Prior research with pacing therapy : Around 1990 there were early published reports about the benefits of dual-chamber pacing with a shortened atrioventricular (AV) delay.2-4 "The studies found that CHF patients improved significantly with a 'superphysiologic’ AV delay of about 100 ms," said Dr. Saxon. "This sparked a lot of enthusiasm. However, subsequent studies have not been able to replicate the early results, except in one subgroup – patients who have a marked delay in their AV nodal conduction, and thus have long baseline PR intervals. In these patients, the ventricular contraction is delayed, leading to inadequate filling and mitral valve regurgitation. A pacemaker with a shorter AV delay can help solve this problem. A consensus is now emerging that while reducing the AV delay can help patients in this one small niche group, it’s not a therapy that can be applied broadly. However, these studies were among the first to show that pacing could be used to treat a segment of CHF patients who had no traditional bradycardia indications."
She added that decreasing the AV delay has the potential to help more CHF patients, but the AV delay must be tailored to the patient. "If a physician is willing to spend the time and order sophisticated tests to help pinpoint a patient’s optimal AV delay, there will usually be some benefit – sometimes incremental, sometimes dramatic. But this strategy is certainly not widely applicable to CHF patients." (guidant.com)