Left axis deviation

Raised intracranial pressure, classically from subarachnoid haemorrhage, can produce deep widespread T-wave inversion (cerebral T waves) with marked QT prolongation and bradycardia, in the absence of coronary occlusion.

Dextrocardia produces inverted P waves in lead I with a negative QRS, reverse R-wave progression across the precordial leads and often a right axis. A similar tracing appears with reversed arm leads, so limb-lead placement must be checked before the diagnosis is made.

Right axis deviation shifts the QRS axis beyond +90 degrees, giving a negative QRS in lead I with a positive QRS in lead III. Common causes include right ventricular hypertrophy, chronic lung disease, pulmonary embolism, lateral infarction and a tall thin body habitus.

Hypothermia slows everything down: bradycardia, prolonged PR, QRS and QT intervals, and the characteristic J (Osborn) wave, a notch at the end of the QRS. Shivering artefact and atrial fibrillation are frequent, and severe cases can progress to ventricular arrhythmias.

Diffuse concave ST elevation with PR depression; no reciprocal changes.

Voltage criteria (Sokolow-Lyon ≥35 mm), often with strain pattern in lateral leads.