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Treatment algorithm for Pulmonary Atresia with Intact Ventricular Septum
Progress in Pediatric Cardiology 29 (2010) 61–63
Contents lists available at ScienceDirect
Progress in Pediatric Cardiology j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / p p e d c a r d
Treatment algorithm for Pulmonary Atresia with Intact Ventricular Septum John E. Foker a,⁎, James M. Berry b, Lee A. Pyles b a b
Division of Cardiothoracic Surgery, University of Minnesota, Minneapolis, MN, USA Division of Cardiothoracic Pediatric Cardiology, University of Minnesota, Minneapolis, MN, USA
a r t i c l e
i n f o
Available online 27 March 2010 Keywords: Pulmonary atresia with intact ventricular septum Hypoplasia SVR 2VR
a b s t r a c t The articles in this issue reveal the complexity of the PAIVS spectrum and the methods of treatment that are currently being used. Despite the complexity, the articles provide greater understanding of the developmental events leading to these lesions and the methods that could be used to reverse them. Taken together, the evidence certainly favors embarking on a 2VR track whenever possible. The number of completed biventricular repairs will be increased and also the adverse later consequences of a hypertensive RV and persisting significant RV to coronary artery connections will be eliminated when they are not. The algorithm, therefore, is heavily weighted to 2VRs. © 2010 Elsevier Ireland Ltd. All rights reserved.
Progress in the treatment of PAIVS patients is the goal of this special issue. The articles have provided important information which suggests that the patients should be placed on a 2VR track initially and, even if they eventually fall short, the situation will also be improved for those who end up with a SVR. A reasonable expectation is that a substantial increase in 2VRs should result and produce a similar improvement in long-term outcomes for the group. As opposed to beginning with the goal of a 2VR, a number of centers have attempted to improve the results by deciding at the initial evaluation whether a SVR or a 2VR track would be most appropriate. Usually, the degree of right heart hypoplasia is the deciding factor in choosing the treatment track. By sharpening the criteria for this stratification, some centers have achieved a reduction in overall mortality although not in SVR rates. The initial assignment into a SVR track, moreover, disregards the considerable growth potential and essentially eliminates the likelihood of having two functioning ventricles. The algorithm presented here, in contrast, begins with the assumption that a 2VR or something close to it is possible in these infants. The enlistment of the growth potential, wherever possible, should provide the best physiological solution with the greatest longterm benefit. Futhermore, leaving a hypertensive RV and persisting RVCACs predictably have adverse consequences into adulthood, as presented in this issue by Tanoue et al and Ekman-Joelsson et al. Consequently, even if a 2VR is not completely realized, eliminating these lesions will still improve the long-term outlook. The algorithm portrays, in bolder type, the evaluations needed and the basic components required to achieve a 2VR outcome (Fig. 1). The algorithm also includes, in lighter type, the other procedures that may be needed to correct residual lesions, when present, to improve the 2VR ⁎ Corresponding author. University of Minnesota, 420 Delaware St. SE MMC 495, Minneapolis, MN 55455, United States. Tel.: + 1 612 625 0910; fax: + 1 612 625 4106. E-mail address: [email protected] (J.E. Foker). 1058-9813/$ – see front matter © 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ppedcard.2010.02.005
result. Because of the spectrum of the lesions and the difficulties in achieving complete repair initially, some patients may require additional procedures for optimum catch-up growth and function. For those patients who are only suitable for a palliative repair, the various possibilities of shunts, transplantation, and a Fontan procedure (SVR) are indicated with dashed lines. Diagnosis often begins by fetal echo and someday, fetal treatment may also be commonplace. For now, however, in utero valvotomies are done only at a small handful of centers. More time and experience will be required to accurately list the indications, procedures and likely results. Certainly, providing forward flow will encourage RV and TV growth and should limit the degree of