Hypertrophic Cardiomyopathy and Sudden Death Initially Identified at Autopsy

The Paradigm of Sudden Death Prevention in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a relatively common and, often, inherited cardiac disease, once regarded as largely untreatable with ominous prognosis and, perhaps, most visibly as a common cause of sudden cardiac death (SCD) in the young. However, HCM is now more accurately considered a treatable disease with management options that significantly alter its clinical course. This is particularly true for SCD because the penetration of implantable cardioverter-defibrillators into HCM practice enables primary prevention device therapy that reliably terminates potentially lethal ventricular tachyarrhythmias (3% to 4%/year). This therapeutic advance is largely responsible for >10-fold decrease in the overall disease-related mortality to 0.5%/year, independent of patient age. A guideline-based clinical risk stratification algorithm has evolved, which included variables identifiable with cardiac magnetic resonance: ≥1 risk markers judged major within the clinical profile of an individual patient, associated with a measure of physician judgment and shared decision-making, can be sufficient to consider the recommendation of a prophylactic defibrillator implant. Implantable cardioverter-defibrillator decisions using the American College of Cardiology and the American Heart Association traditional major risk marker strategy are associated with a 95% sensitivity for identifying those patients who subsequently experience appropriate therapy, albeit often 5 to 10+ years after implant but without heart failure deterioration or death after a device intervention. A mathematical SCD risk score proposed by European Society of Cardiology is associated with a relatively low sensitivity (33%) for predicting and preventing SCD events but with potential for less device overtreatment.

Characterization of heterozygous and homozygous mouse models with the most common hypertrophic cardiomyopathy mutation MYBPC3c.2373InsG in the Netherlands

Hypertrophic cardiomyopathy (HCM) is frequently caused by mutations in the cardiac myosin binding protein-C (cMyBP-C) encoding gene MYBPC3. In the Netherlands, approximately 25% of patients carry the MYBPC3c.2373InsG founder mutation. Most patients are heterozygous (MYBPC3+/InsG) and have highly variable phenotypic expression, whereas homozygous (MYBPC3InsG/InsG) patients have severe HCM at a young age. To improve understanding of disease progression and genotype-phenotype relationship based on the hallmarks of human HCM, we characterized mice with CRISPR/Cas9-induced heterozygous and homozygous mutations. At 18-28 weeks of age, we assessed the cardiac phenotype of Mybpc3+/InsG and Mybpc3InsG/InsG mice with echocardiography, and performed histological analyses. Cytoskeletal proteins and cardiomyocyte contractility of 3-4 week old and 18-28 week old Mybpc3c.2373InsG mice were compared to wild-type (WT) mice. Expectedly, knock-in of Mybpc3c.2373InsG resulted in the absence of cMyBP-C and our 18-28 week old homozygous Mybpc3c.2373InsG model developed cardiac hypertrophy and severe left ventricular systolic and diastolic dysfunction, whereas HCM was not evident in Mybpc3+/InsG mice. Mybpc3InsG/InsG cardiomyocytes also presented with slowed contraction-relaxation kinetics, to a greater extent in 18-28 week old mice, partially due to increased levels of detyrosinated tubulin and desmin, and reduced cardiac troponin I (cTnI) phosphorylation. Impaired cardiomyocyte contraction-relaxation kinetics were successfully normalized in 18-28 week old Mybpc3InsG/InsG cardiomyocytes by combining detyrosination inhibitor parthenolide and β-adrenergic receptor agonist isoproterenol. Both the 3-4 week old and 18-28 week old Mybpc3InsG/InsG models recapitulate HCM, with a severe phenotype present in the 18-28 week old model.

Challenges in Diagnosing Sudden Death Caused by Acute Hemorrhagic Pancreatitis: An Autopsy-Based Case Report

Forensic pathologists frequently encounter cases of sudden natural death. Most sudden natural deaths are attributed to cardiac causes. Acute pancreatitis, especially hemorrhagic pancreatitis, is an infrequent yet critical contributor to sudden death. The role of a forensic pathologist is imperative in such cases to find out the cause of the sudden death and to either confirm or refute any allegations. In this context, we describe a case of a 34-year-old male who experienced sudden death due to acute hemorrhagic pancreatitis, highlighting the need for a detailed autopsy, pathophysiological insights, and diagnostic challenges.

