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Comparison of Doppler Flow Velocity and Thermodilution Derived Indexes of Coronary Physiology
Ozan M Demir1, Coen K M Boerhout2, Guus A de Waard3
1British Heart Foundation Centre of Excellence and National Institute for Health Research Biomedical Research Centre at the School of Cardiovascular Medicine and Sciences, King's College London, London, United Kingdom.
Insights
Coronary flow reserve (CFR) measured by thermodilution overestimates Doppler-derived CFR. A thermodilution threshold of 2.5 provides better accuracy for diagnosing reduced coronary flow reserve than the commonly used 2.0 threshold.
Area of Science:
- Cardiology
- Medical Imaging
- Hemodynamics
Background:
- Coronary flow reserve (CFR) is crucial for assessing myocardial perfusion.
- Doppler-derived CFR measurements are common, but their correlation with thermodilution is unclear.
- Diagnostic thresholds for CFR require validation across different measurement techniques.
Purpose of the Study:
- To compare Doppler flow velocity and thermodilution-derived indexes for CFR measurement.
- To establish optimal thermodilution-based diagnostic thresholds for CFR.
- To evaluate the correlation between Doppler and thermodilution-derived microvascular resistance.
Main Methods:
- An international multicenter registry collected data from patients undergoing both Doppler and thermodilution CFR measurements.
- Physiological data from 250 vessels in 149 patients were analyzed.
- Correlation and agreement analyses were performed, including Bland-Altman analysis.
Main Results:
- A modest correlation (r²=0.36) was found between thermodilution-derived CFR (CFRthermo) and Doppler-derived CFR (CFRDoppler).
- CFRthermo overestimated CFRDoppler (mean bias 0.59).
- A CFRthermo threshold of 2.5 showed better sensitivity (75.5%) and specificity (81.3%) than the common threshold of 2.0 for predicting CFRDoppler < 2.5. Microvascular resistance indexes showed weak correlation.
Conclusions:
- Thermodilution-derived CFR overestimates Doppler-derived CFR, with only a modest correlation between the two methods.
- The standard thermodilution CFR threshold of 2.0 has low sensitivity for detecting reduced CFR.
- A thermodilution threshold of 2.5 offers improved diagnostic accuracy for assessing coronary flow reserve.
Objectives:
The aim of this study was to compare Doppler flow velocity and thermodilution-derived indexes and to determine the optimal thermodilution-based diagnostic thresholds for coronary flow reserve (CFR).
Background:
The majority of clinical data and diagnostic thresholds for flow-based indexes are derived from Doppler measurements, and correspondence with thermodilution-derived indices remain unclear.
Methods:
An international multicenter registry was conducted among patients who had coronary flow measurements using both Doppler and thermodilution techniques in the same vessel and during the same procedure.
Results:
Physiological data from 250 vessels (in 149 patients) were included in the study. A modest correlation was found between thermodilution-derived CFR (CFRthermo) and Doppler-derived CFR (CFRDoppler) (r2 = 0.36; P < 0.0001). CFRthermo overestimated CFRDoppler (mean 2.59 ± 1.46 vs 2.05 ± 0.89; P < 0.0001; mean bias 0.59 ± 1.24 by Bland-Altman analysis), the relationship being described by the equation CFRthermo = 1.04 × CFRDoppler + 0.50. The commonly used dichotomous CFRthermo threshold of 2.0 had poor sensitivity at predicting a CFRDoppler value <2.5. The optimal CFRthermo threshold was 2.5 (sensitivity 75.54%, specificity 81.25%). There was only a weak correlation between hyperemic microvascular resistance and index of microvascular resistance (r2 = 0.19; P < 0.0001), due largely to variation in the measurement of flow by each modality. Forty-four percent of patients were discordantly classified as having abnormal microvascular resistance by hyperemic microvascular resistance (≥2.5 mm Hg · cm-1 · s) and index of microvascular resistance (≥25).
Conclusions:
CFR calculated by thermodilution overestimates Doppler-derived CFR, while both parameters show modest correlation. The commonly used CFRthermo threshold of 2.0 has poor sensitivity for identifying vessels with diminished CFR, but using the same binary diagnostic threshold as for Doppler (<2.5) yields reasonable diagnostic accuracy. There was only a weak correlation between microvascular resistance indexes assessed by the 2 modalities.
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