Continuous Thermodilution Method to Assess Coronary Flow Reserve.

Area of Science:

• Cardiology
• Physiology
• Medical Devices

Background:

• Coronary flow reserve (CFR) is crucial for clinical risk stratification.
• Invasive CFR assessment traditionally uses Doppler or thermodilution with saline boluses (CFR_thermo-bolus).
• Continuous thermodilution offers a novel, operator-independent method for quantifying absolute coronary flow (AF).

Purpose of the Study:

• To evaluate the feasibility of continuous thermodilution for quantifying resting AF.
• To determine CFR using continuous thermodilution (CFR_{Thermo-infusion}).
• To compare CFR_{Thermo-infusion} with CFR_thermo-bolus.

Main Methods:

• Sixty-two patients with suspected coronary disease underwent invasive assessment.
• Absolute coronary flow (AF) was measured at maximal hyperemia (20 mL/min) and varying infusion rates (6-12 mL/min) using a dedicated catheter and temperature/pressure guidewire.
• Resting AF was determined at 10 mL/min infusion, and hyperemic AF at 20 mL/min; CFR_{Thermo-infusion} was calculated as their ratio.

Main Results:

• Continuous thermodilution confirmed hyperemia at 12 mL/min infusion, with adequate curve tracings at 10 mL/min for resting AF assessment.
• Mean CFR_{Thermo-infusion} was 2.56 ± 0.9, closely correlating with CFR_thermo-bolus (2.49 ± 1; r=0.76, p<0.001).
• High intraclass agreement (ICC=0.76, p<0.001) was observed between the two CFR measurement methods.

Conclusions:

• Continuous thermodilution is a feasible method for quantifying resting absolute coronary flow.
• This technique provides a novel clinical tool for determining coronary flow reserve.
• CFR_{Thermo-infusion} demonstrates good correlation and agreement with the established CFR_thermo-bolus method.