Novel monorail infusion catheter for volumetric coronary blood flow measurement in humans: in vitro validation
Selected in EuroIntervention by S. Brugaletta
van 't Veer M, Adjedj J, Wijnbergen I, Tóth GG, Rutten MC, Barbato E, van Nunen LX, Pijls NH, De Bruyne B
EuroIntervention. 2016 Aug 20;12(6):701-7
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What is known
Quantitative measurement of volumetric coronary blood flow (ml/min) during catheterisation in humans is currently not possible. Surrogate methods, such as intracoronary Doppler, have high variability and are operator-dependent. In addition, normal values of coronary flow reserve vary considerably. Since microvascular resistance can be defined as the ratio between coronary pressure and flow, the lack of a reliable technique to measure volumetric coronary blood flow has hampered the quantitative assessment of the coronary microcirculation as well. Consequently, reliable data regarding microvascular dysfunction are limited. The present article validates a novel monorail infusion catheter that ensures complete and homogeneous mixing of saline with blood, and can be used as standard PCI equipment.
- Based on the principles of thermodilution, volumetric coronary flow can be determined from the flow rate of a continuous saline infusion, the temperature of saline when it enters the coronary artery, and the temperature of the blood mixed with the saline in the distal part of the coronary artery.
- In an in vitro set-up of the systemic and coronary circulation at body temperature, coronary flow values varied from 50-300 ml/min in steps of 50 ml/min.
- At each coronary flow value, thermodilution-based measurements were performed at infusion rates of 15, 20, and 30 ml/min. Temperatures and pressures were simultaneously measured with a pressure/temperature sensor-tipped guidewire. Agreement of the calculated flow and the measured flow as well as repeatability were assessed.
- A total of five catheters were tested, with a total of 180 measurements. A strong correlation (ρ=0.976, p<0.0001) and a difference of –6.5±15.5 ml/min were found between measured and calculated flow. The difference between two repeated measures was 0.2%±8.0%.
In vivo measurement of coronary flow has been of interest for years for every researcher, due to its strong correlation with patients’ prognosis. Unfortunately, it hasn't been possible to obtain a direct measurement and we managed to use some surrogate endpoints, such as Doppler indices or indirect evaluation of microvascular resistance. The present article opens an interesting door in this field, describing a new method for estimating coronary flow, through the use of a specifically designed for saline infusion microcatheter. The method is highly reproducible and operator-independent, which means that it may be applied worldwide by any operator, maintaining the same standardized results. A clinical validation, demonstrating a correlation between the flow so-obtained and clinical variables, is now needed in order to start using it as surrogate endpoint for studies focused on coronary microcirculation.