First-Line RAAS Therapy
ACE inhibitors are the first-line therapy for targeting the renin-angiotensin-aldosterone system (RAAS) in most clinical scenarios, with ARBs serving as an equally effective alternative when ACE inhibitors are not tolerated. 1, 2
Evidence-Based Rationale
The 2017 ACC/AHA guidelines establish that ACE inhibitors remain first-line therapy for all patients with reduced ejection fraction and are broadly recommended for RAAS blockade in hypertension 1. This recommendation is supported by decades of outcome data demonstrating cardiovascular and renal protection.
When to Choose ACE Inhibitors vs ARBs
ACE inhibitors should be your default choice because:
- They have the most robust long-term mortality data across multiple cardiovascular conditions
- They are established as first-line for heart failure with reduced ejection fraction, post-MI, and chronic kidney disease 2
- They are generally less expensive and more widely available
Switch to ARBs when:
- ACE inhibitor-induced cough develops (occurs in 5-20% of patients)
- Angioedema occurs (absolute contraindication to ACE inhibitors)
- Patient specifically requires AF prevention, where ARBs show particular benefit 1
Clinical Application Algorithm
Start with an ACE inhibitor (e.g., lisinopril, enalapril, ramipril) for:
- Hypertension
- Heart failure with reduced ejection fraction
- Post-myocardial infarction
- Chronic kidney disease with proteinuria
- Diabetes with target organ damage
Use ARBs as first-line only when:
- Prior ACE inhibitor intolerance documented
- Atrial fibrillation prevention is a specific goal 1
Add mineralocorticoid receptor antagonists (MRAs) for dual RAAS blockade:
- Spironolactone or eplerenone combined with ACE inhibitor is preferred over ACE inhibitor + ARB combination 2
- This strategy provides superior outcomes in heart failure with fewer adverse events than ACE inhibitor + ARB combinations
Important Caveats
Avoid direct renin inhibitors (aliskiren) as first-line therapy - they show similar blood pressure reduction but more side effects compared to ACE inhibitors and ARBs, with no proven mortality benefit 3, 4. The evidence does not support their use over established agents.
Monitor carefully for:
- Hyperkalemia (especially when combining RAAS agents)
- Acute kidney injury (particularly in bilateral renal artery stenosis)
- Hypotension with initial dosing
The combination of ACE inhibitor + ARB is no longer recommended for most patients due to increased risk of hyperkalemia and worsening renal function without clear mortality benefit 4. If dual RAAS blockade is needed, prefer ACE inhibitor + MRA instead 2.
Special Populations
For renovascular hypertension with fibromuscular dysplasia: RAS blockers (ACE inhibitors or ARBs) are drugs of choice when angioplasty is not feasible, but require careful renal function monitoring 5.
For primary aldosteronism requiring medical therapy: MRAs (spironolactone 50-100 mg daily, titrated up to 300-400 mg if needed) become the primary RAAS-targeting agent 5.