22. Summary: A
Thought Experiment
How can this be? How can a week of atenolol reduce
two year mortality? Let's do a thought experiment. Suppose we
take 200 people with really, really, bad coronary artery disease.
It is a thought experiment, so I can get the sickest patients
I want, enrollment is easy, consent is easy, and the paper work
is minimal. We randomized the patients into two groups. 100 patients
are sent to military boot camp: Twenty-four hours a day of exercise,
stress, pain, tachycardia, poor or no sleep, etc. The other group
of 100 patients gets catered meals in a hotel with a comfortable
chair, TV, and pampering. What is going to happen?
Well, some of the people in the boot camp group
are going to die from the forced exercise. Of the people who don't
die, there is going to be episodes of myocardial ischemia, that
ischemia is going to crack intracoronary plaque. Coronary ischemia
damages the coronary endothelium. Once it is damaged, activated
platelets cause vasoconstriction. In normal coronaries, activated
platelets cause vasodilation, but in ischemia damaged coronaries,
activated platelets cause vasoconstriction. So, ischemia begets
more ischemia, begets infarction, which may lead to death. The
stress leads to ischemia, which leads to infarction, which leads
to death. Those deaths may occur during the forced exertion or
in the next few weeks to months. The week of stress has set a
chain of events going that leads to cardiac morbidity and mortality.
What about the people in the comfy chair group?
Well, we never stressed them. We never started the vicious cycle.
They just enjoyed themselves.
