Pre-excitation syndrome: Difference between revisions
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=== WPW Syndrome === | === WPW Syndrome === | ||
WPW is a combination of the presence of '''congenital accessory pathways along with episodic [[tachyarrhythmias]]'''. Here the accessory pathways are referred to as ''[[Bundle of Kent]] or [[AV bypass tracts]].'' | WPW is a combination of the presence of '''congenital accessory pathways along with episodic [[tachyarrhythmias]]'''. Here the accessory pathways are referred to as ''[[Bundle of Kent]] or [[AV bypass tracts]].'' | ||
The features of pre-excitation are subtle, intermittent, and are aggravated by an increase in vagal tone ( [[Valsalva maneuver|Valsalva maneuve]]<nowiki/>r, AV blockage by drugs). | The features of pre-excitation are subtle, intermittent, and are aggravated by an increase in vagal tone ( [[Valsalva maneuver|Valsalva maneuve]]<nowiki/>r, AV blockage by drugs). | ||
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!Co-existing Conditions | !Co-existing Conditions | ||
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|'''[[Atrial fibrillation|Atrial Fibrillation]] (AFib)'''''' | |'<nowiki/>''[[Atrial fibrillation|Atrial Fibrillation]] (AFib)''''''''' | ||
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* Irregularly irregular | * Irregularly irregular | ||
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* Left chamber enlargement | * Left chamber enlargement | ||
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|'''[[Atrial Flutter]]''' | |'''[[Atrial Flutter]]''' | ||
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* Regular or Irregular | * Regular or Irregular | ||
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*[[Alcohol]] | *[[Alcohol]] | ||
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|'''[[Atrioventricular nodal reentry tachycardia]] ([[AV nodal reentrant tachycardia|AVNRT]])''''''''' | |'''[[Atrioventricular nodal reentry tachycardia]] ([[AV nodal reentrant tachycardia|AVNRT]])'''''''''''' | ||
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* Regular | * Regular | ||
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*[[Atrial tachyarrhythmias]] | *[[Atrial tachyarrhythmias]] | ||
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|'''[[Multifocal atrial tachycardia|Multifocal Atrial Tachycardia]]'''''' | |'<nowiki/>''[[Multifocal atrial tachycardia|Multifocal Atrial Tachycardia]]''''''''' | ||
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* Irregular | * Irregular | ||
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*[[Wolff-Parkinson-White syndrome]]''' | *[[Wolff-Parkinson-White syndrome]]''' | ||
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|'''[[Premature atrial contraction|Premature Atrial Contractrions]] ([[Premature atrial contraction|PAC]])''' | |'''[[Premature atrial contraction|Premature Atrial Contractrions]] ([[Premature atrial contraction|PAC]])''' | ||
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* Regular except when disturbed by premature beat(s) | * Regular except when disturbed by premature beat(s) | ||
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*[[Hypercholesterolemia]] | *[[Hypercholesterolemia]] | ||
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|'''[[Wolff-Parkinson-White syndrome|Wolff-Parkinson-White Syndrome]]'''''' | |'<nowiki/>''[[Wolff-Parkinson-White syndrome|Wolff-Parkinson-White Syndrome]]''''''''' | ||
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*[[Tuberous sclerosis]] | *[[Tuberous sclerosis]] | ||
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|'''[[Ventricular fibrillation|Ventricular Fibrillation]] (VF)''' | |'''[[Ventricular fibrillation|Ventricular Fibrillation]] (VF)''' | ||
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* Irregular | * Irregular | ||
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*[[Stroke]] | *[[Stroke]] | ||
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|'''[[Ventricular tachycardia|Ventricular Tachycardia]]''' | |'''[[Ventricular tachycardia|Ventricular Tachycardia]]''' | ||
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*Incidence 0.1 – 3.0 per 1000 | *Incidence 0.1 – 3.0 per 1000 | ||
