BACKGROUND TO CARDIAC IMPLANTABLE ELECTRONIC DEVICES
Cardiac rhythm management (CRM) is the treatment of arrhythmias. Arrhythmias can cause a range of symptoms including palpitations, dizzy spells, blackouts, and sudden cardiac arrest. Contemporary management of arrhythmia may involve cardiac implantable electronic devices (CIEDs) and catheter ablation.1
CIEDs are used to manage slow and fast heart rates, and in the treatment of selected patients with heart failure. Types of CIED include permanent pacemakers (PPMs), implantable cardioverter defibrillators (ICDs), and cardiac resynchronisation therapy (CRT) devices. CIEDs are usually implanted under the skin, with one to three leads threaded down a vein to connect to the heart.1
PPMs: types and what they do
PPMs monitor the heart rate and, when necessary, give tiny electrical impulses to trigger the heartbeat. The leads may be implanted in the right atrium, the right ventricle (single-chamber device), or both (dual-chamber device; see Figure 1).
ICDs can deliver life-saving therapy in the form of anti-tachycardia pacing (ATP) or shocks within seconds of detecting the abnormal rhythm to restore normal rhythm. They may be placed prophylactically in patients at increased risk of arrhythmias (primary prevention) or in those who have had a life-threatening arrhythmia (secondary prevention). Most ICDs have pacing functionality in addition to ATP and shocks.
CRT devices are used in patients with heart failure due to weak and/or poorly coordinated ventricles. This usually manifests as a bundle branch block on a 12-lead electrocardiogram. CRT devices pace the left ventricle (via the coronary sinus) in addition to the right ventricle, to improve the coordination of the heartbeat and thus ‘synchronising’ the heart. CRT can be a feature of both pacemakers (CRT-P) and defibrillators (CRT-D).
Pacing codes
Pacemakers are coded to inform the user how they work and what they do. This code consists of:
first letter — chamber paced (A = atria, V = ventricle, and D = dual);
second letter — chamber sensed;
third letter — response to sensed event (inhibited/dual); and
fourth letter — rate response (R).
Figure 1. X-ray images showing dual-chamber pacemaker (left image) and dual-chamber implantable cardioverter defibrillator (right image). © Medtronic, Inc., used with permission.
Figure 2. Graphic and X-ray visualisation of leadless pacemaker. © Medtronic, Inc., used with permission.
For example, DDDR = dual leads (atria and ventricle), both chambers sensed, both chambers respond to sensed events, and can adapt rate to changes in the patient’s physical activity.
A disadvantage of conventional CIEDs is the need for one or more leads to pass down a vein from the device (placed under the skin below the collarbone) to the chambers of the heart. Occasionally there may be challenges with venous access (for example, dialysis-dependent patients and indwelling lines) that may preclude their use. Rarely, these can become damaged or infected,2–5 necessitating their replacement. Removal of existing leads can be difficult and risky because they become bound to the veins and heart by scar tissue.
Figure 3. Graphic and X-ray visualisation of subcutaneous implantable cardioverter defibrillator. © Boston Scientific, used with permission.
NEWER TECHNOLOGIES
Leadless pacemakers
These directly attach to the inside of the right ventricle (Figure 2), avoiding the need for leads paced within the vein, with significantly lower risk of infection.6
The device is implanted via the femoral vein using a catheter delivery system.
Leadless devices currently lack atrial-based pacing and cardiac resynchronisation, but the latest version can sense atrial contraction and thus provide AV synchrony. Devices with atrial-based pacing are currently in trials, allowing for dual-chamber pacing in the future.
Subcutaneous implantable cardioverter defibrillators
Subcutaneous implantable cardioverter defibrillators (SICD) were introduced for patients at risk of sudden cardiac death with no requirement for pacing, that is, solely for defibrillation shocks. They are used in the same manner as a transvenous ICD.
All components of this device are under the skin but outside the ribcage (Figure 3).
CIED FOLLOW-UP
All patients with a CIED in situ are routinely under follow-up with a pacemaker/ICD/device clinic to ensure appropriate programming and satisfactory working of the CIED.
