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J Thorac Cardiovasc Surg 1998;116:182-183
© 1998 Mosby, Inc.

Letters To The Editor

Evaluation of resting coronary blood flow and coronary flow reserve in infants after cardiac operations

To the Editor:

In a recent issue of the Journal, Donnelly and coauthors presented an elegant clinical study on the evaluation of resting coronary blood flow and coronary flow reserve in infants after cardiac surgery by means of positron emission tomography with nitrogen 13–labeled ammonia. ¹ The information provided by this work is a significant technical achievement, particularly in a field, neonatal cardiac surgery, in which meaningful methods for measuring myocardial function are not yet available.

Donnelly and coauthors underlined the limited information available on "myocardial perfusion in the infant heart," and they pointed out that the "degree to which neonates can increase myocardial blood flow with maximal coronary dilatation is unknown." ¹ They state: "there are no published reports quantifying coronary flow or coronary flow reserve in human infants." ¹ If that statement is accepted as valid, their study will be a reference for any other clinical investigation in this field.

Observations recorded on the isolated blood-perfused neonatal piglet heart can be interesting. ² Baseline coronary blood flow is 91.9 ± 15.8 ml/m/100 gm as demonstrated by direct measurement in an isolated blood-perfused model of the neonatal (1- to 5-day-old) piglet heart. So that the reserve of neonatal myocardial perfusion could be evaluated, 1 hour of hypoxia has been applied at three different degrees: mild (oxygen tension 42 mm Hg, oxygen saturation 82%), moderate (oxygen tension 27 mm Hg, oxygen saturation 59%), and severe (oxygen tension 20 mm Hg, oxygen saturation 36%). The following variations from baseline value have been recorded after 1 hour of hypoxia: 231% ± 66% after mild hypoxia, 334% ± 40% after moderate hypoxia, and 560% ± 96% after severe hypoxia. These data showed a substantial increase in the coronary blood flow after 1 hour of hypoxia, with a significant (p < 0.05) difference from the baseline value in the group with severe hypoxia. Therefore the coronary flow reserve should be considered as a potential entity, at least in this model of the isolated blood-perfused neonatal piglet heart.

Interestingly, in the same experimental study, after 1 hour of reoxygenation (oxygen tension 400 mm Hg, oxygen saturation 100%), all values of coronary blood flow returned to the baseline, except in the group with severe hypoxia, in which the coronary blood flow remained 224% ± 42% of the baseline after 1 hour of full reoxygenation.

These observations prompted my colleagues and me to further investigate the problem of reoxygenation. ^3,4 On the basis of these experimental observations, it would be interesting to use the clinical model of Donnelly and coauthors to study the resting coronary blood flow and coronary flow reserve in infants, bearing in mind (1) the potential differences between acyanotic and cyanotic infants, in particular with regard to the coronary reserve, and (2) the potential differences between the two groups, in particular with regard to the variations between preoperative and postoperative parameters (with or without reoxygenation).

Médecin AssociéCentre Hospitalier Universitaire VaudoisClinique de GenolierGenolier CH-1272, Switzerland12/8/90664

References

1. Donnelly JP, Raffel CM, Shulkin BL, Corbett JR, Bove EL, Mosca RS, et al. Resting coronary flow and coronary flow reserve in human infants after repair or palliation of congenital heart defects as measured by positron emission tomography. J Thorac Cardiovasc Surg 1998;115:103-10. [Abstract/Free Full Text]
   
2. Corno AF, Laks H, Davtyan H, Flynn W, Drinkwater DC, Chang P. The effects of the acute hypoxia and reoxygenation on function and metabolism of the isolated neonatal heart. J Am Coll Cardiol 1987;9:35A.
   
3. Corno AF, Samaja M. The reoxygenation phenomenon. J Thorac Cardiovasc Surg 1993;105:373.[Medline]
   
4. Corno AF, Samaja M, Casalini S, Allibardi S. The effects of the rate of reoxygenation on the recovery of hypoxemic hearts. J Thorac Cardiovasc Surg 1995;109-1250.
   

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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 Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Antonio Corno Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Corno, A. Search for Related Content PubMed PubMed Citation Articles by Corno, A.