hypoplasia although additional procedures to relieve residual RV outflow track obstruction will be needed. Nevertheless, when applicable, a satisfactory 2VR should be the outcome and in utero treatment will likely be used more in the future. The initial newborn evaluation will usually establish the details of PAIVS. Among these, the presence or absence of significant RV-CACs and associated coronary artery lesions, as well as the size and quality of the tricuspid valve are important issues. If there are significant RV-CACs, the evaluation should attempt to confirm that the coronary arteries are connected to the aorta. This is an important developmental event that rarely does not take place. Even a brief antegrade signal in diastole establishes continuity through to the aorta. If no continuity between aorta and coronary arteries exists transplantation seems to be the best option. The evaluation should then proceed to determine the location of the connections and identify, with the aid of angiography, significant stenoses resulting from the associated arteritis. From these studies, a plan for the treatment of the RV-CACs should emerge. The size of the TV is important and, in addition, about 25% of the valves have some degree of abnormality, principally stenosis, over and above the small size. Most often the TV abnormality does not need to be addressed early, in part because right heart function does not have to be fully normal for adequate pulmonary blood flow and also because some
62
J.E. Foker et al. / Progress in Pediatric Cardiology 29 (2010) 61–63
Fig. 1. An evaluation and treatment plan for the PAIVS spectrum must be complex to deal with the lesions that are encountered. The study methods to assess the lesions are listed on the left-hand side and the procedures that may be used on the right. The algorithm favors the 2VR track and the diagnostic methods and procedures needed to achieve this outcome are presented in bolder type. Those studies and procedures which are less commonly needed or used on the 2VR track are in less bold type. Although the secondary procedures such as relief of residual RV obstruction or TV valve repair are not often required, they are considered important to achieve the full potential of the 2VR. On the far right are the palliative treatment endpoints and these are indicated by dotted lines.
type of shunt (aorto-pulmonary or PDA) will be present. Operative repair will be easier when the tricuspid valve apparatus has grown. On occasion, a significant Epstein's malformation of the tricuspid valve will be present, and because of the regurgitation, the RV is usually not severely hypoplastic. The possibility of two regurgitant valves (TV and PV) in series after the placement of an RVOT patch makes an adequate cardiac output unlikely without TV repair or replacement. Although, a significant Epstein's malformation complicates the pathway to a 2VR, a regurgitant TV also makes the venous pressures less favorable for a SVR. This combination is a difficult one, although the first apparent survivor of this combination which required repair of both components in infancy is now 25 years old and has had his second TV replacement. With the evaluation accomplished, the procedures can be planned. RV cavitary hypoplasia is very common and when severe, its growth potential has been questioned. Taken together with TV hypoplasia and significant RV-CACs, the initial outlook may be daunting in terms of a satisfactory outcome and, in particular, for the likelihood of a 2VR. The data now indicate, however, that considerable growth potential exists even for very hypoplastic structures and many of the other anatomic problems can be treated. The function of the pulmonary ventricle can be met temporarily in several ways which allows time for RV growth. Assigning these infants to a SVR repair track in the newborn period is unnecessary and even unwise because of the continuing consequences of the hypertensive RVs and RV-CACs. We believe the evidence suggests that the great majority of these patients should be placed on a 2VR track and, even if this goal is not