*[[Lown-Ganong-Levine syndrome|LGL syndrome]] is a rare Man > woman. | *[[Lown-Ganong-Levine syndrome|LGL syndrome]] is a rare Man > woman. | ||
*prognosis is good with [[SCD]] is noted in only 0.1% (rare) | *prognosis is good with [[SCD]] is noted in only 0.1% (rare)<br /> | ||
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== Risk Factors == | == Risk Factors == | ||
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====<u>[[Atrioventricular (AV) reentrant tachycardia|Atrioventricular Reentry Tachycardia's (AVRT)]]</u>==== | ====<u>[[Atrioventricular (AV) reentrant tachycardia|Atrioventricular Reentry Tachycardia's (AVRT)]]</u>==== | ||
[[File:Orth.gif|thumb|AVRT ( Orthodromic and Antidromic)|435.99x435.99px]]AVRT is a form of PSVT. Reentry circuit results from the combination of signal transduction from normal conduction system and [[accessory pathway]]. | [[File:Orth.gif|thumb|AVRT ( Orthodromic and Antidromic)|435.99x435.99px]]AVRT is a form of PSVT. Reentry circuit results from the combination of signal transduction from normal conduction system and [[accessory pathway]].( See: Diagram)<ref name="urlCardiac dysrhythmias (Chapter 4) - An Introduction to Clinical Emergency Medicine">{{cite web |url=https://www.cambridge.org/core/books/an-introduction-to-clinical-emergency-medicine/cardiac-dysrhythmias/6FD797C2E6CEAE6A61705158AE9C7A9A |title=Cardiac dysrhythmias (Chapter 4) - An Introduction to Clinical Emergency Medicine |format= |work= |accessdate=}}</ref> | ||
* During tachyarrythmias, the [[accessory pathway]] forms part of the reentry circuit that results in the disappearance of features of tachyarrhythmias. | * During tachyarrythmias, the [[accessory pathway]] forms part of the reentry circuit that results in the disappearance of features of tachyarrhythmias. |
Revision as of 09:26, 24 June 2020
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1], Associate Editor-In-Chief: Shivam Singla, M.D.[2]
Overview
Pre-excitation syndrome is a condition where ventricles of the heart become depolarized too early, which leads to their partially premature contraction.
Normally, the atria (chambers taking venous blood) and the ventriculi (chambers pro-pulsing blood towards organs) are electrically isolated, and only electrical passage exists at "atrioventricular node". In all pre-excitation syndromes, there is at least one more conductive pathway is present. Physiologically, the electrical depolarization wave 'waits' in atrioventricular node to allow atria contract before ventriculi. However, there is no such property exists in abnormal pathway, so electrical stimulus passes to ventricle by this tracts far before normal atrioventricular-his system, and ventricles are depolarized (excited) before (pre-) normal conduction system. The term pre-excitation derives from this condition.
It is usually caused by a secondary conduction pathway (other than the bundle of His).
Historical Perspective
- First described by Louis Wolff, John Parkinson and Paul Dudley White in 1930
- They found the association of these conditions with a small risk of sudden cardiac death
Classification
- pre-excitation syndrome may be classified into sub-types
Type | Conduction pathway | PR interval | QRS interval | Delta wave? |
Wolff-Parkinson-White syndrome | Bundle of Kent (atria to ventricles) | short | long | yes |
Lown-Ganong-Levine syndrome | "James bundle" (atria to bundle of His) | short | normal | no |
Mahaim-type | Mahaim fibers | normal | long |
WPW Syndrome
WPW is a combination of the presence of congenital accessory pathways along with episodic tachyarrhythmias. Here the accessory pathways are referred to as Bundle of Kent or AV bypass tracts.
The features of pre-excitation are subtle, intermittent, and are aggravated by an increase in vagal tone ( Valsalva maneuver, AV blockage by drugs).
ECG Features of WPW
- Shortened PR interval (Less than 120ms)
- Delta wave – slow/slurring in the rise of an initial portion of the QRS
- Widening of QRS complex
- ST Segment and T wave discordant changes – i.e. in the opposite direction to the major component of the QRS complex
- WPW is mainly categorized as type A or B.
