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Biomedical subjects

W F Walsh

Publications and source records attributed to W F Walsh.

53 records · Page 3Linked to original sources
PubMed1989

Effect of electromagnetic interference by neonatal transport equipment on aircraft operation.

The number of civilian air ambulance services operating in the United States has been steadily increasing. The quantity and sophistication of electronic equipment used during neonatal transport have also increased. All medical equipment generates some electromagnetic interference (EMI). Excessive EMI can interfere with any of an aircraft's electrical systems, including navigation and communications. The United States military has strict standards for maximum EMI in transport equipment. Over the past 15 years, approximately 70% of neonatal transport monitors, ventilators, and incubators have failed testing due to excessive EMI. As neonatal transport equipment becomes more sophisticated, EMI is increased, and there is greater potential for aircraft malfunction. The Federal Aviation Administration should develop civilian standards for acceptable EMI, civilian aircraft operators must be aware of the possible dangers of excessive EMI, and equipment which does not meet future FAA standards should not be purchased.

Aircraft↗
PubMed1988

Doppler echocardiographic determination of aortic valve area using the continuity equation.

The noninvasive measurement of aortic valve area by use of the continuity equation has been proposed as an accurate method for determining the severity of aortic stenosis. In 32 patients (mean age 64 +/- 14 years) with proven aortic stenosis and without significant regurgitation, aortic valve areas derived by the Gorlin equation from cardiac catheterisation data were compared with valve areas calculated from the continuity equation using Doppler echocardiography. There was a close correlation between Doppler and catheter derived aortic valve areas (r = 0.87, SEE = 0.17 cm2). The interobserver error for aortic valve area measurement in 20 patients was 9.0 +/- 6.8%. The specificity of this method for critical aortic stenosis (aortic valve area less than 0.75 cm2) was 73% and the sensitivity 88%. We conclude that in an adult, predominantly elderly population with calcific aortic stenosis, this Doppler echocardiographic method is reproducible and can be used accurately to derive aortic valve area.

Adolescent↗
PubMed1985

Regional left ventricular wall motion assessment: comparison of two-dimensional echocardiography and radionuclide angiography with contrast angiography in healed myocardial infarction.

The diagnostic ability of radionuclide angiography (RNA) and 2-dimensional echocardiography (2-D echo) to assess regional left ventricular (LV) wall motion was compared with contrast angiography in 52 patients with healed myocardial infarction. After 5 patients were excluded for inadequate 2-D echocardiographic studies, the LV images of 47 patients obtained by all 3 techniques were divided into 7 segments for analysis. Both 2-D echo and RNA showed close agreement with contrast angiography in assessing normal vs abnormal wall motion in the anterobasal (91%, 91%), anterolateral (87%, 79%) and posterolateral segments (77%, 79%). The sensitivity in detecting wall motion abnormalities was highest for 2-D echo and RNA in the anterolateral (83%, 77%) and apical (95%, 84%) segments and lowest for the inferior segment (48%, 48%). Specificity of 2-D echo and RNA was high, ranging from 94% in the anterolateral segment to 71% in the septal segment for 2-D echo, and from 91% in the inferior segment to 81% in the posterobasal and septal segments for RNA. Major discrepancies with contrast angiography occurred more often in the posterobasal, posterolateral, inferior and septal LV segments. Thus, in comparison with contrast angiography, 2-D echo and RNA are reliable for detecting anterior and apical wall motion abnormalities, but relatively less sensitive for detecting wall motion abnormalities involving the inferior, posterobasal and posterolateral LV segments.

Aged↗
PubMed1984

Early and long-term results of coronary artery bypass grafting with severely depressed left ventricular performance.

The effects of coronary artery bypass grafting (CABG) on ventricular performance and long-term clinical status were studied in 18 consecutive patients with disabling angina pectoris and severely depressed left ventricular (LV) performance (ejection fraction [EF] 27 +/- 9%). All patients survived CABG, although 1 patient had a perioperative myocardial infarction. There was no change in LVEF at rest, 29 +/- 12%, in the other 17 patients. However, LVEF during peak exercise increased from 22 +/- 7% to 27 +/- 14% (p less than 0.05). The 17 patients were separated into 2 groups: those who increased their peak exercise LVEF by at least 10% (group A, 8 patients) and those who increased it by less than 10% (group B, 9 patients). Preoperatively, patients in group A had a higher LVEF at rest (p less than 0.001) and smaller end-systolic and end-diastolic volumes at rest (p less than 0.001) and during exercise (p less than 0.005). Preoperatively, the LVEF in group A decreased with exercise, from 36 +/- 4% to 27 +/- 5% (p less than 0.01), but was unchanged in group B (19 +/- 3% vs 17 +/- 4%, difference not significant). After CABG, patients in group A had a smaller increase in end-systolic volume with exercise than those in group B (13 +/- 7 vs 34 +/- 22 ml/m2, p less than 0.05), but the changes in end-diastolic volume with exercise were not significantly different. At 27 +/- 5 months after CABG, 5 of 8 patients in group A were asymptomatic.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1983

Early left ventricular dysfunction and chelation therapy in thalassemia major.

