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Atrioventricular Valve Repair in Patients With Single-ventricle Physiology: Mechanisms, Techniques of Repair, and Clinical Outcomes
Atrioventricular Valve Repair in Patients With Single-ventricle Physiology: Mechanisms, Techniques of Repair, and Clinical Outcomes Osami Honjo, MD, PhD, Luc Mertens, MD, PhD, and Glen S. Van Arsdell, MD Significant atrioventricular (AV) valve insufficiency in patient with single ventricle-physiology is strongly associated with poor survival. Herein we discuss the etiology and mechanism of development of significant AV valve insufficiency in patients with single-ventricle physiology, surgical indication and repair techniques, and clinical outcomes along with our 10-year surgical experience. Our recent clinical series and literature review indicate that it is of prime importance to appreciate the high incidence and clinical effect of the structural abnormalities of AV valve. Valve repair at stage II palliation may minimize the period of volume overload, thereby potentially preserving post-repair ventricular function. Since 85% of the AV valve insufficiency was associated with structural abnormalities, inspection of an AV valve that has more than mild to moderate insufficiency is recommended because they are not likely to be successfully treated with volume unloading surgery alone. Semin Thorac Cardiovasc Surg Pediatr Card Surg Ann 14:75-84 © 2011 Published by Elsevier Inc.
Introduction
B
ecause the Fontan circulation is crucially dependent on a single energy source, ie, a systemic single-ventricle, atrioventricular (AV) valve function is as important as ventricular function to maintain adequate oxygen delivery. A number of the initial ‘Ten Commandment’ risk factors for a Fontan have largely been overcome.1 Such is not the case with AV valve function. Many clinical series have shown significantly worse survival in patients with single-ventricle physiology who had significant AV valve insufficiency.2-5 In an effort to overcome the risk of insufficiency, various repair techniques have evolved.2,6,7 Despite some success, AV valve insufficiency is still a strong risk factor of failure of cavopulmonary circulation in the current era.6,8 In this review, we discuss the etiology and mechanism of development of significant AV valve insufficiency in patients with single-ventricle physiology, surgical indication and repair techniques, and clinical outcomes along with our 10-year surgical experience of this challenging entity.
From The Labatt Family Heart Centre, The Hospital for Sick Children and The University of Toronto, Canada. Address correspondence to Glen S. Van Arsdell, MD, Division of Cardiovascular Surgery, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada, M5G 1X8; E-mail: [email protected]
1092-9126/11/$-see front matter © 2011 Published by Elsevier Inc. doi:10.1053/j.pcsu.2011.02.001
Development of AV Valve Insufficiency Mechanisms of development of AV valve insufficiency in the single-ventricle physiology are complex and multifactorial. The three key factors that trigger the development of significant AV valve insufficiency are chronic volume overload, structural AV valve abnormalities, and myocardial damage/ischemia (Fig. 1). Chronic Volume Overload Many patients with a single-ventricle physiology who undergo a neonatal palliation with a systemic-to-pulmonary shunt (Blalock-Taussig shunt or Norwood type procedure) will result in a shunt-dependent in-parallel circulation. The systemic single ventricle is exposed to considerable volume overload until the time of stage II palliation, where cavopulmonary shunt type operation makes circulation in-series, minimizing volume overload.9 Chronic volume overload causes progressive ventricular dilatation,10 annular dilation, and an effective leaflet tethering, leading to malcoaptation of the leaflets. Structural Abnormalities of AV Valve AV valve leaflets and the subvalvular apparatus in a functional single-ventricle heart are often abnormal. Stamm et al11 examined 82 specimens with hypoplastic left heart syndrome (HLHS) in a view of morphologic tricuspid valve as a systemic AV valve. One third of the specimens had moderate or severe tricuspid valvular dysplasia, which was particularly 75
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Figure 1 The mechanisms of development of significant AV valve insufficiency. We emphasize the importance of structural AV valve abnormalities as one of the most imperative triggers in the development of AV valve insufficiency in this patient group.
common in the presence of a patent mitral valve. Other abnormalities included bileaflet or, rarely, quadraleaflet tricuspid valve (12%), accessory orifices, prolapse of the anterior leaflet, and, rarely, Ebstein’s malformation. Others have described that up to 20% of the autopsy specimens of functional single left ventricles (ie, tricuspid atresia and pulmonary atresia with intact ventricular septum) had structural abnormalities in their morphologically mitral valve.12,13 The common AV valve leaflets in the setting of double inlet AV connection are dysplastic in 55% of cases.14 What the autopsy series clearly shows is that not all AV valve insufficiency in singleventricle physiology is ‘functional’ in nature. Tricuspid Valve Because it is designed to sustain the competency in the lowresistance pulmonary circulation, the tricuspid valve is thought to be more susceptible to pressure or volume overload. In patients who had more than moderate pulmonary hypertension (pulmonary artery pressure, 50 to 69 mmHg) in the setting of a biventricular physiology, approximately Table 1 Classification and Prevalence of Mitral Valve Anomalies According to the Carpentier’s Functional Classification (n ⴝ 145) Type
Percentage
Type I: Normal leaflet motion 1. Annular dilatation 2. Cleft 3. Leaflet defect Type II: Leaflet prolapse 1. Chordal elongation 2. Papillary muscle elongation 3. Absence of chordae Type III Restricted leaflet motion A. Normal papillary muscle 1. Commissure papillary muscle fusion 2. Short chordae B. Abnormal papillary muscle 1. Parachute valve 2. Hammock valve 3. Papillary muscle hypoplasia
21.0 4.8 12.0 4.1 54.5 31.7 16.5 6.2 24.1
Modified and adapted from Chauvaud et al.20
5.5 4.8 3.4 8.2 2.0
one third of patient had more than moderate tricuspid valve insufficiency, with half having competent or mildly insufficient tricuspid valves.15 Likewise, chronic volume overload does not always result in significant tricuspid valve insufficiency. Among 30 adult patients with unrepaired atrial septal defect with a mean pulmonary-to-systemic flow ratio of 2.4:1, one fifth developed more than moderate tricuspid valve insufficiency at 25 years.16 There is no question that significant pressure and/or volume overload play a role in developing tricuspid valve insufficiency. However, the mechanism of significant tricuspid valve insufficiency is more complex and should be the combination of pressure and/or volume overload with other factors (ie, ventricular and annular dilatation, ventricular septal geometry, ventricular function, and structural abnormalities of the valve leaflets). Myocardial Damage/Ischemia and Ventricular Dysfunction Ventricular dysfunction leads to progressive ventricular dilatation and changes in geometry of the ventricle and subvalvular apparatus, including papillary muscle. The mechanism for dysfunction has been described to include circulatory arrest, ischemia-reperfusion injury, hemodilution, inflammatory response, high post-bypass systemic vascular resistance, and intrinsic vulnerability of neonatal systemic right ventricle.17 Our recent experience showed approximately one third of the infants with Norwood physiology had at least mild AV valve insufficiency at pre-stage II evaluation.18 Kuroda et al10 showed decrease in ejection fraction of the sysTable 2 Type of AV Valve Abnormalities in 58 Patients Who Underwent AV Valve Repair in The Hospital for Sick Children (1998-2008) Abnormalities
Percentage
Annular dilatation Cleft Prolapse Chordal elongation Restriction Dysplasia Papillary muscle abnormalities
77 21 51 42 49 52 8
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77
temic ventricle after placement of a systemic-to-pulmonary shunt. In addition, a diastolic run off through the systemicto-pulmonary shunt may reduce effective coronary artery blood flow, thereby potentially leading to ventricular dysfunction. Once significant AV valve insufficiency occurs, it creates a negative feedback loop where further volume overload of the regurgitant volume worsens ventricular and annular dilatation (Fig. 1).
