Supraventricular tachycardia (SVT)

This is a common condition and mostly affects younger otherwise healthy people. It is most often due to an extra electrical connection between the top and the bottom chambers of the heart. These extra connections may be distinct from the normal wiring of the heart (Accessory pathway/AVRT) or part of the normal conduction system itself (AVNRT). The two connections may ‘short circuit’ from time to time causing the heart to beat fast (between 150 and 250 times a minute). The patient experiences sudden onset of palpitations which may last for minutes to hours. Because of the episodic nature of SVT, some of these patients are initially misdiagnosed as suffering from anxiety or panic attacks for many years. The condition can be controlled with drugs, but most patients prefer the one-off curative catheter ablation to life-long tablets. Results of catheter ablation are excellent (success rates greater than 90%, serious complication rate <2%) and the patients are home the same day.

Atrial flutter

Atrial flutter is an extremely common condition, especially in older patients. In this, the electrical circuit revolves round and round in the right atrium (the top right chamber of the heart) at the rate of 250-300 beats per minute. The lower chambers, the ventricles follow at rate of 100-150 beats per minute. Patients experience breathlessness, palpitations and fatigue. Atrial flutter tends to be persistent and is often impossible to treat satisfactorily with drugs. Flutter often coexists with atrial fibrillation.

The condition can easily be cured with catheter ablation (success rates >90%) in which the cardiologist commonly uses radiofrequency energy to interrupt the flutter circuit

Atrial fibrillation

In atrial fibrillation (AF), the sinus node is no longer regulating the electrical activation of the atria. Instead, chaotic, swirling wavefronts of electrical activation pass through the atria. The drivers of this rhythm often arise in the pulmonary veins that drain blood from the lungs and plumb into the back of the left atrium. Hence, AF normally originates in the left atrium.

During AF the atria are not activated regularly or uniformly. As a result, the atria do not pump efficiently. Instead they fibrillate or ‘wobble’, resulting in stagnant blood flow within the atria, reduced blood flow from the atria to the ventricles and a chaotic irregular pulse.

Reduced flow during AF may lead to formation of blood clots in the left atrium of susceptible patients, in turn giving rise to a risk of stroke. Not all patients are at risk of stroke, and the risk may be significantly reduced through thinning of the blood with drugs such as warfarin or other newer blood thinning drugs.

Reduced flow also reduces the pumping efficiency of the heart. This can make people breathless and fatigued. The irregular and often fast heartbeat during atrial fibrillation may also cause uncomfortable palpitations.

AF is described as paroxysmal if it is episodic and self-terminates spontaneously. It is persistent if the patient’s heart is in atrial fibrillation continuously. Types of treatments and their success may differ according to this distinction.

For more information, written specifically for patients, see the Arrhythmia Alliance and AF Association websites:


Blackouts and dizziness can be due to problems with the electrical conducting system of the heart, resulting in either a very slow, or a pause in the normal heart rhythm. These issues can be treated by the implantation of a permanent pacemaker. Leads are inserted through veins in the shoulder, into the heart. These are connected to a very small pulse generator/ battery which is inserted under the skin in the shoulder region. The process is usually straightforward and is performed under local anaesthetic.

Further information is available at the BFH website: