Postmortem cardiac magnetic resonance in sudden cardiac death

Morphological and Genetic Aspects for Post-Mortem Diagnosis of Hypertrophic Cardiomyopathy: A Systematic Review

Hypertrophic cardiomyopathy (HCM) is one of the most common genetic cardiovascular diseases, and it shows an autosomal dominant pattern of inheritance. HCM can be clinically silent, and sudden unexpected death due to malignant arrhythmias may be the first manifestation. Thus, the HCM diagnosis could be performed at a clinical and judicial autopsy and offer useful findings on morphological features; moreover, it could integrate the knowledge on the genetic aspect of the disease. This review aims to systematically analyze the literature on the main post-mortem investigations and the related findings of HCM to reach a well-characterized and stringent diagnosis; the review was performed using PubMed and Scopus databases. The articles on the post-mortem evaluation of HCM by gross and microscopic evaluation, imaging, and genetic test were selected; a total of 36 studies were included. HCM was described with a wide range of gross findings, and there were cases without morphological alterations. Myocyte hypertrophy, disarray, fibrosis, and small vessel disease were the main histological findings. The post-mortem genetic tests allowed the diagnosis to be reached in cases without morpho-structural abnormalities; clinical and forensic pathologists have a pivotal role in HCM diagnosis; they contribute to a better definition of the disease and also provide data on the genotype-phenotype correlation, which is useful for clinical research.

Autopsy for Medical Diagnostics: Finding the Cause of Sudden Unexpected Death through Investigation of the Cardiac Conduction System by Serial Sections

Sudden unexpected death (SUD) is a fatal event that occurs in an apparently healthy subject in a way that such an abrupt outcome could have not been predicted. SUD-including sudden intrauterine unexplained death (SIUD), sudden neonatal unexpected death (SNUD), sudden infant death syndrome (SIDS), sudden unexpected death of the young (SUDY), and sudden unexpected death in the adult (SUDA)-occurs as the first manifestation of an unknown underlying disease or within a few hours of the presentation of a disease. SUD is a major unsolved, shocking form of death that occurs frequently and can happen at any time without warning. For each case of SUD, a review of clinical history data and performance of a complete autopsy, particularly focused on the study of the cardiac conduction system, were carried out according to the necropsy protocol devised by the Lino Rossi Research Center, Università degli Studi di Milano, Italy. Research cases collected and selected for this study were represented by 75 SUD victims that were subdivided into 15 SIUD, 15 SNUD, 15 SUDY, and 15 SUDA victims. After a routine autopsy and clinical history analysis, death remained unexplained, and hence a diagnosis of SUD was assigned to 75 subjects, which included 45 females (60%) and 30 (40%) males ranging in age from 27 gestational weeks to 76 years. Serial sections of the cardiac conduction system disclosed frequent congenital alterations of the cardiac conduction system in fetuses and infants. An age-related significant difference in distribution among the five age-related groups was detected for the following anomalies of the conduction system: central fibrous body (CFB) islands of conduction tissue, fetal dispersion, resorptive degeneration, Mahaim fiber, CFB cartilaginous meta-hyperplasia, His bundle septation, sino-atrial node (SAN) artery fibromuscular thickening, atrio-ventricular junction hypoplasia, intramural right bundle branch, and SAN hypoplasia. The results are useful for understanding the cause of death for all SUD cases that were unexpected and would have otherwise remained unexplained, so as to motivate medical examiners and pathologists to perform more in-depth studies.

Increased Epicardial Adipose Tissue (EAT), Left Coronary Artery Plaque Morphology, and Valvular Atherosclerosis as Risks Factors for Sudden Cardiac Death from a Forensic Perspective

Background: In sudden cardiac deaths (SCD), visceral adipose tissue has begun to manifest interest as a standalone cardiovascular risk factor. Studies have shown that epicardial adipose tissue can be seen as a viable marker of coronary atherosclerosis. This study aimed to evaluate, from a forensic perspective, the correlation between body mass index (BMI), heart weight, coronary and valvular atherosclerosis, left ventricular morphology, and the thickness of the epicardial adipose tissue (EAT) in sudden cardiac deaths, establishing an increased thickness of EAT as a novel risk factor. Methods: This is a retrospective case−control descriptive study that included 80 deaths that were autopsied, 40 sudden cardiac deaths, and 40 control cases who hanged themselves and had unknown pathologies prior to their death. In all the autopsies performed, the thickness of the epicardial adipose tissue was measured in two regions of the left coronary artery, and the left ventricular morphology, macro/microscopically quantified coronary and valvular atherosclerosis, and weight of the heart were evaluated. Results: This study revealed a higher age in the SCD group (58.82 ± 9.67 vs. 53.4 ± 13.00; p = 0.03), as well as a higher incidence in females (p = 0.03). In terms of heart and coronary artery characteristics, there were higher values of BMI (p = 0.0009), heart weight (p < 0.0001), EAT of the left circumflex artery (LCx) (p < 0.0001), and EAT of the left anterior descending artery (LAD) (p < 0.0001). In the multivariate analysis, a high baseline value of BMI (OR: 4.05; p = 0.004), heart weight (OR: 5.47; p < 0.001), EAT LCx (OR: 23.72; p < 0.001), and EAT LAD (OR: 21.07; p < 0.001) were strong independent predictors of SCD. Moreover, age over 55 years (OR: 2.53; p = 0.045), type Vb plaque (OR: 17.19; p < 0.001), mild valvular atherosclerosis (OR: 4.88; p = 0.002), and moderate left ventricle dilatation (OR: 16.71; p = 0.008) all act as predictors of SCD. Conclusions: The data of this research revealed that higher baseline values of BMI, heart weight, EAT LCx, and EAT LAD highly predict SCD. Furthermore, age above 55 years, type Vb plaque, mild valvular atherosclerosis, and left ventricle dilatation were all risk factors for SCD.

Post-Mortem Cardiac Magnetic Resonance in Explanted Heart of Patients with Sudden Death

BACKGROUND

We sought to evaluate the diagnostic accuracy of post-mortem cardiac magnetic resonance (PMCMR) of explanted hearts to detect the cardiac causes of sudden death.

METHODS

PMCMR was performed in formalin-fixed explanted hearts of 115 cases of sudden death. Histological sampling of myocardium was performed using two different approaches: (1) guideline-based sampling; (2) guideline-based plus PMCMR-driven sampling.

RESULTS

Forensic diagnosis of cardiac cause of death was ascertained in 72 (63%) patients. When the guideline-driven histological sampling was used, the PMCMR interpretation matched with final forensic diagnosis in 93 out of 115 cases (81%) with sensitivity of 88% (79-95%), specificity of 65% (47-80%), PPV of 84% (78-90%), NPV of 73% (58-84%), accuracy of 81% (72-88%), and AUC of 0.77 (0.68-0.84). When a PMCMR-driven approach was added to the guideline-based one, the matching increased to 102 (89%) cases with a PMCMR sensitivity of 89% (80-94%), a specificity of 86% (67-96%), PPV of 95% (89-98%), NPV of 73% (59-83%), accuracy of 89% (81-93%), and AUC of 0.88 (0.80-0.93).

CONCLUSIONS

PMCMR has high accuracy to identify the cardiac cause of sudden death and may be considered a valid auxilium for forensic diagnosis. PMCMR could improve histological diagnosis in conditions with focal myocardial involvement or demonstrating signs of myocardial ischemia.

Myocardial Infarction Following COVID-19 Vaccine Administration: Post Hoc, Ergo Propter Hoc?

Vaccination against coronavirus disease 2019 (COVID-19) is the safest and most effective strategy for controlling the pandemic. However, some cases of acute cardiac events following vaccine administration have been reported, including myocarditis and myocardial infarction (MI). While post-vaccine myocarditis has been widely discussed, information about post-vaccine MI is scarce and heterogenous, often lacking in histopathological and pathophysiological details. We hereby present five cases (four men, mean age 64 years, range 50–76) of sudden death secondary to MI and tightly temporally related to COVID-19 vaccination. In each case, comprehensive macro- and microscopic pathological analyses were performed, including post-mortem cardiac magnetic resonance, to ascertain the cause of death. To investigate the pathophysiological determinants of MI, toxicological and tryptase analyses were performed, yielding negative results, while the absence of anti-platelet factor 4 antibodies ruled out vaccine-induced thrombotic thrombocytopenia. Finally, genetic testing disclosed that all subjects were carriers of at least one pro-thrombotic mutation. Although the presented cases do not allow us to establish any causative relation, they should foster further research to investigate the possible link between COVID-19 vaccination, pro-thrombotic genotypes, and acute cardiovascular events.

Diagnostics of messenger ribonucleic acid (mRNA) severe acute respiratory syndrome-corona virus‑2 (SARS-CoV‑2) vaccination-associated myocarditis—A systematic review

Background

Objective

Methods

Results

Conclusion

Supplementary Information

State of the Art on the Role of Postmortem Computed Tomography Angiography and Magnetic Resonance Imaging in the Diagnosis of Cardiac Causes of Death: A Narrative Review

The need of a minimally invasive approach, especially in cases of cultural or religious oppositions to the internal examination of the body, has led over the years to the introduction of postmortem CT (PMCT) methodologies within forensic investigations for the comprehension of the cause of death in selected cases (e.g., traumatic deaths, acute hemorrhages, etc.), as well as for personal identification. The impossibility to yield clear information concerning the coronary arteries due to the lack of an active circulation to adequately distribute contrast agents has been subsequently overcome by the introduction of coronary-targeted PMCT Angiography (PMCTA), which has revealed useful in the detection of stenoses related to calcifications and/or atherosclerotic plaques, as well as in the suspicion of thrombosis. In parallel, due to the best ability to study the soft tissues, cardiac postmortem MR (PMMR) methodologies have been further implemented, which proved suitable for the detection and aging of infarcted areas, and for cardiomyopathies. Hence, the purpose of the present work to shed light on the state of the art concerning the value of both coronary-targeted PMCTA and PMMR in the diagnosis of coronary artery disease and/or myocardial infarction as causes of death, further evaluating their suitability as alternatives or complementary approaches to standard autopsy and histologic investigations.

Post-mortem computer tomography in ten cases of death while diving: a retrospective evaluation

INTRODUCTION

Self-contained underwater breathing apparatus (SCUBA) diving deaths have always been a challenge for forensic pathologists. Post-mortem computer tomography (PMCT) allows intracorporeal gas visualization, contributing to identify the cases in which the cause of death is arterial gas embolism (AGE). However, in the literature, it is indicated to perform the radiological examination within 24 h after death.

MATERIALS AND METHODS

In this retrospective study, 32 cases of death who had undergone PMCT 24-48 h after death/corpse finding between January 2011 and March 2021 were analyzed, including ten cases of SCUBA divers who died of AGE. All cases' radiological images were reviewed to localize the intracorporeal gas distribution alongside other findings that are usually related to SCUBA diving death. A semi-quantitative evaluation was also performed.

RESULTS

Most of the divers showed gas within the left heart and the arteries. In addition, the semi-quantitative evaluation revealed that the divers presented a higher mean amount of intraarterial gas compared to the fresh corpses. On the other hand, the putrefied corpses presented gas within the portal system and generalized subcutaneous emphysema with higher frequency and quantity than the divers and fresh corpses.

CONCLUSION

Our cases suggested that the PMCT, even when performed 24-48 h after death, remains a valuable tool to diagnose AGE in cases of SCUBA diving deaths. In addition, with the limit of the small sample size, our data showed that at least a medium quantity of intraarterial gas, when not associated with a high amount of gas within the portal system and subcutaneous emphysema, could be considered a diagnostic criterion of AGE.

