October Meeting at JSUMC

The meeting began with Chapter Vice President Leonard Talalai reminding us of the Celebration of the Heart coming up on December 11, and asking that anyone with gifts to give away should give them to him to give away again as door prizes at the celebration. Chapter President Bill Ryan then introduced our speaker, Joseph P. Fay, of Medtronic Corporation. Joe spoke at the meeting at Riverview in July about implantable cardioverter-defibrilators - ICDs for short - and Bill thought it was worth repeating here.

As Joe said in July at Riverview, he deals with the electrical system of the heart, not the plumbing. When you get a bypass or a stent, that’s work on the plumbing that brings blood to the heart muscle. An ICD is there to help the electrical system that controls the heartbeat.

Not to repeat everything Joe said in July (which you can read about in the August newsletter - on the chapter website if you don’t have it), ICDs have come a long way since the 1980’s. They used to be so big they had to be implanted in the abdomen, it was major surgery to put them in and get the wires up to the heart, and the batteries lasted only about a year and a half. They were used only for patients who had already had two incidents of potentially fatal arrhythmia - ventricular fibrillation (uncoordinated twitching instead of pumping) or ventricular tachycardia (pumping too fast). Now they’re so small they can be implanted with minor surgery, they’re used for heart patients who are predisposed that kind of arrhythmia, and they last up to nine years before the battery runs down.

Joe told us we lose a thousand people a day to sudden cardiac arrest. With ICDs getting easier to implant and maintain, we want to get them to more people who are at risk. Recent studies say most heart failure patients who have had a heart attack and have ejection fraction below 35 percent should get one (an article on page 7 has more about ejection fraction).

An ICD, in case you were wondering, is a device that can be implanted in the chest. It consists of a small box - sometimes called the can - that contains a battery and some electronics, usually implanted under the skin below the collarbone, and one or more wires, called leads (rhymes with seeds), that are threaded through a vein to the heart.

If the heart is not pumping, it can deliver a shock to restart it - that’s called defibrillation. A less severe shock, to correct a runaway heart, is called cardioversion. If the heart is pumping too slowly, it can act as a pacemaker, giving an imperceptible kick to trigger each beat.

Depending on the patient’s needs, there could be just one lead down to the right ventricle, or two if the atrium also needs support - one to the ventricle and one to the right atrium. There are also three-lead systems that Joe described later.

The ICD is programmable. The system includes a device called a programmer, which is a laptop computer with a small device (like a computer mouse) that’s wired to it and can be held over the can to communicate with the can through the patient’s skin. Using the programmer, the doctor can tell the ICD how to decide when to shock, and the ICD can tell the doctor about every event, every heartbeat, since the last time it was interrogated. The ICD never forgets.

Battery life depends on how often the ICD has to shock the heart or act as a pacemaker, and the programmer can tell when the battery is low. At that point the whole can is replaced, not just the battery - it saves surgery time, there’s less risk of infection, and the technology has advanced in that time. But the leads are there to stay - they become embedded in the vein.

Joe discussed a problem Medtronic had last year that got some unfavorable publicity. Medtronic found that one type of leads they produced had a failure rate of about two percent instead of the usual half percent. Lead failure can be serious because the patient’s life may depend on the ICD. Medtronic corrected the problem, recalled the unused leads, and instructed doctors to program the ICDs to monitor the leads so that replacement leads could be put in if needed (without removing the old leads).

Medtronic and other companies have developed systems for remote monitoring. Instead of the patient having to go to the doctor’s office to use the programmer, the patient has a smaller box connected to the phone line, and the patient can put a mouse-like device over where the can is and push a start button. More recently there are boxes that can be placed by the patient’s bedside and the patient doesn’t have to do anything. Information from the ICD goes wirelessly to the device and through the phone line to a server site, which then sends information to the patient’s doctor. The bedside box also monitors itself and can report any problems with its own operation.

Joe described a technique called cardiac resynchronization therapy, or CRT. In some heart failure patients, the left and right ventricles don’t contract at the same time. As each ventricle contracts it pushes the septum (the wall between the ventricles) toward the opposite side, and less blood is pumped out. Connecting a third lead to the ICD enables it to pace the ventricles so they beat simultaneously and the ejection fraction is increased.

At the July meeting Joe described a new technique that Medtronic calls OptiVol. He gave us a more detailed explanation this time. Heart failure patients tend to accumulate fluid in the lungs (which is why the condition has been called “congestive heart failure,” or CHF). The increased fluid lowers the electrical resistance across the chest. An ICD can be designed to sense the resistance between the can and the other end of the lead and give early warning of accumulating fluid.

Somebody asked about getting an MRI when you have an ICD. The answer is no. There isn’t any danger of the magnetic field pulling the device out of your chest. But magnetic fields induce electric currents, and there’s a danger that stray currents in the leads could make the ICD operate improperly or even injure the heart. Medtronic is developing an ICD that they expect to be safe for MRI.

On a related topic: don’t go through the metal detectors at airports; ask for a special inspection without any electrical detectors. You can walk through the gates at stores that deter shoplifters, but don’t stand near them - patients have been known to pass out when their pacemakers stop working.

Thanks, Joe, for a very informative talk and some very knowledgeable answers to our questions.

Have a Happy and Healthy Thanksgiving!