- Type A: positive delta wave in all precordial leads with R/S > 1 in V1
- Type B: negative delta wave in leads V1 and V2
Lown-Ganong-Levine (LGL) Syndrome
Here the Accessory pathway are composed of James fibers.
ECG features:
- PR interval <120ms
- Normal QRS morphology
The important point to be noted is that this tern is not relevant or shouldn't be used in the absence of paroxysmal tachycardia. Its existence is disputed and it may not exist.
Mahaim-Type Pre-excitation
Right-sided accessory pathways connecting either AV node to ventricles, fascicles to ventricles, or atria to fascicles
ECG features:
- Sinus rhythm ECG may be normal
- May result in variation in ventricular morphology
- Reentry tachycardia typically has LBBB morphology
Pathophysiology
- Pathophysiology of Pre-Excitation syndrome
- Pre-excitation refers to the early activation of the ventricles as a result of impulses bypassing the AV node via an accessory pathway. The latter are abnormal conduction pathways formed during cardiac development. These can conduct impulses either
- towards ventricles (Anterograde conduction, rarely seen) ,
- Away from the ventricles (Retrograde conduction, in approx 15%),
- in both the directions ( Majority of cases).
- In WPW syndrome which is a type of pre-excitation syndrome the abnormal conduction pathways are called Bundle of Kent or AV bypass tract.
- The accessory pathways facilitate the formation of Tachyarrhythmias by mainly forming a reentry circuit, termed as AVRT (80%). Even in cases of direct conduction through the accessory pathways from A to V ( Bypassing AV node), there can be the resultant formation of Tachyarrhythmias, seen most frequently in the condition of A. Fib with RVR.
- Pre-excitation refers to the early activation of the ventricles as a result of impulses bypassing the AV node via an accessory pathway. The latter are abnormal conduction pathways formed during cardiac development. These can conduct impulses either
Clinical Features
People with Pre- Excitation syndromes may be asymptomatic, however, the individual may experience following symptoms
- Palpitations
- Dizziness or lightheadedness.
- Shortness of breath.
- Chest pain
- Fatigue.
- Anxiety.
- Fainting
- Difficulty breathing
Differentiating Pre-excitation Syndrome from other Diseases
Arrhythmia | Rhythm | Rate | P wave | PR Interval | QRS Complex | Response to Maneuvers | Epidemiology | Co-existing Conditions | |
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'Atrial Fibrillation (AFib)'''' |
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Atrial Flutter |
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Atrioventricular nodal reentry tachycardia (AVNRT)''''''' |
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'Multifocal Atrial Tachycardia'''' |
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Paroxysmal Supraventricular Tachycardia |
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Premature Atrial Contractrions (PAC) |
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'Wolff-Parkinson-White Syndrome'''' |
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Ventricular Fibrillation (VF) |
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Ventricular Tachycardia |
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Epidemiology and Demographics
- Incidence 0.1 – 3.0 per 1000
- LGL syndrome is a rare Man > woman.
- prognosis is good with SCD is noted in only 0.1% (rare)
Risk Factors
High risk population for sudden cardiac death in Wolff-Parkinson-White syndrome include:
- Policemen
- Athletes
- Firemen
- Pilots
- Steelworkers
Risk factors for the development of atrial fibrillation in WPW syndrome include:
- Male gender
- Age (peak ages for the development of atrial fibrillation include 30 years and 50 years)
- Past history of syncope
Natural History, Complications and Prognosis[edit | edit source]
- The majority of patients with [disease name] remain asymptomatic for [duration/years].
- Early clinical features include [manifestation 1], [manifestation 2], and [manifestation 3].
- If left untreated, [#%] of patients with [disease name] may progress to develop [manifestation 1], [manifestation 2], and [manifestation 3].
- Common complications of [disease name] include [complication 1], [complication 2], and [complication 3].
- Prognosis is generally [excellent/good/poor], and the [1/5/10year mortality/survival rate] of patients with [disease name] is approximately [#%].
