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Published on: February 3, 2021
Index of Microcirculatory Resistance Measured during Intracoronary Adenosine-Induced Hyperemia
Irene Santos-Pardo1, Patrik Alström1, Nils Witt1
1Department of Clinical Science and Education, Karolinska Institute, Unit of Cardiology, Södersjukhuset, Stockholm 11883, Sweden.
Insights
Intracoronary (IC) adenosine effectively measures index of microcirculatory resistance (IMR) during hyperemia, showing high agreement with intravenous (IV) adenosine. This method offers a simpler, potentially less uncomfortable alternative for assessing coronary microvascular function.
Area of Science:
- Cardiology
- Vascular Physiology
- Medical Devices
Background:
- Index of microcirculatory resistance (IMR) is an invasive measure of coronary microvascular function.
- IMR calculation traditionally requires maximal hyperemia induced by intravenous (IV) adenosine.
- Evaluating intracoronary (IC) adenosine as an alternative for IMR calculation.
Purpose of the Study:
- To assess the feasibility and accuracy of using IC adenosine for IMR calculation.
- To compare IMR values obtained with IC adenosine versus IV adenosine.
- To determine if IC adenosine simplifies the assessment of coronary microvascular function.
Main Methods:
- 31 patients with stable coronary artery disease were enrolled.
- Coronary pressure and thermodilution measurements were taken at rest and during hyperemia.
- Duplicate IMR measurements were performed using both IC and IV adenosine, with a simplified saline bolus method also tested.
Main Results:
- IC and IV adenosine produced comparable dispersion of transit times.
- High agreement was observed between IMR values calculated using IC and IV adenosine (ICC=0.90).
- A simplified procedure using a single saline bolus did not significantly alter agreement or misclassification rates.
Conclusions:
- IC adenosine demonstrates excellent agreement with IV adenosine for IMR measurement.
- IC adenosine may offer a more convenient, time- and cost-effective method with reduced patient discomfort.
- This approach could facilitate invasive assessment of coronary microvascular function.
Background:
The index of microcirculatory resistance is an invasive measure of coronary microvascular function that has to be calculated during maximal hyperemia, classically achieved with intravenous adenosine (IV). The aim of this study was to evaluate the use of intracoronary (IC) adenosine for the calculation of IMR.
Methods And Results:
31 patients with stable coronary artery disease were included in the study. Coronary pressure and thermodilution measurements were obtained at rest and during maximal hyperemia using a pressure-temperature sensor-tipped coronary guidewire. Duplicate measurements were performed using first IC and then IV adenosine. Dispersion of transit times was comparable for IC and IV adenosine. IMR values based on IC vs IV adenosine showed a high level of agreement and an intraclass correlation coefficient of 0.90. Applying an upper normal limit of 25, misclassification of IMR using IC adenosine was seen in just one patient in whom IC adenosine resulted in a lower value. A simplified procedure based on a single bolus dose of saline did not change the level of agreement or the rate of misclassification.
Conclusions:
We found an excellent agreement between IMR values measured during hyperemia induced by IC as compared to IV adenosine. The use of IC adenosine may facilitate invasive assessment of microvascular function and is potentially time- and cost-saving with less patient discomfort as compared to IV infusion. The trail is registered with NCT03369184.
