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Ann Thorac Surg 2008;85:2085-2088. doi:10.1016/j.athoracsur.2008.01.047
© 2008 The Society of Thoracic Surgeons
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Original Articles: Pediatric Cardiac

Surgical Repair of the Mitral Valve in Children With Dilated Cardiomyopathy and Mitral Regurgitation

Mark A. Walsh, MDa,*, Lee N. Benson, MD, FRCPCa, Anne I. Dipchand, MDa, Andrew N. Redington, MDa, Christopher A. Caldarone, FRCSCb, Glen S. Van Arsdell, MD, FRCSCb, Paul F. Kantor, MBBCha

a Division of Cardiology, Labatt Family Heart Centre, The Hospital for Sick Children, Toronto, Ontario, Canada
b Division of Cardiovascular Surgery, The Hospital for Sick Children, Toronto, Ontario, Canada

Accepted for publication January 15, 2008.

* Address correspondence to Dr Walsh, Labatt Family Heart Centre, The Hospital for Sick Children, 555 University Ave, Toronto, Ontario, M5G 1X8, Canada (Email: mark.walsh{at}sickkids.ca).


   Abstract
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 Abstract
Introduction
 Material and Methods
 Results
 Comment
 References
 
Background: Significant mitral regurgitation is known to exacerbate left ventricular dysfunction in dilated cardiomyopathy. Although intervention on the regurgitant mitral valve is frequently described in adults, there is little pediatric data.

Methods: Five children (aged 3 months to 4 years) with dilated cardiomyopathy and mitral regurgitation underwent mitral valve repair between January 1999 and January 2007 at our institution. All had mitral regurgitation graded as moderate to severe, with ejection fractions of 35% to 60% (median 53%).

Results: There were no deaths; all children were weaned from cardiopulmonary bypass; 1 child required cardiac transplantation 3 weeks after repair. After surgery, mitral regurgitation was moderate in 1 patient, mild in 2 patients, and trivial in 2 patients. The 4 successful cases showed an improvement in functional status at latest follow-up (range, 8 years to 4 months): all were asymptomatic (4 children had preoperative symptoms). Successful cases showed a decreased left atrial dimension (mean z-score 3.8 to 2.6) and a decreased left ventricular end-diastolic diameter (mean 6.9 ± 1.6 to 5.4 ± 1.2). Ejection fraction and left ventricular end-systolic index did not show an improvement and declined in some cases.

Conclusions: We conclude that repair of the mitral valve is feasible in children with dilated cardiomyopathy and acquired mitral regurgitation. Most of the children demonstrated decreased left ventricular chamber sizes and an improved functional status. Although this operation improves symptoms, it is not clear whether it postpones or abrogates the need for cardiac transplantation.


   Introduction
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 Abstract
 Introduction
Material and Methods
 Results
 Comment
 References
 
Childhood dilated cardiomyopathy (DCM) has a prevalence of approximately 0.5 per 100,000, with 50% of cases diagnosed in children under 1 year of age [1–3]. A recent series encompassing of all types of pediatric cardiomyopathy estimated the 1- and 5-year incidence of either death or cardiac transplantation to be 31% and 46%, respectively. When considering all subtypes, DCM has the highest incidence of cardiac transplantation [4]. Medical management from the outset is predominantly palliative and has met with limited success in reversing the underlying disease process [5].

The onset of significant mitral regurgitation (MR) is associated with decreased survival in adult series [6]. Interventions to decrease MR may reduce left atrial pressure, left ventricular (LV) volume load, improve symptoms, and promote favorable LV reverse remodeling. Accordingly, there is growing enthusiasm for surgical and catheter-based interventions on the mitral valve in adult patients [7–11]. Despite some reported success in adults, the premise does not necessarily apply to children with nonischemic DCM. Given the difficulties in comparing adult and pediatric data, it is unclear to what extent one can extrapolate from the adult experience. Mitral valve repair in children may function well as a palliative procedure, both relieving symptoms and slowing disease progression [12]. We describe the clinical course of 5 children with DCM who underwent repair of the mitral valve.


   Material and Methods
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 Introduction
 Material and Methods
Results
 Comment
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Between January 1999 and January 2007, 5 children with DCM and MR underwent mitral valve repair. This study was a retrospective review of these cases, approved by the Research Ethics Board at The Hospital for Sick Children. Informed consent for surgery was obtained in all cases outlining the risks and benefits of the operation. Clinical case notes and echocardiograms were all reviewed retrospectively. The MR in all cases was subjectively graded on a scale of trivial to severe by the reporting cardiologist, based on the width of the color Doppler jet in the left atrium.

