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Biomedical subjects

H J Walker

Publications and source records attributed to H J Walker.

9 recordsLinked to original sources
PubMed1989

Vasodilator therapy and the anesthetist: a review of nitroprusside, labetalol, hydralazine and nitroglycerin.

Vasodilators are important adjuncts to anesthetic management in a variety of clinically encountered situations. Examples include: congestive heart failure, preeclampsia/eclampsia, management of aortic cross-clamping and treatment of perioperative hypertension. In this article, the authors review four commonly utilized vasodilating agents: sodium nitroprusside, labetalol, hydralazine and nitroglycerin. Comparisons and contrasts are made among the drugs. Each agent is presented in four sections: (1) mechanism of action, (2) indications, (3) adverse actions, and (4) dosage, administration and precautions.

Humans↗
PubMed1978

Echocardiographic estimation of aortic-valve gradient in aortic stenosis.

Fifty-five consecutive patients with aortic stenosis underwent echocardiography at the time of cardiac catheterization. Left ventricular systolic pressure was estimated from the echocardiogram assuming that peak systolic circumferential was stress was constant. Systolic blood pressure was substracted from the estimated left ventricular pressure to obtain the aortic-valve gradient. Of 44 patients with adequate echocardiograms and catheterization studies, 30 had their aortic gradient accurately estimated by the echocardiogram (r = 0.75). All 30 patients had normal left ventricular systolic function estimated echocardiographically. The echocardiogram underestimated the aortic gradient in all seven patients with poor left ventricular systolic function. An accurate echocardiographic estimate of aortic-valve gradient can be obtained in patients with normal left ventricular function. The technique can identify those patients with insignificant left ventricular outflow obstruction, thereby obviating the need for invasive studies.

Adolescent↗
PubMed1977

Interobserver variability in echocardiography.

High-quality echocardiograms were performed on 146 normal individuals whose ages ranged from 3 to 73 years (mean 27 years). Normal values for mitral diastolic excursion and E-F slope, the chamber dimensions of the right ventricle, left atrium, and left ventricle, the aortic root dimension, and thickness of the interventricular septum and left ventricular posterior wall were determined. Each tracing was then read independently by two experienced echocardiographers. The extent of interobserver variability was calculated and expressed as a percent of the mean. The 95 per cent confidence limits for these estimates were calculated. Small but significant interobserver variability was found for all nine of these commonly measured echocardiographic parameters. Observer variability is a small but potentially important consideration in investigative echocardiography.

Adolescent↗
PubMed1977

Relation between phasic mitral flow and the echocardiogram of the mitral valve in man.

Ten patients without valvular disease were studied by ventriculography, and the rate and pattern of phasic blood flow into the left ventricle were determined by ventricular volume determinations at intervals of 33 ms during a single diastolic filling period. The derived left ventricular inflow patterns were then compared with the echocardiographic mitral EF slope obtained no more than 25 minutes before left ventriculography. The steepness of the EF slope was found to be inversely correlated with the time required to reach peak inflow velocity (r = 0.80, P less than 0.01) and directly correlated with the peak left ventricular inflow velocity divided by the time required to reach peak velocity (r = 0.72, P less than 0.05). No correlation was found between mean flow velocity into the left ventricle and the EF slope (r = 0.40, P = NS). A significant inverse correlation was found between the EF slope and the fraction of the diastolic filling period elapsed when 50 per cent of the filling volume had entered the left ventricle (r = 0.85, P less than 0.01). These findings suggest that the time required to reach left ventricular peak inflow velocity is one of the determinants of the mitral EF slope.

Angiocardiography↗
PubMed1977

Hypertrophic cardiomyopathy. Evaluation by gated cardiac blood pool scanning.

The gated radionuclide cardiac blood pool scan (GCS) can be used to visualize the entire profile of the interventricular septum and left ventricular contraction. Twenty-two patients with hypertrophic cardiomyopathy, nine with valvular aortic stenosis and six normals, underwent echocardiography and GCS. All patients with hypertrophic cardiomyopathy had asymmetric septal hypertrophy and 14 of 22 had resting systolic anterior motion of the anterior leaflet of the mitral valve on echocardiogram. In eight patients with aortic stenosis with adequate echocardiograms, two had asymmetric septal hypertrophy and none had systolic anterior motion. The GCS demonstrated disproportionate upper septal thickening in 11; septal flattening in 16; cavity obliteration in 17; and a filling defect in the region of the left ventricular outflow tract in 16 of the 22 patients with hypertrophic cardiomyopathy. In the nine patients with valvular aortic stenosis, two demonstrated septal flattening, two cavity obliteration, two an outflow tract defect, and none disproportionate upper septal thickening. Both patients with cavity obliteration demonstrated asymmetric septal hypertrophy on echocardiogram. One normal control patient had septal flattening. Thus the gated cardiac blood pool scan provides an atraumatic technique for the evaluation of patients with hypertrophic cardiomyopathy which complements the echocardiogram.

Aortic Valve Stenosis↗
PubMed1975

Relationship between linguistic performance and memory deficits in retarded children.

Performance of retarded children was measured on four tests of linguistic ability and two memory tests. Subjects were 50 retarded children: 10 each at mental ages 3, 4, 5, 6, and 7. The relationship between linguistic performance and memory was assessed by correlational analysis. Multiple and partial correlations were computed using a measure of language comprehension and a measure of memory span as predictor variables and three measures of language production as criterion variables. Different patterns of correlation were found with the three production as criterion variables. Different patterns of correlation were found with the three production measures, suggesting that the relative importance of memory span in language production depends on the specific production task.

Auditory Perception↗