June Meeting at JSUMC

Lunch had been announced, but lunch can’t be served at an evening meeting. We had fruit salad, chocolate-filled tarts, and a choice of beverage.

Our new chapter president, Matt Klug, wasn’t present to open the meeting, so Bill Ryan, the outgoing president, filled in. After noting that the chocolate-filled tarts were dark chocolate, and some were topped with nuts, both of which are good for you, and that the watermelon in the fruit salad was seedless, Bill introduced the speaker, Gustavo Rios from Medtronic, and the topic: pacemakers and defibrillators.

Gustavo told us his job was to make sure the devices implanted in patients are properly implanted and working properly, and to keep them working properly. A pacemaker, he explained, keeps your heart from going too slow (bradycardia); a defibrillator keeps it from going too fast (tachycardia).

A pacemaker watches your heartbeat, and if there’s a pause of more than one second before the next beat, it paces your heart, so as not to let your heartbeat go below 60 beats per minute. It’s implanted in your shoulder, and it has a battery and two wires, one to the atrium (at the top of the heart) and one to the ventricle (at the bottom of the heart).

Every defibrillator has a pacemaker, but not every pacemaker has a defibrillator. If a defibrillator detects a heartbeat going faster than 120 beats per minute, or 150, or 180, or whatever it’s set for, it will first try “pain-free”: it will try to pace you out of it. It will pace your heart a little faster than it’s going and then gradually slow down. If that doesn’t slow the heart down it will shock you.

Some pacemaker history: Back in the late 1800’s people found out that the heart worked with electrical impulses. In the early 1900’s people who needed a pacemaker had two needles through their skin into the chest connected to a big machine. They were bedridden; they couldn’t go anywhere. A power failure could be fatal.

Implantable pacemakers, he explained, were introduced in 1952. After some deaths at a children’s hospital in Minneapolis due to a power failure, Earl Bakken, a co-founder of Medtronic who had been maintaining the machines, produced a portable pacemaker that worked on batteries (see bottom illustration at right), with two knobs and one wire, that patients could walk around with.

Since then, pacemakers have become smaller and smarter. In 1961 a capsule was developed that contained the whole pacemaker and could be implanted completely inside the body. The first versions were too big to put in the chest so they were implanted in the abdomen. They had only one lead and they paced constantly at 60 beats per minute. If you were an athlete and needed a faster heartbeat you were out of luck. Pacemakers now have two leads, and they can tell when you’re active and will pace at a faster rate.

One concern of patients is how long the battery in the pacemaker will last. Battery life has gradually increased until a pacemaker can now last ten years. It’s checked every three months but it doesn’t have to be opened for seven to ten years. In the 1970’s there was a pacemaker that was powered by a nuclear isotope and could outlast the patients. It isn’t produced because of concerns about radiation and about nuclear proliferation.

Every heartbeat is two beats. First the atrium pumps blood into the ventricle, and then the ventricle pumps it into the arteries. Early pacemakers paced only the ventricle, but research showed that pacing the ventricle can be harmful unless you need it. Pacemakers now have separate leads, for the atrium and the ventricle. They can tell whether they need to pace only the atrium, or only the ventricle, or both, and will switch to whatever mode is needed.

A pacemaker also helps with diagnosis. The computer inside a pacemaker continually keeps notes, If your heart rate goes to 150 it can tell the doctor at what time on what day that happened. If you have atrial fibrillation it can tell the doctor exactly how often and for how long it occurs and can prescribe blood thinners appropriately; without a pacemaker, your doctor only knows that you have it. If you don’t have a pacemaker there is a small device called a loop recorder, that can be implanted over your heart through a tiny incision. It can keep a complete record of your heartbeat for as much as three years.

Implantable defibrillators came about in 1989. External defibrillators have been around longer, but they’re not always available and it takes time to set them up. If you’re in cardiac arrest, every minute of delay cuts ten percent off your chance of survival.

A defibrillator treats a condition called “sudden cardiac death.” The heartbeat is triggered by electrical impulses, and whatever comes fastest sets the pace. The heart has a natural pacemaker called the sinus node that sends out impulses at a rate that’s controlled by your autonomic nervous system. Scar tissue in your heart can cause a short circuit so that each impulse from the sinus node loops around and triggers more than one heartbeat.

Sudden cardiac arrest is not a stopped heart, because the sinus node keeps pacing it. Cardiac arrest occurs when the heart gets so many impulses that it can’t beat coherently and just quivers without moving any blood. Technically that quivering is called ventricular fibrillation. A defibrillator delivers a shock of up to 800 volts that stops the heart and gives it a chance to restart with a normal rhythm.

The first defibrillators were big machines that applied a shock through external pads. These machines have become smaller and more portable and now they’re provided in many public places to be used in case of emergency. Even smaller defibrillators are now implanted in patients who need them.

How do we know who needs a defibrillator? At first only people who had survived sudden cardiac arrest - twice - were eligible. Then you could get a defibrillator if it only happened once. The next step was to implant a defibrillator if there was proof of ventricular tachycardia or ventricular fibrillation. Now there are many conditions that justify implantation of a defibrillator, including scar tissue from a heart attack, ejection fraction under 35 percent, and Stage III heart failure.

Defibrillators have become smarter. They used to give a shock any time the heart rate went over 180 beats per minute. Now they can tell what caused the rapid heart rate. If it’s due to exercise, or if it’s coming from the top of the heart (supraventricular tachycardia), then it’s not life-threatening and there’s no need to shock.

Gustavo could have kept on going and going but we had other business to complete at the meeting. He did have one more thing to show us: a device that sits by your bedside, connects to your telephone line, receives wireless signals from the defibrillator, and calls the doctor if something goes wrong. We thanked him with a round of applause.

As the final order of business for the meeting, Bill Ryan stood up again to pass the mantle of the chapter presidency to Matt Klug, who had meanwhile arrived. First he gave Matt the Scranton PA chapter newsletter, which was being mailed to Bill and should now be mailed to Matt. Then he gave Matt a flash drive, containing the text of all the President’s Messages he ever wrote, and a book: All I Really Need to Know I Learned in Kindergarten. And then he declared Matt President.