Heart Failure

Question 1

Define heart failure

Answer 1

Heart is unable to produce sufficient output to meet the demands of the body

Question 2

Define acute heart failure

Answer 2

Decompensation of the heart due to chronic disease

Question 3

Define chronic heart failure

Answer 3

Congestie heart failure

Question 4

What are the 5 mechanisms of heart failure?

Answer 4

1. Inability of heart to expand (filling failure)
2. Damage to myocardium (pump failure)
3. Increased resistance to outflow (output failure)
4. Valvular defects
5. Irregular rhythms (conduction problem)

Question 5

Describe the processes that can lead to acute HF

Answer 5

• Volume overload can lead to pulmonary OR systemic congestion
• There is decreased CO, cardiogenic shock - leading to congestive HF
• Results in sudden death

Question 6

Describe the processes that can lead to congestive HF

Answer 6

• Failure to empty venous return leading to congestion and oedema
• Gradual dysfunction of myocardial pump or myocardial damage leading to volume or pressure overload

Question 7

What are the clinical signs of R sided HF?

Answer 7

• Congested mucous membranes
• Peripheral oedema
• Congested liver

Question 8

What are the clinical signs of L sided HF?

Answer 8

• Pulmonary oedema
• Dyspnoea
• Coughing
• Mucosal pallor

Question 9

What are the bodies responses to cardiac failure?

Answer 9

• Intrinsic cardiac repsonses - hypertrophy and cardiac dilation to increase heart rate
• Neuroendocrine - symp. increases heart rate and CO. RAAS, increases water and Na retention to increase preload (BV). Thromboxane and endothelin, vasocondtriction to increase BP

Question 10

Define cor pulmonae

Answer 10

R sided heart failure secondary to pulmonary hypertension caused by pulmonary disease (pulmonary oedema, pneumonia, COPD etc.) or vascular disease (pulmonary thromboembolism, dirofilariasis).

Get cardiac dilation and hypertrophy, heart tries but fails to pump blood to lungs.

Question 11

List 4 diseases of the pericardium

Answer 11

1. Bovine reticulopericarditis
2. Haemopericardium - blood accumulation in pericardial sac; atrial rupture (haemangiosarcoma) or aortic rupture in horses
3. Hydropericardium - oedematous fluid in pericardial sac; transudate (HF or neoplasia); modified transudate (Mulberry disease in pigs, Se/Vit E deficiency)
4. Pericardial hernia

Question 12

Define cardiac tamponade

Answer 12

Cardiac compresssion due to fluid accumulation in the pericardial sac. If acute can cause sudden death. If chronic, get gradual accumulation of fluid, constrictive pericarditis and tissue herniation.

Question 13

What can cause inherited conduction disorders?

Answer 13

Mutations in genes coding for cytoskeletal proteins, sarcomeric proteins and ion channels.

Question 14

Define conduction disorder and describe primary and secondary conduction disorders

Answer 14

Conduction disorder - abnormality in the conduction pathways of the SAN, AVN, bundle of HIS and purkinje fibres which results in arrthymia.

• Primary CD - no morphological abnormality, considered normal in some species e.g. horse
• Secondary CD - secondary to underlying disease e.g. atrial fibrillation in cardiomyopathies, ventricular tachycardia in ventricular hypertrophy

Question 15

Describe sick sinus syndrome

Answer 15

• Involves SAN +/- AVN and bundle of HIS
• Potentially life threatening
• Ventricular standstill and paroxysms of supraventricular tachycardia - syncope (temporary loss of consciousness due to cerebral hypoperfusion)
• Usually idiopathic - ischaemia/fibrosis of SAN

Question 16

What is the significance of 1st, 2nd and 3rd degree heart blocks?

Answer 16

1st degree - delay of impulse through AVN

2nd degree - intermittent failure to conduct through AVN, dropped beats

3rd degree - complete block of conduction