Tachycardia-induced cardiomyopathy

The heart fills between beats. At very fast rates there is less time to fill and the muscle has less time to rest and receive its own blood supply, while irregular rhythms also reduce the efficiency of each contraction. Over weeks and months these effects can dilate the left ventricle and reduce ejection fraction. The BHF describes atrial fibrillation as a common abnormal rhythm that causes the heart to beat irregularly and often too fast, and the NHS lists heart failure among its complications.

Tachycardia-induced cardiomyopathy is a diagnosis that is often made in retrospect, once the heart recovers after the rhythm is controlled. It can also be superimposed on pre-existing heart disease, in which case recovery may be partial.

Atrial fibrillation is the commonest cause because it is common and often persistent. Atrial flutter with fast conduction, atrial tachycardia and some supraventricular tachycardias can do the same. Frequent premature ventricular beats, when they account for a large proportion of all heartbeats, can also weaken the heart, and in that situation ablation of the origin may be considered. Persistent fast rhythms in children, though rarer, can occur and are treated by specialist paediatric cardiologists.

• Atrial fibrillation or flutter with fast ventricular rates.

• Atrial tachycardia or supraventricular tachycardia that is persistent.

• Very frequent ventricular ectopic beats.

• Long-lasting rapid pacing or ventricular tachycardia.

The NHS lists AF symptoms as palpitations, tiredness, breathlessness and chest discomfort, though some people have none. When the heart weakens, heart failure features are added: breathlessness on exertion, swelling, weight gain and reduced exercise capacity. Diagnosis involves an ECG, longer rhythm monitoring if the rhythm is intermittent, blood tests including thyroid function and natriuretic peptide, and an echocardiogram showing the ventricle size and ejection fraction. Cardiac MRI can help distinguish tachycardia-induced disease from other cardiomyopathies by showing a lack of scar.

The NHS describes cardiomyopathy as having several types and causes, many inherited, so the label is applied only after other possibilities such as coronary disease, valve disease or inherited cardiomyopathy are considered.

The core approach is to control the rhythm. Medicines such as beta-blockers slow the rate, and anti-arrhythmic drugs may restore or maintain normal rhythm. The NHS and BHF describe cardioversion, an electrical reset, and catheter ablation, which destroys small areas of heart tissue that trigger or sustain the arrhythmia. In people who cannot be controlled, a procedure that closes off the electrical connection between atria and ventricles followed by pacing may be considered.

Standard heart failure medicines are used alongside while the muscle recovers, and anticoagulation is decided by stroke risk when atrial fibrillation is present. Improvement is often seen within weeks to a few months, and a repeat echocardiogram is used to document it.

Many people regain near-normal heart function. However, the heart can remain vulnerable, so if the arrhythmia returns, heart function can fall again, sometimes quickly. Because of that, people who have recovered are usually advised to continue some heart failure medicines for a period and to keep in regular contact with cardiology services. Lifestyle measures such as weight loss, limiting alcohol, treating sleep apnoea and managing blood pressure reduce the chance of recurrence.

Seek prompt medical advice for sustained palpitations, a resting heart rate that is persistently very fast, new breathlessness or swelling. Call 999 for chest pain, fainting, severe breathlessness or stroke symptoms. The NHS advises notifying the DVLA if driving is affected.