Ann Thorac Surg 1998;66:518
© 1998 The Society of Thoracic Surgeons
Original articles: cardiovascular
Invited commentary
Jeffrey P. Gold, MDa
a Department of Cardiothoracic Surgery, Albert Einstein College of Medicine, Montefiore Medical Center, 3400 Bainbridge Ave, 5th FL, Bronx, NY 10467, USA
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Invited commentary
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Doctor Godart and associates from Guy’s Hospital report their experience with 78 children undergoing Blalock-Taussig shunts. These operations span a 12-year period from 1980 to 1992, with 18 of the patients requiring repeat shunt procedures. The entire group underwent angiography for evaluation of the shunt and pulmonary vascular bed at a mean of 51 months after the initial operation. This is quite long by today’s standards and most likely reflects patients shunted earlier in the series before an era of earlier biventricular and single-ventricle "definitive" repairs. This does, however, provide a window into the natural history of patients undergoing this procedure. There was a mixture of diagnoses favoring tetralogy of Fallot (28%), shunt techniques favoring modified shunts (66%), and sizes favoring 5-mm polytetrafluoroethylene. The follow-up catheterization interval for the classic shunts was more than twice that of the modified. Godart and associates report that classic shunts have been supplanted by modified shunts for technical and safety reasons, which has not been consistently borne out in prior literature. They do not, however, comment on "over-shunting" and clinical congestive heart failure, an issue related to shunt type and size selection [1].
The overall results were good, but did not reach the extremely low mortality rates reported previously [1]. The incidence of pulmonary artery distortion is also somewhat higher than previously reported and is attributed to "tenting" by the shunt. This distortion was a full three times more common in the modified group than in the classic shunt group. Godart and associates do not comment on the percentage of patients requiring plastic procedures on the pulmonary arteries, nor do they describe the subsequent shunt takedown techniques. If tenting of the pulmonary artery causes distortion and flow interruption, than perhaps simple ligation of the shunt may predispose to such problems long after the patient is surgically "cured." Subclavian artery stenosis was reported to occur in 82% of patients, which seems quite high. Other series have not noted this frequency of this long-term problem.
The study underscores the excellent growth of the ipsilateral and contralateral pulmonary arteries, at a rate that was consistent with the child’s age and size. This question of symmetric growth of the branch vessels has prompted much debate about peripheral versus central shunts and a continued trend favoring neonatal full repair. This study is reassuring for most patients requiring Blalock-Taussig shunts. Patients with small pulmonary arteries at the start frequently ended up with small vessels in spite of adequate shunting and follow-up care. This underscores the issue that we really do not fully understand the growth of the pulmonary vascular tree, and that the availability of reasonable blood flow and pressure are only a part of the mix of local and systemic angiogenic factors. A fresh (possibly fetal) look at the vascular biology of the pulmonary bed, with either systemic or local provision of regulating messengers and vascular growth factors, would seem the next logical step. Many groups in the clinical and basic science arenas have begun to seriously focus on these important questions [2–5].
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References
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- Gold J.P., Violaris K.M., Engle M.A., et al. A five year clinical experience with one hundred twelve Blalock-Taussig shunts. J Card Surg 1993;8:9-17.[Medline]
- Bauer E.P., Kuki S., Arras M., Zimmerman R., Schaper W. Increased growth factor transcription after pulmonary artery banding. Eur J Cardiothorac Surg 1997;11:818-823.[Abstract/Free Full Text]
- Dempsey E.C., Badesch D.B., Dobyns E.L., Stenmark K.R. Enhanced growth capacity of neonatal pulmonary artery smooth muscle cells in vitro: dependence on cell size, time from birth, insulin-like growth factor I, and auto-activation of protein kinase C. J Cell Physiol 1994;160:469-481.[Medline]
- Xu Y., Stenmark K.R., Das M., Walchak S.J., Ruff L.J., Dempsey E.C. Pulmonary artery smooth muscle cells from chronically hypoxic neonatal calves retain fetal-like and acquire new growth properties. Am J Physiol 1997;273:L234-L245.
- Mayer J.E., Jr, Shin’oka T., Shum-Tim D. Tissue engineering of cardiovascular structures. Curr Opin Cardiol 1997;12:528-532.[Medline]
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Invited commentary
References