Sudden arrhythmic death syndrome (SADS)

We can provide comprehensive diagnosis and treatment of the underlying conditions that cause SADS. We are:

• Able to confirm your appointment with a specialist within 24 hours
• Ranked no.1 in the UK for private cardiac care, treating more than 25,000 people each year
• Trusted, with 99% of cardiac patients happy to recommend us to friends and family

What is sudden arrhythmic death syndrome?

Sudden arrhythmic death syndrome is when someone passes away from a sudden cardiac arrest and there is no obvious sign of the cause. You may also see SADS referred to as sudden adult death syndrome, with the acronym still applicable.

A cardiac arrest is where the heart stops pumping blood around the body, cutting off breathing and the supply of oxygen to the brain. SADS can affect young, seemingly otherwise healthy people. For example, there have been a number of high-profile incidents involving professional athletes in recent years. One of those affected Denmark footballer Christian Eriksen, who suffered a sudden cardiac arrest on the pitch during a game against Finland in June 2021.

Eriksen received cardiopulmonary resuscitation (CPR) from medical staff, who then used an automated external defibrillator (AED) to shock his heart back into rhythm and save his life. As part of his recovery, Eriksen was fitted with an implantable cardioverter defibrillator (ICD) and made his return to the game in February 2022, eight months on from suffering the cardiac arrest.

Many heart conditions are linked to what's known as cardiac arrhythmia. This is a term to describe any disturbance of the normal electrical activity of your heart. These disturbances can lead to an unusually fast or slow heartbeat or an irregular rhythm. 

If undiagnosed or not treated, these can lead to cardiac arrests, which are sometimes fatal. In cases where the cause of the cardiac arrest cannot be found because the heart otherwise appears healthy, sudden arrhythmic death syndrome may be diagnosed. This is different to sudden cardiac death, which is when the cause can be pinpointed.

What causes sudden arrhythmic death syndrome?

In many cases, the underlying cause of sudden arrhythmic death syndrome is hereditary, meaning it is a condition that has been inherited from a parent. The typical cause of SADS is that an arrhythmia goes undiagnosed or untreated and leads to a cardiac arrest. If that proves fatal, it can be difficult to pinpoint the exact cause because the heart will appear to be otherwise healthy when it is examined.

There are a few different conditions that can cause an arrhythmia that leads to SADS. These include:

• Long QT syndrome: A condition that makes your heart's electrical system spend too long recharging ahead of its next beat, causing an irregular rhythm.
• Brugada syndrome: This is where the electrical messages that control your heart rate are affected, causing the two lower chambers (called ventricles) to beat abnormally fast.
• Catecholaminergic polymorphic ventricular tachycardia: CPVT is where your heart is beating at 120 beats per minute (BPM) and is doing so from the ventricles. Normally, the two upper chambers (the atria) beat first and for comparison, a typical resting heart rate is between 60-100 bpm.
• Short QT syndrome: The opposite of long QT syndrome, where your heart doesn't spend enough time recharging before the next beat.
• Timothy syndrome: A rare condition with heart irregularities that are similar to long QT syndrome. It can also affect the brain, the immune system and physical appearance.
• Wolff-Parkinson-White syndrome: This condition is present from birth, but in the majority of patients is not a genetic condition. It affects roughly one in 1,000 people. It causes your heart to beat abnormally fast because the electrical signals controlling the beat use an extra route on top of the usual one.

How common is sudden arrhythmic death syndrome?

• According to the British Heart Foundation (BHF), SADS is recorded for roughly one in 25 cases of sudden cardiac death. This proportion – around 4% – represents those cases where the cause of the cardiac arrest cannot be found.
• The BHF also states that sudden arrhythmic death syndrome affects around 500 people in the UK every year.

How can the conditions that cause SADS be diagnosed?

There are several tests we can carry out to help us understand if you have a heart condition that could put you at risk of sudden arrhythmic death syndrome. Your cardiologist may recommend one or more of these based on an initial physical examination as well as your symptoms and your medical history.

• An electrocardiogram (ECG), where sensors are attached to your chest while you lie on a bed. The ECG then records the electrical signals that control your heartbeat. At HCA we carry out around 25,000 ECGs every year.
• Genetic testing, usually in the form of a simple blood test, to see if you have any genetic defects that have been passed on to you by a family member.
• An echocardiogram, an ultrasound scan that checks to see if your heart and valves are working as they should be. We do more than 20,000 of these each year.
• A cardiac stress test, which is designed to figure out how your heart responds to being put under the strain of exercise. During this test, you'll walk on a treadmill set at a controlled speed and incline while your heart rate and blood pressure are measured.
• Electrophysiology studies that map your heart's electrical activity to try and find the source of arrhythmia.

We can provide results within 48 hours and may repeat these tests to see how your arrhythmia responds to treatment. 

These tests may still be available to you if you are not experiencing symptoms.

How can the conditions that cause SADS be treated?

There are several different treatments for the underlying conditions that can cause sudden adult death syndrome. The most suitable option for you will depend on your condition, the type of arrhythmia and any other underlying causes. It may be that your condition can be safely monitored with regular check-ups, but common treatments may include medication, therapies, devices and surgeries.

Medication

• Beta blockers (propranolol, bisoprolol or atenolol) to lower blood pressure and control your heart rate. Flecainide can sometimes be used if beta blockers are not helping
• Blood thinners, such as warfarin, which help to prevent blood clots
• Medicines for associated conditions that may cause arrhythmia

Therapies

• Electrical cardioversion, which gives your heart a safe electric shock to try and reset its rhythm. This is done by attaching patches or paddles to your chest.
• Vagal manoeuvres, which are techniques such as placing an ice pack or cold cloth on your face to help slow your heart rate.

Devices

• A pacemaker, a small device placed inside your chest to manage the speed of your heartbeat. In the last three years, we've fitted almost 900 of these.
• An ICD. Slightly larger than a pacemaker, it emits a small electric shock to restore your heart to a normal rhythm. 

Surgeries

• Cardiac denervation, an operation on the left-hand side of your neck to unblock or remove nerves.
• Catheter ablation, a minimally invasive treatment where one or more tubes are inserted into your heart's blood vessels to correct its abnormal rhythm.

In the last three years, our expert surgeons have performed over 3,000 ablations and more than 2,000 cardiac surgeries.

Potential side effects of treatments

As with most medications and surgeries, there are some potential side effects associated with having treatment for the conditions that can cause sudden adult death syndrome. These include:

• Lethargy, which can be brought on by taking beta blockers
• Stomach upsets, sometimes associated with taking flecainide
• Infection from surgical procedures, including having a pacemaker or ICD fitted
• Problems with the ICD or pacemaker working properly
• Abnormal sweating or inconsistent temperatures in the face, which can happen after a cardiac denervation

How can you lower the risk of SADS?

Some arrhythmias that lead to sudden adult death syndrome can't always be prevented. But there are steps you can take to help reduce your risk. These include:

• Eating a diet low in salt and saturated fat to protect your heart
• Exercising regularly
• Giving up or limiting smoking
• Limiting your intake of alcohol
• Sleeping well
• Managing your stress levels
• Maintaining a healthy bodyweight

When you meet with your consultant, they'll be able to recommend all the relevant lifestyle choices you can make and explain how they can help your condition.