Surgical Technique
Cardiopulmonary bypass was established with mild hypothermia (32°C to 34°C) by standard aortic and bicaval venous cannulation. Myocardial protection was accomplished with antegrade cold blood cardioplegia with prompt diastolic arrest followed by repeated infusion 20 minutes thereafter. Intraoperative transesophageal echocardiography was used to guide the surgeon as to the appropriate intervention. The left atrium was incised parallel to the interatrial groove, and the mitral valve exposed. Patients 2 and 3 had a Cosgrove-Edwards ring (28 mm and 26 mm) inserted whereas all others had an annuloplasty using autologous pericardium. The Cosgrove-Edwards rings were cut to suit the annulus size and sutured in place. Patient 3 required the ring to be shortened by 8 mm to better approximate the size of the anterior leaflet. Patient 4 had an additional Gore-Tex (W.L. Gore & Assoc, Flagstaff, Arizona) chordae sutured to the anterior mitral leaflet because of a prolapsed papillary muscle. Patient 5 had closure of a cleftlike false commissure in the middle of the posterior mitral leaflet using interrupted sutures. Evaluation of the repair was performed with intraoperative transesophageal echocardiography. Once the repair was judged to be adequate, children were weaned from cardiopulmonary bypass.


   Results
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 Abstract
 Introduction
 Material and Methods
 Results
Comment
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Four girls and 1 boy, 3 months to 4 years of age, underwent repair of the mitral valve. All had a diagnosis of idiopathic DCM with moderate to severe MR. All children had associated radiographic signs of pulmonary venous congestion. Four children had mild symptoms of respiratory distress; 1 child was asymptomatic. Echocardiographic and clinical assessments are detailed in Table 1. Patients 1 and 5 were siblings, and patient 1 had suspected Alström's syndrome (visual impairment and mild developmental delay). At the time of the surgery, all children were taking an angiotensin-converting enzyme inhibitor, 1 child was taking digoxin, and 3 were on a β-blocker (1 patient propranolol; 2 patients, carvedilol). Before repair, 1 child required inotropic support; however, no children required positive pressure ventilation.


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  		Table 1 Patient Demographics, Echocardiogram Data, New York Heart Association (NYHA) Class at Presentation and Latest Follow-Up
 
There were no intraoperative or postoperative deaths; all children were successfully weaned from cardiopulmonary bypass. Milrinone infusion (0.66 µg · kg–1 · min–1) and low-dose dopamine infusion (5 µg · kg–1 · min–1 [4 children]) were commenced once weaned from cardiopulmonary bypass as per our institution's protocol. Two children required a high-dose epinephrine infusion (0.1 µg · kg–1 · min–1) for globally decreased left ventricular function once weaned from cardiopulmonary bypass. Children remained intubated for 1 to 4 days; critical care length of stay ranged from 3 to 7 days. There were no other significant complications in the immediate postoperative period.

Patient 4 continued to demonstrate severe global left ventricular dysfunction until 3 weeks after repair; the ejection fraction was 10% compared with 30% preoperatively. A milrinone infusion was commenced; however, intubation was required for increasing respiratory distress which was followed by a cardiac arrest. The child was emergently placed on extracorporeal mechanical support and underwent cardiac transplantation 4 days later.

Echocardiographic Data
Left ventricular ejection faction, left atrial z-score, end-diastolic dimension z-score, end-systolic volume, and end-diastolic volume indexed to body surface area are listed in Figure 1. There was a decreased mean left atrial dimension (z-score 3.8 to 2.6) and a decreased mean left ventricular end-diastolic diameter (mean 6.9 ± 1.6 to 5.4 ± 1.2) from presentation to latest follow-up. The ejection fraction and end-systolic volume showed a variable decline in all but 1 case. Patients 1 and 2 have a longer follow-up of 6 years; they showed a decline in ejection fraction of 35% to 27% and 53% to 40% over this period.


