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Left atrial-left ventricular conduit for relief of congenital mitral stenosis in infancy
J THORAC CARDIOVASC SURG 80:782-787, 1980
Left atrial-left ventricular conduit for relief of congenital mitral stenosis in infancy Severe congenital mitral stenosis in the infant poses a difficult problem. We present the case history of an infant in whom a left atrial-left ventricular apical conduit was used to bypass a severely hypoplastic mitral valve. Associated coarctation of the aorta, patent ductus arteriosus, and ventricular septal defect were corrected at the same time. This method of circumventing the mitral valve offers a new approach to the relief of congenital mitral hypoplasia in small infants.
Hillel Laks, M.D.* William E. Hellenbrand, M.D.,** Charles Kleinman, M.D.,** and Norman S. Talner, M.D.,*** New Haven, Conn.
COngenital mitral stenosis poses a challenging problem in the infant. This condition is frequently associated with other congenital anomalies, particularly hypoplastic left ventricle, aortic stenosis, interrupted aortic arch, and coarctation of the aorta. Attempts at mitral valvulotomy and valve replacement in the small infant have been attended with a high mortality rate. We describe the case history of a 6-week-old infant with mitral stenosis, coarctation of the aorta, patent ductus arteriosus, and ventricular septal defect in whom a left atrial-left ventricular conduit was used to relieve the obstruction caused by the severely hypoplastic mitral valve. Case report An 8-week-old male infant was born after a term pregnancy. He had a history of rapid breathing and poor feeding since the age of 3 weeks. On physical examination he weighed 3.9 kg and was 58 ern long. He was mildly cyanotic and in respiratory distress, with a heart rate of 170 beats/ min and a respiratory rate of 100 breaths/min. There was a prominent right ventricular impulse, normal first heart sound, accentuated pulmonic component of the second heart sound, a Grade 2/6 ejection systolic murmur heard at the mid-left sternal border, and a Grade 2/4 diastolic murmur heard at the apex. The lungs were clear and the liver was palpable 3 ern From Yale University School of Medicine, New Haven, Conn. Received for publication April 7. 1980. Accepted for publication April 22, 1980. Address for reprints: Hillel Laks, M.D., Yale University School of Medicine, Department of Surgery, Cardiothoracic Section, 333 Cedar St., P.O. Box 3333, New Haven, Conn. 06510. *Associate Professor. Department of Surgery. **Assistant Professor, Department of Pediatric Cardiology. ***Professor, Department of Pediatric Cardiology.
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below the costal margin. The chest roentgenogram revealed cardiomegaly and increased pulmonary vascularity. The electrocardiogram showed right ventricular hypertrophy. M-mode echocardiography (Fig. I) showed that the left ventricular cavity measured 8 mm in diastole, which was below the fifth percentile for the infant's body surface area.' The left atrial cavity was markedly dilated and measured 25 mm in diameter. The left atrial-to-aortic ratio was elevated to 2.5. Multiple diastolic echoes from the mitral valve were suggestive of mitral stenosis. Real-time echocardiography using the coronal short axis view" showed marked left atrial enlargement with bowing of the atrial septum into the right atrial cavity with a closed foramen ovale. There was marked thickening of the mitral valve with a measured orifice of only 3 mm in diastole with minimal opening of the valve leaflets. Cardiac catheterization was performed on the day of admission. The results are shown in Fig. 2. The pulmonary artery pressure was at systemic levels with a mean wedge pressure of 23 mm Hg compared to a simultaneous recorded left ventricular end-diastolic pressure of 8 mm Hg. The oxygen consumption" was 186 rnl/rnin/rn" with a systemic arteriovenous oxygen content difference of 7.0 vol % and a systemic flow of 2.7 L'min/rn". Angiography demonstrated a diminutive mitral valve orifice with minimal excursion and no mitral insufficiency. The left ventricular cavity was small and the papillary muscles could not be identified. There was a patent ductus arteriosus with right-to-left shunting and a juxtaductal coarctation of the aorta. The surgical procedure was performed on Oct. 25, 1979. A left thoracotomy in the fourth intercostal space was performed and the incision extended across the sternum into the right side of the chest. The coarctation of the aorta was exposed, the patent ductus arteriosus ligated, and the pericardium was opened. The left atrium right ventricle, and pulmonary artery were markedly enlarged. After heparinization the ascending aorta, right atrium, and left atrium were cannulated, the patient was placed on cardiopulmonary bypass, and the blood was cooled. While cooling was in progress, the coarctation was repaired with a polytetrafluoroethylene patch placed across the coarctation site. After 25 minutes of cooling, when
0022-5223/80/1 10782+06$00.60/0 © 1980 The C. V. Mosby Co.
