We describe original histologic findings of left ventricle papillary muscle (LVPM) arteries in people under 30 years of age. We examined 666 samples taken from the tip, mid-portion and base of papillary muscles in 56 males and 55 females, as well as several samples from the rest of the left ventricle. The number of smooth muscle cells (SMC) in the tunica media of the LVPM arteries led us to divide the samples examined into three groups: (i) group 1, 355 samples (53%) with a normal number of SMC and a normal lumen (the number of group 1 samples increased from the tip (21%) to the base (47%)); (ii) group 2, 252 samples (38%) with a mild to moderately increased number of SMC (the number of these samples decreased from the tip (44%) to the base (22%)); and (iii) group 3, 59 samples (9%) with abundant SMC that were more than twofold greater in size and number of normal arteries, in contrast with the other two groups. The shape of the SMC in group 3 samples was round and the extremely narrow, centrally located lumen of these SMCE had a round or oval shape. These changes were restricted only to papillary muscle arteries and the number of group 3 samples decreased from the tip (63%) to the mid-portion (37%). No inflammatory reaction or chronic ischemic changes were found in the LVPM arteries and surrounding area. The SMC changes in groups 2 and 3 were found in subjects aged more than 2 months. These findings will provide anatomists, cardiologists, pathologists and physiologists with valuable knowledge and will trigger further investigation into the etiology of the structural changes observed and their evolution with age.

In this study we describe original histologic findingsof the right ventricle papillary muscle (PM) arteries in people under 30 years old. We examined 666 samples taken from the tip, mid-portion, and base of the PM in 56 males and 55 females, as well as samples from the rest of the right ventricle. The amount of smooth muscle cell (SMC) fibersin the tunica media (TM) led to their division into three groups: Group 1: 351 samples (53%); normal amount, normal lumen. The amount of SMCs increased from the tip (20%) to the base (48%). Group 2: 226 samples (34%); mild to moderately increased amount of SMCs, with narrowness, eccentric displacement, and uneven lumen shape. They decreased from the tip (42%) to the base (23%). Group 3: 89 samples (13%), with abundant SMCs that duplicated the arterial size, contrary to the other two groups. Their shape was round and their extremely narrow, centrally located lumen had a round or oval shape. These changes were restricted only to PM arteries and decreased from the tip (65%) to the mid-portion (35%). This type of artery predominated compared to the other two groups, probably because of the narrow lumen. No inflammatoryreaction or chronic ischemic changes were found in the PM and its arteries. The SMC changes in groups 2 and 3 were found in subjects older than 2 months. The above findingswill provide anatomists, cardiologists, and physiologists with valuable knowledge. Anat Key words: heart; papillar y muscles; papillar y arteries; tunica media; interstitial fibrosis During our previous study (Nerantzis et al., 1994), of the right ventricle posterior papillary muscle (PM) arteries, in which we examined whether the posterior right diagonal artery, supplied them with blood, we frequently observed unusual arterial changes, although a large number of the tissue samples were from very young patients. These changes consisted of variable amounts of smooth muscle cell (SMC) fibers of the tunica media (TM). In some of these PM arteries, the SMCs were abundant, presenting a significantlythick wall associated with remarkably narrow, almost obstructed lumen.The goal of the current study was to describe in detail the histology of the right ventricle PM arteries, in order to assess the amount of SMCs in the TM in samples taken from young subjects. Information was also gathered on perivascular and interstitial fibrosis,the status of the intima and adventitia of PM arteries, and the anatomical configurationof PM.We also examined samples from other regions of the right ventricle, to confirmsimilar histologic findingsregarding the amount of SMCs observed in the PM arteries.To the best of our knowledge there is no similar study in the literature.We are certain that these detailed anatomical-histological findingsconcerning the right ventricle PM and its

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We describe histologically cases of patients between 31 and 60 years of age who had fibromuscular dysplasia (FMD) in the tunica media (TM) of the left ventricle papillary muscles (PM) arteries. We also compared them with our previous findings in subjects younger than 30 years of age. We examined histologically samples taken from the tip of the anterior PM of the left ventricle in 200 healthy male hearts. In 33 cases (16.5 %), FMD was in the TM. We divided these cases into three subgroups (A, B, C) based on the degree of replacement of smooth muscle cells by fibrous tissue, and thus identified 17, 11 and 5 cases, respectively. Until the age of 41, the typical lesions were often localized within the TM. Beyond that age, the fibrous tissue increased in the TM wall and in the surrounding area of the vessels, causing dysfunction of the PM. Degenerative lesions, as well as inflammatory infiltration, were found after the age of 53. The findings of this study will be useful to cardiologists and cardiac surgeons, in pointing out that, after the age of 44 years old, some PM and their supporting valves may present a degree of dysfunction.