Page 438 - Textbook of Pathology, 6th Edition

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Figure 16.5 Schematic diagram showing transverse section through the ventricles with left ventricular hypertrophy (concentric and eccentric).

(Fig. 16.5). The weight of the heart is increased above sites for the formation of new sarcomeres. Besides, the
normal, often over 500 gm. However, excessive epicar- nucleic acid content determinations have shown increase
dial fat is not indicative of true hypertrophy. in total RNA and increased ratio of RNA to DNA content
Grossly, Thickness of the left ventricular wall (excluding of the hypertrophied myocardial fibres.
trabeculae carneae and papillary muscles) above 15 mm
is indicative of significant hypertrophy. In concentric CONGENITAL HEART DISEASE
hypertrophy, the lumen of the chamber is smaller than
usual, while in eccentric hypertrophy the lumen is dilated Congenital heart disease is the abnormality of the heart
(Fig. 16.6). In pure hypertrophy, the papillary muscles and present from birth. It is the most common and important
trabeculae carneae are rounded and enlarged, while in form of heart disease in the early years of life and is present
hypertrophy with dilatation these are flattened. in about 0.5% of newborn children. The incidence is higher
Microscopically, there is increase in size of individual in premature infants. The cause of congenital heart disease
SECTION III
muscle fibres. There may be multiple minute foci of is unknown in majority of cases. It is attributed to multi-
degenerative changes and necrosis in the hypertrophied factorial inheritance involving genetic and environmental
myocardium (Fig. 16.7). These changes appear to arise as influences. Other factors like rubella infection to the mother
a result of relative hypoxia of the hypertrophied muscle during pregnancy, drugs taken by the mother and heavy
as the blood supply is inadequate to meet the demands of alcohol drinking by the mother, have all been implicated in
the increased fibre size. Ventricular hypertrophy renders causing in utero foetal injury resulting in congenital
the inner part of the myocardium more liable to ischaemia. malformations of the heart.
Electron microscopy reveals increase in the number of CLASSIFICATION. Congenital anomalies of the heart may
myofilaments comprising myofibrils, mitochondrial be either shunts (left-to-right or right-to-left), or defects
changes and multiple intercalated discs which are active
causing obstructions to flow. However, complex anomalies
Systemic Pathology

Figure 16.6 A, Concentric cardiac hypertrophy. Weight of the heart is increased. The chambers opened up at the apex show concentric
thickening of left ventricular wall (white arrow) with obliterated lumen (hypertrophy without dilatation). B, Eccentic cardiac hypertrophy. The heart
is heavier. The free left ventricular wall is thickened (black arrow) while the lumen is dilated (white arrow) (hypertrophy with dilatation).