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Ann Thorac Surg 2003;76:977-978
© 2003 The Society of Thoracic Surgeons

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Correspondence

Reply

^a Division of Cardiac Surgery, Aichi Medical University, Nagakute-cho, Aichi 480-1195, Japan

e-mail: kawaguch{at}aichi-med-u.ac.jp

To the Editor:

I am pleased to respond to Drs Misawa and Fuse regarding our recent study [1]. As my colleagues and I [2] reported in 1992, when assist cup compression is applied synchronously with the heart beat, the heart can generate more cardiac work in terms of pressure–volume area and external work without an increase in myocardial oxygen consumption for fixed end-diastolic and stroke volumes. The increased portion of cardiac work must come from compression by the assist cup. If the end-diastolic volume becomes smaller with compression, the cardiac work generated by the native heart also becomes smaller, although total cardiac work is unchanged. Because of work by the assist cup, myocardial oxygen consumption should be smaller. Therefore, when the end-diastolic volume becomes smaller as observed in in vivo hearts assisted by dynamic cardiomyoplasty, a reduction in oxygen consumption can be explained by the same mechanism.

Although we can assume myocardial wall stress is smaller with compression, it is not necessary to invoke Laplace’s law because wall thickness is unchanged when the assist device compresses the heart. We simply recognize that total cardiac work generated is a summation of work done by the heart itself and work transferred to the heart by compression in synchrony with the heart beat. However, if the effect of wall thickness is as Drs Misawa and Fuse surmise, an oxygen-saving effect could be observed even with adynamic cardiomyoplasty. This effect may be an additional benefit of dynamic and adynamic cardiomyoplasty.

References

1. Kawaguchi O., Huang Y.F., Yuasa T., Shirota K., Carrington R.A.J., Hunyor S.N. Cardiomyoplasty reduces myocardial oxygen consumption: implications for direct mechanical compression. Ann Thorac Surg 2002;74:1092-1097.[Abstract/Free Full Text]
2. Kawaguchi O., Goto Y., Futaki S., Ohgoshi Y., Yaku H., Suga H. Mechanical enhancement and myocardial oxygen saving by synchronized dynamic left ventricular compression. J Thorac Cardiovasc Surg 1992;103:573-581.[Abstract]

This Article Full Text (PDF) 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 Kawaguchi, O. Search for Related Content PubMed Articles by Kawaguchi, O. Related Collections Mechanical Circulatory Assistance