Volume 80 Number 5 November , 1980
Congenital mitral stenosis
783
Fig. 1. Preoperative two-dimensional echocardiogram from the subxiphoid view (A) with diagrammatic repre sentation (8). Enlarged left atrium (LA) is seen with tiny mitral orifice (op en arrow) measuring 3 mm acro ss. The interatrial septum (s olid arrow) is bowing toward the right atrial cavity (RA). RV, Right ventricle . the tympanic temperature reached 18° C, the aorta was cross-clamped and 50 ml of co ld blood with potassium chl oride (25 mEq /L ) was infused slowly in the aorti c root. Bypa ss was discontinued , the right atrial cannula was remov ed, and an incisio n was made in the right atrium. The ventric ular septal defe ct was identified beneath the septal leaflet of the tricuspid valve . Because it was oval with fibrous edge s, it was closed via the tricuspid orifice without a patch with horizontal mattress sutures and pledgets. A vertical inci sion then was made through the atrial septum and the mitral valve was identified. The orifice was 3 mm in diameter, with a long tubular orifice into the left ve ntricle . It appeared that valvulotomy would be ineffective in view of the severe annular hypoplasia and that excision of the valve and placement of a prosthesis in the left atrial chamber was not feasible owing to the small size of the heart. For these reasons it was decided to insert the left atrial-left ventr icular conduit as a means of bypassing the hypopla stic mitral valve . Therefore, an incision was made down the lateral aspect of the left atrial appendage into the left atrial chamber and a 12 mm porcine valved conduit (Hancock) was beveled and sutured to the left atrium with a running suture of 5-0 Prolene. An incision then was made in the left ventricle starting at its apex and extending upward between the left anterior descending coronary artery and its diagonal branch , as shown in Fig . 3. The hypopl astic tubul ar mitral valve could be seen with two small papillary muscle s. The distal end of the conduit was then also beveled and sutured to the left ventricle with a running suture of 5-0 Prolene . After a period of arrest lasting 45 minutes, the right atr ial cannula again was inserted into the right atrium and bypass was reinstituted . Air was aspirated from the heart and the
aort ic cross-clamp was relea sed . Myocardial protection included system ic cooling, cold blood cardioplegia given immediately after cro ss-clamping , and topical hypothermia during the period of clamping. The blood was rew armed and the patient weaned from cardiopulmonary bypass without difficult y and without the use of inotropi c agent s . At the conclusion of the procedure the left atrial pressure was 8 mm Hg with a systemi c systolic blood pres sure of 85 mm Hg. There was no step-up in oxygen saturation between the superior vena cava and the pulmonary artery . A sheet of silicone rubber was used in front of the conduit to facilitate reoperation in the future . Postoperati vely , the patient had respiratory difficulties with exce ssive secretions but was extubated on the twelfth postoperative day . Postoperative echocardiography showed persistent severe mitral steno sis with minimal opening of the valve. The left atrium was enl arged , with a diameter of 25 mm and an aorti c-to-Ieft atrial rat io of 2.5 . The left ve ntricular ca vity was enlarged compared to the preoperative measurement with an end-diastolic diameter of 18 mm, which is within normal limits. The left ventricular ejection fraction appeared norm al. The real-time study from the subxiphoid view also showed bowing of the atria l septum tow ard the right atrial cavit y. The conduit orifice into the left atrium was widely patent , but the porcine valve could not be evaluated . Repeat cardiac catheterization was undertaken I month following the procedure . The pre ssures and saturatio ns are shown in Fig . 2. The oxygen con sumption wa s reduced from the preoperative value to 129 ml/rnin /m " de spite a reduction in the system ic arteriovenous oxygen content d ifference to 4 .5 vol%, and the systemic flow was ca lculated at 2.7
The Journal of
784
Laks et al.
SVC
Thoracic and Cardiovascular Surgery
Wedge
=26 v =25 m =23
'0
SVC
@
RV
@
PREOPERATIVE
CATHETERIZATION
POSTOPERATIVE
60/5
CATHETERIZATION
Fig. 2. The results of cardiac catheterization before and after operation are shown. The numbers in circles indicate the oxygen saturation and the numbers without circles indicate the pressure in millimeters of mercury. SVC. Superior vena cava. RA. Right atrium. RV. Right ventricle. PA. Pulmonary artery. LA. Left atrium. LV. Left ventricle. The asterisk (*) and dagger (t) indicate simultaneous pressure measurements.
