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Ann Thorac Surg 2002;73:1358
© 2002 The Society of Thoracic Surgeons

Correspondence

Precise quantification of pulsatile flow

Akif Ündar, PhDa,b, Mohammed S. Koudieh, MDa,b, Charles D. Fraser, Jr, MDa,b

a Congenital Heart Surgery Service, Texas Children’s Hospital, 6621 Fannin St, Mail Code: WT 19345-H, Houston, TX 77030-2399 USA
b >Division of Congenital Heart Surgery, Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, TX, USA

e-mail: aundar{at}bcm.tmc.edu

To the Editor

We read with great interest the recent article by Nakano and associates [1]. We congratulate the authors for their meticulous design and promising results. We have a few comments and a suggestion about this important article. In our opinion, complete quantification of pressure-flow waveforms is essential for direct comparison between perfusion modes [2]. Using pulse pressure, pump rate, or the ratio of the femoral artery flow rate to the systemic flow rate separately for quantification is inadequate. The generation of pulsatile flow depends on an energy gradient [3]. Therefore, the quantification in terms of hemodynamic energy is a "must" for direct comparison. We believe that Shepard’s energy equivalent pressure (EEP) formula is the best tool to directly compare different perfusion modes, because it contains both pressure and flow waveforms [4].

Nakano and associates have achieved the pulse pressure of 0 mm Hg during nonpulsatile perfusion. In a clinical scenario, however, pulse pressure is about 15 to 20 mm Hg, or even higher during mechanical circulatory support using a nonpulsatile left ventricular assist device because the natural heart is still beating [5, 6]. Therefore, a precise quantification of pressure-flow waveforms is more critical than ever for direct comparison.

Nakano and associates have stated that a systemic flow rate of lower than 80 ml/kg/min is required to show the benefits of pulsatile perfusion during cardiopulmonary bypass. However, we have shown that pulsatile perfusion with a pump flow rate of 150 ml/kg/min significantly improves cerebral, renal, and myocardial blood flow during and after cardiopulmonary bypass in piglets [7].

We hope that Nakano and associates will consider our suggestion for using the EEP formula for quantification of pulsatile and nonpulsatile pressure-flow waveforms. We believe that this approach may allow them to determine the differences in terms of hemodynamic energy between different perfusion modes, or between different forms of pulsatility.

References

  1. Nakano T., Tominaga R., Morita S., et al. Impact of pulsatile systemic circulation on endothelium-derived nitric oxide release in anesthetized dogs. Ann Thorac Surg 2001;72:156-162.[Abstract/Free Full Text]
  2. Ündar A., Frazier O.H., Fraser C.D., Jr Defining pulsatile perfusion: quantification in terms of energy equivalent pressure. Artif Organs 1999;23:712-716.[Medline]
  3. Shepard R.B., Simpson D.C., Sharp J.F. Energy equivalent pressure. Arch Surg 1966;93:730-740.[Abstract/Free Full Text]
  4. Ündar A., Eichstaedt HC., Masai T., et al. Comparison of six pediatric cardiopulmonary bypass pumps during pulsatile and nonpulsatile perfusion. J Thorac Cardiovasc Surg 2001;122:827-829.[Free Full Text]
  5. Ündar A., Fraser C.D., Jr Physiology of nonpulsatile perfusion: acute versus chronic support [letter]. ASAIO J 2000;46:150.[Medline]
  6. Potapov E.V., Loebe M., Nasseri B.A., et al. Pulsatile flow in patients with a novel nonpulsatile implantable ventricular assist device. Circulation 2001;102(Suppl 3):183.
  7. Ündar A., Masai T., Yang S.Q., Goddard-Finegold J., Frazier O.H., Fraser C.D., Jr Effects of perfusion mode on regional and global organ blood flow in a neonatal piglet model. Ann Thorac Surg 1999;68:1336-1343.[Abstract/Free Full Text]

Related Article

Reply
Toshihide Nakano and Ryuji Tominaga
Ann. Thorac. Surg. 2002 73: 1358-1359. [Extract] [Full Text] [PDF]




This Article
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Mohammed S. Koudieh
Charles D. Fraser, Jr
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