Cardiology in the Young (2015), 25, 1002–1005
© Cambridge University Press, 2014
doi:10.1017/S1047951114001334
Brief Report Unguarded mitral orifice associated with hypoplastic left heart syndrome Jennifer A. Su,1,2 John Ho,1,2 Pierre C. Wong1,2 1
Division of Cardiology, Children’s Hospital Los Angeles, California, United States of America; 2Department of Pediatrics, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America Abstract In the spectrum of mitral valve anomalies, unguarded mitral orifice is an exceedingly rare malformation, with only four cases described in the current literature. All previously reported cases have been associated with discordant atrioventricular connections. We describe the first known case of unguarded mitral valve orifice, in the setting of atrioventricular concordance, in a newborn with hypoplastic left heart syndrome. Keywords: Unguarded mitral orifice; hypoplastic left heart syndrome; CHD Received: 27 May 2014; Accepted: 29 June 2014; First published online: 24 July 2014
C
ONGENITAL ANOMALIES OF THE MITRAL VALVE ARE
rare, and may result in both mitral stenosis and regurgitation. Congenital mitral stenosis occurs in ∼1.2% of patients with CHD, and 0.42% of all cardiac patients.1 Malformations resulting in mitral regurgitation are even more unusual.2 One rare but fascinating anomaly resulting in mitral regurgitation is Ebstein’s malformation of the mitral valve, first described by Ruschhaupt in 1976.3,4 This anomaly has a highly variable morphology, with an unguarded mitral valve orifice – in which the mitral valve fails to form altogether – speculated to be its most severe form.5 Only four cases of unguarded mitral orifice have been described to date, all of which have been associated with atrioventricular discordance.6–8 We report the first known case of unguarded mitral valve orifice, in the setting of atrioventricular concordance, in a newborn with hypoplastic left heart syndrome.
Case report A 37-week-newborn boy was transferred to our hospital for the management of hypoplastic left heart Correspondence to: J. A. Su, MD, Division of Cardiology, Children’s Hospital Los Angeles, 4650 W. Sunset Boulevard, Mailstop #34 Los Angeles, CA 90027, United States of America. Tel: 323 361 8308; Fax: 323 361 1513; E-mail: [email protected]
syndrome and small bowel obstruction. His mother had received comprehensive prenatal care, and the congenital heart defect had been diagnosed prenatally. At birth, the patient was appropriate for gestational age, weighing 2550 g. He was vigorous and maintained oxygen saturations between 80 and 95% on room air. A radiograph of the chest and abdomen revealed a left-sided cardiac apex, mild cardiomegaly, moderate pulmonary vascular congestion, abdominal situs solitus, and severely dilated loops of bowel. A prostaglandin E1 infusion was started, and his postnatal echocardiogram confirmed the diagnosis of hypoplastic left heart syndrome. His cardiac segments were {S, D, S}, with a normal right atrium and a left atrium with restrictive leftto-right atrial shunting through a patent foramen ovale. The tricuspid valve was normal and the right ventricle had qualitatively normal systolic function. The pulmonary valve was large with no insufficiency or stenosis. There was no evidence of pulmonary venous stenosis. There was an unguarded mitral valve orifice with virtually absent mitral valve leaflets (Figs 1a and 2). The left ventricular chamber was hypoplastic, but with a bulging cavity and thin, hyperechoic ventricular walls, suggesting possible endocardial fibroelastosis. No identifiable valve chordae or papillary muscles were visualised. The aortic valve, which clearly arose from the left ventricle, was formed
Vol. 25, No. 5
Su et al: Unguarded mitral orifice in HLHS
1003
Figure 1. Transthoracic apical four-chamber views. (a) Hypoplastic left heart syndrome status post emergent atrial septostomy, with an unguarded mitral orifice (seen as muscular ridges) between the left atrium (LA) and left ventricle (LV). No visible mitral valve leaflet or chordal tissue is seen. The left ventricle is thin walled, hypoplastic, and hyperechoic. (b) Slight anterior probe angulation displays the ascending aorta (Ao) arising from the LV. The formed but imperforate aortic valve (arrow) can be seen between the LV and Ao. (c) Diastolic frame demonstrating free retrograde flow through the mitral valve orifice into the LA. (d) Late systolic frame demonstrating antegrade blood flow into the LV. RA = right atrium; RV = right ventricle.
