Abnormal heart rate turbulence could be associated with an increased risk of heart disease death in low-risk, older individuals, according to a study in the Feb. 15 issue of the Journal of Cardiovascular Electrophysiology. However, more studies replicating these data in other patient populations will be necessary to understand whether this potential biomarker will be a clinically valuable tool, Robin Boineau, MD, of the National Institutes of Health, told Cardiovascular Business News.
During the observational study, Phyllis K. Stein, PhD, and Joshua I. Barzilay, MD, of the Washington School of Medicine in St. Louis, and the Emory University School of Medicine in Atlanta, assessed 1,272 patients aged 65 or older via 24-hour heart monitoring via Holter monitors (GE Healthcare) to evaluate heart rate turbulence in healthy, subclinical (some signs of heart disease) or clinical (previous CV event) patients.
The researchers measured the magnitude of the initial heart rate jump (turbulence onset) and the speed at which heart rate returns to normal (turbulence slope), and then determined if the heart rate turbulence response is normal or abnormal.
The researchers reported that heart rate turbulence was a strong risk factor for heart disease, even stronger than heightened levels of C-reactive protein (CRP). Almost 7 percent of the patients within the study had abnormal heart rate turbulence, which predicted the increased likelihood of heart disease death.
Additionally, Stein and Barzilay found that patients at a low risk for heart disease were eight to nine times more likely to die of heart disease if they had abnormal heart rate turbulence values during the 14-year follow-up. The authors also noted that individuals at a low risk for heart disease who had elevated CRP were 2.5 times more likely to die than those with normal or low CRP.
Traditional risk factors include age, gender, high blood cholesterol, high blood pressure, obesity, diabetes and smoking are important. But both abnormal heart rate turbulence and CRP levels were independently correlated to an increased likelihood of dying of heart disease, particularly in the group of patients classified as healthy.
"If we find similar results in other patient populations then the next step will be to see if we can do something about it [abnormal heart rate turbulence]," said Boineau, a medical officer in the National Heart, Lung, and Blood Institute's (NHLBI) Division of Cardiovascular Sciences, who was not part of the study. If there is nothing one can do about abnormal heart rate turbulence, then patients would need to be checked and treated for traditional heart disease risk factors—diabetes, high lipid levels, high body mass indexes and high blood pressure.
"In the mean time we will see if we can find some therapies that could be used to blunt this abnormal response," she noted. "It would be more effective if there was some way we knew we could change the abnormal response."
If studies such as this are replicated, Boineau said that testing for abnormal heart turbulence should be done as an add-on to testing for CRP levels.
"This study shows a great potential value for heart rate turbulence in diagnostic settings," Boineau concluded. "It appears that signs of heart rate turbulence also are generally present a year or more before clinical manifestations of heart disease, indicating that this may be an opportunity for disease prevention in addition to disease prediction."
The study was funded by the NHLBI.