Shortened Head-Up Tilting Test Guided by Systolic Pressure Reductions in Neurocardiogenic Syncope

To the Editor:We read with interest and appreciated the article by Pitzalis et al. 1 However, an important methodological issue requires further clarification with regard to the Finapres method.Specifically, the authors do not mention whether and how corrections were made to avoid the artifacts in pressure measurements caused by changes in body position during the test.The traces shown in the Figure suggest that the pressure measurements are influenced, during the tilting-up phase, by the change in hydrostatic pressure at the finger-cuff.This is reflected by the presumably fictitious step increase in both diastolic and systolic pressures of about 20 mm Hg in the tracings corresponding in time with the uptilting.Indeed, the reliability of Finapres is not perfectly linear, and may over-or underestimate pressure values at the 2 extremes of the measurement range. 2 Imprecision is usually avoided by self-calibration of the instrument every 60 seconds; 3 however, if the reference pressure value is not simultaneously verified by other means (eg, a simple sphygmomanometer), the measurement recorded by the instrument may be unreliable, particularly after substantial variations of pressure, and may lead to a substantial number of false-positives.The step increase in pressure shown in the Figure , however, would suggest that pressure values were not checked during changes of position.This is an important issue, as the clinical accuracy per se of Finapres is suboptimal 3 and requires scrupulous observance of every possible adjustment.At our institution, baseline simultaneous measurements of the arterial blood pressure are routinely obtained at the radial artery by Dinamap (Critikon, Tampa, Calif) and traditional (Riva-Rocci, Erka, Germany) mercury brachial cuff in order to assess the agreement between the 2 methods.4 Throughout the whole test (baseline, tilting, and recovery), the beat by beat pressure measurements obtained by the Finapres are compared with the Dinamap measurements every 3 minutes to correct, as needed, the Finapres pressure values either by adjustment of the finger position exactly at the sternal angle to correct differences of hydrostatic pressure, 3 or by turning on the automatic servo self adjustment of the Finapres to correct the instrument shift.