Lambl’s excrescences, also known as valvular strands, are small, filiform, fibrous strands located on cardiac valves.
Thought to be present in 70-80% of adults according to pathological studies, but only ~40% on echocardiograph studies . When present, multiple Lambl’s excrescences are present in the vast majority of cases .
These lesions are asymptomatic and either get discovered incidentally or less commonly, if implicated in thromboembolic ischemic stroke, which is the feared complication arising from these lesions . However, the incidence of ischemic stroke due to Lambl’s excrescences is thought to be very rare, with one study reporting an incidence of less than 0.5 per 100 person-years .
Macroscopically, Lambl’s excrescences are small, filiform strands that are up to 10 mm in length with a thickness of up to 1.5 mm . When larger in size or multiple strands are part of the one complex, the descriptor giant Lambl’s excrescences may be employed . Histologically, these lesions are composed of a fibroelastic and avascular core, covered by an outer layer of endothelial cells .
Lambl’s excrescences may exist on either native and prosthetic cardiac valves . Typically, they form at the lines of valve closure, most commonly of the mitral and aortic valves, with the right heart valves affected in less than 10% of all cases . This location on the lines of valve closure serves as an important distinction from similarly appearing cardiac papillary fibroelastomas, which are instead usually located on the valve surface and are also rarely multiple in number .
The exact pathogenesis is uncertain. It has been postulated that the initiating factor is trauma or shear forces to the endocardium of these heart valves, which most often occurs at the lines of closure, followed by subsequent fibrous covering .
Generally only echocardiography is required to make the diagnosis, although cardiac MRI may be performed to exclude other differential lesions .
The defining features of valvular strands on echocardiography are as follows;
- filiform morphology
- width of 2 mm or less
- length between 3-10 mm
- undulating motion
- highest density at lines of leaflet closure
- when associated with valvular prostheses more commonly located on the hinge points, sewing ring, or struts
They most commonly occur on the upstream aspect of the aortic and mitral valves, and often multiple are present .
Treatment and prognosis
Surgical resection may be required if giant or if thought to be the etiology of ischemic stroke, however generally no treatment is required .
History and etymology
Lambl’s excrescences were eponymously named after Vilem Dusan Lambl (1824-1895), a Bohemian physician, who discovered these lesions in 1856 .