Ann Thorac Surg 1997;63:112-116
© 1997 The Society of Thoracic Surgeons
Original Articles: Cardiovascular
Ross-Konno Operation With Resection of Endocardial Fibroelastosis for Critical Aortic Stenosis With Borderline-Sized Left Ventricle in Neonates
Jacques A. M. van Son, MD, PhD,
Volkmar Falk, MD,
Friedrich W. Mohr, MD
Departments of Cardiovascular Surgery and Pediatric Cardiology, Herzzentrum, University of Leipzig, Leipzig, Germany
Accepted for publication July 17, 1996.
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Abstract
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Background. Critical aortic stenosis with severe concentric left ventricular hypertrophy and endocardial fibroelastosis has a substantial mortality rate when the conventional therapeutic strategy, ie, open surgical or balloon valvuloplasty, is applied. During the last decade, univentricular repair (Norwood operation) and heart transplantation have evolved as the only viable therapeutic options. An alternative in patients with borderline hypoplastic left heart syndrome consists of performance of a Ross-Konno operation with surgical enlargement of the left ventricular cavity, a procedure that has the advantage of achieving a two-ventricle repair.
Methods. Two neonates and 2 young infants with critical aortic stenosis, concentric left ventricular hypertrophy, and severe endocardial fibroelastosis, with echocardiographically documented antegrade flow in the ascending aorta, underwent a Ross-Konno operation combined with extensive endocardial and myocardial resection of the left ventricular septum and free wall. The incision in the ventricular septum was closed with a wide cuff of infundibular muscle that was harvested in continuity with the pulmonary autograft.
Results. In all 4 patients, the operation resulted in normal aortic valve function, marked reductions of width of the left ventricular septum (median, 6.5 mm, versus 11 mm preoperatively) and the left ventricular posterior free wall (median, 8.5 mm, versus 15.5 mm preoperatively), and enlargement of the left ventricular end-diastolic volume (median, 12.5 cm3, versus 6.5 cm3 preoperatively). Three patients had an uneventful recovery, with gradual improvement of left ventricular diastolic and systolic function during the first postoperative week; 1 neonate with associated mitral regurgitation died of left ventricular failure.
Conclusions. The Ross-Konno procedure with resection of endocardial fibroelastosis may be a valuable adjunct for achieving a two-ventricle repair in borderline hypoplastic left heart syndrome. The operation results in enlargement of the left ventricular stroke volume and improvement of left ventricular diastolic function; in addition, resection of endocardial fibroelastosis relieves the mechanical impairment of myocardial function and therefore may promote the potential for left ventricular growth.
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Introduction
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In the broad spectrum of left ventricular outflow tract obstruction (LVOT) in neonates, surgical options traditionally have been dichotomous, consisting of biventricular repair for anomalies on the mild-to-moderate end of the spectrum and univentricular repair for severe anomalies. We report a technique of biventricular repair in hearts with critical aortic stenosis, concentric left ventricular hypertrophy with endocardial fibroelastosis (EFE), and borderline-sized left ventricular volume for which, thus far, univentricular repair or heart transplantation was the only viable option.
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Patient and Methods
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Four patients underwent a Ross-Konno operation with resection of EFE. The ages of the patients were 5 days, 7 days, 5 weeks, and 6 weeks. The median weight was 4.1 kg. The diagnosis of critical aortic stenosis (median gradient 50 mm Hg) was established by echocardiography and cardiac catheterization studies. One patient had undergone a previous balloon valvuloplasty, with resulting aortic regurgitation and left ventricular dilation and dysfunction. In all patients, the aortic valve was bicuspid and dysmorphic. The aortic annulus was hypoplastic in all patients (median diameter, 7 mm; range, 5 to 9 mm). The median diameter of the mitral valve annulus was 9 mm (range, 8 to 12 mm). Concentric left ventricular hypertrophy resulted in a small left ventricular cavity, with a median end-diastolic volume of 6.5 cm3 and with cavity obliteration nearly occurring during systole (Fig 1
). Further echocardiographic measurements are summarized in Table 1. Blood flow in the ascending aorta and aortic arch was antegrade in all patients. Blood flow in the ductus arteriosus was left to right in 3 patients (median systemic arterial oxygen saturation 98%) and bidirectional in 1 patient (systemic arterial oxygen saturation in the upper extremities 98%, and in the lower extremities 90%). One patient had Shone's complex with long-segment tunnel subaortic stenosis. In another patient, EFE extended into the base of the posteromedial papillary muscle, which resulted in mild mitral regurgitation.
