transmural voltage gradient manifesting as a positive J-wave. J-waves in hypothermia typically appear in inferior and lateral leads. Brugada syndrome also involves Ito but produces a right bundle branch-like pattern; hyperkalemia causes peaked T-waves but not J-waves; hypercalcemia shortens QT but does not produce J-waves.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.