Finding Could Lead to More Aggressive Treatment for Patients at Highest Risk
Feb 9, 2004
Diabetics who have certain abnormalities on an electrocardiogram (ECG) a measure of the heart's electrical activity are much more likely to die in a five-year period than their peers who have normal ECG results, NewYork-Presbyterian Hospital/Weill Cornell Medical Center physician-scientists report in the February issue of the journal Diabetes.
Electrocardiograms, which are performed by attaching electrodes to the chest, are one of the easiest and most common heart tests given to patients.
Because these are readily performed, the ECG can be used to identify diabetics who are at markedly increased risk of suffering either cardiovascular death or death due to any cause, said lead author Dr. Peter Okin, Professor of Medicine and Director of Clinical Affairs in the Division of Cardiology at Weill Cornell Medical College; and Attending Physician at NewYork-Presbyterian/Weill Cornell.
In general, people with diabetes are at much greater risk of developing cardiovascular disease, and are more likely to have a heart attack or stroke, than nondiabetics. Determining which diabetics are in a more precarious position may spur doctors to use more aggressive treatments, said Dr. Okin.
There's a rising tide of diabetes in the American population, largely due to obesity, and this is putting a whole new generation of Americans at increased risk for dying of cardiovascular disease and other causes. We as physicians have to care for more and more diabetic patients, and we need better tools to identify those at greater risk and those who need additional help, said Dr. Okin.
Additional study is needed to determine if interventions can make a difference for diabetic patients with ECG abnormalities, but it is certainly our suspicion that aggressive interventions such as treating high blood pressure, lowering cholesterol, and controlling blood sugar will make a difference, he said.
The findings are from the Strong Heart Study, an ongoing study of American Indians in 13 communities in Arizona, Oklahoma, and North and South Dakota. The researchers are studying Native Americans because they tend to have multiple risk factors linked to cardiovascular disease.
The Strong Heart Study focuses on American Indians because of a very, very high risk of developing or dying due to cardiovascular disease. There is a very high prevalence of diabetes, obesity, alcohol abuse, tobacco use, and elevated cholesterol, said Dr. Okin. This is a population with major medical problems.
The study included 994 American Indians with type 2 diabetes, the most common form of the disease, which is often associated with obesity. All the patients, who were mostly in their 50s or 60s, had a digital electrocardiogram, which allowed the researchers to use computerized measurements to quantify the degree of abnormality. The participants were followed for an average of nearly 5 years.
During that time, 56 people died due to cardiovascular disease, such as heart attack or stroke, and 155 died due to other causes.
The risk of dying due to cardiovascular disease was 3.68 times as high for patients with an ECG finding known as ST segment depression, and 2.61 times as likely for those with an elevated principal component analysis (PCA) ratio.
ST segment depression can be a sign of a number of things, including underlying coronary artery disease (clogged heart arteries) or an enlarged heart. People with an elevated PCA ratio are thought to be at greater risk of developing heart arrhythmias.
The researchers also found that the risk of dying of any cause was 2.36 times as high in those with ST segment depression, and 2.03 times as high in those with a prolonged heart-rate-adjusted QT interval greater than 460 milliseconds.
They speculate that a prolonged QT interval could also be a sign of other diabetes-related conditions, such as kidney failure or electrolyte and hormonal imbalances, which could increase the risk of dying of other causes. ST segment depression often occurs when the heart is enlarged, which is known to increase the risk of dying due to any cause.
It's not clear if the findings are applicable to all diabetics, but the chances are good that they hold true for people of other ethnicities.
Are the findings applicable to other populations? That's always an important question. I would say almost certainly yes because all of these findings the ST depression, the QT elongation, and the principal component analyses are associated with adverse outcomes in other populations, said Dr. Okin.
The results mirror those found in the entire Strong Heart Study population, which included people without diabetes. However, it's the first time anyone has looked at all of these factors, including ST segment depression and PCA ratio, in diabetics, Dr. Okin said.
And the study is unique in that it links a specific number, or quantitative result, to a higher risk of death. ECGs can sometimes be open to interpretation, Dr. Okin said.
The presence of non-specific ST segment and T-wave wave abnormalities have been associated with all cause and cardiovascular mortality in other studies, but that's a very qualitative description, said Dr. Okin. You and I may look at cardiograms and describe them very differently. What we are doing is very quantitative, and these computer-measured findings are very reproducible.
In addition to Dr. Okin, the study co-authors include NewYork-Presbyterian/Weill Cornell's Dr. Richard Devereux, Elisa Lee (University of Oklahoma Health Sciences Center), James Galloway (University of Arizona), and Barbara Howard (Medlantic Research Institute).
The study was funded by grants from the National Heart, Lung, and Blood Institute, and a grant from The Michael Wolk Heart Foundation.2453045pubjvb9001&&19:59-11- 4-2004kebloom16:15- 8-20-200402_09_04