Pressure-Sensing Catheter Centering Assembly for Accurate FFR
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Solution Overview
Problem
Current methods for assessing the severity of stenosis in blood vessels, such as fractional flow reserve (FFR) measurements, face challenges including inaccurate pressure readings, high manufacturing costs, and reduced precision due to factors like thermal variations and additional blockage caused by pressure-sensing devices, which complicate the determination of stenosis severity and guide treatment decisions.
Innovation Solution
A pressure-sensing catheter with a pressure sensor embedded in its wall, capable of smoothing the outer diameter and configured as a monorail or over-the-wire catheter, allows for precise measurement of pressure proximal and distal to a stenotic lesion, using an existing guidewire, and includes a centering assembly to accurately determine vessel size, enabling the calculation of a fractional flow reserve (FFR) that accounts for the catheter's impact on pressure measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pressure-sensing guidewire is used to measure pressure gradient across a lesion, then pressure measurements can be obtained, but the measurements suffer from drift, thermal variations, and reduced precision
Solution Approach 1:
The pressure sensor is extracted from the guidewire and placed in a separate sensor housing that can be positioned independently. This allows the sensing element to be isolated from the thermal and mechanical disturbances that affect guidewire-based measurements, thereby improving measurement precision and reliability.
Solution Approach 2:
A fluid-filled catheter system serves as an intermediary between the blood vessel and the pressure sensor. The fluid transmits pressure from the vessel to the sensor housed within the catheter, isolating the sensor from direct exposure to thermal variations and mechanical drift while maintaining accurate pressure transmission.
2Measurement precision
If a small catheter connected to a blood pressure sensor is used, then pressure measurements can be obtained, but the catheter and sensor housing create additional blockage to blood flow
Solution Approach 1:
The catheter incorporates an expandable centering assembly that can dynamically adjust its configuration. When not in use, the assembly remains compact to minimize flow obstruction. When positioning is required, it expands to center the catheter in the vessel, providing measurement capability without permanent flow restriction.
Solution Approach 2:
The catheter is divided into functional segments: a distal sensing portion with minimal obstruction for pressure measurement, and a proximal portion containing the sensor housing and centering assembly. This segmentation allows the measurement function to be separated from the structural support functions, reducing the overall impact on blood flow while maintaining measurement capability.
3Ease of operation
If pressure sensor is embedded within guidewire, then pressure measurements can be taken, but manufacturing costs increase and repositioning is time-consuming
Solution Approach 1:
The catheter system is designed to perform multiple functions: it can measure pressure at multiple locations, accommodate different guidewire configurations, and provide centering capability. This multi-functionality eliminates the need for specialized pressure-sensing guidewires and reduces the need for repeated repositioning operations.
Solution Approach 2:
The catheter incorporates an automatic centering mechanism that self-adjusts to center the catheter in the vessel using the expandable assembly. This self-centering capability eliminates the need for manual repositioning and operator intervention, thereby reducing time loss and improving ease of operation.
4Device complexity
If FFR calculation does not account for catheter size, then calculation is simpler, but measurement accuracy is reduced
Solution Approach 1:
The system incorporates feedback by using the centering assembly to determine vessel size and then using that information to calculate an offset correlation. This offset is fed back into the FFR calculation to compensate for catheter size effects, thereby improving accuracy without requiring complex manual adjustments.
Solution Approach 2:
The FFR calculation methodology is modified to include vessel size and catheter size as additional parameters. By changing the calculation parameters to account for physical dimensions, the system achieves higher accuracy while maintaining computational simplicity through automated processing.
Data Source
AI summary
An apparatus for assessing the severity of stenosis in a blood vessel includes an elongate body including a distal portion and a centering assembly. The centering assembly is actuatable to selectively center the elongate body in the vessel. A pressure sensor is disposed adjacent the centering assembly and is configured to detect fluid pressure in the vessel. A processing system receives the measured pressure from the pressure sensor, receives data representing the cross-sectional area of the vessel, receives data representing the size of the distal portion, calculates a offset correlation based on the size of the distal portion and based on the size of the vessel, and calculates a fractional flow reserve (FFR) for the vessel as an index of stenosis severity taking into account the offset correlation and the measured fluid pressure from the pressure sensor.