Aspects of paediatric cardiovascular pathology Michael T. Ashworth  Diagnostic Histopathology  Volume 25, Issue 8, Pages 313-323 (August 2019) DOI: 10.1016/j.mpdhp.2019.05.003 Copyright © 2019 The Author Terms and Conditions

Figure 1 Anterior view of the fixed fetal heart at 27 weeks' gestation. The atrial appendages surround the arterial pedicle. The right atrial appendage is pyramidal in shape with a broad junction with the right atrium. The left atrial appendage has a hooked tip and a narrow junction with the corresponding atrium. Diagnostic Histopathology 2019 25, 313-323DOI: (10.1016/j.mpdhp.2019.05.003) Copyright © 2019 The Author Terms and Conditions

Figure 2 Explanted heart from a 14-year-old with anthracycline cardiomyopathy. The heart is cut in a simulated 4-chamber view. The apical trabecular pattern of both ventricles is well seen. The right ventricle shows broad, parallel trabeculations. On the left side the trabeculations are finer and are interwoven. Note the pectinate muscles in the atria. In the right atrium they extend around the atrioventricular junction. The left atrioventricular junction, by contrast, is smooth. Diagnostic Histopathology 2019 25, 313-323DOI: (10.1016/j.mpdhp.2019.05.003) Copyright © 2019 The Author Terms and Conditions

Figure 3 Atrioventricular connections. a: Concordant connections: the right atrium is connected to the right ventricle and the left atrium to the left ventricle. There is usual atrial situs. b: Concordant connections with situs inversus - the right atrium is connected to the right ventricle and the left atrium to the left ventricle. c: ambiguous connections. This particular example shows left atrial isomerism. The right ventricle is on the right side of the body and the left ventricle on the left side. Both atria are of left morphology and the connection is thus ambiguous. As is frequently the case, there is an atrioventricular septal defect. d: Discordant connections. There is atrial situs solitus, but the left ventricle is on the right side and the right ventricle on the left side. The right atrium is connected to the left ventricle and the left atrium to the right ventricle. e: Double inlet ventricle. Both atria open into the same ventricular chamber (left ventricle). Double inlet right ventricle may also occur. With double inlet ventricle there is usually a rudimentary second ventricle connected by a ventricular septal defect to the dominant ventricle. f: Absent connection. This example shows absence of the right atrioventricular connection. There is atresia of the tricuspid valve and the right ventricle is small and connected to the left ventricle via a ventricular septal defect. There is also an atrial septal defect to permit flow of blood. A similar appearance may be seen with mitral atresia. Diagnostic Histopathology 2019 25, 313-323DOI: (10.1016/j.mpdhp.2019.05.003) Copyright © 2019 The Author Terms and Conditions

Figure 4 Ventriculoarterial connections. a: Concordant connections. Normal heart with usual atrial situs. b: Discordant connections. Transposition of the great arteries. There is usual atrial situs and the atrioventricular connections are concordant. The aorta arises from the right ventricle and the pulmonary artery from the left ventricle. The great arteries are parallel and lack the normal spiral relationship. c: Double outlet ventricle. Double outlet right ventricle viewed from the right side. The aorta arises from the right ventricle but there is a sub aortic ventricular septal defect (red asterisk) connecting it partly to the left ventricle. When greater than 50% override occurs the aorta by definition is committed to that ventricle. Double outlet left ventricle is much rarer. d: Single outlet of the heart. Common arterial trunk with a single vessel arising from both ventricles with an underlying ventricular septal defect and giving origin to the coronary arteries and pulmonary arteries. e: Single outlet of the heart: pulmonary atresia with ventricular septal defect. The aorta arises from the heart, overriding the ventricular septal defect. The pulmonary artery (shown in blue) is atretic and, although attached to the epicardial surface, does not connect with either ventricle. Diagnostic Histopathology 2019 25, 313-323DOI: (10.1016/j.mpdhp.2019.05.003) Copyright © 2019 The Author Terms and Conditions

Figure 5 Perimembranous VSD. The ventricular septal defect lies between the limbs of the septomarginal trabeculation. It is predominantly outlet in type. The septomarginal trabeculation is outlined in blue. Star = supra-ventricular crest. Diagnostic Histopathology 2019 25, 313-323DOI: (10.1016/j.mpdhp.2019.05.003) Copyright © 2019 The Author Terms and Conditions

