Incremental value of atrial sensing in the diagnosis of ICD recordings: findings from the THINGS registry

Abstract Background Automatic diagnosis of implantable cardioverter defibrillator (ICD) requires confirmation through analysis of electrograms (EGM) recordings by an electrophysiologist (EP) specialist. Purpose To investigate whether the atrial sensing capability in single-chamber ICD improves reliability in episodes assessment. Methods The THINGS registry enrolled 526 consecutive patients without atrial pacing indication who underwent single-lead ICD implantation. Of them, 343 patients received a conventional single-chamber ICD (ICD VR) and 183 a single-lead ICD with atrial sensing capability (ICD DX, BIOTRONIK). Device-detected ventricular episodes were independently classified by two experienced electrophysiologists as ventricular (VT) or supraventricular tachycardia (SVT) by analyzing the EGMs. In case of disagreement, a third experienced EP specialist, blinded to previous assessment, was consulted. The inter-rate reliability was evaluated using the Cohen's kappa (k) coefficient in the ICD VR and ICD DX group. Results A total 441 (383 in the ICD VR and 58 in the ICD DX group) device-detected events were analyzed. Using ventricular EGM alone for ICD VR patients, the proportion of observed agreement between the 1st and 2nd adjudicator was 86.4% consisting of 268 (70.0%) episodes confirmed as VT and 63 (16.4%) classified as SVT. The k coefficient was 0.61 and no agreement was reached for 52 (13.6%) tracings. For them, the third assessment had low agreement with both previous EP evaluations (the k coefficients 1st/3th and 2nd/3th EP specialist were 0.03 and −0.05, respectively). In ICD DX group, with available atrial EGM, the proportion of observed agreement in the first stage improved to 93.0%: 44 (75.8%) episodes were adjudicated as VT and 10 (17.2%) as SVT with a k=0.79. Only 4 (7.0%) recordings had a discordant classification. For them, the 2nd and 3rd EP specialist had perfect agreement (k=1). Conclusions Atrial sensing capability improves EP specialist assessment of ICD episodes allowing dual EGMs analysis. Misinterpretation of ICD recordings may thus be less common in ICD DX than in conventional single-chamber ICD VR and may improve clinical decisions. Funding Acknowledgement Type of funding sources: None.