Impaired alert tone perception and post-MRI malfunction in patients with S-ICD: a three-center analysis

Background

The subcutaneous implantable cardioverter-defibrillator (S-ICD) provides audible alert tones to indicate device or lead issues. Impaired perception of this warning tone or functional loss after magnetic resonance imaging (MRI) may compromise patient safety.

Purpose

This study investigated (1) factors associated with inability of patients to perceive the alert tone, and (2) the impact of MRI scans on post-scan tone function.

Methods

A total of 262 S-ICD patients from 3 European centers were prospectively included. The alert tone was demonstrated to all patients. Age, body mass index (BMI), sex, and diagnosed hypoacusis were analyzed as predictors of tone perception using multivariable logistic regression. In an additional analysis, a subgroup of 33 device patients who had previously undergone MRI scanning were evaluated for alert tone function loss, stratified by scan region (e.g. cardiac, cranial, spinal, abdominal). Differences across MRI regions were assessed using Fisher’s exact test and pairwise odds ratios.

Results

Alert tone testing confirmed functionality in 250/262 devices (95.4%). Of these 250 patients with a functional tone, 12 (4.8%) were unable to perceive it. Higher age and hypoacusis were independent predictors of failure to perceive the tone (both p < 0.05).

In a separate analysis focusing on the technical integrity of the alert tone after MRI exposure, we evaluated the subgroup of patients who had undergone MRI scanning. Among 33 MRI-exposed devices, an objective loss of tone function post-scan occurred in 10 (30.3%). Only 0.9% of devices in patients without MRI did not have a functional tone; (p < 0.001). The incidence of tone loss varied between MRI regions without reaching the level of statistical significance (overall Fisher’s exact test, p = 0.81). No single MRI region showed a significantly higher risk compared with the reference region in pairwise analyses.

Discussion/Conclusions

In a large all-comer S-ICD cohort, 4.8% of patients are unable to hear the alert tone. Advanced age and pre-existing hypoacusis independently reduced the likelihood of perceiving the S-ICD alert tone. Undergoing an MRI had a significantly high risk of loss of alert tone function. These findings emphasize the importance of testing the audible alert and demonstrating it to patients. Telemetric surveillance should be considered in S-ICD management, especially in patients unable to perceive the alert tone.Figure 1.Predictors Forest Plot