Mechanisms and prognostic impact of myocardial ischaemia in hypertrophic cardiomyopathy

Despite the progress made in risk stratification, sudden cardiac death and heart failure remain dreaded complications for hypertrophic cardiomyopathy (HCM) patients. Myocardial ischaemia is widely acknowledged as a contributor to cardiovascular events, but the assessment of ischaemia is not yet included in HCM clinical guidelines. This review aims to evaluate the HCM-specific pro-ischaemic mechanisms and the potential prognostic value of imaging for myocardial ischaemia in HCM. A literature review was performed using PubMed to identify studies with non-invasive imaging of ischaemia (cardiovascular magnetic resonance, echocardiography, and nuclear imaging) in HCM, prioritising studies published after the last major review in 2009. Other studies, including invasive ischaemia assessment and post-mortem histology, were also considered for mechanistic or prognostic relevance. Pro-ischaemic mechanisms in HCM reviewed included the effects of sarcomeric mutations, microvascular remodelling, hypertrophy, extravascular compressive forces and left ventricular outflow tract obstruction. The relationship between ischaemia and fibrosis was re-appraised by considering segment-wise analyses in multimodal imaging studies. The prognostic significance of myocardial ischaemia in HCM was evaluated using longitudinal studies with composite endpoints, and reports of ischaemia-arrhythmia associations were further considered. The high prevalence of ischaemia in HCM is explained by several micro- and macrostructural pathological features, alongside mutation-associated energetic impairment. Ischaemia on imaging identifies a subgroup of HCM patients at higher risk of adverse cardiovascular outcomes. Ischaemic HCM phenotypes are a high-risk subgroup associated with more advanced left ventricular remodelling, but further studies are required to evaluate the independent prognostic value of non-invasive imaging for ischaemia.

Differing strategies for sudden death prevention in hypertrophic cardiomyopathy

Sudden death (SD) has traditionally been the most visible and feared complication of hypertrophic cardiomyopathy (HCM). Substantial progress in reducing the occurrence of these catastrophic events represents a new paradigm in disease management. Prevention of SD in HCM has resulted from introduction of primary prevention ICDs that reliably terminate life-threatening ventricular tachyarrhythmias, as well as a matured risk stratification algorithm capable of reliably identifying those patients at highest risk. This initiative has been a major determinant of reducing HCM-related mortality to a low rate of 0.5%/year. In such a heterogeneous heart disease as HCM, no perfect risk stratification strategy is possible, and available approaches differ in terms of sensitivity and specificity for identifying patients with SD risk. Major cardiovascular societies, American Heart Association/American College of Cardiology in the USA and European Society of Cardiology in Europe have promoted different risk stratification guidelines creating the potential for judging SD risk in a given HCM patient differently based on commitment to a particular societal guideline or country of residence. In this review, we provide a critical but balanced assessment of these two divergent SD prevention strategies with regard to their respective strengths and weaknesses, as a guide to clinicians directly engaged in this important management issue.

CMR left ventricular strains beyond global longitudinal strain in differentiating light-chain cardiac amyloidosis from hypertrophic cardiomyopathy

Background

The clinical value of left ventricular (LV) global longitudinal strain (GLS) in the differential diagnosis of light-chain cardiac amyloidosis (AL-CA) and hypertrophic cardiomyopathy (HCM) has been previously reported. In this study, we analyzed the potential clinical value of the LV long-axis strain (LAS) to discriminate AL-CA from HCM. Furthermore, we analyzed the association between all the LV global strain parameters derived from cardiac magnetic resonance (CMR) feature tracking and LAS in both the AL-CA and HCM patients to assess the differential diagnostic efficacies of these global peak systolic strains.

Materials and methods

Thus, this study enrolled 89 participants who underwent cardiac MRI (CMRI), consisting of 30 AL-CA patients, 30 HCM patients, and 29 healthy controls. The intra- and inter-observer reproducibility of the LV strain parameters including GLS, global circumferential strain (GCS), global radial strain (GRS), and LAS were assessed in all the groups and compared. Receiver operating characteristic (ROC) curve analysis was performed to determine the diagnostic performances of the CMR strain parameters in discriminating AL-CA from HCM.

