Studies Propose That Depression Increases Risk of Dying for Heart Failure Patients
ANAHEIM, CA. -- The link between depression and the development of heart disease is growing stronger, Duke University Medical Center cardiologists say.
At the annual meeting of the American College of Cardiology, investigators reported study findings that, first, document the extent of depression in heart patients and, next, propose a mechanism by which that depression harms the heart.
Duke researchers found that the risk of dying was more than twice as high in a group of congestive heart failure patients who were depressed, compared to those patients who weren't.
"Some physicians have traditionally assumed that heart patients become depressed because they are unhappy about being sick, and that this was benign," said cardiologist Dr. Christopher O'Connor, the lead investigator. "However, this study shows us that major depression in patients hospitalized for congestive heart failure independently predicts a poor prognosis."
The study, funded by the Duke Clinical Research Institute, found that 35 percent of 374 heart failure patients admitted to Duke between March 1997 and June 1998 were diagnosed with depression, based on a standard battery of psychological tests. Furthermore, 14 percent of this group of patients were classified as having major depression.
The extent and degree of depression in those patients is much higher than would have been expected if patients were just reacting to the fact that they were sick, O'Connor said in an interview. "This is a higher than normal prevalence, even for heart disease patients," he said. "But it was not detected before we tested for it."
The overall death rate in the depressed group was 11.9 percent at three months versus 5.6 percent in the non-depressed group. Morbidity - the occurrence of cardiovascular complications - was also increased in depressed patients.
There are many theories about the biological mechanism between depression and the worsening of heart disease, O'Connor said. One relates to the finding that heart rate variability in depressed congestive heart failure patients is diminished. "It does not vary as it should, thus increasing the risk of sudden death," O'Connor said.
Also, researchers have found that "depressed patients have stickier platelets," he said. That is, their blood platelets have a heightened reactivity and are more likely to clot together, setting up conditions that favor a heart attack. "We aren't yet sure why this happens," he said. "It could be an alteration in hormonal balance, or a number of other possibilities."
O'Connor said researchers are now conducting a study to see if anti-depressants help heart patients. Results of a worldwide trial he is leading will be presented later this year.
In another study prepared for presentation at the meeting, O'Connor and two researchers from the Sinai Center for Thrombosis Research in Baltimore, Dr. Victor Serebruany and Dr. Paul Gurbel, tested the blood that patients had voluntarily donated.
They mixed the blood with the active ingredients in the anti-depressant sertraline (tradename Zoloft), a selective serotonin reuptake inhibitor, and its neurologically inactive metabolite N-desmethylsertraline, and found that - to their "great surprise" - sertraline helped prevent platelets from sticking together. That is, they work to prevent clots from forming in the blood; clots that could produce a heart attack or stroke.
"The antiplatelet properties of sertraline is on an order similar in strength to super aspirin." Dr. Serebruany said in an interview. "Here we have a drug that treats depression, is extremely safe, and has anti-platelet effects no one has ever looked at before," he says.
Sertraline works by restoring levels of the neurotransmitter serotonin, thereby relieving the symptoms of depression. An association between low levels of serotonin and heart disease has been made, and this study suggests that this particular selective serotonin reuptake inhibitor itself may help control blood clotting, O'Connor says.