What is the role of beta-blockers (beta-adrenergic blocking agents) in managing thoracic aortic aneurysms?

Role of Beta-Blockers in Managing Thoracic Aortic Aneurysms

Beta-blockers are recommended as the preferred first-line antihypertensive agents in patients with thoracic aortic aneurysms to reduce the risk of aneurysm expansion, dissection, and rupture. 1

Mechanism and Benefits

Beta-blockers provide several protective effects in thoracic aortic aneurysms:

• Reduce heart rate and blood pressure, decreasing hemodynamic stress on the aortic wall
• Decrease the force of left ventricular ejection (dP/dt)
• Potentially slow the rate of aortic dilatation
• Reduce the risk of aortic dissection and rupture

Evidence-Based Recommendations

First-Line Therapy

• Beta-blockers are designated as Class I (Level of Evidence: C-EO) for patients with thoracic aortic aneurysms 1
• They are particularly well-studied in Marfan syndrome, where they have been shown to reduce the rate of aortic dilatation 1

Blood Pressure Targets

• Target blood pressure should be <140/90 mmHg in patients without diabetes 1
• Target blood pressure should be <130/80 mmHg in patients with diabetes or chronic renal disease 1
• Aim for the lowest tolerated blood pressure while maintaining adequate perfusion 1

Combination Therapy

For patients requiring additional blood pressure control:

1. Beta-blockers as foundation therapy
2. Consider adding ACE inhibitors or angiotensin receptor blockers (ARBs) 1
   • ARBs (particularly losartan) may provide additional benefit in Marfan syndrome 1
   • In the Jikei Heart Study, valsartan was associated with reduced incidence of aortic dissection 1

Special Considerations

Marfan Syndrome

• Beta-blockers are strongly recommended (Class I, Level of Evidence: B) for all patients with Marfan syndrome and aortic aneurysm 1
• Consider adding an ARB (losartan) as it may further slow aortic root dilatation 1

Monitoring

• Regular imaging surveillance is essential for all patients with thoracic aortic aneurysms
• For aneurysms 4.0-5.4 cm: imaging every 6-12 months 1
• For aneurysms <4.0 cm: imaging every 2-3 years 1

Surgical Considerations

• Surgical repair is indicated when aneurysm diameter reaches ≥5.5 cm 1
• Beta-blockers should be continued perioperatively in patients undergoing surgical repair 1

Limitations and Controversies

Despite widespread recommendation, some limitations exist:

• The evidence supporting beta-blocker therapy comes primarily from observational studies rather than large RCTs 1
• Some studies have questioned the consistent efficacy of beta-blockers in preventing aneurysm growth 2
• Recent research has focused on the potential role of the renin-angiotensin system in aneurysm development 3

Common Pitfalls

1. Inadequate dosing: Beta-blockers should be titrated to achieve target heart rate (50-60 bpm) for optimal effect
2. Inconsistent monitoring: Regular imaging surveillance is essential regardless of medical therapy
3. Monotherapy reliance: Consider combination therapy for optimal blood pressure control
4. Delayed surgical referral: Medical therapy should not delay surgical intervention when indicated

Beta-blockers remain the cornerstone of medical management for thoracic aortic aneurysms, with the strongest evidence supporting their use in patients with Marfan syndrome. While newer agents targeting the renin-angiotensin system show promise, beta-blockers continue to be recommended as first-line therapy by major cardiovascular guidelines.