The body has mechanisms for ensuring adequate blood flow to the brain and to the heart. These compensations result in decreased blood flow to the kidneys. Decreasing the blood flow to the kidneys is dangerous, and a vicious cycle that worsens the heart failure.
Due to the decreased filtration, more volume backs up in the body, and this increases the pressure in the veins, which raises the hydrostatic pressure in the capillaries (blood is trying to get through but theres too much blood on the venous side of the capillary), leading to leakage into the interstitial fluid space = EDEMA, which is a hallmark symptom of heart failure.
The reduced blood flow also activates the renin angiotensin aldosterone system, since aldosterone will retain more Na+ and water to fill the vasculature and constrict the vasculature to ATTEMPT TO INCREASE the renal pressure.
The decrease in blood pressure will also activate the sympathetic nervous system, to try to stimulate the heart and constrict the vasculature.
The secretion of vasopressin is also increased in order to stimulate water reabsorption and constrict the vasculature.
In case that was not enough, endothelin, a vasoconstrictor, is also produced in greater quantities.
Keep these pathophysiological changes in mind in order to justify drug therapy that targets each of these facts.
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