[I am open to correction in any point of the post below].

….all diseases may, in some sense, be called affections of the nervous system, because in almost every disease the nerves are more or less hurt; and in consequence of this, various sensations, motions and changes, are produced in the body.

–Robert Whytt (1714-1766), Scottish Physician

 

One of my obsessions as a child (and as an adult) is probably related to my having Autism Spectrum Disorder, Level 1 (in my case, what used to be called “Asperger’s Syndrome). I have always been fascinated by the heart and death and why a particular medical condition caused the heart to stop beating, especially if the condition was not itself a heart disease. I’d wonder about how a gunshot that missed the heart could sometimes cause rapid (or in the case of certain head wounds, nearly immediate) cardiac arrest. I would see Daddy shoot a rabbit, and it would run for ten or twenty yards, then collapse, dead. Why did its heart beat strongly enough to support its running, then suddenly stop. Or, in another scenario, why can a human being hold her breath over three minutes (and for free divers, close to ten minutes), yet someone who slips underwater or chokes on a piece of meat suffers cardiac arrest, in some cases, in a minute or two. Recently I heard of a case of a twenty-eight year old man who choked on food, and when rescue arrived two minutes later, his heart had already stopped. He was revived and had no neurological effects—but what caused his heart to stop so quickly.

Now I am not a medical doctor; the furthest I got in the medical field was as an EMT-Basic who was not even certified to give IVs or advanced cardiac life support. However, I can read, and over the years I learned that people shot often bleed out and that people who drown in fresh water can suffer cardiac arrest within a couple of minutes from electrolyte imbalances, but what about the choking victim. In the case of the gunshot victim, why does the loss of 30-50% of blood volume arrest the heart? Surely that is enough blood to stretch the sarcomeres enough for systole to continue.

I used to blame the heart—it was strong, yes, but also very fragile—too fragile, and stops too easily or too quickly for doctors to halt the underlying cause of the arrest in time to avoid brain damage or death. It turns out that often the real culprit is not the heart, but the brain.

The brain responds to bodily trauma in a way that is often destructive to the body. True, there is the diving reflex that diverts blood flow to the heart and brain that allows some drowning victims to survive. However, the rapid release of neurotransmitters in trauma or asphyxia or even in a myocardial infarction (heart attack) can result in stoppage of the heart. In effect, the sympathetic nervous system which speeds up the body, with its neurotransmitters, conflicts with the parasympathetic nervous system, which slows the bodily functions, and this conflict can lead to cardiac instability and a fatal arrhythmia. While the electrical instability of the heart itself can cause a fatal ventricular arrhythmia during an MI, often the big straw that breaks the small camel’s back is a massive release of stress hormones that is “ordered” by the brain. In the case of severe bleeding, such as occurs in gunshot wounds, a nervous system mechanism causes the heart to slow down (“brady down”) and stop after 30-50% of blood volume is lost. Some head injuries, such as bullet wounds that affect key areas of the brain associated with the brain stem, cause, according to a military medic with whom I talked, almost immediate Torsades de Pointes (a chaotic heart rhythm) which progresses to ventricular fibrillation and death. The military uses pharmacological blockers to cut off sympathetic and parasympathetic signals to the heart, and sometimes that buys extra time to treat the patient. A recent animal study published by the National Academy of Sciences found that it is the release of neurotransmitters with conflicting effects on the body that leads to cardiac arrest, and when such parasympathetic and sympathetic signals are blocked, it buys several minutes in which the heart continues to beat until oxygen is totally exhausted. Yet this time could allow doctors to reverse the asphyxia without going through the (far more often than not) unsuccessful CPR and advanced cardiac life support in the face of cardiac arrest. Some scientists are not suggesting that in cases of asphyxia cardiac arrest, animal studies be done to determine whether pharmacological blocking agents to stop both parasympathetic and sympathetic signals from reaching the heart during asphyxia crises will keep the heart beating longer. Apparently there is a pattern to the course of dying in such cases, and knowing the pattern can help the timing of intervention. If blocking agents work in animals, this may be an option for human treatment.

Thus I should stop blaming the heart for early cardiac arrest in these conditions, at least in most cases, and blame the brain instead. A person with the strongest heart in the world could go into cardiac arrest quickly from asphyxia or blood loss if her nervous system effects cause the arrest.

As a philosopher of religion, this raises some issues for intelligent design arguments, at least those in the British natural theology tradition. Animal bodies are filled with examples of poor design; Francis Collins, who is a devout Christian, mentions some of them in his attack on intelligent design arguments (one of the design flaws is that instead of a totally separate, two-tube system for food and air, we have a system in which a flap closes the airway while we eat so that air goes into the trachea rather than the esophagus. Collins points out that any human engineer would have enough sense to avoid such a flawed design. The fact that our brains “try” to kill us during severe disease, trauma, or asphyxia does not suggest intelligent design—it suggests that some of the so-called protective mechanisms of the brain can make cardiac arrest occur more rapidly, resulting in less time for doctors to focus on underlying causes and resulting in the deaths of many people who would not otherwise die. Give me a good cosmological contingency argument any day over an intelligent design argument. Now I am not calling God incompetent; I believe it is possible that evolution became flawed due to an angelic fall (as we see in J. R. R. Tolkien’s mythical account, in which Melkor (or Morgoth) and his allies damaged nature itself in their rebellion against Eru (God).

I suppose the satisfaction of curiosity is a good feeling, but I am also frustrated with the slow progress of medicine in this area in which very few studies have been done. I am glad some scientists are working in this seminal area of science and medicine and hope that their efforts result in lives saved from an early death.

Advertisements