Dual-chamber (DC) pacing benefits are impaired by the occurrence of atrial arrhythmias (AA). Pacemakers (PM) have been enhanced by a mode-switch function (MSF) which allows the switch from DDD(R) to DDIR pacing in presence of AA.

We analyzed MSF at 6 and 12-month (m) follow-up in 369 patients (Pts) aged 77+/−9 y, free of permanent AA (59%), implanted with Kappa® DC PMs (Medtronic, MN, USA) for II and III AV block (65%), and sinus dysfunction (SD) (35%). 52% had no cardiopathy and there was no difference in electrical parameters at implant regardless lead and indication.

No specific programming was imposed. MS function data was collected at each follow-up: number of MS, average percentage of time in AA. EGM was used to confirm AA in most cases.

The MSF shows AA episode rate of 61% at 6m and 48% at 12m. Moreover, 29% of pts (Gr1) had no AA during the 12m, 11% had AA only during the last 6m (Gr2), 24% only during the first 6m (Gr3 and Gr5) and 37% during the 12m (Gr4 and Gr6). Statistically, there was no significant difference between groups concerning the number of MS and between the percentage of time in AA at each follow-up.

Long-term follow-up confirms results already described in the literature, and the MS event counters may predict the existence of AA. EGM confirms the specificity of this function. Number of MS is significantly high in SD (p<0.05), whereas the observation of a high number of MS may also point to oversensitivity of the MSF. Percentage time spent in AA is a revealing parameter, as it represents average time during which pts had been in AA since the previous follow-up.

This study confirms that AA occurrence remains an important complication in PM patients, regardless indication. Simple examination of MS recordings can lead to suspicion of major AA. The gravity of this AA can be quickly determined, but only detailed examination of MS episodes can confirm the diagnosis.