Saturday, December 09, 2006

Can 10 Cents Be Equal To 15,000 Dollars? A Case Against Open-Artery Hypothesis? Lest We Forget: Message From OAT Trial

Many acute heart attacks are caused by complete shut down of blood supply (due to blockage of a heart artery) to a part of the heart. The heart muscle without blood supply for more than a few minutes can be damaged permanently. Because of this, earliest possible reestablishment of blood flow by opening the closed heart artery is the centerpiece of management of heart attack victims. The time is of the essence in these cases. The prevailing literature seems to be quite clear thus far. It tends to get murky from here on.

What about a patient who does not really come with a heart attack but is found to have a closed artery that might have closed days, weeks, months or years back? There have been some non-randomized trials that suggest that a closed artery should be opened regardless of how long it has been closed. This is the basis for open-artery hypothesis. Simply put, open-artery hypothesis presumes that an open heart artery is better than a closed artery regardless of consideration for most other factors. In addition to some research supporting this hypothesis, it also appeals to our psyche. Broken glass needs fixing; a broken plane engine needs fixing; a broken door knob needs replacing, and a closed artery needs opening. The human body is a complex interplay of several dynamic intangibles (hormones, chemical reactions not visible to the naked eye and so hard to grasp sometime) that a glass, plane or door knob is not. So inductive reasoning may not apply to opening any closed artery.

A study published in December 7, 2006 issue of New England Journal of Medicine (NEJM) studied the benefits of opening a closed artery 3 to 28 days after a heart attack. This randomized study is named occluded artery trial (OAT).This study included the patients who had a heart attack due to a blocked artery, but that artery could not be opened within a few hours for some reason. This study showed that opening the closed artery more than several hours after heart attack not only did not help, but showed a trend toward hurting the patients. This study seems to question the open-artery hypothesis. Hillis and Lange, the authors of an accompanying editorial say that giving beta blockers could be as good as or better than opening a closed artery late after heart attack. Having researched this issue themselves, these authors speak from a position of authority. Increased risk of complications from an invasive stent procedure not withstanding, can a 10 cent beta blocker pill be as good as or better than a 15,000 dollar stent procedure?

After reading this article, I could not help but think of hormonal replacement for post- menopausal females. We had observed that risk of blockages of heart arteries in case of females was much higher after menopause. The obvious difference between pre and post-menopausal women is lack of hormones in post-menopausal women. So replacing those hormones should decrease chances of heart disease in post-menopausal women. It appealed to our psyche. It all made sense! The observational studies seemed to show what we expected. Then came a well-designed trial called HERS (Heart and Estrogen-Progestin Replacement Study) that studied the impact of hormones on heart disease in case of post-menopausal females. It showed that hormone replacement therapy might actually have harmful effects.

Could there be a parallel between hormone replacement therapy and open-artery hypothesis there?

OAT trial discussed above has sent an important message. From here on, we need to do more to test open-artery hypothesis aggressively. Proving it will validate our present position. Disproving it will not only save our patients numerous potentially harmful procedures, but will also save us much needed health care dollars.
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