Parachute accessory anterior mitral valve leaflet causing left ventricular outflow tract obstruction. Report of a case with emphasis on the echocardiographic findings

A case of percutaneous septal myocardial ablation in a patient with obstructive hypertrophic cardiomyopathy with accessory mitral valve tissue

Accessory mitral valve tissue (AMVT) is a rare congenital anomaly that sometimes causes left ventricular outflow tract (LVOT) obstruction. We report the case of a 72-year-old woman with hypertrophic obstructive cardiomyopathy (HOCM) complicated by AMVT. The patient presented at our hospital with palpitations and shortness of breath. Transthoracic echocardiography revealed a diagnosis of HOCM and an abnormal structure inside the LVOT. Transesophageal echocardiography revealed an AMVT. We initially treated the patient with oral medication, but due to side effects, the patient could not take the target dose and her symptoms did not improve. We suggested surgical treatment, but the patient refused. By evaluating the relationship between AMVT and the surrounding tissues using three-dimensional transesophageal echocardiography, we determined that percutaneous septal myocardial ablation (PTSMA) might be successful. The first PTSMA was not effective, but the second procedure showed significant improvement in the pressure gradient and symptoms. The patient with HOCM and concomitant AMVT had a severe LVOT pressure gradient, and PTSMA was performed with excellent results. Since we experienced a rare case and were able to treat it percutaneously, we report our findings in relation to the literature.

Learning objective

This case study highlights successful use of percutaneous septal myocardial ablation (PTSMA) in treating a patient with hypertrophic obstructive cardiomyopathy (HOCM) and accessory mitral valve tissue (AMVT). The key objective is to understand PTSMA can be an effective treatment option for HOCM with Type IIa AMVT, characterized by the attachment only to the mitral leaflets, when surgical intervention is not preferred, enhancing management of this rare condition.

Accessory mitral valve tissue: anatomical and clinical perspectives

Mitral valve is a complex cardiac structure composed of several components to work in synchrony to allow blood flow into left ventricle during diastole and not to allow blood flow into left atrium during systole. Accessory mitral valve tissue (AMVT) was defined as existence of any additional part and parcel of valvular structure which has an attachment to normal mitral valve apparatus in left-sided cardiac chambers. AMVT may present itself in different clinical circumstances ranging from a silent clinical course to thromboembolic events, heart failure, left ventricular outflow tract obstruction, and severe arrhythmia. This article reviews the clinical perspectives of AMVT in terms of symptoms, diagnosis, and treatment, providing a new anatomical classification regarding the location of AMVT. Briefly type I refers to AMVT having attachments on the supra leaflets level, type II refers to attachments on the mitral leaflets, and type III refers to attachment below the mitral leaflets. Increased awareness and widespread use of echocardiographic techniques would increase recognition of AMVT in patients with heart murmurs but otherwise healthy and in those with left ventricular outflow tract obstruction or tissue which causes subaortic stenosis and with unexplained cerebrovascular events.

Left ventricular false tendons: echocardiographic, morphologic, and histopathologic studies and review of the literature

BACKGROUND

Left ventricular false tendons (LVFTs) are fibrous or fibromuscular bands stretching across the left ventricle (LV) from the ventricular septum to the papillary muscle or LV free wall but not connecting, like the chordae tendinae, to the mitral leaflet. LVFTs have become the focus of studies and discussions since the advent of echocardiography.

MATERIALS AND METHODS

We prospectively studied the prevalence of LVFTs by two-dimensional echocardiography in 476 infants and children referred to our institute for cardiac evaluation and cardiology workup. We also studied the morphology and histopathology of LVFTs in 68 congenital heart disease specimens and in 20 piglet hearts. The literature was reviewed and the clinical significance of LVFTs was discussed.

RESULTS

LVFTs of varying size and different location were detected in 371 (77.9%) of 476 infants and children studied, in 42 (61.8%) of 68 congenital heart disease specimens, and in 19 (95.0%) of 20 piglet hearts. Of the 75 LVFTs from the congenital heart disease specimens, 33 (44.4%) were fibrous type, measuring less than 1.4mm; 38 (50.7%) were fibromuscular type, 1.5-2.4mm; and 4 (5.3%) were muscular type, 2.5mm or more in diameter. Of the 33 LVFTs from the piglet hearts, 23 (69.7%) and 10 (30.3%) were fibrous and fibromuscular, respectively, and none (0.0%) was muscular.

