Once a major procedure, ICD implantation now takes only two to three hours.
Ventricular fibrillation is the irregular contraction of the heart's lower chambers. This erratic rhythm prevents the heart from pumping blood to the body. Its most common cause is myocardial infarction, or heart attack, and death follows soon after if no action is taken. Before the invention of the implantable cardioverter defibrillator (ICD), more than 40 percent of those suffering ventricular fibrillation died. After it's invention, that rate decreased to two percent.
The Electric Beginning
Defibrillation administers electricity to the heart to shock it back into normal rhythm. The discovery of this characteristic of electricity was somewhat accidental. In the early 1900's, while investigating electrocution deaths after General Electric switched from direct current (dc) to alternating current (ac), electrical engineering professors at Johns Hopkins University in Maryland used ac shocks to kill stray dogs. In the process, they observed that a second shock could bring the dead dog back to life.
Early Days
Claude Beck, a cardiac surgeon at University Hospitals of Cleveland, continued animal experimentation, using ac electricity directly on the open hearts of animals he had put into ventricular fibrillation. When, by chance, in 1947, a 14-year-old boy's heart stopped during surgery, Beck called for his research tools to be brought into the operating room. After two shocks, using metal spoons with wooden handles as paddles to deliver the electricity, he succeeded in restarting the boy's heart. Scientists in Europe and the Soviet Union continued to refine the process, using dc defibrillation, then a biphasic waveform (a larger positive shock followed by a smaller negative one).
Michel Mirowski
In 1966, when a friend and mentor of Israeli cardiologist Michel Mirowski died from ventricular fibrillation, the seeds of invention were sown in grief. Why wasn't there a way to prevent this malignant fibrillation, or a way to convert it to normal rhythm when it happened? Implantable pacemakers had recently become available; Mirowski wanted to make a defibrillator also small enough to be implanted into the body so that a person could be shocked out of ventricular fibrillation without having to be in a hospital. The medical community scoffed at the idea. After all, the machines used in hospitals weighed 30 to 40 pounds, used large paddles to deliver the jolts and took two people to operate.
Success
Unable to accomplish the task he set for himself in Israel, Mirowski emigrated to the United States and in 1969 began working at Johns Hopkins University with Dr. Morton Mower. Their work met with skepticism from all corners. Nevertheless, Mirowski and Mower continued their research and in the mid-1970's a series of long-term tests of the device in dogs showed its viability. In 1980, following extensive investigation and review, the first defibrillator was implanted into a human. Soon the bulky paddles of early defibrillators were gone, replaced by adhesive pads, and a modern biphasic waveform required less power, allowing the defibrillator's components to become smaller.
Vindication
In 1985, after 800 human implantations, the device was approved by the Food and Drug Administration, and by 1990, when Mirowski died, his implantable cardioverter defibrillator had saved the lives of 10,000 people. Today, the ICD is a fraction of its 1980's size. Despite this, it lasts longer and does much more. It has prolonged the lives of hundreds of thousands of people with irregular heart rhythms, a great many of whom would surely have suffered sudden cardiac death without it.
Tags: ventricular fibrillation, biphasic waveform, cardioverter defibrillator, Hopkins University, implantable cardioverter, implantable cardioverter defibrillator, implanted into