New Research Paper
Coronary
Comparison of Doppler Flow Velocity and Thermodilution Derived Indexes of Coronary Physiology

https://doi.org/10.1016/j.jcin.2022.03.015Get rights and content
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Abstract

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.

Key Words

coronary flow reserve
hyperemic microvascular resistance
index of microvascular resistance
microvascular dysfunction

Abbreviations and Acronyms

ACS
acute coronary syndrome
APV
average peak velocity
CCS
chronic coronary syndrome
CFR
coronary flow reserve
CFRDoppler
Doppler-derived coronary flow reserve
CFRthermo
thermodilution-derived coronary flow reserve
FFR
fractional flow reserve
hMR
hyperemic microvascular resistance
IMR
index of microvascular resistance
PET
positron emission tomography
ROC
receiver-operating characteristic
Tmn
mean transit time

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The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the Author Center.

Drs Demir and Boerhout contributed equally to this work.