No Clinical Gain, More Risk: Preference for Dual- Vs Single-Chamber ICD Again Questioned

May 16, 2013

CHICAGO, IL — Dual-chamber implantable cardioverter defibrillators (ICDs) are more costly and demanding to implant than single-chamber devices and, it turns out, for primary prevention in patients without indications for pacing, pose a greater risk of complications, don't prolong survival, and aren't any better at keeping patients out of the hospital, concludes a study in the May 15, 2013 issue of the Journal of the American Medical Association[1].

Yet in the US, most ICDs implanted in such patients are dual-chamber devices, Dr Pamela N Peterson (University of Colorado, Denver) and colleagues concluded from data covering 2006–2009 gleaned from the ICD component of the National Cardiovascular Data Registry (NCDR-ICD) and Medicare claims.

Previous research has suggested that usage rates for dual-chamber ICDs compared with single-chamber devices also vary widely across the US and from center to center, with some hospitals avoiding dual-chamber devices entirely, others implanting them routinely, and most somewhere in between. Other investigators have demonstrated a correlation between an ICD's number of leads and complications, with risk climbing from single-chamber, to dual-chamber, to biventricular-pacing devices.

The current study complements a 2011 study, one with many of the same coauthors, that saw significant increases in both in-hospital mortality and complications with dual- vs single-chamber ICDs in an NCDR-ICD cohort with or without standard or biventricular pacing. That analysis, Peterson pointed out for heartwire , focused on short-term outcomes in a much broader ICD population.

"If somebody needs a dual-chamber device, if the [pacing] indication is there, even if there's a higher risk of complications, it makes more sense clinically if they get that type of device," according to Peterson. But without a pacing indication, she added, dual-chamber ICDs don't seem to have a clinical advantage to justify their significantly greater complication risk.

The group's analysis, which used propensity matching to help smooth out baseline differences between dual- and single-chamber ICD cohorts, showed statistically similar mortality and all-cause and heart-failure hospitalization one year after device implant. But complications were significantly more prevalent in the dual-chamber group (p<0.001), especially the need for ICD-system revision due to mechanical complications (p=0.001), report Peterson et al.

Outcomes of Patients With Single-Chamber vs Dual-Chamber in Propensity-Matched Cohorts In Peterson et al

End points Single-chamber, n=11 619 (%) Dual-chamber, n=11 619 (%) p
90-d complications      
Mechanical complications requiring system revision 1.43 1.98 0.001
Device-related infection 0.59 0.71 0.22
ICD replacement 0.73 0.77 0.70
Any complication 3.51 4.72 <0.001
1-y clinical outcomes      
All-cause mortality 9.85 9.77 0.83
All-cause hospitalization 43.86 44.83 0.97
Heart-failure hospitalization 14.73 15.38 0.16

Propensity matching accounted for 41 variables reflecting demographics, admission diagnosis, history of syncope and heart disease, revascularization, LVEF, individual comorbidities and conduction abnormalities, QRS duration, whether electrophysiologic testing had been performed, and measures of renal function

Some clinicians say dual-chamber ICDs are better than single-chamber devices at distinguishing ventricular from supraventricular arrhythmias by virtue of their atrial lead; and that, many say, is likely to cut the risk of inappropriate shocks. "If they're getting inappropriate shocks, and the dual-chamber device can reduce them, that would be beneficial," Peterson said. "But the data haven't shown that the dual-chamber device reduces inappropriate shocks any more than a single chamber device."

Peterson discloses support by a grant from the Agency for Healthcare Research and Quality. Disclosures for the coauthors are listed in the paper.

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