Inhibition of Unnecessary RV Pacing with AV Search Hysteresis in ICDs (INTRINSIC RV):

Abstract

Implantable cardioverter defibrillators (ICDs) reduce sudden arrhythmic death risk but when these devices are programmed DDD and pace in the right ventricle (RV), they can be associated with increased mortality and heart failure morbidity compared to an ICD programmed to back-up RV. An ideal ICD would provide effective treatment for life-threatening tachyarrhythmias, reduce unnecessary RV pacing and maintain AV synchrony. The Inhibition of Unnecessary RV Pacing with AV Search Hysteresis (AVSH) in ICDs (INTRINSIC RV) study will assess whether an ICD programmed to DDDR with AVSH is equal to an ICD programmed to VVI with regard to mortality, heart failure hospitalizations, and several predefined secondary enpoints. AVSH allows intrinsic AV conduction beyond the programmed AV delay to help minimize ventricular pacing. INTRINSIC RV, a multi-center, randomized, prospective trial will enroll >1,200 participants who receive a Guidant VITALITY AVT ICD. ICDs are programmed initially to DDDR AVSH 60-130. Then, after a week, if the %RV pacing <20%, patients are randomized to VVI-40 or DDDR 60-130 with AVSH. Those with RV pacing > or =20% are placed in an obvservational arm and programmed ad libitum by the treating physician. Patients are followed for one year. This large, randomized, controlled, clinical trial will address whether DDDR with AVSH programming is equivalent to VVI programming in an ICD with regard to mortality and heart failure hospitalization.

Reduction of Right Ventricular Pacing in Patients with Dual‐Chamber ICDs

“…Inhibition of Unnecessary RV Pacing with AV Search Hysteresis in ICDs (INTRINSIC RV) is a prospective, multicenter, randomized trial that compares clinical outcomes among ICD recipients with VVI programming versus DDDR programming with AVSH 9 . A composite endpoint of mortality and hospitalization for heart failure is the primary endpoint.…”

“…All patients with an ICD indication were included in this trial. Other inclusion and exclusion criteria were described previously 9 …”

“…Ideally, an ICD would be able to sense activity in both the atria and the ventricles and provide a broad range of treatments for ventricular and atrial arrhythmias without unnecessary RV pacing. Most dual‐chamber ICDs contain algorithms designed to encourage intrinsic conduction and decrease the percentage of RV pacing 9,10 through automatic adjustment of AV delays. The AV Search Hysteresis (AVSH) algorithm (Guidant Corporation, St. Paul, MN, USA) actively searches for the presence of intrinsic AV conduction by extending the AV delay to a preprogrammed percentage to reduce unnecessary RV pacing 11 …”

Cardiovascular Outcomes With Atrial-Based Pacing Compared With Ventricular Pacing

“…21 As in MOST, dual-chamber pacing resulted in a higher frequency of right ventricular pacing (60% versus 3%) and was associated with an increased risk of death or heart failure hospitalization (26.7% versus 16.1%). 21 New modes of dual-chamber pacing have been developed to minimize right ventricular pacing, 24 and ongoing research will determine whether they improve clinical outcomes in patients with sinus node dysfunction. Another option to avoid unnecessary ventricular pacing in patients with normal atrioventricular conduction is to use single-chamber atrial pacing.…”

Physiologic Pacing: New Modalities and Pacing Sites

“…Second, ventricular pacing is often not significantly reduced especially at high pacing rates associated with rate‐responsive systems. Many modern dual chamber pacemakers contain an “AV hysteresis” function that can reduce ventricular pacing by transiently increasing the AV delay in an attempt to “search” for intrinsic conduction 19,20 . One trial showed a significant reduction of percentage ventricular pacing in patients with a pacing indication and intact AV nodal conduction (70 ± 40% vs 19 ± 28%, P < 0.001) 20 .…”