Sudden Cardiac Death and Ex-Situ Post-Mortem Cardiac Magnetic Resonance Imaging: A Morphological Study Based on Diagnostic Correlation Methodology

During the last years, post-mortem imaging has gradually been assumed within research in the field of forensic pathology. This role appears to be clearly and simply applied in the trauma field with the use of conventional radiography or Post Mortem Computed Tomography (PMCT). Recently, particular attention was paid to cardiovascular imaging using Post Mortem Magnetic Resonance Imaging (PMMRI). The present experimental study aims to: (i) confirm the efficacy of a Post Mortem Cardiac Resonance Imaging (PMCRI) study protocol for the study of human hearts collected during the autopsy; (ii) apply the defined protocol on subjects who died of “SCD (sudden cardiac death)”, to identify alterations that could guide subsequent sampling. Two hearts of healthy subjects (A: male 22 years; B: female 26 years), who died from causes other than SCD were collected and compared to hearts that belonged to SCD individuals (C: male, 47 years old; D: female, 44 years old; E: male; 72 years old). The exams were performed on a 1.5 T scanner (Philips Intera Achieva, Best, the Netherlands) on hearts collected during autopsy and after a 30-day formalin fixation. Two readers analyzed the obtained images blindly and after randomization. From the comparison between the data from imaging and the macroscopic and histological investigations carried out, the present study proved the effectiveness of a PMMRI protocol to study ex-situ hearts. Moreover, it suggested the following semeiology in post-mortem SCD cases: the hyperintense area with indistinct margins in the Short Tau Inversion Recovery (STIR) sequence was linked to edema or area of pathological fibers, whereas the hypointense area in the T2-FFE sequences was linked to fibrosis. PMMRI can provide a valuable benefit to post-mortem investigations, helping to distinctly improve the success rate of histological sampling and investigations, which remains the gold standard in the diagnosis of sudden death.

Post-mortem CMR in a model of sudden death due to myocardial ischemia: validation with connexin-43

OBJECTIVES

We sought to evaluate the effectiveness of post-mortem cardiac magnetic resonance (PM-CMR) for the identification of myocardial ischemia as cause of sudden cardiac death (SCD) when the time interval between the onset of ischemia and SCD is ≤ 90 min.

METHODS

PM-CMR was performed in 8 hearts explanted from pigs with spontaneous death caused by occlusion of the left anterior descending coronary artery: 4 with SCD after ≤ 40 min of coronary occlusion and 4 between 40 and 90 min. PM-CMR included conventional T1 and T2-weighted image and T1, T2, and T2* mapping techniques. Imaging data were compared and validated with immunohistochemical evaluation of the altered proportion and redistribution of phosphorylated versus non-phosphorylated connexin 43 (CX43 and npCX43, respectively), an established molecular marker of myocardial ischemia.

RESULTS

At T2-weighted images, the ischemic core was hypointense (core/remote ratio 0.67 ± 0.11) and surrounded by and hyperintense border zone. Compared to remote myocardium, the ischemic core had higher T1 (p = 0.0008), and lower T2 (p = 0.007) and T2* (p = 0.002). Cytoplasmatic npX43 and the npCX43/CX43 ratio were significantly higher in animals deceased > 40 min than in others.

CONCLUSION

PM-CMR can reliably detect early signs of myocardial damage induced by ischemia, based on conventional pulse sequences complemented by a novel ad hoc application of quantitative mapping techniques.

KEY POINTS

• Post-mortem MRI may help to understand cause of sudden cardiac death. • Post-mortem MRI allows detection of signs of myocardial ischemia as cause of sudden cardiac death within 90 and 40 min following coronary occlusion as demonstrated in a pig model of myocardial ischemia. • Signs of myocardial ischemia using conventional and mapping MRI technique are associated with the immunohistochemical changes of phosphorylated and dephosphorylated connexin-43 which is an established molecular marker of myocardial ischemia.

Post-Mortem Cardiac Magnetic Resonance for the Diagnosis of Hypertrophic Cardiomyopathy

