The Official Journal of EuroPCR and the European Association of Percutaneous Coronary Interventions (EAPCI)

Normal Values of Thermodilution-Derived Absolute Coronary Blood Flow and Microvascular Resistance in Humans

DOI: 10.4244/EIJ-D-20-00684

1. Cardiovascular Centre Aalst, OLV Clinic, Aalst, Belgium
2.Lausanne University Centre Hospital, Lausanne, Switzerland.  
3.Advanced Biomedical Sciences, University of Naples Federico II, Italy
4. Department of Cardiology, Catharina Hospital Eindhoven, The Netherlands 
5.Department of Biomedical Engineering Eindhoven University of Technology, Eindhoven, The Netherlands 

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Absolute hyperemic coronary blood flow (Q, in mL/min) and resistance (R, in Woods Units, WU) can be measured invasively by continuous thermodilution. The aim of this study was to assess normal reference values of Q and R.  

Methods and Results:

In 177 arteries (69 patients: 25 controls i.e. without identifiable coronary atherosclerosis; 44 patients with mild, non-obstructive atherosclerosis), thermodilution-derived hyperemic Q and total, epicardial, and microvascular absolute resistances (Rtot, Repi, and Rmicro) were measured. In 20 controls and 29 patients measurements were obtained in all 3 major coronary arteries,thus allowing calculations of Q and R for the whole heart. In 15 controls (41 vessels) and 25 patients (71 vessels),vessel-specific myocardial mass was derived from coronary computed tomography angiography.

Whole heart hyperemic Q tended to be higher in controls  compared to patients (668±185 vs 582±138 mL/min,p=0.068). In the left anterior descending coronary artery (LAD), hyperemic Q was significantly higher (293±102 mL/min versus 228±71 mL/min,p=0.004) in controls than in patients . This was mainly driven by a difference in Repi  (43±23 vs 83±41 WU, p=0.048),without significant differences in Rmicro. After adjustment for vessels-specific myocardial mass, hyperemic Q was similar in the 3 vascular territories (5.9±1.9,4.9±1.7,and 5.3±2.1 mL/min/g,p=0.44,in the LAD, left circumflex and right coronary artery,respectively).

The present report provides reference values of absolute coronary hyperemic Q and R. Q was homogeneously distributed in the 3 major myocardial territories  but the large ranges of observed hyperemic values of flow and and of microvascular resistance preclude their clinical use for interpatient comparison.  


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