Cardioversion

What is cardioversion?

Cardioversion is a short, planned procedure that restores a normal heart rhythm when the heart is beating irregularly or too fast, most commonly for atrial fibrillation (AF) or atrial flutter. Under a brief general anaesthetic or deep sedation, a precisely synchronised electrical impulse is delivered through pads on the chest, momentarily resetting the heart's electrical activity so the natural pacemaker can resume normal rhythm. The energy is timed exactly to your heartbeat, which is what distinguishes controlled cardioversion from emergency defibrillation.

Pharmacological cardioversion, using an anti-arrhythmic drug instead of electricity, is an alternative in selected circumstances, though electrical cardioversion is more immediately effective and extremely well tolerated.

When is cardioversion recommended?

Cardioversion is typically advised when AF or flutter is causing symptoms, palpitations, breathlessness, fatigue or reduced exercise capacity, and a rhythm-control strategy is appropriate; when a first or recent episode has not settled on its own; or when restoring normal rhythm will reveal how much of your symptom burden is due to the arrhythmia itself, information that genuinely shapes the long-term plan, including whether catheter ablation is worthwhile.

It is not the right tool for everyone: where AF is long-standing, the left atrium is very enlarged, or symptoms are minimal, a rate-control strategy may serve you better. This judgement is exactly what specialist assessment is for.

Preparation: safety first

The key risk in cardioversion is dislodging a clot that may have formed in the heart during AF. Preparation is therefore built around stroke prevention:

• Anticoagulation: at least three to four weeks of uninterrupted blood-thinning treatment before the procedure, continued for at least four weeks afterwards, and long term where your stroke risk warrants it.
• Transoesophageal echocardiogram (TOE): where earlier treatment is preferred or anticoagulation has been imperfect, a TOE can directly confirm the heart is clear of clot immediately before cardioversion.
• Pre-assessment: an ECG, blood tests and an anaesthetic review, with clear fasting instructions.

What happens on the day?

Cardioversion takes place in a monitored day-case unit. You are asleep for only a few minutes; the shock itself takes seconds, and one to three synchronised impulses are delivered if needed. You wake without memory of the procedure, are monitored briefly, and are usually home within a few hours. You will need someone to accompany you and should not drive for forty-eight hours after the anaesthetic.

Success in restoring normal rhythm on the day is high, typically around ninety per cent for AF and higher for flutter.

Will the rhythm hold?

Cardioversion resets the rhythm; it does not, by itself, change the conditions that allowed AF to start. Depending on your circumstances we may recommend anti-arrhythmic medication around the procedure to improve durability, and, just as importantly, a targeted programme addressing the factors that drive AF recurrence: weight, sleep apnoea, alcohol, blood pressure and fitness. Where AF returns despite this, cardioversion has still done valuable diagnostic work, and ablation often becomes the logical next step, with your response to cardioversion helping predict its benefit.

Risks in perspective

Performed with proper anticoagulation, cardioversion is very safe. Risks are small and mostly minor: temporary skin redness under the pads, short-lived rhythm disturbance immediately after the shock, and the general risks of brief sedation. The serious risk, stroke, is precisely what the preparation protocol is designed to prevent, which is why the anticoagulation rules are non-negotiable.

Frequently asked questions

Does cardioversion hurt?

No. You are asleep for the shock itself and wake with no memory of it. Some people notice mild skin redness or chest-wall ache afterwards, similar to sunburn or a pulled muscle, which settles within a day or two with simple measures.

How quickly can I get back to normal?

Most people feel back to themselves the same evening, aside from the general advice that follows any sedation: no driving for forty-eight hours, no alcohol or important decisions for twenty-four, and a quiet first day. Many patients notice an immediate improvement in energy and breathing once normal rhythm is restored.

Can cardioversion be repeated?

Yes. There is no fixed limit, and a repeat cardioversion is sometimes entirely reasonable, for instance after an illness that triggered a relapse. That said, if AF keeps returning despite good preparation, repeating the same procedure indefinitely is rarely the best strategy, and we will talk honestly about ablation or a rate-control approach instead.

What are the chances the rhythm holds long term?

On the day, cardioversion restores normal rhythm in roughly nine out of ten patients. How long it holds depends on how long AF has been established, the size of the left atrium, and how thoroughly the drivers, weight, alcohol, sleep apnoea and blood pressure, are addressed. We will give you a realistic, personalised estimate rather than a generic figure.

Do I really need blood thinners if I feel fine?

Yes. Clot risk around cardioversion has nothing to do with how you feel, and the anticoagulation protocol is what makes the procedure safe. Stopping early, even for a few days, undoes that protection, so please never adjust these tablets without cardiology advice.

How soon after diagnosis can cardioversion be arranged?

Privately, very quickly. Once anticoagulation requirements are satisfied, or a TOE has confirmed the heart is clear of clot, cardioversion can usually be scheduled within days at one of our partner facilities, with your pre-assessment, procedure and follow-up coordinated seamlessly from Harley Street.

Why choose Dr Assomull?

Dr Assomull provides the complete pathway at 68 Harley Street: confirming the diagnosis and whether rhythm control is right for you, arranging anticoagulation and, where needed, same-week TOE-guided cardioversion in a specialist London facility, and then leading the long-term plan, medication, lifestyle and onward ablation referral where appropriate, so the normal rhythm you regain is one you keep.

If AF or flutter is disrupting your life, book a consultation, usually available within one working day.