VENTRICULAR PROTECTION AGAINST ATRIAL ARRHYTHMIAS IN DDD PACING BASEDON A STATISTICAL APPROACH - CLINICAL-RESULTS

Atrial arrhythmias (AAI are commonly encountered in DDD paced patients . Newer dual chamber pacemakers (PM) possess mode switching functions that convert pacing to an asynchronous mode when AAs are detected. The lack of a reliable mode switch leading to rapid, irregular ventricula r responses may result from AA undersensing. To avoid this, the DDDR P M Chorum 7234 Ela Medical AA diagnosis is based on a statistical appro ach: the PM constantly compares arrhythmic and sinus cycles and, based on ''strong'' and ''weak'' criteria, provides for rapid or slower mod e switch. The aim of the study was to evaluate the efficiency and reli ability of these two criteria. Thirty-one patients with a Chorum 7234 implanted for AV block (11), sinus dysfunction (10), both (5), or hype rtrophic obstructive cardiomyopathy (5) were evaluated at 24 hours and I month using the internal memory (IM) of the PM, surface 24-hour Hol ter recordings, and exercise testing. Interrogation of the IM on the f irst day of study showed that 8 patients had mode switching episodes, based only on the strong criterion confirmed by the surface Holter rec ording. At 1 month, the LM revealed mode switching episodes in 22 pati ents, 6 of whom had used the weak criterion. No inappropriate mode swi tching episode was recorded during exercise testing at the 1-month fol low-up. These results confirm the reliability and efficiency of this a lgorithm as well as the requirement for a specific algorithm to compen sate for transient loss of sensing during AA.