Pathophysiology of AV Valve Insufficiency The types of AV valve abnormalities and their frequency described by Carpentier and colleagues19,20 are listed in Table 1. The primary mechanisms of AV valve insufficiency in 58 patients who underwent AV valve repair from 1998 to 2008 at The Hospital for Sick Children (Toronto, Canada) are shown in Table 2. The vast majority of patients had annular dilatation. Prolapse, restriction, and dysplasia were seen in approximately half the patients, indicating that most patients had more than one AV valve abnormality. In fact, all 58 patients in our series had at least two types of abnormality. Of interest, the most common mechanism of AV valve insufficiency was prolapse, accounting for 46% of the patient population. Of note, AV valve insufficiency in the single-ventricle patient is often associated with dysplasia of the leaflets. Restriction was seen in approximately half the patients, but was rarely the primary mechanism of AV valve insufficiency (2%). The Myth of Volume Unloading With Stage II Palliation Stage II palliation with a cavopulmonary connection is thought to volume unload the single ventricle. While changes in ventricular volume and annular dimension can be documented,21 those changes did not necessarily result in improvement in AV valve insufficiency.22,23 Mahle et al22 showed that only six (16%) out of 36 patients who had moderate or severe AV valve insufficiency at the time of bidirectional cavopulmonary shunt (BCPS) had improved AV valve insufficiency grade without AV valve repair. Ten (28%) patients subsequently required AV valve repair, indicating that the majority of AV valve insufficiency is not purely ‘functional’. Our recent series showed the vast majority (85%) of the patients who required AV valve repair had structural abnor-
Table 3 Primary Mechanisms of AV Valve Insufficiency in 58 Patients With Single-Ventricle Physiology* Right Left Ventricle Ventricle Number Mechanism (n ⴝ 48; 83%) (n ⴝ 8; 13%) (%) Annular dilatation Prolapse Dysplasia Cleft Restriction
8
0
8 (15)
22 12 1 1
2 6 0 0
24 (46) 17 (35) 1 (2) 1 (2)
*Two patients who had indeterminate ventricular morphology had dysplasia as the primary mechanism of AV valve insufficiency.
Figure 2 The timing of AV valve repair in 58 patients with singleventricle physiology who underwent AV valve repair during staged palliation.
malities of the AV valve (Table 2).24 In other words, only 15% of the AV valve insufficiency had pure annular dilatation as the primary mechanism (Table 3). Additionally, newly emerging volumetric data from magnetic resonance imaging shows that collateral formation leads to a Qp:Qs of 1 following a BCPS.25 These magnetic resonance imaging findings suggest that the volume unloading of a BCPS appears to be temporary. Our policy has been to inspect and attempt repair for AV valve insufficiency of mild to moderate or greater at the time of the cavopulmonary connection. That policy will continue, given that an anatomic abnormality is identified in 85% of cases. When Should We Repair the AV Valve? The timing of AV valve repair in our institute is shown in Fig. 2. Approximately two thirds of patients underwent AV valve repair at stage II palliation, and just less than one fifth of the patients underwent AV valve repair either between the BCPS and Fontan or at the Fontan procedure. In general, we try to avoid repair at the time of a Fontan procedure unless it is a simple repair requiring limited operative time. It is rare to intervene on the AV valve at stage I palliation or in the neonatal time frame. First of all, it is rare to have significant AV valve insufficiency in neonates at presentation, and secondly, neonates with complex single-ventricle anatomy with significant AV valve insufficiency may be triaged to the primary transplantation pathway.
Surgical Techniques Evaluation of the AV Valve Direct inspection of the valve and apparatus and inspection with a balanced fluid insufflation test is performed. Special attention is given to each AV valve component: annular di-
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78 Table 4 The Repair Techniques Used in 58 Single-Ventricle Patients Who Underwent AV Valve Repair Operative Techniques Annuloplasty Commissuroplasty* Valvuloplasty Chordal repair Cleft closure Edge-to-edge repair* Papillary muscle repair
Number (%) 46 (85) 29 (54) 12 (22) 2 (4) 18 (33) 17 (29) 1 (2)
*We used to call the technique that is now called “edge-to-edge repair” as “commissuroplasty or artial closure of commissure.” Therefore, there are some overlaps between these two categories.
mension, commissural leak, prolapse or restriction of the leaflets, leaflet abnormalities (ie, cleft, dysmorphism or dysplasia), subvalvular abnormalities (ie, chordal fusion or elongation), and papillary muscle abnormalities. The repair techniques we used in 58 single-ventricle patients who underwent AV valve repair are shown in Table 4. Annular Dilatation Partial annuloplasty and commissuroplasty are the commonly used techniques for a generalized central regurgitation because of annular dilatation and subsequent poor coaptation and/or localized prolapse of the leaflet(s). We typically use 5-0 polypropylene or 4-0 polyester sutures to locally reduce the annulus size along the commissure(s), where the regurgitant jet mainly comes from. This maneuver is essentially a functional commissuroplasty on the corresponding commissure. Anatomic commissuroplasty is achieved with 6-0 or 7-0 polypropylene simple interrupted sutures. Bove and colleagues6,26 suggested a rather extensive partial annuloplasty to repair the tricuspid valve in HLHS hearts (Fig. 3). Running parallel mattress sutures are placed along the annulus supporting the inferior leaflet between its zones of apposition with the anterior and septal leaflets (Fig. 3A), obliter-
ating the inferior leaflet (Fig. 3B). This repair essentially forms a bicuspid valve. A semi-circular or circular annuloplasty has been described. Kanter et al27 reported the De Vega type semi-circular annuloplasty for functional tricuspid valve insufficiency associated with various congenital heart diseases. Imai et al2 described a circular annuloplasty for various types of AV valve morphology. A 2-0 or 3-0 polytetrafluoroethylene suture is passed through the annulus circumferentially (Fig. 4A), and the full circular purse-string suture is tied over a 22 or 24 mm Hegar’s dilator (Fig. 4B). The suture was placed on the leaflet itself at the area of conduction system. Our preference is to use the partial localized annuloplasty, rather than the circular annuloplasty, to effectively reduce the annulus size in the area of regurgitation ,and also to leave the growth potential to the AV valve annulus.28 Insertion of an annuloplasty ring is also an option for older children and adolescents who have a nearly adult-size AV valve annulus. Prolapse Prolapse is the most common pathophysiology of congenital mitral valve insufficiency,20 as well as the AV valve insufficiency in single-ventricle physiology24 (Tables 1 and 2). A localized or generalized prolapse with essentially normal chordae and subvalvular apparatus are most commonly treated with annuloplasty and/or commissuroplasty.26 If elongation of the chordae and/or papillary muscle is the mechanism of prolapse, chordal shortening plasty can be applied (as described by Carpentier et al19). For chordal rupture or local deficiency, the chordae could be transposed from the opposite leaflet,19 although this technique is not always feasible in the morphologically tricuspid valve or common AV valve. Alternatively, chordal replacement with polytetrafluoroethylene sutures has been shown to be a durable option.29 This technique has been used in morphologically mitral and tricuspid valves.30,31 We and others have used edge-to-edge leaflet repair as a means of managing single-leaflet prolapse. The technique was originally described by Alfieri and colleagues32,33 as a
Figure 3 The extensive partial annuloplasty obliterating the inferior leaflet. This technique essentially forms a bileaflet valve. (Modified and adapted from the original description by Ohye et al.6)
