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The purpose of this study was to evaluate the effectiveness and complications of several types of anticoagulant therapy in children with prosthetic valves. During a 7-year period ending April 1985, 130 children aged 1 to 19 years underwent left-sided valve replacement. Operative mortality was 3%, 5%, and 9%, respectively, for aortic, mitral, and aortic and mitral valve replacement. Among the 123 survivors, 32 (26%) had had aortic, 71 (58%) had had mitral, and 20 (16%) had had aortic and mitral valve replacement. Follow-up ranged from 2 months to 8.2 years, a total of 544 patient-years. The survivors were divided into three groups based on anticoagulant treatment: warfarin sodium, aspirin plus dipyridamole, and no anticoagulants. Among the patients who had aortic valve replacement, thromboembolic complications developed in 2.5% (2.5/100 patient-years) of the aspirin plus dipyridamole group and 5% of the group given no anticoagulants. Only the warfarin group (4%) experienced bleeding complications. Among the patients having mitral valve replacement, thromboembolic complications developed in 4% of the warfarin group, 3% of the aspirin plus dipyridamole group, and 11% of the no anticoagulant group. In addition, 2% of patients in the warfarin group experienced severe bleeding. Two fatal cerebrovascular accidents occurred, both in the aspirin plus dipyridamole group. Patients who received a mitral heterograft were not prescribed any anticoagulant medications, and no thromboembolic complications developed. Among patients having double-valve replacement, complications developed in 5% of the warfarin group and 27% of the group given no anticoagulants.(ABSTRACT TRUNCATED AT 250 WORDS)

Ten children, aged six weeks to 13 years, without intracardiac shunts or lesions that could cause turbulent flow in the ascending aorta or aortic regurgitation, underwent cardiac catheterization, including cardiac output measurements by thermodilution. Simultaneously with each of six consecutive thermodilution injections, mean and maximal blood velocities in the ascending aorta were measured by pulsed Doppler echocardiography from the suprasternal notch. Aortic root and aortic orifice diameters were measured with M-mode and cross-sectional echocardiography. One patient had to be excluded from the analysis because of inadequate Doppler recordings. The best agreement with the results of the thermodilution was observed when internal systolic aortic root diameter was combined with mean velocity (r = 0.97, y = 0.90x + 0.28, SEE = 0.31 liters/min). When cardiac output was normalized for body size, there was still a good correlation between the results of these two methods.

Two beams incident upon a bismuth silicon oxide crystal are shown to give rise to a subharmonic halfway between the incident beams and to an oscillating beam in a ring resonator. It is further shown that the two beams arising are in competition with each other: the subharmonic power rises when the oscillating beam declines owing to damping of the resonator.

Variables obtained with the forced oscillation technique (total respiratory resistance and impedance at 2, 4 and 12 Hz) and with the forced vital capacity manoeuvre (FVC, FEV1, MMEF, MEF75, MEF50, MEF25) were used in the evaluation of the bronchial allergen challenge test in 2 groups of asthmatic children. Each method was applied in 15 provocation tests and the changes of the different variables, allowing for their respective variations, were compared with the clinical assessment. Agreement with the clinical evaluation was found in 15 of 15 occasions with the forced oscillation technique and in 12 of 15 occasions with the forced vital capacity manoeuvre. With the forced oscillation technique a bronchial reaction was detected in 6 of 10 patients at 1/10 of the allergen concentration that gave positive clinical signs and the single most sensitive variable was resistance determination at 4 Hz, with significant change in 5 of 10 cases. The forced vital capacity manoeuvre allowed detection of a bronchial reaction preceding clinical signs at a tenfold lower allergen concentration in 2 of 9 cases and the most sensitive variables were FEV1 and MEF25.

Two hundred eighteen healthy children aged 2 to 18 years were studied using a modification of the forced oscillation technique. Reference values with height as predictor were determined for total respiratory resistance and impedance during inspiration, expiration, and throughout the whole respiratory cycle at an oscillation frequency of 4 Hz and, in a subpopulation of 61 children, at frequencies of 2 and 12 Hz. Mean total inspiratory resistance, determined at 4 Hz, decreased with growth from 1.3 kPa X 1(-1) X s at 2 years of age to 0.3 kPa X 1(-1) X s at 18 years. Variability in the results between individuals, expressed in terms of coefficient of variation, was found to be +27% and -21%, respectively, and within individuals, 9%. Resistance during expiration was on average 16% higher than during inspiration and the variability within individuals was 11%. A marked decrease in resistance was found in small children when the frequency was increased from 2 to 12 Hz. The frequency dependence of respiratory resistance observed in small children changes gradually with growth, in parallel with the reduction of total respiratory resistance, to an adult pattern in which no significant change in resistance can be noted between frequencies of 2 and 12 Hz.