Until quite recently, implanted defibrillators (or implanted cardioverter defibrillator, I.C.D.), were not widely known among the general public. Oh sure, lots of people knew about pacemakers; they've been around for years. But, the idea of a miniaturized defibrillator put inside a person's body, that was the stuff of science fiction. However, ever since it was announced that Vice President Dick Cheney had one, public interest (and knowledge) has increased. And with good reason; the devices are credited with saving the lives of what medical science declares the sickest types of heart patients.

For many years, doctors were under the impression that patients suffering from heart disease died from a progressive failure of the organ. In lay terms, the heart just got tired and stopped pumping. In that kind of patient, an implanted defibrillator (I.C.D.) would not be a viable course of treatment. However, recent studies have found that the more usual cause of death was a sudden malfunction of the normal sinus rhythm of the heart. This situation is precisely what an I.C.D. is designed for. The device examines the electrical signals in the heart at regular intervals and watches for any signs of an irregular heartbeat. If detected, it acts within seconds to jolt the heart and return it a normal beat. As the mechanism is within the patient's body, it can, if necessary, give a more potent shock than an external defibrillator. Also, often times the device will have some sort of telemetry component that will record the patient's heart activity and download it to the doctor's office, thus enabling him/her to monitor the patient's progress.

Now, some people might say: "Whoa, wait, I've seen ‘E/R', I know what those things do to a person. I don't want to be lying in bed, watching TV and then – bam! I get jolted right out of bed when that thing zaps me." That is not the case. Since the shock is delivered directly to the heart, the physical manifestations are actually quite limited. Patients report feeling a slight tingle or, feeling weak and lethargic one moment, and literally energized the next.

It is clear that those patients in the poorest health get the most benefit from implanted defibrillators. Yet, one must also consider that patients with chronic heart disease, those with comparatively good heart function, are not helped by them. This fact needs to be kept in mind as the number of I.C.D.'s implanted is going up at a rate of greater than 20 percent each year.

A study carried out in 1996 examined 196 patients at various medical centers all over the country, all of whom had suffered a minimum of one heart attack before. The purpose of the study was to compare the life-saving features of the defibrillator to the severity of the patients' heart disease. Based on this study, it was found that high-risk patients benefited greatly from the implantation of an I.C.D. Now, over 150,000 people all over the world have an implanted defibrillator, and it's a certainty that they save lives. Its creation is the culmination of approximately twenty years of biomedical research.