Invasive procedures—including cardiovascular—boost risk of endocarditis

A Swedish study published in the Journal of the American College of Cardiology provided evidence that invasive medical procedures—including several of the cardiovascular variety—increase the risk of infective endocarditis. This finding could reinvigorate the debate over whether preventive antibiotics should be administered before certain procedures, researchers said.

Coronary artery bypass graft (CABG) surgeries, in particular, were strongly linked to the life-threatening condition—carrying a 14-fold increase in relative risk, among the top five of all inpatient procedures analyzed. Angioplasty was associated with 3.5 times the risk, while coronary angiography performed in both the inpatient and outpatient settings more than quadrupled the risk of infective endocarditis.

“Among therapeutic procedures, cardiovascular operations, especially coronary revascularizations; procedures on skin and wounds; chronic hemodialysis; blood transfusion; and various noncardiovascular operations carried the highest risk,” wrote lead author Imre Janszky, MD, PhD, and colleagues. “Among diagnostic procedures, bone marrow puncture, coronary angiography, and some transluminal endoscopies, especially bronchoscopy, were the most important.”

The authors identified 7,013 cases of infective endocarditis occurring from 1998 through 2011 at Swedish hospitals. The design of their case-crossover study—in which patients served as their own controls—allowed them to eliminate much of the confounding associated with different patient variables.

Janszky and colleagues investigated whether there was an invasive medical procedure in the 12 weeks before infective endocarditis onset, and compared a patient’s exposure in that timeframe to a 12-week period exactly one year before to calculate the relative risks associated with the interventions.

“Several chronic cardiac conditions or lifestyle related factors such as diabetes might predispose individuals for infective endocarditis, and these conditions are also associated with the probability of undergoing an invasive medical procedure,” the researchers wrote. “However, in the case-crossover approach, due to self-matching, such factors are unlikely to confound the association between procedures and risk for infective endocarditis.”

Antibiotic prophylaxis for medical procedures has been downgraded in clinical guidelines, the authors noted, but there remains debate over the necessity of the preventive treatment because of sparse data on the topic. Currently, only high-risk patients undergoing invasive dental procedures are recommended for pre-treatment antibiotics, noted the authors of an accompanying editorial.

Importantly, the analysis by Janszky et al. excluded dental procedures because most of them weren’t performed in hospitals and therefore weren't captured by the study database.

“Health care professionals performing particularly risk-prone procedures should consider every possible preventive measure to decrease the excess risk,” Janszky and colleagues 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.”

The editorialists said the study is “the highest-quality data available to support an association between invasive medical procedures and infective endocarditis,” and also the largest such study. But they also pointed out it would require 476 patients to be treated with antibiotics to prevent one case of effective endocarditis. While that number might be smaller for the highest-risk procedures, it did little to convince them that antibiotic prophylaxis should be given a widespread endorsement.

“Broadening the scope of antibiotic prophylaxis to include all of these procedures is unlikely to be the solution,” wrote the three researchers from the United Kingdom, including corresponding author Martin H. Thornhill, MBBS, BDS, PhD. “At least for those procedures where sterility should be easy to achieve and maintain, the solution is more likely to lay with improved sterile technique, infection control procedures and identifying systematic approaches for reducing health care–associated bacteremia rather than necessarily advocating antibiotic prophylaxis.”