Did George Floyd Die of Cardioinhibition From Pressure on His Neck?

Abstract

Introduction: Did George Floyd die from Officer Chauvin's knee triggering reflex cardioinhibition an instantaneous neurogenic cardiac arrest (INCA)? Objectives: This study was conducted to assess the findings necessary to conclude what constitutes an INCA death and apply them to the George Floyd case. Methods: We performed an intensive iterative search of the literature for such deaths. Results: The carotid sinus responds to neck pressure causing a neurogenic reflex mediated through the vagal nerve that causes cardioinhibition. This reflex may result in syncope, which occurs predominantly in young females and older males. Seven deaths occurred from carotid sinus massage, causing ventricular fibrillation. Twenty-seven purported INCA deaths were reported based on a history of near-instantaneous collapse, absence of evidence of vital reaction at death, or hemorrhage in "reflex zones." INCA deaths must be distinguished from those from emotional stress resulting in sympathetic action, rather than parasympathetic action. We found that the reported INCA deaths occur in young and old adults with and without underlying cardiac pathology. Conclusion: The death of George Floyd is unlikely to have been from a rare lethal neck reflex mechanism; other causes and mechanisms of death can explain his death. He did not die instantaneously of neck pressure but prolonged neck pressure. The initial cardiac rhythm was pulseless electrical rhythm, not a ventricular arrhythmia. Neither absence of vital reaction nor hemorrhage in a reflex zone was found at autopsy. We conclude that George Floyd did not die of INCA from pressure on his neck.

Keywords: Neck pressure; cardioinhibition; carotid sinus; sudden cardiac death; syncope.

Figure 1.

Cartoon of the carotid sinus.

Figure 2.

Dissection of the neck, exposing the carotid bifurcation and carotid sinus, superimposed upon the neck of the same individual [courtesy of Matthew B. Brown, DC OCME].

Figure 3.

Magnetic resonance imaging reconstruction shows the carotid arteries’ relation to the jaw and cervical vertebral column.

Figure 4.

Magnetic resonance imaging transverse section through the neck with contrast dye showing the internal (pale red arrow) and external (pale blue arrow) carotid arteries and their relation to other structures.

Figure 5.

Physiological response to carotid sinus stimulation.

Figure 6.

Classification of syncope [adapted from Brignole et al Figure 3 (43)].