As many as one person in a hundred may experience an episode of sudden racing of the heart. Typically the onset is abrupt and the person may notice the clothing over the chest moving rapidly as well as feeling the fast heart beat. Typical heart rates are 160 to 220 beats per minute. Sometimes there is associated tightness in the chest, lightheadedness or breathlessness. The episode may stop spontaneously, or the patient may have learnt some “tricks” to stop it, such as breath holding or massaging their neck.
Reassuringly, although a first occurrence may be alarming, such episodes are rarely due to structural heart disease, but rather are an electrical "short-circuit" somewhere in the heart. If episodes last more than 15 minutes it is prudent to seek medical attention and very helpful for subsequent management to have the rhythm documented on a full electrocardiogram. No special treatment may be necessary for infrequent episodes. When episodes are recurrent and intrusive, the cause may usually be discovered with a procedure called an electrophysiology study. This involves recording electrical signals from inside the heart with electrode catheters using local anaesthesia.
The two most common causes found are a short-circuit in the filter in the middle of the heart (called the AV node and the problem AV nodal re-entrant tachycardia) or an extra electrical cable called an accessory pathway. When evidence of an accessory pathway is visible on the ECG, the problem is called Wolf-Parkinson-White syndrome. The problem is often fixed at the same time as diagnosis by “knocking out “ a small part of the faulty electrical circuit with a treatment called radiofrequency ablation. Patients can often go home the same day after such a procedure or may stay overnight.
Uncommonly the fast heart beat may arise from the lower pumping chambers (the ventricles) and additional investigations may then be warranted.