Fig. 3. Intraoperative photograph showing the 12 mm conduit anastomosed to the left atrium and left ventricle. The incision in the ventricle was made between the left anterior descending coronary artery and its diagonal branch. View from the left side with the sternal retractor blade on the inferior aspect of the transverse bilateral thoracotomy incision.
L'min/rn". The angiograms (Figs. 4 and 5) showed a large left atrium, a patent conduit connecting the atrium and ventricle, and a small-sized left ventricular cavity. The gradient of 9 mm Hg between the left atrium and left ventricle was at the level of the porcine valve. There was no gradient across the site of coractation repair. Angiographically, there was a
small residual ventricular septal defect with no step-up in oxygen saturation and with a pulmonary artery pressure that was half systemic. The infant was seen as an outpatient 6 months postoperatively. His weight had increased from 3.9 to 5.4 kg and he was doing well.
Volume 80 Number 5
Congenital mitral stenosis
785
November, 1980
Discussion Congenital mitral stenosis is a rare lesion occurring in only six of 2,178 patients (0.003 %) admitted to the New England Regional Infant Program:' and 1.2% of autopsied patients with congenital heart disease . 5 The association of left ventricular obstructive lesions, ventricular septal defect, and congenital mitral stenosis has been described by Shone and others " and by Rosenquist. 7 Mitral stenosis may also be associated with an endocardial cushion defect. M The anatomic types of congenital mitral stenosis have been described by Ruckman and Van Praagh? and include (l) typical congenital mitral stenosis, (2) hypoplastic mitral stenosis, (3) supramitral ring, and (4) parachute mitral valve . The lesion seen at operation in this patient conforms with some features of "typical congenital mitral stenosis" described by these authors, as the chordae were shortened and thickened, the interchordal spaces were obliterated, and the papillary muscles were underdeveloped. The lesion also conforms with the subgroup in which there is "loss of interpapillary distance." The mitral valve orifice was markedly narrowed to 3 to 4 mm as seen on the echocardiogram (Fig. I) and confirmed at operation. The associated lesions included a mildly hypoplastic left ventricle, coarctation of the aorta , ventricular septal defect, and patent ductus arteriosus, which were repaired during the same procedure . Surgical relief of congenital mitral stenosis has not been satisfactory except in the case in which a supravalvular ring is the predominant lesion 10 and can be resected . Valvuloplasty might provide some relief for certain types of congenital mitral stenosis," but this procedure is particularly difficult in small infants and is not applicable if there is significant mitral annular hypoplasia, as in our case. Excision and replacement of the valve are avoided wherever possible to allow for growth of the anulus. In addition, in infants the anulus may be too small to allow for valve insertion at the level of the anulus. In this situation it may become necessary to place the valve in the supraannular position, suturing it to the left atrial wall and obliterating the left atrial appendage . The size of the left ventricle is critical in these patients . If it is judged to be too small , relief of the mitral stenosis will not solve the problem and a palliative procedure may be indicated." Echocardiography is of value, as in this case, in evaluating the mitral valve and left ventricular size." The smallest sized prosthetic valves currently avail able include the 15 mm Ionescu-Shiley glutaraldehydepreserved pericardial valve, the 17 mm St. Jude valve, the 19 mm Bjork-Shiley valve, the 19 mm modi -
Fig. 4. Postoperative angiogram in the anteroposterior view showing the conduit connecting the left atrium and left ventricle. The actual size of the valve ring is 12mm. The catheter has been passed retrogradely from the aorta into the left atrium via the conduit.
Fig. S. Postoperative angiogram in the lateral view showing the left atrium connected by the conduit to the left ventricle. The coarctation repair site shows no residual narrowing.
