Accessory pathway

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No.	Summary table on Accessory Pathways in cardiology
1	Accessory pathways are abnormal electrical connections between atria and ventricles.
2	The most common accessory pathway disorder is Wolff-Parkinson-White (WPW) syndrome.
3	Accessory pathways can conduct impulses antegradely, retrogradely, or both.
4	Preexcitation on ECG appears as a delta wave — slurred upstroke of the QRS complex.
5	Short PR interval (<120 ms) is a hallmark of accessory pathway conduction.
6	AVRT (Atrioventricular Reentrant Tachycardia) is the most common arrhythmia due to accessory pathways.
7	Orthodromic AVRT uses the AV node antegradely and the accessory pathway retrogradely.
8	Antidromic AVRT uses the accessory pathway antegradely and the AV node retrogradely, producing wide QRS complexes.
9	Patients with WPW are at risk of rapid conduction during atrial fibrillation, leading to ventricular fibrillation.
10	Adenosine or AV nodal blockers can worsen preexcited AF and must be avoided in WPW.
11	Procainamide or ibutilide is preferred for acute management of preexcited AF.
12	Definitive treatment of symptomatic accessory pathways is catheter ablation.
13	Right-sided accessory pathways produce negative delta waves in V1.
14	Left-sided accessory pathways may mimic lateral MI due to Q waves in lateral leads.
15	Concealed accessory pathways conduct only retrogradely and don’t show delta waves.
16	Multiple accessory pathways are common in patients with Ebstein anomaly.
17	Post-ablation ECG shows normalization of PR interval and loss of delta waves.
18	Risk stratification in asymptomatic WPW includes EP study to assess inducibility.
19	Wenckebach phenomenon does not protect against arrhythmias in WPW patients.
20	ECG algorithms and vector analysis can help localize the site of accessory pathways.

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Most common sites for accessory pathways

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[A] Atrio-ventricular pathways
[B] Atrio-fascicular pathways
[C] Nodo-ventricular pathways
[D] Fasciculo-ventricular pathways

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Mahaim pathways are typically seen on the

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[A] Left side of the heart
[B] Right side of the heart
[C] Base of the heart
[D] Apex of the heart

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Ventricular connections of Mahaim pathways are located close to

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[A] Left bundle branch
[B] Right bundle branch
[C] Left anterior fascicle
[D] Left posterior fascicle

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What is the type of conduction through a Mahaim pathway

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[A] Concealed Conduction
[B] Fixed Conduction
[C] Ventricular Aberration
[D] Decremental Conduction

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What is the ECG appearance of QRS complexes in case of maximal pre-excitation through a Mahaim pathway as occurs during antidromic atrioventricular re-entrant tachycardia?

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[A] LBBB
[B] RBBB
[C] LAHB
[D] AV Block

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Multiple accessory pathway are more common in

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[A] Ostium Primum ASD
[B] AVSD
[C] Tetralogy of Fallot
[D] Ebstein’s anomaly

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Wolff-Parkinson-White (WPW) pattern includes ALL of the following EXCEPT

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[A] Short PR interval
[B] Delta wave
[C] Tachycardia
[D] Anterograde conduction

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WPW syndrome is a disorder characterized by all of the following EXCEPT

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[A] Preexcitation on the baseline electrocardiogram
[B] At least three accessory pathway that predispose to tachyarrhythmias
[C] Symptomatic tachyarrhythmias
[D] Can cause sudden cardiac death

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Patient with asymptomatic pre-excitation who happen to be competitive athletes is advised to undergo EPS for risk stratification and potential ablation

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[A] Class I
[B] Class IIA
[C] Class IIB
[D] Class III

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A patient with diagnosis of WPW Syndrome planned for Noninvasive Assessment. When injection Ajmalin given the pre-excitation [delta wave] disappeared. Which risk category the patient should beplaced.

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[A] Low risk Category
[B] High risk Category
[C] Intermidiate risk category
[D] Indication for ICD implantation

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Classic triad of electrocardiographic findings in Wolff-Parkinson-White syndrome are all EXCEPT

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[A] Short PR interval
[B] Wide QRS complex
[C] Delta wave
[D] PSVT

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ALL are TRUE about type A pre-excitation EXCEPT

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[A] Right atrioventricular connections
[B] Positive R wave is seen in V1
[C] Positive delta
[D] RR intervals of less than 250 ms suggest a higher risk pathway

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What is the name of accessory pathway in WPW Syndrome?

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[A] Bundle of Kent
[B] Bachmann bundle
[C] Purkinje fibers
[D] Mahaim accessory pathways

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Most common congenital heart defect associated with Wolff-Parkinson-White syndrome

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[A] ASD
[B] VSD
[C] Tetralogy Of Fallot
[D] Ebstein anomaly

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ECG features of WPW in sinus rhythm

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• PR interval < 120ms
• Delta wave: slurring slow rise of initial portion of the QRS
• QRS prolongation > 110ms
• Discordant ST-segment and T-wave changes (i.e. in the opposite direction to the major component of the QRS complex)
• Pseudo-infarction pattern in up to 70% of patients — “pseudo-Q waves” or prominent R waves in V1-3 (mimicking posterior infarction)

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1. What is an accessory pathway?

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➡ It is an abnormal electrical connection between atria and ventricles.

➡ Bypasses the AV node.

➡ Causes pre-excitation of the ventricles.

➡ Can lead to tachyarrhythmias.

➡ Seen in WPW and other syndromes.

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2. What are the ECG features of WPW syndrome?

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➡ Short PR interval (<120 ms).

➡ Delta wave (slurred upstroke of QRS).

