ECG and Arrhythmias for NEET PG Medicine: AF, Flutter, SVT, WPW, VT, Torsades, Heart Block, Bundle Branch Block, QT

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🎯 Exam priority: High. Expect: identify a rhythm strip (AF, flutter, Mobitz I vs II, complete block, VT, torsades, WPW), electrolyte effects on QT and T waves, RBBB vs LBBB, adenosine for SVT, what not to give in AF with WPW, and magnesium for torsades.

CBME mapping: ECG competencies within GM 1–2. Infarct ECGs are in article 2; antiarrhythmic drug pharmacology in Pharmacology.

Schematic rhythm strips and ECG clues. Drawn by TrackNation — teaching schematics, not real tracings.

Reading the ECG

• QTc is normally 350–450 ms in men and 360–460 ms in women. Long QT: hypokalaemia, hypomagnesaemia, hypocalcaemia, hypothyroidism, MI, myocarditis, intracranial bleeds, drugs, congenital — and it predisposes to torsades. Short QT: hypercalcaemia, hypermagnesaemia, Graves disease, digoxin.

• Tall T waves: hyperkalaemia, acute MI, LBBB, stroke, ventricular hypertrophy. Absent P waves: AF, sinus arrest, severe hyperkalaemia.

• RBBB: QRS ≥ 0.12 s with rsR′/rSR′ in V1–V2. LBBB: QRS ≥ 0.12 s, broad notched or slurred R and no Q waves in I, aVL, V5–V6.

Tachyarrhythmias

• Atrial fibrillation: rapid, irregularly irregular, no P waves, fibrillatory waves. Atrial thrombi → embolic stroke; risk higher with age, moderate–severe mitral stenosis, mechanical valve, hyperthyroidism, hypertension, diabetes, LV dysfunction, prior embolism. Treatment: rate control, anticoagulation, sometimes rhythm conversion. Amiodarone if beta-blockers, non-DHP CCBs and digoxin fail.

• Atrial flutter: sawtooth waves in II, III, aVF; atria ~300/min with 2:1 block → regular ventricular rate 150.

• Reentrant SVT: starts and stops suddenly; AVNRT is the commonest. Vagal manoeuvres first, then IV adenosine or a non-dihydropyridine CCB. WPW: short PR and delta wave (pre-excitation) with paroxysmal tachycardia; AVRT is the usual tachycardia in WPW.

• AF with WPW: digoxin, adenosine, verapamil and diltiazem are dangerous; cardiovert, or use IV procainamide or ibutilide.

• Ventricular tachycardia: ≥ 3 consecutive ventricular beats at ≥ 120/min; sustained if ≥ 30 s. Any wide-QRS tachycardia is VT until proved otherwise. Cardioversion or antiarrhythmics; ICD long term.

• Torsades de pointes: polymorphic VT twisting around the baseline on a long QT; risks include female sex, age, hypokalaemia, hypomagnesaemia, slow heart rate. Give IV magnesium. VF: immediate syncope; CPR with immediate defibrillation.

Bradyarrhythmias and Blocks

• Complete heart block shows AV dissociation: cannon a waves, fluctuating BP, variable S1. In adults 18–60 with new Mobitz II or complete block and no obvious heart disease, up to a third have cardiac sarcoidosis.

• ICMR bradyarrhythmia workflow: look for reversible causes — beta-blockers, calcium channel blockers, digoxin, electrolytes, thyroid; permanent pacing for complete heart block and advanced AV block, and for symptomatic sinus node dysfunction.

• Antiarrhythmics are grouped into four Vaughan Williams classes (details in Pharmacology).

Traps the Examiner Sets

• Mobitz I: PR grows then drops; Mobitz II: PR fixed then drops.

• Regular narrow tachycardia at exactly 150 → think flutter with 2:1 block.

• AF + WPW: no AV-nodal blockers.

• Hypercalcaemia shortens QT; hypocalcaemia lengthens it.

• Torsades: magnesium, not amiodarone.

Memory Hooks & Shortcuts

Shortcuts to lock in this article's numbers and lists. Each one only re-packages facts proven above.

• 🧠 Mobitz I = 'longer, longer, longer, drop — now you've got Wenckebach' — Mobitz I

• 🧠 Flutter at 150 — '300 halved' — flutter

• 🧠 WPW + AF: no ABCD (Adenosine, Beta-blocker/CCB, Digoxin) — AF with WPW

• 🧠 Torsades → Mg first ('twist the magnesium cap') — torsades

• 🧠 Calcium high → QT short (Ca up, QT down) — QT and calcium

• 🧠 RBBB = Rabbit ears (rSR′) in V1 — RBBB

Rapid-Revision Cards

• AF ECG

  No P, f waves, irregularly irregular.

