Comparison of optical measurements of critical closing pressure acquired before and during induced ventricular arrhythmia in adults.

The critical closing pressure (CrCP) of cerebral circulation, as measured by diffuse correlation spectroscopy (DCS), is a promising biomarker of intracranial hypertension. However, CrCP techniques using DCS have not been assessed in gold standard experiments. CrCP is typically calculated by examining the variation of cerebral blood flow (CBF) during the cardiac cycle (with normal sinus rhythm). We compare this typical CrCP measurement with a gold standard obtained during the drops in arterial blood pressure (ABP) caused by rapid ventricular pacing (RVP) in patients undergoing invasive electrophysiologic procedures. Adults receiving electrophysiology procedures with planned ablation were enrolled for DCS CBF monitoring. CrCP was calculated from CBF and ABP data by three methods: (1) linear extrapolation of data during RVP ( ; the gold standard); (2) linear extrapolation of data during regular heartbeats ( ); and (3) fundamental harmonic Fourier filtering of data during regular heartbeats ( ). CBF monitoring was performed prior to and during 55 episodes of RVP in five adults. and demonstrated agreement ( , (95%CI, 0.72 to 1.38). Agreement between and was worse; was higher than (mean ± SD; ). Our results suggest that DCS-measured CrCP can be accurately acquired during normal sinus rhythm.