Ann Thorac Surg 2005;79:337-339
© 2005 The Society of Thoracic Surgeons
Case report
Application of Papillary Muscle Sling Concept in an Infant as a Biological Bridge to Transplantation
Nai-Hsin Chi, MDa,
Shu-Chien Huang, MDa,
His-Yu Yu, MDa,
Yih-Sharng Chen, MD*,a,
Shoei-Shan Wang, MDa
a Department of Cardiothoracic Surgery, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
Accepted for publication August 21, 2003.
* Address reprint requests to Dr Chen, Department of Cardiothoracic Surgery, National Taiwan University Hospital, 7 Chung-Shan S Rd, Taipei 100, Taiwan
yschen11{at}yahoo.com.tw
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Abstract
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We successfully applied the papillary muscle sling concept in mitral valve reconstruction of an infant with dilated cardiomyopathy. This new method of banding the two papillary muscles together can shorten the distance of the base between the two papillary muscles, reduce the severity of mitral regurgitation, and remodel the dilated left ventricle without any mitral stenosis. The infant survived after this bridge-to-transplantation procedure and was successfully transplanted.
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Introduction
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Dilated cardiomyopathy is the major cause of congestive heart failure in pediatric patients. Biological bridge procedures, such as left ventricular reduction and mitral valve reconstruction are suitable for infants that are refractory to the maximal medical therapy, because there is no appropriate ventricular assist device and a limited source of donors for the infant. However, a fixed mitral ring is not suitable for the potential growing pediatric patients. Concept of papillary muscle sling was advocated and successfully applied in adult patients [1]. We applied this similar concept in an infant.
The patient is a 1-year-old male infant (weight, 7.8 kg) with symptoms consisting of fever, dyspnea, poor appetite, and hepatomegaly 2 days before admission. Shock subsequently developed in spite of ventilator and vasopressor support. The chest roentenogram showed an increased heart size (Fig 1a) Echocardiogram showed poor left ventricular ejection fraction (23%), moderate mitral regurgitation, and tricuspid regurgitation (Fig 2a). Catheterization revealed dilated ventricles with poor left ventricular function. Left ventricle end-diastolic pressure was 23 mm Hg and pulmonary artery pressure was elevated with a mean of 38 mm Hg. Endomyocardial biopsy failed to confirm the diagnosis of acute myocarditis, but cardiomyopathy was likely. The clinical course of the patient fluctuated with repeated episodes of infection and pneumonia for 8 weeks, and the heart function failed to improve as shown by repeated echocardiography. He was placed on the waiting list for heart transplantation.
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Fig 1. (a) Preoperative chest roentgenogram with cardiothoracic ratio of 0.73. (b) Postoperative chest roentgenogram with cardiothoracic ratio of 0.55.
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Fig 2. (a) Preoperative echocardiogram: apical four-chamber view showed severe mitral regurgitation. (b) Postoperative echocardiogram, parasternal long axis view. (Arrow indicates the sling.) (c) Postoperative echocardiogram showed trivial mitral regurgitation and good coaptation of mitral valve. (Arrow indicates the loop of tube around the papillary muscle.) (d) The gross finding of the excised heart. (Arrow indicates the loop.) (LA = left atrium; LV = left ventricle.)
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Due to the lack of infant heart donors and the progressive deterioration of his clinical course, despite support by dopamine 20 µg/kg/min, dobutamine 20 µg/kg/min, milrinone 0.5 µg/kg/min, and epinephrine 0.1 µg/kg/min, surgery was undertaken for a biological bridge to transplantation. After median sternotomy, bi-caval cannulation was performed and the mitral valve was exposed through interatrial approach after cardiac arrest by cold blood cardioplegic solution. Multiple stitches with 4-0 Ticron (US Surgical, Tyco Healthcare Group, CT) on the posterior annulus of the mitral valve were placed for later annuloplasty and temporary slight traction for better exposure. After analyzing the anatomical mitral valve and subvalvular apparatus, there was poor coaptation of the central portion of the mitral valve due to dilated annulus during saline testing and wide displacement of both papillary muscles, with about 2 cm between the bases of the two papillary muscles. We were hesitant to put a mitral ring in an infant because of the growth potential, and we decided to perform functional repair of the mitral valve. Because of the limited space within the left ventricle and no recess found between the papillary muscles, we chose a 3-mm GoreTex tube (WL Gore & Assoc, Flagstaff, AZ) to encircle around the bases of the papillary muscles. Because there was not enough space among the trabecula at the bases of the papillary muscles, the shunt partially encircled two papillary muscles. The papillary muscles were loosely drawn together by shortening the loop of the tube, and the encircled tube was secured with two sutures. The loop did not tightly bind the papillary muscles in union, but was allowed slight up and down displacement of the loop. Saline testing showed minimal leakage, and the pre-placed annulus stitches were tightened as posterior mitral annuloplasty. The patient was removed from cardiopulmonary bypass under milrinone (1 µg/kg/min), dopamine (10 µg/kg/min), dobutamine (10 µg/kg/min), epinephrine (0.05 µg/kg/min), and norepinephrine (0.02 µg/kg/min).