reached, a more normal coronary circulation and a decompressed RV will pay dividends in the long run. As shown on the algorithm, the first procedure is usually in the newborn period. At some centers, if significant RV-CACs are not present, a balloon pulmonary valvotomy may be done. This procedure alone does not encourage TV flow by ASD restriction or provide for additional pulmonary blood flow if needed. The relief of the RVOT obstruction, moreover, is incomplete and its role is yet to be determined. The initial operation will begin with off-bypass ligation of RVCACs, if present. When significant RV-CACs are present, the myocardium typically looks yellowish, blotchy and is irritable, reflecting the hypoxic perfusion from the RV. Each connection is located, sometimes with the help of surface echo, and reversibly ligated. If no WMA or sign of injury appears, the ligation is completed. If the ligatures are not tolerated, only a shunt should be done. Following ligation of the connections, the RV can be decompressed without the risk of a significant myocardial steal. Effective relief of the PA will be accomplished by the placement of a transannular outflow track patch (RVOTP). In the more severe cases, the infundibulum is solid muscle and must be cored out to reach the RV cavity and effectively relieve the obstruction. To encourage TV flow and, presumably provide an effective growth signal, the ASD/PFO is snared and adjusted off-bypass to achieve a mild right-to-left gradient of about 4 mm Hg (the defect is usually about 4 mm in diameter). This mild restriction balances the need for an adequate contribution to cardiac output by the right-to-left shunting, with sufficient TV flow to stimulate right-sided growth. The ASD should
J.E. Foker et al. / Progress in Pediatric Cardiology 29 (2010) 61–63
be only mildly restrictive initially and the pressure gradient will usually not increase much as both the child and the TV grow. The question at the first operation will be whether or not to include a systemic to pulmonary artery shunt. With effective relief of outflow obstruction, the RV will collapse. Depending on the degree of hypoplasia, the RV might take only days to relax and produce effective forward flow measured at the TV (often increased TV flow will be accompanied by decreased trans-atrial flow). During this time, the PDA will be able to provide adequate pulmonary blood flow. If the RV is more hypoplastic, a period of growth, in addition to improved compliance, will also be required. When the right heart structures are too small to provide an adequate pulmonary blood flow within about 7–10 days, a systemic to right PA shunt should be placed. In general, a patient with an RV Z score of −4.0 or smaller will benefit from a shunt and PDA ligation, which will make the time of hospitalization shorter. A shunt placed from the right lateral aspect of the ascending aorta to the right pulmonary artery will provide adequate pulmonary blood flow and not run directly backward into the RV. Although the operative approach outlined is not intrinsically destabilizing and results in normoxic, antegrade perfusion, it does add stress to these often unstable infants and a few have benefitted from a period of post-operative ECMO support. With the conditions of complete relief of RVOT obstruction and a mildly restrictive ASD met, the surprisingly good growth potential of these hypoplastic right-sided structures will be realized. For at least half of these infants, this will be the last procedure needed for the foreseeable future. Over the succeeding months, there are a number of possible issues that might need to be addressed. As noted, about 25% of TVs have a structural abnormality in addition to hypoplasia and after a period of growth, the lesion will be more apparent and easier to treat. In some, the problem will be valvar stenosis which can be improved by open valvotomy or balloon dilation. The open valvoplasty allows for more precision in the division of the fused commissures. In addition, fused papillary muscles and/or anomalous muscle bands may also contribute to obstruction and these are best divided under direct vision. Additional obstructing tissue on the valve itself can also be resected. These additional procedures, if necessary, should produce increased forward flow through the TV, stimulate RV growth, and improve the physiological outcome. Prior to relief of the pulmonary atresia at the first operation, some degree of tricuspid valve regurgitation is present in most. With effective opening of the RVOT, the valve leakage usually largely resolves. For a few TVs, however, mild–moderate leakage continues. If the insufficiency reaches a significant level, later valve repair may be helpful. There may also be residual deformities of the RV that require later repair to insure the adequacy of the right-sided output. Obstructions in the outflow tract will likely reduce flow, impair the remodeling of the RV into a volume ventricle, and limit the regression of the hypertrophy initially present. Our evaluation of the literature on
