European Journal of Echocardiography Advance Access published online on April 14, 2008
European Journal of Echocardiography, doi:10.1093/ejechocard/jen152
Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2008. For permissions please email: journals.permissions@oxfordjournals.org
Left ventricular outflow tract obstruction in the presence of asymmetric septal hypertrophy and accessory mitral valve tissue treated with alcohol septal ablation
Michael S. Kim,
Andrew J. Klein,
Bertron M. Groves,
Robert A. Quaife and
Ernesto E. Salcedo*
Division of Cardiology, University of Colorado Denver and Health Sciences Center, Anschutz Medical Campus, 12605 E. 16th Avenue, Campus Mail Stop B-120, Aurora, CO 80045, USA
Received 15 January 2008; .
* Corresponding author. Tel: +1 720 848 7565; fax: +1 720 848 5301. E-mail address: ernesto.e.salcedo{at}uchsc.edu
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Abstract
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Redundant or accessory mitral valve tissue (AMVT) is a rare
clinical condition. It is an even rarer cause of left ventricular
outflow tract obstruction. We report a case of an adult male
with medically unresponsive hypertrophic obstructive cardiomyopathy
in whom real-time three-dimensional transesophageal echocardiography
was used to both diagnose the presence of coexistent asymmetric
septal hypertrophy and AMVT as well as confirm the safety and
efficacy of treatment with alcohol septal ablation.
Keywords: Accessory mitral valve tissue; Hypertrophic obstructive cardiomyopathy; Alcohol septal ablation; Three-dimensional echocardiography
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Introduction
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Subaortic left ventricular outflow tract (LVOT) obstruction
may result from the presence of four distinct anatomic anomalies:
asymmetric septal hypertrophy (i.e. hypertrophic obstructive
cardiomyopathy); subaortic fibrous membrane, web, or tunnel;
abnormal mitral valve attachment; and redundant or accessory
mitral valve tissue (AMVT).
1 Redundant or AMVT is a rare clinical
condition in adults
2 and an even rarer cause of subaortic LVOT
obstruction.
3–6 Echocardiography provides important information
in the diagnosis and treatment of hypertrophic obstructive cardiomyopathy
7,8 and AMVT.
1 We report a case of an adult male in whom real-time
three-dimensional transesophageal echocardiography (3D TEE)
was used to confirm the safety and efficacy of alcohol septal
ablation treatment of combined hypertrophic obstructive cardiomyopathy
with asymmetric septal hypertrophy and AMVT.
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Case report
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A 66 year-old male with progressive exertional fatigue and dizziness
was referred for evaluation of hypertrophic obstructive cardiomyopathy.
His initial evaluation included transthoracic echocardiography
that documented moderate asymmetric left ventricular hypertrophy
with a basal septal wall thickness of 2.1 cm, systolic anterior
motion of the mitral valve with mild mitral regurgitation, and
a resting LVOT gradient of 75 mmHg that increased to 96 mmHg
during the Valsalva manoeuvre. Cardiac magnetic resonance imaging
confirmed the presence of asymmetric septal hypertrophy with
a basal interventricular septal diastolic thickness of 2.2 cm
(compared with 1.0 cm thickness of the posterior left ventricular
wall), mild resting LVOT gradient with a maximum velocity of
3.0 m/s by phase contrast imaging and systolic anterior motion
of the mitral valve with mild mitral regurgitation. The patient
was initially treated medically with separate therapeutic trials
of calcium channel blockers and beta-blockers. However, he could
not tolerate either of these pharmacologic agents secondary
to worsening fatigue and bradycardia. He was then referred for
alcohol septal ablation treatment. Because of the suspicion
of associated AMVT complicating his hypertrophic obstructive
cardiomyopathy, an intra-procedural real-time 3D TEE was performed
using an X7-2t TEE transducer and iE33 ultrasound system (Philips
Healthcare, Andover, MA, USA) to better characterize his mitral
valve leaflet motion before proceeding with alcohol septal ablation
treatment. The baseline TEE demonstrated severe septal hypertrophy
with a maximal septal thickness of 2.2 cm and a resting LVOT
pressure gradient of 114 mmHg (
Figure 1). The real-time
3D TEE also confirmed the combined presence of systolic anterior
motion of the mitral valve and AMVT (
Figure 2A) that was
prolapsed into the LVOT during ventricular systole and was associated
with mild to moderate mitral regurgitation (
Figure 2B).
Two-dimensional planar views were inadequate for determining
the presence and insertion of chordal tissue associated with
the AMVT. Clinically, this was an important issue since there
was the potential for chordal tissue (if present) originating
from the AMVT to insert into the area of asymmetric ventricular
hypertrophy. If this were the case, localized alcohol septal
ablation in this region could potentially exacerbate the severity
of mitral regurgitation by effectively creating a partially
flail anterior mitral valve leaflet.
Myocardial contrast echocardiography was performed with simultaneous
real-time 3D TEE to better define the spatial relationship between
the AMVT, LVOT, and asymmetric septal hypertrophy. The procedural
steps involved in performing both alcohol septal ablation and
myocardial contrast echocardiography have been well described
in a prior review.
