Download Accessory Mitral Valve without Left Ventricular Outflow Tract

Special
Report
Accessory Mitral Valve
without Left Ventricular
Outflow Tract Obstruction
in an Adult
Juan Carlos Rozo, MD
Dajhana Medina, MD
Cesar Guerrero, MD
Ana Maria Calderon, MD
Andrés Mesa, MD
Accessory mitral valve is a rare congenital abnormality and an unusual cause of subvalvular obstruction of the left ventricular outflow tract. Accessory mitral valves are usually
detected in children due to symptomatic obstruction; isolated nonobstructive accessory
mitral valve is rarely seen in adults. We describe the echocardiographic diagnosis of accessory mitral valve as an isolated congenital anomaly not associated with a substantial
degree of obstruction of the left ventricular outflow tract in an asymptomatic adult patient.
This case highlights the importance of transthoracic and transesophageal echocardiography in the diagnosis and follow-up of this uncommon congenital anomaly. (Tex Heart
Inst J 2008;35(3):324-6)
A
Key words: Accessory
mitral valve; echocardiography; heart murmurs; heart
valve diseases/congenital/
complications; left ventricular outflow obstruction/
etiology/ultrasonography;
mitral valve abnormalities/
ultrasonography
From: Department of
Cardiology (Drs. Calderon,
Guerrero, Medina, Mesa,
and Rozo), Texas Heart
Institute at St. Luke’s Episcopal Hospital, Houston,
Texas 77030; and the
Corbic Research Foundation-HMUA (Dr. Mesa),
Envigado, Colombia
Address for reprints:
Andrés Mesa, MD,
Texas Heart Institute,
6624 Fannin St.,
Suite 2390,
Houston, TX 77030
E-mail: amesa@
comcast.net
© 2008 by the Texas Heart ®
Institute, Houston
324
ccessory mitral valve (AMV) is an uncommon cause of left ventricular outflow tract (LVOT) obstruction in children. This entity was first reported in
1842 by Chevers1; the 1st surgical management was described in 1963.2 Accessory mitral valve is usually associated with other congenital abnormalities of the
heart and great vessels, such as ventricular septal defects and transposition of the great
arteries.3-6 Fewer than 100 cases of AMV have been reported in the literature,3,5 most
of which have been in children.
Patients who have AMV with any significant obstruction usually present in the
early days or years of life with a heart murmur and symptoms of LVOT obstruction,
such as exercise intolerance, chest pain on exertion, syncope, and heart failure.3-5 The
symptoms usually become manifest when the mean gradient across the LVOT surpasses 50 mmHg.5,7-9 Identification of asymptomatic adult patients without LVOT obstruction is uncommon.4
We describe the echocardiographic diagnosis of nonobstructive AMV in an asymptomatic woman with a systolic murmur. This case emphasizes the importance of Doppler echocardiography in the noninvasive functional evaluation and follow-up of this
condition.4,5,7,9,10
Case Report
A 55-year-old asymptomatic woman was referred to our institution for evaluation of a
systolic heart murmur. She had a history of obesity and controlled hypertension. Her
current daily medications included atenolol (25 mg), amlodipine (5 mg), and losartan/hydrochlorotiazide (100/25 mg). Physical examination revealed a faint, grade 2/6,
mid-systolic murmur best heard at the left sternal border, with maximal intensity at
the cardiac base, not radiating to the neck. The 1st and 2nd heart sounds were normal, and no 3rd or 4th sound, gallop, or rub was detected. The electrocardiographic results were normal.
Transthoracic echocardiography showed a small structure attached to the anterior
mitral valve leaflet. The mean pressure gradient across the LVOT was 6 mmHg, and
the maximum velocity between the aorta and the left ventricle was 2 m/sec, which
suggested mildly increased outflow velocity. The cardiac chambers were of normal
size; no left ventricular hypertrophy was seen. The left ventricular ejection fraction
was 0.65.
Transesophageal echocardiography (TEE) revealed a mobile, echogenic, membrane-like structure that moved into the LVOT during systole and occupied the
Accessory Mitral Valve without LVOT Obstruction
Volume 35, Number 3, 2008
subaortic area. The structure was attached to the ventricular side of the proximal part of the anterior leaflet
as a chordae tendineae-like structure, thereby meeting
the description of an AMV (Fig. 1). The aortic valve
was trileaflet and normal. There was no evidence of aortic insufficiency; however, the maximum velocity in the
LVOT was slightly elevated at 1.6 m/sec, with a mean
gradient of 3.3 mmHg. Two-dimensional color-flow
Doppler TEE showed trace turbulence in the systolic
flow, starting immediately proximal to the lesion (Fig.
2). No other congenital heart anomaly was present.
