What is cardiac pacing?

Cardiac Pacing: Definition and Applications

Cardiac pacing is a therapeutic intervention that uses electrical impulses delivered by electrodes to stimulate heart muscle contraction, primarily to regulate heart rate when the heart's natural pacemaker is not functioning properly or there is a block in the heart's electrical conduction system. 1

Types of Cardiac Pacing

Temporary Pacing

• Used for short-term management of bradyarrhythmias that are expected to resolve, such as those caused by drug effects, electrolyte disturbances, or ischemia 1, 2
• Indicated for symptomatic bradycardia unresponsive to medical therapy, particularly in emergency situations 2
• Methods include:
  • Transcutaneous pacing - non-invasive method using external electrodes, serves as a bridge to more definitive therapy 2
  • Transvenous pacing - involves placement of temporary pacing leads through central venous access 1

Permanent Pacing

• Indicated for chronic, symptomatic bradyarrhythmias that are permanent and irreversible 1
• Involves surgical implantation of a pulse generator and leads that remain in the body 1
• Primary indications include:
  • Sinus node dysfunction (sick sinus syndrome) with symptomatic bradycardia 1, 3
  • Second-degree Mobitz II and third-degree atrioventricular (AV) block 1
  • Symptomatic bradycardia-tachycardia syndrome 3

Pacing Modes

Single Chamber Pacing

• Atrial pacing (AAI/AAIR) - paces and senses in the atrium only 1
• Ventricular pacing (VVI/VVIR) - paces and senses in the ventricle only, typically used in patients with chronic atrial fibrillation 1, 3

Dual Chamber Pacing

• DDD/DDDR - paces and senses in both atrium and ventricle 1
• Maintains atrioventricular synchrony, which improves hemodynamics 1, 3
• Preferred over ventricular pacing as it significantly reduces stroke risk (HR: 0.81) and atrial fibrillation (HR: 0.80) 1, 3

Cardiac Resynchronization Therapy (CRT)

• Biventricular pacing used to treat heart failure patients with ventricular dyssynchrony 1
• Indicated for patients with:
  • Left ventricular ejection fraction (LVEF) ≤35% 1
  • NYHA class III-IV symptoms despite optimal medical therapy 1
  • QRS duration ≥120 ms (particularly with left bundle branch block) 1, 3

Clinical Benefits of Cardiac Pacing

• Prevents recurrence of syncope in patients with symptomatic bradyarrhythmias 1
• Improves survival in patients with high-degree AV block 1
• Reduces stroke and atrial fibrillation risk with atrial-based pacing compared to ventricular pacing 1, 3
• Improves symptoms, exercise capacity, and quality of life in heart failure patients with CRT 1
• Can improve hemodynamics in specific conditions like hypertrophic obstructive cardiomyopathy through strategic right ventricular apical pacing 3

Technical Aspects and Follow-up

• Pacemaker implantation requires surgical asepsis to prevent infection 1
• Modern pacemakers are externally programmable to optimize pacing modes for individual patients 1
• Regular follow-up is essential to:
  • Evaluate the patient's clinical condition 1
  • Check device function and battery status 1
  • Optimize programming settings 1
  • Detect and address complications early 1

Common Pitfalls and Caveats

• Failure to recognize reversible causes of bradyarrhythmias before permanent pacemaker implantation 1, 3
• Not considering upgrade to CRT in patients with conventional pacemakers who develop heart failure and LV dysfunction 1, 3
• Relying solely on ECG evidence of capture without confirming mechanical capture during temporary pacing 2
• Inadequate patient education about electromagnetic interference and activity restrictions 3

Cardiac pacing technology continues to evolve with developments including leadless pacemakers, improved physiological sensors, and enhanced remote monitoring capabilities, expanding the therapeutic options for patients with bradyarrhythmias and heart failure 3.