First-ever tool helps predict risk of infection after heart device implantation

Cardiovascular implantable electronic devices (CIED) save lives – there’s no question about it. But, on rare occurrences, infections can lead to serious, often life-threatening complications. Last year, it was determined by science that more aggressive use of antibiotics around the time of device implantation does not produce significantly lower risks for the development of such infections.

This was one of the major takeaways from the PADIT trial – the acronym standing for Prevention of Arrhythmia Device Infection Trial – which tested the clinical effectiveness of incremental perioperative antibiotics to reduce device infection. Over four randomly assigned six-month periods, researchers analyzed data from more than 19,500 patients across 20 Canadian centres (and four more centres in Holland). The study is to date the largest device trial ever.

While it yielded no statistically significant finding for physicians, the database collected during the study did turn researchers on to a new question altogether, says Dr. David Birnie, staff cardiac electrophysiologist and Deputy Division Head of Cardiology at the University of Ottawa Heart Institute. Dr. Birnie is also a member of the PADIT steering committee. The question: Can science predict what a given patient’s risk for developing an infection is before one goes into a CIED procedure? Dr. Birnie says the answer (on a case-by-case basis), is ‘yes.’

We found that you could estimate [a patient’s risk of infection] very accurately, using the scoring system for device infection we developed.

- Dr. David Birnie, staff cardiac electrophysiologist, University of Ottawa Heart Institute

“We found that you could estimate [a patient’s risk of infection] very accurately, using the scoring system for device infection we developed,” he said, adding that the resulting system is “very physician- and patient-friendly,” and that it “should be readily adopted in clinical practice pending a peer review.”  

This May (2019), Dr. Birnie took the floor at the 40th Annual Heart Rhythm Scientific Sessions (Late Breaking Clinical Trials) in San Francisco, USA to provide the latest update with regard to the PADIT trial. Using data collected from the original study, researchers now say they have determined five independent predictors of device infection. They’ve used their findings to develop a novel infection risk score for assessing patients being considered for a CIED procedure.

How it works: The PADIT scoring system assigns weighted points to patients based on the ‘tell-tale’ characteristics of their procedure and elements of their personal medical history. It then determines one’s level of risk based on the total number of accumulated points (one can amount as many as 14 total points).

• Add one (1) point for a patient who has had a prior procedure. Add four (4) points for a patient who has had more than two (2).
• Add one (1) point for patients between the age of 60 and 69. Give two (2) points to patients under 60.
• Having depressed renal function will score one (1) point.
• Having an impaired immune system due to disease or drug therapy scores three (3).
• And finally, points are assigned depending on the type of procedure being considered. Factor two (2) points for an ICD (implantable cardioverter defibrillator), four (4) points for CRT (cardiac resynchronization therapy), and five (5) points go to any one requiring a revision or upgrade to an already implanted CIED.

Coincidentally, (or perhaps not), the five elements of the risk-prediction system form to spell the same acronym as the trial from which they were developed. (That is: Prior procedure, Age, Depressed renal function, Immunocompromised, and Type of procedure, spelling PADIT).

A patient scoring fewer than four points is deemed at lowest risk for infection. Between five and six points means a moderate or intermediate risk. Scoring anything above seven points signals to a physician a high-risk of developing a serious infection.

As an example, Dr. Birnie estimates an 85-year old patient with renal dysfunction who needs a battery changed on a previously implanted device would amount to at least seven points. For such patients, Dr. Birnie says the data suggests the likeliness of developing a serious, life-threatening infection is in the area of 4%, which may seem small, but is enough to raise significant alarm.

“A score of seven or higher may suggest the potential harm to the patient is greater than the would-be benefit of receiving a new device,” Birnie says. “The PADIT risk score system will be instrumental in helping physicians make important decisions with their patients, and in identifying additional measures when it comes to the prevention of infections during CIED therapy.”

Of course, all of this is dependent on further validation and even modification, Dr. Birnie notes.  The PADIT infection score warrants validation in an independent cohort.