Background: Pulse wave analysis using the SphygmoCor system allows the estimation of central blood pressures (BP). However, there is controversy over its accuracy for clinical use.
Methods: In 45 patients undergoing coronary angiography, we compared the ascending aorta BPs measured by the invasive catheter with the estimations by the SphygmoCor system, using paired t-tests, simple correlation analysis, and Bland-Altman plots.
Results: The estimation of central systolic BP by SphygmoCor was lower, although statistically insignificant, than that measured by the catheter (144±29 vs. 148±30 mmHg; P=0.98). The standard deviation of the difference amounted to 17 mmHg. Both the measured and estimated central systolic BPs were significantly (P<0.001) lower than the brachial systolic BP (156±30 mmHg). The diastolic BP measured at the brachial artery (87±15 mmHg) and provided by SphygmoCor (90±15 mmHg) were systematically higher (P<0.001) than that measured by the catheter (74±13 mmHg). The SphygmoCor system underestimated the central pulse pressure by -20±14 mmHg compared with the catheter method. The correlation coefficients for systolic BP, diastolic BP, and pulse pressure between catheter measurements and the SphygmoCor estimations were 0.84, 0.60, and 0.82 (P<0.001), respectively.
Conclusion: When the radial waveform was calibrated with the oscillometric brachial pressures, the SphygmoCor system could not provide accurate estimation of central BPs. The inaccurate measurement of cuff pressure was the major limiting factor for the use of the transfer function in the clinical settings.