The renin-angiotensin-aldosterone system (RAAS) plays a crucial role in heart failure. It regulates blood pressure and fluid balance, but its overactivation can worsen heart failure symptoms by promoting vasoconstriction and fluid retention.

Drugs targeting the RAAS, like ACE inhibitors, ARBs, and aldosterone antagonists, are key in heart failure treatment. These medications help improve symptoms, reduce hospitalizations, and increase survival rates by blocking various steps in the RAAS cascade.

Renin-Angiotensin-Aldosterone System (RAAS) Drugs in Heart Failure Treatment

Renin-angiotensin-aldosterone system in heart failure

• RAAS activation contributes to the pathophysiology of heart failure by promoting vasoconstriction, sodium and water retention, and ventricular remodeling
• Increased renin secretion from the kidneys leads to the formation of angiotensin II, a potent vasoconstrictor that stimulates aldosterone release from the adrenal glands
• Aldosterone promotes sodium and water reabsorption in the kidneys, leading to increased blood volume and preload on the failing heart
• Chronic RAAS activation results in progressive deterioration of cardiac function and worsening of heart failure symptoms (dyspnea, edema, fatigue)

Blood Pressure Regulation and Fluid Homeostasis

• The RAAS plays a crucial role in maintaining blood pressure and fluid balance
• The juxtaglomerular apparatus in the kidneys senses changes in blood pressure and initiates the RAAS cascade
• Angiotensinogen, produced by the liver, is converted to angiotensin I by renin
• Angiotensin converting enzyme (ACE) transforms angiotensin I into angiotensin II
• A negative feedback loop helps regulate the system, preventing excessive activation

ACE inhibitors and ARBs for heart failure

• ACE inhibitors (captopril, enalapril, lisinopril) block the conversion of angiotensin I to angiotensin II, reducing vasoconstriction and aldosterone secretion
  • Improve symptoms, reduce hospitalization rates, and prolong survival in patients with heart failure
  • Side effects include hypotension, hyperkalemia, cough, angioedema, and renal dysfunction
  • Interact with potassium supplements, potassium-sparing diuretics, and NSAIDs
• ARBs (losartan, valsartan, candesartan) block the effects of angiotensin II at AT1 receptors, providing similar benefits to ACE inhibitors
  • Alternative for patients intolerant to ACE inhibitor-induced cough
  • Side effects and drug interactions are similar to ACE inhibitors
• Aldosterone antagonists (spironolactone, eplerenone) block the effects of aldosterone at mineralocorticoid receptors, reducing sodium and water retention
  • Improve symptoms and survival in patients with severe heart failure when added to ACE inhibitors or ARBs
  • Require close monitoring for hyperkalemia and renal dysfunction
• Combination therapy with an ACE inhibitor and ARB or aldosterone antagonist provides more comprehensive RAAS blockade but increases the risk of adverse effects

Nursing considerations for RAAS medications

• Assess blood pressure, heart rate, and renal function (serum creatinine, eGFR) before initiating therapy and periodically during treatment
• Monitor serum potassium levels, especially in patients receiving aldosterone antagonists or combination therapy
• Educate patients about the importance of adhering to prescribed dosing schedules and not discontinuing medications without consulting a healthcare provider
• Instruct patients to report signs and symptoms of hypotension (dizziness, lightheadedness, fainting) or angioedema (swelling of the face, lips, tongue, or throat)
• Advise patients to avoid potassium supplements and salt substitutes unless prescribed by a healthcare provider
• Encourage patients to maintain a low-sodium diet ($<$ 2 g/day) and engage in regular physical activity as tolerated
• Collaborate with healthcare providers to adjust medication dosages based on patient response and laboratory values

Patient education for RAAS-targeting drugs

1. Explain the purpose and benefits of the prescribed medication in managing heart failure symptoms and improving long-term outcomes
2. Discuss the importance of taking medications as directed and not discontinuing therapy without consulting a healthcare provider
3. Teach patients how to monitor their blood pressure and heart rate at home using an automated device and keep a log of readings
4. Advise patients to rise slowly from sitting or lying positions to prevent orthostatic hypotension and falls
5. Instruct patients to report any side effects, such as persistent cough (ACE inhibitors), swelling (angioedema), or difficulty breathing, to their healthcare provider promptly
6. Emphasize the significance of regular follow-up appointments and laboratory tests to monitor therapy effectiveness and detect potential adverse effects
7. Provide written materials and resources for additional information and support, such as heart failure education booklets or reliable online sources
8. Encourage patients to adopt a heart-healthy lifestyle, including a low-sodium diet, regular exercise, stress management techniques, and smoking cessation