Diagnosis
Atrioventricular Reentry Tachycardia's (AVRT)
AVRT is a form of PSVT. Reentry circuit results from the combination of signal transduction from normal conduction system and accessory pathway.( See: Diagram)[1]
- During tachyarrythmias, the accessory pathway forms part of the reentry circuit that results in the disappearance of features of tachyarrhythmias.
- AVRT are further divided into
- Orthodromic or Antidromic conduction based on ECG morphology and direction of formation of re-entry circuit.
1) AVRT with Orthodromic Conduction
In this, the anterograde conduction occurs via the AV node and retrograde conduction occurs via an accessory pathway.
ECG features of AVRT with orthodromic conduction
- Rate usually 200 – 300 bpm
- P waves may be buried in QRS complex or retrograde
- QRS Complex usually <120 ms unless pre-existing bundle branch block, or rate-related aberrant conduction
- QRS Alternans – phasic variation in QRS amplitude associated with AVNRT and AVRT, distinguished from electrical altrens by a normal QRS amplitude
- T wave inversion common
- ST segment depression
2) AVRT with Antidromic Conduction
In this, the anterograde conduction occurs via the accessory pathway and retrograde conduction via the AV node. Occurring only in-app. 5% of patients with WPW.
ECG features are:
- Rate usually 200 – 300 bpm.
- Wide QRS complexes due to abnormal accessory pathway ventricular depolarisation.
- Due to wide complex, Commonly mistaken for Ventricular Tachycardia.
3) Atrial Fib/Atrial Flutter in WPW
- In 20% of the patients WPW Atrial fibrillation can occur and in approx 7% of patients with WPW atrial flutter can occur. Accessory pathways plays major role by allowing the rapid conduction of impulses directly to the ventricles without involving AV node, in extreme cases may lead to VT or VF.
ECG features are:
- Rate > 200 bpm
- Irregular rhythm
- Wide QRS complexes due to abnormal ventricular depolarisation via an accessory pathway
- QRS Complexes change in shape and morphology
- Axis remains stable unlike Polymorphic VT
- Atrial Flutter presents with same features as atrial fibrillation in WPW except rhythm is regular and commonly mistaken for VT
Treatment
Medical Treatment
Orthodromic AVRT
- Hemodynamically Unstable patients (Low BP, Altered mental state, pulmonary edema)- Synchronized DC Cardioversion.
- Hemodynamically stable- Vagal maneuvers, Adenosine, CCB, and DC cardioversion as a last resort only if the patient not responding to medical therapy.
Antidromic AVRT
- Hemodynamically unstable patients:- Urgent synchronized DC cardioversion.
- Hemodynamically stable patients:- Amiodarone, procainamide, or ibutilide.
AF with WPW
- Hemodynamically unstable patients: Urgent synchronized DC cardioversion
- Hemodynamically stable patients:- Procainamide or ibutilide.
- Caution: Adenosine, CCB, Beta blockers enhances conduction via accessory pathway resulting in worsening & possible degeneration into VT or VF
Surgery
- Surgery is the mainstay of therapy for [disease name].
- [Surgical procedure] in conjunction with [chemotherapy/radiation] is the most common approach to the treatment of [disease name].
- [Surgical procedure] can only be performed for patients with [disease stage] [disease name].
Prevention
For preventing the recurrence of episodes major options available are
- Radio frequency ablation
- Ablation of accessory pathway tracts
- cures 95% of the time
- Surgery.
- Success rate for surgical ablation is around 100 percent along with lower complication rates. Radiofrequency ablation is a less invasive option and preferred over surgery.
- Surgery can be considered if a patient is undergoing cardiac surgery for other reasons such as CABG or other heart valve surgery.
- Medications
- Although Medications can prevent recurrent episodes of tachycardia they are only used on patients who are not the candidates for ablation or surgery.
- These patients must be taught to perform Valsalva maneuvers that can relieve tachycardia during the episodes.