Cardiac pacemaker

Purpose: a permanent pacemaker delivers electrical stimuli to maintain an adequate heart rate and, where possible, atrioventricular synchrony, in symptomatic bradyarrhythmia.

Nomenclature (NBG code): position 1 = chamber paced, 2 = chamber sensed, 3 = response to sensing, 4 = rate modulation (R). Thus VVI = ventricle paced/sensed/inhibited; AAI = atrium only; DDD = dual chamber; DDDR = dual chamber with rate response.

Indications — sinus node dysfunction: symptoms directly attributable to sinus node dysfunction (Class I); bradycardia from clinically necessary guideline-directed therapy (Class I); tachy-brady syndrome with symptomatic bradycardia (Class IIa); rate-responsive pacing for symptomatic chronotropic incompetence (Class IIa).

Indications — AV block: acquired complete heart block regardless of symptoms and acquired second-degree Mobitz type II regardless of symptoms, once reversible and physiological causes are excluded (both Class I); any degree of block with neuromuscular disease such as myotonic dystrophy type 1 or Kearns-Sayre syndrome (Class I); symptomatic Mobitz type I (Class IIa); unresolving advanced block after cardiac surgery or AV junction ablation (Class I). First-degree block is generally benign, but a PR interval >240–300 ms with left bundle branch block and lamin A/C mutation, or with attributable symptoms, may warrant pacing (Class IIa).

Choice of mode: DDD pacing is recommended over AAI or VVI when permanent pacing is needed for sinus node disease or AV block (Class I). Single-chamber VVI is appropriate when frequent ventricular pacing is not expected or when comorbidities limit the benefit of dual-chamber pacing (Class I). An atrial lead should not be implanted in permanent or persistent AF when rhythm control is not planned (Class III).

Evidence base: meta-analysis of CTOPP, MOST, UKPACE and related trials showed no mortality difference and no difference in new or worsening heart failure between physiological and ventricular pacing, but a significant reduction in new-onset atrial fibrillation with an atrial lead, and a borderline reduction in thromboembolic stroke. Cross-over studies showed better functional capacity and patient preference for dual-chamber pacing; active patients over 70 gain quality-of-life benefit from DDD pacing.

Pacing-induced cardiomyopathy: conventional right ventricular apical pacing causes non-physiological, dyssynchronous left ventricular activation. Patients with pre-existing left ventricular impairment and a high pacing burden may develop heart failure. All patients should have a transthoracic echocardiogram before pacemaker implantation.

Physiological pacing options: CRT (biventricular) adds a lead activating the lateral LV wall — the BLOCK HF trial showed about a 30% reduction in heart failure hospitalisation versus RV pacing in patients with reduced LV function and AV block. His bundle pacing and left bundle branch area pacing achieve a narrow paced QRS with near-normal ventricular contraction.

Complications: pneumothorax, cardiac perforation and tamponade, lead displacement, pocket haematoma and infection, device infection or endocarditis (a recognised cause of bradycardia and of infective endocarditis in the elderly), venous thrombosis, pacemaker syndrome (with VVI pacing), tricuspid regurgitation, and generator end-of-life.

Geriatric decision-making: the final choice of device is individualised, taking into account patient preference, comorbidities, life expectancy, dexterity, cognition and available resources — the "cheapest adequate device" is often the right answer in a frail patient, while an active 70-year-old benefits from dual-chamber or physiological pacing. Latest Updates and Current Practice Update (concise) 2023 HRS/APHRS/LAHRS guideline on cardiac physiologic pacing: conduction system pacing carries a Class IIa recommendation for bradycardia indications when LVEF is 35–50% and a substantial pacing burden is anticipated; the 2025 EHRA/ESC clinical consensus extends guidance on patient selection and on hybrid strategies (HOT-CRT, LOT-CRT). Left bundle branch area pacing (LBBAP) has largely overtaken His bundle pacing because of better capture thresholds and lead stability, and registry data show better outcomes than right ventricular pacing; randomised trials such as PROTECT-HF are ongoing. Leadless pacemakers are now routine in selected older patients (no pocket, no leads, lower infection risk); helix-based leadless systems capable of conduction system pacing entered first-in-human study in 2025.