Antibiotics do not prevent heart attacks

Clinicians and researchers have found that more than three quarters of heart attack patients have been infected with chlamydia pneumoniae - a bacteria found in arteries of heart attack patients - and multiple studies have found this can double the risk of developing subsequent heart attacks.

Researchers hoped, and initial studies suggested, that an antibiotic regimen to treat the chlamydia pneumoniae could reduce the risk of coronary events. Researchers from the TIMI Study Group at Brigham and Women’s Hospital (BWH), in a large, international clinical trial, found that despite long-term treatment with gatifloxacin - an antibiotic often prescribed to successfully treat chlamydia pneumoniae - patients did not experience a reduction in recurrent cardiac events. The findings are published in the April 21, 2005 issue of New England Journal of Medicine.

According to study principal investigator Christopher P. Cannon, MD of BWH and associate professor of Medicine at Harvard Medical School (HMS), “Although chlamydia pneumoniae may have played a role in starting the process of atheroscelosis, once patients have documented heart disease, it appears to be too late to treat the infection. Instead, we need to focus on reducing the cholesterol build-up and inflammation in the arteries, using high-dose statins - as shown in this same study - and other treatments.”

Dr. Cannon noted that while there are many identifiable risk factors for arteriosclerosis, many patients do not exhibit these risk factors. This has prompted ongoing research to find additional markers that will help clinicians identify and then stop progression of cardiovascular disease. Specifically, chlamydia pneumoniae - one of these new, non-traditional risk factors - has been associated with the development of arteriosclerosis and heart attacks. To determine if treating this risk factor reduces coronary events, researchers in the Pravastatin or Atorvastatin Evaluation and Infection Therapy - Thrombolysis in Myocardial Infarction (PROVE IT - TIMI) 22 looked at the long-term treatment of chlamydia pneumoniae with gatifloxacin, an antibiotic or placebo.

Between November 2000 and December 2001, 4,162 patients who had been hospitalized for an acute coronary syndrome were randomized at sites worldwide. The average age of patients was 58 years and 22 percent were women. Patients in the PROVE IT - TIMI 22 trial received standard medical and interventional treatment for the coronary event, including 75 to 325 mg aspirin daily. In addition, to understand how treating C. pneumoniae would impact recurrent coronary events, patients were further randomized to receive 400 mg of gatifloxacin daily or placebo for 10-day treatments each month for an average of two years. The primary end point included death from all causes, myocardial infarction, documented unstable angina that required rehospitalization and/or revascularization with either percutaneous coronary intervention or coronary artery bypass surgery or stroke. Despite being treated with a bactericidal antibiotic, there was no reduction in the rate of cardiovascular events. No subgroups of patients were seen to benefit from the treatment, even using C-reactive protein or antibody titres. Researchers concluded that while there is evidence to suggest C. pneumoniae has a role in the development of heart disease, long-term antibiotic therapy clearly does not benefit a patient who had been recently hospitalized for a coronary event.

According to senior author, BWH’s Eugene Braunwald, MD, HMS Distinguished Hersey Professor of Medicine and chairman of the TIMI Group, “Clinicians need to actively evaluate and use proven therapies for secondary prevention of heart attack including high-dose statin therapy, beta blockers and antiplatelet therapy. However, we will also continue to search for additional therapies to prevent heart attacks.”