Less can be more, they say. And it can be true in cardiovascular technology, it seems.

Reducing unnecessary pacing to the heart’s lower right chamber in patients with dual chamber pacemakers lowers the risk of developing atrial fibrillation (AF), according to a study funded by Medtronic (Minneapolis) and just published today in The New England Journal of Medicine.

The results showed that reducing pacing to the heart’s lower right chamber to less than 10% in dual chamber pacemaker patients lowered the relative risk of developing AF by 40% in a trial of more than 1,000 patients with sinus node disease (SND). SND is the most common reason for pacemaker implantation and is characterized by delayed or failed conduction between the sinus node and the atria, the heart’s upper chambers.

The Search AV Extension and Managed Ventricular Pacing for Promoting Atrioventricular Conduction (SAVE PACe) trial is the first study to demonstrate a clear superiority of newer forms of dual chamber pacing for sinus node disease versus older pacemaker technology.

Michael Sweeney, MD, the lead investigator of the SAVE PACe trial, told Medical Device Daily that the results of the study should have a “very significant impact on the public health issue of atrial fibrillation.”

The first device used in the trial was the Medtronic Kappa family of pacemakers, which was replaced with the newer EnRhythm pacing system with the Managed Ventricular Pacing feature, Sweeney said.

The trial’s objective was to demonstrate that dramatically reducing unnecessary right ventricular pacing could reduce the development of persistent atrial fibrillation. The study was developed in 2002, began enrolling patients in 2003, and was terminated in December 2006 after an interim analysis revealed that patients not using the newer forms of dual chamber pacing from Medtronic showed a 1.8 greater risk of developing persistent AF than those using them. This difference was highly statistically significant, the company noted.

Sweeney, an associate professor of medicine at Harvard Medical School (Boston) and an electrophysiologist at Brigham and Women’s Hospital (Boston), said that the outcome of the study was not a surprise but that it was interesting to see how broadly applicable it can be among SND patients who receive pacemakers.

“The reduction of relative risk of atrial fibrillation was observed across all clinically relevant population subgroups ... every group of patients that we could parcel out within the study population had this benefit,” Sweeney said.

AF, an electrical malfunction of the upper chambers of the heart that produces irregular heartbeats, is the most common side effect of pacemakers and can lead to further complications such as stroke or death.

“Atrial fibrillation is a huge public health program ... the vast majority of patients who receive a pacemaker for sinus node disease experience atrial fibrillation upon follow-up ... it absolutely dominates the care and management of these patients,” Sweeney said.

After an average of 1.7 years in the study, 68 patients who received conventional dual chamber pacing developed persistent atrial fibrillation (12.7%), compared with 42 patients (7.9%) who received dual chamber minimal ventricular pacing, which minimizes unnecessary pacing to the right ventricle of the heart. Mortality was similar in the two patient groups, but heart failure hospitalizations were more than 50% lower for the group of patients with dual chamber minimal ventricular pacing (3.2% vs. 7.3% for those who received conventional dual chamber pacing).

“It’s important because it targets atrial fibrillation and the overlap with need for pacemaker therapy,” Sweeney said.

He told MDD that there is a fair amount of retrospective evidence linking ventricular pacing with AF, however the SAVE PACe trial is unique because it is the first study that validates the concept on a larger scale.

He said about 100 centers in the U.S. and Canada participated in the trial.

Sweeney said that Boston Scientific (Natick, Massachusetts) and St. Jude (St. Paul, Minnesota) also make pacemakers with features intended to allow doctors to minimize ventricular pacing as well.

“However, they either have not published evidence that they can deliver on that promise, or the evidence they have published is inferior by comparison,” Sweeney said.

Because of a lack of understanding, Sweeney said many pacemakers on the market already have these features but that the technology is not being exploited to achieve the goal of reducing the risk of AF.

“It clearly demonstrates that pacemakers, just like pharmacologic therapy, in addition to being effective for their intended goal, can have side effects,” Sweeney said.

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