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fied leaflet Hancock glutaraldehyde-preserved porcine valve, and the unmodified 19 mm porcine valves (Hancock and Carpentier-Edwards). Braunwald and associates'" have described experimental experience with the development of small heterograft valves. The 12 mm porcine valve (Hancock) has a calculated orifice of 0.53 ern", these calculations being based on the in vitro study of four valves at flows of about 80 mIlsec. * In our patient, we found a 9 mm Hg gradient across the porcine valve with no gradients across the anastomoses at a calculated systemic flow of 2.7 L'min/rn", which would give a calculated mitral valve area of 0.3 ern" or an index of 1.2 cm 2/m 2 • This is disappointing but is consistent with the findings of higher gradients in the smaller porcine valves in other patients after insertion of porcine valved conduits. 14 The left ventricular enddiastolic pressure (10 mm Hg) found postoperatively, which is elevated in this age child, was thought to be due to the small left ventricular size. The bioprosthetic valves have the advantage of not requiring anticoagulants, but the struts may present a problem even when the valve is placed in the supra-annular position. In addition, the anulus-to-orifice ratio is particularly unsatisfactory in the small-sized valves. The St. Jude valve has a low profile which is advantageous but is associated with the problems of anticoagulation or the risk of thromboembolism. A porcine heterograft removed from a tubular prosthesis has been placed in the annular position in an 18-month-old infant with mitral stenosis.P In the infant under 6 months of age, it is possible that a similar valve removed from a 12 mm conduit could be placed in the supravalvular position but might cause obstruction to the pulmonary veins. Use of a left atrial-left ventricular conduit is applicable in cases in which the congenital mitral stenosis cannot be relieved directly and there is no room for a supravalvular prosthetic valve. It has the theoretical advantage of allowing the anulus to grow, making it possible to replace the valve at a later time, or of replacing the conduit at a staged procedure. For this reason, silicone rubber was used as a pericardial substitute to facilitate reoperation. This procedure, which we have not seen previously described, may offer a successful method of circumventing the mitral valve in infants with severe congenital mitral stenosis.
Addendum On July 9, 1980, the patient was admitted to the hospital with high fevers and respiratory distress. Chest x-ray film was
*Personal communication: Hancock Laboratories, Inc., Anaheim, Calif. February, 1980.
unchanged. Echocardiography showed a decrease in left atrial size from previous studies. The atrial septum was no longer bowed. The mitral valve looked atretic and the left ventricle and aorta appeared hypoplastic. The patient was treated with antibiotics and diuretics, but had an unexpected cardiac arrest on July II, 1980, and could not be resuscitated. Postmortem examination of the heart showed the surgical correction to be intact, with no obstruction to the valve or conduit. The mitral valve was completely occluded. The left ventricle and aorta appeared to be hypoplastic; the silicone rubber pericardial substitute did not appear to be constricting and facilitated exposure of the heart. We would like to acknowledge the experimental work of Robert J. Szarnicki, M.D., who reported on the use of a left atrial-left ventricular conduit in dogs at the World Congress of Pediatric Cardiology, London, England, 1980.
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REFERENCES Roge CLL, Silverman NH, Hart PA, Ray MR: Cardiac structure growth pattern determined by echocardiography. Circulation 57:285-290, 1978 Lange LW, Sahn OJ, Allen HD, Goldberg SJ: Subxiphoid cross-sectional echocardiography in infants and children with congenital heart disease. Circulation 59:513-524, 1979 Lister G, Hoffman lIE, Rudolph AM: Oxygen uptake in infants and children. A simple method for measurement. Pediatrics 53:656-662, 1974 Collins-Nakai RL, Rosenthal A, Castaneda AR, Bernhard WF, Nadas AS: Congenital mitral stenosis. A review of 20 years' experience. Circulation 56: 1039-1047, 1977 Nadas AS, Fyler DC: Pediatric Cardiology, ed 3, Philadelphia, 1972, W. B. Saunders Company, pp 683687 Shone 10, Sellers RD, Anderson RC, Adams