From the Guidelines
The most likely mechanism of arrhythmia in a patient with tachycardia, shortness of breath, and a delta wave on ECG is Wolff-Parkinson-White (WPW) syndrome, which involves an accessory electrical pathway between the atria and ventricles that bypasses the normal atrioventricular (AV) node conduction system. This condition is characterized by the presence of a delta wave on ECG, which represents pre-excitation of the ventricles through the accessory pathway, known as the Bundle of Kent 1. In WPW syndrome, electrical impulses can travel down both the normal and accessory pathways, creating a reentry circuit that often leads to atrioventricular reentrant tachycardia (AVRT) 1.
Key Characteristics of WPW Syndrome
- The delta wave on ECG is a hallmark of WPW syndrome, indicating pre-excitation of the ventricles through the accessory pathway 1
- The accessory pathway allows electrical signals to bypass the normal delay at the AV node, resulting in faster ventricular activation and potentially dangerous rapid heart rates 1
- AVRT is the most common arrhythmia associated with WPW syndrome, accounting for 95% of re-entrant tachycardias that occur in patients with an accessory pathway 1
Treatment and Management
- Catheter ablation is a recommended treatment for WPW syndrome, as it can eliminate the accessory pathway and prevent further arrhythmias 1
- Medications like flecainide, propafenone, or amiodarone may be used to control symptoms, but patients with WPW should avoid AV nodal blocking agents like beta-blockers, calcium channel blockers, and digoxin when in atrial fibrillation, as these can paradoxically increase ventricular rate by favoring conduction through the accessory pathway 1
- The decision to proceed with catheter ablation should be based on the individual patient's risk of arrhythmic events, as well as their symptoms and quality of life 1
Risk Stratification and Prevention
- Patients with WPW syndrome are at risk of sudden cardiac death, although the incidence is estimated to be low, ranging from 0.15% to 0.39% over 3- to 10-year follow-up 1
- Risk stratification using electrophysiological studies can help identify patients at high risk of arrhythmic events, and guide treatment decisions 1
- Patients with asymptomatic pre-excitation who have a high-risk occupation, such as pilots, may be considered for catheter ablation to prevent arrhythmic events 1
From the Research
Mechanism of Arrhythmia
The patient's symptoms of tachycardia, shortness of breath, and the presence of a delta wave on electrocardiogram (ECG) suggest Wolff-Parkinson-White (WPW) syndrome as the most likely diagnosis.
- The delta wave is a characteristic electrocardiographic finding in WPW syndrome, indicating preexcitation of the ventricular myocardium via an accessory pathway 2.
- The accessory pathway in WPW syndrome bypasses the atrioventricular (AV) node, creating a direct electrical connection between the atria and ventricles, which can lead to tachyarrhythmias 3.
- The most common tachyarrhythmias associated with WPW syndrome are orthodromic and antidromic reciprocating tachycardia and atrial fibrillation, which can cause symptoms such as tachycardia and shortness of breath 4.
Pathophysiology
The pathophysiology of WPW syndrome involves the congenital presence of impulse-conducting fascicles, known as accessory pathways (APs) or bypass tracts, which connect atria and ventricles across the annulus fibrosis and are capable of preexciting portions of the ventricular myocardium 3.
- The accessory pathway can conduct impulses in both anterograde (from atria to ventricles) and retrograde (from ventricles to atria) directions, leading to reentrant tachycardias 3.
- The presence of an accessory pathway can also lead to atrial fibrillation, which can be life-threatening if it degenerates into ventricular fibrillation 2.
Diagnostic and Therapeutic Considerations
The diagnosis of WPW syndrome is based on electrocardiographic findings, including a short PR interval, presence of a delta wave, widened QRS complex, and ST-T wave changes 4.