Simultaneous Noninvasive Assessment of Systemic and Coronary Endothelial Function

Area of Science:

• Cardiovascular Imaging
• Vascular Physiology
• Noninvasive Diagnostics

Background:

• Endothelial function is crucial for vascular health; dysfunction predicts coronary events.
• Nitric oxide (NO)-mediated coronary artery endothelial function can be assessed noninvasively using MRI during isometric handgrip exercise (IHE).
• The internal mammary artery (IMA) is visible during coronary MRI, enabling simultaneous assessment of systemic and coronary endothelial function.

Purpose of the Study:

• To propose and validate a noninvasive MRI strategy for simultaneously assessing systemic and coronary endothelial function during IHE.
• To evaluate the role of nitric oxide in the IMA response to IHE.
• To compare endothelial function between healthy subjects and patients with coronary artery disease (CAD).

Main Methods:

• Utilized 3T MRI to assess cross-sectional area and blood flow changes in the right coronary artery and IMA during IHE in 25 CAD patients and 26 healthy subjects.
• Administered a nitric oxide synthase inhibitor (monomethyl-l-arginine) in 8 healthy subjects to determine NO's role in IMA response.
• Assessed interobserver reproducibility for IMA cross-sectional area and blood flow measurements during IHE.

Main Results:

• IMA cross-sectional area and blood flow increased in healthy subjects during IHE, an effect significantly reduced by NO inhibition.
• In CAD patients, the right coronary artery showed no dilation, and IMA dilation was significantly less compared to healthy subjects.
• Blood flow responses to IHE were significantly reduced in both coronary and IMA in CAD patients compared to healthy controls.

Conclusions:

• MRI-assessed IMA responses to IHE reflect NO-dependent endothelial function and are reproducible.
• Endothelial function is reduced in both coronary and systemic arteries of CAD patients.
• This noninvasive MRI technique allows simultaneous measurement of coronary and systemic endothelial function, providing novel insights into vascular health.