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Figure 4 The circular annuloplasty technique for the common AV valve. A, A large polytetrafluoroethylene suture is passed through the annulus circumferentially. B, The suture is tied over a 22 or 24 mn Hagar’s dilator. (Modified and adapted from the original description by Imai et al.2)
technique to repair mitral valve prolapse in adults, and has subsequently been applied to tricuspid valves and AV valves. Ando and Takahashi7 delineated the edge-to-edge strategy in 22 single-ventricle patients (Fig. 5). For the common AV valve, the superior and inferior bridging leaflets are sutured together, along with cleft closure and/or additional closure of the commissure(s), between the non-coapting leaflets (Figs. 5A and B). In the tricuspid valve, the free edges of the anterior and septal leaflets are sutured together, making two effective orifices (Fig. 5C). Alternatively, the commissure between the anterior and septal commissure could be completely obliterated if the effective orifice size is large enough (Fig. 5D). Alfieri et al34 further extended this concept and reported a ‘clover technique’ to repair traumatic tricuspid insufficiency, where the free edges of all three leaflets are sutured together (Fig. 6). Double orifice techniques have been reported in the various configurations, especially for repairing common AV valve. Our surgical strategy is to first apply annuloplasty and commissuroplasty at the zone of appositions of the affected leaflets. Shortening of the chordae and/or papillary muscle was occasionally used for repairing chordal elongation in our series (6%), but chordal transposition or artificial chordal replacement was barely used for repairing AV valve insufficiency in the single-ventricle physiology in our institute. The edge-to-edge type repair is one of our preferences of choice, especially for common AV valve morphology with free-floating leaflets with the absence of supporting subvalvular apparatus. Leaflet Abnormalities A cleft is a relatively common leaflet abnormality (21%; Table 2) in single-ventricle patients, typically with a common AV valve; but it also can be seen in the anterior leaflet of the tricuspid valve. Standard cleft closure is utilized (Fig. 7A). If there is a large cleft associated with deficient
leaflet tissue, a pericardial patch can be used to augment the leaflet.20 In the moderate to severely dysplastic AV valves, we often see multiple small gaps, irregular leaflet edge, and resultant minor prolapses along the edge of the leaflets (Fig. 7B). The dyslplastic leaflet linearity can be improved by individual closure of each gap with 7-0 prolene interrupted sutures. Also, we often see relatively large accessory ‘pseudo’ commissures on the leaflets more appropriately termed “leaflet dysmorphism” (Fig. 7C). The dysmorphic ‘commisures’ can have localize prolapse that is repaired with an edge-to-edge technique. Restriction Significant AV valve insufficiency purely caused by anatomic restriction of the leaflets is extremely rare (2%) in single-ventricle patients. Functional restriction was quite common and seen in 49% of our cohort. Functional restriction occurs when there is annular dilatation and secondary displacement of the papillary muscle, making a ‘tethering effect,’ which can be resloved by downsizing the annulus. If restrictive motion is caused by the structural abnormalities of the subvalvular apparatus, mobilization of chordae and papillary muscle can be performed according to Carpentier.19 One could apply the leaflet extension technique for a severely restricted leaflet.20 No patient required such techniques in our series. AV Valve Replacement Replacement of the AV valve is the last option after all the reconstructive or reparative approaches fail. In fact, there was no patient who had primary AV valve replacement in our series. A mechanical valve is the device of choice at our institute because of its long durability, but other institute prefers to use a biosynthetic valve.35 It is ideal to preserve the papillary muscle(s) and chordal attachment to restore ventricular function after AV valve replacement,35 although it is not al-
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Figure 5 Two common types of the edge-to-edge repair for repairing the morphologically common AV valve (A, B) and the tricuspid valve (C, D). A, The superior and inferior bridging leaflets are sutured together and the cleft is directly closed. B, A non-coapting commissure is entirely closed in addition to the edge-to-edge suture on the superior and inferior bridging leaflets. C, The anterior and septal leaflets are sutured together making two effective orifices. D, A con-coapting antero-septal commissure is totally obliterated in addition to the edge-to-edge suture. (Modified and adapted from the original description from Ando and Takahashi.7)
ways possible in the complex AV valve morphology. The incidence of heart block caused by prosthetic valve replacement in small children is substantially high.35,36 Post-Repair Evaluation Intraoperative assessment of AV valve repair by a transesophageal echocardiography (TEE) is of prime importance for the decision making process. If the regurgitation has not improved or is not less than mild, we will revise the repair if the surgeon’s assessment is that there is room for further im-
provement. Evaluation of ventricular function at this point is of great importance because our recent studies clearly showed that the postoperative ventricular function is the strongest indicator for survival.24 Less than moderate residual AV valve insufficiency on TEE is accepted. Our intent is to revise the repair for moderate or greater residual insufficiency. Attention should be given to interpret the regurgitation degree on the intraoperative TEE immediately after weaning from cardiopulmonary bypass. There is often some
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Figure 6 The clover technique described by Alfieri et al for repairing traumatic tricuspid valve insufficiency. The edges of all three leaflets are sutured together making three effective orifices. (Modified and adapted from the original description from Alfieri et al.34)
discrepancy in the regurgitation grade between the intraoperative TEE and postoperative transthoracic echocardiographic finding, where TEE often underestimates the subsequent regurgitation grade.37 We tend to accept mildto-moderate postoperative AV valve stenosis (mean pressure gradient, ⬍ 3-4 mmHg).
Clinical Outcomes Survival The natural and surgically modified survivals of the singleventricle patient with significant AV valve insufficiency have been consistently poorer than that in the single-ventricle patient with a competent AV valve. Barber et al,4 who reported survival of patients with HLHS undergoing Norwood proce-
dure between 1984 and 1987, showed a significantly worse survival in patients with significant tricuspid valve insufficiency (survival: 55% vs 35% at 1 year after Norwood procedure). Because no intervention was performed on the tricuspid valve in this population, this study provides a nice ‘natural history’ evaluation of the effect of AV valve insufficiency on survival. Imai et al2 showed a significantly worse survival in single-ventricle patients who required AV valve repair compared with patients with standard risks (5-year survival, 95% vs 84%). This series was conducted in the era of two-staged Fontan completion. Recent clinical series of AV valve repair at the time of Fontan had a reasonable hospital survival (100% operative survival).38 Ohye et al6 reported the largest series of 28 patients with HLHS who underwent tricuspid valve repair after Norwood
Figure 7 Our surgical strategies to repair dysplastic or dysmorphic tricuspid valve in HLHS hearts. A, Direct cleft closure along with annuloplasty (functional commissuroplasty) on the antero-inferior commissure. B, Repair of the irregular dysplastic leaflets. C, Repair of dysmorphic leaflets by means of the edge-to-edge type repair.
