Use of a pressure wire for automatically correcting artifacts in phasic pressure tracings from a fluid-filled catheter

Background/purpose: Matching phasic pressure tracings between a
fluid-filled catheter and high-fidelity pressure wire has received limited
attention, although each part contributes half of the information to
clinical decisions. We aimed to study the impact of a novel and automated
method for improving the phasic calibration of a fluid-filled catheter by
accounting for its oscillatory behavior.   Methods/materials:
Retrospective analysis of drift check tracings was performed using our
algorithm that corrects for mean difference (offset), temporal delays
(timing), differential sensitivity of the manifold transducer and pressure
wire sensor (gain), and the oscillatory behavior of the fluid-filled
catheter described by its resonant frequency and damping factor (how
quickly oscillations disappear after a change in pressure).  
Results: Among 2886 cases, correcting for oscillations showed a large
improvement in 28% and a medium improvement in 41% (decrease in root mean
square error >0.5 mmHg to <1 or 1–2 mmHg, respectively). 96
% of oscillators were underdamped with median damping factor of 0.27 and
frequency of 10.6 Hz. Fractional flow reserve or baseline Pd/Pa
demonstrated no clinically important bias when ignoring oscillations.
However, uncorrected subcycle non-hyperemic pressure ratios (NHPR)
displayed both bias and scatter.   Conclusions: By automatically
accounting for the oscillatory behavior of a fluid-filled catheter system,
phasic matching against a high-fidelity pressure wire can be improved
compared to standard equalization methods. The majority of tracings
contain artifacts, mainly due to underdamped oscillations, and neglecting
them leads to biased estimates of equalization parameters. No clinically
important bias exists for whole-cycle metrics, in contrast to significant
effects on subcycle NHPR.