Related Subjects:
|Classical Ventricular Tachycardia
|Idiopathic Ventricular Tachycardia
|Ventricular Fibrillation
|Resuscitation - Adult Tachycardia Algorithm
|Resuscitation - Advanced Life Support
|Atrial Flutter
|Atrial Fibrillation
|Pacemakers
|Wolff-Parkinson White syndrome (WPW)
|Supraventricular Tachycardia (SVT)
💡 Students often get confused about pacemaker coding. Remember: the paced chamber always comes first - without a paced chamber, it’s not truly a pacemaker.
⚠️ True pacemaker malfunction is rare; pseudo-malfunction (misinterpreting pacing artefacts, undersensing, or oversensing) is far more common.
🔧 About Pacemaker Codes
- A pacemaker has a pulse generator + pacing leads.
- Leads usually pass through the venous system and attach to the endocardium by screw or tine fixation.
- Some are epicardial leads, sewn or screwed onto the heart surface during surgery.
- ⚡ Standard dual-chamber pacemaker = RA lead + RV lead. (Dual-chamber ICD adds a defibrillator coil in RV).
- ❤️🔥 Biventricular pacing (CRT) uses 3 leads (RA, RV, LV via coronary sinus) → restores synchrony, improves haemodynamics, relieves heart failure symptoms.
- 🔁 Dual chamber devices can be programmed for triggered pacing (sense in atrium → pace ventricle after a delay).
📊 NBG Pacemaker Codes
- Written in a 5-letter code (chamber paced ➝ chamber sensed ➝ response ➝ programmability ➝ anti-tachy function).
- Example: DDDR = Dual-chamber paced, Dual-chamber sensed, Dual response, Rate modulated.
- Historic codes & detail: NASPE
Chambers Paced
1 |
Chambers Sensed
2 |
Mode of Response
3 |
Programmable Functions
4 |
Anti-Tachycardia
5 |
| V = Ventricle | V = Ventricle | T = Triggered | R = Rate Modulated | O = None |
| A = Atrium | A = Atrium | I = Inhibited | C = Communicating | P = Paced |
| D = Dual (A&V) | D = Dual (A&V) | D = Dual (T+I) | M = Multi-programmable | S = Shocks |
| O = None | O = None | O = None | P = Simple programmable | D = Dual (P+S) |
| --- | --- | --- | O = None | --- |
🩺 Pacemaker Types
| Type | Indications | Notes |
|---|
| Single-Chamber (AAI or VVI) |
- AAI: Sinus node disease with intact AV conduction.
- VVI: Chronic AF with bradycardia or AV block.
|
- One lead (RA or RV).
- ✅ Simple, fewer complications.
- ❌ No AV synchrony.
|
| Dual-Chamber (DDD) |
- AV block (2° or 3°).
- Sinus node dysfunction + bradycardia.
- Maintains AV synchrony.
|
- Two leads (RA + RV).
- Better haemodynamics than single-chamber.
- Most common modern pacemaker.
|
| Biventricular (CRT) |
- Heart failure + reduced EF.
- Wide QRS / LBBB + persistent symptoms (NYHA II–IV).
|
- Leads in RA, RV, + LV via coronary sinus.
- Resynchronises ventricles → ↑ CO.
- Improves survival & QOL in HFrEF.
|
| Leadless Pacemaker |
- Symptomatic bradycardia.
- High infection risk or venous access issues.
|
- Implanted directly in RV.
- Lower infection/lead complications.
- ❌ Limited to VVI pacing.
|
| ICD with Pacing |
- High SCD risk (e.g., VT/VF, post-MI, low EF).
- Also manages bradycardia.
|
- Defibrillator + pacing in one device.
- Delivers shocks & prevents bradyarrhythmias.
- Regular follow-up needed.
|
⏱️ Hysteresis
- Allows heart to use intrinsic rhythm → conserves battery.
- Set below base rate (e.g., Base 60, Hysteresis 50 → no pacing until HR < 50, then pace at 60).
- Useful for physiologic rate changes (e.g., slower HR during sleep).
⚙️ Pacemaker Insertion
- 📋 Pre-op: Hx, exam, ECG, echo, bloods, informed consent.
- 💉 Antibiotic prophylaxis (e.g., cefazolin).
- 🔪 Pocket created under clavicle; leads placed via subclavian/cephalic vein.
- ⚡ Leads tested & generator implanted in pocket.
- ✅ Pacemaker programmed & wound closed.
🛡️ Post-Procedure Care
- Monitor on telemetry.
- CXR → confirm leads & exclude pneumothorax.
- Wound care & infection precautions.
- Restrict arm movement/lifting for several weeks.
⚠️ Complications
- Infection (pocket/endocarditis).
- Lead displacement.
- Pneumothorax (venous access).
- Bleeding/hematoma.
- Pacing failure (over/undersensing).
- Venous thrombosis (rare).
📍 Indications – Temporary Pacing
- Asystole or complete heart block.
- Severe bradycardia with haemodynamic compromise.
- Bradycardia-dependent arrhythmias (e.g., Torsades).
- Overdrive pacing for VT, AF, flutter.
- Acute MI + 2°/3° heart block.
📍 Indications – Permanent Pacing
- Symptomatic bradycardia (syncope, fatigue).
- 2° or 3° AV block.
- Sick sinus syndrome.
- AF with slow ventricular response.
- HFrEF + ventricular dyssynchrony → CRT.
- Post-MI conduction disturbance.
🩺 Immediate / Procedural Complications
- 🩸 Bleeding or haematoma at the generator pocket (more common in anticoagulated patients).
- 💨 Pneumothorax from subclavian vein puncture.
- 🫁 Haemothorax due to vascular injury.
- 💔 Cardiac perforation by the pacing lead → may cause pericardial effusion or tamponade.
- 🫀 Arrhythmias during lead placement (e.g., ventricular ectopics or VT).
- 🧠 Air embolism (rare).
- 🦠 Early infection of the pocket or wound.
⏱️ Early Post-Procedure Complications
- 🔌 Lead displacement (most common early complication) → loss of capture or sensing failure.
- 📉 Failure to capture due to lead position or rising pacing threshold.
- ⚡ Oversensing or undersensing leading to inappropriate pacing.
- 🦠 Pocket infection or cellulitis.
- 🫀 Pericardial effusion following lead perforation.
- 🫁 Delayed pneumothorax.
📅 Late Complications
- 🦠 Device infection or lead endocarditis.
- 🔧 Lead fracture or insulation failure.
- 🔌 Lead dislodgement (late migration).
- 🧲 Pacemaker syndrome (AV dyssynchrony causing fatigue, dizziness, hypotension).
- ⚡ Pacing-induced cardiomyopathy due to chronic right ventricular pacing.
- 🫀 Tricuspid regurgitation from lead interference with the valve.
- 🧠 Venous thrombosis or superior vena cava obstruction.
⚠️ Rare but Recognised Problems
- 📦 Generator erosion through the skin.
- 🫀 Twiddler’s syndrome (patient rotates the device → lead displacement).
- 🔋 Battery depletion or device malfunction.
- 📡 Electromagnetic interference affecting device function.
📚 Exam tip: Learn the common codes (VVI, AAI, DDD, DDDR, CRT).
True malfunction is rare → always rule out pseudo-malfunction first (lead displacement, oversensing, battery depletion).