CONCLUSIONS

LVFTs were detected partially or completely by modified two-dimensional echocardiography in both normal and abnormal hearts. LVFTs is a useful anatomical landmark of LV for the differentiation of morphological LV and right ventricle in segmental analysis of congenital heart disease. LVFTs are a cause of functional murmur. No pressure gradient was noted in the mid-LV or outflow tract. LVFTs could be a contributory factor in the generation of dysrhythmias during LV catheterization studies. LVFTs were more easily identifiable in neonates and young age patients because of a better delineation of images in echocardiography.

Left ventricular outflow tract obstruction caused by accessory mitral valve tissue

This report describes the echocardiographic diagnosis of accessory mitral valve tissue causing left ventricular outflow tract obstruction in a symptomatic man. The accessory tissue was surgically removed and the mitral valve replaced with complete resolution of left ventricular outflow tract gradient and symptoms. The case illustrates the importance of transthoracic and transesophageal echocardiography in the diagnosis and preoperative evaluation of this rare but treatable cause of subaortic valve obstruction.

Accessory mitral valve tissue: report of two asymptomatic cases

Accessory mitral valve tissue is a rare anomaly of embryologic development of the endocardial cushion and may cause substantial and progressive obstruction of the left ventricular outflow tract. Subaortic obstruction resulting from accessory mitral tissue is most likely due to systolic ballooning of the tissue into the outflow tract. The obstruction can occur in the early period of life as a result of mass effect or it can develop gradually due to the continued deposition of fibrous tissues within the left ventricular outflow tract. In patients with accessory mitral valve tissue, surgery is mandatory if there is a significant obstruction in the left ventricular outflow tract. We report two cases with accessory mitral valve tissue causing mild subaortic stenoses which did not require surgery.

Accessory mitral valve tissue manifesting cerebrovascular thromboembolic event in a 34-year-old woman

Accessory mitral valve tissue is an extremely rare congenital cardiac anomaly. Most of the cases reported in the medical literature were associated with left ventricular outflow tract obstruction. The majority of cases of accessory mitral valve tissue, causing left ventricular outflow tract obstruction, occur in association with other congenital cardiac anomalies. In this reported case, a patient with accessory mitral valve tissue complicated with thromboembolic cerebrovascular event is presented. The patient also had an associated idiopathic hypertrophic subaortic stenosis.

Critical subaortic stenosis in a newborn caused by accessory mitral valve tissue

A 2-week-old newborn girl underwent successful surgery in our clinic for critical subaortic stenosis caused by accessory mitral valve tissue, which, because of excessive growth, protruded into the left ventricular outflow tract. The preoperative pressure gradient below the aortic valve was 80 mm Hg. The operation consisted of resection of the accessory tissue through a combined aortotomy and atriotomy approach without residual pressure gradient and mitral valve incompetence. This approach is recommended to ensure that accessory tissue is removed without damaging the mitral valve.

Critical left ventricular outflow tract obstruction due to accessory mitral valve tissue

Left ventricular outflow tract (LVOT) obstruction due to anomalous tissue tag arising from the mitral valve is a rare congenital cardiac anomaly. It generally becomes symptomatic during the first decade of life as exercise intolerance, chest pain, or syncope at effort. To date, only a few cases of critical systemic obstruction due to isolated mitral valve anomaly in neonates have been reported. We report the case of a neonate who was a few hours old and was referred in severe clinical condition due to critical left ventricular outflow obstruction resulting from an anomalous tissue tag of mitral valve origin.

Anomalous papillary muscle as a cause of left ventricular outflow tract obstruction in an adult

Left ventricular outflow tract obstruction may be caused by abnormalities of the various structures comprised by the outflow tract. Hypertrophic cardiomyopathy is one of the more common causes, but many are rare anomalies, a collection of which we have compiled. We present a case of left ventricular outflow tract obstruction mimicking aortic stenosis in an adult. This was found to be due to abnormal insertion of a hypertrophied papillary muscle, successfully corrected by mitral valve replacement.

