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

Source: https://tracknation.in/story/ecg-and-arrhythmias-for-neet-pg-medicine-af-flutter-svt-wpw-vt-torsades-heart-block-bundle-branch-block-qt (TrackNation — free UPSC notes with PYQs)

> NEET PG Medicine: ECG intervals and what lengthens or shortens them, bundle branch blocks, atrial fibrillation and flutter, reentrant SVT and WPW, ventricular tachycardia and fibrillation, torsades de pointes, AV blocks and pacing, with schematic rhythm strips, hooks, vignette MCQs and cards.

## Start Here

🎯 **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.

| **Rhythm**

 | **ECG**

 | **First treatment**

 |
| AF

 | No P, irregular f waves, irregularly irregular

 | Rate control (beta-blocker, non-DHP CCB, digoxin) + anticoagulation

 |
| Atrial flutter

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

 | Rate control, cardioversion

 |
| Reentrant SVT

 | Regular narrow QRS; sudden start and stop

 | Vagal manoeuvres → IV adenosine or non-DHP CCB

 |
| AF with WPW

 | Fast, irregular, wide/varied QRS

 | Cardioversion or IV procainamide/ibutilide; avoid digoxin, adenosine, verapamil, diltiazem

 |
| VT

 | ≥ 3 wide beats ≥ 120/min

 | Cardioversion or antiarrhythmics; ICD long term

 |
| Torsades

 | Twisting QRS on long QT

 | IV magnesium; defibrillate if VF

 |
| VF

 | Chaotic, no output

 | 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).

| **AV block**

 | **ECG**

 | **Note**

 |
| First degree

 | Every P conducted; PR > 0.20 s

 | Usually benign

 |
| Mobitz I (Wenckebach)

 | PR lengthens until a QRS drops; next PR shortest

 | Can be physiological in young athletes

 |
| Mobitz II

 | Constant PR; sudden dropped QRS (e.g. 3:1, 4:1)

 | Infranodal; risk of progression

 |
| Third degree (complete)

 | No P waves conducted; P rate > QRS rate; AV dissociation

 | Cannon a waves, variable S1; pacing

 |

## 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

- No P, f waves, irregularly irregular.

- Embolic stroke.

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

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

- AVNRT.

- Vagal → IV adenosine / non-DHP CCB.

- Short PR + delta wave; AVRT.

- Digoxin, adenosine, verapamil, diltiazem.

- Cardioversion or IV procainamide/ibutilide.

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

- VT until proved otherwise.

- CPR + immediate defibrillation.

- Twisting QRS, long QT; IV magnesium.

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

- High Ca, high Mg, digoxin.

- Hyperkalaemia, acute MI, LBBB.

- rSR′ in V1–V2; QRS ≥ 0.12.

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

- PR > 0.20 s.

- PR lengthens → drop.

- Fixed PR → drop.

- AV dissociation; cannon a waves.

- 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

**Answer: (a)** — Atrial fibrillation; anticoagulate by risk.

**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

**Answer: (c)** — Also mechanical valves, hyperthyroidism, hypertension, diabetes, LV dysfunction.

**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

**Answer: (a)** — Amiodarone if these fail.

**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

**Answer: (c)** — Atria ~300/min; half conducted.

**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

**Answer: (b)** — Or a non-dihydropyridine CCB.

**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

**Answer: (c)** — AVRT is the usual tachycardia in WPW.

**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

**Answer: (b)** — Short PR + delta wave = pre-excitation.

**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

**Answer: (d)** — Also avoid digoxin, adenosine, diltiazem.

**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

**Answer: (b)** — They prolong the accessory pathway refractory period.

**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

**Answer: (a)** — Sustained if ≥ 30 seconds.

**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

**Answer: (b)** — A classic safety rule.

**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

**Answer: (c)** — Sustained = ≥ 30 s or collapse.

**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

**Answer: (b)** — Ventricular fibrillation.

**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

**Answer: (a)** — Torsades de pointes; defibrillate if VF follows.

**Q15.** Which electrolyte abnormality shortens the QT interval?

- (a) hypocalcaemia

- (b) hypokalaemia

- (c) hypercalcaemia

- (d) hypomagnesaemia

**Answer: (c)** — Also hypermagnesaemia and digoxin.

**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

**Answer: (a)** — Also acute MI, LBBB, ventricular hypertrophy.

**Q17.** Normal QTc in adult women is about

- (a) 360–460 ms

- (b) 200–300 ms

- (c) 120–200 ms

- (d) 500–600 ms

**Answer: (a)** — Men 350–450 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

**Answer: (a)** — LBBB has broad notched R in I, aVL, V5–V6.

**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

**Answer: (b)** — RBBB shows rSR′ in V1.

**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

**Answer: (d)** — PR > 0.20 s.

**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

**Answer: (b)** — Can be physiological in young athletes.

**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

**Answer: (d)** — Infranodal and more dangerous.

**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

**Answer: (b)** — No P waves are conducted.

**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

**Answer: (a)** — Lyme carditis is a reversible cause.

**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

**Answer: (d)** — Narrow QRS → usually in the AV node.

**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

**Answer: (a)** — Also check electrolytes and thyroid.

**Q27.** Torsades de pointes is promoted by all EXCEPT

- (a) slow heart rate

- (b) hypokalaemia

- (c) hypomagnesaemia

- (d) hypercalcaemia

**Answer: (d)** — Hypercalcaemia shortens QT.

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

- (a) 60/min

- (b) 300/min

- (c) 600/min

- (d) 150/min

**Answer: (b)** — Range 250–350.

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

- (a) NYHA

- (b) CHA2DS2-VASc

- (c) Vaughan Williams

- (d) Killip

**Answer: (c)** — Class I–IV.

**Q30.** Absent P waves can be seen in all EXCEPT

- (a) first-degree AV block

- (b) atrial fibrillation

- (c) sinus arrest

- (d) severe hyperkalaemia

**Answer: (a)** — First-degree block has P waves with long PR.

### 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.