Page 437 - Textbook of Pathology, 6th Edition

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Figure 16.4 Schematic pathophysiology of compensatory mechanisms in cardiac failure.

chambers causing volume overload resulting in cardiac Right ventricular hypertrophy. Most of the causes of right
failure that ends in death (Fig. 16.4). ventricular hypertrophy are due to pulmonary arterial CHAPTER 16
hypertension. These are as follows:
Cardiac Hypertrophy i) Pulmonary stenosis and insufficiency
ii) Tricuspid insufficiency
Hypertrophy of the heart is defined as an increase in size iii) Mitral stenosis and/or insufficiency
and weight of the myocardium. It generally results from iv) Chronic lung diseases e.g. chronic emphysema,
increased pressure load while increased volume load (e.g. bronchiectasis, pneumoconiosis, pulmonary vascular disease
valvular incompetence) results in hypertrophy with etc.
dilatation of the affected chamber due to regurgitation of the v) Left ventricular hypertrophy and failure of the left The Heart
blood through incompetent valve. The atria may also ventricle.
undergo compensatory changes due to increased workload.
The basic factors that stimulate the hypertrophy of the
myocardial fibres are not known. It appears that stretching Cardiac Dilatation
of myocardial fibres in response to stress induces the cells to Quite often, hypertrophy of the heart is accompanied by
increase in length. The elongated fibres receive better cardiac dilatation. Stress leading to accumulation of excessive
nutrition and thus increase in size. Other factors which may volume of blood in a chamber of the heart causes increase in
stimulate increase in size of myocardial fibres are anoxia (e.g. length of myocardial fibres and hence cardiac dilatation as a
in coronary atherosclerosis) and influence of certain compensatory mechanism.
hormones (e.g. catecholamines, pituitary growth hormone).
CAUSES. Accumulation of excessive volume of blood within
CAUSES. Hypertrophy with or without dilatation may the cardiac chambers from the following causes may result
involve predominantly the left or the right heart, or both in dilatation of the respective ventricles or both:
sides. i) Valvular insufficiency (mitral and/or aortic insufficiency
Left ventricular hypertrophy. The common causes are as in left ventricular dilatation, tricuspid and/or pulmonary
under: insufficiency in right ventricular dilatation)
i) Systemic hypertension ii) Left-to-right shunts e.g. in VSD
ii) Aortic stenosis and insufficiency iii) Conditions with high cardiac output e.g. thyrotoxicosis,
iii) Mitral insufficiency arteriovenous shunt
iv) Coarctation of the aorta iv) Myocardial diseases e.g. cardiomyopathies, myocarditis
v) Occlusive coronary artery disease v) Systemic hypertension.
vi) Congenital anomalies like septal defects and patent
ductus arteriosus MORPHOLOGIC FEATURES. Hypertrophy of the myo-
vii) Conditions with increased cardiac output e.g. thyro- cardium without dilatation is referred to as concentric, and
toxicosis, anaemia, arteriovenous fistulae. when associated with dilatation is called eccentric