Why are alpha-blockers, Calcium Channel Blockers (CCB), Angiotensin-Converting Enzyme inhibitors (ACEi) / Angiotensin Receptor Blockers (ARBs) relatively contraindicated in aortic stenosis?

From the Guidelines

Alpha-blockers, calcium channel blockers (CCBs), and angiotensin-converting enzyme inhibitors (ACEIs)/angiotensin receptor blockers (ARBs) are relatively contraindicated in aortic stenosis because they can precipitate hemodynamic collapse in these patients. These medications reduce systemic vascular resistance and can cause vasodilation, which is particularly dangerous in aortic stenosis where cardiac output is already limited by the fixed obstruction at the aortic valve. In aortic stenosis, the heart relies on adequate preload and afterload to maintain forward flow across the stenotic valve. Alpha-blockers (like doxazosin or prazosin) cause peripheral vasodilation, reducing venous return and blood pressure. CCBs (particularly dihydropyridines like amlodipine) cause arterial vasodilation, reducing afterload. ACEIs/ARBs (like lisinopril or losartan) cause both arterial and venous dilation. When these medications are used in patients with significant aortic stenosis, the resulting drop in blood pressure can lead to decreased coronary perfusion, myocardial ischemia, syncope, or even cardiogenic shock, as the heart cannot increase stroke volume to compensate for the reduced systemic vascular resistance due to the fixed outflow obstruction.

Key Points to Consider

• The use of vasodilators, including ACE inhibitors and ARBs, may cause substantial hypotension in patients with severe aortic stenosis and should only be used with great caution 1.
• Medical treatment should be optimized, but optimization of treatment should not delay surgical decision-making 1.
• Beta-blockers are generally preferred for blood pressure management in aortic stenosis as they have less impact on preload and afterload while reducing myocardial oxygen demand.

Clinical Implications

• In patients with aortic stenosis, careful consideration should be given to the use of alpha-blockers, CCBs, and ACEIs/ARBs due to the potential for hemodynamic collapse.
• If blood pressure management is necessary, beta-blockers are a safer option, but consultation or co-management with a cardiologist is preferred for hypertension management in patients with moderate or severe aortic stenosis 1.
• The management of aortic stenosis should prioritize the prevention of complications, such as decreased coronary perfusion, myocardial ischemia, syncope, or cardiogenic shock, and the optimization of treatment should be individualized based on the patient's specific condition and needs.

From the Research

Relative Contraindications of Alpha-blockers, CCB, ACEi, and ARBs in Aortic Stenosis

• Alpha-blockers, calcium channel blockers (CCB), angiotensin-converting enzyme inhibitors (ACEi), and angiotensin receptor blockers (ARBs) are relatively contraindicated in aortic stenosis due to their potential to exacerbate the condition 2, 3.
• The use of CCBs in patients with moderate or severe aortic stenosis has been associated with adverse effects on treadmill exercise and reduced survival 2.
• However, other studies have found that the use of CCBs in patients with severe aortic stenosis and hypertension is not associated with worse clinical outcomes, and may even lead to better prognosis in patients with coronary artery disease 4, 3.
• ACEi and ARBs are recommended as first-line treatments for hypertension, but their use in patients with aortic stenosis is debated due to concerns about their safety 5, 6.
• The selection of antihypertensive therapy in patients with aortic stenosis should be individualized, taking into account the patient's specific condition and comorbidities 5.

Mechanisms and Clinical Implications

• The mechanisms underlying the potential harmful effects of alpha-blockers, CCB, ACEi, and ARBs in aortic stenosis are not fully understood, but may be related to their effects on blood pressure, cardiac output, and valve function 2, 3.
• The clinical implications of these findings are that patients with aortic stenosis should be carefully monitored when receiving antihypertensive therapy, and alternative treatments should be considered if necessary 4, 5.
• Further research is needed to fully understand the effects of alpha-blockers, CCB, ACEi, and ARBs in patients with aortic stenosis and to develop evidence-based guidelines for their use in this population 2, 6.