A Novel Hydrodynamic Approach for the Evaluation of Microvascular Resistance during Provocative Spasm Testing

Figures

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  Fig. 1.. Schematics of the LAD and the coronary microcirculation and how they are modelled as two resistances in a series configuration, including the epicardial resistance, Repicardial, and microvascular resistance, Rmv. Pressure and velocity at the tip of the ComboWire are Pa and VA, respectively, and Pv indicates venous pressure.

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  Fig. 2.. The coronary arterial resistance of the LAD comprises the epicardial vessel and microcirculation. The resistance inside the LAD is shown from the location of ComboWire. The epicardial LAD resistance was less compared to the microcirculation resistance. It is assumed upon the presence of microvascular spasm, the microcirculation resistance increases considerably. LAD refers to the left anterior descending coronary artery, Ra is the proximal resistance, Repicardial and Rmv are the epicardial and microvascular resistances, respectively.

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  Fig. 3.. a ComboWire continuous pressure and flow velocity recordings with a 20-s window extracted for pre-ACh (b) and post-ACh (c).

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  Fig. 4.. Variation in the selected starting reference location to calculate the epicardial resistance for both pre-ACh (a) and post-ACh (b). The starting location shifts downstream by intervals of 10 mm compared to the chosen reference point. Table c tabulates the epicardial and microvascular resistances calculated based on different selected reference points.

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  Fig. 5.. Image mapping protocol applied to calculate the diameter and the length of LAD for two cases without (left column) and with (right column) epicardial spasm for both pre-ACh (top row) and post-ACh (bottom row).

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  Fig. 6.. The profiles of artery diameter for two cases without and with epicardial spasm at different locations from proximal to the ComboWire to the very distal aspect of the LAD for both pre-ACh (solid blue line) and post-ACh (dashed blue line). The right-hand-side vertical axis shows the changes in the diameter of the LAD at post-ACh compared to the pre-ACh (solid orange line).

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  Fig. 7.. A proposed flowchart to identify the presence of epicardial and/or microvascular spasms based on the levels of epicardial and microvascular resistances pre- and post-ACh.