Medical Device Daily Washington Editor
BOSTON – It is commonly understood that as Americans – and other Western nations with a cohort similar to the U.S. Baby Boom – grow older and more overweight, so will the prevalence of heart disease of various types and origins. Thus it may have come as no surprise to many when the FDA stated in its September 2005 report on ICD and pacemaker malfunctions that the annual number of ICDs implanted in the U.S. “increased from fewer than 10,000 implants in 1990 to close to 100,000 in 2002.”
However, the medical systems in other Western nations are apparently not quite as aggressive in making use of ICDs. According to a Heart Rhythm 2006 presentation by Wyn Davies, a consulting cardiologist at St. Mary's Hospital (London), the rate of ICD implantation in the U.S. exceeds that of the UK by a factor of 10. Another attendee at Heart Rhythm 2006 discussing the subject off the record put the multiplier at a more conservative factor of five, which is still a stark contrast if one assumes that there is no proportional difference in the health status of these two nations.
As a point of comparison, the National Heart, Lung and Blood Institute at the National Institutes of Health (Bethesda, Maryland) estimates that about 1 million Americans suffer heart attacks yearly. Given an estimated current U.S. population of about 298.4 million, the prevalence of heart attacks is about 3.4%. The population of the UK will be about 60.6 million in July 2006, and the UK Department of Health estimates that “275,000 people have a heart attack annually.” This yields a rate of about 4.2%.
Assuming that the rates of infarction roughly parallel those of sudden cardiac death due to rhythm problems, it would seem that a huge disparity exists between the U.S. and the UK in terms of ICD use, especially given that infarction is a more common diagnosis in the UK. If the rates of other heart diseases track those of infarction in both nations, this apparent disparity in the use of ICDs widens.
Regardless of how these numbers actually tumble out, one thing seems incontrovertible: Americans get ICDs at a far greater rate than their counterparts in other Western nations. It might be pertinent to ask whether cardiac arrhythmias are overtreated in the U.S. or undertreated in the UK.
It should be noted up front that many ICDs are installed as a preventive measure for high-risk patients with no history of fibrillation or flutter. Precisely what percentage of ICDs are installed on this basis may be impossible to determine if only because different doctors employ different standards to define such an event. If prophylaxis is not a standard of care in the UK, much of this disparity disappears. The Center for Medicare & Medicaid Services (CMS; Baltimore) approved ICD coverage for preventive use in 2005.
So it should be noted that attendance at an event populated by electrophysiologists leaves no doubt that prophylaxis is a very compelling notion for American doctors. On the other hand, the recent disclosure that antibiotics are, or at least were, overprescribed in the U.S. makes it very difficult indeed to avoid the suspicion that ICDs are overused in the U.S.
One of the filtering mechanisms that electrophysiologists use to undergird the decision whether to recommend ICD implantation is that of risk analysis, but this paradigm is, predictably, also the subject of some controversy. One of the debate sessions at Heart Rhythm 2006 was on this very topic.
In that debate, which was one of many at the '06 edition of Heart Rhythm, Greg Flaker, MD, the director of the electrophysiology lab at the University of Missouri Hospital and Clinic (Columbia) argued that risk analysis creates serious ethical quandaries, whereas Arthur Moss, MD, professor of medicine at the University of Rochester Medical Center (Rochester, New York), argued the opposite, that risk analysis still has a place in care decisions.
Flaker's arguments hinged largely on the ethics of denying ICDs to individual patients from subgroups whose members “swim against the data” whereas Moss made his case from a systemic standpoint, including the assertion that patients with two or more risk factors experienced a mortality rate of 45% over a three-year span. Moss based his numbers on the MADIT II (Multicenter Automatic Defibrillator Implantation II) trial.
Anne Curtis, MD, president of the Heart Rhythm Society (Washington) and the chief of cardiology at the University of South Florida (Tampa), shed some light on this subject.
When asked if ICDs are implanted more often than is necessary, Curtis told Medical Device Daily that “I would not agree with that. You could argue that we're not implanting enough in the United States” due to the difficulty in establishing which patients are really at risk of sudden cardiac death. Curtis confirmed that prophylactic use is not common in the UK, but nonetheless insisted that “implant rates are still well below” that which could be used to substantial benefit to American patients.
“There are a lot of tools” for risk stratification, Curtis remarked, but they are not powerful enough to enable the kind of distinction that would eliminate installation in patients who are at low or zero risk. She commented that T-wave alternans may prove a more viable risk determination tool than any currently available, but as things stand, doctors simply do not have a tool that lays out risk in an unambiguous fashion.
T-wave alternans is a variation in the t-wave, a relatively inconspicuous feature of heartbeat. However, patient heartbeats must be forced to more than 100 beats per minute to test this phenomenon and the clinical trial data on t-waves is not yet sufficient to establish their predictive power for risk analysis purposes. CMS now pays for, but does not require, t-wave analysis for ICD candidates (Medical Device Daily, March 16, 2006).
Curtis also pointed out that only 5% of those who experience sudden cardiac death are revived. She asked “what is our tolerance” for not implanting someone who seems to have no risk but who later has an event?