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Figure 8 A, The Kaplan-Meier survival curve of the single-ventricle patients who underwent AV valve repair compared with the matched control subjects (n ⫽ 50 in each group), showing the worse survival in the AV valve repair group compared with the standard-risk group. B, The subgroup who has successful AV valve repair with preserved ventricular function (n ⫽ 35) has an equivalent survival compared with the matched controls.
procedure, which essentially suggested that postoperative right ventricular function and residual tricuspid valve insufficiency are the major determinants for survival. The patients who had successful tricuspid valve repair (residual insufficiency, grade 0 to 2) with preserved right ventricular function had the best survival (survival rate without transplant, 88%). On the other hand, there was 80% mortality in patients with early or late right ventricular dysfunction regardless of the result of tricuspid valve repair. Our recent series, consisting of 58 patients with various types of single-ventricle physiology, had similar findings to the Ohye study. The patients who required AV valve repair have a worse survival compared with the matched control patients (Fig. 8A). Of importance, the subgroup who had a successful AV valve repair with preserved ventricular function had an equivalent early and long-term survival compared with matched controls (Fig. 8B). The predictors for death or transplant are listed on Table 5, suggesting the importance of ventricular function and residual AV valve sufficiency on the outcome.
Durability of AV Valve Repair Ohye et al6 reported that 15 out of 21 patients (71%) with HLHS who had a successful tricuspid valve repair continued to have none to mild tricuspid valve insufficiency at the median follow-up of 20 months. Ando and Takahashi7 showed that the regurgitation grade was mild or less in 77.3% in the edge-to-edge repair group compared with 38.7% in the conventional repair group at the mean follow-up period of 2 to 2.5 years. In our series, 10 of 58 patients (17%) required re-repair or replacement at the median follow-up period of 21 months.24 The AV valve morphology or mechanism of initial AV valve insufficiency did not influence the re-intervention rate. The mechanisms of recurrent AV valve insufficiency are listed in Table 6. All four patients who had dysplasia as the primary mechanism of recurrent AV valve insufficiency required replacement of the AV valve. The survival after re-repair or replacement was 70% at 1 and 3 years, and there was no difference between re-repair and replacement groups.
Summary Table 5 Predictors for Death/Transplant After AV Valve Repair Based on Cox Regression Model in 58 Patients Who Underwent AV Valve Repair
Significant AV valve insufficiency in the single-ventricle physiology has substantial negative impacts on the natural
Predictors
P Value
Cardiopulmonary bypass time Annular dilatation as the primary mechanism* Residual AV valve insufficiency grade Post-repair ventricular function
.02 .02 .03 .02
Table 6 The Mechanism of Recurrent AV Valve Insufficiency Requiring Re-Repair or Replacement
*Seventy-five percent of the patients who had annular dilatation as the primary mechanism had preoperative ventricular dysfunction and dilatation.
Mechanism
Number
Re-annular dilatation Dysplasia Cleft Double orifice
3 4 2 1
AV Repair in patients with single-ventricle physiology and surgical modified histories of this patient population. The combination of chronic volume overload, structural abnormalities of the AV valve, and myocardial damage/ventricular dysfunction trigger the development of AV valve insufficiency. Our recent clinical study and other pathological studies emphasize the importance of structural abnormalities of the AV valve on development of AV valve insufficiency and on clinical outcomes of AV valve repair. The fact that the vast majority of patients (85%) with significant AV valve insufficiency have structural abnormalities on the AV valve, which indicates that volume unloading surgery alone may not be enough to effectively reduce the degree of AV valve insufficiency. Post-repair survival is greatly influenced by post-repair ventricular function and residual AV valve insufficiency. Patients who have successful AV valve repair with preserved ventricular function have an equivalent early and long-term survival compared with standard-risk patients.
Proposed Strategy and Future Direction The lessons we learned from our recent clinical series and literature review are that it is of prime importance to appreciate the high incidence and clinical effect of the structural abnormalities of AV valve. Valve repair at stage II palliation may minimize the period of volume overload, thereby potentially preserving post-repair ventricular function. Inspection of AV valve structure and function is strongly recommended if a patient has mild-to-moderate or moderate AV valve insufficiency at the time of stage II palliation. We believe the strategy is justified based on an 85% incidence of valve structural abnormalities that are not likely to be successfully treated with volume unloading surgery alone.
Acknowledgment The authors would like to thank Nobuko Yamamoto for the illustrations.
References 1. Hosein RB, Clarke AJ, McGuirk SP, et al. Factors influencing early and late outcome following the Fontan procedure in the current era. The ’Two Commandments’? Eur J Cardiothorac Surg 2007;31:344-352; discussion 353 2. Imai Y, Takanashi Y, Hoshino S, et al. Modified Fontan procedure in ninety-nine cases of atrioventricular valve regurgitation. J Thorac Cardiovasc Surg 1997;113:262-268; discussion 269 3. Moak JP, Gersony WM. Progressive atrioventricular valvular regurgitation in single ventricle. Am J Cardiol 1987;59:656-658 4. Barber G, Helton JG, Aglira BA, et al. The significance of tricuspid regurgitation in hypoplastic left-heart syndrome. Am Heart J 1988;116: 1563-1567 5. Mayer JE Jr, Bridges ND, Lock JE, et al. Factors associated with marked reduction in mortality for Fontan operations in patients with single ventricle. J Thorac Cardiovasc Surg 1992;103:444-451; discussion 451-452 6. Ohye RG, Gomez CA, Goldberg CS, et al. Tricuspid valve repair in hypoplastic left heart syndrome. J Thorac Cardiovasc Surg 2004;127: 465-472 7. Ando M, Takahashi Y. Edge-to-edge repair of common atrioventricular or tricuspid valve in patients with functionally single ventricle. Ann Thorac Surg 2007;84:1571-1576; discussion 1576-1577
83 8. d’Udekem Y, Iyengar AJ, Cochrane AD, et al. The Fontan procedure: contemporary techniques have improved long-term outcomes. Circulation 2007;116(suppl):I157-I164 9. Berman NB, Kimball TR. Systemic ventricular size and performance before and after bidirectional cavopulmonary anastomosis. J Pediatr 1993;122:S63-S67 10. Kuroda O, Sano T, Matsuda H, et al. Analysis of the effects of the Blalock-Taussig shunt on ventricular function and the prognosis in patients with single ventricle. Circulation 1987;76:III24-II28 11. Stamm C, Anderson RH, Ho SY. The morphologically tricuspid valve in hypoplastic left heart syndrome. Eur J Cardiothorac Surg 1997;12:587592 12. Pinto RJ, Deshpande J, Dalvi BV. Mitral valve anomalies in tricuspid atresia: an autopsy study of 54 hearts. Cardiol Young 1997;7:163-171 13. Akiba T, Becker AE. Disease of the left ventricle in pulmonary atresia with intact ventricular septum. The limiting factor for long-lasting successful surgical intervention? J Thorac Cardiovasc Surg 1994;108:1-8 14. Stein JI, Smallhorn JF, Coles JG, et al. Common atrioventricular valve guarding double inlet atrioventricular connexion: natural history and surgical results in 76 cases. Int J Cardiol 1990;28:7-17 15. Mutlak D, Aronson