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Biomedical subjects

C W White

Publications and source records attributed to C W White.

At least 145 records · Page 8Linked to original sources
PubMed1984

The value of lesion cross-sectional area determined by quantitative coronary angiography in assessing the physiologic significance of proximal left anterior descending coronary arterial stenoses.

The results of previous work from this laboratory have shown a poor correlation between percent stenosis (determined visually with calipers) and the coronary reactive hyperemic response (an index of maximal coronary vasodilator capacity) determined during cardiac surgery. This study was performed to determine whether other parameters of lesion severity could predict the reactive hyperemic response and thus the hemodynamic significance of coronary stenoses in human beings. Twenty-three patients with lesions in the proximal left anterior descending coronary artery were studied. To account for differences in expected vessel size, patients with large diagonal branches (greater than one-half the diameter of the left anterior descending artery) arising before the lesion were excluded. Computer-assisted quantitative coronary angiography was used to measure percent diameter stenosis, percent area stenosis, and minimal stenosis cross-sectional area. With a pulsed Doppler velocity probe, reactive hyperemic responses were recorded after a 20 sec coronary occlusion of the left anterior descending artery at cardiac surgery before cardiopulmonary bypass and were quantified by the peak/resting velocity ratio (normal greater than 3.5:1). Percent area stenosis ranged from 7% to 54% for vessels with normal reactive hyperemic responses and from 27% to 94% for vessels with abnormal reactive hyperemic responses. With both percent diameter stenosis and percent area stenosis there was substantial overlap between vessels with normal and abnormal reactive hyperemic responses. In contrast, nine of nine vessels with normal reactive hyperemic responses had lesion minimal cross-sectional areas of greater than 3.5 mm2 and 13 of 14 vessels with abnormal reactive hyperemic responses had minimal cross-sectional areas of less than 3.5 mm2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Intact human erythrocytes prevent hydrogen peroxide-mediated damage to isolated perfused rat lungs and cultured bovine pulmonary artery endothelial cells.

Addition of untreated or glutaraldehyde-fixed human erythrocytes decreased hydrogen peroxide (H2O2)-mediated acute edematous injury in isolated rat lungs, H2O2-induced damage to cultured bovine pulmonary artery endothelial cells, and H2O2-dependent oxidation of reduced cytochrome C in vitro. The results suggest that intact erythrocytes can scavenge H2O2, and as a result, protect the lung and possibly other tissues from damage.

Animals↗
PubMed1984

Evaluating visual loss with multi-flash campimetry.

Multi-flash campimetry is a computer-implemented psychophysical technique that allows temporal resolution to be assessed in 120 points per eye in a half hour. It has previously been reported that the results can serve to distinguish between multiple sclerosis patients and control subjects. We have now used this technique to measure temporal resolution in patients with amblyopia, cataracts, optic neuritis or macular degeneration. Our results indicate that multi-flash campimetry is at least as sensitive to visual loss in patients with amblyopia or cataracts as visual acuity testing with the Snellen chart and kinetic visual field testing with the Goldmann perimeter. Further, multi-flash campimetry may be more sensitive than the other two techniques to subtle residual loss in patients who have had optic neuritis and to early loss in patients with macular degeneration.

Adult↗
PubMed1982

The effects of atrial fibrillation on atrial pressure-volume and flow relationships.

To study whether atrial fibrillation might produce local changes in the atrium which could facilitate the tendency of this arrhythmia to become chronic and self-perpetuating, we compared the effect of atrial fibrillation, atrial pacing, and acute volume loading on the perfusion and oxygen consumption of the atrium in anesthetized dogs. Measurement of atrial perfusion with microspheres indicates that during atrial fibrillation, atrial blood flow increases 2- to 3-fold. Right atrial pacing is a significantly less potent metabolic stimulus for atrial vasodilation. Using Doppler velocity recordings of sinus node artery blood flow velocity, a marked increase in velocity is observed within 5 seconds after the initiation of atrial fibrillation. During atrial fibrillation, the sinus node artery reactive hyperemia response is markedly attenuated. Atrial fibrillation acutely decreases atrial distensibility; atrial pressure increased 81 +/- 19% with only a small increase (9.7 +/- 3%) in atrial diameter measured by echocardiography. During sinus rhythm, volume expansion to equivalent levels of atrial pressure as seen during atrial fibrillation increased atrial diameter 21 +/- 5% P less than 0.05. Atrial oxygen consumption determined by the microspectrophotometric method markedly increases during atrial fibrillation, compared to control conditions (12.3 +/- 2.8 vs. 3.9 +/- 0.6 ml O2/min per 100 g, respectively) P less than 0.05. Atrial O2 extraction was 5.5 +/- 0.4 ml O2/ml blood in the control state, and did not change with interventions. There was a linear relationship between left atrial O2 consumption and blood flow in all experimental conditions. Atrial fibrillation therefore alters atrial hemodynamics and metabolism by increasing atrial blood flow and oxygen consumption and decreasing atrial distensibility. Since atrial perfusion during atrial fibrillation is high and atrial flow reserve is limited, it is possible that additional atrial metabolic requirements might lead to atrial ischemia, fibrosis, and, thereby, perpetuation of the arrhythmia.