63
PAIVS supports the conclusion that even a moderate amount of RV hypertension (e.g. 50–60 mm Hg) will compromise RV catch-up growth. Evaluation of the ASD should be undertaken if the patient remains too cyanotic and the right heart structures have failed to grow. If the ASD appears to be too large, it should be reduced in size or even eliminated. The consequences of closing the ASD can easily be determined by temporary balloon occlusion in the catheterization laboratory. If the ASD was originally snared, it can be reduced in size by a relatively small procedure and it can be eliminated by either device closure or cinching down completely the ASD snare. The possibilities of a later relief of residual RVOT obstruction or TV repair are included in the algorithm, not because they are frequent but because either of these two residual lesions will decrease flow across the TV and, hence, limit RV catch-up growth. In our series, the patients who had another operation to relieve RVOT obstruction were those infants born without a main pulmonary artery and had a conduit placed between the RV and the PA confluence which was later outgrown. Nevertheless, a conversion to a 1 1/2 ventricle repair can be used if the RV does not grow adequately or the TV continues to have significant obstruction. With attention to the details of the approach, this outcome should be unusual. As the child passes through the teenage years, the effect of having no pulmonary valve (PV) may become apparent. If the RV starts to dilate, PV placement may become necessary. These children will resemble a well repaired tetralogy of Fallot and, therefore, the absence of a PV may become noticeable. Both the information in this issue's articles and our approach to PAIVS patients guide this algorithm. The basic and clinical studies presented in this issue illustrate compellingly that this is a reversible developmental problem of several components. The first that must be dealt with is the presence of significant RV-CACs which previously have precluded RV decompression. The ability to ligate the connections off-bypass will directly assess and treat this problem and allow the majority of PAIVS patients to proceed to a 2VR. Clearly, the growth potential of even very hypoplastic right heart structures is substantial and catch-up growth will occur if the conditions cited above are met. Even if adequate right-sided growth does not occur, the continuing adverse consequences of the RV-CACs and the hypertensive RV will have been eliminated. Finally, there would seem to be no longer term problems (outside of the absent PV) that will surface which cannot be said of a SVR. Our conclusion is that the large majority of these patients will end up with a 2VR and the long-term benefits of this approach. Acknowledgment Supported in part by the Robert and Sharon Kaster Endowment for Pediatric Cardiac Surgical Science. We are grateful for the expert figure preparation of Brian Harvey and manuscript preparation of Jeanne Traaseth.
Contents lists available at ScienceDirect
Progress in Pediatric Cardiology j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / p p e d c a r d
Treatment algorithm for Pulmonary Atresia with Intact Ventricular Septum John E. Foker a,⁎, James M. Berry b, Lee A. Pyles b a b
Division of Cardiothoracic Surgery, University of Minnesota, Minneapolis, MN, USA Division of Cardiothoracic Pediatric Cardiology, University of Minnesota, Minneapolis, MN, USA
a r t i c l e
i n f o
Available online 27 March 2010 Keywords: Pulmonary atresia with intact ventricular septum Hypoplasia SVR 2VR
a b s t r a c t The articles in this issue reveal the complexity of the PAIVS spectrum and the methods of treatment that are currently being used. Despite the complexity, the articles provide greater understanding of the developmental events leading to these lesions and the methods that could be used to reverse them. Taken together, the evidence certainly favors embarking on a 2VR track whenever possible. The number of completed biventricular repairs will be increased and also the adverse later consequences of a hypertensive RV and persisting significant RV to coronary artery connections will be eliminated when they are not. The algorithm, therefore, is heavily weighted to 2VRs. © 2010 Elsevier Ireland Ltd. All rights reserved.