Figure 2. Three-dimensional echocardiographic images. (a) Cropped view from the superior aspect of the atria, showing en face views of the mitral orifice (MO) and tricuspid valve (TV). No visible mitral leaflets are seen. (b) Apical four-chamber view showing the cardiac chambers and the unguarded mitral orifice (asterisks). LA = left atrium; LV = left ventricle; RA = right atrium; RV = right ventricle.
but imperforate (Fig 1b). By Doppler interrogation, low-velocity to-and-fro flow was observed between the left atrium and left ventricle. Interestingly, left
ventricular filling occurred during systole, suggesting complete absence of left-sided myocardial contraction (Fig 1c), and retrograde flow from the left
1004
Cardiology in the Young
ventricle to the left atrium occurred during late diastole (Fig 1d). On physical examination, the patient was alert, mildly cyanotic, with no obvious dysmorphic features. His precordium was active with a nondisplaced ventricular impulse. Upon auscultation, there was a single S1 and S2, and a grade 2/6 systolic ejection murmur heard along the left upper sternal border with radiation to bilateral axillae. Lung fields were clear and he had a normal respiratory effort. Abdominal examination revealed a non-distended and soft abdomen with decreased bowel sounds, and a liver edge at 2 cm below the right costal margin. Peripheral pulses were 2+ in all extremities. The patient underwent an emergent atrial septectomy and bilateral pulmonary artery banding to control pulmonary blood flow on day 1 of life. The next day, he underwent an exploratory laparotomy and was found to have jejunal atresia, necessitating small bowel resection and jejunostomy. On day 5 of life, the patient returned to the operating room and underwent a Norwood procedure with placement of a 5 mm right ventricle to pulmonary artery (Sano) shunt. A transoesophageal echocardiogram performed during surgery confirmed the complete absence of identifiable mitral valve tissue. Cardiac surgery was performed without complications, and the patient returned to the cardiothoracic ICU for continued medical management. His subsequent course was uneventful.
Discussion Unguarded mitral orifice is an exceedingly rare malformation in which the mitral valve is completely absent, leading to unobstructed to-and-fro flow between the corresponding atrial and ventricular chambers. Previous cases of unguarded mitral orifice have been associated with heterotaxy syndrome including mirror-image atrial arrangements, atrioventricular discordance, and double-outlet right ventricle.6–8 This case is unique in that our patient has normal segmental anatomy, indicating that this anomaly does not necessarily involve disturbance of the left–right axis during embryologic development. Moreover, our case is distinct in that the patient carried the diagnosis of hypoplastic left heart syndrome. Mitral valve development occurs during the 4th and 5th weeks of gestation as a result of leaflet delamination from the left ventricular endomyocardial surface. Interference of this process, either by maldevelopment of the mesenchymal tissue or cardiomyocyte apoptosis, has been speculated to result in an unguarded mitral orifice.6 Such disturbances may also affect myocardial development, resulting in
June 2015
an abnormally thinned ventricular wall. This appears to have been the case with our patient – in addition to unguarded mitral orifice leading to unobstructed to-and-fro flow between the left atrium and ventricle, the patient’s left ventricular cavity was thin-walled and essentially akinetic. It has previously been suggested that unguarded mitral orifice may represent an extreme form of Ebstein’s anomaly of the mitral valve, although the latter is characterised by failure of delamination of the mural leaflet of mitral valve, with the septal leaflet generally formed and attached normally.5,9 The two anomalies appear to have common features, and may indeed represent a particular spectrum of mitral valve disease. Notably, Ebstein’s malformation of the mitral valve has been associated with aortic obstruction, and unguarded mitral orifice appears to be associated with complete atresia of the corresponding outflow tract.6–8,10 In our case, one can cautiously speculate that unguarded mitral orifice, in conjunction with the underlying left ventricular myocardial abnormality, might have led to aortic atresia and evolution of hypoplastic left heart syndrome. In conclusion, unguarded mitral orifice is a rare and intriguing anomaly that has been previously described in association with heterotaxy and atrioventricular discordance. In this report, we describe a case of a patient with unguarded mitral orifice and normal segmental anatomy. Furthermore, our case represents the first documented occurrence of this very rare anomaly in association with hypoplastic left heart syndrome.
Acknowledgement None. Financial Support This research received no specific grant from any funding agency, commercial, or not-for-profit sectors. Conflicts of Interest None. Supplementary material To view supplementary material for this article, please visit http://dx.doi.org/10.1017/S1047951114001334
References 1. Collins-Nakai RL, Rosenthal A, Castaneda AR, Bernhard WF, Nadas AS. Congenital mitral stenosis. A review of 20 years’ experience. Circulation 1977; 56: 1039–1047. 2. Séguéla PE, Houyel L, Acar P. Congenital malformations of the mitral valve. Arch Cardiovasc Dis 2011; 104: 465–479.