Animals↗
PubMed1981

Abnormalities in baroreflex control of heart rate in canine heart failure.

The mechanism of the attenuated arterial baroreceptor control of heart rate in heart failure was studied in 18 unanesthetized dogs after the development of chronic right-heart failure and compared to 12 control animals. The change in heart rate and arterial pressure in response to increases in right carotid sinus pressure during isolated carotid sinus perfusion was markedly reduced in heart failure (P less than 0.05). After vagotomy the difference in heart rate responses persisted, but was less pronounced (P = 0.065). The chronotropic response to perfusion of the sinus node artery with acetylcholine in heart-failure dogs showed a selectively depressed response, when compared to norepinephrine and hypertonic saline. The ratio of the change in heart rate in heart-failure vs. control dogs was 57% for acetylcholine but was not diminished for hypertonic saline (114%). The effect of direct vagal nerve stimulation on changes in heart rate was also markedly reduced in heart-failure dogs. These studies demonstrate that the alterations in baroreceptor control of heart rate in heart failure involve both the parasympathetic and sympathetic baroreflex efferent limbs. There is, in addition, a depressed responsiveness of the sinus node to cholinergic stimuli.

Animals↗
PubMed1981

Reversibility of abnormal arterial baroreflex control of heart rate in heart failure.

The reversibility of the abnormalities in arterial baroreceptor control of heart rate in heart failure was examined in an experimental model of canine high-output biventricular failure produced by an arteriovenous fistula that could be later surgically corrected by ligation. Marked attenuation of arterial baroreceptor control of heart rate in response to both hypertensive and hypotensive stimuli was seen in this model of heart failure. After surgical correction the heart rate response to a hypertensive stimulus did not return to normal but remained severely blunted for up to 8 mo of follow-up. The lack of reversibility after surgical correction suggests that permanent structural changes in arterial baroreceptors may occur after heart failure of short duration.

Animals↗
PubMed1981

Changes in cardiovascular health knowledge occurring from childhood to adulthood. A cross-sectional study.

A standardized test of cardiovascular health knowledge was administered to 1367 students, ages 12-18 years, and 562 adults, ages 20-60 years. Mean scores were: ages 12-14 years, 42.5 +/- 0.7% (SEM); 15-18 years, 49.1 +/- 0.1%; 20-40 years, 68.7 +/- 0.7%; 40-60 years, 68.2 +/- 0.7% correct. Cardiovascular health knowledge increased linearly in the student population, averaging 3.08% per year. Increases continued to occur in adults, but plateaued after age 40 years, despite an increasing incidence of cardiovascular disease in this age group. Health knowledge was highly correlated with the highest educational achievement. At all age levels, knowledge of diagnostic tests was highest and knowledge of pathophysiology lowest. A personal or family history of heart disease or history of an elevated serum cholesterol was not a stimulus for increases in health knowledge.

Adolescent↗
PubMed1980

Efficacy of traditional continuing medical education in changing physician knowledge and behavior in the care of patients with acute myocardial infarction.

In a controlled study, we assessed the effectiveness of a 2 hour traditional CME program in changing the knowledge and behavior of 23 family physicians caring for 123 patients with acute myocardial infarction. Although significant immediate gains in knowledge occurred, these gains were not translated into significant improvements on 33 patient care practices as assessed by a special medical audit instrument.

Clinical Competence↗
PubMed1978

Anuloaortic ectasia: angiographic, hemodynamic and clinical comparison with aortic valve insufficiency.

Thirty-five patients with angiographically diagnosed anuloaortic ectasia were compared with 18 patients with isolated aortic valve insufficiency to study differences between the presentation, hemodynamic or angiographic findings and clinical course in the two groups. The maximal aortic root diameter in anuloaortic ectasia was 7.6 +/- 2.4 cm (mean +/- 1 standard deviation) versus 4.2 +/- 0.6 in aortic insufficiency. Dissection was a common complication of anuloaortic ectasia (44 percent) but was not seen in aortic insufficiency. Neither the size nor the configuration of the aortic aneurysm was a reliable predictor of dissection. Despite surgical therapy, patients with anuloaortic ectasia have a worse prognosis than those with aortic valve insufficiency.

Adult↗
PubMed1978

Systemic hypertension complicating tetralogy of Fallot: effects of antihypertensive therapy.

