Validation Study to Determine the Accuracy of Central Blood Pressure Measurement Using the Sphygmocor Xcel Cuff Device

Abstract

Numerous devices purport to measure central (aortic) blood pressure (BP) as distinct from conventional brachial BP. This validation study aimed to determine the accuracy of the Sphygmocor Xcel cuff device (AtCor Medical, CardieX, Sydney, Australia) for measuring central BP. 296 patients (mean age 61±12 years) undergoing coronary angiography had simultaneous measurement of invasive central BP and noninvasive cuff-derived central BP using the Xcel cuff device (total n=558 individual comparisons). A subsample (n=151) also had invasive brachial BP measured. Methods were undertaken according to the Artery Society recommendations, and several calibration techniques to derive central systolic BP (SBP) were examined. Minimum acceptable error was ≤5±≤8 mm Hg. Central SBP was significantly underestimated, and with wide variability, when using the default calibration of brachial-cuff SBP and diastolic BP (DBP; mean difference±SD, −7.7±11.0 mm Hg). Similar variability was observed using other calibration methods (cuff 33% form-factor mean arterial pressure and DBP, −4.4±11.5 mm Hg; cuff 40% form-factor mean arterial pressure and DBP, 4.7±11.9 mm Hg; cuff oscillometric mean arterial pressure and DBP, −18.2±12.1 mm Hg). Only calibration with invasive central integrated mean arterial pressure and DBP was within minimal acceptable error (3.3±7.5 mm Hg). The difference between brachial-cuff SBP and invasive central SBP was 3.3±10.7 mm Hg. A subsample analysis to determine the accuracy of central-to-brachial SBP amplification showed this to be overestimated by the Xcel cuff device (mean difference 4.3±9.1 mm Hg, P =0.02). Irrespective of cuff calibration technique, the Sphygmocor Xcel cuff device does not meet the Artery Society accuracy criteria for noninvasive measurement of central BP.

Validation study to determine the accuracy of central blood pressure measurement using the SphygmoCor XCEL cuff device in patients with severe aortic stenosis undergoing transcatheter aortic valve replacement

“… 10 The most recent validation study was aimed to determine the accuracy of the SphygmoCor XCEL cuff device for measuring central blood pressure in 296 patients undergoing coronary angiography. 11 Central SBP was underestimated and with wide variability (−7.7 ± 11.0 mm Hg). In contrast to the previous study, the SphygmoCor XCEL cuff device was found not to meet the accuracy criteria for non-invasive measurement of central SBP of 5 ± 8 mm Hg.…”

“…The only appropriately powered and conducted validation studies for the XCEL device are Gotzmann et al 10 . and Schultz et al 11 . In the first study, including 502 patients, non‐invasive assessment of aortic SBP was performed by both the SphygmoCor XCEL device and the Mobil‐O‐Graph NG device and was compared with simultaneous invasive pressure measurement (through fluid‐filled catheters).…”

“…8 (2) Bland-Altman analysis shows lower bias before and a larger bias after TAVR due to a more in- Nonetheless, this study did not fulfill the requirements of a validation study according to ARTERY Society protocols and in any case, the differences were outside the pass criteria. 8 The only appropriately powered and conducted validation studies for the XCEL device are Gotzmann et al 10 and Schultz et al 11 In the first study, including 502 patients, non-invasive assessment of aortic SBP was performed by both the SphygmoCor XCEL device and the Mobil-O-Graph NG device and was compared with simultaneous invasive pressure measurement (through fluid-filled catheters). The mean systolic bias of SphygmoCor XCEL device to invasively assessed aortic SBP was −5.0 ± 7.7 mm Hg and with Mobil-O-Graph NG device was slightly but significantly larger (−6.0 ± 10.4 mm Hg, p =.011).…”

“…The mean difference was lower (−3 mm Hg) but dispersion was somehow larger than in general population. 10,11 The non-invasive metrics correlated well with the invasive ones, but correlation is not the intended statistic to consider when aiming a validation study. Having said this, the superior correlation with the central invasive pressure shown for the XCEL estimated central pressure with respect to the cuff-brachial SBP before TAVR would make it the first best candidate to be used in the calculation of non-invasive metrics related to the valvulo-arterial load in patients with AS.…”

Accurate Measurement of Blood Pressure

“…As alluded to earlier, there is a strong physiological rationale that central aortic BP may be a better predictor of cardiovascular risk than peripheral BP. However, there are myriad issues which plague the accuracy of devices that estimate central BP [31], including: (1) uncertainty on the best waveform calibration method [32]; (2) reliance on cuff BP for calibration of waveforms [33]; (3) failing to account for brachial-radial BP amplification (only applicable to radial tonometry methods) [34][35][36][37]; and (4) device-specific results due to different algorithms for the estimation of BP [31,32,38]. This final point has led to devices that estimate central BP being described as either 'type I' or 'type II' [31].…”