Relationship between cardiopulmonary resuscitation and injuries of the cardiac conduction system: Pathological features and pathogenesis of such injuries*

Rib fractures and other injuries after cardiopulmonary resuscitation for non-traumatic cardiac arrest: a systematic review and meta-analysis

PURPOSE

This study aims to ascertain the prevalence of rib fractures and other injuries resulting from CPR and to compare manual with mechanically assisted CPR. An additional aim was to summarize the literature on surgical treatment for rib fractures following CPR.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Embase, Medline Ovid, Cochrane Central, Web of Science, and Google Scholar.

REVIEW METHODS

The databases were searched to identify studies reporting on CPR-related injuries in patients who underwent chest compressions for a non-traumatic cardiopulmonary arrest. Subgroup analysis was conducted to compare the prevalence of CPR-related injuries in manual versus mechanically assisted chest compressions. Studies reporting on surgery for CPR-related rib fractures were also reviewed and summarized.

RESULTS

Seventy-four studies reporting CPR-related injuries were included encompassing a total of 16,629 patients. Any CPR-related injury was documented in 60% (95% confidence interval [95% CI] 49-71) patients. Rib fractures emerged as the most common injury, with a pooled prevalence of 55% (95% CI 48-62). Mechanically assisted CPR, when compared to manual CPR, was associated with a higher risk ratio for CPR-related injuries of 1.36 (95% CI 1.17-1.59). Eight studies provided information on surgical stabilization of CPR-related rib fractures. The primary indication for surgery was the inability to wean from mechanical ventilation in the presence of multiple rib fractures.

CONCLUSION

Rib fractures and other injuries frequently occur in patients who undergo CPR after a non-traumatic cardiopulmonary arrest, especially when mechanical CPR is administered. Surgical stabilization of CPR-related rib fractures remains relatively uncommon.

LEVEL OF EVIDENCE

Level III, systematic review and meta-analysis.

Pathological and Comprehensive Genetic Investigation of Autopsy Cases of Idiopathic Bradyarrhythmia

BACKGROUND

Idiopathic bradyarrhythmia is considered to be due to pathological degeneration of the cardiac conduction system (CCS) during aging. There appears to have been no comprehensive genetic investigations in patients with idiopathic bradyarrhythmia.

METHODS AND RESULTS

Ten autopsy cases with advanced bradyarrhythmia (6 men and 4 women; age: 70-94 years, 81.5±6.9 years; 5 cases each of sinus node dysfunction [SND] and complete atrioventricular block [CAVB]) were genetically investigated by using whole-exome sequencing. Morphometric analysis of the CCS was performed with sex-, age- and comorbidity-matched control cases. As a result, severe loss of nodal cells and distal atrioventricular conduction system were found in SND and CAVB, respectively. However, the conduction tissue loss was not significant in either the atrioventricular node or the proximal bundle of His in CAVB cases. A total of 13 heterozygous potential variants were found in 3 CAVB and 2 SND cases. Of these 13 variants, 4 were missense in the known progressive cardiac conduction disease-related genes: GATA4 and RYR2. In the remaining 9 variants, 5 were loss-of-function mutation with highly possible pathogenicity.

CONCLUSIONS

In addition to degenerative changes of selectively vulnerable areas in the heart during advancing age, the vulnerability of the CCS, which may be associated with "rare variants of small effect," may also be a contributing factor to the degeneration of CCS, leading to "idiopathic" bradyarrhythmia.

Iatrogenic Injuries in Manual and Mechanical Cardiopulmonary Resuscitation

PURPOSE

Mechanical chest compression has been shown to be equivalent to manual chest compression in providing survival benefits to patients experiencing cardiac arrest. There has been a growing need for a contemporary review of iatrogenic injuries caused by mechanical in comparison with manual chest compression. Our study aims to analyze the studies that document significant life-threatening iatrogenic injuries caused by mechanical and manual chest compression.

METHODS

A systematic review of PubMed and Embase was performed according to Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines. All studies published after January 1^st, 2000 were reviewed using inclusion/exclusion criteria and completed by May 2020. A total of 7202 patients enrolled in 15 studies were included in our meta-analysis.

