Inhibition of Unnecessary RV Pacing With AV Search Hysteresis in ICDs - INTRINSIC RV


The goal of the trial was to evaluate dual- versus single-chamber pacing among patients implanted with an implantable cardioverter defibrillator (ICD) for standard indications.

Study Design

Patients Screened: 1,530
Patients Enrolled: 988
Mean Follow Up: 1 year
Mean Patient Age: Mean age 63 years
Female: 22

Patient Populations:

Standard indication for ICD implantation

Primary Endpoints:

All-cause mortality or heart failure hospitalization through 1 year, evaluated for noninferiority

Drug/Procedures Used:

Patients were implanted with a VITALITY AVT ICD that was programmed to dual-chamber rate-adaptive pacemaker (DDDR) mode. After one week, patients with right ventricular (RV) pacing <20% were randomized to continued programming of DDDR AV search hysteresis (AVSH) 60-130 (n = 502) or reprogramming to VVI-40 (n = 486).

Principal Findings:

At baseline, 67% of patients had coronary artery disease. Beta-blockers were used in 78% of patients, angiotensin-converting enzyme inhibitors in 64%, and diuretics in 50%.

The primary endpoint of death or heart failure hospitalization occurred in 6.4% of the DDDR AVSH group and 9.5% of the VVI-40 group, meeting the threshold for noninferiority. For superiority of DDDR AVSH, p = 0.072 and the risk ratio was 0.67. All-cause mortality also met the criteria for noninferiority (3.6% for DDDR AVSH vs. 5.1% for VVI-40 group, p < 0.001 for noninferiority, p = 0.23 for superiority). During follow-up, RV pacing in the DDDR AVSH group averaged 10%.


Among patients implanted with an ICD for standard indications, use of dual-chamber DDDR AVSH pacing was noninferior to single-chamber VVI-40 pacing for death or heart failure hospitalization at 1 year.

Results of the present trial differ from those of the DAVID trial, which showed treatment with dual-chamber pacing was associated with an increase in mortality or congestive heart failure hospitalizations by 1 year compared with ventricular backup pacing in patients with LV dysfunction and standard indications for ICD therapy, but not for pacing. There are several major differences between the trials, including pacing at a lower threshold in the present trial (60 bpm vs. 70 bpm in DAVID) and the patient population, which in INTRINSIC RV excluded patients with >20% RV pacing in the first week.


Presented by Brian Olshansky, MD, at the Heart Rhythm Society Annual Scientific Sessions, Boston, MA, May 2006.

Sullivan RM, Russo AM, Berg KC, et al. Arrhythmia rate distribution and tachyarrhythmia therapy in an ICD population: results from the INTRINSIC RV trial. Heart Rhythm. 2012 Mar;9(3):351-8.

Keywords: Odds Ratio, Coronary Artery Disease, Follow-Up Studies, Cardiac Pacing, Artificial, Diuretics, Heart Failure, Defibrillators, Implantable

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