Extracorporeal membrane oxygenation (ECMO) has been used in neonates for a variety of disease states including congenital diaphragmatic hernia, meconium aspiration syndrome, sepsis, and postoperative cardiac compromise. To our knowledge, ECMO has not been employed prior to cardiac catheterization in critical aortic stenosis (CAS). We report a neonatal case of CAS where ECMO was used early as a form of left ventricular assist to achieve adequate systemic perfusion and oxygenation and reduce myocardial ischemia. The patient was maintained on ECMO during subsequent attempts at cardiac catheterization, balloon valvuloplasty, and operative valvotomy.

Aortic Valve↗

PubMedDate not supplied

Measuring short-wavelength-sensitive cone discrimination thresholds using pseudoisochromatic figures displayed on a color monitor.

PURPOSE: To simplify the testing of short-wavelength-sensitive (SWS) cone function in the clinic. METHODS: SWS-cone discrimination thresholds were measured along the tritan axis using pseudoisochromatic figures displayed on a color monitor. A circular 6 degrees field, containing spatially discrete patches of varying sizes and luminances, was presented on a background. A subset of patches formed the target patch in the shape of a C. Eight subjects with normal color vision reported the direction of the gap in the C using a cursor controlled by a joystick. DATA: were expressed in units of SWS-cone trolands. RESULTS: SWS-cone discrimination threshold increased slowly as the SWS-cone trolands of the starting chromaticity increased. The dependence of the threshold on the SWS-cone activation level was similar to literature reports of chromatic discrimination measured with conventional paradigms. CONCLUSIONS: The advantages of this method: (a) It is a simple intuitive task for patients. (b) The paradigm can be implemented with an 8-bit/gun color monitor. (c) The test avoids the need to define equiluminance for the individual patient before the color test is administered. This method can provide a useful technique for measuring SWS-cone function in a clinical population.

Adult↗

PubMedDate not supplied

Effect of sawtooth polarity on chromatic and luminance detection.

Psychophysical studies have documented that many observers show lower thresholds for rapid-off than for rapid-on sawtooth luminance modulation. This finding, together with physiological findings from chromatically opponent ganglion cells of the macaque monkey, prompted a search for a similar bias in psychophysical detection of chromatic increments and decrements of light. Using a luminance pedestal in conjunction with a luminance background to favor detection by chromatic mechanisms, we measured spectral sensitivity for rapid-on and rapid-off sawtooth stimuli presented spatially coextensive with the pedestal. There were two different pedestal chromaticities: one broadband, and the second composed only of long-wavelength light to enhance short-wavelength-sensitive, cone-mediated detection. Spectral-sensitivity measurements for different wavelength stimuli revealed no systematic differences across the visible spectrum as a function of sawtooth waveform polarity or pedestal chromaticity. Similarly, temporal contrast-sensitivity functions for hetero-chromatically modulated red-green sawtooth stimuli did not reveal an asymmetry in sensitivity for rapid-red and rapid-green chromatic change. Some of the observers showed a higher sensitivity for luminance modulated rapid-off sawtooth stimuli, as also noted in previous studies. This asymmetry was not found when a white luminance pedestal and background was used. These results suggest that the cone inputs to chromatically opponent ON- and OFF-center cells are sufficiently balanced to provide equivalent psychophysical thresholds for chromatic increments and decrements of light.

Adult↗

PubMedDate not supplied

Computerized color-vision test based upon postreceptoral channel sensitivities.

An automated, computerized color-vision test was designed to diagnose congenital red-green color-vision defects. The observer viewed a yellow appearing CRT screen. The principle was to measure increment thresholds for three different chromaticities, the background yellow, a red, and a green chromaticity. Spatial and temporal parameters were chosen to favor parvocellular pathway mediation of thresholds. Thresholds for the three test stimuli were estimated by four-alternative forced-choice (4AFC), randomly interleaved staircases. Four 1.5-deg, 4.2 cd/m2 square pedestals were arranged as a 2 x 2 matrix around the center of the display with 15-minute separations. A trial incremented all four squares by 1.0 cd/m2 for 133 ms. One randomly chosen square included an extra increment of a test chromaticity. The observer identified the different appearing square using the cursor. Administration time was approximately 5 minutes. Normal trichromats showed clear Sloan notch as defined by log (deltaY/deltaR), whereas red-green color defectives generally showed little or no Sloan notch, indicating that their thresholds were mediated by their luminance system, not by the chromatic system. Data from 107 normal trichromats showed a mean Sloan notch of 0.654 (SD = 0.123). Among 16 color-vision defectives tested (2 protanopes, 1 protanomal, 6 deuteranopes, & 7 deuteranomals), the Sloan notch was between -0.062 and 0.353 for deutans and was < -0.10 for protans. A sufficient number of color-defective observers have not yet been tested to determine whether the test can reliably discriminate between protans and deutans. Nevertheless, the current data show that the test can work as a quick diagnostic procedure (functional trichromatism or dichromatism) of red-green color-vision defect.

Automation↗

PubMedDate not supplied

Nuclear image transmission by picturephone. Evaluation by ROC curve method.

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Decision Making↗

PubMedDate not supplied

Glutaraldehyde-fixed bovine pericardium for right ventricular outflow enlargement.

Right ventricular outflow tract enlargement using glutaraldehyde-fixed bovine pericardium was evaluated experimentally using the pig model. Twelve piglets (8-16 kg) underwent closure of surgically created, longitudinal right ventriculotomies using premeasured, round, bovine pericardial patches. Half of the animals had pulmonary artery banding to increase right sided pressures. The animals were studied an average of 5.1 months following surgery. Cardiac catheterization was performed on eight animals. Pressure measurements revealed no gradient across any outflow patch, and angiography showed no stenosis or dilatation. There was marked right ventricular hypertension in the banded animals. The hearts from all twelve animals were examined grossly and microscopically. There was endothelialization of all patches with no aneurysm formation. Measurements revealed that most patches had become oval shaped. There was no difference in patch size changes between banded and non-banded animals. The patches showed no significant size change in the longitudinal plane (average from 20.8 mm to 20.3 mm, 6.3% change); however, there was a significant decrease in the transverse size (20.8 mm to 17.3 mm, 16.0%) (p less than 0.001). The change in patch size was probably due to reshaping to conform to the longitudinal ventriculotomy and caused no narrowing. In this study, glutaraldehyde-fixed bovine pericardium appeared to be satisfactory for right ventricular outflow enlargement. Favorable qualities include ease of handling, hemostasis, and no aneurysm formation.

Animals↗