• AF main risk

  Embolic stroke.

• AF rate control

  Beta-blocker, non-DHP CCB, digoxin; then amiodarone.

• Flutter

  Sawtooth II, III, aVF; atria ~300; 2:1 → 150.

• Commonest PSVT

  AVNRT.

• SVT treatment

  Vagal → IV adenosine / non-DHP CCB.

• WPW

  Short PR + delta wave; AVRT.

• AF + WPW avoid

  Digoxin, adenosine, verapamil, diltiazem.

• AF + WPW give

  Cardioversion or IV procainamide/ibutilide.

• VT definition

  ≥ 3 beats ≥ 120/min; sustained ≥ 30 s.

• Wide-QRS tachycardia

  VT until proved otherwise.

• VF

  CPR + immediate defibrillation.

• Torsades

  Twisting QRS, long QT; IV magnesium.

• Long QT causes

  Low K, Mg, Ca; hypothyroid; drugs; congenital.

• Short QT causes

  High Ca, high Mg, digoxin.

• Tall T waves

  Hyperkalaemia, acute MI, LBBB.

• RBBB

  rSR′ in V1–V2; QRS ≥ 0.12.

• LBBB

  Broad notched R, no Q in I, aVL, V5–V6.

• 1st-degree block

  PR > 0.20 s.

• Mobitz I

  PR lengthens → drop.

• Mobitz II

  Fixed PR → drop.

• Complete block

  AV dissociation; cannon a waves.

• New CHB age 18–60

  Think cardiac sarcoidosis.

Sources

Facts in this article were checked against these documents.

• MSD Manual Professional: Electrocardiography; Overview of Arrhythmias; Atrial Fibrillation; Atrial Fibrillation and WPW; Atrial Flutter; Reentrant PSVT; Ventricular Tachycardia; Ventricular Fibrillation; Long QT and Torsades; AV Block; Bundle Branch Block; Medications for Arrhythmias — Merck & Co. (MSD Manuals), reviewed 2024–26 (link)

• Standard Treatment Workflow: Bradyarrhythmias in Symptomatic Patients — ICMR / Department of Health Research, MoHFW, 2022–26

• Competency Based Undergraduate Curriculum, General Medicine (GM 1–2) — National Medical Commission, 2024

Test Yourself: Practice Questions

Thirty questions in NEET PG style, most of them clinical vignettes and ECG descriptions.

Practice Questions (NEET PG pattern)

Original questions written in the style of the exam: +4 for a correct answer, −1 for a wrong one. Every answer was checked against the sources listed above. NEET PG papers are not published by NBEMS, so these are not past-paper questions.

Q1. A 70-year-old has palpitations; ECG shows no P waves, a wavy baseline and an irregularly irregular ventricular rhythm. The main risk to prevent is

• (a) embolic stroke

• (b) complete heart block

• (c) pericarditis

• (d) torsades de pointes

Q2. Which condition raises stroke risk in atrial fibrillation most among these?

• (a) low BMI

• (b) young age

• (c) moderate to severe mitral stenosis

• (d) normal LV function

Q3. First-line drugs for long-term rate control in atrial fibrillation include

• (a) beta-blockers, non-dihydropyridine CCBs or digoxin

• (b) adenosine

• (c) atropine

• (d) lidocaine

Q4. A regular narrow-complex tachycardia at exactly 150/min with sawtooth waves in II, III and aVF is

• (a) sinus tachycardia

• (b) AVNRT

• (c) atrial flutter with 2:1 block

• (d) VT

Q5. A young woman has palpitations that start and stop suddenly; ECG shows a regular narrow-complex tachycardia at 190/min. Vagal manoeuvres fail. Next drug is

• (a) IV digoxin

• (b) IV adenosine

• (c) IV amiodarone

• (d) oral warfarin

Q6. The commonest type of paroxysmal supraventricular tachycardia is

• (a) junctional ectopic tachycardia

• (b) AV reentrant via an accessory pathway

• (c) AV nodal re-entry

• (d) atrial flutter

Q7. A resting ECG shows a short PR interval and a slurred upstroke of the QRS in a patient with episodes of tachycardia. The diagnosis is

• (a) hyperkalaemia

• (b) Wolff-Parkinson-White syndrome

• (c) LBBB

• (d) first-degree AV block

Q8. A patient with known WPW develops a fast irregular broad-complex tachycardia (AF with pre-excitation). Which drug must be avoided?

