ECG & arrhythmias — MRCP Part 1 flashcards

Question 1

A patient with Wolff–Parkinson–White syndrome develops an irregular broad-complex tachycardia (pre-excited atrial fibrillation). Which group of drugs must be avoided?

Accepted Answer

AV node-blocking drugs: adenosine, verapamil, diltiazem, beta-blockers and digoxin. — Blocking the AV node pushes more atrial impulses down the accessory pathway. The ventricular rate can then rise further and degenerate into ventricular fibrillation.

Question 2

A 66-year-old with a previous anterior MI has palpitations. BP 128/80 mmHg, alert, no chest pain or breathlessness. ECG: regular broad-complex tachycardia at 170/min. What rhythm should you assume until proven otherwise?

Accepted Answer

Ventricular tachycardia (VT). — In someone with structural heart disease, a regular broad-complex tachycardia is far more often VT than SVT with aberrant conduction. Treating SVT as VT is safe; treating VT as SVT can be fatal.

Question 3

First-line drug treatment for torsades de pointes is intravenous ______.

Accepted Answer

magnesium sulfate — Torsades is polymorphic VT associated with a long QT interval. Magnesium suppresses the early after-depolarisations that trigger it, even when the serum magnesium is normal.

Question 4

In stable narrow-complex SVT, what are the IV adenosine bolus doses if the first fails?

Accepted Answer

6 mg, then 12 mg, then 18 mg, as rapid IV boluses. — Adenosine has a half-life of seconds, so it must be pushed fast through a large vein with a flush to reach the AV node in an effective concentration.

Question 5

Atrial flutter with 2:1 block typically produces a ventricular rate of about what?

Accepted Answer

About 150 beats per minute. — The atrial rate in flutter is around 300/min. With every second impulse blocked at the AV node, the ventricles beat at about 150/min.

Question 6

What is the first-line definitive treatment for typical atrial flutter?

Accepted Answer

Catheter ablation of the cavotricuspid isthmus. — Typical flutter is a macro-re-entry circuit in the right atrium that passes through the cavotricuspid isthmus. Ablating that narrow isthmus breaks the circuit; success is over 90%.

Question 7

A 74-year-old with an exacerbation of COPD is hypoxic. ECG: irregularly irregular rhythm at 120/min with at least three different P-wave morphologies. What is the rhythm?

Accepted Answer

Multifocal atrial tachycardia (MAT). — Several ectopic atrial foci fire, each producing its own P-wave shape. MAT is usually driven by systemic illness — hypoxia, electrolyte disturbance or catecholamine excess — rather than primary heart disease.

Question 8

For AF of more than 48 hours, how long should anticoagulation be given before elective electrical cardioversion?

Accepted Answer

At least 3 weeks (or exclude left atrial thrombus with transoesophageal echo). — Thrombus may already have formed in the left atrial appendage. Restoring organised atrial contraction can dislodge it, so the patient must be protected first.

Question 9

Why is flecainide avoided for rhythm control in a patient with ischaemic or structural heart disease?

Accepted Answer

It can provoke dangerous ventricular arrhythmias (pro-arrhythmia) in a scarred or structurally abnormal heart. — Flecainide is a class Ic sodium channel blocker that slows conduction. In ischaemic myocardium this promotes re-entry and increased mortality. Amiodarone is the choice when there is structural heart disease.

Question 10

In a patient with AF and moderate–severe mitral stenosis, which anticoagulant is used?

Accepted Answer

Warfarin. DOACs are not recommended in this group. — The DOAC trials excluded significant (mostly rheumatic) mitral stenosis, where thromboembolic risk is very high. Warfarin is also used with mechanical valves.

Question 11

For a man with AF, at what CHA₂DS₂-VASc score does NICE say to consider, and to offer, anticoagulation?

Accepted Answer

Consider at a score of 1; offer at 2 or more (in women, offer at 2 or more). — Female sex scores one point but does not by itself increase risk. A score of 0 in men or 1 in women means no anticoagulation.

Question 12

In a cardiac arrest with a shockable rhythm (VF or pulseless VT), when is amiodarone 300 mg IV first given?

Accepted Answer

After the 3rd shock (with adrenaline 1 mg). — Early shocks are the priority. If VF persists after three shocks, adrenaline and amiodarone 300 mg are given; amiodarone 150 mg can follow after the 5th shock.

Question 13

Peri-arrest bradycardia with adverse features: what is the first drug and its dose?

Accepted Answer

Atropine 500 micrograms IV, repeated every 3–5 minutes to a maximum of 3 mg. — Atropine blocks muscarinic receptors, removing vagal slowing of the SA and AV nodes.

Question 14

What are the earliest ECG changes of hyperkalaemia?

Accepted Answer

Tall, narrow, tented T waves. — As potassium rises further: flattened/absent P waves, PR prolongation, QRS widening, then a sine-wave pattern and VF/asystole.

Question 15

What is the characteristic ECG wave of hypothermia?

