Sudden Cardiac Death And Circadian Rhythms Link On A Molecular Basis
In a study due to be published in the March issue of the journal Nature, scientists report the discovery of a molecular basis of the link between circadian rhythms and sudden cardiac death.
Sudden cardiac death is a natural , rapid and unexpected death that occurs within one hour after the onset of cardiac acute symptoms. Sudden cardiac death is the leading cause of death in the United States of America, accounting for 700-800 deaths each day. The most common cause of SCD is ventricular arrhythmia, an abnormal heart rhythm. Ventricular arrhythmias occur mainly in the morning, probably because the peak of stress hormones occurs in this part of the day. However, this fact could not be clearly explained until now.
Sudden cardiac death is the direct consequence of cardiac arrest, which can be reversed if medical staff acts promptly before the final shutdown of the brain function (cerebral death) and other functions (biological death). SCD may occur in apparently healthy persons, or may occur in patients suffering from cardiomyopathy. The only practical method of preventing SCD is to control the coronary risk factors: hypertension, ventricular hypertrophy, high cholesterol and obesity among others.
The results of this study lay the foundation for new methods of prevention and treatment of this fatal event. According to a study conducted by researchers at Case Western Reserve University School of Medicine, the genetic factor Kruppel-like Factor 15 (KLF15) correlates body’s circadian rhythm with the heart’s electrical activity. Both lack and excess of KLF15 increases the risk of arrhythmias. It has been noted that patients with heart failure present a lack of KLF15. Also it has been discovered that patients with Brugada syndrome, a genetic cardiac arrhythmia, present an excess of KLF15.
The discovery KLF15 does not only explain the molecular basis of ventricular arrythmya and sudden cardiac death, but can also be the basis for developing new strategies in oreder to prevent SCD. For example, by increasing KLF15 in patients with heart failure, especially in the morning, when the risk of SCD is increased, the number of sudden cardiac events could be reduced.
Dr. Darwin Jeyaraj, MD, MRCP, assistant professor of medicine at Case Western Reserve University School of Medicine, points out that this is only the mere beggining of a series of research intended to cast light on the link between circadian rhythms and sudden cardiac death.
Mukesh K. Jain, MD, Faha, professor of medicine, noted the importance of this remarkable finding: “This is the first time a definitive link between circadian rhythms and sudden cardiac death has been established”. He also added that further studies are needed so as to evaluate the link between heart disease and circadian rhythm disruption.