9 Myocardial contrast echocardiography confirmed
localized transmural opacification of the basal ventricular
septum. Real-time 3D volumetric reconstructions following myocardial
contract echocardiography confirmed the absence of connecting
chordae originating from the AMVT (
Figure 3; see Supplementary
material online,
Video 1). Based on these findings, we felt
it was felt safe to proceed with alcohol septal ablation of
the first septal perforator branch of the left anterior descending
artery. No post-ablation complications of heart block or significant
ventricular dysrhythmia occurred. Repeat post-ablation coronary
angiography confirmed a subtotal occlusion of the first septal
perforator with no injury to the left anterior descending artery
(
Figure 4).
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Figure 3 RT3D TEE (real-time three-dimensional transesophageal echocardiography) volumetric reconstruction following enhancement with myocardial contrast highlighting accessory mitral valve tissue (AMVT) (arrowhead) and absence of connecting chordae (arrow).
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Figure 4 (A) Pre-alcohol septal ablation left coronary angiography highlighting the first septal perforator (arrowheads). (B) Post-alcohol septal ablation left coronary angiography demonstrating subtotal occlusion of the first septal perforator (arrowheads).
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Immediately post-ablation, the LVOT pressure gradient was reduced
to 11 mmHg as measured by simultaneous left ventricular/aortic
catheter recordings and TEE Doppler (
Figure 5). Slow pullback
of the pigtail catheter from the left ventricular apex to the
ascending aorta revealed no significant pressure gradient. Repeat
post-ablation real-time 3D TEE evaluation demonstrated mild
residual mitral regurgitation and improved systolic anterior
motion of the mitral valve primarily involving the AMVT as compared
with the pre-ablation echocardiographic evaluation (
Figure 6;
see Supplementary material online,
Video 2).
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Discussion
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Accessory mitral valve tissue is a very rare condition in adults
with an estimated incidence of one per 26 000 echocardiograms.
1 Although the precise embryologic mechanism of AMVT formation
remains unknown, it is thought to result from abnormal development
of endocardial cushion tissue.
10 One observation lending credence
to this theory is that AMVT is commonly associated with other
congenital intra-cardiac (i.e. ventricular septal defect) and
vascular anomalies (i.e. transposition of the great arteries,
coarctation complex).
11 Pathology studies suggest that there
are two distinct types of AMVT – mobile and fixed.
12 The
mobile type is a dysplastic, sail or parachute-like, thickened
leaflet that is projected into the LVOT during ventricular systole.
In contrast, the fixed type is firmly anchored to the interventricular
septum by short chordae, lacks mobility, and demonstrates normal
leaflet morphology. Our patient had the mobile type of AMVT,
characterized by a free-floating, sail-like leaflet which did
not appear to contribute to his LVOT obstruction.
Despite interest in other non-invasive imaging modalities (i.e. computed tomography and magnetic resonance imaging), echocardiography is currently favoured for both diagnosing and determining the clinical significance of AMVT.13–15 Three-dimensional echocardiography is ideally suited for assessing cardiac structural anomalies given the unique anatomic and spatial variations inherently associated with structural heart disease. Furthermore, it is particularly useful in evaluating valvular anatomy given the non-planar orientation of cardiac valves.16 In fact, the utility of 3D echocardiography in detecting the presence and significance of AMVT has already been reported.17–19
Although alcohol septal ablation has emerged as an effective therapeutic strategy of choice for most patients with medically refractory hypertrophic obstructive cardiomyopathy,20,21 to our knowledge, the safety and efficacy of alcohol septal for hypertrophic obstructive cardiomyopathy in the presence of AMVT which may potentially contribute to the LVOT obstruction has never been reported. In our unique case, the underlying diagnostic challenges included the ability to both determine the impact of AMVT on LVOT obstruction as well as adequately characterize AMVT anatomy to establish the safety of alcohol septal ablation. For example, the possibility of the presumed AMVT to actually be a flail subvalvular membrane needed to be definitively excluded. Flail subvalvular membranes have been reported as an etiology of subvalvular aortic stenosis.22–25 In our patient, real-time 3D TEE clarified the morphologic relationship of the AMVT and the interventricular septum by documenting both tissue origination from the anterior mitral valve leaflet (thereby excluding subvalvular membrane as a diagnosis) as well as absence of chordal attachments to the basal interventricular septum. Based on this information, we felt confident in the safety of proceeding with alcohol septal ablation of the first septal perforator of the left anterior descending artery and effectively abolished the LVOT gradient without complication.
To our knowledge, this is the first patient to be reported with hypertrophic obstructive cardiomyopathy in the combined presence of asymmetric septal hypertrophy, significant LVOT obstruction, and AMVT. We also confirmed the efficacy of using real-time 3D TEE to define difficult spatial relationships and anatomic anomalies allowing us to successfully treat LVOT obstruction with alcohol septal ablation.
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Supplementary material
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Supplementary material is available at
EJECHO online.
Video 1: RT3D TEE volumetric reconstruction following enhancement with myocardial contrast highlighting AMVT and absence of connecting chordae.
Video 2: Change in systolic anterior motion of the AMVT following alcohol septal ablation. Left frame, Pre-alcohol septal ablation; Right frame, Post-alcohol septal ablation.
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Acknowledgements
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The authors would like to express their appreciation to Doris
Peterson, RDCS, for her expertise and assistance in performing
the RT3D TEE.
Conflict of interest: none declared.
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References
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Abstract
Introduction
