Role of the Lymphatics in Cardiac Disease

Cardiovascular diseases remain the largest cause of death worldwide with recent evidence increasingly attributing the development and progression of these diseases to an exacerbated inflammatory response. As a result, significant research is now focused on modifying the immune environment to prevent the disease progression. This in turn has highlighted the lymphatic system in the pathophysiology of cardiovascular diseases owing, in part, to its established function in immune cell surveillance and trafficking. In this review, we highlight the role of the cardiac lymphatic system and its potential as an immunomodulatory therapeutic target in selected cardiovascular diseases.

Characterisation of hypertensive heart disease: pathological insights from a sudden cardiac death cohort to inform clinical practice

Hypertensive heart disease refers to changes in the myocardium that result from hypertension. The relationship between hypertensive heart disease and sudden cardiac death is well established, but there are few pathological studies. We examined the clinical and pathological features of hypertensive heart disease in sudden cardiac death victims from a national cardiovascular pathology registry. We investigated 5239 cases of sudden cardiac death between 1994 and 2018. Hearts were examined by two expert cardiac pathologists. Diagnostic criteria included history of hypertension, increased heart weight and left ventricular wall thickness in the absence of other causes. Collagen was quantified using picrosirius red staining and imaging software. Of 75 sudden cardiac death cases due to hypertensive heart disease (age at death: 54 ± 16 years; 56% males), 56 (75%) reported no prior cardiac symptoms. Thirty-four (45%) recorded a BMI ≥ 30. Only two (2.7%) had hypertensive heart disease diagnosed antemortem. Four (5%) were diagnosed clinically with hypertrophic cardiomyopathy, but lacked myocyte disarray at autopsy. All hearts showed concentric left ventricular hypertrophy and myocyte hypertrophy. Fibrosis was identified microscopically in 59 cases (81%). The posterior left ventricular wall showed the greatest increase in the percentage of collagen in hypertensive diseased hearts compared to controls (25.2% vs 17.9%, p = 0.034). Most sudden deaths due to hypertensive heart disease occur without prior cardiac symptoms; thus, clinical risk stratification is challenging. Hypertensive heart disease can be misdiagnosed in life as hypertrophic cardiomyopathy which has major implications for relatives. Pathologists require a history of hypertension and histology for a definitive diagnosis of hypertensive heart disease.

Redox Regulation of Cardiac ASK1 (Apoptosis Signal-Regulating Kinase 1) Controls p38-MAPK (Mitogen-Activated Protein Kinase) and Orchestrates Cardiac Remodeling to Hypertension

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Systemic hypertension increases cardiac workload causing cardiomyocyte hypertrophy and increased cardiac fibrosis. An underlying feature is increased production of reactive oxygen species. Redox-sensitive ASK1 (apoptosis signal-regulating kinase 1) activates stress-regulated protein kinases (p38-MAPK [mitogen-activated protein kinases] and JNKs [c-Jun N-terminal kinases]) and promotes fibrosis in various tissues. Here, we determined the specificity of ASK1 signaling in the heart, with the hypothesis that ASK1 inhibitors may be used to manage fibrosis in hypertensive heart disease. Using immunoblotting, we established that moderate levels of H₂O₂ activate ASK1 in neonatal rat cardiomyocytes and perfused rat hearts. ASK1 was activated during ischemia in adult rat hearts, but not on reperfusion, consistent with activation by moderate (not high) reactive oxygen species levels. In contrast, IL (interleukin)-1β activated an alternative kinase, TAK1 (transforming growth factor–activated kinase 1). ASK1 was not activated by IL1β in cardiomyocytes and activation in perfused hearts was due to increased reactive oxygen species. Selonsertib (ASK1 inhibitor) prevented activation of p38-MAPKs (but not JNKs) by oxidative stresses in cultured cardiomyocytes and perfused hearts. In vivo (C57Bl/6J mice with osmotic minipumps for drug delivery), selonsertib (4 mg/[kg·d]) alone did not affect cardiac function/dimensions (assessed by echocardiography). However, it suppressed hypertension-induced cardiac hypertrophy resulting from angiotensin II (0.8 mg/[kg·d], 7d), with inhibition of Nppa/Nppb mRNA upregulation, reduced cardiomyocyte hypertrophy and, notably, significant reductions in interstitial and perivascular fibrosis. Our data identify a specific reactive oxygen species→ASK1→p38-MAPK pathway in the heart and establish that ASK1 inhibitors protect the heart from hypertension-induced cardiac remodeling. Thus, targeting the ASK1→p38-MAPK nexus has potential therapeutic viability as a treatment for hypertensive heart disease.

Insights from examination of hearts from adults dying suddenly to the understanding of congenital cardiac malformations

Congenital heart disease is a rare but important finding in adults who experience sudden death. Examination of the congenitally malformed heart has historically been considered esoteric and best left to those with expertise. The Cardiac Risk in the Young cardiovascular pathology laboratory based at St George's University of London has now received over 6,000 cases. Of these, 21 congenitally malformed hearts were retained for research and educational purposes. Hearts were assessed using sequential segmental analysis, and causes of death were adjudicated based on thorough macroscopic examination and histology. Congenital malformations that were encountered included atrial septal defects, ventricular septal defects, tetralogy of Fallot, and transposition of the great arteries in both its regular and congenitally corrected variants. Findings also included hearts with mirror-imaged and isomeric atrial appendages. Direct causes of death included myocardial fibrosis, pulmonary hypertension, and hemorrhage. A small but notable proportion did not reveal a substrate for arrhythmia, raising the question of whether the terminal event was due to the congenital heart disease itself, or an underlying channelopathy. Here, we demonstrate the value of simple sequential segmental analysis in describing and categorizing the cases, with the concept of the "morphological method" serving to identify the distinguishing features of the cardiac components. Clin. Anat. 33:394-404, 2020. © 2019 Wiley Periodicals, Inc.