Edwards, 1971;Gomes and McGoon, 1971;Mair et al., 1974;Bharati et al., 1974).In addition, the morphological study of a lesion such as truncus arteriosus communis, in which partial or complete absence of division of the conotruncus is present, may help to clarify which developmental structures take part in the septation of the outflow tracts of the normal heart. With this in mind, we have also examined cases presentina with aortopulmonary septal defect or conal ventricular septal defect which are developmentally related to truncus arteriosus. Definition of termsThe term conus, embryogenetically, refers to the middle third of the bulbus cordis; it is formed by free walls (parietal conus) and by septum (conal septum) derived from the fusion of the conus ridges. Anatomically, the conus corresponds to the outflow tracts of both ventricles and conventionally it refers to the muscular cardiac segments interposed between the semilunar and atrioventricular valves; the conal septum is that portion of the ventricular septum which separates the ventricular infundibula. In the early stages of cardiac development, the atrioventricular channel is separated from the semilunar valves by the parietal conus; a process of differential absorption leads to direct fibrous continuity between mitral and aortic valves, while

Hemorheological parameters (viscosity of whole blood, plasma viscosity, hematocrit, velocity of red blood cells) were studied in 30 patients with coronary artery disease (15 patients with acute myocardial infarction, 15 patients with chronic angina), 14 subjects at high risk for ischemic heart disease and 14 normal volunteers matched for sex and age. Viscosity of whole blood was high in all coronary disease patients and in high-risk subjects as compared with controls. Velocity of red blood cells was significantly decreased in these patients. On the other hand, plasma viscosity and fibrinogen values were in the normal range in both groups and hematocrit was only slightly elevated in patients with angina. Furthermore, there were no changes in rheological parameters during the period of observation (1 week). We can suppose that the hyperviscosity is due, above all, to the decreased red blood cell deformability both in coronary disease patients but also in high-risk subjects. It is probable that red blood cell damage is present before the acute ischemic event, and that is a preexisting cause and not a consequence of it.

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