
==== Front
JACC Case Rep
JACC Case Rep
JACC Case Reports
2666-0849
Elsevier

S2666-0849(24)00221-3
10.1016/j.jaccas.2024.102428
102428
Mini-Focus Issue on Congenital Heart Disease
Case Report: Clinical Case
Atypical Cardiac Anatomy Leading to Subvalvar Aortic Stenosis in a 19-Month-Old Boy With a Murmur
Stave Elise A. MD estave@childrensnational.org
a∗
d’Udekem Yves MD, PhD b
del Rosario Amanda MD c
Hanabergh Sofia S. MSc b
Gulino Sam P. MD d
Sable Craig A. MD a
a Department of Cardiology, Children’s National Hospital, Washington, DC, USA
b Department of Cardiac Surgery, Children’s National Hospital, Washington, DC, USA
c One Love Pediatrics Guam, Tamuning, Guam
d Department of Pathology and Laboratory Medicine, Children’s National Hospital, Washington, DC, USA
∗ Address for correspondence: Dr Elise Stave, Children’s National Hospital, 111 Michigan Avenue, NW, Washington, DC 20010, USA. estave@childrensnational.org
21 8 2024
21 8 2024
21 8 2024
29 16 10242824 4 2024
6 6 2024
© 2024 The Authors
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
A 19-month-old boy presented with a murmur and was found to have an unusual etiology of subvalvar aortic stenosis with discrete subaortic membrane and anomalous attachment of the anterior mitral valve papillary muscle to the interventricular septum. Preoperative suspicion for mitral valve involvement impacted surgical planning.

Key Words

aorta
congenital heart defect
mitral valve
stenosis
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pmcHistory of Presentation

A 19-month-old boy presented to the pediatrician as a new patient for a routine well child visit. He did not have any cardiac symptoms (eg, cyanosis, chest pain, tachycardia, shortness of breath, syncope). His growth and development were appropriate for age. The patient’s family lives overseas, so he was evaluated there.Learning Objectives

• To describe how the cardiovascular surgical approach to subvalvar aortic stenosis repair might differ when mitral valve apparatus anomalies are suspected.

• To identify findings on transthoracic and transesophageal echocardiogram that should raise suspicion for an abnormality of the mitral valve contributing to subvalvar aortic stenosis or formation of a subaortic membrane.

Physical examination was notable for a 3/6 systolic ejection murmur at the upper sternal border and otherwise normal evaluation.

Past Medical History

He was noted to be otherwise healthy with no past medical history.

Differential Diagnosis

Differential diagnosis includes acyanotic heart disease or an innocent murmur (eg, Still’s murmur). The grade of the murmur (3) decreases likelihood of a Still’s murmur; however, a Still’s murmur is the most likely cause of murmur in a healthy 19-month-old with appropriate growth. To further differentiate between possible causes of a grade 3 systolic murmur in acyanotic heart disease, the location at the upper sternal border could represent a finding in the aortic or pulmonic position (right vs left, respectively). Aortic stenosis would be represented by a systolic ejection murmur at the right upper sternal border, whereas pulmonic stenosis or an atrial septal defect leading to relative pulmonic stenosis would lead to a systolic ejection murmur at the left upper sternal border. Other etiologies of systolic murmur (eg, mitral or tricuspid regurgitation) would lead to a holosystolic murmur at the apex or left lower sternal border, respectively.

Investigations

An echocardiogram was performed, showing subvalvar fibromuscular aortic stenosis and mild peak and mean gradients across the membrane, with trivial aortic insufficiency. Echocardiograms were repeated every 6 months, and when he was 3 years of age, a significant increase in the left ventricular outflow tract gradient was noted (peak 60 mm Hg, mean 30 mm Hg). These echocardiograms were performed overseas and read by cardiologists at Children’s National Hospital.

