Dual Chamber Pacemakers

Abnormalities in AV conduction can contribute to a reduction in atrial contribution to ventricular filling and prolong the duration of mitral regurgitation into diastole. Restoration of these 2 hemodynamic phenomena provided the rationale for the potential benefits of AV synchronized pacing with optimal AV delay. Initial success showed a beneficial effect of cardiac pacing with a short AV delay in patients with HF.51 Subsequent acute52-54 and chronic studies55-60 assessing the effect of shortening the AV delay in patients with impaired ventricular function showed mixed results. Three well-designed and randomized studies failed to show any consistent improvements in HF with shortening of the programmed AV delay. Another concluded that for patients with standard indications for ICD therapy, no indication for cardiac pacing, and an LVEF of 40% or less, dual-chamber pacing offers no clinical advantage over ventricular backup pacing and may be detrimental by increasing the combined end point of death or hospitalization for HF.61