In June 2001, Vice President Dick Cheney had a Medtronic (NYSE:MDT) defibrillator implanted at the George Washington University Hospital because of his severe heart disease. He had his first of four heart attacks at age 37. Then in 1988, he underwent quadruple bypass surgery, followed by angioplasty done in November 2000 and again in March 2001. The implantable cardioverter defibrillator, or ICD, sits in his upper chest and monitors the heart rhythm for potentially lethal fast beats that cause sudden cardiac death, or SCD. If this miracle of modern technology detects a life-threatening arrhythmia, it shocks his heart back into normal rhythm.

Although ICDs had been available for more than a decade, when Vice President Cheney received his, they were not routinely implanted in patients as a preventive measure. The vice president had not fainted or experienced a lengthy life-threatening heart rhythm -- common reasons for implanting an ICD -- before his procedure.

Studies published after 2001 showed the benefit of defibrillators in preventing sudden cardiac death in high-risk patients who have not had an arrhythmic event, so clearly there are good medical reasons for his receiving the device. In addition to Medtronic, three other companies -- Guidant, which is owned by Boston Scientific (NYSE:BSX); St. Jude Medical (NYSE:STJ), and Biotronik (privately owned) -- make these devices, which cost tens of thousands of dollars, require close monitoring, and need replacements every five years or so.

Did the ICD do Vice President Cheney any good? In other words, in the five years since it was implanted, has it ever detected a life-threatening rhythm, fired, and saved his life? Recall that he had no life-threatening rhythm problems in the 20-plus years between his first heart attack and when the ICD was implanted. Has the personal benefit for him exceeded the personal risk of surgery, the risk of worsening heart failure that some patients with defibrillators experience, and the risk of inappropriate shocks from the device?

There is absolutely no medical question that Vice President Cheney should have received the defibrillator. The point is that a large percentage of patients with them do not receive therapy from the devices. The major criterion used to decide whether or not to implant the device as a preventive move is a measurement of poor heart muscle function, not an electrical measurement.

Wouldn't it be great to have a simple, non-invasive test to better predict who would most benefit? Well, Cambridge Heart (OTC BB: CAMH.OB) has a special EKG machine that tests for microvolt T-wave alternans (MTWA), a tiny variation in the T-wave portion of the EKG. When a test is abnormal, the patient is at high risk for sudden cardiac death, and when the test is normal, the patient is at low risk. A study published in the January 2006 Journal of the American College of Cardiology by Dr. Daniel Bloomfield and others concluded: "Among patients with heart disease and LVEF < 0.40 [a measurement of poor heart pump function], MTWA can identify not only a high-risk group, but also a low-risk group unlikely to benefit from ICD prophylaxis."

Tests such as MTWA are only ordered if a payer will reimburse whoever performs it. Medicare, the world's biggest payer, made a national coverage decision to pay for the test this year if the test is done using the spectral analysis methodology, which is patented by Cambridge Health and creates a barrier to entry for other competitors. GE Medical, a part of GE (NYSE:GE), has a product that measures MTWA but does not use the spectral analysis method. The Medicare decision was huge for Cambridge Health, but if data from new studies compel Medicare to require a MTWA test prior to implanting the ICD for some patients, that would be gargantuan. Current cardiology guidelines do not urge doctors to check a MTWA test before implanting an ICD, but further research could change that.

For example, cardiologists await the results from a trial called The Alternans Before Cardioverter Defibrillator (ABCD) Trial: A Noninvasive Strategy for Primary Prevention of Sudden Cardiac Death Using T Wave Alternans, which are to be presented at the 2006 American Heart Association (AHA) Meeting on Nov. 15. Great results could be terrific for Cambridge Health, particularly it if showed that MTWA was a robust enough test to change clinical practice guidelines to mandate that MTWA be tested for in high-risk patients. Other clinical trials are nearing completion.

The stock has been a 10-bagger this year -- but the catch is that the stock was trading at $0.25 on Dec. 1, 2005, and is now at its five-year high. Another catch is that the company has issued lots of options and is poorly capitalized. Nonetheless, good news at the AHA meeting may be great news for millions of patients as well as for Cambridge Heart shareholders, particularly if guidelines were to subsequently change based on the results.

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Fool contributor Michael P. Cecil is a cardiologist and the author of Drugs for Less: The Complete Guide to Free and Discounted Prescription Drugs. Email him if you would like to discuss the article.The Fool has a disclosure policy, and the author does not own any of the stocks mentioned in the article.