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 stent-graft (Sensorgraft) facing a sensor in fixed position (Sensorbox). Maximum inter-sensor variation of Sensorgraft and Sensorbox 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. Sensorgraft motion was measured by ultrasound. Measurements with Sensorgraft were compared to those with Sensorbox 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 microm and 210+/-0.93 microm, respectively. Measurements of Sensorgraft were higher than Sensorbox, 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 microm and 26 +/- 1.48 microm, 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.