Diagnostics

In the context of cardiac devices, diagnostics refers to the data stored and reported by an implantable cardioverter defibrillator (ICD) or pacemaker that records the patient’s cardiac rhythm, device activity, and the delivery of any therapies. This stored information is reviewed at each device clinic appointment and via remote monitoring to evaluate how the heart has been behaving and whether the device is functioning as intended.

Devices typically store: heart rate histograms (showing the distribution of heart rates over time); detected arrhythmia episodes with the accompanying electrogram (the electrical signal recorded from within the heart); any therapies delivered (pacing, anti-tachycardia pacing, or shocks); and device-specific parameters such as battery voltage, lead impedance, and sensing and pacing thresholds.

Diagnostics are reviewed to assess: whether any arrhythmias have occurred (including episodes the patient may not have felt); whether device therapies were appropriate or inappropriate; whether any device parameters have drifted outside normal ranges (which can indicate lead problems, battery depletion, or changing cardiac physiology); and whether medications or device settings need to be adjusted.

For cardiac arrest survivors with ICDs, device diagnostics provide a continuous record of the heart’s electrical behaviour. ICD-detected arrhythmia episodes and the appropriateness of shocks delivered are particularly important information. Modern remote monitoring systems transmit device diagnostics to the device clinic automatically, allowing early detection of problems without requiring the patient to attend in person.