D, Lessick J, et al. Functional tricuspid regurgitation in patients with pulmonary hypertension: is pulmonary artery pressure the only determinant of regurgitation severity? Chest 2009; 135:115-121 16. Shah D, Azhar M, Oakley CM, et al. Natural history of secundum atrial septal defect in adults after medical or surgical treatment: a historical prospective study. Br Heart J 1994;71:224-227; discussion 228 17. Wernovsky G, McElhinney DB, Tabbutt S. Postoperative management after first-stage palliation. In: Rychik J, Wernovsky G, editors. Hypoplastic left heart syndrome. Norwell, MA: Kluwer Academic Publishers; 2003; pp 107-128 18. Honjo O, Benson LN, Mewhort HE, et al. Clinical outcomes, program evolution, and pulmonary artery growth in single ventricle palliation using hybrid and Norwood palliative strategies. Ann Thorac Surg 2009; 87:1885-1892; discussion 1892-1893 19. Carpentier A. Cardiac valve surgery–the “French correction.” J Thorac Cardiovasc Surg 1983;86:323-337 20. Chauvaud S, Fuzellier JF, Houel R, et al. Reconstructive surgery in congenital mitral valve insufficiency (Carpentier’s techniques): long-term results. J Thorac Cardiovasc Surg 1998;115:84-92; discussion 93 21. Forbes TJ, Gajarski R, Johnson GL, et al. Influence of age on the effect of bidirectional cavopulmonary anastomosis on left ventricular volume, mass and ejection fraction. J Am Coll Cardiol 1996;28:1301-1307 22. Mahle WT, Cohen MS, Spray TL, et al. Atrioventricular valve regurgitation in patients with single ventricle: impact of the bidirectional cavopulmonary anastomosis. Ann Thorac Surg 2001;72:831-835 23. Reyes A 2nd, Bove EL, Mosca RS, et al. Tricuspid valve repair in children with hypoplastic left heart syndrome during staged surgical reconstruction. Circulation 1997;96(suppl):II-341-II-343; discussion II344-II-345. 24. Honjo O, Atlin C, Mertens L, et al. Atrioventricular valve repair in patients with functional single ventricle physiology: impact of ventricular and valve function and morphology on survival and reintervention. J Thorac Cardiovasc Surg 2011 [In press] 25. Grosse-Wortmann L, Al-Otay A, Yoo SJ. Aortopulmonary collaterals after bidirectional cavopulmonary connection or Fontan completion: quantification with MRI. Circ Cardiovasc Imaging 2009;2: 219-225 26. Bove EL, Ohye RG, Devaney EJ, et al. Tricuspid valve repair for hypoplastic left heart syndrome and the failing right ventricle. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu 2007;10:101104 27. Kanter KR, Forbess JM, Fyfe DA, et al. De Vega tricuspid annuloplasty for systemic tricuspid regurgitation in children with univentricular physiology. J Heart Valve Dis 2004;13:86-90 28. Honjo O, Ishino K, Kawada M, et al. Midterm outcome of mitral valve repair for congenital mitral regurgitation in infants and children. Interact Cardiovasc Thorac Surg 2006;5:589-593
84 29. Matsumoto T, Kado H, Masuda M, et al. Clinical results of mitral valve repair by reconstructing artificial chordae tendineae in children. J Thorac Cardiovasc Surg 1999;118:94-98 30. Reddy VM, McElhinney DB, Brook MM, et al. Repair of congenital tricuspid valve abnormalities with artificial chordae tendineae. Ann Thorac Surg 1998;66:172-176 31. Honjo O, Ishino K, Yoshizumi K, et al. Repair of a dysplastic tricuspid valve using artificial chordae: case report. J Heart Valve Dis 2006;15: 392-393 32. Fucci C, Sandrelli L, Pardini A, et al. Improved results with mitral valve repair using new surgical techniques. Eur J Cardiothorac Surg 1995;9: 621-626; discussion 626-627 33. Alfieri O, De Bonis M, Lapenna E, et al. “Edge-to-edge” repair for anterior mitral leaflet prolapse. Semin Thorac Cardiovasc Surg 2004; 16:182-187
O. Honjo, L. Mertens, and G.S. Van Arsdell 34. Alfieri O, De Bonis M, Lapenna E, et al. The “clover technique” as a novel approach for correction of post-traumatic tricuspid regurgitation. J Thorac Cardiovasc Surg 2003;126:75-79 35. Mahle WT, Gaynor JW, Spray TL. Atrioventricular valve replacement in patients with a single ventricle. Ann Thorac Surg 2001;72:182-186 36. Caldarone CA, Raghuveer G, Hills CB, et al. Long-term survival after mitral valve replacement in children aged ⬍5 years: a multi-institutional study. Circulation 2001;104(suppl 1):I143-I147 37. Honjo O, Kotani Y, Osaki S, et al. Discrepancy between intraoperative transesophageal echocardiography and postoperative transthoracic echocardiography in assessing congenital valve surgery. Ann Thorac Surg 2006;82:2240-2246 38. Kerendi F, Kramer ZB, Mahle WT, et al. Perioperative risks and outcomes of atrioventricular valve surgery in conjunction with Fontan procedure. Ann Thorac Surg 2009;87:1484-1488; discussion 1488-1489
Introduction
B
ecause the Fontan circulation is crucially dependent on a single energy source, ie, a systemic single-ventricle, atrioventricular (AV) valve function is as important as ventricular function to maintain adequate oxygen delivery. A number of the initial ‘Ten Commandment’ risk factors for a Fontan have largely been overcome.1 Such is not the case with AV valve function. Many clinical series have shown significantly worse survival in patients with single-ventricle physiology who had significant AV valve insufficiency.2-5 In an effort to overcome the risk of insufficiency, various repair techniques have evolved.2,6,7 Despite some success, AV valve insufficiency is still a strong risk factor of failure of cavopulmonary circulation in the current era.6,8 In this review, we discuss the etiology and mechanism of development of significant AV valve insufficiency in patients with single-ventricle physiology, surgical indication and repair techniques, and clinical outcomes along with our 10-year surgical experience of this challenging entity.
From The Labatt Family Heart Centre, The Hospital for Sick Children and The University of Toronto, Canada. Address correspondence to Glen S. Van Arsdell, MD, Division of Cardiovascular Surgery, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada, M5G 1X8; E-mail: [email protected]
1092-9126/11/$-see front matter © 2011 Published by Elsevier Inc. doi:10.1053/j.pcsu.2011.02.001
Development of AV Valve Insufficiency Mechanisms of development of AV valve insufficiency in the single-ventricle physiology are complex and multifactorial. The three key factors that trigger the development of significant AV valve insufficiency are chronic volume overload, structural AV valve abnormalities, and myocardial damage/ischemia (Fig. 1). Chronic Volume Overload Many patients with a single-ventricle physiology who undergo a neonatal palliation with a systemic-to-pulmonary shunt (Blalock-Taussig shunt or Norwood type procedure) will result in a shunt-dependent in-parallel circulation. The systemic single ventricle is exposed to considerable volume overload until the time of stage II palliation, where cavopulmonary shunt type operation makes circulation in-series, minimizing volume overload.9 Chronic volume overload causes progressive ventricular dilatation,10 annular dilation, and an effective leaflet tethering, leading to malcoaptation of the leaflets. Structural Abnormalities of AV Valve AV valve leaflets and the subvalvular apparatus in a functional single-ventricle heart are often abnormal. Stamm et al11 examined 82 specimens with hypoplastic left heart syndrome (HLHS) in a view of morphologic tricuspid valve as a systemic AV valve. One third of the specimens had moderate or severe tricuspid valvular dysplasia, which was particularly 75
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Figure 1 The mechanisms of development of significant AV valve insufficiency. We emphasize the importance of structural AV valve abnormalities as one of the most imperative triggers in the development of AV valve insufficiency in this patient group.
