Inappropriately Appropriate.

Jackson et al describe a complex timing cycle interaction in a patient with a dual-chamber implantable cardioverter– defibrillator. The intracardiac electrograms provided along with their description of an algorithmic approach to differential diagnosis is ripe with teaching points typical of the bedside rounds of yesteryear. Complex cases require not only meticulous logical analysis of the available data but also detailed knowledge of the background information necessary to apply that reasoning. In this instance, the authors used the morphology of the intracardiac electrograms, the relative timing between ventricular and atrial activation, identifying the initial chamber for the change in the rhythm, along with the background knowledge of specific device timing windows and expected responses, and functional knowledge of the SecureSense lead noise detection algorithm.