Arrhythmias: Supraventricular tachycardias

Question 1

Categorise the types of Supraventricular tachycardia

Answer 1

Sinus tachycardia Paroxysmal SVTs: AVNRT and AVRT Atrial tachyarrythmias: -Atrial fibrillation -Atrial flutter -Atrial tachycardia -Atrial ectopic beats

Question 2

Categorise the types of Ventricular tachycardia

Answer 2

Life-threatening: -Sustained ventricular tachycardia -Ventricular fibrillation -Torsades de pointes Normal heart ventricular tachycardia Non-sustained ventricular tachycardia Ventricular ectopic beats

Question 3

Define supraventricular and ventricular tachycardias

Answer 3

Supraventricular tachycardias arise from atrium or AV junction. Conduction via the His-Purkinje system produces a narrow QRS (<120ms). Ventricular tachycardias arise from the ventricles.

Question 4

Define inappropriate sinus tachycardia

Answer 4

A persistent increase in resting heart rate unrelated to, or out of proportion with, the level of physical or emotional stress.

Question 5

Outline the aetiology of sinus tachycardia

Answer 5

Generally a secondary phenomenon: Acute: Exercise, emotion, pain, fever, infection, PE etc. Chronic: Pregnancy, anaemia, hyperthyroid, catecholamine excess. Inappropriate sinus tachycardis is extremely rare. Can be due to enhanced automaticity, or abnormal autonomic regulation of the heart.

Question 6

What are paroxysmal SVTs?

Answer 6

Tachycardias that occur at the AV junction, including AV nodal re-entrant tachycardia (AVNRT) and AV re-entrant tachycardia (AVRT). These are often seen in young patients with little or no structural heart disease. Commonly presents between ages 12-30.

Question 7

Explain AVNRT

Answer 7

AVNRT is the commonest cause of palpitations in patients with normal heart structure. Mechanism: re-entrant circuit around the AVN, typically ‘slow-fast’ AVNRT.

Question 8

What ECG changes are seen in AVNRT?

Answer 8

Tachycardia (usually 140-240 bpm) Regular R-R interval Absent P wave (if simultaneous atrial and ventricular activation), or Inverted P wave immediately before/after QRS Narrow QRS complexes

Question 9

Explain AVRT

Answer 9

Formation of a re-entrant pathway comprising of the AV node, the His bundle, the ventricle, and an accessory pathways between ventricle and atria. This is a macro re-entry circuit activated sequentially.

Question 10

What ECG changes are seen in AVRT?

Answer 10

Tachycardia (usually 200-300bpm) Regular R-R interval Orthodromic: Narrow QRS complex, P wave visible between QRS and T wave Antidromic: Wide QRS complex

Question 11

Define Wolff-Parkinson-White syndrome

Answer 11

A congenital condition featuring: -Bundle of Kent -Symptomatic episodes of tachyarrhythmia/palpitations

Question 12

What ECG changes are seen in Wolff-Parkinson-White syndrome in sinus rhythm?

Answer 12

Delta wave Narrow QRS complex elongation >110ms Short PR interval <120ms

Question 13

How can Wolff-Parkinson-White syndrome present?

Answer 13

AVRT: 200-300bpm -Orthodromic: Narrow QRS complex, P wave visible between QRS and T wave -Antidromic (5%): Wide QRS complex AF: risk of VF in WPW -Palpitations, SoB, chest pain, syncope, stroke/TIA Sudden cardiac death (rare)

Question 14

Outline the definitive treatment of Wolff-Parkinson-White syndrome

Answer 14

Asymptomatic: Monitor for symptoms Minimally symptomatic: Ablation of bundle of Kent Symptomatic: Ablation of bundle of Kent

Question 15

Describe the clinical features of paroxysmal SVTs

Answer 15

Regular rapid palpitations: Sudden onset and offset May be terminated by Valsalva manoeuvre May include: anxiety, dizziness, dyspnoea, neck pulsation, central chest pain, fatigue Polyuria due to ANP release, esp in AVNRT and AF Syncope (10-15%)

Question 16

Describe the acute management of paroxysmal SVTs

Answer 16

SVT + haemodynamic instability -> DC cardioversion SVT + haemodynamic stablility: 1. Valsalva manoeuvre or carotid sinus massage 2. IV adenosine: initially 6mg, then 2x12mg if needed -Verapamil, metoprolol, or diltiazem if adenosine contraindicated e.g. Asthma 3. DC cardioversion *slightly differs if known WPW syndrome

Question 17

What is the mechanism of action of adenosine

Answer 17

Adenosine causes very short complete heart block, which can interrupt re-entrant pathways in the AV node, and restore normal sinus rhythm in paroxysmal SVTs.

Question 18

List 3 side effects of adenosine

Answer 18

Bronchospasm Flushing Chest pain Heaviness of limbs Sense of impending doom*: important advise this will only be for a brief time

Question 19

Name 2 contraindications of non-dihydropyridine CCBs and Beta-blockers in the treatment of paroxysmal SVTs

Answer 19

AVN blockers: Verapamil, diltiazem, and beta-blockers should not be given: -After Beta-blocker, or -Broad-QRS complex tachycardias

Question 20

Describe the Valsalva manoeuvre

Answer 20

Should be undertaken in supine position Forceful exhalation against a closed airway Avoid deep inspiration prior to straining

Question 21

Name 5 causes of atrial tachyarrhythmias

Answer 21

Increasing age MI Hypertension Obesity Diabetes mellitus Hypertrophic cardiomyopathy Heart failure Valvular heart disease Myocarditis/pericarditis Cardiothoracic surgery Chest infections Hyperthyroidism Electrolyte imbalances

Question 22

Define atrial flutter

Answer 22

Organised atrial rhythm with an atrial rate typically between 300-350 bpm. These can occur around the tricuspid annulus, fibrosis, or pulmonary veins (LA).

Question 23

How is ventricular rate determined in atrial flutter?

Answer 23

Ventricular rate is determined by the AV conduction ratio. 2:1 block (commonest): 150 bpm 1:1 block: 300 bpm - associated with severe haemodynamic instability and progression to VF 3:1 block: 100 bpm 4:1 block: 75 bpm - seen when receiving treatment, or underlying heart disease

Question 24

What is 1:1 atrial flutter associated with?

Answer 24

Severe haemodynamic instability Progression to VF

Question 25

What ECG changes are seen with typical atrial flutter?

Answer 25

Sawtooth pattern: best seen in II, III, aVF Narrow QRS complex, Broad QRS in 1:1 flutter Regular R-R interval P waves present

Question 26

How is atrial flutter managed?

Answer 26

Similar to atrial fibrillation Symptomatic acute paroxysmal flutter: DC cardioversion Ablation has greater success rate than in AF

Question 27

What monitoring is required whilst taking amiodarone?

Answer 27

Prior to treatment: TFTs: risk of thyroid dysfunction LFTs: raised serum transaminase, risk of cirrhosis U&Es: hypokalaemia can cause arrhythmias CXR: risk of pulmonary fibrosis Every 6 months: TFTs LFTs

Question 28

Describe the treatment of SVT episodes in known WPW

Answer 28

SVT + haemodynamic instability -> DC cardioversion SVT + haemodynamic stablility: 1. Valsalva manoeuvre or carotid sinus massage 2. Flecainide: blocks accessory pathway conduction 3. DC cardioversion

Question 29

What SVT drugs should be avoided in known WPW?

Answer 29

Adenosine: small risk of precipitating pre-excited AF Digoxin: promotes accessory pathway conduction