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A person (close to me genetically) recently had a surgery to replace an aortic heart valve that the surgeon called "the ugliest valve he'd seen in a long time". Two of the leaflets were fused together, which the doctor said could have been since birth.
I am wondering if this condition is known to be hereditary.
Short answer: Yes.
Fused leaflets?
The condition you’re referring to is known as Congenital bicuspid aortic valve (BAV). It is the most common congenital heart valve abnormality, present in 1-2% of live births. Normally there are three leaflets (a.k.a. cusps) comprising the aortic valve. BAV refers to the situation when there are only two cusps, a hemodynamically less favorable scenario.
Although generally benign in itself, BAV has been associated with an increased risk of several serious complications. In particular, aortic stenosis, a condition in which the blood flow exiting the heart is limited by a narrowed valve, is more common in individuals with BAV and often occurs at a younger age. Aortic stenosis in BAV patients is also frequently accompanied by aortic insufficiency, back flow through the valve. Both properties reflect the anatomic descriptor you give: ugly.
Is BAV hereditary?
Yes. This can be demonstrated by looking at familial clustering of the condition. In one study, the researchers started with thirty patients diagnosed by echocardiography with congenital BAV.* All first-degree relatives were contacted, and 90% of them agreed to undergo echocardiography. Of those, 9% were found to have BAV. This is significantly higher than the baseline population risk (~1%). The distribution was compatible with an autosomal dominant inheritance pattern with incomplete penetrance.
A more recent study used fancy math to determine the heritability of BAV.** They found that 89% of the risk for BAV is due to heritable factors.
*This paper is available in full for free and provides a nice review of the background (summarized here) as well as the findings I presented:
Huntington K, Hunter AG, Chan KL. A prospective study to assess the frequency of familial clustering of congenital bicuspid aortic valve. J Am Coll Cardiol. 1997 Dec;30(7):1809-12.
**Cripe L, Andelfinger G, Martin LJ, Shooner K, Benson DW. Bicuspid aortic valve is heritable. J Am Coll Cardiol. 2004 Jul 7;44(1):138-43.
I would just like to add one point. There are 3 important causes of aortic valve stenosis: congenitally bicuspid aortic valve, senile calcific aortic stenosis and rheumatic heart disease. In advanced stages of all 3 conditions, the morphology of aortic valve looks equally bad and it may difficult to ascertain the original pathology. Fusion of leaflets may occur in all 3 conditions. Senile degenerative aortic stenosis occurs mostly in the elderly, hence if the age of this patient is advanced, that is a very likely possibility and that condition is not familial or hereditary. Rheumatic heart disease is common in developing parts of the world and is most commonly associated with involvement of mitral valve also. Isolated aortic involvement is much less common in rheumatic heart disease.
Not all patients with bicuspid aortic valve will progress to narrowing or regurgitation. Stenosis/regurgiation may occur after many years or may not occur at all. Also, milder degrees of valve dysfunction do not cause any symptoms and do not need surgery.
Hope this helps.
References:
http://www.mayoclinicproceedings.org/article/S0025-6196%2812%2961880-1/abstract?cc=y=
http://www.sciencedirect.com/science/article/pii/004681779390267K
