Improved pressure-frequency sensing subxiphoid pericardial access system: performance characteristics during in vivo testing.

We have designed, synthesized, and tested an improved version of our original subxiphoid access system intended to facilitate epicardial electrophysiology. The new version of the system incorporates a precision fiber-optic pressure sensor and a novel signal analysis algorithm for identifying pressure-frequency signatures which, in the clinical setting, may allow for safer access to the pericardial space. Following in vivo studies on ten adult canine models, we analyzed 215 pressure-frequency measurements made at the distal tip of the access needle, of which 98 were from nonpericardial, 112 were from pericardial, and five were from ventricular locations. The needle locations as identified by the algorithm were significantly different from each other (p < 0.01), and the algorithm had improved performance when compared to a standard fast Fourier transform (FFT) analysis of the same data. Moreover, the structure of the algorithm can potentially overcome the time lags intrinsic to FFT analysis such that the needle's location can be determined in near-real time. Hydrodynamic pressure-frequency measurements made during traversal of the pericardial membrane revealed a distinct change in signal structure between the pericardial and nonpericardial anatomy. We present and discuss the design principles, details of construction, and performance characteristics of this system.