Tuesday, October 30, 2007

Defibrillator Lead Recalls: Industry and Clinical Implications

Medtronic’s most recent defibrillator lead recall will have profound implications (Wall Street Journal: subscription required) for the medical device industry as a whole:
"The events surrounding the Medtronic recall expose a hole in the U.S.’s medical safety system: Medical devices are regulated under different standards from those applied to prescription drugs. The Food and Drug Administration requires that almost all new medications be tested in human trials before they go on the market. But some devices, like the Sprint Fidelis leads, are subject to lighter guidelines because they are considered modifications of earlier products. The FDA, in most cases, also doesn't mandate major studies of medical devices after they've hit the market.

As a result, both the federal agency and the company were handicapped in evaluating whether a widespread public health threat was emerging.”
The broad market penetration of a these life-saving devices and the minimal safety data required for their approval, the FDA’s entire 510(k) device exemption and GMP (Good Manufacturing Practices) product development processes are now being reviewed. Even the smallest widget being developed that might be implanted in a patient and is sterilized (so-called Class II devices), be it cardiovascular, orthopedic, or otherwise, will be coming under ever-increasing scrutiny. This, in turn, will inevitably slow development and raise costs. What is clear now is that efforts to improve patient safety, already underway, will not be allowed to maintain the status quo.

But for those of us in this field, the defibrillator lead recall has even more far-reaching implications clinically. The recommendation of defibrillators for “primary prevention” of sudden arrhythmic death in those felt to be at high risk and whom have not yet had such an arrhythmia needs to be reviewed in light of these recent developments. (ed. comment: For lay readers, "Primary prevention" refers to patients who have not yet had an incidence or episode of a particular medical condition – in this case an abnormally rapid heart rhythm known as ventricular tachycardia (VT) or ventricular fibrillation (VF), often leading to sudden cardiac arrest (SCA) or sudden cardiac death (SCD). "Secondary prevention" refers to patients who have survived these conditions, and receive a particular therapy in response to the episode. Secondary prevention trials, such as AVID, CASH and CIDS, have shown a significant mortality benefit for patients who receive ICDs over those who receive just drug therapy.)

While there are excellent prospective, randomized data extolling the virtues of implanting implantable cardiac defibrillators (ICDs) in patients with markedly reduced ejection fractions (see the MADIT-II and SCD-HeFT data), these data were obtained with older device systems. (ed comment: Again, for the lay reader, the "ejection fraction" is the percentage of blood ejected from the heart with each beat - normal is over 50%) We are now left to wonder: should we be using older technology for our patients when recommending defibrillator implantation? After all, this is where we have the clinical data. Or do the newer advances of the more sophisticated devices (that might still be subject to later recalls but contain newer advanced features that we assume will provide better device oversight) warrant abandoning more conservative, evidenced-based medicine in the presumed interest of patient safety? Should new, expensive clinical trials be developed for these newer devices as well?

It is helpful to remember the raw data from the SCD-HeFT trial: there were 829 patients implanted with ICDs. Of those patients, 259 (31%) were shocked for ANY cause, and 177 (68% of those shocked) were shock appropriately for ventricular tachycardia or ventricular fibrillation. Therefore, the annual rate of shocks was 7.5% and the annual rate of appropriate shocks in these patients was 5.1%. Further, the number of deaths in the three arms studied were as follows: placebo (no therapy) 244 deaths, Amiodarone (medical therapy only) 240 deaths, ICD therapy 182 deaths. Would a faulty lead have changed the frequency of shock data? Certainly. Would it have changed the mortality data? Even if we added 5 deaths (as was potentially seen with the Sprint Fidelis lead) to the ICD arm of SCD-HeFT, it seems unlikely.

Nonetheless, given the recent recall, I suspect that we will see increased resistance by referring physicians to recommend these devices for primary prevention of arrhythmias. This is an inevitable outcome of such a massive recall, much like the later revelation of the propensity of stent thrombosis in drug-eluting stents. But like that scenario, there will still be appropriate patients in whom devices are warranted for primary prevention like those with markedly reduced left ventricular ejection fractions less than 25%. It’s just that the benefit for patients with higher ejection fractions in the 30-35% range may now be viewed more skeptically.


1 comment:

Anonymous said...

Dr Wes:

In light of this, what are you thoughts on MTWA screening to determine if a patient should get an ICD?



p.s. I really like your blog. I enjoyed reading your posts about your dad, earlier...was he a pilot?