Twenty-four pigeons learned a successive discrimination between 500 mmu (S+) and 574 mmu (S-). When tested in extinction, some birds received stimuli around S+, with no S- presentations. These birds showed a positive peak shift, with maximum responding not at 550 mmu, but displaced to 538 mmu and 544 mmu. Other birds were tested with stimuli around S-, with no S+ presentations. These birds showed a negative shift, with least responding not at 574 mmu, but at 586 mmu. Though the first group was tested around S+ and the second around S-, total responding between groups did not differ. When retested on the other half of the continuum, however, birds that had gone from the S+ half to the S- half responded fewer times than those that had gone from the S- half to the S+ half. In a second experiment, reducing stimulus spacing from 6 mmu to 2 mmu produced flatter gradients and decreased the amount of positive shift. In a third experiment, birds were tested across the whole continuum with stimuli presented in serial order. A sequence from 538 mmu to 586 mmu produced no responding after the first part of the session; a sequence from 586 mmu to 538 mmu produced responding throughout the session.

Animals↗

PubMedDate not supplied

Experience with qualitative and quantitative applications of Doppler echocardiography in congenital heart disease.

The increasing popularity of Doppler echocardiography in recent years has stemmed from the combination of Doppler with two-dimensional echocardiography, and from the Doppler capability for flow velocity measurement. In the past decade, Doppler instrumentation has evolved from single probe A- and M-mode systems with non-quantitative Doppler output, into multi-faceted instruments combining two-dimensional echo, M-mode echo, with both pulsed and continuous wave Doppler. In the field of pediatric cardiology, quantitative Doppler applications have proven most useful in noninvasive measurement of the severity of obstruction at aortic and pulmonic valves, and across pulmonary artery bands. High accuracy is enjoyed using either continuous wave, or high pulse repetition pulsed wave, Doppler. Additional quantitative applications include estimation of volume aortic flow (cardiac output), and comparison with volume pulmonic flow (pulmonary to systemic flow ratio). Through evaluation of specific disturbances of blood flow (timing, location, direction, duration), qualitative aspects of Doppler continue to provide sensitive and specific diagnosis of valvular disease, as well as shunt lesions such as atrial and ventricular septal defect, and patent ductus arteriosus. Qualitative Doppler offers 'semi-quantitation' of the severity of lesions based on demonstration of breadth and extent of the individual flow disturbances. The addition of Doppler flow information to the information available from conventional M-mode and two-dimensional echo has led to a comprehensive cardiac ultrasound capability. Information previously available only from invasive study (severity of gradient, shunt, regurgitation) is now available noninvasively; the impact upon current and long-term aspects of patient care should prove considerable.

Aortic Valve Insufficiency↗

PubMedDate not supplied

Transesophageal echocardiography during repair of congenital cardiac defects: identification of residual problems necessitating reoperation.

One advantage of intraoperative transesophageal echocardiographic (TEE) evaluation during surgery for congenital heart disease is detection of suboptimal repairs, thus providing the opportunity to return to cardiopulmonary bypass (CPB) to repair residual defects. The purpose of this study was to evaluate the impact of TEE on decisions to return to CPB. Two-hundred-thirty infants and children with a variety of defects were studied with size-appropriate TEE probes. Patients were grouped by anatomic defect or surgical procedure for which TEE was requested. After CPB, pre- and post-CPB TEE anatomic, functional, and flow evaluations were compared. TEE findings prompted a return to CPB to repair residual defects in 17 of 230 (7.4%) patients. By diagnosis, return to CPB occurred in 9 of 28 (32%) patients with left ventricular outflow tract obstruction, 5 of 78 (6.4%) patients with ventricular septal defect, 1 of 16 (6%) patients with switch-repaired transposition, 1 of 32 (3%) with aortic valve disease, and 1 of 3 with double outlet right ventricle. All post-CPB diagnoses were confirmed during reoperation. Although post-CPB TEE provided reassuring information in patients with other diagnoses, TEE impact on return to CPB appears to be significant in a small group of primary diagnoses. The sensitivity and specificity of TEE determination of the need for reoperation were 89% and 100%, respectively. By identifying the site, severity, and mechanism of residual problems, TEE offers substantial utility in detection of residual problems in need of reoperation.

