title: Prospective randomized study of mode switching in a clinical trial of pacemaker therapy for sinus node dysfunction.
abstract: BACKGROUND
  Atrial fibrillation (AF) is common in pacemaker patients with sinus node dysfunction (SND) and may result in rapid ventricular pacing (RVP) in the DDDR mode. Mode switching (MS) reduces RVP, but its clinical benefit in patients with SND is unknown.
  
  
  RESULTS
  Two hundred two patients in the Mode Selection Trial (MOST; 2,010-patient, 6-year trial of DDDR vs VVIR pacing in SND) randomized to DDDR pacemakers with atrial high-rate episode (AHRE) storage capabilities were subrandomized to MS ON (N = 96) or MS OFF (N = 106). Cardiovascular symptoms, quality of life (QOL), reprogramming due to RVP, death, stroke, and heart failure hospitalization (HFH) were compared between groups. The treatment groups were similar with regard to AF history (59% MS ON vs 57% MS OFF). AHREs occurred in 49% patients during median follow-up of 2.2 years. Median AHRE duration (in min; MS ON 116 vs MS OFF 58, P = 0.29), frequency AHREs/week (MS ON 3.5 vs MS OFF 6.4, P = 0.23), and time spent in AHRE (min/week) (MS ON 450, MS OFF 268) were similar. Reprogramming due to any RVP during AHREs occurred more in MS OFF vs MS ON (13.2% vs 3.1%, P = 0.011) and marginally more for symptomatic RVP (8.5% vs 2.1%, P = 0.062). Cardiovascular symptoms occurred in 93.6% MS ON vs 90.2% MS OFF (P = 0.38). Median number of symptoms reported per visit was similar (MS ON 1.3 vs MS OFF 1.5, P = 0.62). Median symptom frequency/severity, summed and averaged over visits, was similar (MS ON 4.3 vs MS OFF 4.5, P = 0.74). QOL was not different between groups. Death, stroke, and HFH were not different between groups.
  
  
  CONCLUSIONS
  MS reduces pacemaker reprogramming due to RVP during AHREs in a small number of patients but does not improve QOL or cardiovascular symptoms overall among patients with SND.
authors.affiliation: Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA. mosweeney@partners.org
authors.forename: Michael O
authors.initials: MO
authors.lastname: Sweeney
authors.forename: Anne S
authors.initials: AS
authors.lastname: Hellkamp
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Ellenbogen
authors.forename: Taya V
authors.initials: TV
authors.lastname: Glotzer
authors.forename: Russell
authors.initials: R
authors.lastname: Silverman
authors.forename: Raymond
authors.initials: R
authors.lastname: Yee
authors.forename: Kerry L
authors.initials: KL
authors.lastname: Lee
authors.forename: Gervasio A
authors.initials: GA
authors.lastname: Lamas
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001283:Atrioventricular Node / Q000473:pathology / Q000601:surgery; D023381:Endpoint Determination; D004867:Equipment Design; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D010138:Pacemaker, Artificial; D011183:Postoperative Complications / Q000209:etiology; D011446:Prospective Studies; D011788:Quality of Life; D012720:Severity of Illness Index; D012804:Sick Sinus Syndrome / Q000628:therapy*; D018434:Sickness Impact Profile; D016037:Single-Blind Method; D016896:Treatment Outcome