Sudden Cardiac Death And Circadian Rhythms Link On A Molecular Basis
In a studyÂ due toÂ be published in the March issue of the journal Nature, scientists report the discovery of a molecular basis of the linkÂ between circadian rhythms and sudden cardiac death.
Sudden cardiac death is a natural , rapid and unexpected deathÂ that occurs within one hour after the onset of cardiacÂ acute symptoms. Sudden cardiac death is the leading cause of death in the United States of America,Â accounting forÂ 700-800 deathsÂ each day. The most common cause ofÂ SCD is ventricular arrhythmia, an abnormal heart rhythm. Ventricular arrhythmias occur mainly in the morning, probably because the peak of stress hormonesÂ occurs in this part of the day. However, this factÂ could not be clearly explained until now.
Sudden cardiac death is the direct consequence of cardiac arrest, which can be reversed if medical staff actsÂ promptly before the final shutdown ofÂ the brain function (cerebral death) and other functions (biological death). SCDÂ may occur inÂ apparently healthy persons, or may occur inÂ patients suffering from cardiomyopathy. The only practical method of preventing SCD isÂ to controlÂ the coronary risk factors: hypertension, ventricular hypertrophy, high cholesterol andÂ obesity among others.
The results of this studyÂ lay the foundation for new methods of prevention and treatment of this fatal event. According to a studyÂ conductedÂ by researchers at Case Western Reserve University School of Medicine,Â the genetic factor Kruppel-likeÂ Factor 15 (KLF15) correlates body’s circadian rhythm with the heart’s electrical activity. Both lack and excess of KLF15Â increases the risk of arrhythmias.Â It has beenÂ noted that patients with heart failureÂ present a lack ofÂ KLF15. Also it has been discovered that patients with BrugadaÂ syndrome, a genetic cardiac arrhythmia, presentÂ an excess of KLF15.
The discovery KLF15Â does not only explain the molecular basis of ventricular arrythmyaÂ and sudden cardiac death, but can alsoÂ be the basis for developingÂ new strategiesÂ in orederÂ to prevent SCD. For example, by increasing KLF15Â in patients with heart failure, especially in the morning, when the risk of SCD is increased,Â the number of sudden cardiac events could beÂ reduced.
Dr.Â Darwin Jeyaraj, MD, MRCP, assistant professor of medicine at Case Western Reserve University School of Medicine, points out that thisÂ is only the mere begginingÂ of a series of research intended to cast light on the link between circadian rhythms and sudden cardiac death.
MukeshÂ K. Jain, MD, Faha, professor of medicine, noted the importance of this remarkableÂ finding: “This is the first time a definitive link between circadian rhythms and sudden cardiac deathÂ has been established”. He also added that further studies are neededÂ so as toÂ evaluate the link between heart disease and circadian rhythm disruption.