The morphology of 50 normal tricuspid valves was studied. The surface of the leaflets was divided into three zones: (1) the rough zone, into which most of the chordae tendineae are inserted, (2) the basal zone, and (3) the clear zone, which lies between the rough and basal zones.Five types of chordae were distinguished by their morphology and mode of insertion: fan-shaped, rough zone, basal, free edge, and deep chordae. The last two types are unique to the tricuspid valve.If fan-shaped chordae, used to define the commissures between the leaflets, are absent, other landmarks may be used for commissural definition. Once defined, all tissue between the commissures was regarded as part of the anterior, posterior, or septal leaflet. The recognition that the free edges of the anterior and septal leaflets contain notches, that rough zone chordae insert into them, and that the posterior leaflet has scallops further aids identification of a leaflet's components. Thus, structures formerly regarded as accessory leaflets were incorporated into one of the three leaflets.RECENTLY, we have reexamined the morphology of the mitral valve and have been able to establish a better clinicopathologic correlation in various types of mitral valve abnormality. By identifying the specific fan-shaped chordae tendineae attached to the mitral valve, we were able to delineate the commissural areas clearly and to divide the valve into anterior and posterior leaflets. We were, thus, also able to identify the clefts of the posterior leaflet and to distinguish them from the true commissures.1 2 This definition of mitral valve anatomy eliminates the need to postulate accessory leaflets of the mitral valve. It proved valuable in enhancing clinicopathologic understanding of the syndrome of mitral regurgitation due to prolapse of the posterior leaflet.3

Fifty normal mitral valves from adults were studied. Commissures, identified by commissural chordae tendineae and the tips of papillary muscles, partition the mitral valvular tissue into anterior and posterior leaflets. This definition incorporates into the posterior leaflet the structures formerly regarded as accessory leaflets. The posterior leaflet is further divided into scallops by clefts in its tissue. Cleft chordae provide a guide to these interscallop indentations or clefts. Partitioned this way, the posterior leaflet was tri-scalloped in 46 hearts. In 42, a large middle scallop was present with two smaller scallops on either side. Rough and clear zones can be defined on the anterior leaflet and rough, clear, and basal zones on the posterior leaflet. Additional Indexing Words: Commissure Prolapsed mitral valve Chordae tendineae Mitral regurgitation

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Chordae tendineae from 50 normal mitral valves were studied. Four main types can be distinguished by their mode of insertion. Commissural chordae insert into and define the commissures between the anterior and posterior leaflets. Rough zone chordae insert into the ventricular aspect of the distal rough portion of the anterior and posterior leaflets. Such rough zone chordae typically split into three cords before inserting into the leaflet. Two of the anterior leaflet rough zone chordae are thicker than the others and are called strut chordae. They insert at 4 and 8 o'clock positions on the semicircular anterior leaflet. Cleft chordae insert into and define the clefts between the scallops of the posterior leaflet. Basal chordae are single strands that arise from the posterior ventricular wall and insert into the basal zone of the posterior leaflet. This classification permits a clear definition of mitral valve anatomy and forms a sound basis for functional studies of chordae tendineae.

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SUMMARY Focal cerebral ischemia hi humans increases the Incidence of cardiac arrhythmias, and serum cardiac enzyme and plasma norepinephrine levels. In addition, systemic administration of catecholamines causes myocardial damage. This suggests that cerebral ischemia may cause myocardial damage as a consequence of elevated plasma norepinephrine levels. Therefore, experiments were done hi 23 chloralosed, paralyzed and artificially ventilated cats to investigate the effects of occluding (n = 17) or sham-occluding (n = 6) the left middle cerebral artery on the myocardium and on circulating levels of plasma catecholamines. After occlusion of the middle cerebral artery for 12-22 hr, 41% (7/17) of the hearts had either acute myocardial necrosis (3/7), focal hemorrhage (3/7), or both (177). In anlmah with acute myocardial damage the levels of plasma norepinephrine and epinephrine were significantly increased compared to pre-middle cerebral artery occlusion values ( + 46 ± 18% and +142 ± 45%, respectively). As well, meats with acute myocardial damage, changes from initial levels of plasma norepinephrine and epinephrine were significantly Increased over those of experimental cats without acute myocardial damage. In animals which did not have acute myocardial damage (10/17) the circulating plasma levels of catecholamines were not significantly different from pre-occlusion values. Similarly, sham occlusion did not alter plasma catecholamine levels. These data demonstrate that a percentage of animals subjected to middle cerebral artery occlusion have myocardial damage and an increase hi plasma concentration of norepinephrine and epinephrine. This suggests that a rise hi plasma catecholamine levels, due to Increased sympathetic activity after middle cerebral artery occlusion, may cause myocardial damage. Stroke Vol 17, No 3, 1986 PATIENTS who begin to recover neurologically after a stroke may perish unexpectedly from cardiac complications or sudden death.1 Although some of these deaths could be attributed to concomitant heart disease, stroke patients have an excess of cardiac arrhythmias, increased cardiac serum enzymes and raised plasma catecholamines when compared to similarly managed controls matched for age, sex and the presence of heart disease. "5 Some patients dying from stroke show myocardial lesions, 6 similar to those observed in animals infused with catecholamines 718 and in animals with increased intracranial pressure, 9 or intracranial hemorrhage. "12 Taken together, these findings suggest that raised levels of catecholamines after cerebral ischemia, likely from increased sympathetic activity, contribute to myocardial damage. The present study was done to determine whether focal cerebral ischemia in the cat would produce cardiac lesions and whether changes in plasma levels of catecholamines were associated with the cardiac lesions. Methods Experiments were done in 23 adult cats of either sex weighing 2.0 to 3.5 kg. To isolate the middle cerebral artery (MCA) animals were anesthetized either with sodium pentoba...