Vol. 25, No. 5
Su et al: Unguarded mitral orifice in HLHS
3. Ruschhaupt DG, Bharati S, Lev M. Mitral valve malformation of Ebstein type in absence of corrected transposition. Am J Cardiol 1976; 38: 109–112. 4. Jacob JL, da Silveira LC, Braile DM. Echocardiographic and angiographic diagnosis of Ebstein’s anomaly of the mitral valve. Br Heart J 1991; 66: 379–380. 5. Anderson KR, Zuberbuhler JR, Anderson RH, Becker AE, Lie JT. Morphologic spectrum of Ebstein’s anomaly of the heart: a review. Mayo Clin Proc 1979; 54: 174–180. 6. Yasukochi S, Satomi G, Park I, Ando M, Momma K. Unguarded mitral orifice, mirror-imaged atrial arrangement, and discordant atrioventricular connections. Cardiol Young 1999; 9: 478–483.
1005
7. Earing MG, Edwards WD, Puga FJ, Cabalka AK. Unguarded mitral orifice associated with discordant atrioventricular connection, double-outlet right ventricle, and pulmonary atresia. Pediatr Cardiol 2003; 24: 490–492. 8. Hwang MS, Chang YS, Chu JJ, Lin WS, Su WJ. A potential new constellation of defects: unguarded mitral orifice associated with double-outlet right ventricle {I, D, D} and pulmonary atresia/stenosis. Int J Cardiol 2011; 148: 354–357. 9. Cuadra AP, Muñoz-Castellanos L, Espinola-Zavaleta N. Isolated Ebstein's anomaly of mitral valve in an adult patient with systemic lupus erythematosus. Congenit Heart Dis 2010; 5: 641–644. 10. Erickson LC, Cocalis MW. Ebstein’s malformation of the mitral valve: association with aortic obstruction. Pediatr Cardiol 1995; 16: 45–47.
Copyright of Cardiology in the Young is the property of Cambridge University Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
© Cambridge University Press, 2014
doi:10.1017/S1047951114001334
Brief Report Unguarded mitral orifice associated with hypoplastic left heart syndrome Jennifer A. Su,1,2 John Ho,1,2 Pierre C. Wong1,2 1
Division of Cardiology, Children’s Hospital Los Angeles, California, United States of America; 2Department of Pediatrics, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America Abstract In the spectrum of mitral valve anomalies, unguarded mitral orifice is an exceedingly rare malformation, with only four cases described in the current literature. All previously reported cases have been associated with discordant atrioventricular connections. We describe the first known case of unguarded mitral valve orifice, in the setting of atrioventricular concordance, in a newborn with hypoplastic left heart syndrome. Keywords: Unguarded mitral orifice; hypoplastic left heart syndrome; CHD Received: 27 May 2014; Accepted: 29 June 2014; First published online: 24 July 2014
C
ONGENITAL ANOMALIES OF THE MITRAL VALVE ARE
rare, and may result in both mitral stenosis and regurgitation. Congenital mitral stenosis occurs in ∼1.2% of patients with CHD, and 0.42% of all cardiac patients.1 Malformations resulting in mitral regurgitation are even more unusual.2 One rare but fascinating anomaly resulting in mitral regurgitation is Ebstein’s malformation of the mitral valve, first described by Ruschhaupt in 1976.3,4 This anomaly has a highly variable morphology, with an unguarded mitral valve orifice – in which the mitral valve fails to form altogether – speculated to be its most severe form.5 Only four cases of unguarded mitral orifice have been described to date, all of which have been associated with atrioventricular discordance.6–8 We report the first known case of unguarded mitral valve orifice, in the setting of atrioventricular concordance, in a newborn with hypoplastic left heart syndrome.
