Heart Failure Quiz

See Pathophysiology. Option C is correct because aldosterone is a hormone that acts on the kidney to make it reabsorb sodium, and because water follows sodium, the body retains water too. In heart failure the pumping heart delivers less blood to the kidneys, and the kidneys respond as if the body were short of volume. This activates the renin-angiotensin-aldosterone system (RAAS), a hormone chain that ends with the release of aldosterone. The result is sodium and water retention and a larger circulating volume. This is a sensible short-term response, because a bigger volume can restore blood pressure and organ perfusion. In a failing heart, however, the extra volume raises preload (the filling pressure) and, together with vasoconstriction from angiotensin II, afterload (the resistance), so it adds to the workload of an already weak heart. This is why drugs that block the system, such as ACE inhibitors and mineralocorticoid receptor antagonists (MRAs, which block the action of aldosterone), are used to treat heart failure.

• Hormone: Aldosterone makes the kidney reabsorb sodium, and water follows.
• Trigger: Less blood reaching the kidneys in heart failure activates the renin-angiotensin-aldosterone system.
• Effect: Sodium and water retention raises circulating volume, preload and afterload, adding to the workload.
• Treatment: ACE inhibitors and mineralocorticoid receptor antagonists block this system.