Former police officer Derek Chauvin is accused of killing George Floyd by restraining him in a way that led to his death. The prosecution says that Chauvin’s restraint caused Floyd to be unable to breathe, which resulted in a lack of oxygen and death. The defense argues that Floyd’s underlying health problems — primarily coronary artery disease, hypertension, and drug abuse — led to his death.
Both sides seem to have overlooked an important medical aspect of this case. They are missing the importance of Floyd’s initial cardiac rhythm, determined by the paramedics who arrived on the scene. It was pulseless electrical activity (PEA).
What Caused Floyd’s PEA?
PEA is characterized by a heart that has normal or near-normal QRS complexes on an electrocardiogram, but has no effective contraction, no effective heartbeat.
There are specific causes of PEA. One is a massive pericardial effusion surrounding the heart that squeezes the heart so tightly that it can’t move or contract. But that fluid does not damage the electrical system of the heart, so the electrical system will continue to generate QRS complexes. Another cause is severe blood loss. If very little or no blood gets into the heart then it will not contract, but the electrical system may continue to work, causing PEA. And another cause is severely low oxygen levels. Severely low oxygen levels can cause the heart to not contract in an effective manner, but the electrical system may still function and produce QRS complexes, hence PEA.
A cardiologist who testified in the Chauvin trial said that Floyd was in a PEA rhythm. The emergency department physician who cared for Floyd said the same thing. The forensic pathologist who testified for the defense said the same thing. Hence, there seemed to be agreement that Floyd was in PEA.
The dispute arose over the mechanism of that PEA. The prosecution said it was caused by Chauvin restraining Floyd in such a way that he could not breathe. This led to falling oxygen levels, which led to PEA. The doctor for the defense said that Floyd had 90% blockage of his right coronary artery and that a branch from the right coronary artery feeds the sinus node. He said the stress of the situation along with Floyd’s other health problems and the blocked right coronary led to lack of blood flow to the sinus node, which triggered a fatal arrhythmia. It was this fatal arrhythmia that caused his heart to stop and his oxygen levels to fall.
There are several problems with the scenario put forward by the defense. If the primary problem was an electrical one, which began with damage to the sinus node, then why would Floyd go into PEA? If his electrical system was so badly damaged that it caused a cardiac rhythm, such as ventricular fibrillation (Vfib), that caused his heart to stop, then how could it have recovered to the point that it would make normal or near normal QRS complexes, which are seen in PEA? With PEA, the electrical system of the heart is not as severely damaged. Rather, the heart is not beating for reasons other than a primary electrical problem. It would be very odd for a patient to go from Vfib to PEA, unless there were medical interventions such as CPR, medications, and/or defibrillation via shocks to the heart. Floyd had none of these, not even CPR, before the paramedics arrived. Therefore, it is highly unlikely that Floyd went from a Vfib arrest that was not addressed for at least 10 minutes to a PEA rhythm — such a situation may even be unheard of. I was surprised that this was not brought up during the trial. One explanation might be because the PEA diagnosis was not definitive, yet several authorities claimed that was the case.
Something else that was not brought up was that the sinus node is not supplied by the right coronary artery 100% of the time. About 40% of the time it comes off the circumflex artery. Also, when it does come off the right coronary, it comes off at a proximal point. If it came off above the blockage, that would be relevant. But, surprisingly, this was not discussed or investigated.
Overlooking Medical Fact Missteps
I’m also surprised at some things that were brought up. The doctor for the defense said that adrenaline release probably contributed to Floyd’s death. He said that adrenaline (also known as epinephrine) is a vasoconstrictor, implying that it would cause coronary vasoconstriction and thereby put Floyd’s heart in further danger of a fatal arrhythmia. However, adrenaline is not a vasoconstrictor of the coronary arteries. This has been shown in many studies, such as one in the American Heart Association journal Circulation Research. A quote from this study: “epinephrine resulted in a 37% increase in coronary blood flow.” Hence, the doctor for the defense did not know this basic medical information. Or, he did not tell the truth as part of a strategy. No one pointed out this mistake.
This doctor made a similar mistake about carbon monoxide. He saw a picture of Floyd lying on the ground near an exhaust pipe. This led him to speculate that Floyd may have inhaled fumes, resulting in high levels of carbon monoxide in his blood. However, he did not know whether the car was running. Also, the carboxyhemoglobin level in Floyd was measured — and determined not elevated. This measurement was discovered after this doctor had left, so when the prosecution tried to bring it up, the defense objected. The judge agreed with the defense and said that if the prosecution referred to this result there would be a mistrial. To approach the carboxyhemoglobin level with a threat of a mistrial speaks to fundamental problems with our legal system: it is more interested in protocol and its rules than the truth. Also, it lacks a scientific approach.
To approach this scientifically and medically would be to formulate a hypothesis such as: If George Floyd had a high level of carbon monoxide in his body, then this, in part, led to his death. A measured carboxyhemoglobin measurement would support or refute that hypothesis. There was such a measurement. Therefore, a scientific — and reasonable — approach would be to simply look at the level. But instead, the court said the jury could not see that level. It was off limits. This kind of stuff is an inherent part of our legal system. We would be better off to take a more scientific approach.
Focus on the Truth
The testimony of the doctor for the defense demonstrates problems with both our legal system and the medical profession. He presented medical information that was false, yet he was never challenged in the trial. His testimony also demonstrates problems with the profession of medicine. As a professor of pathology and residency director during his career, the doctor was very involved in the teaching of residents. What did he teach them? Did he teach them how to twist the truth for the sake of gain? Or, did he just teach them incorrect information, such as what he said about adrenaline, because he didn’t know any better?
An important lesson from the Chauvin trial is this: we need to reform both our legal and medical systems. We need to place more emphasis on truth and knowledge, and less emphasis on twisting the truth.
W. Robert Graham, MD, completed medical school and residency at UTHSC-Dallas (Parkland Hospital) and served as chief resident. Graham received an NIH fellowship at the Salk Institute for oncogene research in 1985. He was a professor of medicine at Baylor College of Medicine from 1998 to 2016. In retirement, he enjoys writing and ranching.
Last Updated April 19, 2021