Atrioventricular Re-entrant Tachycardia and WPW Syndrome

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Questions and Answers

Which of the following could lead to a broad complex tachycardia?

Orthodromic AVRT

Antidromic AVRT (correct)

Ectopic beats during AVNRT

Increased vagal tone

What is the preferred initial management for a patient with atrial tachycardia who is haemodynamically compromised?

Administer beta blockers immediately

Perform electrical cardioversion (correct)

Administer antiarrhythmic medication

Start calcium channel blockers

Which characteristic is specific to AVNRT?

Accessory pathway involvement

Presence of a P wave before the QRS complex

Wide QRS complexes

Narrow complex tachycardia (correct)

What is a key mechanism underlying AVRT?

Presence of an accessory pathway between atria and ventricles Signup and view all the answers

Wolff-Parkinson White syndrome is associated with which of the following?

Accessory pathway connection via the bundle of Kent Signup and view all the answers

What is a hallmark ECG feature of Right Bundle Branch Block (RBBB)?

Widened QRS complex greater than 120msec Signup and view all the answers

Which of the following conditions can lead to Left Bundle Branch Block (LBBB)?

Left ventricular outflow obstruction Signup and view all the answers

In symptomatic patients with RBBB, which intervention is likely considered for chronic management?

Pacemaker insertion Signup and view all the answers

What does a tall late R wave in lead V1 suggest in the context of RBBB?

Right ventricular activation delay Signup and view all the answers

Which testing method is primarily used to diagnose bundle branch blocks?

Electrocardiogram (ECG) Signup and view all the answers

Which feature would most likely be observed in a patient with LBBB?

Tall late R wave in leads I and V6 Signup and view all the answers

In the presence of new RBBB and chest pain, what condition may it indicate?

Myocardial infarction Signup and view all the answers

Which statement is true regarding the prognosis of asymptomatic patients with RBBB?

They usually have benign outcomes with no correlation to adverse events. Signup and view all the answers

What is the most common heart rate range for atrioventricular re-entrant tachycardia (AVRT)?

110 to 250 beats per minute Signup and view all the answers

What type of wave may be observed on an ECG during Wolff-Parkinson White syndrome?

Delta wave Signup and view all the answers

In the acute management of narrow complex tachycardia, what initial assessment is crucial?

Haemodynamic stability Signup and view all the answers

Which feature is NOT typical for atrioventricular nodal re-entrant tachycardia (AVNRT)?

Visible P waves on ECG Signup and view all the answers

What is a common presentation for patients with Wolff-Parkinson White syndrome?

Paroxysmal supraventricular tachycardia Signup and view all the answers

What intervention can be performed if a patient with Wolff-Parkinson White syndrome is haemodynamically stable?

Vagal manoeuvres Signup and view all the answers

Which statement regarding AVRT is inaccurate?

It occurs due to a short circuit within the AV node. Signup and view all the answers

What is typically included in the presentation of atrioventricular nodal re-entrant tachycardia (AVNRT)?

Palpitations, chest discomfort, dizziness Signup and view all the answers

Study Notes

Atrioventricular Re-entrant Tachycardia (AVRT)

AVRT is a type of tachycardia caused by a premature ventricular complex
ECG may show a "delta wave" which is a slurred upstroke on the QRS complex associated with a shortened PR interval
Patients may experience palpitations, pounding in the neck, dizziness, and chest discomfort
Heart rate is typically between 110-250 beats per minute

Wolff-Parkinson White (WPW) Syndrome

Congenital malformation leads to incomplete separation of the atria and ventricles during fetal development
Patients may experience paroxysmal supraventricular tachycardia (SVT)
Resting ECG may show a shortened PR interval, a delta wave, and a prolonged QRS complex
Patients with normal blood pressure may be managed with vagal maneuvers, adenosine, calcium-channel blockers, or beta-blockers but only in the presence of resuscitation equipment as fast atrial fibrillation can result
Haemodynamically unstable patients may require direct current (DC) cardioversion or medications like flecainide, procainamide, or amiodarone, which slow or block the accessory pathway

Atrioventricular Nodal Re-entrant Tachycardia (AVNRT)

A regular, paroxysmal narrow complex tachycardia
Short circuit occurs within the AV node
One P wave per QRS but usually not visible due to simultaneous contraction of the atria and ventricles. If visible, it is usually just after the QRS complex.
Most common cause of palpitations in patients without structural heart disease
More common in women than men
May present with palpitations, chest discomfort, dizziness, and rapid pounding in the neck
Heart rate is typically between 110-250 bpm

