Chronic heart failure is a complex and progressive disorder that occurs when the heart is incapable of generating sufficient cardiac output (CO) to meet the demands of the body. Initially, compensatory mechanisms may allow adequate CO to be maintained at rest but not during exercise (exercise intolerance). Eventually CO cannot be maintained at rest (decompensation); this can be precipitated by acute illness (e.g. influenza), stress or drugs (e.g. NSAIDs). Chronic heart failure is predominantly a disease of old age. It occurs in ∼2% of patients under 50 years, but >10% over 65; 5-year survival is <50%. Acute heart failure describes a sudden loss of cardiac function, for example acute coronary syndrome (see Chapter 44). It may cause pulmonary congestion and oedema (see below) and cardiogenic shock (see Chapter 31).

Causes of Heart Failure

The most common cause (∼70% cases) is impaired ventricular contraction with an ejection fraction <45% (systolic failure; Figure 46a), generally a consequence of ischaemic heart disease (IHD). Diastolic failure is due to impaired filling, caused by reduced ventricular compliance (flexibility; e.g. fibrosis, hypertrophy), restriction (e.g. pericarditis) or impaired relaxation (see below). Ejection fraction may be normal or increased. Systolic failure is generally accompanied by diastolic failure, while the latter can occur alone. Both involve increased filling pressures, so have similar clinical manifestations.

As IHD generally affects the left ventricle, left heart failure is most common, and is associated with dyspnoea (breathlessness), an enlarged heart and fatigue (see below). Right heart failure may result from chronic lung disease (cor pulmonale), pulmonary hypertension or embolism, and valve disease, but usually it is secondary to left heart failure (congestive or biventricular heart failure) (Figure 46b). Central venous pressure (CVP) is greatly increased, with consequent jugular venous distension, swelling of the liver (hepatomegaly), peripheral oedema and peritoneal fluid accumulation (ascites).

High output failure occurs when a healthy heart is unable to meet grossly elevated demands for output due to anaemia or a drastically reduced peripheral resistance (e.g. septic shock).

Pathophysiology

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