Adolescent↗

PubMedDate not supplied

Guidelines for transesophageal echocardiography in children.

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Child↗

PubMedDate not supplied

Video viewing as an alternative to sedation for young subjects who have cardiac ultrasound examinations.

Sedation is often required for extended or quantitative echocardiographic examination of young patients. To test the hypothesis that patient viewing of entertaining videotapes during echocardiographic examinations would reduce the need for sedation and that Doppler pressure gradients so obtained would correspond satisfactorily with subsequent catheterization pressure gradients, 38 patients (age, 5 to 64 months; mean age, 18.6 months) with a variety of cardiac defects were studied. Because of excessive activity, resistance, fear, or crying, all of these patients would have normally been sedated. Instead, an age-appropriate videotape was used for patient viewing. In 35 of 38 patients, complete examinations were obtained with video viewing with no sedation. Twelve study patients later underwent catheterization while receiving sedation. The Doppler pressure gradients obtained while patients were viewing videotapes corresponded well with catheterization (r = 0.94). However, those pressure gradients were higher than those obtained with catheterization (mean, 8.3 mm Hg), but there was only one significant discrepancy of 22 mm Hg. In this series, complete examinations were obtained without sedation in 92% of subjects who would have normally required sedation (p less than 0.001), with minimal reduction in the accuracy of prediction of subsequent sedated catheterization pressure gradients. This suggests that near baseline conditions existed while patients were viewing television. Video viewing during echocardiographic examinations appears to be advantageous.

Cardiac Catheterization↗

PubMedDate not supplied

Left ventricular outflow tract obstruction: an indication for intraoperative transesophageal echocardiography.

Transesophageal echocardiography (TEE) provides detailed anatomic imaging of both discrete and complex forms of left ventricular outflow tract (LVOT) obstruction, and Doppler techniques provide additional information regarding the site, mechanism, and severity of the obstruction. Because the transaortic surgical approach to LVOT obstruction often provides limited direct visualization during surgery, we sought to evaluate the utility of intraoperative TEE during surgery for LVOT obstruction. We tested the hypotheses that intraoperative TEE would (1) be useful in defining the level and nature of LVOT obstruction, (2) serve to direct the surgical approach, (3) define the adequacy of relief of LVOT obstruction, and (4) detect surgical complications. Study population consisted of a consecutive series of 27 infants and children undergoing surgery for LVOT obstruction. Patient age ranged from 0.5 to 17.9 years, and weight from 5.4 to 71.2 kg. In 14 patients LVOT obstruction resulted from a discrete membrane, whereas 13 had complex forms of LVOT obstruction. Fully anesthetized and monitored patients were examined with 5 MHz TEE probes appropriate to the size of the patient. In the 14 patients with discrete LVOT obstruction, discrete membranes were identified by TEE in all; gradients ranged from 36 to 75 mm Hg. In 13 of 14 patients, postbypass TEE demonstrated removal of the membrane and excellent relief of gradients. In one of these patients, TEE demonstrated a small ventricular septal defect acquired during resection; the patient was returned to bypass for closure. In one patient, return to bypass for further resection of LVOT obstruction was prompted by TEE demonstration of a high residual gradient. In the 13 patients with complex LVOT obstruction, TEE demonstrated the complexity of LVOT obstruction in all. Gradients ranged from 4 to 95 mm Hg. Although this information was used in surgical planning, five patients had high residual gradients after bypass and underwent further resection. An additional two were returned to bypass for mitral valve replacement. Overall, 8 of 27 patients (29.6%) were returned to bypass based on TEE demonstration of residual anatomic or hemodynamic abnormalities. This occurred significantly more frequently in complex LVOT obstruction than in discrete LVOT obstruction (p = 0.045). We conclude that intraoperative TEE has substantial utility in the demonstration of site, mechanism, and severity of LVOT obstruction and for surgery designed to relieve LVOT obstruction. We believe that TEE should be an integral part of surgical management of LVOT obstruction.

Adolescent↗

PubMedDate not supplied

Guidelines for physician training in transesophageal echocardiography: recommendations of the American Society of Echocardiography Committee for Physician Training in Echocardiography.

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Echocardiography↗