Postoperative echocardiography revealed trivial mitral regurgitation (Fig 2b, c) and left ventricular ejection fraction improved to 36%. The high dose of vasopressor support was gradually tapered to a low dose of milrinone (0.25 µg/kg/min) in a week, and the cardiothoracic ratio improved from 0.73 preoperatively to 0.55 postoperatively (Fig 1b). An attempt to extubate the patient on postoperative day 12 failed. Fortunately he received heart transplantation from a 10-month-old donor 3 weeks after the surgery with excellent results.
Careful examination of the excised heart revealed no thrombus formation around the shunt or within the trabecula of papillary muscle bases. The papillary muscles were well bound by the loop of the tube, and the distance between the two bases of papillary muscles was 1 cm (Fig 2d).
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Comment
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Hvass and colleagues [1] first advocated the papillary muscle sling technique as a palliative procedure for mitral valve reconstruction in adult patients with poor left ventricular function and moderate to severe mitral regurgitation. This new technique shortens the distance between the bases of the papillary muscles and can be regarded as an intracardiac technique of the surgical anterior ventricular endocardial restoration (SAVER) procedure [2] without ventriculotomy (Fig 3a, b). This may lead to left ventricular remodeling for reducing mitral regurgitation and the left ventricle diameter. This internal banding method creates a parachute effect at the papillary muscle and chordae tendinea.
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Fig 3. Concept of papillary muscle sling in different groups of patients. (a) Dilated left ventricle with poor coaptation resulting in mitral regurgitation. (b) Concept of adult patients group. The papillary muscle sling is over the base of the papillary muscles. (c) Concept of infant group. The papillary muscle sling encircles the papillary muscle.
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However, that technique is not suitable for the pediatric or infant patients because there is limited space within the papillary muscle bases of the small heart to encircle the tube. In addition, the potential mitral stenosis may develop according to the pediatric experience of a "parachute" mitral valve. We modified the papillary muscle sling concept and applied this modification to our patient by encircling the papillary muscle only (Fig 3c). In our pediatric patient, we cannot find an adequate accessory papillary muscle recess space to restrict the sling from migration. Thus, we can only put the looped tube around the two papillary muscles. Our method will pull the two papillary muscles closer to remodel the left ventricle, and this method will not create a parachute-like phenomenon at the bases. The looped tube may act as a piston down toward the apex during diastole and upward to the annulus during systole when examining the excised heart, in spite that we cannot detect the change from the echocardiography.
Although the long-term effect of this method has yet to be determined, because the infant received transplantation within 3 weeks, it did provide us with information on the feasibility of applying the concept of internal banding of papillary muscles to pediatric patients.
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References
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- Hvass U, Tapia M, Baron F, Pouzet B, Shafy A. Papillary muscle sling: a new functional approach to mitral repair in patients with ischemic left ventricular dysfunction and functional mitral regurgitation. Ann Thorac Surg. 2003;75:809–811[Abstract/Free Full Text]
- Athanasuleas CL, Stanley AW Jr, Buckberg GD, Dor V, DiDonato M, Blackstone EH. Surgical anterior ventricular endocardial restoration (SAVER) in the dilated remodeled ventricle after anterior myocardial infarction. RESTORE group. J Am Coll Cardiol. 2001;37(5):1199–1209[Medline]
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Abstract
Introduction
