Page 454 - Textbook of Pathology, 6th Edition

438 from disorders of the lungs. It is characterised by right RHEUMATIC FEVER AND
ventricular dilatation or hypertrophy, or both. Thus, cor
pulmonale is the right-sided counterpart of the hypertensive RHEUMATIC HEART DISEASE
heart disease described above.
Depending upon the rapidity of development, cor DEFINITION
pulmonale may be acute or chronic: Rheumatic fever (RF) is a systemic, post-streptococcal, non-
Acute cor pulmonale occurs following massive pulmonary suppurative inflammatory disease, principally affecting the
embolism resulting in sudden dilatation of the pulmonary heart, joints, central nervous system, skin and subcutaneous
trunk, conus and right ventricle. tissues. The chronic stage of RF involves all the layers of the
Chronic cor pulmonale is more common and is often heart (pancarditis) causing major cardiac sequelae referred
preceded by chronic pulmonary hypertension (Chapter 17). to as rheumatic heart disease (RHD). In spite of its name
Following chronic lung diseases can cause chronic suggesting an acute arthritis migrating from joint to joint, it
pulmonary hypertension and subsequent cor pulmonale: is well known that it is the heart rather than the joints which
i) Chronic emphysema is first and major organ affected. William Boyd years ago
ii) Chronic bronchitis gave the dictum ‘rheumatism licks the joint, but bites the whole
iii) Pulmonary tuberculosis heart’.
iv) Pneumoconiosis
v) Cystic fibrosis INCIDENCE
vi) Hyperventilation in marked obesity (Pickwickian The disease appears most commonly in children between
syndrome) the age of 5 to 15 years when the streptococcal infection is
vii) Multiple organised pulmonary emboli. most frequent and intense. Both the sexes are affected equally,
PATHOGENESIS. Chronic lung diseases as well as diseases though some investigators have noted a slight female
of the pulmonary vessels cause increased pulmonary preponderance.
vascular resistance. The most common underlying The geographic distribution, incidence and severity of
mechanism causing increased pulmonary blood pressure RF and RHD are generally related to the frequency and
(pulmonary hypertension) is by pulmonary vasoconstriction, severity of streptococcal pharyngeal infection. The disease
activation of coagulation pathway and obliteration of is seen more commonly in poor socioeconomic strata of the
pulmonary arterial vessels. Pulmonary hypertension causes society living in damp and overcrowded places which
SECTION III
pressure overload on the right ventricle and hence right promote interpersonal spread of the streptococcal infection.
ventricular enlargement. Initially, there is right ventricular Its incidence has declined in the developed countries as a
hypertrophy, but as cardiac decompensation sets in and right result of improved living conditions and early use of
heart failure ensues, dilatation of right ventricle occurs. antibiotics in streptococcal infection. But it is still common
The sequence of events involved in the pathogenesis of in the developing countries of the world like in India,
cor pulmonale is summarised in Fig. 16.23. Pakistan, some Arab countries, parts of Africa and South
America. In India, RHD and RF continue to a major public
MORPHOLOGIC FEATURES. In acute cor pulmonale, health problem. In a multicentric survey in school-going
there is characteristic ovoid dilatation of the right ventricle, children by the Indian Council of Medical Research, an
and sometimes of the right atrium. In chronic cor pulmonale, incidence of 1 to 5.5 per 1000 children has been reported.
there is increase in thickness of the right ventricular wall
from its normal 3 to 5 mm up to 10 mm or more. Often, ETIOPATHOGENESIS
Systemic Pathology
there is dilatation of the right ventricle too.
After a long controversy, the etiologic role of preceding throat
infection with β-haemolytic streptococci of group A in RF is
now well accepted. However, the mechanism of lesions in
the heart, joints and other tissues is not by direct infection
but by induction of hypersensitivity or autoimmunity. Thus,
there are 2 types of evidences in the etiology and
pathogenesis of RF and RHD: the epidemiologic evidence and
the immunologic evidence.
A. EPIDEMIOLOGIC EVIDENCE. There is a body of
clinical and epidemiological evidence to support the concept
that RF occurs following infection of the throat and upper
respiratory tract with β-haemolytic streptococci of Lancefield
group A. These evidences are as under:
1. There is often a history of infection of the pharynx and
upper respiratory tract with this microorganism about 2 to 3
weeks prior to the attack of RF. This period is usually the
Figure 16.23 Pathogenesis of cor pulmonale (RVH= right ventricular
hypertrophy, RHF= right heart failure). latent period required for sensitisation to the bacteria.