Results

The intra- and inter-observer reproducibility of the LV global strains and LAS were excellent (range of interclass correlation coefficients: 0.907-0.965). ROC curve analyses showed that the differential diagnostic performances of the global strains in discriminating AL-CA from HCM were good to excellent (GRS, AUC = 0.921; GCS, AUC = 0.914; GLS, AUC = 0.832). Furthermore, among all the strain parameters analyzed, LAS showed the highest diagnostic efficacy in differentiating between AL-CA and HCM (AUC = 0.962).

Conclusion

CMRI-derived strain parameters such as GLS, LAS, GRS, and GCS are promising diagnostic indicators that distinguish AL-CA from HCM with high accuracy. LAS showed the highest diagnostic accuracy among all the strain parameters.

Phenotype variation of hypertrophic cardiomyopathy in carriers of the p.Arg870His pathogenic variant in the MYH7 gene

The review analyzes variability of clinical manifestations of p.Arg870His in the MYH7 gene, which is repeatedly registered in patients with hypertrophic cardiomyopathy (HCM). The analysis involves the data from scientific publications obtained as a search result in the PubMed, СlinVar, and eLibrary.ru databases, as well as authors’ own results. A wide range of phenotypic manifestations have been revealed in carriers of p.Arg870His, from the asymptomatic to severe course, rapid progression, and early death. The review considers possible factors that modify the effect of the pathogenic variant (i.e. dosage of the pathogenic variant, the presence of other unfavorable genetic variants, etc.). The importance of accumulating information on the clinical features of HCM in the carriers of specific gene variants is emphasized in order to clarify their pathogenicity and to identify factors modifying the clinical outcome, which is important for the choice of the treatment strategy for HCM.

Derivation and Validation of a Screening Model for Hypertrophic Cardiomyopathy Based on Electrocardiogram Features

Background

Hypertrophic cardiomyopathy (HCM) is a widely distributed, but clinically heterogeneous genetic heart disease, affects approximately 20 million people worldwide. Nowadays, HCM is treatable with the advancement of medical interventions. However, due to occult clinical presentations and a lack of easy, inexpensive, and widely popularized screening approaches in the general population, 80–90% HCM patients are not clinically identifiable, which brings certain safety hazards could have been prevented. The majority HCM patients showed abnormal and diverse electrocardiogram (ECG) presentations, it is unclear which ECG parameters are the most efficient for HCM screening.

Objective

We aimed to develop a pragmatic prediction model based on the most common ECG features to screen for HCM.

Methods

Between April 1st and September 30th, 2020, 423 consecutive subjects from the International Cooperation Center for Hypertrophic Cardiomyopathy of Xijing Hospital [172 HCM patients, 251 participants without left ventricular hypertrophy (non-HCM)] were prospectively included in the training cohort. Between January 4th and February 30th, 2021, 163 participants from the same center were included in the temporal internal validation cohort (62 HCM patients, 101 non-HCM participants). External validation was performed using retrospectively collected ECG data from Xijing Hospital (3,232 HCM ECG samples from January 1st, 2000, to March 31st, 2020; 95,184 non-HCM ECG samples from January 1st to December 31st, 2020). The C-statistic was used to measure the discriminative ability of the model.

Results

Among 30 ECG features examined, all except abnormal Q wave significantly differed between the HCM patients and non-HCM comparators. After several independent feature selection approaches and model evaluation, we included only two ECG features, T wave inversion (TWI) and the amplitude of S wave in lead V1 (SV1), in the HCM prediction model. The model showed a clearly useful discriminative performance (C-statistic > 0.75) in the training [C-statistic 0.857 (0.818–0.896)], and temporal validation cohorts [C-statistic 0.871 (0.812–0.930)]. In the external validation cohort, the C-statistic of the model was 0.833 [0.825–0.841]. A browser-based calculator was generated accordingly.

Conclusion

The pragmatic model established using only TWI and SV1 may be helpful for predicting the probability of HCM and shows promise for use in population-based HCM screening.

Anatomical-MRI Correlations in Adults and Children with Hypertrophic Cardiomyopathy

Hypertrophic Cardiomyopathy (HCM) is the most frequent hereditary cardiovascular disease and the leading cause of sudden cardiac death in young individuals. Advancements in CMR imaging have allowed for earlier identification and more accurate prognosis of HCM. Interventions aimed at slowing or stopping the disease’s natural course may be developed in the future. CMR has been validated as a technique with high sensitivity and specificity, very few contraindications, a low risk of side effects, and is overall a good tool to be employed in the management of HCM patients. The goal of this review is to evaluate the magnetic resonance features of HCM, starting with distinct phenotypic variants of the disease and progressing to differential diagnoses of athlete’s heart, hypertension, and infiltrative cardiomyopathies. HCM in children has its own section in this review, with possible risk factors that are distinct from those in adults; delayed enhancement in children may play a role in risk stratification in HCM. Finally, a number of teaching points for general cardiologists who recommend CMR for patients with HCM will be presented.