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Fig 1. . Preoperative echocardiogram (parasternal short axis in diastole) demonstrating severe concentric hypertrophy of the left ventricular myocardium with small left ventricular cavity (C). Note intense echoes from endocardial fibroelastosis.
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Operative Technique
Through a median sternotomy, the aorta, the main pulmonary artery and its branches, and the ductus arteriosus were mobilized. After initiation of cardiopulmonary bypass using bicaval cannulation, the ductus arteriosus was ligated and the left ventricle was vented. In the presence of marked aortic regurgitation, the aorta was cross-clamped, an aortotomy was made approximately 5 mm distal to the sinotubular junction, and cardioplegic solution was administered directly into the coronary ostia. In the absence of aortic regurgitation, the main pulmonary artery was first transected approximately 3 mm distal to the tops of the commissures, and the pulmonary valve was inspected to confirm the echocardiographic findings. If the valve was trileaflet and appeared normal, it was harvested with a larger than usual cuff of infundibular free-wall muscle (up to 2.5 cm instead of the usual 1 cm). Subsequently, if this was not done before, the aorta was cross-clamped, cardioplegic solution was administered into the aortic root, and an aortotomy was made. Large buttons of aortic sinus tissue were developed around the left and right coronary ostia to eliminate as much as possible pulmonary artery tissue as a support structure for the autograft valve leaflets. The aortic valve leaflets were then completely resected along with any remaining aortic tissue. To gain access to the left ventricle, we incised the ventricular septum to the left of the right coronary ostium in a fashion similar to that used in the Konno procedure. Depending on the size of the pulmonary autograft relative to that of the aortic annulus and the absence or presence of tunnel subaortic stenosis, the incision into the ventricular septum was limited or extended, respectively. The EFE was then resected by sharp and blunt dissection from the base to the apex of the heart, sparing the areas immediately adjacent to the papillary muscles. Hypertrophied myocardium also was resected along the septum and left ventricular free wall. Utmost care was taken not to damage the conduction system, which is located to the right of the right coronary ostium. After having achieved an adequate enlargement of the left ventricular cavity, we sewed the pulmonary autograft to the left ventricular outflow tract with running 6-0 polyglyconate suture (Maxon; Davis & Geck, Inc, Danbury, CT) in a continuous fashion, using the cuff of infundibular muscle to close the ventricular septal incision. Small felt pledgets were used to achieve solid anchoring of the infundibular muscle to the ventricular septal muscle. The left and right sinuses of the pulmonary autograft were completely resected except for a 2-mm rim of tissue along the leaflet insertion. Both coronary buttons were then implanted with 7-0 Maxon suture.
The distal edge of the pulmonary autograft was sewn end-to-end to the ascending aorta. In case of a size discrepancy between the pulmonary autograft and the ascending aorta, the size of the ascending aorta was adapted to that of the pulmonary autograft. Air was removed from the heart, the aortic cross-clamp was removed, and rewarming of the patient was initiated. Finally, the right ventricular outflow tract was reconstructed with a pulmonary homograft using 6-0 polypropylene suture (Prolene; Ethicon, Inc, Somerville, NJ) in a continuous fashion.
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Results
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At operation, the aortic valve was confirmed to be bicuspid and severely dysmorphic in all patients. In the 1 patient who had undergone balloon valvuloplasty, the noncoronary aortic cusp was torn. The EFE had a median thickness of 3 mm (range, 1 to 4 mm). In all patients, a Ross-Konno operation was combined with resection of EFE and of hypertrophied myocardium. The length of the septal incision varied from 1.1 to 2.5 cm. In the 1 patient with mitral regurgitation, an additional mitral valvuloplasty was performed. In the 1 patient with Shone's syndrome, the associated coarctation was resected, and the descending aorta was anastomosed to the underside of the proximal aortic arch.
In all patients, intraoperative echocardiography showed excellent neo-aortic valve function and markedly reduced width of the ventricular septum and left ventricular free wall, with an almost twofold increase of left ventricular volume (Fig 2; see Table 1
). Three patients had mild and 1 had moderate left ventricular dysfunction; the latter patient had mild to moderate residual mitral regurgitation.
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Fig 2. . Postoperative echocardiogram (apical 4-chamber view) after extensive resection of endocardial fibroelastosis and subendocardial myocardium, demonstrating enlarged left ventricular cavity (lv) in diastole (A) and systole (B). Note that the apex is formed by the right ventricle (rv).
