Single- versus dual-chamber ICD discriminators for tachyarrhythmia detection: a remote monitoring based, single-center study

Implantable cardioverter defibrillator (ICD) systems are available in both single-chamber (SC) and dual-chamber (DC) configurations, with discrimination functions varying accordingly. Although expert opinion generally suggests that modern SC discriminators equipped with morphology detection algorithms are equally effective to DC systems in tachyarrhythmia discrimination, only limited and contradictory data are available. In most previous reports the choice between SC or DC discrimination was determined by the number of the implanted leads.

We aimed to assess the efficacy of SC vs. DC ICD discriminators in malignant tachyarrhythmias by performing a head-to-head comparison of devices from a single manufacturer, whose ICDs also include single-lead devices with a programmable option of SC or DC discriminators (VDD ICD).

Data from ICD recipients followed up with the Home Monitoring system were retrospectively analysed. As primary outcome we compared the risk of inappropriate therapy between patients, whose ICD was programmed to SC (i.e. Stability/Onset/MorphMatch) vs. DC (i.e. SMART) discrimination algorithms. A sensitivity analysis was also conducted including only patients into the SC discrimination group with activated morphology discriminator.

A total of 211 patients (mean age 64±12, male 75%, primary prophylaxis 33%) were included. All patients had been implanted with an ICD from the same manufacturer (VVI: 62, VDD: 94, DDD: 14, CRT-D: 41), and were remotely followed up. Among these, 71 ICDs were programmed to SC, while 98 were programmed to apply DC discriminators. In the remaining 42 cases, only VF zone was programmed, therefore these patients were excluded from further analysis. Of the SC discriminator group, 35 (49%) patients were programmed to utilize morphology discriminator. There was no significant difference between the SC and DC groups in atrial (6±3 vs. 4±3 mV; p=0.062) or ventricular sensing (15±6 vs. 14±7 mV; p=0.781) at the time of introduction to remote monitoring. We did not detect difference in the risk of inappropriate therapies between the SC and DC discriminator groups (HR 2.274; 95% CI 0.437-11.815; p=0.329), and we did not find difference in the predefined sensitivity analysis between the two groups (HR 2.177; 95% CI 0.254-18.664; p=0.478).

Our data suggest that there is no significant difference in the performance of tachyarrhythmia discrimination between single- and dual-chamber discriminators. The findings of the present study support single-chamber discriminators as a viable alternative even for patients with implanted dual-chamber devices.