Sick sinus syndrome can be associated with sudden cardiac death.  The pioneering research could potentially help improve thousands of lives through preventative treatment of those most at risk from sick sinus syndrome, in which the activity of the heart’s pacemaker this sinoatrial node, is impaired. 

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. It is estimated that about 30% of sudden cardiac deaths occur at nighttime, claiming the lives of often young and fit people, including well-trained athletes.

Professor Henggui Zhang and colleagues at The University of Manchester, working with Professor Jules Hancox from the University of Bristol’s Physiology & Pharmacology Department, has for the first time shown how gene mutation and activity of the nervous system can combine to seriously disrupt the heart’s normal rhythm.

The form of sick sinus syndrome investigated is not connected with structural heart disease, but with genetic mutations that alter a protein called SCN5A that is involved in generation of electrical activity in the heart.

The research is based on 13 years worth of work developing models of cardiac electrical activity, and has now been published in the leading journal Circulation Research.

Using experimental measurements from the sinoatrial node together with detailed computer models, researchers were able to simulate the electrical activity in cardiac tissue.

They found that there is a chemical present in the nervous system which in healthy individuals acts to slow the heart rate, but in sick sinus syndrome patients may prevent electrical activity spreading across the heart, thereby compromising cardiac function. 

These effects are associated with gene mutations which can be detected by tests, and which could help to identify those most at risk as well as informing treatments such as drugs or pacemaker devices.

Professor Hancox said: “The insights into sick sinus syndrome from this study are potentially of great importance.  If other forms of sick sinus syndrome that involve mutations to different proteins in the heart are affected by nerve activity in the same way, this may identify a common target to reduce or eliminate risk of dangerous arrhythmia.”