Acute Management of Narrow Complex Tachycardia

Assess if the patient is haemodynamically stable
Signs of haemodynamic instability include low blood pressure and tachycardia
If no haemodynamic compromise, the patient may be treated with a beta-blocker, calcium-channel blocker, or antiarrhythmic medication
If haemodynamically compromised, cardioversion may be indicated

Re-entrant Tachycardias: AVRT and AVNRT

Re-entry allows a wave of depolarization to cycle around the heart tissue, causing tachycardia
AVRT: Part of the re-entry circuit lies outside the AV node. This can lead to a narrow or broad complex tachycardia depending on whether the cycle is clockwise or anticlockwise.
AVNRT: The re-entry circuit is within the AV node, leading to a narrow complex tachycardia.

AVRT and AVNRT

Usually paroxysmal tachycardias (they start and stop suddenly)
Usually regular with a heart rate greater than 150 bpm
Wolff-Parkinson-White syndrome is an example of an AVRT with an accessory called the bundle of Kent, which is an accessory pathway
Do not occur commonly as cells are often in a refractory stage when they receive the following depolarization, so they are unable to "pass the message on"
When arrhythmia occurs, it is often triggered by an ectopic beat that propagates through the system
May be associated with thyrotoxicosis as this increases the likelihood of ectopic beats

AVRT: Atrioventricular Re-entrant Tachycardia Explained

Re-entrant circuit due to the presence of an accessory pathway between the atria and ventricles
Two types: Orthodromic and Antidromic
- Orthodromic: Anterograde down the AV node pathway and retrograde up the accessory pathway, leading to a narrow complex tachycardia. The P wave is often present after the QRS complex. Usually generated by a premature atrial complex
- Antidromic: Anterograde down the accessory pathway and retrograde up through the AV node, leading to a broad QRS complex tachycardia. Calcium channel blockers, beta-blockers, and digoxin may be used to manage this.
Other possible causes of AVRT:
- Idiopathic degeneration of the conducting system (Lenegre's or Lev's disease)

Blocks to the Bundle Branches

The right and left bundle branches come off the bundle of His
The left bundle branch subdivides into the anterior and posterior divisions
Complete block of a bundle branch is associated with a widened QRS complex
The shape of the QRS complex depends on whether the right or left bundle is blocked

Right Bundle Branch Block (RBBB)

The right ventricle is activated later than normal (as the bundle branch that would activate the right ventricle quickly is blocked)
QRS is greater than 120 msec (3 small squares)
Deep S wave in leads I and V6
Tall late R wave or second R wave (R') in the QRS of lead V1 ("rabbit ear" pattern)

Causes of RBBB

May include:
- Congenital heart disease (ASD, VSD, tetralogy of Fallot)
- Pulmonary disease (pulmonary hypertension, pulmonary embolism)
- Myocardial disease (MI, cardiomyopathy)
New RBBB with chest pain:
- May indicate occlusion of the left anterior ascending artery
New RBBB with dyspnea:
- May indicate pulmonary embolism

Presentation and Assessment of RBBB

May be an incidental finding
Asymptomatic individuals - no correlation with adverse outcomes and usually benign
Patients may present with episodes of syncope
ECG: Important tool for diagnosis
Echocardiogram: Used to assess the heart's structure and function

Treatment of RBBB

Asymptomatic - none required
Symptomatic:
- Pacemaker
- Cardiac resynchronization therapy - biventricular pacing

Left Bundle Branch Block (LBBB)

The left ventricle is activated later than normal (as the bundle branch that would activate the left ventricle quickly is blocked)
QRS is wider than 120 msec (3 small squares)
Deep S wave in lead V1
Tall late R wave in leads 1 and V6
Abnormal Q waves (as the left bundle branch usually initiates ventricular contraction)

Causes of LBBB

LBBB always affects the cardiovascular system and increases mortality
More common in people with structural and ischemic heart disease
May include:
- Left ventricular outflow obstruction
- Hypertensive heart disease
- Aortic stenosis
- Myocardial infarction
- Cardiomyopathy

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Description

This quiz focuses on Atrioventricular Re-entrant Tachycardia (AVRT) and Wolff-Parkinson White (WPW) Syndrome, exploring their symptoms, ECG findings, and management strategies. Understand the connection between ventricular complexes and the occurrence of tachycardia, as well as treatment options for patients experiencing these conditions.