Accepted Answer

The Osborn (J) wave — a positive hump at the junction of QRS and ST segment. — Other features: bradycardia, long PR/QT and arrhythmias (AF, VF, asystole). Defibrillation may be ineffective below 30°C.

Question 16

What does the ECG "reverse tick" (Salvador Dalí moustache) ST depression indicate?

Accepted Answer

Digoxin effect. — Digoxin produces scooped ST depression and a short QT at therapeutic levels. It does not by itself mean toxicity; toxicity causes arrhythmias such as AV block.

Question 17

Hypercalcaemia ______ and hypocalcaemia ______ the QT interval.

Accepted Answer

shortens; prolongs — Calcium entry governs the plateau (phase 2) of the action potential. More extracellular calcium shortens the plateau; less prolongs it.

Question 18

What does NICE recommend as initial rate-control monotherapy in atrial fibrillation?

Accepted Answer

A standard beta-blocker (not sotalol) or a rate-limiting calcium channel blocker (diltiazem or verapamil). — Both slow AV node conduction. Choose by comorbidity — rate-limiting CCBs are avoided in HFrEF. Digoxin is added if one drug is not enough.

Question 19

Name two groups of AF patients in whom NICE prefers rhythm control over rate control first-line.

Accepted Answer

Any two of: AF with a reversible cause; heart failure thought to be caused by AF; new-onset AF; atrial flutter suitable for ablation; rhythm control judged more suitable. — For everyone else, rate control is first-line because it is as good as rhythm control for outcomes and avoids antiarrhythmic toxicity.

Question 20

For stable AF of under 48 hours, pharmacological cardioversion uses ______ if there is no structural heart disease, or amiodarone if there is.

Accepted Answer

flecainide — NICE offers a choice of flecainide or amiodarone when there is no structural or ischaemic heart disease, and amiodarone only when there is. Flecainide is pro-arrhythmic in structurally abnormal hearts. Do not use magnesium or a calcium channel blocker for pharmacological cardioversion.

Question 21

For stable AF of under 48 hours, pharmacological cardioversion uses flecainide if there is no structural heart disease, or ______ if there is.

Accepted Answer

amiodarone — NICE offers a choice of flecainide or amiodarone when there is no structural or ischaemic heart disease, and amiodarone only when there is. Flecainide is pro-arrhythmic in structurally abnormal hearts. Do not use magnesium or a calcium channel blocker for pharmacological cardioversion.

Question 22

Catheter ablation for atrial fibrillation electrically isolates which structures?

Accepted Answer

The pulmonary veins, from the left atrium (pulmonary vein isolation). — Most AF triggers fire from muscle sleeves in the pulmonary veins. NICE suggests radiofrequency point-by-point ablation first, with cryoballoon or laser balloon ablation if that is unsuitable, when drugs fail or are not tolerated.

Question 23

Which antiarrhythmic is second-line (per the notes) for maintaining sinus rhythm after cardioversion of AF, and must be avoided in heart failure?

Accepted Answer

Dronedarone. — It is related to amiodarone but has no iodine. It increased mortality in people with heart failure or LV systolic dysfunction and in permanent AF, so it is contraindicated there.

Question 24

Which class of anticoagulant is first-line for stroke prevention in non-valvular atrial fibrillation?

Accepted Answer

A direct oral anticoagulant (DOAC): apixaban, dabigatran, edoxaban or rivaroxaban. — DOACs are at least as effective as warfarin, cause less intracranial bleeding and need no INR monitoring.

Question 25

Which drug is used for a "pill-in-the-pocket" strategy in infrequent paroxysmal AF without structural heart disease?

Accepted Answer

Flecainide, taken orally at the start of an episode. — NICE allows it for people with infrequent symptomatic paroxysms, no LV dysfunction, valve or ischaemic heart disease, systolic BP above 100 mmHg and resting heart rate above 70, who can use it reliably.

Question 26

What is the first-line treatment for a haemodynamically stable regular narrow-complex SVT?

Accepted Answer

Vagal manoeuvres — the modified Valsalva manoeuvre is the most effective. — Raising vagal tone slows AV node conduction and can break the re-entry circuit. If they fail, give IV adenosine; unstable patients go straight to synchronised DC cardioversion.

Question 27

Current RCUK algorithm: what is the first-line treatment of a STABLE regular broad-complex tachycardia treated as VT?

Accepted Answer

Synchronised DC cardioversion under sedation or anaesthesia. If that risk is too high: IV procainamide, or amiodarone if procainamide is unavailable. — Cardioversion is more reliably effective than drugs. Amiodarone is given as 300 mg IV over 10–60 minutes, then 900 mg over 24 hours.

Question 28

Tachyarrhythmia with a pulse and life-threatening features: what is given if up to three synchronised shocks fail?

Accepted Answer

IV amiodarone 300 mg over 10–20 minutes (or procainamide 10–15 mg/kg over 20 minutes), then repeat the synchronised shock. — Life-threatening features (shock, syncope, myocardial ischaemia, severe heart failure) mean electricity comes first. The drug makes further shocks more likely to work.

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