To describe a series of fetuses diagnosed as having Shone's syndrome, which includes four cardiac defects and for which there is a wide variety of clinical presentations, surgical treatments and outcomes, and to discuss the counseling strategy.
We reviewed retrospectively the records of four babies who were suspected prenatally to have Shone's syndrome.
The mean age at diagnosis was 27.5 (range, 22–35) weeks. A small left ventricle, mitral and aortic annulus and ascending aorta were detected in three cases. In three fetuses there was an abnormal mitral valve apparatus and in two fetuses a sub-aortic membrane was detected. Coarctation of the aorta was an impending diagnosis in three babies. Following counseling, all parents decided to continue the pregnancy to term. Echocardiographic evaluation was performed soon after birth. The mean mitral valve annulus diameter was 8.2 (range, 7–10) mm, and that of the aortic valve annulus was 6 (range, 5–7) mm. The aortic valve was bicuspid in all babies with an additional sub-aortic membrane in two babies. Doppler ultrasound examination revealed high-velocity flow through the mitral valve in three babies; two of them had a parachute mitral valve. Coarctation repair was performed in two babies during the first week of life. One patient underwent mitral valvuloplasty followed by later mitral valve replacement. All patients were alive after a mean of 7.8 (range, 3.3–10.5) years' follow-up.
Shone's syndrome consists of four defects: a supravalve mitral membrane, parachute mitral valve, subaortic stenosis (membranous or muscular) and coarctation of the aorta1. An incomplete form has been described when only two or three of the components are recognized. Patients with Shone's syndrome have been described as having an unsatisfactory operative outcome with a mortality rate of 24–27%, they require multiple interventions, and have poor long-term prognosis2–4. Fewer than 50 cases of Shone's syndrome have been reported in the literature and most of them focus on postnatal surgical outcome, with few data published on the outcome of prenatal diagnosis. In this study, we describe our experience with four consecutive cases of Shone's syndrome diagnosed prenatally and discuss the dilemma of family counseling in this relatively rare condition.
Fetal echocardiograms of patients diagnosed as having Shone's syndrome in our center during a 10-year study period (1993–2003) were retrospectively reviewed and analyzed. Postnatal echocardiographic data as well as clinical data, X-rays, medical and surgical treatment and follow-up reports were evaluated.
All measurements were obtained using the standard two-dimensional ultrasound technique (with a HP Sonos 5500 (Hewlett-Packard, Andover, MA, USA) ultrasound machine) at a time corresponding to end-diastole. Left heart measurement was obtained from the four-chamber view. Ventricular dimensions were measured immediately below the opposed tips of the atrioventricular leaflets, and ventricular lengths were measured at the same position from the apex of the left ventricle to the point where the valve leaflets met. The aortic annulus diameter was measured in a long-axis view at the valve level, that of the ascending aorta was measured immediately above the sinus of Valsalva, and that of the aortic isthmus was measured immediately above the entrance of the ductus arteriosus. All measurements were compared with normal cardiac dimension values for the appropriate gestational age5.
Following prenatal echocardiographic findings, parents were counseled about the wide range and uncertainty of the possible outcomes of their baby's cardiac condition, the possible development of multisite obstruction within the left side of the heart, and the difficulty to accurately predict the likely surgical course and outcome.
During the 10-year study period (1993–2003), 12 520 fetal echocardiographic examinations were performed in our center. One hundred and eighty-nine (1.5%) cases of congenital heart disease were identified. Four fetuses were suspected of having ultrasound characteristics corresponding with Shone's syndrome. The cause for referral was unusual cardiac findings on a routine obstetric ultrasound scan. The mean age at ultrasound examination was 27.5 (range, 22–35) weeks' gestation.
In all four cases, cardiothoracic ratios were within the normal range6. All four patients had small left ventricular dimensions (< 5th percentile), a small aortic annulus (< 5th percentile), and two patients had a small aortic isthmus (< 5th percentile) (Figure 1). The mitral valve apparatus appeared abnormal in three of the four fetuses, with thickened leaflets and a narrowed orifice. Normal flow velocity was detected by Doppler interrogation across the mitral valve in all four fetuses. It was impossible to determine the anatomy of the papillary muscles. A sub-aortic membrane was detected in two of the four fetuses and flow velocity was normal across the left ventricular outflow tract in all four cases.
