A cardiac device check refers to the assessment and evaluation of implanted cardiac devices, such as implantable loop recorders (ILRs), pacemakers (PPMs), implantable cardioverter defibrillators (ICDs) and cardiac resynchronisation therapy (CRT) devices.
These checks are typically performed by Cardiac Physiologists with a specialist interest in cardiac devices. These devices should be checked regularly – typically on a 12-month basis, this can be different depending on individual circumstances.
Different types of cardiac devices include:
Implantable loop recorder (ILR)
ILRs are tiny ECG recorders which are implanted underneath the skin around the chest wall area. The device contains sensors, which can continuously monitor the ECG, helping detect and diagnose intermittent arrhythmias, which cannot be recorded via other tests (such as 12-Lead ECG or Holter monitors).
Patients who have occasional palpitations, dizzy spells, loss of consciousness or even a transient ischaemic attack (TIA) without any identifiable cause may benefit from an ILR. The device is programmed with certain parameters, which will automatically record any rhythm which meets these parameters, as well as having a ‘symptom activator’ which allows the patient to let us know when they’re symptomatic, so we can identify if their ECG is affected or not.
Permanent pacemaker (PPM)
A pacemaker is an electrical device, comprised of a generator that sits under the skin, connected to 1 or 2 leads, which pass through a vein and go directly into the heart, resulting in the top and/or bottom chambers of the heart being sensed or paced. A leadless pacemaker is a small device which is implanted directly into the bottom chamber of the heart, the ventricle, to stimulate it.
Pacemakers are implanted to treat abnormal rhythms that can cause the heart to beat too slowly or miss beats. PPMs result in symptom improvement, such as alleviating shortness of breath and dizziness, as well as an improvement in life expectancy for patients with conduction issues.
Implantable cardioverter defibrillator (ICD)
An ICD is a device that can detect and treat life-threatening arrhythmias, such as ventricular tachycardia or ventricular fibrillation. The device can treat these arrhythmias by rapid pacing (delivering a burst of anti-tachycardia pacing (ATP)) or by delivering an electric shock to the heart, stunning the heart to restore normal rhythm (defibrillation/shock). These devices can also provide the same function as a pacemaker, by preventing slow heart rates.
There are 2 main types of ICDs:
transvenous ICD – comprised of a generator that sits under the skin, connected to 1 or 2 leads, which pass through a vein and go directly into the heart, resulting in the bottom (and top if required) chambers of the heart being sensed or paced, with the lead in the bottom chamber able to deliver the therapies
subcutaneous ICD – comprised of a generator that sits on the side of the chest, under the left arm, with a lead buried under the chest, going from the device to the middle of the chest (not in the heart)
ICDs can improve the life expectancy in patients who have suffered a dangerous heart rhythm (secondary prevention) and in those who are at risk of a dangerous arrhythmia but have not yet had it (primary prevention).
Cardiac resynchronisation therapy (CRT)
A CRT device is implanted to improve the coordination of the heart’s contractions, making it beat more efficiently. This device is quite similar to a pacemaker; however can have 2 or 3 leads. The extra lead helps both bottom chambers pump simultaneously. This ultimately leads to an improvement in heart function and reduces the symptoms of heart failure over time.
This device can either be in the form of a pacemaker, or a defibrillator (called CRT-P and CRT-D, respectively).
