Lariat-Small Step or Giant Leap?

Abstract

When Neil Armstrong spoke these now-famous words as he stepped off Apollo 11’s lunar excursion module and onto the moon on July 21, 1969, it was both a small physical step, like the many steps each of us takes every day, and a giant figurative leap formankind to walkonanotherworld for the first time. Similarly, the approval processes for medical devicessubject to reviewintheUnitedStates throughtheUSFood andDrugAdministration (FDA) can be characterized asmany “small steps” via the simple premarket notification, or 510(k) process, and relatively few “giant leaps” via the rigorous and expensive premarket approval (PMA) process. Overwhelmingly,most reviewablemedical devices are evaluated and approved by the far less-stringent 510(k) process because they represent either Class I (low risk) or Class II devices (intermediate risk, such as electrocardiographymachines).1 NewClass III devices (high risk, such as cardiac pacemakers) require approval through themuchmore stringent PMAprocess, which requires formal evaluation of safety and efficacy, often in the form of expensive randomized trials.2 If a Class III devices is “substantially equivalent” in function and use to an already approved device, submission of supplementary materials to an existing PMAmay suffice. As a practicing cardiac electrophysiologist, I am thankful that we have both the 510(k) and PMA processes for approving themyriadmedical devices I use every day in the process of providing heart rhythm care. And yet, when I consider the tools that I used inperforming invasive procedures thisweek, manyof themareClass II and III devices, and all of themwere approved by either the 510(k) process or by PMA supplement. The defibrillator I most recently implanted, for example, is many generations of capacitor and battery technology, processing power, and programming features beyond the original implantable defibrillators that underwent evaluation through the full PMA process years ago. Without these processes, manufacturers would be forced either to stifle innovation or to conduct new randomized trials for eachminor iteration, which would clearly be expensive, unwieldy, and in most cases, unnecessary. In this issue of JAMA Internal Medicine, Chatterjee and colleagues3 evaluate the safetyof theLariat suturedeliverydevicewith a systematic reviewof the literature and an analysis of events reported to the FDAManufacturer andUser Facility Device Experience (MAUDE) database. This device was approvedbyFDAasaClass IIdevicedescribed in theoriginal 2006 application under the 510(k) process as having the intended useof “sutureplacement andknot tying for use in surgical applicationswheresoft tissue [sic] arebeingapproximatedand/or ligated”with predicates of loop surgical ligationdevices used in abdominal surgery via laparoscopic tools and in endoscopic saphenousveinharvesting.4Approvalby theFDAof this 510(k) applicationwasbasedprimarily on the concept that the device represented an intermediate-risk product for the iterative “small step”of suture ligationof tissue similar toprior devices. Chatterjee and colleagues,3 however, found that the entire published literature andall the events reported toMAUDE were in associationwithuseof theLariat for left atrial appendageocclusion.3TheLariatprocedure involves transseptal catheterizationof the left atrial appendagevia the femoralveinwith a catheter that includes amagnetic tip. Simultaneously, a second catheter with a magnetic tip is placed in the epicardial space via a percutaneous epicardial access approach. The 2 catheters (endocardial and epicardial) are magnetically opposedwith the tip of the left atrial appendage between them, creating a rail over which the Lariat passes to the base of the appendage. The loop is then closed to ligate the left atrial appendageat its base.While thecompany’spatent5mentions the intendeduseof leftatrialappendageocclusion, theirFDA510(k) application does not.4 Occlusion of the left atrial appendage is, indeed, an intriguing potential target for stroke risk reduction in atrial fibrillation.Atrial fibrillationaffectsmillions in this country, and risk of stroke associatedwith atrial fibrillation (muchofwhich is due to left atrial appendage thrombus) is a very real problemthathashistoricallybeenaddressedwithwarfarinorother anticoagulant therapy in patients at risk. Oral anticoagulant therapy is burdensome and associated with bleeding risk, so aprocedural alternative (if safe andeffective)wouldbe attractive in at least some patients. Appendage ligation at the time of cardiac surgery is performed based on this plausible benefit, but I amnotawareof randomizeddatademonstrating that the practice reduces stroke risk.6 Other devices, such as the Watchmandevice (BostonScientificCorp)7 andAmplatzerCardiac Plug (AGA Medical Corp)8 are undergoing evaluation as newClass III devices for the intendeduse of stroke risk reduction by left atrial appendage occlusion, but unlike the Lariat procedure, which results in external loop ligation of the appendage at its base, the Watchman and Amplatzer procedures involve implantation of a self-expanding nitinol and polyethylene terephthalate or polyester device inside the appendage. Via the PMA process, the FDA considered the Watchman device after very promising results from the PROTECTAF(WatchmanLeftAtrialAppendageSystemforEmbolic PROTECTion in Patients With Atrial Fibrillation) trial,7 which demonstrated that the efficacy of the Watchman was not inferior to warfarin for the prevention of stroke in patients at high risk. The agency’s approval of the device, however, was delayed after subsequent follow-up data from the PREVAIL (Prospective Randomized Evaluation of theWatchmanLAAClosureDevice inPatientsWithAtrialFibrillationVerRelated article page 1104 Research Original Investigation Safety of Left Atrial Appendage ExclusionWith the Lariat Device