Blood cyst of the pulmonary valve in an adult: report of a case and review of the literature

We report a case of a blood cyst originating from the pulmonary valve cusp of a 43-year-old Japanese woman with pulmonary stenosis. Cineangiography revealed a pedunculated tumor on the arterial surface of the pulmonary valve. It was successfully removed by a transpulmonary artery approach. The cyst contained old blood and calcified thrombi, and its wall consisted of collagenous fibrous tissue. Immunohistochemically, a monolayer of flat cells lining the cyst was confirmed as endothelium using antibodies to von Willebrand factor and CD34, as well as UEA-I lectin. To the best of our knowledge, blood cysts of the pulmonary valve are rare and only 10 such cases have been reported, including six pediatric cases. This case is the oldest and fifth adult patient with a blood cyst found on the pulmonary valve. A possible histogenesis is discussed.

Morphologic aspects and morphogenesis of blood cysts on canine cardiac valves

We investigated retrospectively the morphologic aspects of blood cysts of the atrioventricular valve in eight Beagle dogs and clarified the morphogenesis of the lesions. Study of serial sections revealed that the cysts communicate with the blood vessels; however, they showed no connection with the valve surface. Immunohistochemically, the thin endothelium of the lesions showed positive staining for factor VIII-related antigen. Histologic studies of a variety of sizes of blood cysts revealed four basic stages of blood cyst formation: 1) initially, the involved blood vessel undergoes only a slight enlargement that is not grossly detectable; 2) next, the vessel becomes moderately or markedly dilated and contains a large number of erythrocytes. The changes of this stage are macroscopically detectable; and 3) then, blood flow is arrested partly in the cystic lesion, followed by degeneration and necrosis of the cyst. At this third stage, fibrous tissue or dense collagenous connective tissue is usually seen surrounding the cyst; 4) and finally, metaplastic bone is formed within the lesion. Colloidal carbon infusion into the valves of normal canine hearts revealed the presence of an extensive, dense arrangement of blood vessels in the septal leaflet of the tricuspid valve, which usually is the recognized site to develop blood cysts.

Macromolecular transport within heart valves

The present study documents the permeability characteristics of heart valvular endothelium to low-density lipoprotein (LDL), albumin, and horseradish peroxidase (HRP). Using quantitative autoradiography, LDL and albumin concentrations were measured within aortic valves of squirrel monkeys and rabbits after 30 minutes of in vivo circulation. The valvular concentration profiles were analyzed using theoretical mathematical models based on fundamental transport principles. In vivo transvalvular concentration profiles of LDL and albumin displayed the highest tissue concentrations immediately beneath the endothelium and displayed the lowest concentrations near the midline of the valve. Tissue concentrations of LDL and albumin displayed large differences in magnitudes between different regions of individual valve leaflets suggesting marked spatial variation in the permeability properties of the valvular endothelium to LDL and albumin; this was also seen visually with HRP. The results of the theoretical analysis showed that 1) the aortic valvular endothelium limits the uptake of LDL and albumin into the valvular tissue, 2) the permeability of the valvular endothelium differs widely from one region of a valve to another and even from one side of the valve to the other within a single valvular region, and 3) intramural diffusion is the predominant mode of transport for LDL and albumin within the aortic valve, even in valvular regions exposed to large pressure differences across the valve.