Causes and risk factors
Heart rate is controlled by electrical signals passing across the heart tissues. Heart is made up of primarily muscle tissue. A network of nerve fibres regulates contraction and relaxation of heart muscles to obtain wave like pumping action of heart. Electrical signals are generated by SA node placed in the right atrium of heart. Autonomic nervous system controls the rate of signals sent by SA node. Electric signals follow the following pathway in the heart – SA node, Atrioventricular node, bundle of HIS, right and left bundle branch, purkinje fibres. AV node conducts impulses from atria to ventricles. In WPW syndrome there is an extra connection in the electrical pathway of heart since birth called as accessory pathway. It allows impulses to bypass AV node, and pass from atria to ventricle in a faster than usual. The accessory pathway may also transfer signals from ventricles back to atria. These extra electrical impulses cause disruption in normal pumping action of heart causing it to beat faster i.e. arrhythmia and tachycardia. Caffeine and other stimulants can trigger the condition.
Clinical presentation
Symptoms of WPW syndrome include dizziness, palpitations. Patient experiences light-headedness, anxiety, tiring during exercise, fatigue. Arrhythmia and tachycardia are the main alarming signs of the disease. Patient complains of chest pain, tightness of chest, shortness of breath. If undiagnosed, WPW syndrome can lead to sudden cardiac arrest and death.
Investigation
Medical history by the patient and Clinical examination by the doctor helps in diagnosis. Blood tests for potassium levels and thyroid hormones is recommended. An ECG is advised. Holter monitoring can be done [24 hours monitoring of electrical activity of heart]. Imaging studies such as chest X ray may be useful. Electrophysiological testing may be useful in the diagnosis of the condition.
Treatment
Regularising heart beat by methods such as vagal manoeuvre [putting ice pack on face, bearing down as if defecating or coughing] is required. Medications like anti arrhythmic drugs may be required to correct increased heart rate. When above treatment is not helpful, cardioversion is applied i.e. electric current is administered in the heart which restores normal heart rhythm. Surgical treatment to prevent tachycardia involves catheter ablation, pacemaker, implantable cardioverter defibrillator, open heart surgery.
