Antibacterial Envelope Cuts Heart Device Infections

NEW ORLEANS — An add-on antibacterial envelope led to a significantly lower incidence of major cardiac implantable electronic device infections versus standard infection-prevention strategies alone, without a higher incidence of complications, researchers reported here.

In the WRAP-IT study, treatment with the absorbable, multifilament mesh envelope (TYRX Absorbable Antibacterial Envelope) led to a 12-month Kaplan–Meier estimated event rate of 0.7% for the envelope group versus 1.2% for the standard group (hazard ratio 0.60, 95% CI 0.36-0.98, P=0.04), according to Khaldoun Tarakji, MD, of the Cleveland Clinic, and colleagues.

In terms of complications, the 12-month Kaplan–Meier estimated event rate was 6.0% for the envelope group and 6.9% for the standard (control) group (HR 0.87, 95% CI 0.72-1.06, P<0.001 for noninferiority), the authors reported at the American College of Cardiology annual meeting and simultaneously in the New England Journal of Medicine.

Approximately 1.5 million patients worldwide receive cardiac implantable electronic devices every year, Tarakji said, including pacemakers, implantable cardioverter defibrillators (ICD), and cardiac resynchronization therapy defibrillators (CRT-D). While the devices are safe, there is a risk of infection, particularly following device replacements, or other secondary procedures such as pocket revisions, lead changes, and upgrades, he noted.

“While the risk of major infections is low, when they do occur, they can be devastating for patients, resulting in invasive procedures, device removal, prolonged hospital stays and potentially death,” Tarakji stated. “Other than the use of antibiotics right before the device procedures, this is the first intervention proven to reduce the risk of infection in a randomized clinical trial of this magnitude.”

Study Details

The absorbable, single-use envelope is constructed from a multifilament knitted mesh, and coated with an absorbable polymer mixed with minocycline and rifampin. It elutes the antibiotics into the local tissue for a minimum of 7 days, and the envelope is fully absorbed in approximately 9 weeks.

The investigators randomized patients who were undergoing a cardiac implantable electronic device (CIED) pocket revision, generator replacement, or system upgrade or an initial implantation of a cardiac resynchronization therapy defibrillator 1:1 to receive the envelope or standard infection-prevention care. The latter included pre-procedure intravenous antibiotics and sterile techniques.

The study’s primary endpoint was infection resulting in system extraction or revision, long-term antibiotic therapy with infection recurrence, or death, within 12 months after the CIED implantation procedure. The secondary, safety endpoint was procedure-related or system-related complications within 12 months.

In total, 6,983 patients (mean age 70; 28.3% women) underwent randomization (3,495 to envelope; 3,488 to control). The authors reported that the primary endpoint occurred in 25 patients in the envelope group and 42 patients in the control group, while the secondary endpoint occurred in 201 patients in the envelope group and 236 in the control group.

The mean duration of follow-up was 20.7 months, and the investigators reported that major CIED-related infections through the follow-up period occurred in 32 patients in the envelope group and 51 in the control group (HR 0.63, 95% CI 0.40-0.98).

For the type of major CIED infections, pocket infections occurred in 14 of the envelope and 36 in the control group (HR 0.39, 95% CI 0.21-0.72). There were more cases of bacteremia or endocarditis in the envelope group versus controls (11 vs 6, HR 1.57, 95% CI 0.61-4.05).

There were 349 deaths in the envelope group and 365 deaths occurred in the control group throughout the follow-up period (36-month Kaplan-Meier rate of death 17.4% and 17.8%, respectively, HR 0.96, 95% CI 0.83-1.11).

In a subgroup analysis of patients who received a high-power device (ICD or CRT-D), major CIED infections occurred in 18 patients in the envelope group and 35 patients in the control group (12-month Kaplan-Meier estimated event rate, 0.7% and 1.4%, respectively, HR 0.51, 95% CI 0.29-0.90).

In patients who received low-power devices (pacemaker; CRT-pacemaker), major CIED infections were seen in seven patients in the envelope group and seven patients in the control group (12-month Kaplan-Meier estimated event rate 0.9% and 0.8%, respectively, HR 1.02, 95% CI 0.36- 2.92), the authors reported.

While “The interaction effect for subgroup according to device type was not significant,” they noted, “The beneficial effects of the envelope in preventing major CIED infection in 12 months were more pronounced in patients with high-power devices than in those with low-power devices or an initial CRT-D.”

Study limitations included the fact that consecutive patients were not enrolled because the trial was limited to patients receiving generators from one device manufacturer. Also, the envelope was commercially available at the time of trial, which may have swayed participation. Finally, the use of immunosuppressive agents was not balanced between the two groups.

‘Encouraging,’ but Lasting?

“Adjunctive use of an antibacterial envelope resulted in a 40% lower incidence of major cardiac implantable electronic device infection than standard-of-care infection-prevention strategies alone,” Tarakji’s group reported. “Patients who received the envelope did not have more procedure-related or system-related complications than those who did not receive it.”

“These results add to the existing body of literature on the safety and efficacy of the envelope in reducing cardiac implantable electronic device infections,” they noted. “Although the use of the envelope may require dissection of a slightly larger cardiac implantable electronic device pocket, we did not observe a significant difference in the rate of complications, for example hematoma, or procedure time that could be attributed to this. There were fewer system revisions in the envelope group than in the control group and no complications due to allergy to the envelope mesh, polymer, or antibiotics.”

Ray Gibbons, MD, of the Mayo Clinic in Rochester, Minnesota, told MedPage Today that “Infections in these patients is a major cause of concerns for doctors and patients. Sometimes the problem is severe enough that the patient will need to be hospitalized for weeks.”

Gibbons, who was not involved in the study, cautioned that “while these results are encouraging, longer-term studies on how long these devices remain clear of infection is required. These devices will be implanted for 5 years or longer, so we are going to have to watch to see how long this protection lasts.”