A 20 year old woman with tetralogy of Fallot and an associated atrial septal defect presented with severe hypertension and congestive heart failure. She had been acyanotic for several years. An acute trial of antihypertensive therapy during cardiac catheterization resulted in severe systemic oxygen desaturation and loss of consciousness. Since surgical correction, antihypertensive therapy has been well tolerated. This case demonstrates the hemodynamic importance of systemic vascular resistance in tetralogy of Fallot and the need for extreme caution if aggressive antihypertensive therapy is attempted before surgical correction.

Adult↗
PubMed1977

The status of cardiovascular health knowledge among sixth, seventh, and eighth grade children.

The goals of this study were to develop and standardize a test of cardiovascular health knowledge to determine its status among primary school children, to ascertain the rate at which cardiovascular health knowledge increases as compared to other subject areas, and to demonstrate the feasibility of the use of standardized achievement tests for assessing the results of health education curricula. The Iowa Cardiovascular Health Knowledge Test (ICVHT) was developed and administered in conjunction with a standardized educational testing program, the Iowa Test of Basic Skills (ITBS), to a stratified sample of 2,675 Iowa Students from grades six, seven, and eight. The average student in the sixth, seventh and eighth grades answered 37.9 +/- 0.4, 41.2 +/- 0.3, and 43.7 +/- 0.4 (SEM) percent of the items correctly. ICVHT scores increased minimally (less than 1 item/grade) as grade levels increased, but at a 75% slower rate than scores in other subjects tested. The results document a deficiency in cardiovascular health knowledge and provide a model for use in educational assessment programs in other health disciplines.

Achievement↗
PubMed1977

Distribution of coronary artery flow to the canine right atrium and sinoatrial node.

We assessed segmental distribution of blood flow to the right atrium and the region of the sinoatrial node using micropheres (7-10 mum) in 20 anesthetized dogs. Mean right atrial flow averaged 83+/-7 (SE) ml/min X 100 g, which was 56% of the left ventricular blood flow. The distribution of right atrial flow was not homogeneous. For example, flow to anterior right atriaater (105+/-8 ml/min X 100 g) than mean right atrial flow. Following ligation of the sinus node artery, perfusion of the segment containing the sinus node decreased by only 36%. Relative preservation of perfusion to the sinus node following sinus node artery ligation may explain why ligation of the sinus node artery does not alter heart rate. Furthermore, we also found that cannulation and pump perfusion of the sinus node artery at pressures 10 and 50 mm Hg greater than systolic pressure did not alter the distribution of right atrial flow. Thus, because cannulation and perfusion of the sinus node artery do not artifactually distort regional right atrial blood flow, we conclude that this should be a useful method for evaluating responsiveness of the sinus node to various interventions.

Acetylcholine↗
PubMed1976

Potentiation of excitatory synaptic transmission in the normal and in the reinnervated dentate gyrus of the rat.

Following destruction of the ipsilateral temporo-ammonic tract, which originates in the entorhinal cortex, and terminates on the granule cells of the dentate gyrus, fibers from the surviving contralateral entorhinal area proliferate forming extensive new connections with the denervated dentate granule cells. Utlizing extracellular recording techniques, we have compared the characteristics of synaptic transmission in the lesion induced afferents with the characteristics of the normal ipsilateral afferents by analyzing the responses of dentate granule cells to paired pulse activation of temporo-dentate circuitry. In the dentate gyrus of the normal rat, and extracellularly recorded EPSP evoked by stimulation of the ipsilateral entorhinal cortex is enhanced by as much as 100% by a "conditioning" pulse to the same afferent system. This is called paired pulse potentiation. In the reinnervated dentate gyrus, the extracellular EPSP evoked by a test stimulus delivered to the contralateral entorhinal cortex is also potentiated by a conditioning pulse. Thepaired pulse potentiation in the reinnervated dentate gyrus has a time course which is comparable to that of the normal ipsilateral afferent system, but the magnitude of the potentiation is somewhat less, averaging approximately 140% of control...

Afferent Pathways↗
PubMed1976

Visual masking during pursuit eye movements.

In three experiments, targets and masking stimuli were briefly flashce while observers visually tracked a moving dot. Masking stimuli were more effective when they appeared to be in the same place as the target but stimulated different parts of the retina than when they stimulated the same parts of the retina but appeared displaced because of of an intervening pursuit eye movement. Visual masking during pursuit eye movements thus depended on the apparent position of the stimuli, not their retinal positions as such, which is in disagreement with previous studies of visual masking during saccadic eye movements. The apparent conflict can be explained in terms of the functional significance of visual masking in tracking and saccardic movements: Retinal position masking after saccadic eye movements may erase previous images, and apparent position masking during pursuit eye movements may make moving targets more visible.

Eye Movements↗