Progress in the treatment of PAIVS patients is the goal of this special issue. The articles have provided important information which suggests that the patients should be placed on a 2VR track initially and, even if they eventually fall short, the situation will also be improved for those who end up with a SVR. A reasonable expectation is that a substantial increase in 2VRs should result and produce a similar improvement in long-term outcomes for the group. As opposed to beginning with the goal of a 2VR, a number of centers have attempted to improve the results by deciding at the initial evaluation whether a SVR or a 2VR track would be most appropriate. Usually, the degree of right heart hypoplasia is the deciding factor in choosing the treatment track. By sharpening the criteria for this stratification, some centers have achieved a reduction in overall mortality although not in SVR rates. The initial assignment into a SVR track, moreover, disregards the considerable growth potential and essentially eliminates the likelihood of having two functioning ventricles. The algorithm presented here, in contrast, begins with the assumption that a 2VR or something close to it is possible in these infants. The enlistment of the growth potential, wherever possible, should provide the best physiological solution with the greatest longterm benefit. Futhermore, leaving a hypertensive RV and persisting RVCACs predictably have adverse consequences into adulthood, as presented in this issue by Tanoue et al and Ekman-Joelsson et al. Consequently, even if a 2VR is not completely realized, eliminating these lesions will still improve the long-term outlook. The algorithm portrays, in bolder type, the evaluations needed and the basic components required to achieve a 2VR outcome (Fig. 1). The algorithm also includes, in lighter type, the other procedures that may be needed to correct residual lesions, when present, to improve the 2VR ⁎ Corresponding author. University of Minnesota, 420 Delaware St. SE MMC 495, Minneapolis, MN 55455, United States. Tel.: + 1 612 625 0910; fax: + 1 612 625 4106. E-mail address: [email protected] (J.E. Foker). 1058-9813/$ – see front matter © 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ppedcard.2010.02.005
result. Because of the spectrum of the lesions and the difficulties in achieving complete repair initially, some patients may require additional procedures for optimum catch-up growth and function. For those patients who are only suitable for a palliative repair, the various possibilities of shunts, transplantation, and a Fontan procedure (SVR) are indicated with dashed lines. Diagnosis often begins by fetal echo and someday, fetal treatment may also be commonplace. For now, however, in utero valvotomies are done only at a small handful of centers. More time and experience will be required to accurately list the indications, procedures and likely results. Certainly, providing forward flow will encourage RV and TV growth and should limit the degree of hypoplasia although additional procedures to relieve residual RV outflow track obstruction will be needed. Nevertheless, when applicable, a satisfactory 2VR should be the outcome and in utero treatment will likely be used more in the future. The initial newborn evaluation will usually establish the details of PAIVS. Among these, the presence or absence of significant RV-CACs and associated coronary artery lesions, as well as the size and quality of the tricuspid valve are important issues. If there are significant RV-CACs, the evaluation should attempt to confirm that the coronary arteries are connected to the aorta. This is an important developmental event that rarely does not take place. Even a brief antegrade signal in diastole establishes continuity through to the aorta. If no continuity between aorta and coronary arteries exists transplantation seems to be the best option. The evaluation should then proceed to determine the location of the connections and identify, with the aid of angiography, significant stenoses resulting from the associated arteritis. From these studies, a plan for the treatment of the RV-CACs should emerge. The size of the TV is important and, in addition, about 25% of the valves have some degree of abnormality, principally stenosis, over and above the small size. Most often the TV abnormality does not need to be addressed early, in part because right heart function does not have to be fully normal for adequate pulmonary blood flow and also because some
62
J.E. Foker et al. / Progress in Pediatric Cardiology 29 (2010) 61–63
Fig. 1. An evaluation and treatment plan for the PAIVS spectrum must be complex to deal with the lesions that are encountered. The study methods to assess the lesions are listed on the left-hand side and the procedures that may be used on the right. The algorithm favors the 2VR track and the diagnostic methods and procedures needed to achieve this outcome are presented in bolder type. Those studies and procedures which are less commonly needed or used on the 2VR track are in less bold type. Although the secondary procedures such as relief of residual RV obstruction or TV valve repair are not often required, they are considered important to achieve the full potential of the 2VR. On the far right are the palliative treatment endpoints and these are indicated by dotted lines.
