Staph Responsible for Most Heart Implant Infections, Study Finds

New enrichment culture techniques have helped researchers identify infection types for patients with different kinds of heart implant devices.

A new study examines the risk of heart implant infections, suggesting that many patients who receive medical devices to treat serious cardiac conditions develop infections, most commonly involving difficult to treat staph bacteria.

According to a report published in the medical journal Heart Rhythm on April 7, about 60% of infections suffered among patients with cardiac implantable electrical devices (CIED) are from staphylococcus aureus. However, patients who suffer heart implant infections much later after the devices are placed in their body are more likely to contract Cutibacterium acnes infections, researchers noted.

Cardiac implantable electrical devices are battery-powered devices placed in the chest to monitor and regulate the heart’s rhythm. The devices offer life-saving electrical shocks to stimulate the heart, regulate the rhythm, or restore a normal heartbeat if an abnormal one is detected. They include pacemakers, implantable cardioverter-defibrillators and cardiac synchronization therapy devices.

Researchers have noted that patients who have CIEDs often experience infections, and in 10% to 30% of those patients it has historically been unclear what caused the infections.

In this new study, Japanese researchers focused on determining the specific causes of CIED infections. They analyzed 117 CIED infection patients and categorized their infections based on onset and timing, using enrichment culture techniques to identify slow-growing bacteria.

The research team, led by Dr. Mitsuru Takami, then categorized infections as early onset if they occurred within 365 days of the device implant procedure.

Researchers were able to identify the specific bacteria responsible for the infection in 97% of cases. According to the findings, staph infections accounted for the majority, making up 63% of all infections. Following that, Cutibacterium acnes accounted for 18% of infections.

The data indicated that patients who suffered from early infections during the first year after a CIED was implanted often experienced pocket infections, were more commonly female, had lower left ventricular ejection fraction, higher brain natriuretic peptide levels, and lower kidney function.

Pocket infections are found in the area directly around the implanted device. Lower left ventricular ejection fraction is a condition where the heart’s left ventricle does not pump enough blood during each heartbeat. It can indicate heart failure or other conditions. High natriuretic peptides can indicate heart failure as well.

Patients who suffered late infections were more likely to have Cutibacterium acnes infections. Cutibacterium made up 24% of late infections compared to 8% for staph infections.

Staph infections were more likely to manifest within the first year, making up 43% of early infections, while Cutibacterium made up only 25% of early infections.

Researchers said the specific method they used, enrichment culture, helped detect a higher rate of bacteria responsible for infections compared to conventional blood cultures.

Using enrichment cultures instead of the standard method may help highlight the difference in confirmed bacteria strains compared to prior studies, researchers said.

A study published by researchers from Duke University in 2022 concluded that, among patients who suffer an infection after a CIED is implanted, 80% opt for antibiotics to treat the infection, even though data indicates the best course of action is to remove the device to clear the infection.