Case report A 37-week-newborn boy was transferred to our hospital for the management of hypoplastic left heart Correspondence to: J. A. Su, MD, Division of Cardiology, Children’s Hospital Los Angeles, 4650 W. Sunset Boulevard, Mailstop #34 Los Angeles, CA 90027, United States of America. Tel: 323 361 8308; Fax: 323 361 1513; E-mail: [email protected]
syndrome and small bowel obstruction. His mother had received comprehensive prenatal care, and the congenital heart defect had been diagnosed prenatally. At birth, the patient was appropriate for gestational age, weighing 2550 g. He was vigorous and maintained oxygen saturations between 80 and 95% on room air. A radiograph of the chest and abdomen revealed a left-sided cardiac apex, mild cardiomegaly, moderate pulmonary vascular congestion, abdominal situs solitus, and severely dilated loops of bowel. A prostaglandin E1 infusion was started, and his postnatal echocardiogram confirmed the diagnosis of hypoplastic left heart syndrome. His cardiac segments were {S, D, S}, with a normal right atrium and a left atrium with restrictive leftto-right atrial shunting through a patent foramen ovale. The tricuspid valve was normal and the right ventricle had qualitatively normal systolic function. The pulmonary valve was large with no insufficiency or stenosis. There was no evidence of pulmonary venous stenosis. There was an unguarded mitral valve orifice with virtually absent mitral valve leaflets (Figs 1a and 2). The left ventricular chamber was hypoplastic, but with a bulging cavity and thin, hyperechoic ventricular walls, suggesting possible endocardial fibroelastosis. No identifiable valve chordae or papillary muscles were visualised. The aortic valve, which clearly arose from the left ventricle, was formed
Vol. 25, No. 5
Su et al: Unguarded mitral orifice in HLHS
1003
Figure 1. Transthoracic apical four-chamber views. (a) Hypoplastic left heart syndrome status post emergent atrial septostomy, with an unguarded mitral orifice (seen as muscular ridges) between the left atrium (LA) and left ventricle (LV). No visible mitral valve leaflet or chordal tissue is seen. The left ventricle is thin walled, hypoplastic, and hyperechoic. (b) Slight anterior probe angulation displays the ascending aorta (Ao) arising from the LV. The formed but imperforate aortic valve (arrow) can be seen between the LV and Ao. (c) Diastolic frame demonstrating free retrograde flow through the mitral valve orifice into the LA. (d) Late systolic frame demonstrating antegrade blood flow into the LV. RA = right atrium; RV = right ventricle.
Figure 2. Three-dimensional echocardiographic images. (a) Cropped view from the superior aspect of the atria, showing en face views of the mitral orifice (MO) and tricuspid valve (TV). No visible mitral leaflets are seen. (b) Apical four-chamber view showing the cardiac chambers and the unguarded mitral orifice (asterisks). LA = left atrium; LV = left ventricle; RA = right atrium; RV = right ventricle.
but imperforate (Fig 1b). By Doppler interrogation, low-velocity to-and-fro flow was observed between the left atrium and left ventricle. Interestingly, left
ventricular filling occurred during systole, suggesting complete absence of left-sided myocardial contraction (Fig 1c), and retrograde flow from the left
1004
Cardiology in the Young
ventricle to the left atrium occurred during late diastole (Fig 1d). On physical examination, the patient was alert, mildly cyanotic, with no obvious dysmorphic features. His precordium was active with a nondisplaced ventricular impulse. Upon auscultation, there was a single S1 and S2, and a grade 2/6 systolic ejection murmur heard along the left upper sternal border with radiation to bilateral axillae. Lung fields were clear and he had a normal respiratory effort. Abdominal examination revealed a non-distended and soft abdomen with decreased bowel sounds, and a liver edge at 2 cm below the right costal margin. Peripheral pulses were 2+ in all extremities. The patient underwent an emergent atrial septectomy and bilateral pulmonary artery banding to control pulmonary blood flow on day 1 of life. The next day, he underwent an exploratory laparotomy and was found to have jejunal atresia, necessitating small bowel resection and jejunostomy. On day 5 of life, the patient returned to the operating room and underwent a Norwood procedure with placement of a 5 mm right ventricle to pulmonary artery (Sano) shunt. A transoesophageal echocardiogram performed during surgery confirmed the complete absence of identifiable mitral valve tissue. Cardiac surgery was performed without complications, and the patient returned to the cardiothoracic ICU for continued medical management. His subsequent course was uneventful.
