Exploring the mechanisms responsible for reduced systolic function in high-gradient aortic stenosis.

Area of Science:

• Cardiology
• Cardiovascular Physiology
• Medical Imaging

Background:

• Severe aortic stenosis (AS) can lead to reduced ejection fraction (rEF), a condition impacting cardiac function.
• Understanding the underlying mechanics of rEF in high-gradient AS is crucial for patient management.

Purpose of the Study:

• To investigate the mechanical factors contributing to reduced ejection fraction in patients with high-gradient severe aortic stenosis.
• To differentiate between afterload-induced dysfunction and intrinsic myocardial impairment.

Main Methods:

• Echocardiography and MRI were used to assess aortic valve area, mean gradient, and myocardial fibrosis in 21 patients with severe AS.
• Load-independent pressure-volume hemodynamics were employed to evaluate intrinsic contractility.
• Patients were stratified into groups with reduced ejection fraction (rEF) and preserved ejection fraction (pEF).

Main Results:

• Patients with rEF exhibited higher end-systolic wall stress and valvuloarterial impedance, driven by more severe valvular stenosis.
• Intrinsic contractile function was similar between rEF and pEF groups, indicating preserved myocardial function.
• The rEF group presented with increased symptoms, higher pulmonary pressures, and greater myocardial fibrosis.

Conclusions:

• The primary cause of reduced ejection fraction in high-gradient AS is excessive afterload due to severe valve stenosis.
• Intrinsic cardiac contractility remains preserved, suggesting that afterload is the main determinant of systolic dysfunction.
• Increased myocardial fibrosis in the rEF group did not correlate with diminished muscle function.