What is the Wolff-Parkinson-White syndrome?
Wolff-Parkinson-White syndrome (WPW) is a syndrome of pre-excitation of the ventricles due to an accessory pathway known as the bundle of Kent. This accessory pathway is an abnormal electrical communication from the atria to the
Unlike the AV node, which is the normal electrical pathway from the atria to the ventricles, the accessory pathway in WPW does not have slow conductive properties. This means that electrical activity that originates from the SA node with conduct to the ventricles faster via the accessory pathway than via the AV node. This causes the characteristic EKG pattern consisting of a delta wave at the beginning of the QRS complex. The delta wave is due to pre-excitation of the ventricle due to anterograde conduction via the accessory pathway. The EKG will exhibit a short PR interval and a widened QRS interval.
Patients with WPW often exhibit more than one accessory pathway, and in some patients as many as eight additional abnormal pathways can be found. Though it can be treated with medication, in the long term the treatment of choice is destruction of the abnormal electrical pathway by radiofrequency catheter ablation. Wolff-Parkinson-White syndrome is sometimes caused by Leber hereditary optic neuropathy (LHON), a form of mitochondrial disease.
Blood is circulated through the heart and body by a muscular pump and valve system involving the atria and ventricles. The right atrium receives oxygen-lacking blood returning to the heart from the body. The blood is passed from the right atrium into the right ventricle, which contracts and sends blood out to the pulmonary artery. The pulmonary artery sends the blood into the lungs, where carbon dioxide is removed, and fresh oxygen is added. The left atrium receives blood with oxygen from the lungs and passes this arterial blood to the left ventricle, where it is emptied into the aorta, the main artery of the heart.
These functions are directed by electrical signals within the heart. In patients afflicted with Wolff-Parkinson-White syndrome, an abnormal pathway exists that causes additional electrical signals to pass between the atria and ventricles, possibly causing rapid heart rate.
Wolff-Parkinson-White syndrome is characterised by attacks of rapid heart rate (tachycardia). The heartbeat is regulated by electrical impulses that travel through the atria (upper chambers of the heart) to a knot of tissue known as the atrioventricular node, and then to the ventricles (lower chambers of the heart). Usually, electrical impulses pause at the atrioventricular node before prompting the ventricles to contract. In Wolff-Parkinson-White syndrome, an extra pathway conducts the electrical impulses to the ventricles, without the normal delay, or bounces the electrical impulses back to the atria. The heart rate can reach over 200 beats per minute, when the normal resting heart rate is around 70 to 80 or so. Four out of every 100,000 people are thought to have Wolff-Parkinson-White syndrome. The condition can be managed with medications and surgery.