Proof of concept study on coronary microvascular function in low flow low gradient aortic stenosis

Area of Science:

• Cardiology
• Vascular Biology
• Cardiac Surgery

Background:

• Aortic stenosis (AS) is a significant valvular heart disease.
• Coronary microvascular dysfunction (CMD) is increasingly recognized in AS.
• The relationship between AS subtypes and CMD requires further elucidation.

Purpose of the Study:

• To investigate the association between low flow low gradient aortic stenosis (LFLGAS) and coronary microvascular dysfunction (CMD).
• To compare the severity of CMD in LFLGAS versus normal-flow high-gradient aortic stenosis (NFHGAS).
• To determine the impact of CMD on cardiac performance and its recovery after transcatheter aortic valve implantation (TAVI).

Main Methods:

• Invasive assessment of CMD using index of microcirculatory resistance (IMR), resistive reserve ratio (RRR), and coronary flow reserve (CFR) in 41 severe AS patients.
• Measurement of cardiac function via speckle tracking echocardiography before and 6 months after TAVI.
• Comparison of microvascular and cardiac parameters between LFLGAS and NFHGAS groups.

Main Results:

• Patients with LFLGAS exhibited significantly higher IMR and lower RRR compared to NFHGAS patients, indicating more severe CMD.
• High IMR was correlated with reduced stroke volume index, cardiac output, and peak atrial longitudinal strain (PALS).
• TAVI did not significantly alter microvascular function or PALS, but improved left ventricular global longitudinal strain. LV systolic function recovery post-TAVI was observed only in LFLGAS patients with preserved microvascular function.

Conclusions:

• CMD is more severe in LFLGAS compared to NFHGAS.
• CMD in LFLGAS is associated with a low-flow state, left atrial dysfunction, and impaired cardiac performance.
• Microvascular function is a critical determinant of cardiac recovery following TAVI in LFLGAS patients.