P Jr. Lillihei CW, Edwards JE: The developmental complex of "parachute mitral valve," supravalvular ring of the left atrium, subaortic stenosis, and coarctation of the aorta. Am J Cardiolll:714-720, 1963 Rosenquist GC; Congenital mitral valve disease associated with coarctation of the aorta. Circulation 49:985993, 1974 Bloom KR, Freedom RM, Williams CM, Trusler GA, Rowe RD: Echocardiographic recognition of atrioventricular valve stenosis associated with endocardial cushion defect. Pathologic and surgical correlates. Am J Cardiol 44:1326-1331, 1979 Ruckman RN, Van Praagh R: Anatomic types of congenital mitral stenosis. Report of 49 autopsy cases with consideration of diagnosis and surgical implications. Am J Cardiol 42:592-601, 1978 Chung KY, Manning JA, Lipchik EO, Gramiak R, Mahoney EB: Isolated supravalvular stenosing ring of left atrium. Diagnosis before operation and successful surgical treatment. Chest 65:25-28, 1974 Carpentier A, Guerinon J, Deloche A: Pathology of the mitral valve. Introduction to plastic and reconstructive
Volume 80 Number 5 November, 1980
valve surgery. The Mitral Valve, D. Kalmanson, ed., Acton, Mass., 1976, Publishing Sciences Group, p 65 12 Norwood WI, Kirklin JK, Sanders SP: Hypoplastic left heart syndrome. Experience with palliative surgery. Am J Cardiol 45:87-91, 1980 13 Braunwald NS, Brais M, Castaneda A: Considerations in the development of artificial heart valve substitutes for use in infants and small children. J THORAC CARDIOVASC SURG 72:539-546, 1976
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14 Hellenbrand WE, Laks H, Kleinman CS, Stansel HC, Talner NS: Hemodynamic evaluation after reconstruction of the right ventricular outflow tract with a porcine valve prosthesis. Circulation 60:Suppl 2: 169, 1979 15 Crawford FA, Selby JH Jr, Joransen JA: Mitral valve replacement with a porcine heterograft in an infant. J THORAC CARDIOVASC SURG 75:705-708, 1978
Left atrial-left ventricular conduit for relief of congenital mitral stenosis in infancy Severe congenital mitral stenosis in the infant poses a difficult problem. We present the case history of an infant in whom a left atrial-left ventricular apical conduit was used to bypass a severely hypoplastic mitral valve. Associated coarctation of the aorta, patent ductus arteriosus, and ventricular septal defect were corrected at the same time. This method of circumventing the mitral valve offers a new approach to the relief of congenital mitral hypoplasia in small infants.
Hillel Laks, M.D.* William E. Hellenbrand, M.D.,** Charles Kleinman, M.D.,** and Norman S. Talner, M.D.,*** New Haven, Conn.
COngenital mitral stenosis poses a challenging problem in the infant. This condition is frequently associated with other congenital anomalies, particularly hypoplastic left ventricle, aortic stenosis, interrupted aortic arch, and coarctation of the aorta. Attempts at mitral valvulotomy and valve replacement in the small infant have been attended with a high mortality rate. We describe the case history of a 6-week-old infant with mitral stenosis, coarctation of the aorta, patent ductus arteriosus, and ventricular septal defect in whom a left atrial-left ventricular conduit was used to relieve the obstruction caused by the severely hypoplastic mitral valve. Case report An 8-week-old male infant was born after a term pregnancy. He had a history of rapid breathing and poor feeding since the age of 3 weeks. On physical examination he weighed 3.9 kg and was 58 ern long. He was mildly cyanotic and in respiratory distress, with a heart rate of 170 beats/ min and a respiratory rate of 100 breaths/min. There was a prominent right ventricular impulse, normal first heart sound, accentuated pulmonic component of the second heart sound, a Grade 2/6 ejection systolic murmur heard at the mid-left sternal border, and a Grade 2/4 diastolic murmur heard at the apex. The lungs were clear and the liver was palpable 3 ern From Yale University School of Medicine, New Haven, Conn. Received for publication April 7. 1980. Accepted for publication April 22, 1980. Address for reprints: Hillel Laks, M.D., Yale University School of Medicine, Department of Surgery, Cardiothoracic Section, 333 Cedar St., P.O. Box 3333, New Haven, Conn. 06510. *Associate Professor. Department of Surgery. **Assistant Professor, Department of Pediatric Cardiology. ***Professor, Department of Pediatric Cardiology.