Management

He was referred for surgery for subaortic membrane resection. Preoperatively, at a multidisciplinary surgical conference, possible chordal attachments between the anterior leaflet of the mitral valve and the interventricular septum were noted on transthoracic echocardiography (Video 1, Video 2, Video 3). This finding guided the transesophageal echocardiogram performed immediately prior to his operation (Videos 4 and 5). On transesophageal echocardiogram, attachment between the anterior leaflet of the mitral valve and the interventricular septum was observed. This changed the surgical approach to include a left atriotomy after transverse aortotomy to look through the mitral valve apparatus. When looking through the aortotomy, the mitral valve subvalvar apparatus was crossing under the aortic valve, with space appreciated between the subaortic membrane and the lower connection between mitral valve and septum (Video 6). No accessory mitral valve tissue was appreciated intraoperatively. A septal myectomy was performed through the aortotomy. Subsequently, both the vantage point from transverse aortotomy and from left atriotomy were used to remove dense fibrous tissue attached to the ventricular surface of the mitral valve at the insertion of the chordae tendineae on the mitral valve leaflets and fibrous tissue adherent to the right coronary cusp of the aortic valve. This was performed while avoiding damage to the mitral valve apparatus (averting the development of mitral regurgitation). Intraoperative testing of the mitral valve demonstrated a competent valve.

He tolerated the surgery well and had an unremarkable postoperative course.

Discussion

Subvalvar aortic stenosis can be grouped under the following 4 categories: hypertrophic cardiomyopathy, discrete subaortic membrane, tunnel-type subaortic stenosis, and posterior deviation of the conal septum.1 A less common cause of subvalvar aortic stenosis involves abnormalities of the mitral valve insertion or apparatus, which have been identified primarily in case reports.2, 3, 4, 5 However, mitral valve anomalies contributing to subvalvar aortic stenosis may be underestimated.6 A study evaluating 73 patients with discrete subvalvar aortic stenosis found mitral valve anomalies in 48% of these patients, including insertion of an anomalous papillary muscle into the anterior leaflet of the mitral valve; surgical correction was feasible despite these findings.6

A proposed mechanism for discrete subvalvar aortic stenosis involves abnormal left ventricular morphology, with flow abnormalities and mechanical stress leading to a fibrotic cellular response and membrane creation.7 This patient’s mitral valve papillary muscle attaching to the interventricular septum may have created additional opportunity for turbulent blood flow in the region below the aortic valve, leading to development of discrete subvalvar aortic stenosis.

A mean left ventricular outflow tract Doppler gradient over 30 mm Hg and/or progressive aortic stenosis are indications to proceed to surgery.8

Follow-Up

He was seen as an outpatient 2 weeks after discharge with good activity level and some incisional pain improved by acetaminophen or ibuprofen. A repeat echocardiogram redemonstrated the anomalous connection from mitral valve papillary muscle to the interventricular septum, without obstruction. Six months later, he exhibited no clinical change and remains well.

Conclusions

Anatomic variants of the mitral valve apparatus are important considerations when making a new diagnosis of subvalvar aortic stenosis. Careful echocardiography review is indicated to optimize surgical planning. Transesophageal echocardiography should be used preoperatively to guide the surgical approach with the goal of limiting opportunity for recurrence. In cases where the mitral valve apparatus is involved, a left atriotomy should be considered in the surgical approach for successful resection of fibrous tissue while maintaining competence of the mitral valve.

Funding Support and Author Disclosures

The authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Appendix

Video 1

Preoperative Transthoracic Echocardiography Imaging Showing Subvalvular Aortic Stenosis in Parasternal Long-Axis View

The subaortic membrane is demonstrated, with suspicion for mitral valve involvement.

Video 2

Preoperative Transthoracic Echocardiography Imaging Showing Subvalvular Aortic Stenosis in Apical 4-Chamber View

The area of subvalvular aortic stenosis is visualized more anteriorly than with a typical subaortic membrane.

Video 3

Preoperative Transthoracic Echocardiography Imaging Showing Subvalvular Aortic Stenosis in Parasternal Long-Axis View With Color-Compare

On color Doppler, aliasing under the aortic valve is appreciated.

Video 4

Preoperative Transesophageal Echocardiography

Subvalvular aortic stenosis at 0°.

Video 5

Preoperative Transesophageal Echocardiography

Subvalvular aortic stenosis at 125°.

Video 6

Surgical Video of Subvalvular Aortic Membrane Resection

Through the aortotomy, the mitral valve apparatus is visualized crossing under the aortic valve and attaching to the interventricular septum. A clip is applied to this portion of the mitral valve apparatus and the view transitions to the left atriotomy (00:19) where resection of the subaortic membrane is begun. The view returns to the aortotomy (00:32) for continued resection of subaortic membrane and myectomy. The left atriotomy is again used for additional resection (3:03-3:12).

The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the Author Center.

Appendix

For supplemental videos, please see the online version of this paper.
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