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J Thorac Cardiovasc Surg 1999;117:1233
© 1999 Mosby, Inc.

LETTERS TO THE EDITOR

Reply to the Editor:

Department of Cardiology
Hippokration Hospital
9 TepeleniouStr
Paleo Psychico
Athens 15452, Greece

Regarding the letter to the Editor referring to our article, "AorticFunction in Patients During Intra-aortic Balloon Pumping Determined by thePressure-Diameter Relation," we would like to state the following.

First, wave reflections are evaluated by measuring augmentation index,defined as the ratio: (pressure from inflection point to late systolic peak)/(pulsepressure). ¹ Beginning ofpressure wave upstroke, inflection point, and late systolic peak are definedby using the fourth derivative of pressure. When plotted against derivative,the timing of inflection point is indicated by a local minimum in the firstderivative. To simplify the detection of this point, higher order derivativesare used to identify the zero-crossing point equivalent to the local minimumof the first derivative. The first zero crossing of the fourth derivative(in a direction from above to below the zero line) corresponded to the beginningof the pressure wave upstroke. The second zero crossing in the same directioncorresponded to the inflection point. ¹ Scatter in each primary pressure derivative is smoothed by applyingmoving average curve (Microsoft Excel 97 for Windows; Microsoft Corporation,Redmond, Wash). This resulted in phase shifts, which depend on the intervalof the moving average. Phase shifts of all derivatives are adjusted accordingly.

Second, pressure augmentation index measured on the heart ejection partof the blood pressure tracing is the only way to appreciate, in a comparativemanner, the changes of the reflected waves both at baseline and during intra-aorticballoon pumping. ²

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References

1. Stefanadis C, Dernellis J, VavuranakisM, Tsiamis E, Vlachopoulos C, Toutouzas K, et al. Effect of ventricular pacing–inducedtachycardia on aortic mechanics in man. Cardiovasc Res 1998;39:506-14.
   
2. Stefanadis C, Dernellis J, Tsiamis E, StratosC, Kallikazaros I, Toutouzas P. Aortic function in patients during intra-aorticballoon pumping determined by the pressure-diameter relation. J Thorac CardiovascSurg 1998;116:1052-9.
   

This Article Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Stefanadis, C. Search for Related Content PubMed Articles by Stefanadis, C.