Mode switching in dual chamber pacemakers - Effect of onset criteria on arrhythmia-related symptoms

Aims Various mode-switching algorithms are available with different tachyar rhythmia detection criteria to be satisfied to initiate mode-switching. Thi s study evaluated three different mode-switching algorithms in patients wit h paroxysmal atrial fibrillation. Methods and Results Seventeen patients completed the study. Three mode-swit ching algorithms were downloaded as software into the pacemaker, each for 1 month in a single-blind, randomized sequence. The criteria to initiate mod e-switching were: mean atrial rate ('standard'), '4-of-7' or '1-of-1' atria l intervals to exceed the atrial detection rate. Symptoms for each were mea sured using the Symptom Checklist-Frequency and Severity index. The median number of mode-switch episodes increased From 20 for 'standard' to 39 for ' 4-of-7' (P=0.029 vs 'standard') and 103 for '1-of-1' (P=0.0012 vs 'standard ') onset criteria. Median duration of episodes decreased from 2.5 min with 'standard' to 1.4 min with '4-of-7' and 0.4 min with '1-of-1' onset criteri a. Frequency of symptoms was lower using '4-of-7' (18.2 +/- 12.0 vs 23 +/- 12.0, P=0.08) or '1-of-1' (20.4 +/- 12.4 vs 23 +/- 12.0, P=0.07) than 'stan dard' onset criteria. Severity of arrhythmia tended to be less with either '4-of-7' (16 +/- 10.4 vs 19.1 +/- 19.4, P=0.12) or '1-of-1' (17.5 +/- 10.3 vs 19.1 +/- 9.4, P=0.18) than with 'standard' onset criteria. Conclusions The more sensitive onset criteria for detection of atrial tachy arrhythmias were associated with lower frequency and severity of symptoms.