[Originally posted 8/3/2007]
One of the first aspects that struck me about my medical situation was the nature of the data. I'm a research scientist with a strong focus on experimental data. Carefully designed experiments with data verifying a hypothesis and ultimately independently reproduced and confirmed are a basic tenet of my scientific approach. In the medical field that is a fantasy. Try as one might, well-controlled experiments are difficult to design and carry out for many reasons.
In my case, the question was the relationship between unexplained strokes, known by the technocenti as "paradoxical emboli" and the PFO, that hole in the septum of the heart. What seems to be agreed upon by everyone is that there is a higher incidence of PFO in people who have experienced a stroke. In that population the occurrence of PFO is approximately 45-50% whereas in the general population estimates range from 25-30%. But that is a statistical correlation and not a causal relationship. It doesn't tell us whether closing the PFO will lead to any benefit.
The "theorists" (I hesitate to use the term) hypothesize one of two possible ways in which a PFO can cause a stroke. One is that it permits leakage of blood from the right to the left atrial chamber. That means that blood returning through the veins that is supposed to go to the lung for reoxygenation actually leaks to the other side and goes straight to the brain or the eye or other parts of the body. Any tiny clot carried in that stream can cause a stroke. A second theory is that the presence of the PFO can cause turbulence in the blood flow, creating a region where clots are more likely to be generated. Neither has been directly proven.
It's difficult to get enough participants in a well defined random study to determine the effectiveness of PFO closure in preventing strokes. Most people, like me, who reach the stage of having had one stroke and have discovered the PFO, don't want to take any chances and just want the hole closed. Depending solely on anticoagulant drugs to avoid the stroke seems much riskier, even if the data aren't clear. Hence, few takers sign up for the study.
But my heart won't wait for such studies to be completed. Decisions have to be made now. There is no luxury of waiting for nice clean experimental data. Such is the fertile field for medical ethics.