The story behind the problems with Riata electrophysiology leads made by St. Jude Medical has yet to be fully fleshed out, so it’s only natural that there is still a lot of uncertainty. Here are the top five questions I have.

Five: What is the role of the surgeon?

I have no idea what it takes to implant these things, but I haven’t seen data on lead fractures by center or implanting physician. We know doctors make mistakes, but how will the specialty societies respond if it turns out that skill and experience play a role? Leaving this question entirely to the specialty societies might be asking a bit much.

Four: What is the role of the patient?

I won’t argue it’s all on patient characteristics, but FDA’s Bill Maisel, MD, cites patient anatomy (along with surgeon skill and experience) in an editorial he co-authored in 2008. Maisel offers no details, but Ratika Parkash, MD, of Dalhousie University (Halifax, Canada) noted that “bony anatomy” may be associated with lead failure in a presentation to the 2012 Heart Rhythm Society annual meeting.

Parkash also observed at HRS 2012 that leads implanted in younger patients, more active patients, and patients with more robust ejection fractions may be more susceptible, which she said was the case with the Medtronic Sprint Fidelis.

What are a doctor’s options if the patient’s anatomy suggests a problem? Lead fracture versus sudden cardiac death? That’s a no-brainer, but it’s still not a great predicament.

Three: Which is better; single- or dual-coil leads?

According to Parkash’s data, single-coil leads are slightly less likely to require a revision than dual-coil leads, but Todd Cohen, MD, of Winthrop University Hospital (Mineola, New York), said at HRS 2012 that his data indicated no difference.

There may still be a debate among doctors whether a dual coil lead is necessary – an article in 2001 in EP Europace makes clear there was such a debate 11 years ago – but any such debate will find new life if dual-coil leads really are more susceptible.

Two: Does lead diameter really have anything to do with it? 

The numbers I’ve seen are all over the place. Cohen’s presentation at HRS 2012 included the remark that his study indicated “larger diameter leads tended to have better survival,” while Parkash said her data suggest the opposite.

I’ll wait for some sort of consensus statement, but one wonders whether there is some sort of interaction between lead diameter and materials, and between diameter and the single/dual-coil issue. The only reason I omit materials as a separate point is that there seems to be a consensus on little more than that silicone is out.

One: What about the role of bench and animal testing?

This could be sub-titled “the question of predictive science.” Do anatomical issues ever force a surgeon to insert a lead in such a way as to leave the lead kinked? That might be tough to replicate in the testing lab (and surgeon skill may be a factor in this scenario). Perhaps real-world use subjects a lead to torque that is difficult to replicate.

Does pre-clinical testing need beefing up? It’s tough to say because nobody talks about it, including FDA. I’m trying to line up an interview with the agency on this subject, and readers of Medical Device Daily should soon have a clearer picture of how pre-clinical testing has changed over the past decade or so.

There’s more to this than can be covered here, but one or more of these five factors may prove decisive in the Riata saga. Which will prove most decisive? Only time will tell.