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A Stitch in Time…
EDITORIAL COMMENTARY
A Stitch in Time… James Hammel, MD
Judged against the expectation of a well functioning, permanent, biventricular repair, the surgically modified natural history of tetralogy of Fallot continues to frustrate the pediatric cardiac practitioner. In the article “The mid-term outcomes of bioprosthetic pulmonary valve replacement in children” (this issue), Shinkawa and colleagues report durability data after the implantation of aortic bioprostheses in the pulmonary position, as treatment for the sequelae of pulmonary valve disruption at the initial tetralogy repair. Their findings, that pulmonary valve implantation surgery in children is relatively low-risk, that outcomes at early follow up are generally good, and that by 510 years, valve failures become common, are consistent with earlier reports. Importantly, they report that younger age at implantation is an important predictor of earlier failure, and there is the rub: the surgeon hoping to preserve rather than restore normal right ventricular dimensions and functioning has lacked a reliable bridge from the initial definitive repair to adulthood, when pulmonary annular growth has stopped and freedom from structural valve deterioration is longer (Fig). Beyond these important findings, it becomes harder to draw useful generalizations. Prosthesis-to-patient size ratio, valve make and model, and implantation position and technique interrelate in complex ways with the variables of treatment era, age, and diagnosis. Given the heterogeneity and relative scarcity of subjects for study, the ideal prosthesis type, size, and implant style are unlikely to declare themselves. None of the available bioprostheses were designed for pulmonary implantation, and the range of sizes available was not established with the needs of children in mind. Given that probably only 2000 patients are born with tetralogy of Fallot annually1,2 compared to more than 67,000 older adults undergoing aortic valve replacement per year,3 an ideal pediatric pulmonary valve prosthesis is unlikely ever to be commercialized. Previous reports on the outcomes of pulmonary valve implantation after tetralogy have focused on the likelihood of restoration of the dilated, dysfunctional ventricle to a more normal dimension and contractile ability, and the prevention of sudden death which presumably relates to histopathological damage in the right ventricular myocardium.4 Consensus recommendations are lowering the threshold for the severity of ventricular damage due to pulmonary insufficiency that indicates valve implantation, into the younger and
smaller patient.5 These complications represent the “nine stitches” which might be saved. It is likely, although as yet unproven, that definitive repair James Hammel, MD which preserves native pulmonary See related article on pages 310–318. valve function will obviate late right ventricular degradation partially or completely. A strategy of initial palliation, although currently “unfashionable,” if selectively applied might reduce the need for disruption of the pulmonary valve at definitive surgery.6 Tedious but potentially effective techniques are being developed for the preservation and reconstruction of a competent native pulmonary valve.7 Even the implantation of a monocusp valve flap in certain cases may, with improved materials, provide a prolonged period of protection from the effects of pulmonary regurgitation.8 These techniques represent the “stitch in time,” the extra effort expended at the initial definitive repair, which may put off the necessity of pulmonary valve implantation into adulthood or indefinitely. The present work demonstrates that “adult-style” management of pulmonary valve insufficiency is applicable only so far back into childhood. Until the generation of children growing up after pulmonary valve-disrupting operations has graduated to the adult clinic, important questions remain. For optimum health of the right ventricle, will any threshold end diastolic volume index be shown to be unnecessarily low, or will progressive dilation beyond the normal range become the volume criterion? Does long-lasting damage follow a period of marked right ventricular dilation during childhood if valve implantation is deferred until adult size is reached? And at the end, will techniques which preserve some potential of pulmonary valve function and growth really result in long-term freedom from right ventricular disease? Dr Shinkawa and colleagues are to be congratulated for their important contribution to the care of children with this common, complex defect.
Children's Hospital & Medical Center, Omaha, NE
1043-0679/$-see front matter ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1053/j.semtcvs.2015.08.012
319
PULMONARY VALVE REPLACEMENT AFTER TETRALOGY REPAIR
Figure. Missed opportunity: the downstream pathology of pulmonary valve-disrupting operations for tetralogy. 1. Department of Health and Human Services. adults after tetralogy of Fallot repair. Am J 7. Vida VL, Guariento A, Castaldi B, et al: Evolving National Center for Health Statistics. www. Cardiol 95(6):779-782, 2005 strategies for preserving the pulmonary valve 5. Geva T: Indications and timing of pulmonary dhhs.gov. Accessed 15 August, 2015. during early repair of tetralogy of Fallot: Mid2. Hoffman JI, Kaplan. S: The incidence of convalve replacement after tetralogy of Fallot repair. term results. Thorac Cardiovasc Surg 147(2): genital heart disease. J Am Coll Cardiol 39: Semin Thorac Cardiovasc Surg Pediatr Card Surg 687-694, 2014 Annu :11-22, 2006 1890-1900, 2002 8. Sasson L, Houri S, Raucher Sternfeld A, et al: 3. Iung B, Vahanian A: Epidemiology of valvular heart 6. Ross ET, Costello JM, Backer CL, et al: Right Right ventricular outflow tract strategies for ventricular outflow tract growth in infants with disease in the adult. Nat Rev Cardiol 8:162-172, 2011 repair of tetralogy of Fallot: Effect of monocusp 4. Therrien J, Provost Y, Merchant N, et al: Optimal palliated tetralogy of Fallot. Ann Thorac Surg 99 valve reconstruction. Eur J Cardiothorac Surg 43 timing for pulmonary valve replacement in (4):1367-1372, 2015 (4):743-751, 2013
320