➡ Widened QRS complex (>120 ms).

➡ Secondary ST-T changes.

➡ Evidence of ventricular pre-excitation.

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3. What is orthodromic AVRT?

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➡ Reentrant tachycardia using AV node anterogradely.

➡ Accessory pathway used retrogradely.

➡ Narrow QRS tachycardia.

➡ Most common form of AVRT in WPW.

➡ Responds to vagal maneuvers and adenosine.

4. What is antidromic AVRT?

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➡ Reentrant tachycardia using accessory pathway anterogradely.

➡ AV node used retrogradely.

➡ Wide QRS tachycardia.

➡ Less common than orthodromic AVRT.

➡ May resemble VT on ECG.

5. Why is AV nodal blocking dangerous in WPW with AF?

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➡ It blocks the AV node.

➡ Forces conduction via accessory pathway.

➡ Can lead to 1:1 conduction of atrial impulses.

➡ Results in very high ventricular rates.

➡ Increases risk of ventricular fibrillation and sudden death.

6. What drugs are preferred in WPW with AF?

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➡ Procainamide.

➡ Ibutilide.

➡ Avoid AV nodal blockers (e.g., digoxin, beta-blockers).

➡ Cardioversion if unstable.

➡ Catheter ablation for long-term treatment.

7. What is a concealed accessory pathway?

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➡ Conducts only retrogradely.

➡ No delta wave or pre-excitation on baseline ECG.

➡ Can participate in reentry circuits.

➡ Detected during electrophysiological studies.

➡ Causes paroxysmal SVT.

8. What is the definitive treatment for symptomatic accessory pathways?

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➡ Radiofrequency catheter ablation.

➡ Performed during EP study.

➡ Targets pathway location.

➡ High success rate.

➡ Minimal recurrence risk.

9. What are Mahaim fibers?

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➡ Rare accessory pathways.

➡ Typically right-sided.

➡ Show decremental conduction.

➡ Cause wide complex tachycardias.

➡ Mimic ventricular tachycardia.

10. How does pre-excitation affect ECG interpretation in MI?

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➡ Can mask or mimic infarction patterns.

➡ Delta wave distorts QRS morphology.

➡ May lead to false diagnosis of MI.

➡ Requires careful evaluation.

➡ Compare with old ECGs or use EP study.

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What is an accessory pathway?

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1. It is an abnormal electrical connection between atria and ventricles.
2. Bypasses the AV node, causing pre-excitation of ventricles.
3. Can lead to re-entrant tachyarrhythmias like AVRT.
4. Most commonly seen in Wolff-Parkinson-White (WPW) syndrome.
5. May be congenital and vary in number or location.

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Name a condition commonly associated with accessory pathways.

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1. Wolff-Parkinson-White (WPW) syndrome is the most well-known.
2. It involves the Bundle of Kent as the accessory tract.
3. Characterized by short PR interval and delta wave on ECG.
4. Can cause AVRT or even atrial fibrillation with fast conduction.
5. May be asymptomatic or present with palpitations and syncope.

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How does WPW syndrome appear on ECG?

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1. Shortened PR interval (<120 ms).
2. Presence of a delta wave (slurred upstroke of QRS).
3. QRS duration is prolonged (>110 ms).
4. Secondary ST-T changes may be seen.
5. Suggests pre-excitation of ventricles due to bypass tract.

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What is AVRT?

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1. AVRT stands for Atrioventricular Reentrant Tachycardia.
2. It is a reentrant circuit involving the AV node and accessory pathway.
3. Can be orthodromic (narrow QRS) or antidromic (wide QRS).
4. Triggered by a premature beat that initiates the loop.
5. Frequently seen in WPW syndrome.

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Differentiate orthodromic vs antidromic AVRT.

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1. Orthodromic: impulse travels down AV node, up accessory path.
2. Antidromic: impulse travels down accessory path, up AV node.
3. Orthodromic has narrow QRS; antidromic has wide QRS.
4. Orthodromic is more common in WPW cases.
5. Both may cause palpitations, dizziness, or syncope.

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What is the Bundle of Kent?

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1. It is a congenital accessory pathway in WPW syndrome.
2. Connects atria to ventricles directly, bypassing AV node.
3. Can conduct impulses rapidly causing pre-excitation.
4. May be located left-sided or right-sided.
5. Ablation of this tract can cure WPW syndrome.

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What is the treatment for symptomatic WPW?

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1. Initial: vagal maneuvers or adenosine for AVRT termination.
2. Definitive: radiofrequency catheter ablation of the pathway.
3. Beta-blockers or calcium channel blockers may help.
4. Procainamide can be used for wide QRS tachycardia.
5. Avoid AV nodal blockers in atrial fibrillation with WPW.

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Why avoid AV nodal blockers in AF with WPW?

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1. They may block AV node and enhance accessory pathway conduction.
2. This can lead to very rapid ventricular rates.
3. Increases risk of ventricular fibrillation and sudden death.
4. Preferred drugs: procainamide or cardioversion.
5. Recognizing delta wave and wide QRS is critical.

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How is accessory pathway localization done?

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1. Based on ECG pattern during pre-excitation or tachycardia.
2. Electrophysiological study provides precise mapping.
3. Helps guide catheter ablation procedure.
4. Some pathways are harder to access anatomically.
5. Success rate of ablation is over 95% in experienced hands.

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Can accessory pathways be multiple?

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1. Yes, multiple accessory tracts may exist in a single patient.
2. Seen in 5–10% of WPW cases.
3. They increase the complexity of tachyarrhythmias.
4. Require detailed mapping and extended ablation time.
5. Recurrence risk is higher with multiple pathways.

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