MAGNETOcardiography Parameters to Predict Sudden Cardiac Death (MAGNETO-SCD) or Ventricular Events From Implantable Cardioverter Defibrillators

Background: Sudden cardiac death (SCD) caused by ventricular arrhythmias remains a leading cause of mortality worldwide. Current risk stratification for implantable-cardioverter defibrillator (ICD) insertion relies heavily on left ventricular ejection fraction, which has limited discriminatory power. Objectives: The goal of this study was to evaluate whether established/novel magnetocardiography (MCG) parameters (Rotation Score and Angular Dynamics) were associated with subsequent ICD therapies. Methods: Magneto-SCD (Magnetocardiography [MCG] Parameters in the Prediction of Future ICD Therapy) was a prospective, multicenter observational study of de novo ICD recipients across 5 UK hospitals between September 2019 and November 2021. MCG data were obtained by using a portable, unshielded, room temperature device. The primary outcome was occurrence of any appropriate ICD therapy. Secondary outcomes included any appropriate shocks, sustained ventricular arrhythmias, and all-cause mortality. Results: A total of 104 patients were recruited (mean age ± SD 65.5 ± 12.2 years; 80% male); 90 had analyzable MCG data. After mean follow-up of 36.0 ± 17.5 months, 17 received appropriate ICD therapy, with a significantly higher median (Q1-Q3) Rotation Score (504.4 [398.5-665.3] vs 331.7 [256.6-472.2]; P = 0.005) and Angular Dynamics (3.26 [2.55-3.81] vs 2.50 [2.12-3.13]; P = 0.029). These differences in Rotation Score/Angular Dynamics were more marked in those with appropriate shocks (539.7 [428.5-674.5] vs 335.1 [256.3-476.6]; P = 0.001 and 3.348 [2.879-3.830] vs 2.492 [2.117-3.132]; P = 0.005, respectively). Each 1-SD increase in Rotation Score/Angular Dynamics was associated with a higher hazard of appropriate shocks (2.53 [95% CI: 1.53-4.18] and 2.34 [95% CI: 1.37-4.00]) and appropriate therapy. Rotation Score/Angular Dynamics showed apparent discrimination for shocks in this small data set (receiver-operating characteristic area under the curve: 0.82 and 0.77), although CIs were wide and event numbers were small. Associations persisted after limited adjustment for age and left ventricular ejection fraction, supporting an association independent of age and left ventricular ejection fraction within an ICD-selected cohort, although this requires independent validation. Conclusions: In the current study, novel rotation-based MCG parameters were associated with subsequent appropriate ICD therapies, particularly shocks. These exploratory findings support the feasibility of unshielded MCG in routine clinical practice and suggest that Rotation Score/Angular Dynamics may capture arrhythmic substrate and merit further investigation and validation in larger cohorts.