Page 298 - Concise Pathology for Exam Preparation ( PDFDrive )

11 Disorders of the Heart 283

• Low output heart failure is associated with a low cardiac output, eg, heart failure
associated with ischaemic heart disease, hypertension, cardiomyopathy, valvular dis-
eases and pericardial disease.

Common Causes of Heart Failure

• Failure of myocardial pump
• Myocardial infarction
• Hypertensive heart disease
• Myocarditis
• Cardiomyopathies
• Pulmonary embolism
• Anaemia, pregnancy and thyrotoxicosis (increased demand)
• Drugs like beta-blockers, corticosteroids and NSAIDs
• Obstruction to outflow
• Systemic hypertension
• Aortic and pulmonary stenosis
• Pulmonary hypertension
• Obstruction to inflow: Mitral and tricuspid stenosis
• Disorders of cardiac conduction: Cardiac arrhythmias

Clinical Manifestations of Heart Failure
• Dyspnoea: Dyspnoea is initially exertional, but progressively worsens to a stage of
breathlessness even at rest. The mechanisms underlying dyspnoea include
• Interstitial pulmonary oedema
• Respiratory muscle dysfunction/fatigue due to poor perfusion
• Bronchial mucosal oedema and increased bronchial mucous production
• Orthopnoea: Dyspnoea occurring in recumbent position (on lying flat) and relieved by
sitting up is known as orthopnoea. The mechanisms underlying orthopnoea include
• Increased venous return to the lungs in recumbent position
• Elevation of the diaphragm
• Reabsorption of the peripheral oedema that had accumulated while patient was
ambulant
• Paroxysmal nocturnal dyspnoea (PND)
• Severe shortness of breath occurring at night, which awakens the patient from sleep
and is relieved by sitting upright
• It is due to depression of the respiratory centre during sleep and reduced adrenergic
stimulation of the myocardium at night resulting in further impairment of myocardial
function
• Cyanosis of mucosa and nail beds
• Pulse: Sinus tachycardia (due to increased adrenergic activity) and pulsusalternans
(alternate large and small volume beats with a normal rhythm)
• Blood pressure: Diminished pulse pressure due to reduced stroke volume
• Jugular venous pressure: Raised as a consequence of elevated systemic venous pressure
• Liver (congestive hepatomegaly)
• Right upper quadrant pain from stretching of the capsule of the liver
• Liver is enlarged and tender due to elevated right-sided heart pressures transmitted
backward into the portal vein circulation
• Pleural effusion, ascites and pericardial effusion
• Right-sided pleural effusion is more common and results from increased pleural cap-
illary pressure and transudation of fluid into pleural space.
• Ascites results from transudation secondary to elevated pressure in hepatic veins,
portal veins and veins draining the peritoneum.
• Acute pulmonary oedema
• Caused by marked elevation of pulmonary capillary pressure
• Clinically, characterized by severe breathlessness, cough with copious, pinkish, frothy
expectoration and bilateral crepitations

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