Clinical decision making 301: The Sprint Fidelis ICD lead…

The implantable defibrillator (ICD) is an amazing life-saving device.  When used in the appropriate patient, the scientific data supporting its benefit is rock solid. The sudden death-averting appropriate ICD shock in the middle of the night, allows the patient to enjoy breakfast with his spouse, rather than admission to the morgue.

ICD function seems simple: sense the event, charge the capacitor and deliver the shock. However, transmission of all these electrons requires durable leads.  Leads that can withstand 100,000 heart beats per day as well as repetitive torsion from the chest musculature.

History:

Years ago, like many other “installers” of ICDs, I was a believer.  The new lead was lower profile (thinner), handled beautifully, and was easier to install.  It was even a pretty blue color. And, it emanated from a conservative and trusted Fortune 500 medical device company–the company that invented pacemakers.

Who knew the Sprint Fidelis lead would be such a disaster.  I wasn’t the only electrophysiologist duped, as more than 250,000 of these troublesome leads were implanted world-wide.

Compared with a non-recalled ICD lead, the Medtronic’s Sprint Fidelis ICD lead is highly prone to abrupt failure.  Lead failure, or an electrical short, is manifested as electrical noise.  Noise is transmitted to the sensing circuits of the device which results in two adverse outcomes.  First, electrical noise may inhibit pacing output. Pacing failure in a pacemaker dependent patient is nearly always a really bad thing. Secondly, and much more commonly seen in any ICD lead failure is electrical noise masquerading as ventricular fibrillation (VF).  Once VF is detected, the device charges and delivers therapy.

In the case of the Sprint Fidelis lead fracture, “delivers therapy” is medical speak for a wide awake patient receiving repeated 750 volt shocks.  This is a terrible outcome. For many patients inappropriate shocks are a life changer–for the worse.

On the surface, dealing with this issue seems easy: what’s your point, Doctor…Just take that terrible lead out, or put a new one in.  Fix it.

Here is the issue:  Statistics get in the way.

The Fidelis lead fracture rate is 2-3% per year, and fortunately, the death rate is even lower, at less than 0.5%.  Said in other words, for the patient with the recalled lead, each year brings an approximate 1 in 40 chance of sudden painful shocks.  A negative.

However, a recently reported multi-center survey showed that the complication rate from revising the recalled lead is significantly higher, approaching a 15% surgical risk, with half of these complications described as major. This seemingly high complication rate makes perfect sense, as the complication rate for simply replacing an ICD generator–in experienced centers–approaches 11 percent.

As is nearly always the case, I agree with the distinguished and level-headed professor, Dr Fred Morady who advises against prophylactic lead revision. (Dr Morady doesn’t know me, but many years ago, a colleague and I visited his lab as our first exposure to AF ablation, and I am grateful for his generosity.) His comments on this most recent Sprint Fidelis study are as follows…

The incidence of fracture of the Sprint Fidelis lead initially was estimated to be 1-1.5%/year, but the incidence has increased over time and now appears to be 2-3%/year. The most common clinical consequence of lead fracture is inappropriate shocks, and fortunately the risk of syncope or death resulting from lead failure has been very low (<0.1%). In light of the 15% complication rate associated with lead revision, the risk:benefit ratio of lead revision currently favors close observation of Sprint Fidelis leads that show no signs of malfunction.

Fortunately, the decision to operate on these leads is made easier by the fact that many Sprint Fidelis patients are approaching the 4-7 year lifespan of their ICD generators. Elective replacement of an ICD generator for battery depletion allows for an opportunity to revise the lead with less incremental risk.  I have not seen any “expert” statements yet, but it seems justified to revise the lead at the time of elective ICD generator change. It passes the, “it’s what I would have done for myself,” test.

Presentation to the patient…

This is far from easy.  ICD patients with recalled hardware are often a worried cohort. Wouldn’t you be?  I’d be a nut-job, for sure.  Just launching into the notion that your recalled device is fine now, but could go haywire at any moment isn’t even remotely straightforward.

As is often the case in medical practice, mathematically comprehensible population statistics prove difficult to apply to the individual patient who sits before you in the office. Obviously, the presentation of this challenging scenario varies depending on the patient.

It’s easy when it goes like this…

Me:  “You have a recalled wire…presently, your wire is OK…it might fail…if you get a shock, call 911…but for now it is more risky to operate on you, so we are just going to watch it closely.  Soon, your ICD will need changing because of a low battery…We will fix the wire then.”

Patient: “Ok, Doc, whatever you say, I trust you.”

In this case of unpredictable painful electrical shocks versus high surgical risk, trusting the doctor, and moving on with life, without the burden of the details seems better to me.

If it was my body with that fateful blue lead, I wonder whether I would make the right medical decision, or would I say, “I know it is riskier to operate, but I want it fixed?”

JMM