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Three patients survived. The left ventricular diastolic and systolic dysfunction in these patients gradually resolved, as evidenced by a decrease of the median left atrial pressure from 14 to 8 mm Hg and an increase of the median systolic blood pressure from 60 to 68 mm Hg on the first and fifth postoperative days, respectively. Inotropic support was gradually weaned after a median of 8 days. One patient had a temporary complete atrioventricular block, which resolved after 5 days. The 3 surviving patients were discharged after 18, 21, and 29 days.
The patient with additional mitral regurgitation died on the sixth postoperative day. Despite continuous inotropic support, the left ventricular function gradually failed, with a resulting increase in mitral regurgitation. At autopsy, a well-functioning neo-aortic valve was seen, with absence of LVOT obstruction, an intact reconstruction of the ventricular septum, and a relatively normal width of the left ventricular septum and free wall; around and in the base of the posteromedial papillary muscle, there were retained areas of EFE (Fig 3).
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Fig 3. . Marked endocardial fibroelastosis (arrows) at the base of the posteromedial papillary muscle. (Elastine-trichrome stain; x350 before 37% reduction.)
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Follow-up in the 3 surviving patients lasted 9, 10, and 12 months. Echocardiography demonstrated excellent function of the neo-aortic valve in all patients and mild regurgitation of the pulmonary homograft in 1 patient; left ventricular function was excellent in 2 patients and mildly depressed in 1.
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Comment
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Critical aortic stenosis with concentric left ventricular hypertrophy is characterized by rapidly progressive congestive heart failure and is almost always fatal if not relieved early [1–3]. Endocardial fibroelastosis, a response to chronic prenatal myocardial stress, is almost uniformly present in this setting [4, 5]. The degree of development of EFE generally depends on the severity and duration of the LVOT obstruction in utero and shows a spectrum from barely discernible, microscopic thickening to the globular heart with pearly-white endocardium [6–8]. Fibroelastosis is associated with decreased systolic function and passive diastolic properties. The primary mechanism of the impairment of systolic performance may consist of a disruption of the nutrient microcirculation to the subendocardium and mechanical impairment of the myocardium from compression by the meshwork of collagen fibers [9, 10].
The spectrum of LVOT obstruction includes isolated valvar aortic stenosis at one end and hypoplastic left heart syndrome at the other. The concept of concurrent, multiple left-sided lesions with regard to LVOT obstruction is important in neonates and infants. The classic description by Shone and associates, [11] consisting of supramitral ring, single left ventricular papillary muscle, subaortic membrane, and coarctation, underscores this concept. The adverse effects of small inflow, outflow, and cavity size are cumulative. Whether to consider the patients as having the hypoplastic left heart syndrome, requiring staged palliation for single-ventricle physiology, or as having multiple left-sided, obstructive lesions but being capable of achieving a two-ventricle physiology, often is a complex decision. Traditionally, management of complex LVOT obstruction with borderline-sized left ventricle has been associated with a high mortality rate [1, 2, 12, 13]. Several studies have focused on establishing predictive factors associated with successful biventricular repair in patients with complex LVOT obstruction. Parsons and colleagues [14] reported that among infants younger than 3 months who underwent aortic valvotomy, survivors had a larger aortic annulus (10.1 ± 1.7 mm) than did nonsurvivors (7.7 ± 1.5 mm). Left ventricular end-diastolic dimensions were 18.4 ± 1.7 mm in survivors, versus 11.3 ± 3.0 mm in nonsurvivors. Additional volume data showed a left ventricular end-diastolic volume index of 43 ± 23 cm3/m2 in survivors, versus 11 ± 5 cm3/m2 in nonsurvivors. Rhodes and associates [12] used discriminant analysis to predict outcome after a biventricular repair, with 95% accuracy based on mitral valve area (
4.75 cm2/m2), long-axis dimension of the left ventricle relative to the long-axis dimension of the heart (0.8), diameter of the aortic root (3.5 cm/m2), and left ventricular mass (35 gm/m2).
