Faculty Bibliography

Left and right atrial isomerism, comprising congenital heart defects with disturbances in normal left-right asymmetry, are phenotypically distinct after birth, although animal models suggest a common embryologic origin. We postulated that the prenatal phenotype may indeed be similar in both syndromes but that differential fetal loss is responsible for the distinct postnatal phenotypes. Distinctive fetal echocardiographic features of these syndromes have not been described in detail. We therefore sought markers of left atrial isomerism that could be recognized prenatally by echocardiography and compared our results with postnatal data to identify unique intrauterine features. We reviewed 10 cases at our center and 28 published cases of cardiac malformations with atrial isomerism detected by fetal echocardiography. Postnatal imaging and autopsies provided definitive diagnoses. Ninety-five percent of cases exhibited left atrial isomerism and formed the primary study population. Echocardiographic markers included a large azygos continuation of an interrupted inferior vena cava, atrioventricular block with structural heart disease, and viscerocardiac heterotaxy. At least 1 of these markers was seen in all of our center's cases. The incidences of most cardiac lesions detected prenatally were similar to those detected postnatally. However, although the incidences of atrioventricular septal defect and pulmonary outflow obstruction in live births were 50% and 45%, respectively, they were found much more frequently among stillbirths (80% each). In summary, we identified key fetal echocardiographic features highly sensitive for left atrial isomerism. Fetal loss selects against certain lesions such as atrioventricular septal defect. The spectrum of cardiac disease suggests a greater primitivity of the fetal heart than previously shown; the typical cardiac phenotypes are closer to right atrial isomerism than are their extrauterine presentations

Asplenia syndrome is characterized by complex congenital heart defects, asplenia and abdominal heterotaxy. Recent interest in the syndrome has been increased by new knowledge arising from animal models and by continuing improvements in surgical outcome in childhood. To further elucidate the embryologic timing and mechanisms of the asplenia syndrome, 32 necropsy cases were reviewed and 487 published autopsy cases were reanalyzed at the hospital. The most common congenital heart defects were atrial septal defects, common atrioventricular canals and conotruncal anomalies. With use of current information on the timing of normal development, it was hypothesized that most defects originate at Streeter Horizon XIII; patients averaged 3.2 Horizon XIII defects, more than at any other stage. Distribution was unimodal. Extracardiac anomalies also exhibited a developmental spectrum. Because the normal spleen develops by Horizon XIII, asplenia, the sine qua non of the syndrome, originates then or earlier. Abnormal pulmonary lobation occurred in 80% of cases, with right isomerism occurring most often; pulmonary branching asymmetry also originates at or before Horizon XIII. Abdominal heterotaxy occurred in 72% of cases, but the timing of origin is unclear. Anomalies of other systems, including genitourinary, musculoskeletal, endocrine, and nervous systems, develop later (typically XV to XXIII); specific anomalies were less frequent, although much more prevalent than in the general population. It is concluded that asplenia syndrome is a focal developmental disturbance in laterality which occurs primarily at Horizon XIII

Deep hypothermic circulatory arrest has become an essential technique to allow repair of complex congenital cardiac lesions in children. The arrested state has concerned the surgeon, cardiologist, and anesthesiologist alike, and yet deep hypothermic circulatory arrest has been highly successful with a low incidence of neurologic sequelae. Studies of cerebral blood flow and cerebral oxygenation demonstrate that the arrest hypothermic brain does not develop the immediate postarrest hyperemia or hyperoxia seen in normothermic ischemic brain models. However, both hypothermic and normothermic ischemic brains exhibit hypoperfusion beyond the immediate recirculation period, likely coupled with a reduced cerebral metabolic rate. That the hypothermic arrested brain likely becomes anoxic and recovery of the anoxic brain depends in large part on recirculatory hemodynamics suggests that the lack of hyperemia and hyperoxia may play more major roles than was previously believed. The mechanism of protection may be related to suppression of oxygen free radicals

Ocular ultraviolet radiation (UVR) exposure was assessed in three occupational groups: fisherman, landscape workers and construction workers. The ratio of ocular exposure to ambient exposure was determined by placing UV-sensitive film (295-320 nm) between the eyes of the subjects and in a nearby open field. The mean ocular exposures varied between 2 and 17% of the ambient exposure on a horizontal surface, depending on whether subjects wore hats, the job performed and the time of year. Wearing a brimmed hat significantly reduced ocular exposure in all groups of subjects. Subjects working over more reflective surfaces had significantly higher ocular exposure. A seasonal effect on the ocular ambient exposure ratio (OAER) was also observed. These results are consistent with measurements of OAER in mannikin and measurements of surface reflectivity in this and previous studies. The results provide parameters which can be used in modeling ocular UVR exposure in epidemiological and clinical studies