All parents chose to proceed with the pregnancy. All babies were born at term and the diagnosis of Shone's syndrome was confirmed by an echocardiogram (Table 1). A small left ventricle was found in all babies. The mean mitral valve annulus diameter was 8.2 (range, 7–10) mm, which corresponds to a Z-score of −0.665 on the basis of the normal range for newborns (10 ± 2.6 mm)7. The mean diameter of the aortic annulus was 6 (range, 5–7) mm which corresponds to a Z-score of −2.833 on the basis of the normal range in newborns (7.7 ± 0.6 mm)8. A bicuspid aortic valve was detected in all four babies. In two babies there was an additional sub-aortic membrane. Doppler interrogation revealed high-velocity blood flow through the mitral valve in three babies (mean gradient > 8 mmHg). Two of these had a parachute mitral valve, and one had an additional supravalve mitral membrane. A small aortic arch was noted in all four babies. Additional diagnoses included: an interrupted inferior vena cava with hemiazygous continuation in one patient, and a small muscular ventricular septal defect in another. Two babies developed symptoms during the first week of life due to coarctation of the aorta and underwent coarctation repair. A third patient underwent coarctation repair later in life. The fourth patient, at the time of writing, had mild coarctation and was being followed clinically. One patient developed severe left ventricular inlet obstruction and underwent mitral valvoplasty followed by later mitral valve replacement. One patient underwent resection of left ventricular outflow obstruction. All patients were alive after a mean follow-up of 7.8 (range, 3.3–10.5) years (Table 1).
MV annulus diameter: 7 mm, MS: mild, AoV annulus diameter: 5 mm, bicuspid AoV, sub-aortic membrane, small aorta, interrupted IVC
Coarctation repair at 8 years, subaortic membrane resection at 8.3 years
MV annulus diameter: 9 mm, parachute mitral valve, MS: mild, AoV annulus diameter: 7 mm, bicuspid AoV, small aorta
MV annulus diameter: 7 mm, supramitral ring, parachute mitral valve, MS: mild, AoV annulus diameter: 5 mm, bicuspid AoV, coarctation of aorta
3 weeks, 15 months, 24 months
Coarctation repair at 1 month, mitral valvuloplasty at 1.5 years, mitral valve replacement at 3 years
MV annulus diameter: 10 mm, AoV annulus diameter: 7 mm, bicuspid AoV, sub-aortic membrane, ventricular septal defect, coarctation of aorta
Coarctation repair at 1 week
Shone's syndrome is a complex cardiac anomaly originating as maldevelopment of left ventricular inflow. Mitral valve obstruction during early embryogenesis is considered to be the basic pathological event, followed by underdevelopment of the left ventricular cavity, leading to various degrees of left ventricular outflow obstruction and eventually coarctation of the aorta. Shone et al.1 noted that mitral valve obstruction appeared to be the most critical problem associated with the anomaly. Other studies confirmed the belief that severity of the mitral valve obstruction correlates inversely with long-term outcome, and that operative mortality in patients with Shone's anomaly is adversely affected by the degree of mitral valve disease. The patients who demonstrated substantially elevated pulmonary artery pressures were those with the worst mitral obstruction and had the poorest prognosis1–4, 9. Diagnosis of Shone's syndrome by fetal echocardiography at mid-gestation may be misleading, taking into consideration the fact that the fetal heart is still actively growing and developing. The cavity size of the left ventricle, degree of left ventricular inflow and outflow obstruction and possible narrowing of the aortic arch and eventually coarctation, are pending at this stage; both steady state and worsening by the end point are possible. It is understood that the degree of maldevelopment of various left heart segments will eventually influence and determine clinical presentation at birth, need for medical intervention, morbidity and mortality. Obviously, this information is crucial for the physician who consults the parents.
We have described a group of four fetuses that had been diagnosed during pregnancy as potentially having Shone's syndrome, based on abnormal fetal echocardiographic findings. These findings included small dimensions of the left ventricle, aortic root and mitral and aortic valve annuli. All measurements were compared with normal cardiac dimensions for the appropriate gestational age5. All valves were patent, with normal flow pattern across the inflow and outflow of the left ventricle. The mitral valve apparatus was abnormal in three of the four fetuses. Normal left ventricular function had been detected in all four cases with normal myocardial appearance. The diagnosis of left hypoplastic heart was excluded based on the echocardiographic findings. The diagnosis of Shone's syndrome was confirmed on the basis of postnatal echocardiography10–12.
In the original article written by Shone et al., only two (of eight) patients exhibited all four aspects of the anomaly. None of our patients exhibited all four aspects, but all patients exhibited two or three aspects of the anomaly. The patient outcome in our series was widely variable: one patient required no intervention, one needed an intervention of moderate risk as an infant, one needed two interventions in later childhood, and one, after two previous interventions, required mitral valve replacement, which is a major intervention for a child. It is apparent that the diversity and complex nature of cardiac anomalies in babies with Shone's syndrome and the high surgical risk makes prenatal counseling extremely difficult. It is hard to prognosticate accurately when counseling parents and only postnatal echocardiography and long-lasting clinical and echocardiographic follow-up eventually determine the correct nature of this lesion.