New Toys for the Electricians

Electrophysiology is the subspecialty of cardiology that deals with the electrical problems of the heart.  At times the heart develops rhythms that break down into the fast rhythms, the slow rhythms and the lethal rhythms.  I have blogged in the past about the development of ICDs or implantable defibrillators and now we are seeing the next generation of these devices.

This paper was published online at the NEJM website and presented at the Heart Rhythm Society Meeting in May.  It was presented by Dr. Bardy who is the founder of the company as well as one of the inventers of the device.  Dr. Bardy  works at the Cleveland Clinic in Cleveland Ohio.

A conventional ICD is implanted by placing a wire into the right top chamber of the heart known as the atrium and a “shocking catheter” into the right lower chamber of the heart known as the ventricle.  There are other ways to do this but the descriptions are outside the scope of this blog.  To do this, the wires are in contact with the blood of the body and special equipment and x-ray is need.  This new device uses a generator that is implanted in the top part of the chest underneath the skin as in a standard ICD.  The new part is an array shocking catheter which is placed under the skin near the heart alongside the sternum.  It is not in actual contact with the heart and is not in the blood stream.

The procedure requires no x-ray and can be done in any suitable surgical location.  This device requires much more energy to work, almost twice as much, and the device is capable of delivering an astounding 80 joules of energy.  Most ICDs deliver shocks in the range of 18 joules.

The study encompassed 55 patients followed for a short 10 months.  One hundren and thirty seven bouts of induced rhythm were terminated.  Twelve episodes of spontaneous rhythms were successfully treated by the device.  For one patient the device would not successfully work in the lab and the patient received a standard ICD.  One patient died of renal failure unrelated to the study.

This is an exciting advance but not ready for prime time.  The device lacks many of the standard features of ICDs; perhaps the most important one is that of tiered therapy.  What is meant by that is that the device delivers therapy in many ways and often terminates the rhythm without delivering a full shock.  In addition the ICDs often function as backup pacemakers for patients.

Not quite ready, but an exciting advance and I applaud the thought leaders here. 

Next: A new device for atrial fibrillation…

Tags: Electrophysiology, Heart Rhythm, Heart Rhythm Society, ICD, implantable defibrillator
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More on Implantable Defribrillators

Despite all odds, no financial backing or grants, the three men mentioned in my previous blog developed the implantable defibrillator in Baltimore. After animal testing, the first device was implanted in a patient at Johns Hopkins Hospital by Dr. Levi Watkins, Jr. in February 1980. A patent was issued on May 13, 1980 entitled “Method and Apparatus for Monitoring Heart Activity, Detecting Abnormalities, and Cardioverting a Malfunctioning Heart.” The FDA approved the device in 1985 and it was commercialized in the late 1980s. Dr. Mirowski died in March 1990 at the age of 65 of multiple myeloma. He lived to see the device accepted with nearly 10,000 implants by then. He would not be surprised to find out that from 1990 to 2002 more than 416,000 implants were performed.

These devices have been the subject of numerous studies in an attempt to find the optimal patient selection and to avoid the burden that these devices do impose on patients. We are looking for the “sweet spot” — making sure that the right people get the devices and will benefit the most from them.

The early devices were shock only. Since then, all ICDs as they are now called provide pacing as well and the devices can provide various types of therapy in an attempt to terminate the rhythm and only shock as a last resort. Many patients can have their arrhythmias terminated by pacing or small shocks and these changes in therapy allow for longer battery life. These devices cost upwards of $50,000 and have other features’ that will be discussed in other blogs.

Dr. Luceri of this institution who sits on our Clinical Advisory Committee participated in the seminal trial documenting these devices value. The Sudden Cardiac Death in Heart Failure Trial also known as SCD-HeFT was published in the NEJM January 2005. Twenty-five years after the first ICD was implanted, this study proved once and for all that ICDs were superior to medical management and saved lives.

Dr. Mirowski’s insight and determination has saved hundred’s of thousands of patients. One person can make an enormous difference.

Tags: arrhythmias, Dr. Levi Watkins, ICDs, implantable defibrillator, Jr.
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