Seminars in Thoracic and Cardiovascular Surgery Volume 27, Number 3
A Stitch in Time… James Hammel, MD
Judged against the expectation of a well functioning, permanent, biventricular repair, the surgically modified natural history of tetralogy of Fallot continues to frustrate the pediatric cardiac practitioner. In the article “The mid-term outcomes of bioprosthetic pulmonary valve replacement in children” (this issue), Shinkawa and colleagues report durability data after the implantation of aortic bioprostheses in the pulmonary position, as treatment for the sequelae of pulmonary valve disruption at the initial tetralogy repair. Their findings, that pulmonary valve implantation surgery in children is relatively low-risk, that outcomes at early follow up are generally good, and that by 510 years, valve failures become common, are consistent with earlier reports. Importantly, they report that younger age at implantation is an important predictor of earlier failure, and there is the rub: the surgeon hoping to preserve rather than restore normal right ventricular dimensions and functioning has lacked a reliable bridge from the initial definitive repair to adulthood, when pulmonary annular growth has stopped and freedom from structural valve deterioration is longer (Fig). Beyond these important findings, it becomes harder to draw useful generalizations. Prosthesis-to-patient size ratio, valve make and model, and implantation position and technique interrelate in complex ways with the variables of treatment era, age, and diagnosis. Given the heterogeneity and relative scarcity of subjects for study, the ideal prosthesis type, size, and implant style are unlikely to declare themselves. None of the available bioprostheses were designed for pulmonary implantation, and the range of sizes available was not established with the needs of children in mind. Given that probably only 2000 patients are born with tetralogy of Fallot annually1,2 compared to more than 67,000 older adults undergoing aortic valve replacement per year,3 an ideal pediatric pulmonary valve prosthesis is unlikely ever to be commercialized. Previous reports on the outcomes of pulmonary valve implantation after tetralogy have focused on the likelihood of restoration of the dilated, dysfunctional ventricle to a more normal dimension and contractile ability, and the prevention of sudden death which presumably relates to histopathological damage in the right ventricular myocardium.4 Consensus recommendations are lowering the threshold for the severity of ventricular damage due to pulmonary insufficiency that indicates valve implantation, into the younger and
smaller patient.5 These complications represent the “nine stitches” which might be saved. It is likely, although as yet unproven, that definitive repair James Hammel, MD which preserves native pulmonary See related article on pages 310–318. valve function will obviate late right ventricular degradation partially or completely. A strategy of initial palliation, although currently “unfashionable,” if selectively applied might reduce the need for disruption of the pulmonary valve at definitive surgery.6 Tedious but potentially effective techniques are being developed for the preservation and reconstruction of a competent native pulmonary valve.7 Even the implantation of a monocusp valve flap in certain cases may, with improved materials, provide a prolonged period of protection from the effects of pulmonary regurgitation.8 These techniques represent the “stitch in time,” the extra effort expended at the initial definitive repair, which may put off the necessity of pulmonary valve implantation into adulthood or indefinitely. The present work demonstrates that “adult-style” management of pulmonary valve insufficiency is applicable only so far back into childhood. Until the generation of children growing up after pulmonary valve-disrupting operations has graduated to the adult clinic, important questions remain. For optimum health of the right ventricle, will any threshold end diastolic volume index be shown to be unnecessarily low, or will progressive dilation beyond the normal range become the volume criterion? Does long-lasting damage follow a period of marked right ventricular dilation during childhood if valve implantation is deferred until adult size is reached? And at the end, will techniques which preserve some potential of pulmonary valve function and growth really result in long-term freedom from right ventricular disease? Dr Shinkawa and colleagues are to be congratulated for their important contribution to the care of children with this common, complex defect.
Children's Hospital & Medical Center, Omaha, NE
1043-0679/$-see front matter ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1053/j.semtcvs.2015.08.012
319
PULMONARY VALVE REPLACEMENT AFTER TETRALOGY REPAIR
Figure. Missed opportunity: the downstream pathology of pulmonary valve-disrupting operations for tetralogy. 1. Department of Health and Human Services. adults after tetralogy of Fallot repair. Am J 7. Vida VL, Guariento A, Castaldi B, et al: Evolving National Center for Health Statistics. www. Cardiol 95(6):779-782, 2005 strategies for preserving the pulmonary valve 5. Geva T: Indications and timing of pulmonary dhhs.gov. Accessed 15 August, 2015. during early repair of tetralogy of Fallot: Mid2. Hoffman JI, Kaplan. S: The incidence of convalve replacement after tetralogy of Fallot repair. term results. Thorac Cardiovasc Surg 147(2): genital heart disease. J Am Coll Cardiol 39: Semin Thorac Cardiovasc Surg Pediatr Card Surg 687-694, 2014 Annu :11-22, 2006 1890-1900, 2002 8. Sasson L, Houri S, Raucher Sternfeld A, et al: 3. Iung B, Vahanian A: Epidemiology of valvular heart 6. Ross ET, Costello JM, Backer CL, et al: Right Right ventricular outflow tract strategies for ventricular outflow tract growth in infants with disease in the adult. Nat Rev Cardiol 8:162-172, 2011 repair of tetralogy of Fallot: Effect of monocusp 4. Therrien J, Provost Y, Merchant N, et al: Optimal palliated tetralogy of Fallot. Ann Thorac Surg 99 valve reconstruction. Eur J Cardiothorac Surg 43 timing for pulmonary valve replacement in (4):1367-1372, 2015 (4):743-751, 2013
320
Seminars in Thoracic and Cardiovascular Surgery Volume 27, Number 3