common in the presence of a patent mitral valve. Other abnormalities included bileaflet or, rarely, quadraleaflet tricuspid valve (12%), accessory orifices, prolapse of the anterior leaflet, and, rarely, Ebstein’s malformation. Others have described that up to 20% of the autopsy specimens of functional single left ventricles (ie, tricuspid atresia and pulmonary atresia with intact ventricular septum) had structural abnormalities in their morphologically mitral valve.12,13 The common AV valve leaflets in the setting of double inlet AV connection are dysplastic in 55% of cases.14 What the autopsy series clearly shows is that not all AV valve insufficiency in singleventricle physiology is ‘functional’ in nature. Tricuspid Valve Because it is designed to sustain the competency in the lowresistance pulmonary circulation, the tricuspid valve is thought to be more susceptible to pressure or volume overload. In patients who had more than moderate pulmonary hypertension (pulmonary artery pressure, 50 to 69 mmHg) in the setting of a biventricular physiology, approximately Table 1 Classification and Prevalence of Mitral Valve Anomalies According to the Carpentier’s Functional Classification (n ⴝ 145) Type
Percentage
Type I: Normal leaflet motion 1. Annular dilatation 2. Cleft 3. Leaflet defect Type II: Leaflet prolapse 1. Chordal elongation 2. Papillary muscle elongation 3. Absence of chordae Type III Restricted leaflet motion A. Normal papillary muscle 1. Commissure papillary muscle fusion 2. Short chordae B. Abnormal papillary muscle 1. Parachute valve 2. Hammock valve 3. Papillary muscle hypoplasia
21.0 4.8 12.0 4.1 54.5 31.7 16.5 6.2 24.1
Modified and adapted from Chauvaud et al.20
5.5 4.8 3.4 8.2 2.0
one third of patient had more than moderate tricuspid valve insufficiency, with half having competent or mildly insufficient tricuspid valves.15 Likewise, chronic volume overload does not always result in significant tricuspid valve insufficiency. Among 30 adult patients with unrepaired atrial septal defect with a mean pulmonary-to-systemic flow ratio of 2.4:1, one fifth developed more than moderate tricuspid valve insufficiency at 25 years.16 There is no question that significant pressure and/or volume overload play a role in developing tricuspid valve insufficiency. However, the mechanism of significant tricuspid valve insufficiency is more complex and should be the combination of pressure and/or volume overload with other factors (ie, ventricular and annular dilatation, ventricular septal geometry, ventricular function, and structural abnormalities of the valve leaflets). Myocardial Damage/Ischemia and Ventricular Dysfunction Ventricular dysfunction leads to progressive ventricular dilatation and changes in geometry of the ventricle and subvalvular apparatus, including papillary muscle. The mechanism for dysfunction has been described to include circulatory arrest, ischemia-reperfusion injury, hemodilution, inflammatory response, high post-bypass systemic vascular resistance, and intrinsic vulnerability of neonatal systemic right ventricle.17 Our recent experience showed approximately one third of the infants with Norwood physiology had at least mild AV valve insufficiency at pre-stage II evaluation.18 Kuroda et al10 showed decrease in ejection fraction of the sysTable 2 Type of AV Valve Abnormalities in 58 Patients Who Underwent AV Valve Repair in The Hospital for Sick Children (1998-2008) Abnormalities
Percentage
Annular dilatation Cleft Prolapse Chordal elongation Restriction Dysplasia Papillary muscle abnormalities
77 21 51 42 49 52 8
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temic ventricle after placement of a systemic-to-pulmonary shunt. In addition, a diastolic run off through the systemicto-pulmonary shunt may reduce effective coronary artery blood flow, thereby potentially leading to ventricular dysfunction. Once significant AV valve insufficiency occurs, it creates a negative feedback loop where further volume overload of the regurgitant volume worsens ventricular and annular dilatation (Fig. 1).
Pathophysiology of AV Valve Insufficiency The types of AV valve abnormalities and their frequency described by Carpentier and colleagues19,20 are listed in Table 1. The primary mechanisms of AV valve insufficiency in 58 patients who underwent AV valve repair from 1998 to 2008 at The Hospital for Sick Children (Toronto, Canada) are shown in Table 2. The vast majority of patients had annular dilatation. Prolapse, restriction, and dysplasia were seen in approximately half the patients, indicating that most patients had more than one AV valve abnormality. In fact, all 58 patients in our series had at least two types of abnormality. Of interest, the most common mechanism of AV valve insufficiency was prolapse, accounting for 46% of the patient population. Of note, AV valve insufficiency in the single-ventricle patient is often associated with dysplasia of the leaflets. Restriction was seen in approximately half the patients, but was rarely the primary mechanism of AV valve insufficiency (2%). The Myth of Volume Unloading With Stage II Palliation Stage II palliation with a cavopulmonary connection is thought to volume unload the single ventricle. While changes in ventricular volume and annular dimension can be documented,21 those changes did not necessarily result in improvement in AV valve insufficiency.22,23 Mahle et al22 showed that only six (16%) out of 36 patients who had moderate or severe AV valve insufficiency at the time of bidirectional cavopulmonary shunt (BCPS) had improved AV valve insufficiency grade without AV valve repair. Ten (28%) patients subsequently required AV valve repair, indicating that the majority of AV valve insufficiency is not purely ‘functional’. Our recent series showed the vast majority (85%) of the patients who required AV valve repair had structural abnor-
Table 3 Primary Mechanisms of AV Valve Insufficiency in 58 Patients With Single-Ventricle Physiology* Right Left Ventricle Ventricle Number Mechanism (n ⴝ 48; 83%) (n ⴝ 8; 13%) (%) Annular dilatation Prolapse Dysplasia Cleft Restriction
8
0
8 (15)
22 12 1 1
2 6 0 0
24 (46) 17 (35) 1 (2) 1 (2)
*Two patients who had indeterminate ventricular morphology had dysplasia as the primary mechanism of AV valve insufficiency.
Figure 2 The timing of AV valve repair in 58 patients with singleventricle physiology who underwent AV valve repair during staged palliation.
malities of the AV valve (Table 2).24 In other words, only 15% of the AV valve insufficiency had pure annular dilatation as the primary mechanism (Table 3). Additionally, newly emerging volumetric data from magnetic resonance imaging shows that collateral formation leads to a Qp:Qs of 1 following a BCPS.25 These magnetic resonance imaging findings suggest that the volume unloading of a BCPS appears to be temporary. Our policy has been to inspect and attempt repair for AV valve insufficiency of mild to moderate or greater at the time of the cavopulmonary connection. That policy will continue, given that an anatomic abnormality is identified in 85% of cases. When Should We Repair the AV Valve? The timing of AV valve repair in our institute is shown in Fig. 2. Approximately two thirds of patients underwent AV valve repair at stage II palliation, and just less than one fifth of the patients underwent AV valve repair either between the BCPS and Fontan or at the Fontan procedure. In general, we try to avoid repair at the time of a Fontan procedure unless it is a simple repair requiring limited operative time. It is rare to intervene on the AV valve at stage I palliation or in the neonatal time frame. First of all, it is rare to have significant AV valve insufficiency in neonates at presentation, and secondly, neonates with complex single-ventricle anatomy with significant AV valve insufficiency may be triaged to the primary transplantation pathway.
