Medical Device Daily Washington Editor

BOSTON – Cardiac rhythm management (CRM) devices are widely known to be one of the most promising businesses in the medical device industry, so much so that Dennis Zogbi projected in February that CRM hardware will sell to the tune of nearly $15 billion worldwide by 2010. Despite the promising numbers, the variety of devices designed to fix the faulty heart may have taken even the more jaded observers by surprise by now.

However, given all the diagnostic differentiation seen at gatherings such as Heart Rhythm 2006, perhaps the variety is not surprising after all. As an example, acquired atrioventricular sinus node block, as measured by the ankle-arm index (AAI) has generated a substantial number of papers over the past couple of decades, and it can generate a similar state of distress to humans as imposed by ventricular tachyarrhythmia.

The trick for device makers is engineering a device, such as a defibrillator, that can distinguish between these two events.

The scenario for ventricular tachyarrhythmias is fairly widely understood: several studies have sent the clear message that about 55% of defibrillator patients need help only with the atrium because the ventricle is essentially healthy and the atrioventricular sinus node is still passing the beat, so to speak, from the atrium to the ventricle. This slight majority of patients with no discernable ventricular tachyarrhythmias usually needs no help with ventricular function, but a defibrillator must nonetheless be able to provide ventricular stimulus when needed.

Several firms have generated algorithms to deal with this state of affairs, but the Sorin Group (Via Crescentino, Italy) has jumped into the fray with its AAISafeR software, putting the firm in direct competition with Medtronic (Minneapolis) and its Managed Ventricular Pacing (MVP) software.

Both these algorithms seek to cut down on unnecessary ventricular pacing, but Sorin bills AAISafeR as “the first pacing system capable of delivering safe and physiological single chamber therapy while collecting and analyzing dual chamber diagnostic information,” according to the firm's literature. Sorin's subsidiary, ELA Medical (Arvada, Colorado) packages its Ovatio series of defibrillators with the AAISafeR software and another algorithm, the PARAD+, which is designed to distinguish slow ventricular tachyarrhythmia and normal-rate ventricular tachyarrhythmia. ELA Medical has also packaged the AAISafeR into its Symphony line of pacemakers.

ELA came to Heart Rhythm 2006, the annual meeting of theHeart Rhythm Society (Washington), with something to celebrate. The firm snared a premarket approval from the FDA for the Ovatio, which includes single- and dual-chamber ICDs, on May 16, the day before the event commenced (Medical Device Daily, May 18, 2006). ELA touts the DR as consuming only 29 cc of space, giving it an advantage over bulkier units with patients in both comfort and cosmetic considerations.

Jonathan Sahu, MD, assistant professor of medicine at Rush Medical College (Chicago), told Medical Device Daily that AAISafeR keeps needless ventricular pacing to a range of .1 to .2%, but that Medtronic's MVP “has a ventricular pacing rate of about 4%.” Sahu said that Sorin's algorithm “is the best on the market” at present and can cover low ventricular tachycardias. “There is some evidence that we may be underestimating” SVTs, which devices with a high pace preset will tend to miss. However, he reassured that “it doesn't compromise the patient to set the pace at a low rate” in an effort to catch such events.

Sorin's literature claims that the AAISafeR program deploys four tests to keep track of AV block by using the right ventricular lead to provide enough data to keep track of any AV node block tendencies. The firm states that “79% of non-selected patients experience 0% right ventricular pacing with this algorithm.”