L3.3 Cardiac failure

Question 1

Definition of cardiac failure

Answer 1

• when heart unable to pump sufficient blood to meet metabolic needs of body at normal filling pressures & normal venous return

Question 2

Consequence of myocardial dysfunction

Answer 2

• Normal function at rest
• Deficient function under stress
  
  • i.e. during exercise/↑temp/meals/infections/change in heart rates

Question 3

Phases of cardiac failure

Answer 3

Normal → dysfunction → failure → death

Question 4

What is the ejection fraction

Answer 4

• SV/EDV (normally ~50%)
• Predicts life expectancy

Question 5

Systolic ventricular failure

Answer 5

• Characterised by ↓ejection fraction

1. ↓SV (with normal EDV)
2. ↑LV ED VOLUME (less pumped - more remained)
3. Restoration of SV (but at a higher EDV)
4. ∴ Lower ejection fraction

Question 6

Diastolic ventricular failure characteristics

Answer 6

• Impaired filling at normal pressures
• ↓Ventricular compliance (need a higher pressure to fill)

Question 7

What is diastolic ventricular failure due to?

Answer 7

• Due to:
• Concentric hypertrophy (wall becomes stiffer)
  
  • By aortic stenosis & Systemic hypertension
• Pericardial constraint
  
  • By fibrosis (↓compliance) & fluid accumulation (↑pressure → heart cannot fill)

Question 8

Mechanism of diastolic ventricular failure

Answer 8

1. ↓diastolic distensibility
2. ↓SV
3. ↑LV ED PRESSURE
4. Restoration of SV (↑ in EDP overcomes distensibility → restore SV)
5. Normal ejection fracture (but ↑pressures in heart)

Question 9

Natural compensatory mechanisms

Answer 9

• Activation of SNS
• Activation of RAS
• ↑vasopressin
• ↑endothelin
• Ventricular dilation & hypertrophy
  
  • These all however ↑BP which causes more stress on heart than benefits

Question 10

ANP (good natural compensatory mechanism)

Answer 10

• ↑ANP (atrial natriuretic peptide) → acts on kidney to secrete H2O
  
  • Also acts against RAS

Question 11

Consequences of increased LV EDV

Answer 11

• ↑LA pressures (↓compliance as ventricule dilates)
• ↑pulmonary V & capillary pressure → causes pulmonary oedema
  
  • ↓ lung compliance → breathlessness (symptom)
  • Effusion
  • Wheeze
  • Cough with frothy sputum

Question 12

Consequences of increased RV EDV

Answer 12

• ↑RA pressures
• ↑jugular venous pressure
  
  • Hepatic congested (liver swells)
  • Tissue fluid accumulation (e.g. leg oedema)

Question 13

Treatment of cardiac failure

Answer 13

• ↑ cardiac contractility by ↓afterload (vasodilators, ↓P - i.e ↓fluid retention)
• Maintain normal heart rhythm & rate