type of shunt (aorto-pulmonary or PDA) will be present. Operative repair will be easier when the tricuspid valve apparatus has grown. On occasion, a significant Epstein's malformation of the tricuspid valve will be present, and because of the regurgitation, the RV is usually not severely hypoplastic. The possibility of two regurgitant valves (TV and PV) in series after the placement of an RVOT patch makes an adequate cardiac output unlikely without TV repair or replacement. Although, a significant Epstein's malformation complicates the pathway to a 2VR, a regurgitant TV also makes the venous pressures less favorable for a SVR. This combination is a difficult one, although the first apparent survivor of this combination which required repair of both components in infancy is now 25 years old and has had his second TV replacement. With the evaluation accomplished, the procedures can be planned. RV cavitary hypoplasia is very common and when severe, its growth potential has been questioned. Taken together with TV hypoplasia and significant RV-CACs, the initial outlook may be daunting in terms of a satisfactory outcome and, in particular, for the likelihood of a 2VR. The data now indicate, however, that considerable growth potential exists even for very hypoplastic structures and many of the other anatomic problems can be treated. The function of the pulmonary ventricle can be met temporarily in several ways which allows time for RV growth. Assigning these infants to a SVR repair track in the newborn period is unnecessary and even unwise because of the continuing consequences of the hypertensive RVs and RV-CACs. We believe the evidence suggests that the great majority of these patients should be placed on a 2VR track and, even if this goal is not
reached, a more normal coronary circulation and a decompressed RV will pay dividends in the long run. As shown on the algorithm, the first procedure is usually in the newborn period. At some centers, if significant RV-CACs are not present, a balloon pulmonary valvotomy may be done. This procedure alone does not encourage TV flow by ASD restriction or provide for additional pulmonary blood flow if needed. The relief of the RVOT obstruction, moreover, is incomplete and its role is yet to be determined. The initial operation will begin with off-bypass ligation of RVCACs, if present. When significant RV-CACs are present, the myocardium typically looks yellowish, blotchy and is irritable, reflecting the hypoxic perfusion from the RV. Each connection is located, sometimes with the help of surface echo, and reversibly ligated. If no WMA or sign of injury appears, the ligation is completed. If the ligatures are not tolerated, only a shunt should be done. Following ligation of the connections, the RV can be decompressed without the risk of a significant myocardial steal. Effective relief of the PA will be accomplished by the placement of a transannular outflow track patch (RVOTP). In the more severe cases, the infundibulum is solid muscle and must be cored out to reach the RV cavity and effectively relieve the obstruction. To encourage TV flow and, presumably provide an effective growth signal, the ASD/PFO is snared and adjusted off-bypass to achieve a mild right-to-left gradient of about 4 mm Hg (the defect is usually about 4 mm in diameter). This mild restriction balances the need for an adequate contribution to cardiac output by the right-to-left shunting, with sufficient TV flow to stimulate right-sided growth. The ASD should
J.E. Foker et al. / Progress in Pediatric Cardiology 29 (2010) 61–63
be only mildly restrictive initially and the pressure gradient will usually not increase much as both the child and the TV grow. The question at the first operation will be whether or not to include a systemic to pulmonary artery shunt. With effective relief of outflow obstruction, the RV will collapse. Depending on the degree of hypoplasia, the RV might take only days to relax and produce effective forward flow measured at the TV (often increased TV flow will be accompanied by decreased trans-atrial flow). During this time, the PDA will be able to provide adequate pulmonary blood flow. If the RV is more hypoplastic, a period of growth, in addition to improved compliance, will also be required. When the right heart structures are too small to provide an adequate pulmonary blood flow within about 7–10 days, a systemic to right PA shunt should be placed. In general, a patient with an RV Z score of −4.0 or smaller will benefit from a shunt and PDA ligation, which will make the time of hospitalization shorter. A shunt placed from the right lateral aspect of the ascending aorta to the right pulmonary artery will provide adequate pulmonary blood flow and not run directly backward into the RV. Although the operative approach outlined is not intrinsically destabilizing and results in normoxic, antegrade perfusion, it does add stress to