Surgical Techniques Evaluation of the AV Valve Direct inspection of the valve and apparatus and inspection with a balanced fluid insufflation test is performed. Special attention is given to each AV valve component: annular di-
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78 Table 4 The Repair Techniques Used in 58 Single-Ventricle Patients Who Underwent AV Valve Repair Operative Techniques Annuloplasty Commissuroplasty* Valvuloplasty Chordal repair Cleft closure Edge-to-edge repair* Papillary muscle repair
Number (%) 46 (85) 29 (54) 12 (22) 2 (4) 18 (33) 17 (29) 1 (2)
*We used to call the technique that is now called “edge-to-edge repair” as “commissuroplasty or artial closure of commissure.” Therefore, there are some overlaps between these two categories.
mension, commissural leak, prolapse or restriction of the leaflets, leaflet abnormalities (ie, cleft, dysmorphism or dysplasia), subvalvular abnormalities (ie, chordal fusion or elongation), and papillary muscle abnormalities. The repair techniques we used in 58 single-ventricle patients who underwent AV valve repair are shown in Table 4. Annular Dilatation Partial annuloplasty and commissuroplasty are the commonly used techniques for a generalized central regurgitation because of annular dilatation and subsequent poor coaptation and/or localized prolapse of the leaflet(s). We typically use 5-0 polypropylene or 4-0 polyester sutures to locally reduce the annulus size along the commissure(s), where the regurgitant jet mainly comes from. This maneuver is essentially a functional commissuroplasty on the corresponding commissure. Anatomic commissuroplasty is achieved with 6-0 or 7-0 polypropylene simple interrupted sutures. Bove and colleagues6,26 suggested a rather extensive partial annuloplasty to repair the tricuspid valve in HLHS hearts (Fig. 3). Running parallel mattress sutures are placed along the annulus supporting the inferior leaflet between its zones of apposition with the anterior and septal leaflets (Fig. 3A), obliter-
ating the inferior leaflet (Fig. 3B). This repair essentially forms a bicuspid valve. A semi-circular or circular annuloplasty has been described. Kanter et al27 reported the De Vega type semi-circular annuloplasty for functional tricuspid valve insufficiency associated with various congenital heart diseases. Imai et al2 described a circular annuloplasty for various types of AV valve morphology. A 2-0 or 3-0 polytetrafluoroethylene suture is passed through the annulus circumferentially (Fig. 4A), and the full circular purse-string suture is tied over a 22 or 24 mm Hegar’s dilator (Fig. 4B). The suture was placed on the leaflet itself at the area of conduction system. Our preference is to use the partial localized annuloplasty, rather than the circular annuloplasty, to effectively reduce the annulus size in the area of regurgitation ,and also to leave the growth potential to the AV valve annulus.28 Insertion of an annuloplasty ring is also an option for older children and adolescents who have a nearly adult-size AV valve annulus. Prolapse Prolapse is the most common pathophysiology of congenital mitral valve insufficiency,20 as well as the AV valve insufficiency in single-ventricle physiology24 (Tables 1 and 2). A localized or generalized prolapse with essentially normal chordae and subvalvular apparatus are most commonly treated with annuloplasty and/or commissuroplasty.26 If elongation of the chordae and/or papillary muscle is the mechanism of prolapse, chordal shortening plasty can be applied (as described by Carpentier et al19). For chordal rupture or local deficiency, the chordae could be transposed from the opposite leaflet,19 although this technique is not always feasible in the morphologically tricuspid valve or common AV valve. Alternatively, chordal replacement with polytetrafluoroethylene sutures has been shown to be a durable option.29 This technique has been used in morphologically mitral and tricuspid valves.30,31 We and others have used edge-to-edge leaflet repair as a means of managing single-leaflet prolapse. The technique was originally described by Alfieri and colleagues32,33 as a
Figure 3 The extensive partial annuloplasty obliterating the inferior leaflet. This technique essentially forms a bileaflet valve. (Modified and adapted from the original description by Ohye et al.6)
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Figure 4 The circular annuloplasty technique for the common AV valve. A, A large polytetrafluoroethylene suture is passed through the annulus circumferentially. B, The suture is tied over a 22 or 24 mn Hagar’s dilator. (Modified and adapted from the original description by Imai et al.2)
technique to repair mitral valve prolapse in adults, and has subsequently been applied to tricuspid valves and AV valves. Ando and Takahashi7 delineated the edge-to-edge strategy in 22 single-ventricle patients (Fig. 5). For the common AV valve, the superior and inferior bridging leaflets are sutured together, along with cleft closure and/or additional closure of the commissure(s), between the non-coapting leaflets (Figs. 5A and B). In the tricuspid valve, the free edges of the anterior and septal leaflets are sutured together, making two effective orifices (Fig. 5C). Alternatively, the commissure between the anterior and septal commissure could be completely obliterated if the effective orifice size is large enough (Fig. 5D). Alfieri et al34 further extended this concept and reported a ‘clover technique’ to repair traumatic tricuspid insufficiency, where the free edges of all three leaflets are sutured together (Fig. 6). Double orifice techniques have been reported in the various configurations, especially for repairing common AV valve. Our surgical strategy is to first apply annuloplasty and commissuroplasty at the zone of appositions of the affected leaflets. Shortening of the chordae and/or papillary muscle was occasionally used for repairing chordal elongation in our series (6%), but chordal transposition or artificial chordal replacement was barely used for repairing AV valve insufficiency in the single-ventricle physiology in our institute. The edge-to-edge type repair is one of our preferences of choice, especially for common AV valve morphology with free-floating leaflets with the absence of supporting subvalvular apparatus. Leaflet Abnormalities A cleft is a relatively common leaflet abnormality (21%; Table 2) in single-ventricle patients, typically with a common AV valve; but it also can be seen in the anterior leaflet of the tricuspid valve. Standard cleft closure is utilized (Fig. 7A). If there is a large cleft associated with deficient
leaflet tissue, a pericardial patch can be used to augment the leaflet.20 In the moderate to severely dysplastic AV valves, we often see multiple small gaps, irregular leaflet edge, and resultant minor prolapses along the edge of the leaflets (Fig. 7B). The dyslplastic leaflet linearity can be improved by individual closure of each gap with 7-0 prolene interrupted sutures. Also, we often see relatively large accessory ‘pseudo’ commissures on the leaflets more appropriately termed “leaflet dysmorphism” (Fig. 7C). The dysmorphic ‘commisures’ can have localize prolapse that is repaired with an edge-to-edge technique. Restriction Significant AV valve insufficiency purely caused by anatomic restriction of the leaflets is extremely rare (2%) in single-ventricle patients. Functional restriction was quite common and seen in 49% of our cohort. Functional restriction occurs when there is annular dilatation and secondary displacement of the papillary muscle, making a ‘tethering effect,’ which can be resloved by downsizing the annulus. If restrictive motion is caused by the structural abnormalities of the subvalvular apparatus, mobilization of chordae and papillary muscle can be performed according to Carpentier.19 One could apply the leaflet extension technique for a severely restricted leaflet.20 No patient required such techniques in our series. AV Valve Replacement Replacement of the AV valve is the last option after all the reconstructive or reparative approaches fail. In fact, there was no patient who had primary AV valve replacement in our series. A mechanical valve is the device of choice at our institute because of its long durability, but other institute prefers to use a biosynthetic valve.35 It is ideal to preserve the papillary muscle(s) and chordal attachment to restore ventricular function after AV valve replacement,35 although it is not al-
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Figure 5 Two common types of the edge-to-edge repair for repairing the morphologically common AV valve (A, B) and the tricuspid valve (C, D). A, The superior and inferior bridging leaflets are sutured together and the cleft is directly closed. B, A non-coapting commissure is entirely closed in addition to the edge-to-edge suture on the superior and inferior bridging leaflets. C, The anterior and septal leaflets are sutured together making two effective orifices. D, A con-coapting antero-septal commissure is totally obliterated in addition to the edge-to-edge suture. (Modified and adapted from the original description from Ando and Takahashi.7)
ways possible in the complex AV valve morphology. The incidence of heart block caused by prosthetic valve replacement in small children is substantially high.35,36 Post-Repair Evaluation Intraoperative assessment of AV valve repair by a transesophageal echocardiography (TEE) is of prime importance for the decision making process. If the regurgitation has not improved or is not less than mild, we will revise the repair if the surgeon’s assessment is that there is room for further im-
provement. Evaluation of ventricular function at this point is of great importance because our recent studies clearly showed that the postoperative ventricular function is the strongest indicator for survival.24 Less than moderate residual AV valve insufficiency on TEE is accepted. Our intent is to revise the repair for moderate or greater residual insufficiency. Attention should be given to interpret the regurgitation degree on the intraoperative TEE immediately after weaning from cardiopulmonary bypass. There is often some
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Figure 6 The clover technique described by Alfieri et al for repairing traumatic tricuspid valve insufficiency. The edges of all three leaflets are sutured together making three effective orifices. (Modified and adapted from the original description from Alfieri et al.34)
discrepancy in the regurgitation grade between the intraoperative TEE and postoperative transthoracic echocardiographic finding, where TEE often underestimates the subsequent regurgitation grade.37 We tend to accept mildto-moderate postoperative AV valve stenosis (mean pressure gradient, ⬍ 3-4 mmHg).
