"Healthy people" do not expect to die from sudden cardiac death.
The commonly known risk factors, such as high blood pressure, elevated cholesterol, diabetes, and smoking, account for most of the cardiac related deaths but not 100% of them.
What They Discovered
According to the new research from the Washington University School of Medicine, indicates that an abnormal response to an early beat in the left ventricle, the heart's main pumping chamber, can identify high-risk patients even when they have no other signs or known risk factors of cardiovascular disease.
A ventricular premature beat (VPB) is an extra heartbeat resulting from abnormal electrical activation originating in the ventricles before a normal heartbeat occurs. VPBs are very common even in healthy people. The difference is how the heart reacts to them. The heart's response to a VPB is called heart rate turbulence and it can be measured by a Holter monitor device that is typically worn for a 24 hr period and records the heart rhythm or electrical signals.
When the ventricle beats early, the heart has not finished filling and it pumps less blood to the body than it should. To compensate, the heart rate speeds up to increase blood flow.
But an early beat causes the heart to empty too soon, leaving extra filling time afterward. So on the second beat after the VPB, the heart is extra full and pumps more blood to the body than it should. To compensate properly for this situation, the heart rate slows down.
A healthy heart will compensate for the over and under-filling that follows a VPB, by speeding up and slowing down until the amount of blood filling the heart returns to normal.
Clinical Study
Phyllis K. Stein, PhD, research associate professor of medicine and director of the Heart Rate Variability Laboratory at the School of Medicine her and colleagues analyzed Holter monitor recordings for almost 1,300 patients over age 65 recorded between 1989 and 1993.
The patients were divided into three groups based on an assessment of their cardiovascular health. Those in the "clinical" group had a history of cardiovascular disease such as heart attack or surgery to open narrow blood vessels. Those in the "subclinical" group had traditional risk factors for cardiovascular disease such as high blood pressure or diabetes but had never been treated for cardiovascular disease. And those in the "healthy" group had no evidence of clinical or subclinical disease.
In all three groups, abnormal heart rate turbulence was predictive of cardiac death. But the association was especially strong in the healthy group. Of the 357 patients classified as healthy, 21 had abnormal heart rate turbulence. These 21 people were almost eight times more likely to die of cardiac causes than the rest of the healthy group.
They also looked at what is called C-reactive protein, which is an inflammatory marker which can indicate a higher risk for cardiac disease. They determined that the heart turbulence was a better indicator of sudden cardiac death in the "healthy" group.
Even though the Holter Monitor device is readily available for use, only one particular brand has the special updated software to pick up the heart turbulence in the clinical setting. Stein is hoping that this study will help make the updated software more widely available.
Source:
- Washington University School of Medicine. Phyllis K. Stein, Joshua I. Barzilay, (2011, February 15). 'Healthy' patients at high risk of cardiac death identified. February 16, 2011.
Raechelle Janzen - Life is not just about how you weathered the storms.....its about how you danced in the rain.
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