Electrocardiographic spiked-helmet sign in critical non-cardiac illness

The spiked-helmet sign (SHS) is an electrocardiographic finding characterised by a distinctive pattern associated with critical illness, resolving once the clinical condition improves. While the underlying mechanism remains uncertain, different mechanisms have been proposed to account for these findings including changes in intrathoracic or intra-abdominal pressures, transient compression of the coronary arteries, repolarisation abnormalities and electromechanical artefacts. We describe the development of the SHS in a patient with underlying left bundle branch pacing following the development of respiratory failure due to haemoptysis and review proposed mechanisms for its pathophysiology.