these often unstable infants and a few have benefitted from a period of post-operative ECMO support. With the conditions of complete relief of RVOT obstruction and a mildly restrictive ASD met, the surprisingly good growth potential of these hypoplastic right-sided structures will be realized. For at least half of these infants, this will be the last procedure needed for the foreseeable future. Over the succeeding months, there are a number of possible issues that might need to be addressed. As noted, about 25% of TVs have a structural abnormality in addition to hypoplasia and after a period of growth, the lesion will be more apparent and easier to treat. In some, the problem will be valvar stenosis which can be improved by open valvotomy or balloon dilation. The open valvoplasty allows for more precision in the division of the fused commissures. In addition, fused papillary muscles and/or anomalous muscle bands may also contribute to obstruction and these are best divided under direct vision. Additional obstructing tissue on the valve itself can also be resected. These additional procedures, if necessary, should produce increased forward flow through the TV, stimulate RV growth, and improve the physiological outcome. Prior to relief of the pulmonary atresia at the first operation, some degree of tricuspid valve regurgitation is present in most. With effective opening of the RVOT, the valve leakage usually largely resolves. For a few TVs, however, mild–moderate leakage continues. If the insufficiency reaches a significant level, later valve repair may be helpful. There may also be residual deformities of the RV that require later repair to insure the adequacy of the right-sided output. Obstructions in the outflow tract will likely reduce flow, impair the remodeling of the RV into a volume ventricle, and limit the regression of the hypertrophy initially present. Our evaluation of the literature on
63
PAIVS supports the conclusion that even a moderate amount of RV hypertension (e.g. 50–60 mm Hg) will compromise RV catch-up growth. Evaluation of the ASD should be undertaken if the patient remains too cyanotic and the right heart structures have failed to grow. If the ASD appears to be too large, it should be reduced in size or even eliminated. The consequences of closing the ASD can easily be determined by temporary balloon occlusion in the catheterization laboratory. If the ASD was originally snared, it can be reduced in size by a relatively small procedure and it can be eliminated by either device closure or cinching down completely the ASD snare. The possibilities of a later relief of residual RVOT obstruction or TV repair are included in the algorithm, not because they are frequent but because either of these two residual lesions will decrease flow across the TV and, hence, limit RV catch-up growth. In our series, the patients who had another operation to relieve RVOT obstruction were those infants born without a main pulmonary artery and had a conduit placed between the RV and the PA confluence which was later outgrown. Nevertheless, a conversion to a 1 1/2 ventricle repair can be used if the RV does not grow adequately or the TV continues to have significant obstruction. With attention to the details of the approach, this outcome should be unusual. As the child passes through the teenage years, the effect of having no pulmonary valve (PV) may become apparent. If the RV starts to dilate, PV placement may become necessary. These children will resemble a well repaired tetralogy of Fallot and, therefore, the absence of a PV may become noticeable. Both the information in this issue's articles and our approach to PAIVS patients guide this algorithm. The basic and clinical studies presented in this issue illustrate compellingly that this is a reversible developmental problem of several components. The first that must be dealt with is the presence of significant RV-CACs which previously have precluded RV decompression. The ability to ligate the connections off-bypass will directly assess and treat this problem and allow the majority of PAIVS patients to proceed to a 2VR. Clearly, the growth potential of even very hypoplastic right heart structures is substantial and catch-up growth will occur if the conditions cited above are met. Even if adequate right-sided growth does not occur, the continuing adverse consequences of the RV-CACs and the hypertensive RV will have been eliminated. Finally, there would seem to be no longer term problems (outside of the absent PV) that will surface which cannot be said of a SVR. Our conclusion is that the large majority of these patients will end up with a 2VR and the long-term benefits of this approach. Acknowledgment Supported in part by the Robert and Sharon Kaster Endowment for Pediatric Cardiac Surgical Science. We are grateful for the expert figure preparation of Brian Harvey and manuscript preparation of Jeanne Traaseth.