Aneurysm sac pressure monitoring: Effect of pulsatile motion of the pressure sensor on the interpretation of measurements

Purpose: To determine the effect of pulsatile motion of graft-attached pressure sensors on the accuracy of aneurysm sac pressure measurement. Methods: Pressure inside a pressure box was measured with a sensor attached to a stentgraft (Sensor graft) facing a sensor in fixed position (Sensor box). Maximum inter-sensor variation of Sensor graft and Sensor box was determined in static experiments. Experiments with pulsatile circulation were performed with a compliant and a noncompliant stent-graft at 120/80 mmHg and 160/95 mmHg. Pressure measurements in the box were repeated after the box pressure was increased from 0 to 120 mmHg. Sensor graft motion was measured by ultrasound. Measurements with Sensor graft were compared to those with Sensor box using Pearson correlation coefficients to determine the concordance between the sensors. Results: The maximum inter-sensor variation was 4 mmHg. Increased box pressure induced progressive pulsatile graft and sensor motion during all experiments. During the experiments with the compliant graft at systemic pressures of 120/80 and 160/95 mmHg, the maximum inter-sensor variation was exceeded at box pressures of 65 and 75 mmHg, respectively. The sensor motion at these box pressures was 214±2.70 μm and 210±0.93 μm, respectively. Measurements of Sensor graft were higher than Sensor box, up to 13 mmHg at a box pressure of 120 mmHg. The Pearson correlation coefficients during these experiments were 0.99 and 1.00 (p<0.001), respectively. In the experiments with the noncompliant graft, the maximum inter-sensor variation was not exceeded, and sensor motion was only 7±0.46 μm and 26±1.48 μM, respectively. The Pearson correlation coefficient during these experiments was 1.00 (p<0.001). Conclusion: Pulsatile sensor motion can influence the accuracy of pressure measurement. More compliant grafts are more susceptible to this phenomenon. Despite false high pressure measurements, stent-graft-attached pressure sensors seem appropriate to follow pressure trends in the aneurysm sac.

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