The heart is a muscular pump, circulating blood to deliver oxygen and nutrients. Its rhythmic contractions are regulated by an electrical system. Pre-excitation syndrome is a condition where an abnormal electrical connection allows signals to bypass normal pathways. This extra pathway can cause ventricles to activate prematurely, leading to abnormal heart rhythms.
The Heart’s Electrical Shortcuts
Normal electrical activity begins in the sinoatrial (SA) node, the heart’s natural pacemaker, located in the upper right chamber (atrium). The impulse spreads across the atria, causing them to contract, before reaching the atrioventricular (AV) node.
The AV node delays the electrical signal, allowing atria to empty blood into the ventricles before they contract. The signal then travels through the bundle of His and Purkinje fibers, rapidly spreading to the ventricles and prompting their contraction.
In pre-excitation syndrome, an “accessory pathway” is an extra strand of muscle tissue directly connecting the atria and ventricles, bypassing the AV node. This pathway lacks the AV node’s delaying properties, allowing impulses to travel faster and activate ventricles earlier. Wolff-Parkinson-White (WPW) syndrome is the most common type, characterized by such a pathway enabling premature ventricular activation.
Common Indicators
Individuals with pre-excitation syndrome may experience various indicators; some have no symptoms. The most common is heart palpitations, described as a fluttering, pounding, or racing sensation. These rapid heartbeat episodes can begin suddenly and last from seconds to hours.
Other indicators include dizziness or lightheadedness, often due to inefficient pumping during rapid rhythms. Some individuals may also experience shortness of breath, chest pain, or fatigue. Fainting (syncope) can occur, especially if the heart rate becomes extremely rapid.
Identifying the Condition
Diagnosis relies on an electrocardiogram (ECG or EKG), a non-invasive test recording the heart’s electrical activity. In pre-excitation, the ECG often shows specific patterns: a shortened PR interval and a “delta wave.” The delta wave is a characteristic slurring or sloped upstroke at the beginning of the QRS complex, indicating premature ventricular activation through the accessory pathway.
While the ECG provides initial evidence, a doctor may recommend an electrophysiology (EP) study for detailed assessment. During an EP study, thin wires are guided through blood vessels into the heart to map its electrical activity and identify the accessory pathway’s location and properties. This test helps determine if the pathway conducts signals rapidly, which is important for assessing risks and guiding treatment.
Treatment Approaches
Management varies depending on symptoms and the accessory pathway’s assessed risk. For asymptomatic individuals with a low-risk pathway, close observation may be appropriate. However, if symptoms occur or the pathway poses a higher risk of dangerous arrhythmias, treatment becomes necessary.
Medication, such as antiarrhythmic drugs, can control heart rhythm and prevent rapid heartbeats. These medications affect the heart’s electrical signals, though long-term efficacy and side effects are considered.
Catheter ablation is a common, often curative treatment. This procedure guides a catheter to the heart, using radiofrequency energy (heat) or cryoablation (cold) to create a small scar that blocks unwanted electrical signals through the accessory pathway. Catheter ablation has a high success rate, often eliminating the extra pathway and reducing future arrhythmia risk. Treatment choice depends on symptoms, pathway characteristics, and overall health.