Heart Failure

Question 1

Describe the pathophysiology of heart failure

Answer 1

Decreased CO
Decreased arterial blood pressure
Which causes increased sympathetic action leading to vasoconstriction. This increases after load as arteries are narrowed. Sympathetic action also increases Renin (leading to increased blood volume and so BP)
Increased venous BP from the blood back up increases the preload of the heart as well as from the renin. This increases the work the heart has to do and increases O2 demand of cardiac myocytes which causes more damage and leads to worsening heart failure.

Question 2

What drugs are used to treat heart failure and how do they help

Answer 2

1. Furosemide : loop diuretic so it blocks Na+/K+/2Cl- cotransporter in the loop of Henley. Lower conc of solutes in interstitial fluid of nephron so less water drawn out of filtrate and more urine produced. Less volume so less work for heart less O2 demand.
   Side effects: hypokalaemia, hypotension, AKI, urinary retention as high volume, hyperglycaemia, gout.
2. Ramipril: Ace inhibitor. This prevents angiotensin 1 to angiotensin 2 by ACEi in the lungs. Reduces aldosterone and so reduces vasoconstriction and water retention. Reduces blood volume reduced pressure on the heart reduces O2 demand.
3. Bisprolol: Beta blocker. Blocs sympathetic action on the heart. This slows HR and reduces work of heart.
4. Spironolactone: mineralocorticoid receptor antagonist which blocks aldosterone. Reduces blood volume and vasoconstriction. Reduces work of heart.
5. Losartan : only if Angiotensin receptor blocker only used if ACEi not tolerated. Stops AT1 to AT2.