The Heart

Question 1

Define heart failure.

Answer 1

Congestive cardiac failure is the common endpoint of many forms of heart disease.

It occurs when impaired function renders the heart unable to maintain output to meet the metabolic demands of the body, or when it can only do so at elevated pressures.

Congestive cardiac failure may be left-sided, right-sided or both, and it may be systolic or diastolic.

Question 2

Describe systolic heart failure.

Answer 2

Systolic heart failure involves a progressive deterioration of myocardial contractile function.

Commonly due to ischaemia, valvular disease and primary myocardial failure.

Question 3

Describe diastolic failure.

Answer 3

Diastolic heart failure is characterised by impaired relaxation and filling during diastole.

Common causes include hypertrophy, fibrosis, amyloidosis and constrictive pericarditis.

Question 4

Discuss cardiac hypertrophy.

Answer 4

Myocyte hypertrophy occurs due to chronic pressure or volume overload, and due to chronic tropic signals such as beta-adrenergic stimulation.

Hypertrophic myocytes are characterised by increased DNA ploidy, increased mitochondrial numbers and increased numbers of sarcomeres.

Although the muscle increases, the capillary bed does not. Together with interstitial matrix deposition this can result in myocardial injury and reduced compliance.

Question 5

Discuss the manifestations of left-sided heart failure.

Answer 5

• pulmonary congestion and oedema
• left atrial dilation with atrial fibrillation
• reduced renal perfusion, resulting in salt and water retention, ischaemic acute tubular necrosis and impaired waste excretion
• hypoxic encephalopathy

Question 6

Discuss the manifestations of right-sided heart failure.

Answer 6

• right atrial and ventricular dilation and hypertrophy;
• oedema;
• hepatomegaly with centrilobular congestion and atrophy, ultimately leading to centrilobular necrosis and fibrosis;
• splenomegaly; and
• renal congestion with hypoxic injury and marked acute tubular necrosis.

Question 7

Define ischaemic heart disease.

Answer 7

Ischaemic heart disease involves a mismatch between myocardial demand and oxygen delivery.

It is classically the result of insufficient blood supply due to narrowing of the coronary arteries. Atherosclerosis or vasospasm are common reasons.

Mismatch can also result from increased myocardial demand (eg. tachycardia, hypertrophy) or diminished oxygen delivery due to anaemia, shunting or carbon monoxide poisoning.