Some patients may additionally have a ‘remote monitor’ that allows communication with the device without requiring face-to-face follow-up.7 Remote monitoring is performed via a secure web-based platform. It has evolved to automatic data acquisition on a frequent basis with unscheduled transmission of predefined alerts to the CIED provider (device clinic). These alerts can include information and warnings about device and lead integrity, programming issues, or physiological data such as abnormal heart rates or rhythms, or risk of heart failure deterioration.
COMPLICATIONS
CIED complications can present immediately post-procedure or at a later stage. Those presenting early are often related to the procedure itself and include:
pneumothorax related to venous access;
cardiac perforation at the time of the procedure or due to later lead movement (related to helix of the lead);
pocket haematomas due to peri-procedural anticoagulation or poor surgical technique;
displacement of pacemaker/defibrillator lead requiring repositioning/replacement;
retained stitch or superficial infection; and
infection requiring system explant.
These are often detected while the patient is an inpatient but can manifest at a later stage and so may present to primary care.
CIED ISSUES IN PRIMARY CARE
Patient with a CIED in situ presents with syncope
Causes for this can include:
arrhythmias, which may be picked up on interrogation of CIED; and
CIED malfunction due to lead or generator issues — if the lead is damaged it can pick up noise that can lead to inappropriate inhibition of pacing resulting in bradycardia. Battery issues can cause failure to pace appropriately, resulting in bradycardia.
It is best to refer the patient back to the clinic where the CIED can be interrogated and the problem identified.
Depending on the presentation and history, other conditions such as malignant vasovagal syncope, orthostatic hypotension, and neurological causes may need to be explored.
Patient with a CIED in situ presents with discomfort
Infection is one of the most serious complications of CIED therapy and is associated with significant mortality, morbidity, and financial healthcare burden. Incidence of infection was estimated at 4.82/1000 device–years after primary implantation, and 12.12/1000 device–years after replacement.2–5
Superficial infection limited to the surgical suture line may be cautiously treated with a short course of antibiotics. The patient should be kept under review until the infection resolves; otherwise, if the wound is not settling, it should be escalated without delay.
Pocket infection is defined as infection limited to the generator pocket. It is associated with local signs of inflammation that may be mild and characterised by erythema, warmth, and fluctuation. Deformation of the pocket, adherence, or threatened erosion are often signs of low-grade, indolent infection.
The GP should refer to the device clinic if this is suspected. It is not recommended to take a sample of pocket material. Bloods, including blood cultures and a C-reactive protein (CRP), should be considered if infection is suspected prior to commencing antibiotic therapy.
Patient with a CIED in situ presents with an unexplained pyrexia
The diagnosis of CIED systemic infection and infective endocarditis without local infection may be more challenging. Symptoms may be non-specific (fever, chills, or night sweats) and a long period of time may elapse between CIED implantation and symptom onset and diagnosis.
CRP may be helpful, although non-specific. Identification of the causative microorganisms for a CIED infection is pivotal for effective antibiotic therapy. Blood cultures should be obtained prior to the institution of antibiotic therapy. GPs should have a high index of suspicion and refer to a pacing centre.
SUMMARY: KEY POINTERS FOR PRIMARY CARE
Not all syncope and presyncope following pacemaker implant will be due to arrhythmia. GPs should request device interrogation from their local implant centre if in doubt.
GPs should consider CIED infection with persistent pyrexia, especially of unknown origin.
Discomfort over the device, especially if new onset, can be a sign of pocket infection or migration. GPs should request advice from the local implant centre.
GPs should consider simple bloods: full blood count (FBC) and CRP.
Notes
Provenance
Freely submitted; externally peer reviewed.
Competing interests
Archana Rao has received honoraria from Medtronic, Boston Scientific, and Phillips for educational sessions undertaken. Stuart Bennett has received an honorarium from Medtronic for a webinar presentation.
Discuss this article
Contribute and read comments about this article: bjgp.org/letters
- Received March 24, 2022.
- Revision requested April 25, 2022.
- Accepted May 9, 2022.
- © British Journal of General Practice 2022
REFERENCES
- 1.↵
- 2.↵
- 3.
- 4.
- 5.↵
- 6.↵
- 7.↵