Background: Post-mortem cardiac magnetic resonance (PMCMR) is an emerging tool supporting forensic medicine for the identification of the causes of cardiac death, such as hypertrophic cardiomyopathy (HCM). We proposed a new method of PMCMR to diagnose HCM despite myocardial rigor mortis. Methods: We performed CMR in 49 HCM patients, 30 non-HCM hypertrophy, and 32 healthy controls. In cine images, rigor mortis was simulated by the analysis of the cardiac phase corresponding to 25% of diastole. Left ventricular mass, mean, and standard deviation (SD) of WT, maximal WT, minimal WT, and their difference were compared for the identification of HCM. These parameters were validated at PMCMR, evaluating eight hearts with HCM, 10 with coronary artery disease, and 10 with non-cardiac death. Results: The SD of WT with a cut-off of > 2.4 had the highest accuracy to identify HCM (AUC 0.95, 95% CI = 0.89–0.98). This was particularly evident in the female population of HCM (AUC=0.998), with 100% specificity (95% CI = 85–100%) and 96% sensitivity (95% CI = 79–99%). Using this parameter, at PMCMR, all of the eight patients with HCM were correctly identified with no false positives. Conclusions: PMCMR allows identification of HCM as the cause of sudden death using the SD of WT > 2.4 as the diagnostic parameter.

T2 and T2∗ mapping in ex situ porcine myocardium: myocardial intravariability, temporal stability and the effects of complete coronary occlusion

Diagnosis of ischaemia-related sudden cardiac death in the absence of microscopic and macroscopic ischaemic lesions remains a challenge for medical examiners. Medical imaging techniques increasingly provide support in post-mortem examinations by detecting and documenting internal findings prior to autopsy. Previous studies have characterised MR relaxation times to investigate post-mortem signs of myocardial infarction in forensic cohorts. In this prospective study based on an ex situ porcine heart model, we report fundamental findings related to intramyocardial variability and temporal stability of T₂ as well as the effects of permanent coronary occlusion on T₂ and T₂^∗ relaxation in post-mortem myocardium. The ex situ porcine hearts included in this study (n= 19) were examined in two groups (S_s, n= 11 and S_i, n= 8). All magnetic resonance imaging (MRI) examinations were performed ex situ, at room temperature and at 3 T. In the S_s group, T₂ mapping was performed on slaughterhouse porcine hearts at different post-mortem intervals (PMI) between 7 and 26 h. Regarding the intramyocardial variability, no statistically significant differences in T₂ were observed between myocardial segments (p= 0.167). Assessment of temporal stability indicated a weak negative correlation (r=- 0.21) between myocardial T₂ and PMI. In the S_i group, animals underwent ethanol-induced complete occlusion of the left anterior descending artery. T₂ and T₂^∗ mapping were performed within 3 h of death. Differences between the expected ischaemic and remote regions were statistically significant for T₂ (p= 0.007), however not for T₂^∗ (p= 0.062). Our results provide important information for future assessment of the diagnostic potential of quantitative MRI in the post-mortem detection of early acute myocardial infarction.

Postmortem computed tomography angiography (PMCTA) and traditional autopsy in cases of sudden cardiac death due to coronary artery disease: a systematic review and meta-analysis

INTRODUCTION

Several studies have been performed to assess the efficacy of postmortem computed tomography angiography (PMCTA) in solving cases of sudden cardiac death, even in comparison with the traditional autopsy. However, the results were often inconsistent and inconclusive. Therefore, a global discussion on the subject through a systematic review of the literature and a meta-analysis is necessary.

METHODS

A systematic search of PubMed was performed up to April 23, 2018. Studies exploring the role of PMCTA in cases of sudden cardiac death and the accuracy of this method in diagnosing the cause of death compared to traditional autopsy were included.

RESULTS

The overall sensitivity and specificity of the seven included studies, using conventional autopsy as a reference standard, were 92% and 95%, respectively. The positive and negative likelihood ratios were, respectively, 20.76 (95% CI 1.16-370.2) and 0.08 (95% CI 0.03-0.17), showing that PMCTA represents a strong indicator of the posttest probability of disease. The diagnostic odds ratio and the area under the curve were, respectively, 261.54 (95% CI 1.87-5760.53) and 0.93 (95% CI 0.90-0.95), indicating a high diagnostic power of the test.

CONCLUSION

PMCTA demonstrated a high accuracy in the diagnosis of parietal and luminal coronary changes but was less effective in detecting myocardial ischemia and necrosis. Therefore, the only radiological investigation is often insufficient to determine the cause of sudden death and the conventional autopsy remains the gold standard. However, PMCTA can improve the performance of the autopsy, serving as an aid and guide in the sampling phase for histopathological investigations.