782
below the costal margin. The chest roentgenogram revealed cardiomegaly and increased pulmonary vascularity. The electrocardiogram showed right ventricular hypertrophy. M-mode echocardiography (Fig. I) showed that the left ventricular cavity measured 8 mm in diastole, which was below the fifth percentile for the infant's body surface area.' The left atrial cavity was markedly dilated and measured 25 mm in diameter. The left atrial-to-aortic ratio was elevated to 2.5. Multiple diastolic echoes from the mitral valve were suggestive of mitral stenosis. Real-time echocardiography using the coronal short axis view" showed marked left atrial enlargement with bowing of the atrial septum into the right atrial cavity with a closed foramen ovale. There was marked thickening of the mitral valve with a measured orifice of only 3 mm in diastole with minimal opening of the valve leaflets. Cardiac catheterization was performed on the day of admission. The results are shown in Fig. 2. The pulmonary artery pressure was at systemic levels with a mean wedge pressure of 23 mm Hg compared to a simultaneous recorded left ventricular end-diastolic pressure of 8 mm Hg. The oxygen consumption" was 186 rnl/rnin/rn" with a systemic arteriovenous oxygen content difference of 7.0 vol % and a systemic flow of 2.7 L'min/rn". Angiography demonstrated a diminutive mitral valve orifice with minimal excursion and no mitral insufficiency. The left ventricular cavity was small and the papillary muscles could not be identified. There was a patent ductus arteriosus with right-to-left shunting and a juxtaductal coarctation of the aorta. The surgical procedure was performed on Oct. 25, 1979. A left thoracotomy in the fourth intercostal space was performed and the incision extended across the sternum into the right side of the chest. The coarctation of the aorta was exposed, the patent ductus arteriosus ligated, and the pericardium was opened. The left atrium right ventricle, and pulmonary artery were markedly enlarged. After heparinization the ascending aorta, right atrium, and left atrium were cannulated, the patient was placed on cardiopulmonary bypass, and the blood was cooled. While cooling was in progress, the coarctation was repaired with a polytetrafluoroethylene patch placed across the coarctation site. After 25 minutes of cooling, when
0022-5223/80/1 10782+06$00.60/0 © 1980 The C. V. Mosby Co.
Volume 80 Number 5 November , 1980
Congenital mitral stenosis
783
Fig. 1. Preoperative two-dimensional echocardiogram from the subxiphoid view (A) with diagrammatic repre sentation (8). Enlarged left atrium (LA) is seen with tiny mitral orifice (op en arrow) measuring 3 mm acro ss. The interatrial septum (s olid arrow) is bowing toward the right atrial cavity (RA). RV, Right ventricle . the tympanic temperature reached 18° C, the aorta was cross-clamped and 50 ml of co ld blood with potassium chl oride (25 mEq /L ) was infused slowly in the aorti c root. Bypa ss was discontinued , the right atrial cannula was remov ed, and an incisio n was made in the right atrium. The ventric ular septal defe ct was identified beneath the septal leaflet of the tricuspid valve . Because it was oval with fibrous edge s, it was closed via the tricuspid orifice without a patch with horizontal mattress sutures and pledgets. A vertical inci sion then was made through the atrial septum and the mitral valve was identified. The orifice was 3 mm in diameter, with a long tubular orifice into the left ve ntricle . It appeared that valvulotomy would be ineffective in view of the severe annular hypoplasia and that excision of the valve and placement of a prosthesis in the left atrial chamber was not feasible owing to the small size of the heart. For these reasons it was decided to insert the left atrial-left ventr icular conduit as a means of bypassing the hypopla stic mitral valve . Therefore, an incision was made down the lateral aspect of the left atrial appendage into the left atrial chamber and a 12 mm porcine valved conduit (Hancock) was beveled and sutured to the left atrium with a running suture of 5-0 Prolene. An incision then was made in the left ventricle starting at its apex and extending upward between the left anterior descending coronary artery and its diagonal branch , as shown in Fig . 3. The hypopl astic tubul ar mitral valve could be seen with two small papillary muscle s. The distal end of the conduit was then also beveled and sutured to the left ventricle with a running suture of 5-0 Prolene . After a period of arrest lasting 45 minutes, the right atr ial cannula again was inserted into the right atrium and bypass was reinstituted . Air was aspirated from the heart and the
aort ic cross-clamp was relea sed . Myocardial protection included system ic cooling, cold blood cardioplegia given immediately after cro ss-clamping , and topical hypothermia during the period of clamping. The blood was rew armed and the patient weaned from cardiopulmonary bypass without difficult y and without the use of inotropi c agent s . At the conclusion of the procedure the left atrial pressure was 8 mm Hg with a systemi c systolic blood pres sure of 85 mm Hg. There was no step-up in oxygen saturation between the superior vena cava and the pulmonary artery . A sheet of silicone rubber was used in front of the conduit to facilitate reoperation in the future . Postoperati vely , the patient had respiratory difficulties with exce ssive secretions but was extubated on the twelfth postoperative day . Postoperative echocardiography showed persistent severe mitral steno sis with minimal opening of the valve. The left atrium was enl arged , with a diameter of 25 mm and an aorti c-to-Ieft atrial rat io of 2.5 . The left ve ntricular ca vity was enlarged compared to the preoperative measurement with an end-diastolic diameter of 18 mm, which is within normal limits. The left ventricular ejection fraction appeared norm al. The real-time study from the subxiphoid view also showed bowing of the atria l septum tow ard the right atrial cavit y. The conduit orifice into the left atrium was widely patent , but the porcine valve could not be evaluated . Repeat cardiac catheterization was undertaken I month following the procedure . The pre ssures and saturatio ns are shown in Fig . 2. The oxygen con sumption wa s reduced from the preoperative value to 129 ml/rnin /m " de spite a reduction in the system ic arteriovenous oxygen content d ifference to 4 .5 vol%, and the systemic flow was ca lculated at 2.7
The Journal of
784
Laks et al.
