# Cardiac Pacemaker Indications > Cardiac pacemaker indications for NEET-PG Medicine covering class I criteria for permanent pacing, the NBG code, MCQ-tested modes and complications. - Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/cardiac-pacing-indications - Exam / course: NEET-PG · Subject: Medicine - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-08 - Last updated: 2026-10-08 - Reference basis: Braunwald's Heart Disease; Harrison's Principles of Internal Medicine; Hurst's The Heart - How to cite: "Cardiac Pacemaker Indications", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/cardiac-pacing-indications ## Direct answer Cardiac pacemakers are indicated for symptomatic bradycardia that cannot be reversed, most importantly symptomatic sinus node dysfunction and symptomatic second or third degree AV block. Complete heart block with a slow or unreliable escape rhythm qualifies even without symptoms, as does bradycardia after AV node ablation. Dual chamber pacing, written DDD, is usually preferred when AV conduction is the problem and the sinus node works. ## What you must remember - **Symptomatic bradycardia:** sinus node dysfunction with chronotropic incompetence, symptomatic type II second degree or third degree AV block, and slow atrial fibrillation with symptoms. - **Asymptomatic block:** complete heart block with a slow or unreliable escape rhythm is a class I indication even without symptoms. - **Mobitz I:** Wenckebach block at the AV node is usually benign, and pacing is reserved for symptomatic or high-grade cases. - **Resynchronisation:** LVEF of 35 per cent or less, sinus rhythm, LBBB with QRS of 150 ms or more, and NYHA class II to IV on optimal therapy. - **NBG code:** chamber paced, chamber sensed, response to a sensed event, rate modulation, then multisite pacing. - **Common modes:** VVI for atrial fibrillation with a slow ventricular response, AAI with intact AV conduction, DDD for AV block with a working sinus node, and DDDR when rate must follow activity. - **Complications:** pneumothorax, pocket haematoma, infection, lead dislodgement, perforation with tamponade, and pacemaker syndrome after loss of AV synchrony. ## Choosing a mode for a dizzy patient A 72-year-old woman has repeated presyncope, with a heart rate of 36 and regular P waves that do not conduct to the ventricles. 1. **Exclude reversible causes:** Digoxin, beta-blockers and calcium channel blockers are stopped and electrolytes corrected. 2. **Confirm the block persists:** If the block persists and the symptoms are real, the mode depends on where conduction fails. 3. **Choose dual chamber for AV block:** The P waves are regular and the AV block is complete, so the sinus node is working and dual chamber pacing restores AV synchrony. 4. **Avoid VVI here:** DDD is chosen over VVI because VVI removes atrial contribution, producing pacemaker syndrome with fatigue, neck pulsations and hypotension. 5. **Consider AAI for sinus pauses:** A patient with sinus pauses but normal AV conduction suits AAI, which keeps a physiological AV interval, although the risk of later AV block makes DDD the more common choice in many centres. 6. **Use VVI for atrial fibrillation:** Atrial fibrillation with a slow ventricular response needs VVI or VVIR, because there are no organised atrial beats to track. ## Where the mode question is decided The rhythm details in the stem decide the mode, which is what the examiner is testing. - **Trap:** choosing a pacing mode from the diagnosis label. — **Correct:** sinus node disease and AV block can coexist, so the conduction story decides the mode. - **Trap:** expecting the same magnet response from a pacemaker and an ICD. — **Correct:** a magnet over a pacemaker usually produces asynchronous pacing, whereas over an ICD it suspends tachycardia therapy while bradycardia pacing continues. - **Trap:** confusing LBBB with RBBB and forgetting the 150 ms threshold. — **Correct:** resynchronisation needs LBBB with QRS of 150 ms or more, so a wide left bundle pattern with an ejection fraction of 30 per cent should be assessed for resynchronisation rather than offered a standard pacemaker. - **Trap:** missing pacemaker syndrome after VVI. — **Correct:** a patient who feels worse on VVI than before implantation may have pacemaker syndrome, which is usually treated by converting to a dual chamber system. ## Frequently asked questions ### Why is Mobitz type II block an indication for pacing when Mobitz type I is not? Symptomatic Mobitz type II second degree AV block is a class I indication for permanent pacing because it can progress suddenly to complete heart block. Mobitz type I Wenckebach block, by contrast, is usually benign and rarely needs a pacemaker. ### What does the NBG code mean? The NBG code has five positions: the chamber paced, the chamber sensed, the response to a sensed event, rate modulation and multisite pacing. For example, DDDR paces and senses both chambers, responds by inhibition or triggering, and varies rate with activity. ### Which pacing mode suits atrial fibrillation with a slow ventricular response? VVI or VVIR is used for atrial fibrillation with a slow ventricular response, since there are no organised atrial beats for an atrial lead to track. The R suffix adds rate response when the heart rate does not rise with activity. ### What is pacemaker syndrome? Pacemaker syndrome is a constellation of fatigue, dizziness, neck pulsations and hypotension caused by loss of AV synchrony, most often after VVI pacing. It is usually treated by converting to a dual chamber system. ### How does a magnet affect a pacemaker and an ICD differently? A magnet over a pacemaker usually triggers asynchronous pacing, whereas over an ICD it suspends shock therapy while leaving bradycardia pacing intact. Checking the device type before applying a magnet is therefore essential.