### Date : 2024-11-01 13:41 ### Topic : Wolff-Parkinson-White(WPW) syndrome #cardiology ---- **Wolff-Parkinson-White (WPW) Syndrome** is a condition where an additional electrical pathway, known as an **accessory pathway**, exists between the atria and ventricles. This accessory pathway bypasses the AV node, allowing electrical impulses to travel directly from the atria to the ventricles. WPW can lead to episodes of rapid heart rate (tachycardia) and predisposes to serious arrhythmias. ### 1. **Mechanism of WPW Syndrome** - In WPW syndrome, an **accessory pathway** (also called the Bundle of Kent) connects the atria and ventricles, bypassing the normal AV nodal conduction. - The AV node normally slows down the conduction from atria to ventricles, ensuring controlled ventricular filling. However, in WPW syndrome, the accessory pathway allows **faster conduction**, leading to early ventricular depolarization. - This results in a **pre-excitation of the ventricles**, meaning part of the ventricles depolarize earlier than usual. ### 2. **ECG Characteristics of WPW Syndrome** WPW syndrome has characteristic findings on an electrocardiogram (ECG): - **Short PR Interval**: Due to the bypassing of the AV node, the PR interval (time from atrial to ventricular depolarization) is shortened, typically <0.12 seconds. - **Delta Wave**: This is a slurred upstroke at the beginning of the QRS complex, representing the early depolarization of the ventricles through the accessory pathway.  - **Wide QRS Complex**: The QRS complex is wider than normal due to the fusion of conduction through the accessory pathway and the normal His-Purkinje system. ### 3. **Types of Arrhythmias in WPW Syndrome** The accessory pathway can lead to different types of arrhythmias due to the potential for **reentrant circuits**, where impulses travel in a circular pattern through the normal and accessory pathways: - **Atrioventricular Reentrant Tachycardia (AVRT)**: The most common arrhythmia in WPW, where a reentrant circuit is formed between the accessory pathway and AV node. - **Orthodromic AVRT**: Impulses travel down the AV node and return to the atria via the accessory pathway. This results in a **narrow QRS complex** tachycardia because the ventricles are depolarized through the normal His-Purkinje system. - **Antidromic AVRT**: Impulses travel down the accessory pathway and return via the AV node, causing **wide QRS complex** tachycardia, as the ventricles are depolarized through the accessory pathway. - **Atrial Fibrillation**: In WPW syndrome, AF can be dangerous because the accessory pathway does not have the delay mechanism of the AV node. This allows rapid impulses to pass directly to the ventricles, leading to a **very fast ventricular rate** (sometimes >200 bpm), which can result in **ventricular fibrillation** and sudden cardiac death. ### 4. **Symptoms** Symptoms of WPW can vary, but during an episode of tachycardia, patients may experience: - **Palpitations**: Feeling of a racing or fluttering heartbeat. - **Dizziness or Lightheadedness**: Due to reduced cardiac output during rapid heart rates. - **Shortness of Breath**: Particularly in prolonged episodes. - **Chest Pain**: Especially if the heart is unable to pump effectively during tachycardia. - **Syncope**: In rare cases, if the heart rate is excessively fast, blood flow to the brain may be reduced. - **Sudden Cardiac Arrest**: Rare but possible, especially during atrial fibrillation with a very high ventricular rate. ### 5. **Diagnosis** - **Electrocardiogram (ECG)**: WPW is typically diagnosed by identifying the characteristic ECG findings (short PR interval, delta wave, wide QRS complex). - **Holter Monitor or Event Recorder**: Continuous ECG monitoring can help capture episodes of tachycardia if they are intermittent. - **Electrophysiological Study (EPS)**: This invasive procedure maps the electrical pathways in the heart to locate the accessory pathway and assess the risk of arrhythmia. It is often done in preparation for ablation. ### 6. **Treatment** Treatment depends on the severity of symptoms and the type of arrhythmia: - **Lifestyle Modifications**: Avoiding stimulants (caffeine, alcohol) and stress, which can trigger arrhythmias. - **Medications**: In some cases, medications can help control heart rate, but care must be taken as some drugs can worsen the condition. - **Avoid AV Node Blockers** (like beta blockers, calcium channel blockers, and digoxin) in patients with atrial fibrillation and WPW. These drugs slow AV nodal conduction, which can encourage faster conduction through the accessory pathway, increasing the risk of ventricular fibrillation. - **Antiarrhythmics**: *Procainamide* or *ibutilide* can be used in acute management of AF in WPW syndrome as they work on the accessory pathway. - **Catheter Ablation**: A definitive treatment where the accessory pathway is ablated (destroyed) using radiofrequency energy or cryoablation. This is often recommended for patients with symptomatic WPW, those at high risk of sudden cardiac death, or those who cannot tolerate medications. - **Emergency Management**: - In cases of **unstable arrhythmia** (e.g., atrial fibrillation with a rapid ventricular response leading to hemodynamic instability), **electrical cardioversion** is required to restore a normal rhythm. - **Antiarrhythmic drugs** like procainamide or ibutilide may be used in acute settings for atrial fibrillation in WPW, especially if the patient is stable. ### 7. **Prognosis and Risk of Sudden Cardiac Death** - WPW itself is not always dangerous, but patients with WPW and atrial fibrillation are at risk of life-threatening arrhythmias due to rapid ventricular rates. - Those with a history of syncope, a very short refractory period of the accessory pathway, or a family history of sudden cardiac death may have a higher risk and are often recommended for catheter ablation. ### Summary - **WPW Syndrome** involves an accessory pathway that bypasses the AV node, leading to pre-excitation of the ventricles. - **Characteristic ECG Findings**: Short PR interval, delta wave, and wide QRS complex. - **Arrhythmias**: AVRT (orthodromic and antidromic) and atrial fibrillation with rapid ventricular response. - **Treatment**: Avoid AV node blockers in AF; consider catheter ablation for definitive treatment. ### Reference: - ### Connected Documents: -