SVC
Thoracic and Cardiovascular Surgery
Wedge
=26 v =25 m =23
'0
SVC
@
RV
@
PREOPERATIVE
CATHETERIZATION
POSTOPERATIVE
60/5
CATHETERIZATION
Fig. 2. The results of cardiac catheterization before and after operation are shown. The numbers in circles indicate the oxygen saturation and the numbers without circles indicate the pressure in millimeters of mercury. SVC. Superior vena cava. RA. Right atrium. RV. Right ventricle. PA. Pulmonary artery. LA. Left atrium. LV. Left ventricle. The asterisk (*) and dagger (t) indicate simultaneous pressure measurements.
Fig. 3. Intraoperative photograph showing the 12 mm conduit anastomosed to the left atrium and left ventricle. The incision in the ventricle was made between the left anterior descending coronary artery and its diagonal branch. View from the left side with the sternal retractor blade on the inferior aspect of the transverse bilateral thoracotomy incision.
L'min/rn". The angiograms (Figs. 4 and 5) showed a large left atrium, a patent conduit connecting the atrium and ventricle, and a small-sized left ventricular cavity. The gradient of 9 mm Hg between the left atrium and left ventricle was at the level of the porcine valve. There was no gradient across the site of coractation repair. Angiographically, there was a
small residual ventricular septal defect with no step-up in oxygen saturation and with a pulmonary artery pressure that was half systemic. The infant was seen as an outpatient 6 months postoperatively. His weight had increased from 3.9 to 5.4 kg and he was doing well.
Volume 80 Number 5
Congenital mitral stenosis
785
November, 1980
Discussion Congenital mitral stenosis is a rare lesion occurring in only six of 2,178 patients (0.003 %) admitted to the New England Regional Infant Program:' and 1.2% of autopsied patients with congenital heart disease . 5 The association of left ventricular obstructive lesions, ventricular septal defect, and congenital mitral stenosis has been described by Shone and others " and by Rosenquist. 7 Mitral stenosis may also be associated with an endocardial cushion defect. M The anatomic types of congenital mitral stenosis have been described by Ruckman and Van Praagh? and include (l) typical congenital mitral stenosis, (2) hypoplastic mitral stenosis, (3) supramitral ring, and (4) parachute mitral valve . The lesion seen at operation in this patient conforms with some features of "typical congenital mitral stenosis" described by these authors, as the chordae were shortened and thickened, the interchordal spaces were obliterated, and the papillary muscles were underdeveloped. The lesion also conforms with the subgroup in which there is "loss of interpapillary distance." The mitral valve orifice was markedly narrowed to 3 to 4 mm as seen on the echocardiogram (Fig. I) and confirmed at operation. The associated lesions included a mildly hypoplastic left ventricle, coarctation of the aorta , ventricular septal defect, and patent ductus arteriosus, which were repaired during the same procedure . Surgical relief of congenital mitral stenosis has not been satisfactory except in the case in which a supravalvular ring is the predominant lesion 10 and can be resected . Valvuloplasty might provide some relief for certain types of congenital mitral stenosis," but this procedure is particularly difficult in small infants and is not applicable if there is significant mitral annular hypoplasia, as in our case. Excision and replacement of the valve are avoided wherever possible to allow for growth of the anulus. In addition, in infants the anulus may be too small to allow for valve insertion at the level of the anulus. In this situation it may become necessary to place the valve in the supraannular position, suturing it to the left atrial wall and obliterating the left atrial appendage . The size of the left ventricle is critical in these patients . If it is judged to be too small , relief of the mitral stenosis will not solve the problem and a palliative procedure may be indicated." Echocardiography is of value, as in this case, in evaluating the mitral valve and left ventricular size." The smallest sized prosthetic valves currently avail able include the 15 mm Ionescu-Shiley glutaraldehydepreserved pericardial valve, the 17 mm St. Jude valve, the 19 mm Bjork-Shiley valve, the 19 mm modi -
Fig. 4. Postoperative angiogram in the anteroposterior view showing the conduit connecting the left atrium and left ventricle. The actual size of the valve ring is 12mm. The catheter has been passed retrogradely from the aorta into the left atrium via the conduit.
