Intramyocardial microarteriopathy.

1. Two basic types of arterial vessels can be distinguished in the myocardium. a) Compacta or Ventricular Wall Type. Intramyocardial microarteries with ring musculature of the media. b) Papillary Muscle Type. Arteries with longitudinal musculature arranged as bundles in the broad media. 2. The manifestation of intramyocardial microarteriopathy differs in these vessel types. PAS-positive and elastica-rich cushion-like thickening of the intima mainly occurs in the compacta type. Arterial vessels of the trabecular portion additionally show hyperelastosis of intima and media. The degenerative lesions of the papillary muscle type are characterized by early degeneration of the smooth muscle cells and hyperfibroelastosis of intima and media. 3. Pathological vascular lesions in the compacta and papillary muscle type occur more frequently in the left ventricle, and increase with age. 4. Slight and medium lesions are in the majority. Severe vascular changes are seen in the 7th to 9th decade in about 5-10% (compacta type) and in 30-35% (papillary muscle type) respectively. 5. Hypertension seemed to raise the frequency of slight and medium lesions in the compacta type vessels. In the papillary muscle type the degenerative lesions frequently extend from the top to the bottom of the papillary muscles. 6. No significant difference between frequency and severity of vascular lesions in diabetics and in the control group could be demonstrated. 7. It appears that pathological vascular lesions occur less frequently in compacta type vessels in cases of high-grade stenosis due to extramural coronary artery sclerosis. 8. Impairment of the quality of myocardial circulation is only encountered in the presence of severe pathological vascular lesions.