Understanding heart rhythm disorders

Common · often curable

SVT — Supraventricular Tachycardia

SVT is one of the most common rhythm disturbances we see, and it particularly affects younger, otherwise healthy people. It happens when an extra electrical connection exists somewhere between the heart's upper and lower chambers — either an accessory pathway running alongside the heart's normal wiring (a condition called AVRT), or an extra loop within the normal conduction pathway itself (AVNRT). Either way, the result is the same: an electrical signal can suddenly start looping round this extra connection, driving the heart at a fast, regular rate of anywhere between 150 and 250 beats per minute.

Episodes tend to start and stop abruptly, and can last anywhere from a few minutes to several hours. Because the sensation of a sudden racing heart can be frightening, SVT is quite often mistaken at first for anxiety or a panic attack — particularly when an ECG isn't captured during an episode. Medication can control or prevent episodes, but for most patients a catheter ablation procedure is curative: it has a success rate of over 90%, a serious complication rate of under 2%, and patients typically go home the same day.

Very common · usually treatable with ablation

Atrial flutter

Atrial flutter is very common, especially in older patients. It occurs when an electrical signal gets caught travelling round and round a fixed circuit in the right atrium (the heart's upper right chamber), typically at a rate of 250 to 300 times a minute. Not every one of these signals reaches the ventricles below, but enough do to produce a fast heartbeat of around 100 to 150 beats per minute. The result is often breathlessness, palpitations and fatigue.

Atrial flutter is frequently persistent and can be difficult to control using medication alone, and it often occurs alongside atrial fibrillation. The good news is that, because the problem is usually caused by a single, well-defined electrical circuit, catheter ablation — using radiofrequency energy to interrupt that circuit — is highly effective, curing more than 90% of cases.

Stroke risk · long-term management

Atrial fibrillation (AF)

Normally, the heart's natural pacemaker — the sinus node — sends out a single, orderly signal that spreads evenly through the atria. In atrial fibrillation, this regular control is lost. Instead, chaotic electrical wavefronts sweep through the atria, very often triggered by tissue where the pulmonary veins enter the left atrium. Rather than contracting in a coordinated way, the atria quiver, and blood flow through them becomes sluggish and can pool. This creates a real risk of blood clots forming, which can travel to the brain and cause a stroke — a risk that can be substantially reduced with blood-thinning medication where appropriate.

Because the atria are no longer pumping efficiently, AF also reduces the heart's overall efficiency, which can leave people feeling breathless and tired, on top of an irregular, sometimes uncomfortable pulse. AF is described as paroxysmal when episodes come and go and stop on their own, or persistent when the irregular rhythm continues without stopping — and this distinction has a real bearing on which treatment approach is most appropriate.

Atrial fibrillation causes palpitations in around 2.5% of the UK population, and affects roughly 7 in every 100 people over the age of 65. It matters beyond the symptoms it causes directly: an estimated 30% of strokes may be linked to silent, undiagnosed AF.

For slow rhythms · blackouts & dizziness

Pacemakers

Not every rhythm problem makes the heart go too fast — sometimes the opposite happens. Blackouts, dizzy spells or fainting can be caused by the heart's rhythm running too slowly, or pausing altogether, usually because of a fault somewhere in its natural conducting system. Where this is the underlying cause, the standard and highly effective treatment is a permanent pacemaker.

A pacemaker consists of one or more thin leads, which are guided through a vein near the shoulder into the heart, connected to a small pulse generator — the "battery" — implanted just under the skin, also near the shoulder. Once in place, it monitors the heart's natural rhythm and steps in with a small electrical impulse whenever needed. For most patients this is a straightforward procedure carried out under local anaesthetic.