identity » Thu Jun 22, 2017 7:54 pm wrote:evidence-based medicine
Any chance of some context on that one, because I really don't get it.
Why on Earth is evidence (studies, field trials etc.) a bad thing?
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identity » Thu Jun 22, 2017 7:54 pm wrote:evidence-based medicine
DrEvil » Fri Jun 23, 2017 8:40 am wrote:identity » Thu Jun 22, 2017 7:54 pm wrote:evidence-based medicine
Any chance of some context on that one, because I really don't get it.
Why on Earth is evidence (studies, field trials etc.) a bad thing?
What counts in a democracy is the experience of the citizens, i.e.,
their subjectivity and not what small gangs of autistic intellectuals
declare to be real.
—(philosopher of science) Paul Feyerabend
“Bloodlines are paths that allow oxygen-rich blood to saturate oxygenstarved
heart tissue. One laser can create bloodlines: the CO2 Heart
LaserTM.” Well, that’s what it says on the website of the company that
makes the laser, PLC Medical Systems, Inc.
“Transmyocardial laser revascularization” (TMR) is the latest whistle
in the surgical approach to angina. A company spokesperson told me that
they estimated they were approaching a total of 6,000 procedures worldwide
(in spring 2000), explaining that, after the procedure was covered
by Medicare, it quickly gained widespread acceptance as a treatment for
angina by the medical world (Floody 2000).
What kind of operation is this? In TMR, an incision is made in the
side of the chest between two ribs. The outer layer of the heart (the pericardium)
is removed, and the heart muscle (the myocardium) is exposed.
A laser (several different types are used) is touched to the surface of the
heart, and a laser beam is fired into the heart, presumably to make a channel
through the heart. Usually thirty to fifty such channels are made. The
idea is that this will make a sort of substitute artery, a “bloodline” in the
terms of one company, through which blood will flow providing oxygen-rich
blood directly to the heart muscle. The pericardium is replaced, and
the incision in the chest is closed.
Interestingly enough, the origins of this operation lie in some experiments
done in the 1960s where a doctor, making an analogy with the way
reptile hearts work (reptile hearts don’t get blood delivered via arteries,
but the blood simply suffuses from the ventricles into the heart muscle
itself through cavities called “sinusoids”), decided simply to make
such channels using acupuncture needles! Subsequently some other researchers
decided to try using lasers to do the same thing (for a clear
history of the procedure, see Kantor et al. 1999). By the mid-1990s, a
number of fairly large trials had been carried out. The procedure was
reserved for people who were not healthy enough to be treated by the
standard techniques (CABG, angiography), and who had very serious,
unstable end-stage angina – that is, for very sick people. The results
were quite remarkable: success rates were in the range of 75% to 90%.
“Success” was defined as very significant improvement in pain and functioning.
Angina is characterized in several ways; one uses the Canadian
Cardiovascular Society system which sorts angina into four classes. Successful
improvement in these studies required a two-stage improvement;
that’s a lot for such very sick people.
The problem is that no one really knows how or why this operation
“works.” The “bloodlines” close up in a matter of hours, and there is
no evidence that the myocardial blood flow actually increases by the best
type of evidence, perfusion imaging (Landolfo et al. 1999). The analogy
with the reptile heart simply doesn’t work; mammalian hearts just don’t
have the reptilian sinusoids. So what does happen? Some say that the laser
beams disrupt the nerves of the heart and denervate the affected areas
(Al-Sheikh et al. 1999), but others seem to show pretty conclusively that
this is not the case (Hirsch et al. 1999). There is some reason to believe
that the scarring process may lead to the creation of some new blood
vessels (“angiogenesis”), but there is no clear evidence that this has any
effect on angina.
So, what’s left? A number of people who have looked at the situation
suggest that, by analogy with the bilateral internal mammary artery ligation,
this may be due to the placebo effect (for example, Kantor et al.
1999; Lange and Hillis 1999). There are minimal improvements in the
objective measures of heart disease; but for patients, the most important
thing is not objective measures of anything, but whether or not they can
climb stairs, lift their grandchildren, or mow the lawn.
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