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Ann Thorac Surg 2002;73:1358-1359
© 2002 The Society of Thoracic Surgeons

Correspondence

Reply

Toshihide Nakano, MDa, Ryuji Tominaga, MDa

a Division of Cardiovascular Surgery, Faculty of Medicine, Kyushu University 3-1-1, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan

e-mail: toshihide.nakano{at}mb8.seikyou.ne.jp

To the Editor

I thank Dr Ündar and his associates for their comments and suggestions regarding our work [1]. We agree completely that quantification of pulse waveforms is essential in order to describe pulsatile flow, especially for comparison with other pulsatile perfusion models. In that sense, Shepard and colleagues’ energy equivalent pressure formula [2] is a frequently useful and important method of characterizing pulsatile flow. This formula properly represents pulse waveforms from the perspective of hemodynamic energy; however, we believe that other factors that we measured in our experiment, such as changes in pressure velocity and flow velocity, are also necessary for precise quantification of pulsatile waveforms.

In our left heart bypass model, a cannula was inserted into both the left atrium and left ventricle to buffer pulsatile preload to a centrifugal pump. In addition, we adjusted the circulatory blood volume to avoid blood output through the aortic valve and to maintain constant systemic blood flow in both the pulsatile and nonpulsatile systemic circulation. These methods enabled us to obtain nonpulsatile systemic flow with a pulse pressure of less than 10 mm Hg, despite contraction of the left ventricle.

Dr Ündar showed improved organ blood flow in pulsatile perfusion with a pump rate of 150 ml/kg/min in a neonate piglet [3]. In the present study, we used adult dogs, and, in our previous report, we used a conscious calf to demonstrate that there was no difference in oxidative metabolism between pulsatile and nonpulsatile systemic perfusion at a pump flow rate of over 90 ml/kg/min [4]. Thus, we believe it is unreasonable to do a simple comparison beyond age and species solely from the perspective of effective pulsatile flow rate.

The main focus of our present and previous studies [1, 5] was to reveal the physiological effects of pulsatile perfusion on endothelial cell function via shear stress. We are convinced that it would be very useful if we could establish a correlation between Shepard and colleagues’ energy equivalent pressure formula and the degree of shear stress on the arterial endothelial cells in various perfusion modes. Therefore, we will certainly utilize this formula in describing pulse waveforms in our next study.

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. Shepard R.B., Simpson D.C., Sharp J.F. Energy equivalent pressure. Arch Surg 1966;93:730-740.[Abstract/Free Full Text]
  3. 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]
  4. Tominaga R., Smith W.A., Massiello A., Harasaki H., Golding L.A. Chronic nonpulsatile blood flow. III. Effects of pump flow rate on oxygen transport and utilization in chronic nonpulsatile biventricular bypass. J Thorac Cardiovasc Surg 1996;111:863-872.[Abstract/Free Full Text]
  5. Nakano T., Tominaga R., Nagano I., Okabe H., Yasui H. Pulsatile flow enhances endothelium-derived nitric oxide release in the peripheral vasculature. Heart Circ Physiol 2000;278:H1098-H1104.

Related Article

Precise quantification of pulsatile flow
Akif Ündar, Mohammed S. Koudieh, and Charles D. Fraser, Jr
Ann. Thorac. Surg. 2002 73: 1358. [Extract] [Full Text] [PDF]




This Article
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Ryuji Tominaga
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