Recognition and management of accessory mitral tissue causing severe subaortic stenosis

Failure to recognize the presence of accessory mitral tissue causing subaortic stenosis can lead to not only the performance of inappropriate operations, but the persistence and recurrence of obstruction or even death. Over a 12-month period, we treated 2 children with severe subaortic stenosis caused by accessory mitral tissue. In 1 patient, who was 4 years old, the echocardiogram showed the accessory mitral tissue to be attached to the anterior mitral leaflet and ballooning into the subaortic area. The other patient, as a newborn, underwent simultaneous repair of a complete canal defect and coarctation. Two years later, the patient was seen because of syncopal episodes, progressive mitral insufficiency, and subaortic stenosis thought to be caused by anterior displacement of the anterior mitral leaflet. Mitral valvuloplasty and a conal enlargement procedure were planned. Intraoperatively, after the mitral valvuloplasty had been done, the subaortic stenosis was found to be due to a tight subaortic ring formed by accessory mitral tissue located at the septum and its fibrous extension to the anterior mitral leaflet. In both patients, excision of the accessory mitral and fibrous tissues resulted in a wide-open subaortic area. Both patients had an uneventful hospital course, and follow-up echocardiography showed no noteworthy residual left ventricular outflow gradient. We believe that increased awareness and sophisticated echocardiographic techniques should lead to an increased recognition of accessory mitral tissue causing subaortic stenosis. Simple resection of the accessory mitral tissue and its secondary fibrous tissues can be curative.

Diagnosis of accessory mitral valve tissue by transesophageal echocardiography

Accessory mitral valve tissue is a rare cause of intracardiac mass and subvalvular left ventricular outflow tract obstruction. The preoperative diagnosis of this congenital anomaly has been facilitated by transthoracic two-dimensional and Doppler echocardiography. However, transthoracic two-dimensional echocardiography cannot identify or correctly diagnose all cases of accessory mitral valve tissue. We report a patient in whom an intracardiac mass detected by transthoracic echocardiography was definitively diagnosed as accessory mitral valve tissue by transesophageal echocardiography.

Trans-ventricular septal defect approach for resection of accessory mitral valve tissue

Accessory mitral valve tissue is a rare cause of left ventricular outflow tract obstruction, which can be difficult to recognize. Surgical resection by the conventional transaortic approach with or without left atriotomy is extremely difficult in infants with a small aorta. When a ventricular septal defect is present, it may be the best way to approach the accessory mitral valve tissue, because the ventricular septal defect is located just in front of it. Five infants underwent resection of accessory mitral valve tissue together with repair of other intracardiac malformations. In 3 infants, resection of accessory mitral valve tissue was easily performed through the ventricular septal defect, which required enlargement in 2 patients.

A case of accessory mitral valve leaflet associated with solitary mitral cleft

Accessory mitral valve leaflet is a rare congenital anomaly. More than half of the cases show other congenital cardiac defects and almost all of the cases show subaortic obstruction. We report a case of an accessory mitral valve tissue without outflow obstruction associated with mitral cleft of the posterior mitral leaflet. To our knowledge, this is the first reported case of the combination of these two congenital anomalies.

Surgical options in subaortic stenosis associated with endocardial cushion defects

Over a 15-year period, 12 patients with endocardial cushion defects undergoing correction had subaortic stenosis requiring operative intervention. Ages ranged from 4 months to 17 years (mean, 7 +/- 6 years) and subaortic gradients from 15 to 100 mm Hg (mean, 60 +/- 25 mm Hg). Subaortic stenosis was due to discrete fibromuscular tissues in 7 patients, mitral valve malattachment in 3, and tunnel outflow in 2. In 2, the subaortic stenosis was clinically significant at the time of endocardial cushion defects repair, whereas in 10 it was noted 2 to 14 years postoperatively (mean, 6.3 +/- 5 years). Surgical relief of subaortic stenosis was accomplished by resection of muscle tissues in 7, apicoaortic conduit insertion in 2, modified Konno procedure (aortic valve preserved) in 2, and lifting of malattached mitral valve from the outflow in 1. There was no early death and one late death (infected conduit). Severe mitral insufficiency developed in the patient who had the mitral valve lifted and necessitated valve replacement. Postoperative echocardiographic gradient in 9 patients ranged from 0 to 36 mm Hg (mean, 10.5 +/- 14 mm Hg). Clinically significant subaortic stenosis has not developed in any patient in 15 years of follow-up (mean, 5 +/- 4 years). We conclude that in subaortic stenosis associated with endocardial cushion defects, resection is effective for discrete obstruction, whereas a modified Konno procedure is preferable for obstruction due to tunnel outflow or mitral valve malattachment.

Accessory mitral valve leaflet causing aortic regurgitation and left ventricular outflow tract obstruction. Case report and review of published reports

Arrhythmias, aortic regurgitation, and symptoms of severe intermittent ventricular outflow obstruction developed in a 14 year old boy with a heart murmur who had been followed from infancy. These were caused by an accessory mitral leaflet, which was successfully removed at open heart operation. A review of 21 previously reported cases found a high incidence of associated cardiac malformations, appreciable subaortic obstruction in most patients, and a consistent attachment of the accessory tissue to the ventricular aspect of the anterior mitral leaflet. The characteristic echocardiographic appearance of a mobile mass arising from the area of aortic-mitral continuity is sufficient for the diagnosis of accessory mitral leaflet and echocardiographic examination will facilitate the surgical management of this condition.