• (a) ibutilide

• (b) none — cardioversion is contraindicated

• (c) procainamide

• (d) verapamil

Q9. In AF with WPW where cardioversion cannot be done, the preferred drug is

• (a) IV digoxin

• (b) IV procainamide or ibutilide

• (c) IV adenosine

• (d) IV diltiazem

Q10. Ventricular tachycardia is defined as

• (a) ≥ 3 consecutive ventricular beats at ≥ 120/min

• (b) a narrow-complex tachycardia

• (c) any wide QRS beat

• (d) ≥ 10 beats at ≥ 200/min

Q11. A haemodynamically stable patient has a regular wide-QRS tachycardia (QRS 0.16 s). It should be treated as

• (a) atrial flutter

• (b) ventricular tachycardia until proved otherwise

• (c) sinus tachycardia

• (d) SVT with aberrancy

Q12. VT lasting 20 seconds that stops by itself without collapse is classed as

• (a) torsades

• (b) sustained VT

• (c) non-sustained VT

• (d) VF

Q13. A collapsed patient has a chaotic ECG with no identifiable QRS complexes and no pulse. The key immediate treatment is

• (a) synchronised cardioversion at low energy

• (b) CPR with immediate defibrillation

• (c) atropine

• (d) IV adenosine

Q14. A woman on a QT-prolonging drug with low potassium develops a polymorphic VT whose QRS axis twists around the baseline. First-line drug is

• (a) IV magnesium

• (b) IV digoxin

• (c) IV procainamide

• (d) IV amiodarone

Q15. Which electrolyte abnormality shortens the QT interval?

• (a) hypocalcaemia

• (b) hypokalaemia

• (c) hypercalcaemia

• (d) hypomagnesaemia

Q16. A patient's ECG shows tall T waves without chest pain. The electrolyte cause to check first is

• (a) hyperkalaemia

• (b) hypercalcaemia

• (c) hypokalaemia

• (d) hypothermia

Q17. Normal QTc in adult women is about

• (a) 360–460 ms

• (b) 200–300 ms

• (c) 120–200 ms

• (d) 500–600 ms

Q18. ECG shows QRS 0.14 s with an rSR′ pattern in V1. This is

• (a) right bundle branch block

• (b) left bundle branch block

• (c) WPW

• (d) hyperkalaemia

Q19. Broad notched R waves with absent Q waves in I, aVL, V5 and V6 and QRS ≥ 0.12 s indicate

• (a) right bundle branch block

• (b) left bundle branch block

• (c) WPW

• (d) left anterior fascicular block

Q20. Every P wave is followed by a QRS, but the PR interval is 0.28 s. This is

• (a) complete heart block

• (b) Mobitz II

• (c) Mobitz I

• (d) first-degree AV block

Q21. A rhythm strip shows the PR interval getting longer each beat until a QRS is dropped, then the cycle repeats. This is

• (a) third-degree block

• (b) Mobitz type I (Wenckebach)

• (c) Mobitz type II

• (d) sinus arrhythmia

Q22. Constant PR intervals with sudden dropped QRS complexes in a 3:1 pattern indicate

• (a) atrial flutter

• (b) Mobitz type I block

• (c) first-degree block

• (d) Mobitz type II block

Q23. A dizzy elderly man has a slow pulse, cannon a waves in the neck and varying loudness of S1. ECG would show

• (a) AF

• (b) complete AV dissociation (third-degree block)

• (c) sinus tachycardia

• (d) first-degree block

Q24. A 40-year-old without known heart disease develops new complete heart block. A cause to search for, found in up to a third of such patients, is

• (a) cardiac sarcoidosis

• (b) hypercalcaemia

• (c) WPW

• (d) rheumatic fever

Q25. Mobitz type I block in a healthy young athlete is

• (a) caused by hyperkalaemia always

• (b) always an indication for pacing

• (c) a sign of acute MI

• (d) often physiological

Q26. Before pacing a patient with symptomatic bradycardia, the ICMR workflow asks you to exclude

• (a) drugs such as beta-blockers, calcium channel blockers or digoxin

• (b) asthma

• (c) migraine

• (d) hypercholesterolaemia

Q27. Torsades de pointes is promoted by all EXCEPT

• (a) slow heart rate

• (b) hypokalaemia

• (c) hypomagnesaemia

• (d) hypercalcaemia

Q28. In atrial flutter, the atrial rate is typically about

• (a) 60/min

• (b) 300/min

• (c) 600/min

• (d) 150/min

Q29. Which drug classification groups antiarrhythmics into four main classes by cellular effect?

• (a) NYHA

• (b) CHA2DS2-VASc

• (c) Vaughan Williams

• (d) Killip

Q30. Absent P waves can be seen in all EXCEPT

• (a) first-degree AV block

• (b) atrial fibrillation

• (c) sinus arrest

• (d) severe hyperkalaemia

Active Recall

From memory: describe the ECG of AF, flutter, SVT, WPW, VT, torsades and VF with first treatment; list what lengthens and shortens the QT and what causes tall T waves; contrast RBBB and LBBB; and describe each degree of AV block with its significance.