title: Temporal variability of atrial tachyarrhythmia burden in bradycardia-tachycardia syndrome patients.
abstract: OBJECTIVE
  Several studies have tested non-pharmacological therapies for atrial tachyarrhythmias (ATs) by measuring the cumulative time (burden) the patient spends in arrhythmia. Contradictory results questioned either therapy efficacy or statistical power of the trials. We studied AT burden variability in patients paced for sinus node disease (SND) in order to interpret currently published data appropriately and to evaluate reliable sample sizes.
  
  
  RESULTS
  One hundred and five patients with AT and SND received a dual chamber pacemaker with antitachyarrhythmia-pacing capability, and were followed for 13 months. Seventy-eight patients (74%) suffered AT recurrences. Device-gathered diagnostic measures were used to simulate results of randomized studies both with crossover and parallel design. The sample size required for statistically significant results was calculated as a function of the expected therapy-induced burden reduction. AT burden intra-patient variability was high: 43% of patients showed intrinsic fluctuations hiding any therapy-induced burden reduction lower than 30%. Demonstrating therapeutic breakthrough through a 6 month study would require 290 patients with crossover design and 5800 patients with parallel design. Doubling the study period requires 400 and 3000 patients, respectively.
  
  
  CONCLUSIONS
  Patients with AT and paced for SND showed high intra-patient burden variability, which could possibly hide an AT burden reduction induced by a therapy. Previous studies involving non-pharmacological therapies utilizing AT burden endpoints could lack the power to reach statistical significance.
authors.affiliation: Institute of Internal Medicine and Cardiology, University of Florence, Viale Morgagni 85, 50134 Florence, Italy. lpadeletti@interfree.it
authors.forename: Luigi
authors.initials: L
authors.lastname: Padeletti
authors.forename: Massimo
authors.initials: M
authors.lastname: Santini
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Boriani
authors.forename: Gianluca
authors.initials: G
authors.lastname: Botto
authors.forename: Alessandro
authors.initials: A
authors.lastname: Capucci
authors.forename: Michele
authors.initials: M
authors.lastname: Gulizia
authors.forename: Renato
authors.initials: R
authors.lastname: Ricci
authors.forename: Andrea
authors.initials: A
authors.lastname: Spampinato
authors.forename: Paolo
authors.initials: P
authors.lastname: Pieragnoli
authors.forename: Eduardo
authors.initials: E
authors.lastname: Warman
authors.forename: Marco
authors.initials: M
authors.lastname: Vimercati
authors.forename: Andrea
authors.initials: A
authors.lastname: Grammatico
mesh_terms: D000368:Aged; D001919:Bradycardia / Q000401:mortality / Q000628:therapy; D017281:Cost of Illness; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D008297:Male; D010138:Pacemaker, Artificial; D012008:Recurrence; D018401:Sample Size; D013577:Syndrome; D013610:Tachycardia / Q000401:mortality / Q000628:therapy*