Continuous infusion thermodilution for assessment of coronary flow: Theoretical background and in vitro validation

van’t Veer, Marcel; Geven, Maartje C.F.; Rutten, Marcel C.M.; van der Horst, Arjen; Aarnoudse, Wilbert H.; Pijls, Nico H.J.; van de Vosse, Frans N.

doi:10.1016/j.medengphy.2009.01.006

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Volume 31, Issue 6 , Pages 688-694, July 2009

Continuous infusion thermodilution for assessment of coronary flow: Theoretical background and in vitro validation

Marcel van’t Veer
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
- Department of Cardiology, Catharina Hospital, Eindhoven, The Netherlands
- Both authors contributed equally to the study.
- Corresponding author at: Department of Cardiology, Catharina Hospital, Eindhoven, The Netherlands. Tel.: +31 402397004; fax: +31 402464837.
Maartje C.F. Geven
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
- Both authors contributed equally to the study.
Marcel C.M. Rutten
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
Arjen van der Horst
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
Wilbert H. Aarnoudse
- Department of Cardiology, Catharina Hospital, Eindhoven, The Netherlands
Nico H.J. Pijls
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands
- Department of Cardiology, Catharina Hospital, Eindhoven, The Netherlands
Frans N. van de Vosse
- Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands

Received 30 June 2008; received in revised form 23 January 2009; accepted 25 January 2009. published online 24 February 2009.

Abstract

Direct volumetric assessment of coronary flow during cardiac catheterization has not been available so far. In the current study continuous infusion thermodilution, a method based on continuous infusion of saline into a selective coronary artery is evaluated. Theoretically, volumetric flow can be calculated from the known infusion rate (Q_i), the temperatures of the blood (T_b), the saline (T_i), and the mixture downstream to the infusion site (T). We aimed to validate and optimize the measurement method in an in vitro model of the coronary circulation. Full mixing of infusate and blood was found to be the main prerequisite for accurate determination of the coronary flow. To achieve full mixing the influence of catheter design, infusion rate, and location of temperature measurement were assessed.

We found that continuous infusion thermodilution slightly overestimated coronary flow determined by directly measured reference flow by 7±8%, over the entire physiological flow range of 50–250ml/min. These results were found using a specially designed infusion catheter (infusion mainly through distally located sideholes), a high enough infusion rate (25ml/min), and measurement of the mixing temperature between 5 and 8cm distal from the tip of the infusion catheter.

Absolute coronary flow rate can be measured reliably by the continuous infusion method when full mixing is present, under the conditions mentioned above.

Keywords: In vitro model, Coronary circulation, Coronary physiology, Coronary flow, Thermodilution