Figure 1
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  		Fig 1. Change in echocardiographic variables with respect to time. The follow-up times for patients 1 and 2 are 6 years; the rest have a follow-up of less than 6 months. (A) Left ventricular end-systolic volume. (B) Ejection fraction. (C) Left atrial z-score. (D) Left ventricular end-diastolic dimension. (E) Left ventricular end-diastolic volume index. The timeline in all graphs is as follows: 1 = presentation; 2 = 1 week preoperative; 3 = 1 week postoperative; 4 = 6 months postoperative; 5 = latest follow-up. (Diamonds = patient 1; solid boxes = patient 2; solid triangles = patient 3; open boxes = patient 4; open circles = patient 5.)

 
All children had the initial echocardiogram performed between 2 and 16 months of age; MR was severe in 2, moderate in 1, and mild to moderate in 2 children. At presentation, 1 child had normal ventricular function, 2 had mildly reduced ventricular function, and 2 had moderately reduced ventricular function. One week before surgery MR was moderate in 1, moderate to severe in 3, and severe in 1 child. After repair, MR was moderate in 1, mild in 2, and less than mild in 2 children. At latest follow-up (range, 3 months to 6 years), MR was mild in 2 children and mild to moderate in 2. Patient 4, who had residual moderate MR after surgery, eventually underwent cardiac transplantation.

Outcomes
All children are alive, with 1 patient having undergone cardiac transplantation. The time from surgery to latest follow-up is less than 6 months for 3 children, and 6 years for the other 2. At latest follow-up, all 4 successful cases were asymptomatic and growing along their appropriate percentiles. Of the 4 children who had a successful repair, all are receiving diuretics and an angiotensin-converting enzyme inhibitor; 3 are on β-blockers.


   Comment
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
References
 
There are many descriptive studies of mitral valve repair in adult cohorts with both ischemic and nonischemic DCM, with much controversy as to the effectiveness of the operation [12]. From a pediatric perspective, their interpretation is complicated by a different spectrum of etiologies, a different life expectancy, concomitant coronary artery disease, and other comorbidities. In addition, mitral valve repair in the adult population is often performed as an adjunct to ventricular reconstruction, coronary artery revascularization, and additional valvuloplasties [8, 13].

Data from our own institution on a cohort of 189 with pediatric DCM over a 30-year period has shown a transplant-free 5-year survival of 60%. Risk factors for death and transplantation were a decreased ejection fraction at presentation and older age at presentation [14]. Romano and Bolling [12] published data on 200 adult patients undergoing repair of the mitral valve for DCM from 1994 to 2003. The cohort consisted of both ischemic and nonischemic DCM, with some patients having additional interventions at the time of repair. They reported 1 perioperative death, 8 by 30 days, and 26 late deaths. Their actuarial survival was 82%, 71%, and 52% at 1, 2, and 5 years, respectively. As all patients were in New York Heart Association (NYHA) class III and IV, it is unclear whether these patients actually lived longer as a result of the mitral valve repair. Nevertheless, there was a significant improvement in symptoms: the mean NYHA class went from 3.2 to 1.8. There were improvements also in ejection fraction, cardiac output, and end-diastolic volume. The authors suggested that this was a feasible operation with acceptable mortality and that the long-term results approached transplantation survival [12].

Children with congenital MR without DCM appear to retain LV systolic function to a degree disproportionate to the severity of their valvar insufficiency. In children with DCM, significant MR is more likely to affect ventricular function. Worsening left ventricular function begets more annular dilation resulting in more MR, which further exacerbates LV dysfunction [15, 16]. A therapeutic "time window" may exist during which surgical intervention might forestall this progression. In children with DCM, this therapeutic window may be present very early in the disease, when there is relatively preserved ventricular function.

In 1 patient (patient 4), there was a further decline in left ventricular function after MV repair; she eventually underwent cardiac transplantation. This patient was repaired 4 years after presentation; one might speculate that an earlier repair, before decompensation occurred, might have been more effective.

Of the 2 children with longer follow-up, the one has not shown any change in LV ejection fraction and the other has shown a small decrease. This decline in ejection fraction may reflect progression of the underlying cardiomyopathy despite improved LV geometry and volume loading. For these children, it is impossible to determine the degree to which symptom-free survival is attributable to disease severity, versus the benefit accrued from mitral valve repair.

In our experience, repair of the mitral valve resulted in marginally lower ventricular diastolic volumes and a more convincing decrease in left atrial dimension in 4 of 5 cases. Importantly, there was a symptomatic improvement in 4 cases, up to 6 years after repair. We believe that consideration should be given to mitral valve repair in children with moderately reduced LV function, moderate mitral insufficiency, and symptoms consistent with left atrial pressure elevation. In select cases, the benefit of improved functional status and the possibility of postponing cardiac transplantation outweigh the risk of undergoing mitral valve repair. The patients most likely to benefit are those with moderate-to-severe symptoms of pulmonary venous congestion.