Figure 6 Muscular VSD. The interventricular septum is viewed from the left ventricular aspect. There is a large oval defect in the mid part of the septum with a small strand of muscle crossing it. The defect is far removed from the membranous septum. Diagnostic Histopathology 2019 25, 313-323DOI: (10.1016/j.mpdhp.2019.05.003) Copyright © 2019 The Author Terms and Conditions

Figure 7 A drawing of the right aspect of the interventricular septum to demonstrate the septal structures. The tricuspid valve and its associated tension apparatus delineate the inlet part of the septum. The septo-marginal trabeculation and the sub pulmonary area represent the outlet, and the intervening part is the apical part. The membranous septum is shown in yellow. Diagnostic Histopathology 2019 25, 313-323DOI: (10.1016/j.mpdhp.2019.05.003) Copyright © 2019 The Author Terms and Conditions

Figure 8 Malalignment of ventricular septum. The outlet septum in this example of tetralogy of Fallot, as is typically the case in this condition, malaligned. The right ventricular aspect of the interventricular septum is exposed. The aorta overrides the ventricular septal defect. The plane of the outlet septum (the band of muscle between the pulmonary artery and the aorta) is set at an angle to the plane of the rest of the interventricular septum. Diagnostic Histopathology 2019 25, 313-323DOI: (10.1016/j.mpdhp.2019.05.003) Copyright © 2019 The Author Terms and Conditions

Figure 9 Mitochondrial cardiomyopathy. Four chamber view of the heart of a two-month old infant dying suddenly. The heart is greatly enlarged and shows hypertrophy of the ventricular myocardium. This is a characteristic appearance of mitochondrial cardiomyopathy presenting in the neonatal period. Diagnostic Histopathology 2019 25, 313-323DOI: (10.1016/j.mpdhp.2019.05.003) Copyright © 2019 The Author Terms and Conditions

Figure 10 Mitochondrial cardiomyopathy. The myocytes are enlarged and vacuolated and contain numerous mitochondria, many of which are greatly enlarged representing giant mitchondria. Diagnostic Histopathology 2019 25, 313-323DOI: (10.1016/j.mpdhp.2019.05.003) Copyright © 2019 The Author Terms and Conditions

Figure 11 The sections from the anterior left ventricular wall of a teenage boy dying of dilated cardiomyopathy secondary to Duchenne muscular dystrophy. The EvG stained section from the anterior left ventricle shows fibrosis of the middle one-third of the myocardium with dense scarring subepicardially. This sub epicardial location is typical of dystrophin related cardiomyopathy. Diagnostic Histopathology 2019 25, 313-323DOI: (10.1016/j.mpdhp.2019.05.003) Copyright © 2019 The Author Terms and Conditions

Figure 12 Mitogenic cardiomyopathy. A sections from the myocardium of the female infant dying of dilated cardiomyopathy. There is irregularity and hyperchromasia of the myocytes and at least three mitotic figures are visible in this one section. Diagnostic Histopathology 2019 25, 313-323DOI: (10.1016/j.mpdhp.2019.05.003) Copyright © 2019 The Author Terms and Conditions

Figure 13 Ventricular non-compaction. Postmortem heart of the 2-year-old girl dying of dilated cardiomyopathy. The heart is cut in a 4-chamber view. The left ventricle is dilated and globular in shape. There is thickening of its endocardium and the numerous recesses extend into the compact layer of the myocardium. Note that the papillary muscles of the mitral valve are inconspicuous. Diagnostic Histopathology 2019 25, 313-323DOI: (10.1016/j.mpdhp.2019.05.003) Copyright © 2019 The Author Terms and Conditions

Figure 14 Histiocytoid cardiomyopathy. A section from the myocardium of a 4-month-old boy who died suddenly after a short illness. The myocardium contains numerous nodules such as this one. At the bottom of the left of the field normal myocytes are seen. Most of the myocytes in this field are rounded granular and eosinophilic resembling histiocytes. Diagnostic Histopathology 2019 25, 313-323DOI: (10.1016/j.mpdhp.2019.05.003) Copyright © 2019 The Author Terms and Conditions