Ann Thorac Surg 2005;79:36-37
© 2005 The Society of Thoracic Surgeons
INVITED COMMENTARY
Roberto M. Di Donato, MD
Department of Pediatric Cardiac Surgery, Ospedale Bambino Gesù, Piazza S. Onofrio 4, 00165Rome, Italy
Berdat and coworkers have supplied one of the most suggestive contributions to the thesis that additional pulmonary blood flow, while providing higher oxygen saturation, has no adverse effect on clinical and functional outcome after cavopulmonary anastomosis. For the sake of discussion, however, I should raise some observations. First, this is not a prospective randomized study, and the three groups of patients considered are not totally comparable, particularly in terms of age at surgery. Second, some of the findings are contradictory or unexpected. For example, although it was claimed to be beneficial, retrograde additional pulmonary blood flow through a Blalock-Taussig shunt was identified as a risk factor for early death by logistic regression. Furthermore, superior vena cava syndrome was higher in the group with lower pressure antegrade pulmonary blood flow compared with the Blalock-Taussig shunt group. Finally, the overall failure rate of bidirectional cavopulmonary anastomosis suggests that borderline indications were often used, which may further confound the interpretation of the results.
To further mitigate the enthusiasm for additional pulmonary blood flow, I should emphasize that even an isolated bidirectional cavopulmonary anastomosis is, per se, a condition of "some" ventricular volume overload. In fact, although the superior vena cava is in series with the pulmonary circulation, the upper and lower systemic hemi-circuits are instead arranged in parallel, with the arterial output for the upper body facing systemic and pulmonary levels of resistance. The systemic flow to the lower body therefore confronts only one level of resistance and is faster, particularly during physical exertion, which ultimately implies a condition of at least moderate volume overload. The addition of an alternative source of pulmonary blood flow necessarily imposes a greater volume load, largely unpredictable, that potentially neutralizes the process of ventricular remodeling sought by staging the Fontan operation.
I believe that some questions are still unanswered:
- 1 What are the criteria for the calibration of additional pulmonary blood flow?
- 2 What degree of superior vena caval "reflux" should one accept?
- 3 Should additional pulmonary blood flow, as some suggested, be used only in very young and very old patients?
- 4 What is the timing for a Fontan operation in the presence of an additional pulmonary blood flow?
In summary, although the authors should be commended for their elegant study, they provide no clear-cut evidence for the routine application of additional pulmonary blood flow. Hence, the staged approach to Fontan operation should be individualized.
Related Article
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Additional Pulmonary Blood Flow Has No Adverse Effect on Outcome After Bidirectional Cavopulmonary Anastomosis
- Pascal A. Berdat, Emré Belli, François Lacour-Gayet, Claude Planché, and Alain Serraf
Ann. Thorac. Surg. 2005 79: 29-36.
[Abstract]
[Full Text]
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