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Scientists at The University of Manchester have solved a mystery connected with why people die from sudden cardiac arrest during sleep — potentially saving thousands of lives.

The pioneering research, using detailed computer models, could help save lives through preventative treatment of those most at risk from a form of heart rhythm disorder called sick sinus syndrome.

This occurs when the activity of the heart’s pacemaker, the sinoatrial node, is impaired. Up to now, no-one has been able to work out why this happens.

But groundbreaking research by Professor Henggui Zhang at The University of Manchester shows how gene mutation and activity of the nervous system can combine to seriously disrupt the heart’s normal rhythm.

This research means it would be possible to identify those most at risk of suffering sudden cardiac death, which can affect people of any age but particularly the healthy elderly and well-trained athletes.

It could then be possible to control the risk by using drugs or a pacemaker.

Sudden cardiac death occurs after an abrupt loss of consciousness within one hour of the onset of acute symptoms. This often happens during the night as heart rate slows dramatically at night times.

Sick sinus syndrome is a relatively uncommon syndrome. It can result in many abnormal heart rhythms (arrhythmias), including sinus arrest, sinus node exit block, sinus bradycardia, and other types of bradycardia (slow heart rate).

Sick sinus syndrome may also be associated with tachycardias (fast heart rate) such as paroxysmal supraventricular tachycardia (PSVT) and atrial fibrillation. Tachycardias that occur with sick sinus syndrome are characterized by a long pause after the tachycardia.

Abnormal rhythms are often caused or worsened by medications such as digitalis, calcium channel blockers, beta-blockers, sympatholytic medications, and anti-arrhythmics. Disorders that cause scarring, degeneration, or damage to the conduction system can cause sick sinus syndrome, including sarcoidosis, amyloidosis, Chagas’ disease, and cardiomyopathies.

Sick sinus syndrome is more common in elderly adults, where the cause is often a non-specific, scar-like degeneration of the cardiac conduction system. Cardiac surgery, especially to the atria, is a common cause of sick sinus syndrome in children.

Sick sinus syndrome, also called sinus node dysfunction, is a group of abnormal heart rhythms (arrhythmias) presumably caused by a malfunction of the sinus node, the heart’s primary pacemaker.Bradycardia-tachycardia syndrome is a variant of sick sinus syndrome in which slow arrhythmias and fast arrhythmias alternate.

Sick sinus syndrome is a relatively uncommon syndrome. It can result in many abnormal heart rhythms (arrhythmias), including sinus arrest, sinus node exit block, sinus bradycardia, and other types of bradycardia (slow heart rate).

Sick sinus syndrome may also be associated with tachycardias (fast heart rate) such as paroxysmal supraventricular tachycardia (PSVT) and atrial fibrillation. Tachycardias that occur with sick sinus syndrome are characterized by a long pause after the tachycardia.

Abnormal rhythms are often caused or worsened by medications such as digitalis, calcium channel blockers, beta-blockers, sympatholytic medications, and anti-arrhythmics. Disorders that cause scarring, degeneration, or damage to the conduction system can cause sick sinus syndrome, including sarcoidosis, amyloidosis, Chagas’ disease, and cardiomyopathies.

Sick sinus syndrome is more common in elderly adults, where the cause is often a non-specific, scar-like degeneration of the cardiac conduction system. Cardiac surgery, especially to the atria, is a common cause of sick sinus syndrome in children.

Sick sinus syndrome

Coronary artery disease, high blood pressure, and aortic and mitral valve diseases may be associated with sick sinus syndrome, although this association may only be incidental. The mechanism is related to delayed escape. Congenital SSS is due to mutations of gene responsible for formation of Alpha subunit of sodium channel.

Even though many types of sick sinus syndrome produce no symptoms, patients may present with:

* Stokes-Adams attacks – fainting due to asystole or ventricular fibrillation
* Dizziness or light-headedness
* Palpitations
* Chest pain or angina
* Shortness of breath
* Fatigue
* Headache
* Nausea
* Fainting