Clinical Studies and Outcomes


Danish II

A randomized comparison of atrial and dual-chamber pacing in 177 consecutive patients with sick sinus syndrome: echocardiographic and clinical outcome.

Nielsen JC, Kristensen L, Andersen HR, Mortensen PT, Pedersen OL, Pedersen AK. JACC. 2003;42(4):614-623

Design: 177 consecutive patients with sick sinus syndrome (SSS) randomized to pacing treatment in AAIR or DDDR with a short AV delay (DDDR-S) or DDDR with a fixed long AV delay (DDDR-I).
Objectives: Compare AAI and DDD pacing in patients with SSS, as measured by echocardiography.
Key Results: Mean Follow-up – 2.9 ± 1.1 years:

  • In both DDDR groups, LA diameter increased significantly (P < 0.05)
  • In the DDDR-S group, LV fractional shortening decreased significantly (p < 0.01)
  • Atrial fibrillation (AF) was significantly less common in the AAIR group (7.4% vs. 17.5% in DDDR-I group and 23.3% in DDDR-S group, p = 0.03, log rank test)
  • In the AAIR group, no significant changes were observed in LA or LV diameters

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MOde Selection Trial

Adverse effect of ventricular pacing on heart failure and atrial fibrillation among patients with normal baseline QRS duration in a clinical trial of pacemaker therapy for sinus node dysfunction

Sweeney MO, Hellkamp AS, Ellenbogen KA, et al, for the MOde Selection Trial (MOST) Investigators. 

Circulation. 2003;107:2932-2937.

1,339 patients from the Mode Selection Trial (MOST), a 6-year, prospective, randomized study, received either dual-chamber pacing (DDDR) or single-chamber ventricular pacing (VVIR) in sinus node dysfunction (SND). Ventricular desynchronization, imposed by ventricular pacing even when AV synchrony was preserved, increased the risk of heart failure hospitalization and atrial fibrillation in SND with normal baseline QRSd.

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