Page 435 - Textbook of Pathology, 6th Edition

HEART FAILURE ACUTE AND CHRONIC HEART FAILURE. Depending 419
upon whether the heart failure develops rapidly or slowly,
Definition it may be acute or chronic.
Heart failure is defined as the pathophysiologic state in which Acute heart failure. Sudden and rapid development of heart
impaired cardiac function is unable to maintain an adequate failure occurs in the following conditions:
circulation for the metabolic needs of the tissues of the body. i) Larger myocardial infarction
It may be acute or chronic. The term congestive heart failure ii) Valve rupture
(CHF) is used for the chronic form of heart failure in which iii) Cardiac tamponade
the patient has evidence of congestion of peripheral iv) Massive pulmonary embolism
circulation and of lungs (Chapter 5). CHF is the end-result v) Acute viral myocarditis
of various forms of serious heart diseases. vi) Acute bacterial toxaemia.
In acute heart failure, there is sudden reduction in cardiac
Etiology output resulting in systemic hypotension but oedema does
not occur. Instead, a state of cardiogenic shock and cerebral
Heart failure may be caused by one of the following factors, hypoxia develops.
either singly or in combination:
Chronic heart failure. More often, heart failure develops
1. INTRINSIC PUMP FAILURE. The most common and slowly as observed in the following states:
most important cause of heart failure is weakening of the i) Myocardial ischaemia from atherosclerotic coronary
ventricular muscle due to disease so that the heart fails to artery disease
act as an efficient pump. The various diseases which may ii) Multivalvular heart disease
culminate in pump failure by this mechanisms are as under: iii) Systemic arterial hypertension
i) Ischaemic heart disease iv) Chronic lung diseases resulting in hypoxia and pulmo-
ii) Myocarditis nary arterial hypertension
iii) Cardiomyopathies v) Progression of acute into chronic failure.
iv) Metabolic disorders e.g. beriberi In chronic heart failure, compensatory mechanisms like
v) Disorders of the rhythm e.g. atrial fibrillation and flutter. tachycardia, cardiac dilatation and cardiac hypertrophy try CHAPTER 16
to make adjustments so as to maintain adequate cardiac
2. INCREASED WORKLOAD ON THE HEART. output. This often results in well-maintained arterial pressure
Increased mechanical load on the heart results in increased and there is accumulation of oedema.
myocardial demand resulting in myocardial failure.
Increased load on the heart may be in the form of pressure LEFT-SIDED AND RIGHT-SIDED HEART FAILURE.
load or volume load. Though heart as an organ eventually fails as a whole, but
i) Increased pressure load may occur in the following functionally, the left and right heart act as independent units. The Heart
states: From clinical point of view, therefore, it is helpful to consider
a) Systemic and pulmonary arterial hypertension. failure of the left and right heart separately. The clinical
b) Valvular disease e.g. mitral stenosis, aortic stenosis, manifestations of heart failure result from accumulation of
pulmonary stenosis. excess fluid upstream to the left or right cardiac chamber
c) Chronic lung diseases. whichever is initially affected (Fig. 16.3):
ii) Increased volume load occurs when a ventricle is Left-sided heart failure. It is initiated by stress to the left
required to eject more than normal volume of the blood heart. The major causes are as follows:
resulting in cardiac failure. This is seen in the following i) Systemic hypertension
conditions: ii) Mitral or aortic valve disease (stenosis)
a) Valvular insufficiency iii) Ischaemic heart disease
b) Severe anaemia iv) Myocardial diseases e.g. cardiomyopathies, myocarditis.
c) Thyrotoxicosis v) Restrictive pericarditis.
d) Arteriovenous shunts The clinical manifestations of left-sided heart failure result
e) Hypoxia due to lung diseases. from decreased left ventricular output and hence there is
accumulation of fluid upstream in the lungs. Accordingly, the
3. IMPAIRED FILLING OF CARDIAC CHAMBERS. major pathologic changes are as under:
Decreased cardiac output and cardiac failure may result from i) Pulmonary congestion and oedema causes dyspnoea and
extra-cardiac causes or defect in filling of the heart: orthopnoea (Chapter 5).
a) Cardiac tamponade e.g. haemopericardium, hydroperi- ii) Decreased left ventricular output causing hypoperfusion
cardium and diminished oxygenation of tissues e.g. in kidneys causing
b) Constrictive pericarditis. ischaemic acute tubular necrosis (Chapter 22), in brain
causing hypoxic encephalopathy (Chapter 30), and in skeletal
Types of Heart Failure muscles causing muscular weakness and fatigue.
Heart failure may be acute or chronic, right-sided or left- Right-sided heart failure. Right-sided heart failure occurs
sided, and forward or backward failure. more often as a consequence of left-sided heart failure.