The findings were discussed with the patient, and
endocarditis prophylaxis and close follow-up with serial echocardiograms were the recommendations. Surgical treatment was not considered, because the AMV
did not cause substantial LVOT obstruction and was
not associated with symptoms, aortic insufficiency, or
other associated congenital disease. At follow-up, nearly 3 years later, the patient remained free of symptoms
or events.
LA
AML
Ao
LV
RV
Fig. 2 Two-dimensional color-flow Doppler echocardiogram
(long-axis view) of the left ventricle at 140° shows color aliasing
(high flow velocity) (arrow) without significant obstruction at the
left ventricular outflow tract.
AML = anterior mitral leaflet; Ao = aorta; LA = left atrium; LV =
left ventricle; RV = right ventricle
Real-time
motion
image is available
texasheart.org/journal.
Click here
for real-time
motionatimage:
Fig. 2.
Discussion
Accessory mitral valve is rare and may be an unusual
cause of subvalvular LVOT obstruction.11 This entity is
usually seen in symptomatic children with other congenital abnormalities of the heart and great vessels.5,6,12
Herein, we describe the rare presentation of AMV in
an aysmptomatic adult without evidence of a significant degree of LVOT obstruction. In 2003, Prifti and
colleagues5 reviewed all the previously reported cases of
AMV; of the 90 patients, 51 were men and 39 were
LA
AML
Ao
LV
RV
Fig. 1 Multiplane transesophageal echocardiogram (long-axis
view) of the left ventricle at 132° shows the accessory mitral
valve (arrow) attached to the ventricular side of the proximal part
of the anterior leaflet of the mitral valve, moving into the left ventricular outflow tract during systole.
AML = anterior mitral leaflet; Ao = aorta; LA = left atrium; LV =
left ventricle; RV = right ventricle
Real-time
image ismotion
available
at texasheart.org/journal.
Click heremotion
for real-time
image:
Fig. 1.
Texas Heart Institute Journal
women (mean age, 8.6 yr; range, neonatal to 77 yr).
Most of the patients were diagnosed with AMV during
the 1st decade of life.5 Only 15 (16.7%) of the 90 patients had mild LVOT obstruction and 3 (3.3%) had
none. In fact, most cases involved severe LVOT obstruction, with a median LVOT gradient of more than 50
mmHg.5,8,9 Cases of isolated AMV, such as ours—in
an asymptomatic adult with a low LVOT gradient and
no associated congenital lesions—are rare.5,13
Accessory mitral valve tissue has been variably described as sac-like, balloon-like, parachute-like, sailshaped, and leaflet-like, or as a sheet, membrane, or
pedunculated mass. In addition, AMV tissue has been
classified on the basis of intraoperative descriptions and
anatomic presentation. Type I AMV, defined as a fixed
mass, can have a nodular (type IA) or membranous
(type IB) presentation. Type II AMV occurs as a mobile mass and is classified as pedunculated (type IIA) or
leaflet-type (type IIB). Type IIB AMVs are further divided into those with rudimentary chordae tendineae
(type IIB1) or well-developed chordae tendineae (type
IIB2).3,5 Type IIB has been the most frequent presentation reported (33/58 patients, 56.8%).5 Preoperative findings have shown 6 different locations of the
insertion of the chordae tendineae of the AMV: the
left ventricular wall, interventricular septum, accessory papillary muscle, anterolateral papillary muscle, anterior mitral valve leaflet, and the anterior mitral valve
chordae. The most common location has been the anterolateral papillary muscle (14/32, 44%).5,12 In our patient, the AMV tissue had a membrane-like appearance,
with features most similar to those of type IIB.
Accessory Mitral Valve without LVOT Obstruction
325
Rarely, subaortic LVOT obstruction is caused by an
AMV. During early childhood, systolic ballooning of
the AMV into the outflow tract results in a mass effect
and subaortic obstruction. Within a few years, the continuing turbulence produced by AMV into the LVOT
can result in permanent deposits of fibrous tissue and
subaortic obstruction.13 To our knowledge, there have
been few reports concerning the progression of LVOT
obstruction in adult patients with AMV. In fact, the incidence, natural history, and embryologic development
of this malformation are not fully understood. However, the embryologic development seems to involve an
abnormal or incomplete separation of the mitral valve
from the endocardial cushion during cardiac development.4,13,14
Because other types of left ventricular masses such
as tumors (myxomas and papillary fibroelastomas) or
vegetations can produce similar echocardiographic appearances, AMV should be considered in the differential diagnosis of a cardiac mass. Of note, the origin of
these masses can be used for differentiation; tumors
often arise from cardiac muscle, and vegetations tend to
originate from the build-up in the low-pressure side of
the heart valve.5,9
Echocardiography has been considered to be the optimal imaging technique for the diagnosis of AMV since
its use for this purpose was first reported in 1985 by Alboliras and colleagues.7,10,15,16 During the past decade,
the number of reports of AMV has increased significantly,5,6,9 likely because of the widespread availability of
Doppler echocardiography. Echocardiography, especially TEE,17 is a valuable diagnostic tool for clarifying the
nature, morphology, and attachment points of a mass
in the LVOT in a patient with an asymptomatic murmur.5,9,10 Such methods enabled the avoidance of an invasive approach, such as cardiac catheterization, in our
patient, who lacked symptoms, significant LVOT obstruction, and aortic insufficiency. We were able to recommend a conservative approach, given that we could
ensure close, periodic, echocardiographic follow-up for
early identification of any changes that might warrant
surgery.