Accessory mitral valve tissue causing left ventricular outflow obstruction (two-dimensional echocardiographic diagnosis and surgical approach)

Accessory mitral valve tissue, a rare cause of left ventricular outflow tract obstruction, can be difficult to diagnose preoperatively and confusing even at surgery. The reported case illustrates how preoperative evaluation can be made using two-dimensional echocardiography combined with Doppler flow analysis. The intraoperative technique for removing the accessory tissue without causing damage to the native mitral valve is discussed.

Anomalous papillary muscle insertion contributing to obstruction in discrete subaortic stenosis

A case of discrete subvalvular aortic stenosis with anomalous insertion of a papillary muscle to the base of the anterior mitral valve leaflet and continuous with the discrete subaortic stenosis is described. Two-dimensional echocardiographic and pathologic data showing the contribution of the anomalous papillary muscle to left ventricular outflow tract obstruction are presented.

Systolic closure of aortic valve in patients with prosthetic mitral valves

Systolic closure of the aortic valve was found in 10 of 36 patients who underwent mitral valve replacement. Eight patients had early systolic closure, and two had mid-systolic closure. The left ventricular outflow tract dimension on M-mode and two dimensional echocardiograms, left ventricular posterior wall and septal thickness, left ventricular dimensions in systole and diastole, aortic valve opening, and mitral to aortic valve distance were not significantly different between patients with and without systolic closure of the aortic valve. Two of the 10 patients with systolic aortic valve closure were catheterised and in neither was there a gradient between the left ventricle and the aorta. The two patients with mid-systolic closure, however, were the patients who had the narrowest left ventricular outflow tract which could cause significant distortion of blood flow. Systolic closure of the aortic valve in patients with mitral valve replacement is probably not caused by left ventricular outflow tract obstruction, though abnormalities in laminar flow from the left ventricular outflow tract may be involved.

Echocardiographic features of the false tendons in the left ventricle

M mode and two dimensional echocardiographic features consistent with previously reported autopsy findings of false tendons were seen in 5 of approximately 1,000 consecutive echocardiographic examinations. Later, the presence of false tendon was proved at autopsy in one of the five cases. Examination in three cases revealed heart disease: aortic regurgitation, third degree atrioventricular (A-V) block with aortic regurgitation and invasive thymoma with pericardial effusion; examination in two cases revealed no heart disease. In three cases, M mode echocardiograms revealed in the outflow tract of the left ventricle abnormal linear echoes that strongly mimicked those in other disorders such as discrete subaortic stenosis or flail aortic valve. In two cases, there were abnormal linear echoes in the left ventricle toward the apex. In three cases, two dimensional echocardiograms revealed long-string-like echoes stretching from the upper part of the interventricular septum across the ventricular cavity to the lateral wall of the left ventricle in long and short axis views or in four chamber views. In two cases, long slender echoes between the lower parts of the interventricular septum and the left ventricle were seen in apical long axis views. These string-like echoes seem to represent the false tendons previously reported at autopsy, although actual pathologic confirmation was available in only one of the five cases. It is concluded that (1) M mode and two dimensional echocardiograms can demonstrate the presence of false tendons, (2) two dimensional echocardiograms are useful in differentiating false tendons from other conditions causing abnormal linear echoes in the outflow tract of the left ventricle on M mode echography.

Supernumerary mitral valve producing subaortic stenosis

A ten-year-old girl with severe subaortic stenosis was found to have relatively mature valvular endocardial cushion tissue (fibromyxomatous sheets with a chorda tendinea attached to a left ventricular papillary muscle) immediately beneath the aortic valve. This structure behaved like a valve mechanism, obstructing the left ventricular outflow tract during ventricular systole. This anomaly is an extreme on the spectrum of obstructive endocardial cushion malformations.

Echocardiographic source of early anterior systolic motion in late systolic mitral valve prolapse

The echocardiographic features of patients with parachute mitral valve have revealed the combination of an early systolic movement of the mitral valve and late systolic prolapse. Cross-sectional echocardiographic and angiographic studies showed that the early systolic anterior motion was produced by the presence of a flail scallop of the anterior mitral leaflet in the left ventricular outflow tract.