|
Commotio Cordis and SM Play
Copyright 2001 by Jay Wiseman Please contact the author at jaywiseman@yahoo.com regarding reprint and reposting requests. At a recent play party, the dungeon monitor watched a scene in which the top delivered several full-force blows with a closed fist to the front of the bottom's chest area between their collarbones and nipples. While the play party rules did not speak to this behavior, there was some concern that these blows could have caused the bottom to go into cardiac arrest. Fortunately, in this case, that didn't happen. What is the nature of this concern? A sharp blow to the chest does cause the occasional cardiac arrest. Research has shown that these cardiac arrests can occur in people who seem to have entirely healthy hearts. Most such cardiac arrests seem to be caused by a sharp, focused blow to the chest by something like a baseball, hockey puck, or fist. The condition is called "commotio cordis" in the medical literature. (It is also sometimes known by the much more pronounceable term of "cardiac concussion.") A search at www.google.com on the phrase "commotio cordis" will turn up a number of very useful articles. In particular, try: http://www.la12.org/articles/commotio_cordis.htm (For brevity's sake, and given that this is not a formal, academic article, I will simply refer all those wanting further citations and more information to the web search engine of their choice. Let me add that there is a lot of good information on this topic that is quite readily findable on the web.) What seems to happen in commotio cordis is that if the chest is struck by a sharp blow during a very specific portion of a heartbeat, this blow can sometimes cause the electrical system of the heart to become severely disrupted. (For you medical-types reading this, the vulnerable period is a 15msec to 30msec interval just as the T wave is reaching its peak.) The sudden increase in internal chest pressure caused by the blow may create a vagal influence that also plays a role. In a worst-case situation, the blow causes the heart muscle to go into a disorganized quivering that pumps no blood. This disorganized quivering is called ventricular fibrillation -- probably the most common form of cardiac arrest. Ventricular fibrillation is quickly followed by unconsciousness. Untreated, the intensity of the heart muscle's quivering decreases until the heart is in total standstill. Once the heart reaches total standstill -- this commonly takes several minutes -- its chances of ever being prodded back into organized, productive pumping are usually extremely low. Many resuscitation attempts are stopped shortly after the heart reaches total standstill. According to animal experiments, not every single blow that occurs to the chest during this period results in ventricular fibrillation, but this is the time when the risk is greatest. In one study involving pigs, a blow timed to hit during this precise interval caused ventricular fibrillation 75% of the time. (Pig physiology is very similar to human physiology, thus a lot of medical research involving human medical issues takes place "in a swine model" during early study. I should note that one researcher speculated that pigs might be more vulnerable to ventricular fibrillation due to a chest blow than humans are. More on that point later.) Note: Some researchers have noted an occasional brief period of cardiac arrest occurring when the blow is struck during another portion of the heart's electrical cycle (again, for you medical-types, the QRS complex). However, these cardiac arrests apparently almost always self-correct and the heart spontaneously restarts within a few seconds. It is the blows that hit during a specific portion of the T wave, rather than during the QRS complex, which seem to cause essentially all of the persistent cardiac arrests. One researcher estimates that there is about a one percent chance that a given blow will impact the chest during the especially vulnerable period (There is also a much more benign condition called atrial fibrillation, which is not a form of cardiac arrest and is usually due to other causes. In fact, a large number of people are walking around with chronic atrial fibrillation. Other than pointing out that it exists, we don't need to get further into atrial fibrillation here.) Given that the average adult human heart beats more often than once a second ("textbook normal" range for an adult at rest is 60 to 100 beats per minute), it's important to note that this window of vulnerability occurs once per heartbeat, not once per second. Thus, if the heart is beating 75 times per minute the window "opens" 75 times during each minute, not 60 times. Who is at risk? This is still very much an open question. A number of researchers have lamented that there is no centralized, organized reporting system for these deaths. Efforts are underway to improve this lack, including the establishment of a central registry (United States Commotio Cordis Registry in Minneapolis), but the data is still murky. From a legal viewpoint, several researchers have expressed alarm that there have been unduly harsh prosecutions after someone died from a non-malicious blow to the chest. One very significant feature of the statistics that we do have regarding commotio cordis is that it is, for the most part, a younger person's condition. Apparently, the greater flexibility of the ribs of younger people put them at greater risk. In one study, approximately 70% of the victims were under 18. Other studies have had similar findings. Still, victims up to age 38 have been reported. Where is the danger area? The danger area seems to be the anterior chest area bounded by the collarbones above and the xiphoid process below (the arch of the rib cage), with the lateral borders corresponding to a line drawn downwards from the far tips of the collarbones joining with a line drawn lateral to the xiphoid process. No cases of commotio cordis have been reported from glancing blows to the breasts of women where the angle of the force was directed away from the underlying chest wall. Crunching a few