Family history, age, high blood pressure, high cholesterol, smoking, obesity, and diabetes (just to name a few) are all conventional risk factors for heart disease. It’s commonly accepted that these conditions increase your risk of developing cardiovascular disease and stroke. While this is true, such risk factors do not account for all instances of heart disease or cardiac death. There are always some people who possess no apparent risk factors for heart disease and yet still suffer cardiac death.
Currently, conventional testing for cardiovascular disease doesn’t identify such at risk persons. Researchers at the Washington University School of Medicine in St. Louis, Missouri believe that they may have discovered a test that will identify people who are at risk for cardiac death even though they possess no conventional risk factors. According to researchers, they were able to identify at risk persons, who otherwise appeared to be healthy, by an anomaly (abnormal heart rate turbulence) in the response to left ventricle “early” or ventricular premature beat (VPB).
Ventricular premature beats are not an uncommon occurrence. A VPB occurs when the left ventricle misfires and beats earlier than it should. This results in two difficulties for persons with VPB. First, blood flow is decreased because the heart is unable to fill up with a sufficient amount of blood. As a result, heart rates increase as the heart tries to keep up with the demand. Second, VPBs cause the heart to empty much more quickly than normal. This results in a heart that is fuller than normal on the second beat because of the additional time to fill the heart. To compensate for the additional blood that is present, the heart slows down.
Heart rate turbulence is the heart’s response to VPBs. The normal response to VPB is to compensate by alternately speeding up and slowing down to compensate for the VPB. Heart rate turbulence can be tracked through the use of a Holter monitor, a device that is worn for 24 hours which records the heart’s electrical (electrocardiogram) signals.
During the course of this study, researchers tracked the heart rate turbulence of approximately 1,300 individuals. The study took place over a five year period from 1989 to 1993. All participants were over the age of 65 years. Participants were classified in three categories: clinical (history of heart attack or cardiovascular disease), subclinical (risk factors for heart disease present but under no treatment protocol for heart disease), and healthy individuals (those with no risk factors for heart disease).
The healthy group consisted of 357 individuals. Of those, approximately six percent (21 participants) were found to have abnormal heart turbulence. Researchers found that the rate of cardiac death in this group of health participants with abnormal heart turbulence was eight times higher than their counterparts in the same group. In addition, findings indicated that those in the healthy group with abnormal heart turbulence were at a greater risk in terms of survival than those in the subclinical group with normal heart turbulence.
The study did not address whether or not the presence of abnormal heart turbulence is equally predictive of cardiac death in individuals younger than 65 years.
While researchers believe that abnormal heart turbulence is an easy non-invasive predictor test, it’s not yet in common use. The software used to track the abnormal heart turbulence of participants is not yet commercially available to the public.
More information and complete findings were published in the February 15, 2011 edition of the Journal of Cardiovascular Electrophysiology.
Journal Reference:
1. Phyllis K. Stein, Joshua I. Barzilay. Relationship of Abnormal Heart Rate Turbulence and Elevated CRP to Cardiac Mortality in Low, Intermediate, and High-Risk Older Adults. Journal of Cardiovascular Electrophysiology, 2010; DOI: 10.1111/j.1540-8167.2010.01967.x
Source:
Washington University School of Medicine (2011, February 15). 'Healthy' patients at high risk of cardiac death identified. ScienceDaily. Retrieved February 20, 2011, from http://www.sciencedaily.com¬ /releases/2011/02/110215111811.htm