New role for antibiotics in cardiac care?

Although the nature of the relationship is unclear, some evidence indicates the drugs could be useful in preventing heart attacks.

By Victoria Stagg Elliott, amednews staff. April 1, 2002.

Treating people who already have heart trouble with antibiotics may improve cardiac function and reduce the rate of future heart attacks, according to two studies published in the February and March issues of Circulation, the Journal of the American Heart Assn.

The first, published in February by British researchers, found that in angina patients who tested positive for Chlamydia pneumoniae, vascular function improved after five weeks of azithromycin treatment.

Taking antibiotics to heart
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The second study, conducted in Finland and released in March, found that treating people already hospitalized for heart trouble with a three-month regimen of clarithromycin reduced the risk for future heart attacks.

Like an increasing number of medical conditions, heart disease has long been believed to have an infectious component. These two studies are the latest to point in that direction.

"This is an idea whose time has come," said Anderson Morris, MD, medical director of the HealthSouth Heart College and a cardiologist with Cardiovascular Associates in Birmingham, Ala. "Cholesterol is not the total answer, and now we're finding that there are other things going on in the arteries that can cause heart attacks."

Few believe, however, that bacteria or viruses are directly at fault. Currently, the most popular theory is that infection causes inflammation which destabilizes arterial plaques causing cardiac events. But this notion is still unproven. In addition, it's not entirely clear what the role of Chlamydia is, although it is the most common infectious agent found in heart patients' cardiac plaques.

A cautious approach

Cardiologists said the studies were intriguing, but that it was far too early to start adding antibiotics to the statins, ACE inhibitors, and smoking cessation, diet and exercise recommendations that are all the current staples of secondary prevention.

"I don't think any cardiologist wants to recommend doing [this] until more definitive proof is available," said Harischandra Karunaratne, MD, director of the coronary care unit at Florida Hospital in Orlando.

Instead, conventional wisdom is to wait for the results of several large-scale studies sponsored by drug companies and the National Institutes of Health. These efforts are due to be completed within the next few years.

"We're not at a point yet where we want to start testing all our patients and treating them with antibiotics, but this could be something we do in the future," said Robert Bonow, MD, president-elect of the heart association and chief of cardiology at Northwestern University Medical Center in Chicago. "What we all want is some large clinical trials that show there's a benefit in less heart attacks and better outcomes."

There are also many questions left to be answered. It is unclear whether the antibiotics work by eradicating the infection or through their anti-inflammatory properties. Chlamydia, the most common focus of these studies, may not be the only culprit, and an antibiotic will not be useful if the infectious agent is a virus.

Testing to determine the presence and nature of an infection in the cardiac system is also not currently available to the average clinician. But if it becomes so, there could be unintended consequences -- namely, exacerbating the already growing problem of antibiotic resistance.

Homocysteine, the latest heart care target, can be lowered through the use of B-vitamins. Although evidence of its impact on mortality is limited, treatment is cheap and has few adverse effects. Thus, cardiologists want far more evidence to support them adding antibiotics to their regimens.

"An antibiotic you don't want to just throw out into society because of the chance of resistance of other bacteria," said Dr. Morris.

ADDITIONAL INFORMATION:

Taking antibiotics to heart

Objective: To explore whether azithromycin improves endothelial function in patients with coronary artery disease who test positive for antibodies to Chlamydia pneumoniae.
Participants: 40 male patients with heart disease and antibodies to Chlamydia pneumoniae.
Method: In a randomized, prospective, double-blind, placebo-controlled trial, patients received either the antibiotic or a placebo for five weeks and were assessed for flow in the brachial artery, von Willebrand factor and C-reactive protein.
Results: Improved function was noted in those who received the antibiotic.
Conclusions: Treatment with azithromycin had a favorable effect on heart function. Further investigation needed into whether it decreases cardiac events.

Source: Circulation, February

Weblink

Abstract, "Effect of Azithromycin Treatment on Endothelial Function in Patients With Coronary Artery Disease and Evidence of Chlamydia pneumoniae Infection," Circulation, February (http://circ.ahajournals.org/cgi/content/abstract/hc1102.105649v1)

Abstract, "Effect of 3 Months of Antimicrobial Treatment With Clarithromycin in Acute Non-Q-Wave Coronary Syndrome," Circulation, March (http://circ.ahajournals.org/cgi/content/abstract/
01.CIR.0000012544.07696.1F)