Clinical Outcomes Survival The natural and surgically modified survivals of the singleventricle patient with significant AV valve insufficiency have been consistently poorer than that in the single-ventricle patient with a competent AV valve. Barber et al,4 who reported survival of patients with HLHS undergoing Norwood proce-
dure between 1984 and 1987, showed a significantly worse survival in patients with significant tricuspid valve insufficiency (survival: 55% vs 35% at 1 year after Norwood procedure). Because no intervention was performed on the tricuspid valve in this population, this study provides a nice ‘natural history’ evaluation of the effect of AV valve insufficiency on survival. Imai et al2 showed a significantly worse survival in single-ventricle patients who required AV valve repair compared with patients with standard risks (5-year survival, 95% vs 84%). This series was conducted in the era of two-staged Fontan completion. Recent clinical series of AV valve repair at the time of Fontan had a reasonable hospital survival (100% operative survival).38 Ohye et al6 reported the largest series of 28 patients with HLHS who underwent tricuspid valve repair after Norwood
Figure 7 Our surgical strategies to repair dysplastic or dysmorphic tricuspid valve in HLHS hearts. A, Direct cleft closure along with annuloplasty (functional commissuroplasty) on the antero-inferior commissure. B, Repair of the irregular dysplastic leaflets. C, Repair of dysmorphic leaflets by means of the edge-to-edge type repair.
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Figure 8 A, The Kaplan-Meier survival curve of the single-ventricle patients who underwent AV valve repair compared with the matched control subjects (n ⫽ 50 in each group), showing the worse survival in the AV valve repair group compared with the standard-risk group. B, The subgroup who has successful AV valve repair with preserved ventricular function (n ⫽ 35) has an equivalent survival compared with the matched controls.
procedure, which essentially suggested that postoperative right ventricular function and residual tricuspid valve insufficiency are the major determinants for survival. The patients who had successful tricuspid valve repair (residual insufficiency, grade 0 to 2) with preserved right ventricular function had the best survival (survival rate without transplant, 88%). On the other hand, there was 80% mortality in patients with early or late right ventricular dysfunction regardless of the result of tricuspid valve repair. Our recent series, consisting of 58 patients with various types of single-ventricle physiology, had similar findings to the Ohye study. The patients who required AV valve repair have a worse survival compared with the matched control patients (Fig. 8A). Of importance, the subgroup who had a successful AV valve repair with preserved ventricular function had an equivalent early and long-term survival compared with matched controls (Fig. 8B). The predictors for death or transplant are listed on Table 5, suggesting the importance of ventricular function and residual AV valve sufficiency on the outcome.
Durability of AV Valve Repair Ohye et al6 reported that 15 out of 21 patients (71%) with HLHS who had a successful tricuspid valve repair continued to have none to mild tricuspid valve insufficiency at the median follow-up of 20 months. Ando and Takahashi7 showed that the regurgitation grade was mild or less in 77.3% in the edge-to-edge repair group compared with 38.7% in the conventional repair group at the mean follow-up period of 2 to 2.5 years. In our series, 10 of 58 patients (17%) required re-repair or replacement at the median follow-up period of 21 months.24 The AV valve morphology or mechanism of initial AV valve insufficiency did not influence the re-intervention rate. The mechanisms of recurrent AV valve insufficiency are listed in Table 6. All four patients who had dysplasia as the primary mechanism of recurrent AV valve insufficiency required replacement of the AV valve. The survival after re-repair or replacement was 70% at 1 and 3 years, and there was no difference between re-repair and replacement groups.
Summary Table 5 Predictors for Death/Transplant After AV Valve Repair Based on Cox Regression Model in 58 Patients Who Underwent AV Valve Repair
Significant AV valve insufficiency in the single-ventricle physiology has substantial negative impacts on the natural
Predictors
P Value
Cardiopulmonary bypass time Annular dilatation as the primary mechanism* Residual AV valve insufficiency grade Post-repair ventricular function
.02 .02 .03 .02
Table 6 The Mechanism of Recurrent AV Valve Insufficiency Requiring Re-Repair or Replacement
*Seventy-five percent of the patients who had annular dilatation as the primary mechanism had preoperative ventricular dysfunction and dilatation.
Mechanism
Number
Re-annular dilatation Dysplasia Cleft Double orifice
3 4 2 1
AV Repair in patients with single-ventricle physiology and surgical modified histories of this patient population. The combination of chronic volume overload, structural abnormalities of the AV valve, and myocardial damage/ventricular dysfunction trigger the development of AV valve insufficiency. Our recent clinical study and other pathological studies emphasize the importance of structural abnormalities of the AV valve on development of AV valve insufficiency and on clinical outcomes of AV valve repair. The fact that the vast majority of patients (85%) with significant AV valve insufficiency have structural abnormalities on the AV valve, which indicates that volume unloading surgery alone may not be enough to effectively reduce the degree of AV valve insufficiency. Post-repair survival is greatly influenced by post-repair ventricular function and residual AV valve insufficiency. Patients who have successful AV valve repair with preserved ventricular function have an equivalent early and long-term survival compared with standard-risk patients.
Proposed Strategy and Future Direction The lessons we learned from our recent clinical series and literature review are that it is of prime importance to appreciate the high incidence and clinical effect of the structural abnormalities of AV valve. Valve repair at stage II palliation may minimize the period of volume overload, thereby potentially preserving post-repair ventricular function. Inspection of AV valve structure and function is strongly recommended if a patient has mild-to-moderate or moderate AV valve insufficiency at the time of stage II palliation. We believe the strategy is justified based on an 85% incidence of valve structural abnormalities that are not likely to be successfully treated with volume unloading surgery alone.
Acknowledgment The authors would like to thank Nobuko Yamamoto for the illustrations.
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