Discussion Unguarded mitral orifice is an exceedingly rare malformation in which the mitral valve is completely absent, leading to unobstructed to-and-fro flow between the corresponding atrial and ventricular chambers. Previous cases of unguarded mitral orifice have been associated with heterotaxy syndrome including mirror-image atrial arrangements, atrioventricular discordance, and double-outlet right ventricle.6–8 This case is unique in that our patient has normal segmental anatomy, indicating that this anomaly does not necessarily involve disturbance of the left–right axis during embryologic development. Moreover, our case is distinct in that the patient carried the diagnosis of hypoplastic left heart syndrome. Mitral valve development occurs during the 4th and 5th weeks of gestation as a result of leaflet delamination from the left ventricular endomyocardial surface. Interference of this process, either by maldevelopment of the mesenchymal tissue or cardiomyocyte apoptosis, has been speculated to result in an unguarded mitral orifice.6 Such disturbances may also affect myocardial development, resulting in
June 2015
an abnormally thinned ventricular wall. This appears to have been the case with our patient – in addition to unguarded mitral orifice leading to unobstructed to-and-fro flow between the left atrium and ventricle, the patient’s left ventricular cavity was thin-walled and essentially akinetic. It has previously been suggested that unguarded mitral orifice may represent an extreme form of Ebstein’s anomaly of the mitral valve, although the latter is characterised by failure of delamination of the mural leaflet of mitral valve, with the septal leaflet generally formed and attached normally.5,9 The two anomalies appear to have common features, and may indeed represent a particular spectrum of mitral valve disease. Notably, Ebstein’s malformation of the mitral valve has been associated with aortic obstruction, and unguarded mitral orifice appears to be associated with complete atresia of the corresponding outflow tract.6–8,10 In our case, one can cautiously speculate that unguarded mitral orifice, in conjunction with the underlying left ventricular myocardial abnormality, might have led to aortic atresia and evolution of hypoplastic left heart syndrome. In conclusion, unguarded mitral orifice is a rare and intriguing anomaly that has been previously described in association with heterotaxy and atrioventricular discordance. In this report, we describe a case of a patient with unguarded mitral orifice and normal segmental anatomy. Furthermore, our case represents the first documented occurrence of this very rare anomaly in association with hypoplastic left heart syndrome.
Acknowledgement None. Financial Support This research received no specific grant from any funding agency, commercial, or not-for-profit sectors. Conflicts of Interest None. Supplementary material To view supplementary material for this article, please visit http://dx.doi.org/10.1017/S1047951114001334
References 1. Collins-Nakai RL, Rosenthal A, Castaneda AR, Bernhard WF, Nadas AS. Congenital mitral stenosis. A review of 20 years’ experience. Circulation 1977; 56: 1039–1047. 2. Séguéla PE, Houyel L, Acar P. Congenital malformations of the mitral valve. Arch Cardiovasc Dis 2011; 104: 465–479.
Vol. 25, No. 5
Su et al: Unguarded mitral orifice in HLHS
3. Ruschhaupt DG, Bharati S, Lev M. Mitral valve malformation of Ebstein type in absence of corrected transposition. Am J Cardiol 1976; 38: 109–112. 4. Jacob JL, da Silveira LC, Braile DM. Echocardiographic and angiographic diagnosis of Ebstein’s anomaly of the mitral valve. Br Heart J 1991; 66: 379–380. 5. Anderson KR, Zuberbuhler JR, Anderson RH, Becker AE, Lie JT. Morphologic spectrum of Ebstein’s anomaly of the heart: a review. Mayo Clin Proc 1979; 54: 174–180. 6. Yasukochi S, Satomi G, Park I, Ando M, Momma K. Unguarded mitral orifice, mirror-imaged atrial arrangement, and discordant atrioventricular connections. Cardiol Young 1999; 9: 478–483.
1005
7. Earing MG, Edwards WD, Puga FJ, Cabalka AK. Unguarded mitral orifice associated with discordant atrioventricular connection, double-outlet right ventricle, and pulmonary atresia. Pediatr Cardiol 2003; 24: 490–492. 8. Hwang MS, Chang YS, Chu JJ, Lin WS, Su WJ. A potential new constellation of defects: unguarded mitral orifice associated with double-outlet right ventricle {I, D, D} and pulmonary atresia/stenosis. Int J Cardiol 2011; 148: 354–357. 9. Cuadra AP, Muñoz-Castellanos L, Espinola-Zavaleta N. Isolated Ebstein's anomaly of mitral valve in an adult patient with systemic lupus erythematosus. Congenit Heart Dis 2010; 5: 641–644. 10. Erickson LC, Cocalis MW. Ebstein’s malformation of the mitral valve: association with aortic obstruction. Pediatr Cardiol 1995; 16: 45–47.
Copyright of Cardiology in the Young is the property of Cambridge University Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.