Exercise radionuclide angiography was used to assess the incidence of subclinical abnormalities of left ventricular function in 23 asymptomatic patients with thalassemia major. Left ventricular ejection fraction (LVEF) at rest was normal in 18 patients and abnormal in 5. A normal LVEF response during exercise was shown in only 5 of the patients with normal resting left ventricular function. A normal response during exercise occurred more often in those patients who had received a smaller transfusional iron load and had a lower serum ferritin level (p less than 0.05). Twelve of the twenty-three patients were receiving chelation therapy with subcutaneous deferoxamine. Ejection fraction at rest was normal in 11 of these patients. During exercise a normal ventricular response was shown in 4 patients. After 1 year of intensive chelation therapy in these 12 patients, left ventricular function was reassessed. A normal exercise response was seen in an additional 4 patients; 3 of these showed an increase in peak exercise LVEF, and in the remaining patient no change of peak exercise LVEF was shown. The response during exercise was unchanged in 3 patients and had deteriorated in 1 patient.

Adolescent↗
PubMed1981

Results of long-term vasodilator therapy in patients with refractory congestive heart failure.

The long-term effects of vasodilator therapy with oral hydralazine and long-acting nitrates were studied in 34 patients with refractory heart failure. Seven patients who had marginal hemodynamic improvement despite optimal hydralazine therapy were not maintained on vasodilators, and eight who had a favorable hemodynamic response subsequently discontinued hydralazine therapy because of side effects. Of these 15 patients, four (27%) died and 11 remained in New York Heart Association functional class II or IV at a mean follow-up of 10 +/- 2 months (SEM). The 19 patients who received chronic therapy for 8 +/- 2 months were divided into nine late responders (47%), who improved to functional class I or II, and 10 late nonresponders (53%), who remained in functional class III or IV. Only one of the nine late responders (11%) died, compared with seven of the 10 late nonresponders (70%) (p less than 0.01). The actuarially determined survival at 1 year was 100% for late responders and 13 +/- 12% for late nonresponders (p less than 0.01). No clinical variable could distinguish late responders from late nonresponders. Hemodynamic variables measured before vasodilator therapy showed that late responders had a lower mean right atrial pressure (8 +/- 1 vs 17 +/- 3 mm Hg, p less than 0.01) and lower mean pulmonary artery wedge pressure (20 +/- 2 vs 30 +/- 2 mm Hg, p less than 0.005), higher stroke, volume index (27 +/- 2 vs 20 +/- 1 ml/m2, p less than 0.005) and higher stroke work index (32 +/- 4 vs 19 +/- 2 g-m/m2, p less than 0.01) than late nonresponders. There were no significant differences in the acute response to vasodilators between the two groups. We conclude that (1) a substantial portion of patients with refractory congestive heart failure either do not have a beneficial response to vasodilator therapy or discontinue it because of side effects; (2) about half of the patients who are maintained on chronic vasodilator therapy (or about one-fourth of the patients in whom therapy is initiated) had sustained clinical benefit; and (3) the initial hemodynamics, but not the clinical variables, are predictive of late mortality and late clinical response. Patients with evidence of more severe left ventricular dysfunction have an unfavorable course.

Administration, Oral↗
PubMed1977

Nitrogen-13-labeled ammonia for myocardial imaging.

Cyclotron-produced nitrogen-13 (half-life 10 min), as labeled ammonia (13NH4+), has been evaluated as a myocardial perfusion imaging agent. The regional myocardial uptake of 13NH4+ has been shown to be proportional to regional tissue perfusion in animal studies. Intravenously administered 13NH4+ is rapidly cleared from the circulation, being extracted by the liver (15%), lungs, myocardium (2%-4%), brain, kidney, and bladder. Myocardial ammonia is metabolized mainly to glutamine via the glutamine synthetase pathway. Pulmonary uptake is substantial, but usually transient, except in smokers where clearance may be delayed. The position annihilation irradiation (511 keV) of 13N may be imaged with a scintillation camera, using either a specially designed tungsten collimator or a pinhole collimator. After early technical problems with collimation and the production method of 13NH4+ were overcome, reproducible high quality myocardial images were consistently obtained. The normal myocardial image was established to be of a homogeneous "doughnut" configuration. Imaging studies performed in patients with varying manifestations of ischemic and valvular heart disease showed a high incidence of localized perfusion defects, especially in patients with acute myocardial infarction. Sequential studies at short intervals in patients with acute infarction showed correlation between alterations in regional perfusion and the clinical course of the patient. It is concluded that myocardial imaging with 13NH4+ and a scintillation camera provides a valid and noninvasive means of assessing regional myocardial perfusion. This method is especially suitable for sequential studies of acute cardiac patients at short intervals. Coincidence imaging of the 511 keV annihilation irradiation provides a tomographic and potentially quantitative assessment of the regional myocardial uptake of 13NH4+.

Ammonia↗
PubMed1977

Assessment of diagnostic value of technetium-99m pyrophosphate myocardial scintigraphy in 80 patients with possible acute myocardial infarction.

