Pneumonia is the most common serious infection after heart surgery, medical researchers from the University of Pennsylvania have found.

Most infections occur about two weeks after surgery, not one week as previously thought, researchers said at the American Heart Association Scientific Sessions 2011.

"In the past, focus has been on sternal wound infections after heart surgery, rather than other prevalent infections such as pneumonia," said lead researcher Michael A. Acker, M.D. He is also chief of Cardiovascular Surgery at Penn.

Researchers analyzed cardiac surgery results of more than 5,100 patients in the heart surgery registry Cardiothoracic Surgical Trials Network (CTSN). They found that median time to major infection was 14 days after heart surgeries, and 42 percent of all major infections occurred after hospital discharge.

Pneumonia infection of the lungs occurred in 2.4 percent of all patients.

Risk factors for developing an infection include: congestive heart failure, chronic lung disease, hypertension, corticosteroid use prior to surgery.

"This new research should help guide more effective management strategies to reduce overall occurrence of all infections,” Acker said.