Continuous vs Bolus Thermodilution to Assess Microvascular Resistance Reserve

Area of Science:

• Cardiology
• Physiology
• Medical Imaging

Background:

• Coronary flow reserve (CFR) and microvascular resistance reserve (MRR) are crucial indicators of coronary microvascular function.
• These parameters can be derived using various methods that assess coronary blood flow.

Purpose of the Study:

• To compare the accuracy and reliability of CFR and MRR measurements obtained via continuous versus bolus thermodilution techniques.
• To evaluate the test-retest reliability of both continuous (CFR_cont, MRR_cont) and bolus (CFR_bolus, MRR_bolus) thermodilution methods.

Main Methods:

• A study involving 175 patients with chest pain and nonobstructive coronary artery disease.
• Simultaneous bolus and continuous thermodilution measurements were performed in the left anterior descending coronary artery.
• MRR was calculated using CFR, fractional flow reserve, and systemic pressure adjustments; test-retest reliability was assessed in 102 patients.

Main Results:

• Continuous thermodilution yielded significantly lower mean values for both CFR (2.67 ± 0.81) and MRR (3.22 ± 1.02) compared to bolus thermodilution (CFR: 3.47 ± 1.42; MRR: 4.40 ± 1.99).
• A significant but weak correlation was observed between CFR and MRR values derived from both methods (r ≈ 0.26-0.28).
• Continuous thermodilution demonstrated superior precision, with a nearly 3-fold lower repeatability coefficient for both CFR and MRR compared to bolus thermodilution.

Conclusions:

• Continuous thermodilution offers a more precise and reliable method for assessing CFR and MRR in patients with nonobstructive coronary artery disease.
• While yielding lower values, continuous thermodilution significantly reduces measurement variability, enhancing the diagnostic utility of these indices.
• The findings suggest continuous thermodilution is preferable for consistent and reproducible evaluation of coronary microvascular function.