Sudden Death in Adults: A Practical Flow Chart for Pathologist Guidance

The medico-legal term "sudden death (SD)" refers to those deaths that are not preceded by significant symptoms. SD in apparently healthy individuals (newborn through to adults) represents a challenge for medical examiners, law enforcement officers, and society as a whole. This review aims to introduce a useful flowchart that should be applied in all cases of SD. Particularly, this flowchart mixes the data obtained through an up-to-date literature review and a revision of the latest version of guidelines for autopsy investigation of sudden cardiac death (SCD) in order to support medico-legal investigation. In light of this review, following the suggested flowchart step-by-step, the forensic pathologist will be able to apply all the indications of the scientific community to real cases. Moreover, it will be possible to answer all questions relative to SD, such as: death may be attributable to cardiac disease or to other causes, the nature of the cardiac disease (defining whether the mechanism was arrhythmic or mechanical), whether the condition causing SD may be inherited (with subsequent genetic counseling), the assumption of toxic or illicit drugs, traumas, and other unnatural causes.

Update on the Diagnostic Pitfalls of Autopsy and Post-Mortem Genetic Testing in Cardiomyopathies

Inherited cardiomyopathies are frequent causes of sudden cardiac death (SCD), especially in young patients. Despite at the autopsy they usually have distinctive microscopic and/or macroscopic diagnostic features, their phenotypes may be mild or ambiguous, possibly leading to misdiagnoses or missed diagnoses. In this review, the main differential diagnoses of hypertrophic cardiomyopathy (e.g., athlete's heart, idiopathic left ventricular hypertrophy), arrhythmogenic cardiomyopathy (e.g., adipositas cordis, myocarditis) and dilated cardiomyopathy (e.g., acquired forms of dilated cardiomyopathy, left ventricular noncompaction) are discussed. Moreover, the diagnostic issues in SCD victims affected by phenotype-negative hypertrophic cardiomyopathy and the relationship between myocardial bridging and hypertrophic cardiomyopathy are analyzed. Finally, the applications/limits of virtopsy and post-mortem genetic testing in this field are discussed, with particular attention to the issues related to the assessment of the significance of the genetic variants.

Evolution of risk stratification and sudden death prevention in hypertrophic cardiomyopathy: Twenty years with the implantable cardioverter-defibrillator

Hypertrophic cardiomyopathy (HCM) is a relatively common inherited myocardial disorder, once regarded as largely untreatable with ominous prognosis and most visibly as a common cause of sudden death (SD) in the young. Over the last several years, HCM has been transformed into a contemporary treatable disease with management options that significantly alter clinical course. With the use of implantable cardioverter-defibrillators (ICDs) in the HCM patient population, a new paradigm has emerged, with primary prevention device therapy reliably terminating potentially lethal ventricular tachyarrhythmias (3%-4% per year) and being largely responsible for a >10-fold decrease in disease-related mortality (to 0.5% per year), independent of age. An evidenced-based and guideline directed clinical risk stratification algorithm has evolved, including variables identified with cardiac magnetic resonance. One or more risk markers judged major and relevant within a patient's clinical profile can be considered sufficient to recommend a primary prevention implant (associated with a measure of physician judgment and shared decision-making). ICD decisions using the prospective individual risk marker strategy have been associated with 95% sensitivity for identifying patients who subsequently experienced appropriate ICD therapy, (albeit often delayed substantially for >5 or >10 years after implant), but without heart failure deterioration or HCM death following device intervention. A rigid mathematically derived statistical risk model proposed by the European Society of Cardiology is associated with low sensitivity (ie, 33%) for predicting SD events. Introduction of prophylactically inserted ICDs to HCM 20 years ago has significantly altered the clinical course and landscape of this disease. SD prevention has reduced HCM mortality significantly, making preservation of life and the potential for normal longevity a reality for most patients.