Effects of HF

Heart Failure ➔ ↓ Cardiac Output

↓ CO ➔ ↑ HR ↑ contractility ↑

• Receptors detect ↓ BP ➔ release aromatic amines ➔ ↑ HR and contractility

• ↓ CO ➔ ↓ renal perfusion (↓ GFR) ➔ secretion of renin and activation of renin-angiotensin-aldosterone system (RAAS)

  • RAAS tries to ↑ CO by ↑ BP:

    • ↑ volume (reabsorbing salt and H2O follows)

    • vasoconstriction (↑ peripheral resistance)

  • This attempt to ↑ CO makes HF worse:

    • ↑ preload (from ↑ volume)

    • ↑ afterload (from vasoconstriction)

• RAAS self-regulates via feedback mechanisms (BNP counteracts the activation of RAAS)