Year : 2019 | Volume
: 3 | Issue : 3 | Page : 198--199
Unicuspid Aortic Valve: Overview of a Rare Congenital Cardiac Anomaly
Senior Consultant (SAG Officer), Department of Medicine, Deen Dayal Upadyaya Hospital, Hari Nagar, New Delhi, India
Deen Dayal Upadhaya Hospital, Hari Nagar, GNCT of Delhi, New Delhi - 64
|How to cite this article:|
Golani D. Unicuspid Aortic Valve: Overview of a Rare Congenital Cardiac Anomaly.J Indian Acad Echocardiogr Cardiovasc Imaging 2019;3:198-199
|How to cite this URL:|
Golani D. Unicuspid Aortic Valve: Overview of a Rare Congenital Cardiac Anomaly. J Indian Acad Echocardiogr Cardiovasc Imaging [serial online] 2019 [cited 2020 May 29 ];3:198-199
Available from: http://www.jiaecho.org/text.asp?2019/3/3/198/273307
Natural history of unicuspid aortic valve (UAV) is poorly  described in the literature although its mention dates back to 1958 by Edwards. It manifests as asymptomatic cardiac murmur or with dyspnea, angina, syncope, dizziness, and heart failure. UAV accounts for 5.6% of all aortic valve replacements (AVRs). Diagnosis by echocardiography is possible only in 20% of cases and majority of UAV recognition is either at examination of surgically excised valve or at autopsy.
Normal aortic cusps develop from three tubercles that are converted into three cusps and sinuses of Valsalva by the process of excavation. Disordered number results from fusion/duplication of cusps; their occurrence in decreasing order of frequency is 0.9%–1.3% for bicuspid, 0.02% for unicuspid, and 0.08–0.04 for quadricuspid. Decreasing cusp number has shown male predilection (3:1 for bicuspid aortic valve [BAV] and 4:1 for UAV), earlier valve failure, and aggressive pathological changes including calcification.
UAV is of two different types: (1) acommissural UAV and (2) unicommissural UAV. Both varieties differ in terms of structure, onset of illness, progression of lesion, and timing of intervention. Acommissural UAV has single leaflet without any commissure and has a small central pinhole opening. It usually presents as severe aortic stenosis that is symptomatic early in life during infancy and requires early intervention for survival. Unicommissural UAV has one cusp with one large eccentric hole (that has oval, exclamation mark, or teardrop shape) along with single commissure attached to the aortic root. Unicommissural UAV presents later in life in 3rd to 5th decades either as severe aortic stenosis with or without incompetence. There is a case report of heavily calcified UAV presenting late at 63 years of age.
As there is a risk of sudden cardiac death and AVR is required 10–20 years earlier in UAV than in BAV and 20–30 years earlier than in tricuspid aortic valve, it is imperative to have accurate diagnosis of UAV and its type. Associated congenital anomalies, namely patent ductus arteriosus (5%), aortic aneurysm (5%), ventricular septal defect (12%), coarctation of aorta (37%), and congenital coronary artery anomalies, add to morbidity and mortality. There is an additional future risk of development of dilation of aortic root, ascending aorta, and dissection of aorta resulting from hemodynamic stress and congenital weakness of aortic media. Echocardiography (transthoracic, transesophageal, and real-time 3-dimensional echocardiography) is the most commonly used tool for diagnosis. It becomes imperative to image all possible views (especially systolic frame to have idea of valve opening) to assess annular attachment zone, severity of aortic stenosis and incompetence, ascending aorta, left ventricular changes, other valvular structures, and other associated congenital anomalies. Ancillary imaging, namely cardiac computed tomography (CT), magnetic resonance imaging, and CT-angiography, is to be used for a comprehensive preoperative workup. The need for such imaging studies were substantiated by a review article of 60 pediatric cases, in which it was amply demonstrated that preoperative diagnosis of UAV was rare and diagnosis was mainly after pathological examination of excised valve and at autopsy., In fact, difference between unicuspid and bicuspid valve may be subtle: a helpful differentiating feature is that normal commissures are located above the coronary ostia, but rudimentary commissure of unicuspid valve is located lower than the coronary ostia. One has to exclude hypoplastic left heart syndrome which is characterized by aortic root diameter <4–5 mm, slit-like left ventricle with end-diastolic volume <20 ml/m2, mitral annular diameter <9 mm, and left ventricular inflow end-diastolic dimension <25 mm.
Intervention options for UAV are palliative (balloon or surgical aortic valvotomy), AVR, Ross procedure, and aortic root replacement. Many affected patients require intervention for severe stenosis in infancy/childhood (especially acommissural type); others require surgery for severe calcific stenosis/incompetence several years later. Valve dysfunction can also occur 10–20 years earlier than with bicuspid valve. Aortic dissection also occurs at a younger age. Although stenosed UAV may be treated by valvotomy, regurgitant valves are commonly replaced. Surgical valvotomy has distinct advantage over balloon valvotomy in that resection of nodular dysplasia, thinning of leaflets, recreation of interleaflet triangles, and creation of neocommissure is possible. Usually, bicuspidation is done as valve competency and stability are better achieved than tricuspidation. However, decision regarding balloon versus surgical valvotomy is on individual basis; nevertheless, gentle balloon dilation does stabilize patient with depressed left ventricular function. Ultimately, AVR or Ross procedure (to avoid anticoagulation) is required. Aortic root replacement is additionally required if aortic root/ascending aorta diameter exceeds 4.5 cm. There may be a need to implant permanent pacemaker (in 3%–8%) during AVR when calcified UAV has calcification extending into interventricular septum.
In the previous issue of JIAE, the author has lucidly presented a case report of unicommissural UAV in a 21-year-old male. Diagnosis is on the basis of apt clinical and echocardiographic skills (images appear to be crisp and explanatory), later confirmed on surgery. The author has given overview description of UAV and has rightly mentioned need to identify associated lesions including current recommendation of aortic root replacement.
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