Wednesday, April 21, 2010

Remote Monitoring and Preventing Unnecessary ICD Shocks

In 2009 there was an interesting editorial written by Joseph E. Marine from Johns Hopkins University School of Medicine, published in the journal, Europace (European Society of Cardiology).  The title of the editorial was "Remote monitoring for prevention of inappropriate implantable cardioverter
defibrillator shocks: is there no place like home?
The entire article can be found at the following location:
For those of you unfamiliar with ICD's (implantable cardioverter
defibrillator), the ICD delivers a relatively high-voltage shock to the heart when conditions indicate that the heart may be about to go ventricle fibrillation (a rapid irregular heartbeat that will likely lead to death) or that the heart ceases beating.  The latter condition is easily detected, however, determining the former condition is more difficult.  Because the conditions are not always clear, ICD (and a companion system, the CRT-D) too frequently deliver shocks unnecessarily. (I have discussed issues related to detection in other articles in the blog.  Here are the links to those discussions:,  Another reason that an ICD might deliver unnecessary shocks would be because of sensor lead failure or near failure. 

Joseph Marine examined the value of remote monitoring to the prevention of unnecessary shocks.  He concluded that remote monitoring was particularly suited to providing early detection of failing sensor leads.  However, ...
[f]inally, most inappropriate ICD shocks are not caused by
lead failure, but rather by supraventricular arrhythmias, and this
study does not provide any evidence that home monitoring
reduces risk of inappropriate shocks from this cause.
In other words, remote monitoring could not aid with improving the false positive rate - the delivery of unnecessary shocks.

To those who have not been involved with ICDs, it may seem that the delivery of an unnecessary may not be so bad given the alternative, that a failure to deliver a shock will likely lead to the patient's death.  And there are many cardiologists who will argue the case for a "hair-trigger" system - acceptance of false positives, but no acceptance of false negative: that is a failure to deliver a shock when conditions warrant.

However, unnecessary shocks will do damage over time.  Furthermore, those patients who have received a shock describe it as feeling like "... a mule kicked" them in the chest.  I know of situations where patients who a received shocks eventually have the ICD removed

So, I want to make the case to the medical device industry that remote monitoring may be the key to solving the false positive problem.  In that the data that remote monitoring systems collect and transmit may lead to better detection and discrimination.  In addition with reference to my article on prediction, remote monitoring may enable physicians to tune ICDs based on specific predecessor events that could enable remotely adjusting the parameters on the ICD to allow better targeting.

I'm not an expert in this area.  However, I know enough about indicator conditions in other areas that can be used to adjust systems and improve their accuracy.

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