RESULTS

Significant life-threatening iatrogenic injuries had higher odds of occurring when mechanical chest compression was used compared to manual chest compression, especially for hemothorax and liver lacerations. Mechanical chest compression involves consistently deeper compression depths compared to manual chest compression, potentially resulting in more injuries. In the mechanical chest compression cohort, chest wall fractures had the highest incidence rate (55.7%), followed by sternal fracture (28.3%), lung injuries (3.7%), liver (1.0%), and diaphragm (.2%) lacerations.

CONCLUSIONS

Mechanical chest compression was associated with more iatrogenic injuries as compared to manual chest compression. Further research is needed to define the appropriate application of mechanical in comparison with manual chest compression in different scenarios. Levels of provider training, different mechanical chest compression device types, patient demographics, and compression duration/depth may all play roles in influencing outcomes.

Two autopsy cases with injuries to the stomach following cardiopulmonary resuscitation

We herein report two autopsy cases with gastric injury associated with cardiopulmonary resuscitation (CPR). Case 1 was a 36-year-old woman who was found in cardiopulmonary arrest possibly caused by a fall from a height of 8 m. She received continuous manual chest compression with artificial ventilation while being transferred to the hospital. Autopsy revealed bruises on her left upper arm with a fracture to the left humerus and advanced pneumohemothorax that was associated with laceration of the left lung due to fracture of the dorsal left costa. Furthermore, complete rupture of the gastric wall (25 cm) was found without hemorrhage. Case 2 was an 85-year-old man found unconscious on the road. He had a history of oral anticoagulant administration, cognitive impairment, and gait disorder. He also received cardiac massage and manual artificial ventilation during CPR. Autopsy revealed severe head injury, possibly caused by a backward fall. His stomach was markedly dilated by air and a fresh intramural hematoma had extended into all layers of the stomach and adjacent omentum; however, injury of the abdominal wall was not evident. Histopathological investigation of the brain revealed advanced Alzheimer's disease and Lewy pathology, and the damaged neural tissue, which was positive for the amyloid precursor protein. We determined that the gastric injuries in both cases had been caused by CPR. We conclude that careful investigation is required for gastric injury cases to determine the etiology and correlation between gastric injury and cause of death when the victims receive CPR.

Minimal inflammatory foci of unknown etiology may be a tentative sign of early stage inherited cardiomyopathy

Although relatively uncommon, pathologists may encounter minimal inflammatory foci in the absence of typical structural heart disease; however, the clinicopathological significance of minimal inflammatory foci, including correlation with sudden unexpected death, is unexplored. From 1072 serial autopsy subjects, cases with unexplained minimal inflammatory foci, the extent of which was under 1% of the whole examined ventricle, were extracted to exclude cases with borderline/focal myocarditis resulting from local, systemic infection, or autoimmune mechanisms. Immunohistochemistry and genetic analysis targeting viral genomes and heart disease-related genes using next generation sequencing were performed. We detected 10 cases with unexplained minimal inflammatory foci (five males, five females, aged 15-68 years). The cause and/or manner of death were sudden unexpected death (6 cases, 60%), sudden unexpected death with epilepsy (1 case, 10%), drowning in a hot bath (1 case, 10%), and suicide (2 cases, 20%). In none of these cases was pathogen-derived DNA or RNA detected. In 8 of the 10 cases (80%), 17 possible pathogenic genetic variants causative for arrhythmogenic right ventricular cardiomyopathy or dilated cardiomyopathy; DSP was the most frequently involved gene (three cases with two different variants), followed by LAMA4 and MYBPC3 (two cases, two variants for each gene), LDB3 (two cases, one variant), and the remaining 10 variants occurred in seven cases (DSC2, RYR2, SOS1, SCN5A, SGCD, LPL, PKP2, MYH11, GATA6, and DSG2). All mutations were missense mutations. DSP_Lys1581Glu and DSC2_p.Thr275Met were classified according to American College of Medical Genetics and Genomics consensus statement guidelines as pathogenic or likely pathogenic for arrhythmogenic cardiomyopathy in three patients (30%). The remaining 15 variants were classified as potentially pathogenic variants. Unexplained minimal inflammatory foci may be an early sign of inherited cardiomyopathy, and such cases might already have arrhythmogenic potential that can lead to sudden unexpected death. Detection of minimal inflammatory foci by careful pathological examination may indicate the value of conducting comprehensive genetic analysis, even if significant structural abnormalities are not evident.

