By Marilynn Larkin
NEW YORK (Reuters Health) - Contact allergy to implanted devices is rare, but should be considered and tested for in certain situations, researchers say.
"When there is clinical concern for infection, history of prior device extraction, history of redness at the implant site or negative culture results, patients should be tested for device allergy," Dr. Amber Atwater of Duke University School of Medicine in Durham, North Carolina told Reuters Health.
"However," she said by email, "I recommend that this only be done by a physician who is trained in complex patch testing and understands the chemicals that are relevant to cardiac devices."
Dr. Atwater and colleagues analyzed data on 11 patients (mean age, 58; 27% women) who completed 15 patch test sessions at Duke from 2012 to 2017. Six had implanted pacemakers and five had implanted cardioverter defibrillators.
As reported online April 3 in JAMA Dermatology, common indications for patch testing were concern for allergy (100%) or infection (60%), skin eruption (80%) and skin symptoms (67%). Eight patients (72.7%) had erythema at the implant scar.
Eight patients underwent device extraction. The duration of implantation was one to 77 months if the device was extracted before patch testing (six patients), and one to 11 months if it was extracted after.
Six patients (55%) had positive patch test reactions, including four (36%) to metals. Other positive results included reactions to rubber accelerators, lidocaine, silicone, and a device-related dexamethasone plug.
Seven of the patients who underwent extraction had culture results available, five of which were negative.
Success after reimplantation ranged from 11 to 36 months. As of September 15, 2017, one patient had died; the other devices were functioning as expected.
Three of the five patients with negative patch test results kept their devices, "which demonstrated that the negative patch test result had important diagnostic value," according to the authors. The other two had their devices extracted prior to testing, and reimplantation was not indicated.
While it is possible to test patients for allergies in advance of implantation, "that is not currently standard of care," Dr. Atwater noted. "The American Contact Dermatitis Society recommends, 'In patients who strongly believe that they are metal allergic, evaluation through patch testing ... before implantation of a metal device may be prudent.'"
"It is important to understand that there is not a guarantee that a person who is allergic to a specific chemical will react to that chemical if it is present in the implanted device," she concluded.
Dr. Adam Friedman, Professor and Interim Chair of Dermatology at George Washington School of Medicine and Health Sciences in Washington, DC, commented in an email to Reuters Health, "This small retrospective study aims to highlight the utility of patch testing common pacemaker allergens in those patients with chronic skin reactions at the site of implantation as a means to properly guide replacement for those who do and do not have identified sensitivities to said allergens."
"I am personally a fan of biologically-based medical decision making. Thus, I advise caution, as patch testing is both a costly and time-consuming diagnostic test and should be used meaningfully," he said. "Every patient with a pacemaker who develops a 'rash' at the pacer site should not undergo such testing - mindful selection should be the objective."
"One should use the clinical phenotype of the reaction to guide this decision," he added, "meaning an eczematous eruption would warrant further investigation while a red, painful rash should push one in a different direction (i.e., irritant versus infection).
JAMA Dermatol 2019.