5. Prifti E, Bonacchi M, Bartolozzi F, Frati G, Leacche M, Vanini V. Postoperative outcome in patients with accessory mitral
valve tissue. Med Sci Monit 2003;9(6):RA126-33.
6. Iba Y, Saito S, Kawai A, Kurosawa H. Images in cardiovascular medicine. Mitral valve prolapse associated with accessory
mitral valve. Circulation 2005;111(8):e107.
7. Ascuitto RJ, Ross-Ascuitto NT, Kopf GS, Kleinman CS, Talner NS. Accessory mitral valve tissue causing left ventricular
outflow obstruction (two-dimensional echocardiographic
diagnosis and surgical approach). Ann Thorac Surg 1986;42
(5):581-4.
8. Costa J, Almeida J, Barreiros F, Sousa R. Accessory mitral
valve as cause of left ventricular obstruction in the adult. J
Thorac Cardiovasc Surg 2003;125(6):1531-2.
9. Popescu BA, Ghiorghiu I, Apetrei E, Ginghina C. Subaortic stenosis produced by an accessory mitral valve: the role of
echocardiography. Echocardiography 2005;22(1):39-41.
10. Eiriksson H, Midgley FM, Karr SS, Martin GR. Role of
echocardiography in the diagnosis and surgical management
of accessory mitral valve tissue causing left ventricular outflow
tract obstruction. J Am Soc Echocardiogr 1995;8(1):105-7.
11. Tanaka H, Kawai H, Tatsumi K, Kataoka T, Onishi T, Yokoyama M, Okita Y. Accessory mitral valve associated with aortic and mitral regurgitation and left ventricular outflow tract
obstruction in an elderly patient: a case report. J Cardiol 2007;
50(1):65-70.
12. Tanaka H, Okada K, Yamshita T, Nakagiri K, Matsumori
M, Okita Y. Accessory mitral valve causing left ventricular
outflow tract obstruction and mitral insufficiency. J Thorac
Cardiovasc Surg 2006;132(1):160-1.
13. Uslu N, Gorgulu S, Yildirim A, Eren M. Accessory mitral
valve tissue: report of two asymptomatic cases. Cardiology
2006;105(3):155-7.
14. Aoka Y, Ishizuka N, Sakomura Y, Nagashima H, Kawana M,
Kawai A, Kasanuki H. Accessory mitral valve tissue causing
severe left ventricular outflow tract obstruction in an adult.
Ann Thorac Surg 2004;77(2):713-5.
15. Alboliras ET, Tajik AJ, Puga FJ, Ritter DG, Seward JB. Accessory mitral valve tissue in association with discrete subaortic stenosis: a two dimensional echocardiographic diagnosis.
Echocardiography 1985;2:191-5.
16. Sharma R, Smith J, Elliott PM, McKenna WJ, Pellerin D.
Left ventricular outflow tract obstruction caused by accessory
mitral valve tissue. J Am Soc Echocardiogr 2006;19(3):354.
e5-8.
17. Massaccesi S, Mancinelli G, Munch C, Catania S, Iacobone
G, Piccoli GP. Functional systolic anterior motion of the mitral valve due to accessory chordae. J Cardiovasc Med (Hagerstown) 2008;9(1):105-8.
References
1. Chevers N. Observations on diseases of the orifice and valves
of the aorta. Guy’s Hosp Rep 1842(7):387-452.
2. MacLean J, Culligan J, Kane D. Subaortic stenosis due to accessory tissue on the mitral valve. J Thorac Cardiovasc Surg
1963;45:382-7.
3. Prifti E, Frati G, Bonacchi M, Vanini V, Chauvaud S. Accessory mitral valve tissue causing left ventricular outflow tract
obstruction: case reports and literature review. J Heart Valve
Dis 2001;10(6):774-8.
4. Rovner A, Thanigaraj S, Perez JE. Accessory mitral valve in an
adult population: the role of echocardiography in diagnosis and
management. J Am Soc Echocardiogr 2005;18(5):494-8.
326
Accessory Mitral Valve without LVOT Obstruction
Volume 35, Number 3, 2008