DISTRIBUTION OF FAST HEART-RATE EPISODES DURING PAROXYSMAL ATRIAL-FIBRILLATION

Objective-To investigate the defibrillator waiting time (time between the recognition of atrial fibrillation and the actual shock) by studyi ng paroxysmal atrial fibrillation episodes with RR intervals shorter t han a certain limit (that is, episodes during which defibrillation sho uld not be attempted). Methods-Long term 24 hour Holter recordings fi om a digoxin v placebo crossover study in patients with paroxysmal atr ial fibrillation were analysed. In all, 23 recordings with atrial fibr illation episodes of at least 1000 ventricular cycles and with < 20% H olter artefacts or noise were used (11 recorded on placebo and 12 on d igoxin). For each recording, the mean (''mean waiting time'') and maxi mum (''maximum waiting time'') duration of continuous sections of atri al fibrillation episodes with all RR intervals shorter than a certain threshold were evaluated, ranging the threshold from 400 to 1000 ms in 10 ms steps. For each threshold, the mean and maximum waiting times w ere compared between recordings on placebo and on digoxin. Results-Bot h the mean and maximum waiting times increased exponentially with incr easing threshold. Practically acceptable mean waiting times less than one minute were observed with thresholds below 600 ms. There were no s ignificant differences in mean waiting times and maximum waiting times between recordings on placebo and digoxin, and only a trend towards s horter waiting times on digoxin. Conclusions-Introduction of a minimum RR interval threshold required to deliver atrial defibrillation leads to practically acceptable delays between atrial fibrillation recognit ion and the actual shock. These delays are not prolonged by digoxin tr eatment.