In‐vitro comparison of sensors and amplifiers to measure left ventricular pressure in mice

Abstract

Several companies market catheters to measure left ventricular (LV) pressure in mice, and it is often assumed that all sensors are similar, but there may be important differences in fidelity, stability, and immunity to noise and artifacts. We used an electronic signal generator, a dynamic pressure generator, and a laboratory scale to measure the frequency and step responses, immersion response, stability, accuracy, linearity, and sensitivity to side forces of amplifiers and 4 solid‐state sensors each from Millar, Scisense, and RADI. All sensors were stable after immersion with drifts of <1 mmHg/hr over 5 hrs, had flat frequency responses to >1 kHz, and were accurate and linear to within ±2 mmHg from 0‐300 mmHg. The amplifiers from Millar, Scisense, and RADI had time delays of 0.2, 3.2 and 10.6 ms; rise times of 300, 50, and 250 mmHg/ms; and 6 dB‐down frequency responses of 1200, 300, and 600 Hz respectively. The Scisense (but none of the other) catheters showed a 5.3 mmHg/g response to lateral forces applied to the sensor tip. Given that all of these semi‐rigid catheters straighten the normally curved vascular path upon insertion, the dynamic cardiac forces could generate significant "pressure" signals. We conclude that there are significant differences in solid‐state mouse pressure sensors and amplifiers which could generate unrecognized offsets, time delays, and distortions of raw signals and derivatives in‐vivo.