New risk score predicts cardiac-device infection

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Risk score’s strength stems from large database

I like this new infection risk score. It addresses a very clinically relevant issue. It’s important for the electrophysiology community to better understand how to best manage infections related to cardiac rhythm devices and ideally prevent them from happening.

Dr. Ulrika Birgersdotter-Green, professor of medicine, University of California, San Diego Mitchel L. Zoler/MDedge News

Dr. Ulrika Birgersdotter-Green

The strength of the PADIT risk score, compared with past attempts to develop a risk-assessment tool for this situation, was the size of the database the investigators worked with: nearly 20,000 patients. This was many more patients than had ever been used before to address this question. Unfortunately, the data collected from in PADIT did not include information on their anticoagulant treatment.

I’m not a big fan of risk scores in general because they can sometimes detract from independent thinking about how to manage a patient. However, it is also helpful to have this type of risk-assessment information when discussing management options with a patient.

The PADIT risk score may also help identify which patients could potentially benefit the most from an antibiotic-eluting envelope when receiving an implanted cardiac-rhythm device. Recently reported results from WRAP-IT showed that routinely using envelopes cut the incidence of major infections by a relative 40%, but in absolute terms, the number needed to treat with the envelop to prevent one major infection was about 200 patients, a big number given the high cost of the envelope (N Engl J Med. 2019 May 16;380[20]:1895-905). It is therefore very interesting to think about using the PADIT risk score to better target an effective but expensive preventive measure like an antibiotic-eluting envelop to patients at the highest risk for infection.

Ulrika Birgersdotter-Green, MD , professor of medicine and director of pacemaker and ICD services at the University of California, San Diego, made these comments as a designated discussant for the report. She has been a consultant to and received honoraria from Abbott, Boston Scientific, and Medtronic.



– Researchers have devised a five-item scoring formula to quantify the risk for infection in patients undergoing placement, revision, or removal of a cardiac-rhythm device based on data from nearly 20,000 patients enrolled in a recent infection-prophylaxis trial.

The risk score can help identify patients who might benefit from intensified antibiotic prophylaxis, and it can also help during shared decision making with patients to better understand the risk a patient faces from infection, compared with their predicted device benefit, David H. Birnie, MD, said at the annual scientific sessions of the Heart Rhythm Society.

The new risk score produced a concordance statistic, the area under the receiver-operator characteristic curve, of 0.704. It showed that, although it could use further validation, the score as it currently stands has substantial predictive value, said Dr. Birnie, professor of medicine at the University of Ottawa and deputy chief of cardiology at the University of Ottawa Heart Institute. “It’s certainly better than anything we have now,” he said in a video interview.

Dr. Birnie and his associates used data they collected on baseline characteristics and infection outcomes of the 19,603 patients enrolled in PADIT (Prevention of Arrhythmia Device Infection Trial) who underwent a rhythm-device procedure at 1 of 28 participating Canadian centers. The primary aim of PADIT was to assess the safety and efficacy of an intensified antibiotic-prophylaxis regimen, compared with a standard regimen of a cefazolin infusion just before the procedure. The study’s primary endpoint was the incidence of hospitalization for device infection during 1-year follow-up, and while the intensified prophylactic regimen linked with a 23% relative reduction in the hospitalization rate, compared with standard treatment, the difference was not statistically significant (J Am Coll Cardiol. 2018 Dec 18;72[24]:3098-109).

The researchers analyzed the baseline patient data and the blindly adjudicated infection outcomes and identified five factors that were independently associated with an increased infection rate. They organized the five factors and produced a formula they call the PADIT score (see chart). Those five factors are: prior procedures (the greater the number the greater the risk), age (which unexpectedly had an inverse relationship with infection incidence), depressed renal function, immuno-compromised status, and type of procedure. A patient can potentially score 0-15 points.

Among the PADIT patients a score of 0 correlated with about a 0.3% rate of hospitalization for a device-related infection during 1 year of follow-up, a score of 5 with about a 1.1% rate, a score of 6 with about a 1.8% rate, and a score of seven or more with a 3.4% infection rate over the following year. About 5% of patients had a score of 7 or more, and roughly another 5% had a score of 5 or 6, Dr. Birnie said. At his center, clinicians have begun routinely calculating scores for patients scheduled for an arrhythmia-device procedure, and they are considering routinely administering added antibiotic prophylaxis to patients with a preprocedural score of 6 or higher. They may also use the score to determine whether to use the antibacterial envelope recently reported to prevent cardiac-device infections (N Engl J Med. 2019 May 16;380[20]:1895-905).

“It’s very easy for patients to get to a PADIT score of 7 or higher,” Dr. Birnie noted. As an example, he cited a common patient, an 85-year-old with renal dysfunction who is under consideration for a second replacement of an implantable cardioverter defibrillator. The patient would score 1 point for renal insufficiency, 2 points for the type of device, and 4 points for having a prior history of two devices, and the consequent 3.4% risk for infection might counterbalance the potential benefit this elderly patient could expect from the new device. The score will be very important for targeting treatment, shared decision making, and selection of patients for future intervention trials, he concluded.

Dr. Fred M. Kusumoto, director of heart rhythm services, Mayo Clinic, Jacksonville, Fla. Mitchel L. Zoler/MDedge News

Dr. Fred M. Kusumoto

“I think this risk score will change practice by giving clinicians a better idea of a patient’s risk for infection,” commented Fred M. Kusumoto, MD, professor of medicine at the Mayo Medical School, Rochester, Minn., and director of heart rhythm services at the Mayo Clinic in Jacksonville, Fla. The PADIT score will help identify patients for whom leaving a device in place is a better option than taking it out because of their infection risk. The risk score could also help improve the cost effectiveness of preventive treatments, such as antibiotic-eluting envelopes, by targeting treatment to higher-risk patients, Dr. Kusumoto said during a press briefing.

SOURCE: Birnie DH. Heart Rhythm 2019, Absract S-LCT02-01.

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