Limitations of this study include both the small numbers and the short follow-up. In addition, the wide spectrum of disease severity in pediatric DCM make it difficult to assess the true impact of mitral valve surgery. Our results show, however, that this operation warrants consideration in symptomatic children with DCM who have significant MR in association with decreased LV function.


   References
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 Abstract
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 Material and Methods
 Results
 Comment
 References
 

  1. Arola A, Jokinen E, Ruuskanen O, et al. Epidemiology of idiopathic cardiomyopathies in children and adolescents. A nationwide study in Finland. Am J Epidemiol 1997;146:385-393.[Abstract/Free Full Text]
  2. Nugent AW, Daubeney PE, Chondros P, et al. The epidemiology of childhood cardiomyopathy in Australia N Engl J Med 2003;348:1639-1646.[Abstract/Free Full Text]
  3. Lipshultz SE, Sleeper LA, Towbin JA, et al. The incidence of pediatric cardiomyopathy in two regions of the United States N Engl J Med 2003;348:1647-1655.[Abstract/Free Full Text]
  4. Towbin JA, Lowe AM, Colan SD, et al. Incidence, causes, and outcomes of dilated cardiomyopathy in children JAMA 2006;296:1867-1876.[Abstract/Free Full Text]
  5. Canter CE, Kantor PF. Transplantation for dilated cardiomyopathy Prog Ped Cardiol 2007;23:67-72.
  6. Yoran C, Yellin EL, Becker RM, Gabbay S, Frater RW, Sonnenblick EH. Dynamic aspects of acute mitral regurgitation: effects of ventricular volume, pressure and contractility on the effective regurgitant orifice area Circulation 1979;60:170-176.[Abstract/Free Full Text]
  7. Maisano F, Caldarola A, Blasio A, De Bonis M, La Canna G, Alfieri O. Midterm results of edge-to-edge mitral valve repair without annuloplasty J Thorac Cardiovasc Surg 2003;126:1987-1997.[Abstract/Free Full Text]
  8. Wilhelm MJ, Hammel D, Schmid C, et al. Partial left ventriculectomy and mitral valve repair: favorable short-term results in carefully selected patients with advanced heart failure due to dilated cardiomyopathy J Heart Lung Transplant 2005;24:1957-1964.[Medline]
  9. Mudge Jr GH. Asymptomatic mitral regurgitation: when to operate? J Card Surg 1994;9(Suppl):248-251.[Medline]
  10. Fann JI, St Goar FG, Komtebedde J, et al. Beating heart catheter-based edge-to-edge mitral valve procedure in a porcine model: efficacy and healing response Circulation 2004;110:988-993.[Abstract/Free Full Text]
  11. Duffy SJ, Federman J, Farrington C, Reuter DG, Richardson M, Kaye DM. Feasibility and short-term efficacy of percutaneous mitral annular reduction for the therapy of functional mitral regurgitation in patients with heart failure Catheter Cardiovasc Interv 2006;68:205-210.[Medline]
  12. Romano MA, Bolling SF. Update on mitral repair in dilated cardiomyopathy J Card Surg 2004;19:396-400.[Medline]
  13. Smolens IA, Pagani FD, Deeb GM, Prager RL, Sonnad SS, Bolling SF. Prophylactic mitral reconstruction for mitral regurgitation Ann Thorac Surg 2001;72:1210-1216.[Abstract/Free Full Text]
  14. Abraham JR, Benson L, Dipchand AI, Kantor PF. Have B-adrenoceptor antagonists or ACE inhibitors altered the natural history of paediatric dilated cardiomyopathy Can J Cardiol 2006;22(Suppl D):157D.
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  16. Boltwood CM, Tei C, Wong M, Shah PM. Quantitative echocardiography of the mitral complex in dilated cardiomyopathy: the mechanism of functional mitral regurgitation Circulation 1983;68:498-508.[Free Full Text]

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Invited Commentary
Richard Mainwaring
Ann. Thorac. Surg. 2008 85: 2088-2089. [Extract] [Full Text] [PDF]



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Ann. Thorac. Surg., June 1, 2008; 85(6): 2088 - 2089.
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