Aneurysm induced by periarterial application of elastase heals spontaneously.

BACKGROUND: The pathogenesis of aortic aneurysms remains largely unknown, despite aneurysmal rupture being an increasingly common catastrophe. METHODS: This study was designed to elucidate the mechanism of arterial dilatation histologically and electron microscopically, utilising a new animal model. Elastase, 3.0 mg/ml, was applied to the abdominal aortae of 18 New Zealand white rabbits from the adventitia side for 3 hours. The rabbits were sacrificed at 0, 3, 14, 28, 42 and 90 days after the procedure (n=4, 3, 2, 2, 2, 3). RESULTS: Two rabbits were found to have developed aortic rupture. On day 0, elastase application induced fusiform aneurysms up to 1.62+/-0.14 times the pre-elastase application aortic diameter. Dilated walls revealed medial elastolysis, degeneration of smooth muscle cells (SMCs) and damaged endothelial cells. By day 3, the smooth muscle cells had changed to the synthetic type. Aneurysms did not progress, and after 42 days, showed gradual shrinkage. By day 90, aortic diameters had nearly normalised. CONCLUSIONS: Aortic walls also returned to the pre-elastase application thickness and some mature medial elastic lamellae showed regeneration. Medial smooth muscle cells reverted to the contractile type. Aortic dilatation induced by peri-aortic application of elastase heals spontaneously, accompanied by regeneration of smooth muscle cells. Irreversible degeneration of medial smooth muscle cells appears to be more critical to aneurysm formation than degeneration of elastic lamellae.

[Pathology and histochemistry of mitral valve prolapse].

UNLABELLED: To analyze the myxomatous changes and the components of acidic glycosaminoglycans (GAG) of the mitral valve in aged patients with the mitral valve prolapse (MVP) syndrome, a pathological and histochemical study was performed on hearts of 18 autopsied cases with MVP. The histochemical study included toluidine blue Ohno's method, and 3 enzymatic digestion tests with streptomyces hyaluronidase, chondroitinase AC-II and chondroitinase ABC. The following results were obtained: 1. The incidence of MVP with mitral regurgitation among 2,060 elderly autopsy patients over 60 years of age was 0.87%. 2. PATHOLOGICAL FINDINGS: marked prolapse was detected in the anterior leaflet of 3 patients, moderate prolapse in the anterior leaflet of 6 and moderate prolapse in the posterior leaflet of 5. Most patients showed greater prolapse in the anterior than in the posterior leaflets. The MVP of 11 patients (61%) was associated with tricuspid valve prolapse. 3. Histological findings: All cases exhibited thickening at the rough zone; 17 patients showed enlargement of the spongiosa layer, and 15 showed a decrease or disappearance of the fibrosa layer. All cases showed various degrees of change in the atrialis layer. The main site of myxomatous change in the mitral valve of MVP was the spongiosa layer of the rough zone. 4. Histochemical findings: Results using 3 methods of enzymatic digestion tests were positive in 13 patients, which suggested that the major component of increased GAG at the myxomatous changes in the mitral valve of MVP was hyaluronic acid, as did the results with Ohno's toluidine blue method.

[Morphological observation of the mitral annulus fibrosus (II)].

In 1986, Hutchins observed a high incidence of the disjunction of the mitral annulus fibrosus in mitral valve prolapse syndrome. However, we could not prove his view in our previous study using one section in each case. In this study, the types of mitral annulus fibrosus were analyzed in plural sections. Autopsy hearts of nine aged cases were used for examination of the mitral annulus fibrosus in five to eight longitudinal sections from the posterolateral wall. The types of the mitral annulus fibrosus were classified as; Type A (the mitral valve attaches to the left ventricle), Type B (the valve attaches to the left atrium), Type C (the atrialis layer of the valve continues to the left atrium, while the fibrosa layer continues to the left ventricle), and type D (mitral annulus calcification). A1-3 and B1-3 are subtypes. In the nine cases there were no consistent patterns in type distributions. All sections showed Type A1 (Case 2), Type A1 to A3 (Case 5), and Type B1 to B3 (Case 8). In other cases, a combination of Type A and B (Case 4, 6, 7, 9), and inclusion of Type C (Case 1) and Type D (Case 3) were found. The location of the middle scallop of the posterior mitral leaflet corresponded to the section of the previous study. Among three cases of Type A in the middle scallop, two showed Type A in every section. Among five cases of Type B in the middle scallop, only one case showed Type B in every section. Other four cases showed various combinations with the other types. A case of Type D in the middle scallop showed also Type B and Type C. The conclusion of this study was that in 1/3 of the cases, the type of the mitral annulus fibrosus was consistent, but in the other 2/3 they were not consistent. In other words, one section is not necessarily representative of the morphology of the mitral annulus fibrosus in each case.

[Morphological observation of the mitral annulus fibrosus in patients with mitral valve prolapse].

Sixteen cases of mitral valve prolapse (MVP) with mitral regurgitation (MR) in the aged (mainly in their eighth and ninth decades) with both clinical and pathological evidences were investigated. One hundred autopsy cases served as the control. The longitudinally-sectioned mitral annulus fibrosus was pathologically studied in all with special reference to the atrium-valve disjunction reported by Hutchins. Morphologically, the mitral annulus fibrosus was classified either as type A (the mitral valve attaches to the left ventricle), type B (the mitral valve attaches to the left atrium: Hutchins' disjunction), type C (the atrialis continues to the left atrium and the fibrosa to the left ventricle), or type D (mitral annulus calcification). Type B was observed in only 31% of the MVP cases, whereas it was seen in 43% of the control cases. It was concluded that Hutchins' observation could not be regarded as the characteristic pathological finding of MVP.

A clinicopathological study on 25 cases of complete left bundle branch block.

A total of 25 cases (12 men, 13 women) of complete left bundle branch block (LBBB) were found among 1,400 consecutive autopsy in the aged. Their ages ranged from 70 to 86 years (average 78.9). ECG was analyzed as for the occurrence of LBBB and myocardial infarction (MI). Pathological examinations included observations of the conduction system by serial sections. They were divided into group A with MI and group B without MI. Duration of LBBB was 1 to 3 days in 4 cases, more than 1 month in 7, and more than 1 year in 14. From the temporal sequence of LBBB and MI in group A, cases were classified into (1) MI preceding LBBB in 5, (2) both coexistent in 5, and (3) LBBB preceding MI in 1. There were 8 cases of normal electrical axis, 17 left axis deviation, 7 first degree A-V block, and 2 atrial fibrillation. Various heart diseases were underlying in 21 cases, including hypertension, MI, mitral and aortic regurgitation, and primary myocardial disease, and there were 4 cases with no cardiac diseases. Cause of death was cardiac in 12; MI, congestive heart failure, and sudden death. Heart weight was 410 Gm on the average (240 to 550 Gm). MI was found in 11, with stenotic index of 12/15, while it was 9/15 in group B. Lesions of the conduction system were slight to moderate (1.5 to 2.4) except left bundle branch, which showed marked changes in posterior (4.9) and anterior (4.8) fascicles. Site of interruption of the left bundle branch was the junction between the branching portion of the A-V bundle and the left bundle branch (Junctional type) in 17, and peripheral portion of the left bundle branch about 10 mm or more below the junction in 8 (Peripheral type). In conclusion, 2/3 of cases of LBBB belonged to the junctional type and most of them were not related to MI, but to the lesions caused by mechanical injuries at the septal summit. One third of the cases were as peripheral type, which was mainly related to the various types of lesions including septal ischemia (necrosis and fibrosis).