New Hope for Treating Heart Rhythm Irregularity That Often Follows Surgery

Heart

Atrial fibrillation, one of the most common and least manageable postoperative complications of heart surgery, may soon have an effective treatment.

In laboratory tests in dogs, cardiac researchers at Washington University School of Medicine in St. Louis have found that treatment with anti-inflammatory drugs after heart surgery may lessen or prevent atrial fibrillation. They report their findings in the June 7 issue of Circulation.

Atrial fibrillation, a rapid, irregular twitching of the upper chambers of the heart, occurs in a quarter to a half of patients who undergo heart surgeries such as coronary bypass or valve replacement. The condition can lead to serious post-operative complications, including congestive heart failure or stroke.

"Patients have suffered postoperative atrial fibrillation since the early days of cardiac surgery, and while beta-blockers, drugs used to prevent abnormal heart rhythms, seem to reduce the incidence, there has been no cure," says senior author Ralph Damiano Jr., M.D., the John Schoenberg Professor of Surgery and a cardiovascular specialist at Barnes-Jewish Hospital. "Our research suggests inflammation is the cause of postoperative atrial fibrillation, and this gives us new options for preventative therapy."

The researchers' investigated the effects of heart surgery in dogs. They found that the severity of atrial fibrillation corresponded to the amount of inflammation in surgically treated heart tissue. Inflammation led to changes in the electrical properties of the atria.

The inflammatory response consists of alterations in blood flow, increased permeability of blood vessels and escape of cells from the blood into the tissues. It is a normal response of tissue to injury that speeds the healing process in most instances.

"We found that inflammation led to non-uniform conduction of electrical impulses in the atria," Damiano says. "There were areas of very slow conduction and areas of normal conduction. The result was chaotic contractions of the atria."

Anti-inflammatory therapy increased the uniformity of the conduction of electrical impulses and decreased the incidence of atrial fibrillation.

Next, the researchers will continue their studies in dogs and attempt to block inflammation of the heart tissue while preserving the normal inflammatory response in the rest of the body.

"Our hope is that we can soon bring this treatment to the operating room and eliminate one of the major complications of heart surgery," Damiano says.

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Ishii Y, Schuessler RB, Gaynor SL, Yamada K, Fu AS, Boineau JP, Damiano Jr. RJ. Inflammation of atrium after cardiac surgery is associated with inhomogeneity of atrial conduction and atrial fibrillation. Circulation 2005 June;111(22):2881-2888.

Funding from the National Institutes of Health supported this research.

Washington University School of Medicine's full-time and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children's hospitals. The School of Medicine is one of the leading medical research, teaching and patient care institutions in the nation, currently ranked third in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children's hospitals, the School of Medicine is linked to BJC HealthCare. - June 7, 2005