'Are We Downsizing in Vain?' Lead Size, Venous Occlusion Found Unrelated

May 18, 2012

May 18, 2012 (Boston, Massachusetts) — It may or may not be easier to thread a thin pacing or defibrillator lead, compared with a larger-caliber one, through the venous circulation even though that's a perceived advantage of thin leads. But another presumed advantage may simply be a fallacy: thinner leads aren't any less likely than thicker ones to cause venous occlusion, suggests an analysis presented here at the Heart Rhythm Society 2012 Scientific Sessions [1].

Speculating from those observations, Dr Michael C Giudici (Genesis Heart Institute, Davenport, IA) and his colleagues contend that when a vein with leads does occlude, it may have more to do individual patient physiologic responses to the presence of any lead rather than features of a particular lead.

Their analysis, presented under the heading, "Are we downsizing in vain?" found no significant relationships between venous occlusion in patients with pacemakers and defibrillators and how many leads were in the vein, composition of the lead insulation, or size of the lead.

That suggests the trend toward smaller-caliber leads in recent years has not benefited in causing less venous stenosis, Giudici told heartwire. But it may well have produced less sturdy leads more prone to fracture, exemplified by the recent high-profile Riata and Sprint Fidelis affairs.

Giudici's conjecture reflects the common perception of a link between thinner leads and increased rates of fracture and other structural lead failures that have led to the recent safety advisories and "recalls."

"Industry responded to competitive pressure to downsize leads, because implanting physicians were asking for that. They thought they were easier to implant," he said. "But downsizing has been causing problems by compromising the integrity of the leads. We never had these [frequent lead-fracture] issues before we had a lot of this downsizing."

Of 115 consecutive patients presenting over 16 months to one center for generator replacement, device upgrade, or lead revision a mean of seven years after original device implantation, 38 were found with total occlusion of the cephalic or subclavian vein containing the leads. All 38 were asymptomatic with good collateral venous flow, according to Giudici and his colleagues.

Another 52 patients had occlusions of 0% to 49% of venous lumen diameter, 17 had occlusions of 50% to 74%, and eight had 75% to 99% occlusions.

In addition to being unrelated to number of leads in the vein, lead insulation composition, and lead size, venous occlusion wasn't related to patient age, sex, or time since lead implantation.

"We have people who have four or five leads in and their vein's wide open, and other people who have one lead in and it's totally occluded," Giudici said. "It's a patient-specific thing, it's just how they react. It has nothing to do with the device."

Neither Giudici nor the coauthors had any disclosures.