Breaking your heart-A review on CPR-related injuries

Cardiopulmonary resuscitation (CPR) has been shown to increase survival after cardiac arrest, but is associated with the risk of acquired injuries to the patient. While traumatic chest wall injuries are most common, other injuries include upper airway, pulmonary and intra-abdominal injuries. This review discusses the risk factors and prevalence of CPR-related injuries.

A systematic review and pooled analysis of CPR-associated cardiovascular and thoracic injuries

OBJECTIVE

The incidence of thoracic injuries resulting from cardiopulmonary resuscitation (CPR) is not well characterized. We describe a case in which a CPR-associated atrial rupture was identified with ultrasound and successfully managed in the intensive care unit with a bedside thoracotomy and atrial repair. We then describe a systematic review with pooled data analysis of CPR-associated cardiovascular, pulmonary, pleural, and thoracic wall injuries.

DATA SOURCES

PubMed, Scopus, EMBASE, and Web of Science were searched to identify relevant published studies. Unpublished studies were identified by searching the Australian and New Zealand Clinical Trials Registry, World Health Organization International Clinical Trials Registry Platform, Cochrane Library, ClinicalTrials.gov, Current Controlled Trials, and Google.

STUDY SELECTION

Inclusion criteria for the pooled analysis were any clinical or autopsy study in which (a) patients underwent cardiopulmonary resuscitation, (b) chest compressions were administered either manually or with the assistance of active compression-decompression devices, and (c) autopsy or dedicated imaging assessments were conducted to identify complications. Exclusion criteria for the pooled analysis were pre-clinical studies, case reports and abstracts.

DATA EXTRACTION

Nine-hundred twenty-eight potentially relevant references were identified. Twenty-seven references met inclusion criteria.

DATA SYNTHESIS

A systematic review of the literature is provided with pooled data analysis.

CONCLUSIONS

The incidence of reported CPR-associated cardiovascular and thoracic wall injuries varies widely. CPR with active compression-decompression devices has a higher reported incidence of cardiopulmonary injuries. Bedside ultrasound may be a useful adjunct to assess and risk-stratify patients to identify serious or life-threatening CPR-associated injuries.

Reduction in Purkinje fiber number in rats undergone fatal electrocution

Purkinje fibers in cardiac conduction tissue during fatal electrocution. A total of 16 Sprague Dawley rats were divided into 2 groups as follows: the electrocution group and the control group.Animals were deeply anesthetized with sodium pentobarbital and, in the electrocution group, all 8 rats underwent a fatal electrical shock (220 v,50 Hz) followed by cervical dislocation. In the control group, all 8 rats underwent execution by cervical dislocation. Following death, hearts were rapidly excised and perfused with 1% paraformaldehyde before tissues of the left ventricular anterior wall (LVAW) were isolated. The microscopic structure of the Purkinje fibers were subsequently analyzed using conventional hematoxylin and eosin staining. A majority of the Purkinje fibers were located in groups among the cardiac muscle of the LVAW. A significant reduction in Purkinje fiber expression was displayed in the electrocution group compared with the control group (P G 0.05).The mean total number of Purkinje fibers for the electrocution and control groups were 59 T 11 and 3287 T 19 cells, respectively (P G 0.05).The estimated number of Purkinje fibers in the LVAW of the control group was significantly greater than observed in the electrocution group(41.09 T 0.24 vs. 0.7375 T 0.14, P G 0.05). The findings of the current study suggest that such a reduction would be reflected in abnormal cardiac conduction and a possible cause of sudden death.