L3.3 Cardiac failure Flashcards Preview

Cardio Phys > L3.3 Cardiac failure > Flashcards

Flashcards in L3.3 Cardiac failure Deck (13)
Loading flashcards...
1

Definition of cardiac failure

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

2

Consequence of myocardial dysfunction

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

3

Phases of cardiac failure 

Normal → dysfunction → failure → death

4

What is the ejection fraction

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

5

Systolic ventricular failure

  • 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

6

Diastolic ventricular failure characteristics

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

7

What is diastolic ventricular failure due to?

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

8

Mechanism of diastolic ventricular failure

  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)

9

Natural compensatory mechanisms

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

10

ANP (good natural compensatory mechanism)

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

11

Consequences of increased LV EDV

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

12

Consequences of increased RV EDV

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

13

Treatment of cardiac failure

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