The diagnostic value of technetium-99m-pyrophosphate (Tc-pyrophosphate) myocardial scintigraphy was determined in 80 consecutive patients who had been admitted to the coronary care unit in order to rule out an acute myocardial infarction. Scintigraphic findings obtained within 5 days of admission were correlated with the final cardiac diagnosis determined for each patient. Significant myocardial uptake of Tc-pyrophosphate (positive scans) occurred in 13 of 22 patients (59%) who had enzyme and/or electrocardiographic proven acute myocardial infarct: 3 out of 5 with transmural myocardial infarct, 9 of 16 with nontransmural myocardial infarct, and 1 patient with left bundle-branch block. Of 58 patients who showed no evidence of acute myocardial infarction, positive scans occurred in 14 of 33 patients who had unstable angina pectoris (42%), 0 of 6 who had congestive heart failure, 6 of 9 who had other acute cardiac syndromes, and in 0 of 10 who had noncardiac chest pain. In the patients with unstable angina pectoris positive scans could not be predicted on the basis of the history, electrocardiographic findings or the arteriographically determined severity of the coronary artery disease. Blood levels of Tc-99m activity measured in 21 cardiac patients and in 6 volunteers did not correlate with the uptake intensity of Tc-pyrophosphate. These findings suggest caution in the use of this imaging method for the diagnosis of acute myocardial infarct in patients admitted with 'rule out myocardial infarction'.

Acute Disease↗
PubMed1976

Noninvasive evaluation of regional myocardial perfusion in 112 patients using a mobile scintillation camera and intravenous nitrogen-13 labeled ammonia.

The short half-life positron emitter 13N, as labeled ammonia (13NH4+), was evaluated as a myocardial imaging agent. Regional myocardial uptake of 13NH4 correlated with the distribution of labeled microspheres in experimental myocardial infarction. Using intravenous 13NH4+, myocardial scintigraphy was performed in 85 cardiac patients and 27 normal subjects. Ninety-five scintigrams were suitable for analysis. Eighteen of 24 normal subjects had homogeneous myocardial images; six had inhomogeneous images attributable to early technical problems. Perfusion defects were observed in the scintigrams of 82% (57/65) of patients with coronary artery disease, being most common in patients with myocardial infarction (27/28). Six sequential studies showed changes in perfusion consistent with the clinical course of each patient. Scintigraphic abnormalities were also observed in 4/6 patients with valvular heart disease. 13NH4+ myocardial scintigraphy is a valid and sensitive method of assessing regional myocardial perfusion and is especially useful for sequential imaging at short intervals.

Acute Disease↗
PubMedDate not supplied

Subatmospheric oxygen therapy complicating subcutaneous emphysema.

An infant with hypoplastic left heart syndrome, excessive pulmonary blood flow, and tachypnea was placed on subatmospheric oxygen (supplemental nitrogen) to increase pulmonary vascular resistance and decrease pulmonary blood flow. His cardiorespiratory status stabilized without mechanical ventilation, but 2 weeks later he developed spontaneous subcutaneous emphysema. The emphysema worsened over approximately 1 month. During this time his left-to-right shunt gradually decreased, and he was weaned to room air. Even without the use of supplemental oxygen the emphysema resolved without complication, and the patient underwent successful orthotopic heart transplantation at 65 days of age.

Humans↗
PubMedDate not supplied

Embolization of a left atrial ball thrombus during transesophageal echocardiography.

We report a case of systemic embolization of a left atrial ball thrombus during transesophageal echocardiography (TEE). A 49-year-old man with rheumatic mitral stenosis and atrial fibrillation underwent TEE to evaluate a transient cerebral ischemic attack. TEE demonstrated a free-floating left atrial thrombus. Disappearance of the thrombus during the study occurred after tachycardia and was associated with acute hemiplegic stroke and an absent radial pulse. The possible mechanism of embolization and the implications for the selection and management of patients undergoing TEE are discussed.

Echocardiography↗
PubMedDate not supplied

In utero repair of myelomeningocele: a comparison of endoscopy and hysterotomy.

OBJECTIVE: To compare endoscopic coverage of myelomeningocele with a maternal split-thickness skin graft in utero to definitive neurosurgical closure through a hysterotomy. METHODS: Four fetuses with isolated myelomeningocele underwent endoscopic coverage of the defect with a maternal split-thickness skin graft in a CO(2) environment at 22-24 weeks' gestation. Subsequently, 4 fetuses underwent standard neurosurgical closure of their myelomeningoceles at 28-29 weeks' gestation. RESULTS: The mean operating time for the endoscopic procedures was 297 +/- 69 min. Two fetal losses occurred as a result of chorioamnionitis and placental abruption, respectively. A third baby delivered at 28 weeks' gestation after prolonged disruption of the membranes. The 2 survivors required standard closure of the myelomeningocele after delivery. The mean operating time for the hysterotomy procedures was 125 +/- 8 min. No mortality occurred, and all the infants delivered between 33 and 36 weeks with well-healed myelomeningocele scars. At present, the functional levels of all infants approximate the anatomical levels of the lesions. CONCLUSION: With current technology, in utero repair of congenital myelomeningocele through a hysterotomy appears to be technically superior to procedures performed endoscopically.

Adult↗