In addition to morphometric data, clinical decision making in terms of biventricular versus univentricular repair is based on physiologic data. In this perspective, it is critical to separate neonates who are likely to change successfully from the transient stage of fetal (parallel) circulation to the postnatal (in-series) circulation versus those in whom this transition will likely result in increasing left ventricular failure. Monitoring of oxygen saturation in both the upper and lower extremities in combination with echocardiographic Doppler flow mapping of physiology at the level of the ascending aorta, aortic arch, and ductus arteriosus provide important information for logical decision making. In the presence of antegrade flow in the ascending aorta and aortic arch and left-to-right ductal flow or an obliterated ductus arteriosus, with the oxygen saturation in the upper and lower extremities matched at 100%, biventricular repair generally can be accomplished safely. In contrast, when there is retrograde flow in the ascending aorta in the presence of right-to-left ductal flow with oxygen saturation in the upper and lower extremities matched at the 85% to 90% level, univentricular repair according to Norwood is generally indicated because the left ventricle in all likelihood is incapable of delivering efficient antegrade cardiac output. In situations of documented antegrade flow in the ascending aorta with ductal flow being right-to-left or bidirectional, and with a differential oxygen saturation between the upper extremities (approximating 100%) and the lower extremities (lower than 90%), decision making is complex. In this situation, cardiac catheterization may supplement important physiologic data. A left ventricular intracavitary pressure well in excess of the aortic pressure attests to the adequacy of left ventricular systolic function and demonstrates the potential for adequate antegrade flow, thus making a biventricular repair potentially feasible. Equivalent left ventricular and aortic pressures, on the other hand, demonstrate the impossibility of viable antegrade flow, thus setting the stage for univentricular repair. Postnatally, the degrees of left ventricular hypertrophy and of EFE tend to correlate poorly with the severity of the LVOT obstruction and have little prognostic value. Unfortunately, neither echocardiography nor cardiac catheterization can accurately predict the ultimate potential for postoperative recovery of left ventricular diastolic function.
In an attempt to improve the dismal natural history of critical aortic stenosis with left ventricular hypertrophy and EFE, we have combined relief of the LVOT obstruction by means of a Ross-Konno operation with extensive resection of the EFE and the hypertrophied left ventricular septum and free wall, thus avoiding univentricular repair or heart transplantation. Potential advantages of this approach, besides relief of LVOT obstruction and creation of normal aortic valve function, are enlargement of left ventricular stroke volume, improvement of left ventricular diastolic function, and creation of the potential for left ventricular growth. In 3 patients in this series, who all had borderline-sized left ventricular volumes and inflow and outflow dimensions [12, 14], the operation resulted in a dramatic increase in left ventricular volume with early normalization of left ventricular dynamics. The reported technique is not recommended in the presence of moderate or severe mitral regurgitation secondary to extensive EFE involvement of one or both papillary muscles; the 1 patient in our series who died had associated mitral regurgitation. In this setting, besides cardiac transplantation, univentricular palliation according to Norwood's principle may be the only viable option.
Even more so than in septal myectomy for subaortic stenosis [15], extensive endocardial and myocardial resection through a transaortic approach presents special problems in neonates and infants because of limited exposure through the often hypoplastic aortic annulus; the inherent risk of injury of the conduction tissue, the aortic and mitral valves, the papillary muscles, and major coronary artery branches; and the potential for creation of an iatrogenic ventricular septal defect. In this setting, incision of the ventricular septum greatly facilitates exposure of the left ventricular cavity. Closure of the incision in the ventricular septum with a cuff of infundibular muscle that is adherent to the pulmonary autograft is a relatively easy technique and renders reconstruction of the septum with a prosthetic patch, with its inherent disadvantages, unnecessary [16, 17]. A second advantage of this technique is that enlargement of the aortic root accommodates the pulmonary autograft, the size of which often is considerably larger than that of the aorta.
The postoperative course of patients who undergo extensive concentric resection of the left ventricular myocardium, as presented here, is characterized by temporary impairment of left ventricular systolic function, with a decrease in pumping capacity and severance of subendocardially coursing coronary arterial vessels, resulting in high coronary runoff during diastole. Because of this and the chronically impaired left ventricular diastolic function, adequate preloading of the left ventricle (with a left atrial pressure as high as 14 to 16 mm Hg) and prolonged support with inotropic drugs are indicated. In our experience, synchronous with improvement of left ventricular systolic and diastolic function, the inotropic drugs can be slowly weaned, usually after a period of approximately 7 days.
In the embryo and fetus, the left ventricle grows by increasing its number of myocytes (hyperplasia). Although it is not definitely proved in the human, myocyte mitotic activity and the potential for myocyte hyperplasia allegedly persist for 3 to 6 months after birth, after which all myocytes become terminally differentiated cells [18, 19]. In the neonate, pressure and volume overload induce mostly hyperplasia of myocytes and coronary angiogenesis [18, 19]. In light of this, there is a potential for restoration of near-normal left ventricular function and coronary angiogenesis during the early hyperplastic phase of cardiac growth.
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Footnotes
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Address reprint requests to Dr van Son, Herzzentrum, University of Leipzig, Russenstrasse 19, D-04289, Leipzig, Germany.
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Abstract
Introduction
