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Even relatively "sterile" procedures are associated with a subsequent risk of infective endocarditis, researchers found.

In a nationwide case-crossover study from Sweden, inpatient procedures significantly more common in the 12 weeks prior to a hospital admission for endocarditis than in a control period from 365 to 449 days preceding admission included:

• Coronary artery bypass grafting (RR 13.80, 69 versus five cases)
• Percutaneous transluminal coronary angioplasty (RR 3.50, 21 versus six cases)
• Coronary angiography (RR 4.23, 148 versus 35 cases)
• Transfusion (RR 6.69, 174 versus 26 cases)
• Chronic dialysis (RR 3.64, 51 versus 14 cases)
• Bone marrow puncture (RR 4.67, 14 versus three cases)
• Bronchoscopy (RR 16.00, 16 versus one case)

"Apart from a potential reconsideration of antibiotic prophylaxis before certain particularly high-risk procedures, our findings also suggest that further improvement of aseptic measures before and during invasive procedures to minimize the excess risk for infective endocarditis is of crucial importance," suggested Imre Janszky, MD, PhD, of the Norwegian University of Science and Technology in Trondheim, and colleagues in the June 19 issue of the .

An by Martin Thornhill, MBBS, BDS, PhD, of England's University of Sheffield School of Clinical Dentistry, and colleagues agreed.

"Health care professionals performing particularly risk-prone procedures should consider every possible preventive measure to decrease the excess risk," they wrote. "Furthermore, increased awareness of the heightened risk in the vulnerable period after these procedures might lead to earlier diagnosis with a better chance for successful therapy and for avoiding the feared complications of the disease."

Use of antibiotic prophylaxis before dental and some other invasive medical procedures to prevent endocarditis is discouraged, even in high-risk patients, noted Janszky's group. Newer guidelines "severely restrict" the group of patients for whom such prophylaxis is recommended and no longer give indications for prophylaxis in the setting of various high-risk procedures.

Thornhill's group said it was surprising that the relatively "sterile" interventions of bone marrow puncture and transfusion made the list of potential endocarditis triggers.

"How should these data be interpreted? At face value, the implication is that virtually any inpatient or outpatient invasive procedure may be a trigger for subsequent infective endocarditis," they said, though they cautioned that the observational data cannot establish causality.

The study was based on 7,013 adults admitted with endocarditis from 1998 to 2011 with inpatient and outpatient procedures analyzed through the Swedish National Patient Register. The investigators took into account any invasive non-dental medical procedures, except those undertaken to treat endocarditis or infections that could lead to endocarditis.

It is also possible that some procedures were performed "as part of the investigation of patients who were already experiencing infective endocarditis but prior to an established diagnosis," according to the editorialists, citing for example anemia leading to a blood transfusion and a bone marrow biopsy before the correct diagnosis of infective endocarditis is made.

"Despite these criticisms, this work is by far the largest study to address the link between invasive medical procedures and subsequent infective endocarditis. It is the highest-quality data available to support an association between invasive medical procedures and infective endocarditis, and it mirrors the findings of a suggesting a possible increase in risk after invasive dental procedures," Thornhill's group said.