numbers. So what are the chances of a single chest blow causing ventricular fibrillation? Let's make a few assumptions, crunch a few numbers, and see if we get something plausible. If a "textbook normal" human heartbeat ranges from 60 to 100 beats per minute, that averages out to 80 beats per minute or one beat every 3/4 of a second -- in other words, one beat every 750 milliseconds. If the window of vulnerability ranges from 15 to 30 milliseconds, that averages to 22.5 milliseconds. What percentage of the time is an average heartbeat vulnerable? Well, 22.5 divided by 750 would equal X divided by 100. If I remember my basic algebra correctly, X solves for 3%. Thus, the "window of vulnerability" is open 3% of the time in an average heartbeat. Under these circumstances, a blow to the heart in the swine model would be expected to cause ventricular fibrillation in three out of four blows or 2.25% of the time. If we assume that humans are only one-third as vulnerable as pigs are, then a blow to a human would cause ventricular fibrillation only one out of four times or 0.75% of the time -- in other words, three quarters of one percent. If we increase the heart rate to 120 beats per minute (a level it could easily reach during sexual arousal) and leave the other factors constant, the odds increase to 1.125%. Those two figures divide out and round up to 0.94%. One estimate of the reported risk was 1%, so it seems like we do indeed have a plausible risk estimate of there being roughly one chance in a hundred that a sharp blow to the chest will cause a cardiac arrest in a human being. However, if the odds turned out to be only one-tenth that bad, with the chances of a blow to the chest causing a cardiac arrest being only one in a thousand, that would still be pretty scary (to me, anyway). Actually, given the severity of a worst-case outcome, I would still worry if the odds were only one chance in ten thousand. What are the chances of a successful resuscitation? So far, even with very prompt basic CPR, the resuscitation rate following cardiac arrest due to commotio cordis is dismally low, ranging from 10% down to zero. There has been some speculation that prompt use of an automatic external defibrillator (AED) would increase the percentage of successful resuscitations. What should SM players do about all this? First, while the risk of a cardiac arrest due to commotio cordis happening to a particular bottom during a particular SM scene is, overall, probably very low, recognize that SM play which involves sudden, hard, impact to the bottom's chest may be riskier than it is commonly believed to be, particularly if the bottom is a younger person. While most such deaths have been the result of an impact from a relatively small item such as a fist or baseball, or from a kick, there are also reports of such deaths occurring following hard impacts between players or between a player and a goal post. Thus, it is plausible that a hard blow from a flogger to the anterior chest area could cause a commotio cordis arrest. Second, there seems to be no way to monitor such a practice. I don't see any way that either a top or a dungeon monitor could tell the difference between a "low risk" and a "high risk" blow to the chest. Party givers may want to consider this issue when drafting their party rules. Third, tops who intend to engage in play involving hard blows to a bottom's chest have an above-average need to acquire and maintain sharp CPR skills. Note # 1: In a very few cases, what caused the condition may also "cure" it. While, for the sake of keeping CPR instruction simple, the technique is not widely taught to the lay public, in a small percentage of cases the delivering of a sudden, hard blow (often called a "precordial thump" in the CPR literature) to the chest of a person already in cardiac arrest will restore a productive heartbeat. This is especially true if the thump is administered to the victim's chest very shortly after the cardiac arrest occurs. (Such a cardiac arrest is called a "witnessed arrest" in the CPR literature.) Some medical people will try a second such thump if the first one does not work, but the odds of a second thump succeeding if the first one did not succeed are low. If the first two thumps do not succeed, most medical people will not attempt any more of them but will instead start standard CPR. Note # 2: In a few cases, if the victim can give several hard coughs in the interval between when they go into ventricular fibrillation and when they lose consciousness, such coughing can also sometimes restore a productive heartbeat. However, "cough CPR" is a controversial topic. (The "how to survive a heart attack while alone" article drifting around the internet is riddled with errors.) While the technique has some promise, it is better dealt with during actual CPR training. I plan to do an essay on it. Fourth, the chances of a successful resuscitation due to a cardiac arrest caused by commotio cordis are not very high. However, the presence and prompt use of an automatic external defibrillator (AED) may very significantly increase the victim's chances of survival. AEDs are lightweight, small, easy to use, and coming down in price. (Many are now priced under $3,000.00.) I hope to see AEDs in greater evidence at SM events. They are increasingly found on airplanes, in stadiums, and in many other places. (Candidly, at an SM event, the chances are probably much higher that an AED would be needed to treat a cardiac arrest caused by ordinary medical conditions than by commotio cordis.) In summary, many people are not even aware that a sudden impact to the chest can cause the occasional cardiac arrest or that relatively younger people seem to be at above-average risk of such an event. Both SM players and party givers should be aware that the risk of such a cardiac arrest happening as a result of a blow to the bottom's chest is low but not nonexistent, and should adjust their preparations, play, and party rules accordingly.
Copyright 2001 by Jay Wiseman Please contact the author at jaywiseman@yahoo.com regarding reprint and reposting requests. |
