Wednesday, December 12, 2007

Newer Long-Term Cardiac Monitors

Today, Medtronic announced FDA approval of two implantable event recorders called the Reveal DX and Reveal XT, extentions of the earlier Reveal Plus implantable loop recorders (pictured). The Reveal DX continuously monitors the heart rhythm for up to three years, an extention of the Reveal Plus's approximately 14-month longevity, and adds additional heart rate monitoring zones classified as ventricular tachycardia or fast ventricular tachycardia zones. Information is "interrogated" via a specialized, proprietary Medtronic programmer. When patients have symptoms, they can use a hand-held device held over the Reveal implant site to "lock in" the event in the device's memory. (Other earlier-generation devices are discussed in a previous post).

The Reveal XT, monitors for atrial fibrillation episodes, too, but will not be first to market (unfortunately).

Each of the Reveal family of devices requires a minor surgical procedure for implantation that is typically performed as an outpatient procedure under local anesthesia. They have historically cost about $4000-6,000 each.

Medtronic's Reveal platform faces competition from Cardionet, a later-stage, non-invasive cardiac monitoring system dedicated to the detection of syncope and arrhythmic burden that requires no surgery.

With Cardionet, a special monitoring lead system sends the patient's heart rhythm via a bluetooth connection to a dedicated cellphone worn on the patient's waistband that transmits the patient's heart rhythm via cellphone to a central monitoring station (video available here). With the Cardionet system, patient's heart rhythms are monitored 24/7 and using physician-specified criteria, doctors are notified if a dangerous arrhythmia occurs without the need for patient notification. Each arrhythmia as well as heart rate and variability trends are upload to a web-based database system that can easily be evaluated by the physician on any standard computer using a secure internet connection.

In our clinical experience, the Cardionet system has detected asystole (no heart rhythm) while the patient was "sleeping" but noted to be "shaking in bed" by their spouse. The biggest problem for cardiologists prescribing these devices are the late nite calls: I was recently contacted at 2:30 AM for a four-beat run of ventricular tachycardia that terminated spontaneously after having just fallen asleep 30 minutes earlier from another (unrelated) call. Fortunately, I was able to reset the criteria for notifying the physician after speaking with the monitoring technician.

Cardionet's limitation is that it can only be used for up to 21 consecutive days. Each day of monitoring is billed separately to insurance carriers as needed. So if the dysrhythmia occurs infrequently (i.e., more than every three weeks) then longer-term monitoring, like Medtronic's Reveal platform, should be employed.


1 comment:

Kb said...

It looks like a flash drive. :)