Final answer:
Heart failure occurs when the heart cannot pump enough blood to meet the body's needs. It includes HFrEF (reduced ejection fraction) and HFpEF (preserved ejection fraction). The ACC/AHA classifies HF into four stages, and the RAAS plays a critical role in blood pressure and volume regulation.
Step-by-step explanation:
Heart failure is a chronic condition where the heart can't pump with sufficient force to transport oxygenated blood to all vital organs. There are two types of heart failure:
HFrEF (Heart Failure with reduced Ejection Fraction): This is when the heart muscle does not contract effectively, and less oxygen-rich blood is pumped out to the body.
HFpEF (Heart Failure with preserved Ejection Fraction): This occurs when the heart contracts normally but the ventricles do not relax properly during diastole, reducing the heart's capacity to fill with blood.
The ACC/AHA stages of heart failure are:
Stage A: High risk for developing HF without symptoms or structural heart disease.
Stage B: Structural heart disease but without signs or symptoms of HF.
Stage C: Structural heart disease with prior or current symptoms of HF.
Stage D: Refractory HF requiring specialized interventions.
The renin-angiotensin-aldosterone system (RAAS) is crucial for cardiovascular and fluid volume control. When blood pressure is low, the kidneys secrete renin, which converts angiotensinogen into angiotensin I. Angiotensin I is then converted to angiotensin II by ACE in the lungs. Angiotensin II is a potent vasoconstrictor that also stimulates aldosterone release, which leads to increased sodium and water retention, raising blood pressure and restoring fluid volume.