Fig. S. Postoperative angiogram in the lateral view showing the left atrium connected by the conduit to the left ventricle. The coarctation repair site shows no residual narrowing.
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The Journal of Thoracic and Cardiovascular Surgery
Laks et al.
fied leaflet Hancock glutaraldehyde-preserved porcine valve, and the unmodified 19 mm porcine valves (Hancock and Carpentier-Edwards). Braunwald and associates'" have described experimental experience with the development of small heterograft valves. The 12 mm porcine valve (Hancock) has a calculated orifice of 0.53 ern", these calculations being based on the in vitro study of four valves at flows of about 80 mIlsec. * In our patient, we found a 9 mm Hg gradient across the porcine valve with no gradients across the anastomoses at a calculated systemic flow of 2.7 L'min/rn", which would give a calculated mitral valve area of 0.3 ern" or an index of 1.2 cm 2/m 2 • This is disappointing but is consistent with the findings of higher gradients in the smaller porcine valves in other patients after insertion of porcine valved conduits. 14 The left ventricular enddiastolic pressure (10 mm Hg) found postoperatively, which is elevated in this age child, was thought to be due to the small left ventricular size. The bioprosthetic valves have the advantage of not requiring anticoagulants, but the struts may present a problem even when the valve is placed in the supra-annular position. In addition, the anulus-to-orifice ratio is particularly unsatisfactory in the small-sized valves. The St. Jude valve has a low profile which is advantageous but is associated with the problems of anticoagulation or the risk of thromboembolism. A porcine heterograft removed from a tubular prosthesis has been placed in the annular position in an 18-month-old infant with mitral stenosis.P In the infant under 6 months of age, it is possible that a similar valve removed from a 12 mm conduit could be placed in the supravalvular position but might cause obstruction to the pulmonary veins. Use of a left atrial-left ventricular conduit is applicable in cases in which the congenital mitral stenosis cannot be relieved directly and there is no room for a supravalvular prosthetic valve. It has the theoretical advantage of allowing the anulus to grow, making it possible to replace the valve at a later time, or of replacing the conduit at a staged procedure. For this reason, silicone rubber was used as a pericardial substitute to facilitate reoperation. This procedure, which we have not seen previously described, may offer a successful method of circumventing the mitral valve in infants with severe congenital mitral stenosis.
Addendum On July 9, 1980, the patient was admitted to the hospital with high fevers and respiratory distress. Chest x-ray film was
*Personal communication: Hancock Laboratories, Inc., Anaheim, Calif. February, 1980.
unchanged. Echocardiography showed a decrease in left atrial size from previous studies. The atrial septum was no longer bowed. The mitral valve looked atretic and the left ventricle and aorta appeared hypoplastic. The patient was treated with antibiotics and diuretics, but had an unexpected cardiac arrest on July II, 1980, and could not be resuscitated. Postmortem examination of the heart showed the surgical correction to be intact, with no obstruction to the valve or conduit. The mitral valve was completely occluded. The left ventricle and aorta appeared to be hypoplastic; the silicone rubber pericardial substitute did not appear to be constricting and facilitated exposure of the heart. We would like to acknowledge the experimental work of Robert J. Szarnicki, M.D., who reported on the use of a left atrial-left ventricular conduit in dogs at the World Congress of Pediatric Cardiology, London, England, 1980.
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valve surgery. The Mitral Valve, D. Kalmanson, ed., Acton, Mass., 1976, Publishing Sciences Group, p 65 12 Norwood WI, Kirklin JK, Sanders SP: Hypoplastic left heart syndrome. Experience with palliative surgery. Am J Cardiol 45:87-91, 1980 13 Braunwald NS, Brais M, Castaneda A: Considerations in the development of artificial heart valve substitutes for use in infants and small children. J THORAC CARDIOVASC SURG 72:539-546, 1976
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14 Hellenbrand WE, Laks H, Kleinman CS, Stansel HC, Talner NS: Hemodynamic evaluation after reconstruction of the right ventricular outflow tract with a porcine valve prosthesis. Circulation 60:Suppl 2: 169, 1979 15 Crawford FA, Selby JH Jr, Joransen JA: Mitral valve replacement with a porcine heterograft in an infant. J THORAC CARDIOVASC SURG 75:705-708, 1978