Characteristics of deceleration capacity and deceleration runs in vasovagal syncope

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

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.

Purported Self-Organized Criticality of the Cardiovascular Function: Methodological Considerations for Zipf's Law Analysis

Self-organized criticality is a universal theory for dynamical systems that has recently been applied to the cardiovascular system. Precise methodological approaches are essential for understanding the dynamics of cardiovascular self-organized criticality. This study examines how the duration and quality of data recording affect the analysis of cardiovascular self-organized criticality, with a focus on the beat-by-beat heart rate variability time series obtained from seven healthy subjects in a standing position. Drawing a Zipf diagram, we evaluated the distribution of cardiovascular events of bradycardia and tachycardia. We identified tipping points for the distribution of both bradycardia and tachycardia events. By varying the recording durations (1, 2, 5, 10, 20, 30, and 40 min) and sampling frequencies (500, 250, and 100 Hz), we investigated their influence on the observed distributions. While shorter recordings can effectively capture cardiovascular events, they may underestimate the variables describing their distribution. Additionally, the tipping point of the Zipf distribution differs between bradycardia and tachycardia events. Comparisons of the distribution of bradycardia and tachycardia events should be conducted using long data recordings. Utilizing devices with lower sampling frequencies may compromise data fidelity. These insights contribute to refining experimental protocols and advancing our understanding of the complex dynamics underlying cardiovascular regulation.

Safety and efficacy of cardioneuroablation for vagal bradycardia in a single arm prospective study

Cardioneuroablation (CNA) is currently considered as a promising treatment option for patients with symptomatic bradycardia caused by vagotonia. This study aims to further investigate its safety and efficacy in patients suffering from vagal bradycardia. A total of 60 patients with vagal bradycardia who underwent CNA in the First Affiliated Hospital of Xinjiang Medical University from November 2019 to June 2022. Preoperative atropine tests revealed abnormal vagal tone elevation in all patients. First, the electroanatomic structures of the left atrium was mapped out by using the Carto 3 system, according to the protocol of purely anatomy-guided and local fractionated intracardiac electrogram-guided CNA methods. The upper limit of ablation power of superior left ganglion (SLGP) and right anterior ganglion (RAGP) was not more than 45W with an ablation index of 450.Postoperative transesophageal cardiac electrophysiological examination was performed 1 to 3 months after surgery. The atropine test was conducted when appropriate. Twelve-lead electrocardiogram, Holter electrocardiogram, and skin sympathetic nerve activity were reviewed at 1, 3, 6 and 12 months after operation. Adverse events such as pacemaker implantation and other complications were also recorded to analyze the safety and efficacy of CNA in the treatment of vagus bradycardia. Sixty patients were enrolled in the study (38 males, mean age 36.67 ± 9.44, ranging from 18 to 50 years old). None of the patients had a vascular injury, thromboembolism, pericardial effusion, or other surgical complications. The mean heart rate, minimum heart rate, low frequency, low/high frequency, acceleration capacity of rate, and skin sympathetic nerve activity increased significantly after CNA. Conversely, SDNN, PNN50, rMSSD, high frequency, and deceleration capacity of rate values decreased after CNA (all P < 0.05). At 3 months after ablation, the average heart rate, maximum heart rate, and acceleration capacity of heart rate remained higher than those before ablation, and the deceleration capacity of heart rate remained lower than those before ablation and the above results continued to follow up for 12 months after ablation (all P < 0.05). There was no significant difference in other indicators compared with those before ablation (all P > 0.05). The remaining 81.67% (49/60) of the patients had good clinical results, with no episodes of arrhythmia during follow-up. CNA may be a safe and effective treatment for vagal-induced bradycardia, subject to confirmation by larger multicenter trials.