Anomalous origin and course of coronary arteries in adults: identification and improved imaging utilizing transesophageal echocardiography.

Anomalous origin of a coronary artery is rare, but may represent a clinically significant abnormality, since some anomalies are associated with myocardial ischemia, infarction, and sudden death. Diagnosis may elude routine screening procedures, and even when an anomalous vessel is identified angiographically, it may be difficult to delineate its true course on the basis of angiography alone. The purpose of this study was to determine whether transesophageal echocardiography (TEE) is of value in making the diagnosis and outlining the course of anomalous coronary arteries. Five adult patients with anomalous origin of a coronary artery were studied by monoplane TEE and selective coronary angiography. Transthoracic echocardiography (TTE) was also performed in four of these five patients. Anomalous coronary ostia were visualized in four of five patients utilizing TEE, but in none of four patients by TTE. A proximal segment of the anomalous coronary vessel was identified in all five patients by TEE, and in only two of four patients by TTE. TEE images were consistently of superior diagnostic quality. TEE is a valuable tool for the echocardiographic identification of anomalous coronary arteries, and is superior to TTE in adult patients.

Development of pulmonary arteriovenous malformations after modified Fontan operations.

Two patients with complex cyanotic congenital heart disease and without previous Glenn anastomosis underwent modified Fontan operations. Postoperatively, pulmonary arteriovenous malformations developed that resulted in cyanosis from significant intrapulmonary right-to-left shunting. These malformations were detected by pulmonary angiograms and contrast echocardiograms. Pulmonary arteriovenous malformations may be a major cause of late clinical deterioration in patients treated with modified Fontan operations.

Receptive-field properties in reptilian optic tectum: some comparisons with mammals.

The receptive-field properties of single cells in the optic tectum of Iguana iguana were studied using the same procedures as have been used in this laboratory in studying its mammalian homologue, the superior colliculus. Surprisingly, despite some species-specific characteristics, the range of physiological properties of tectal and superior collicular cells appeared to be strikingly similar. This observation is not consistent with the notion that functional differences between these structures evolved as a consequence of the tremendous elaboration of mammalian neocortex and its involvement in sensory processes. The internal organization of visual tectal receptive fields was observed to be very much like that described in mammals. This included a similar distribution of on-off areas, the presence of both spatial summation and spatial inhibition within the excitatory receptive-field borders, suppressive areas just beyond these borders, and a marked tendency for habituation. In addition, many cells showed distinct directional preferences that were strongly influenced by the velocity of movement through the receptive field. Furthermore, the receptive fields of bimodal and trimodal cells showed topographic correspondences as in mammals, although the sizes of the fields were often large, thereby emphasizing the lack of an exact register between modalities. In contrast to the findings in mammals, however, a preference for stationary over moving stimuli was observed in most neurons, and specializations in iguana tectal cells representing the fovea were noted that have not been described in other species. These foveal specializations include a distinct preference for stationary over moving stimuli, the absence of directional selectivity, and the presence of a majority of cells responding at light onset only. It is suggested that the similarities in the organization and response properties of cells of the optic tectum and superior colliculus reflect the retention of ancestral characteristics through various levels of vertebrate evolution. Furthermore, the subtle species differences in the properties of these cells appear to reflect adaptations to specific ecological pressures rather than general evolutionary trends.

Sensory representation in reptilian optic tectum: some comparisons with mammals.

The sensory representations in the tectum of Iguana iguana were studied with electrophysiological recording techniques, and visual, somatic, and auditory cells were found to be represented here. These cells were not equally distributed throughout the tectal laminae. Upper tectal laminae were populated exclusively by visual cells, and deeper laminae were primarily nonvisual. The intermediate laminae had nonvisual, as well as visual, cells. Maps of the visual and somatic representations were constructed, and both representations were topographic and in register with no another. When electrical stimulation was presented via implanted electrodes, orientation responses were evoked that were predictable on the basis of the visuotopic and somatotopic maps. The organizational features of the iguana tectum are strikingly similar to those described in various mammalian species. It is suggested that the pattern of sensory and motor representation used in the midbrain of mammals is an ancient scheme that was retained during the transition from reptilian to mammalian forms more than 180 million years ago.

Reptiles and mammals use similar sensory organizations in the midbrain.

Striking similarities were observed between the overlapping visual and tactile maps of the mammalian superior colliculus and of its homolog in reptiles, the optic tectum. This topographic pattern probably represents a plan of sensory representation that existed in ancient reptiles and that was retained during the evolution to mammalian forms more than 180 million years ago.