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Biomedical subjects

R Lisbona

Publications and source records attributed to R Lisbona.

At least 55 records · Page 3Linked to original sources
PubMed1987

Gravity-independent inequality in pulmonary blood flow in humans.

Single-photon emission computerized tomography of the lung with 99mTc-labeled human albumin macroaggregates (99mTc-MAA) was used in six healthy subjects to study the three-dimensional distribution of pulmonary blood flow. 99mTc-MAA was injected while the subjects were resting in the supine position and holding their lung volume at normal end expiration. Tomography was performed on each subject from 120 projections of radioactivity in the lungs acquired with a rotating gamma camera. To minimize lung motion artifacts, the subjects were asked to hold their breath at end expiration during the 10-s duration of data acquisition in each projectional angle. Perfusion images of lung slices (11 mm thick) were reconstructed, and the radioactivity within each slice was expressed per unit lung volume of 3.7 X 3.7 X 11 mm. Perfusion images of a midcoronal slice from each subject manifested a concentric pattern of radioactivity that decreased significantly from the center to the periphery, suggesting that blood flow rate per unit lung volume was up to 10 times larger near the central region. This gradient in activity between the center and the periphery of the coronary slices was gravity independent as the subjects were supine. Images of sagittal slices from the middle of the right lung also manifested a similar pattern of concentric gradient in activity, with the vertical distribution (gravity related) almost comparable with the horizontal distribution (gravity independent). These results indicate that pulmonary blood flow in resting supine humans is spatially stratified with a marked central-to-peripheral gradient in all directions. It appears that zone 4 (reduced blood flow) is not a phenomenon limited to the dependent region of the lung as commonly thought but rather is a manifestation of this spatial distribution whereby blood flow is lowest in all peripheral regions of the lung.

Adult↗
PubMed1987

Observations with SPECT on the normal regional distribution of pulmonary blood flow in gravity independent planes.

While the effect of gravity on the pulmonary circulation is well documented, the distribution of pulmonary flow under gravity independent conditions is not as well understood. Single photon emission computed tomography was applied to the study of regional pulmonary blood flow in slices where the effect of gravity was constant. Lung tomography, after the injection of [99mTc]MAA, was carried out in six normal volunteers and in the fully inflated and isolated lungs from six dogs that had been killed. Our tomographic results suggest that pulmonary perfusion in isogravitational planes is inherently nonuniform with preferential flow centrally and reduced circulation more peripherally. Planar imaging of the dissected isogravitational slices from the animals further confirmed the uneven perfusion noted on the tomographic slices.

Adult↗
PubMed1986

Interventricular delay in severe aortic stenosis recognized by gated radionuclear blood pool scanning.

Twenty-four patients referred for cardiac catheterization for suspected aortic stenosis were investigated by equilibrium gated blood pool study. From the time-activity curves, end systole for each ventricle was determined and the delay between the two was calculated. The patients were divided into three groups according to their calculated aortic valve area. The mean delay in a control group of 20 normal subjects was 6 +/- 13 msec (mean +/- standard deviation). In group I (aortic valve area greater than 0.75 cm2) the delay was 16 +/- 25 msec (p = NS compared to controls); in group II (aortic valve area 0.5 to 0.75 cm2) the delay was 28 +/- 27 msec (p less than 0.01); and in group III (aortic valve area less than 0.5 cm2) the delay was 60 +/- 28 msec (p less than 0.001). Ten patients were restudied after valve replacement; their mean delay decreased markedly from 48 +/- 19 to 5 +/- 26 msec (p less than 0.001). Thus, this method appears to identify patients with severe aortic stenosis and may therefore be a useful adjunct to the noninvasive assessment of this disorder both before and after surgery.

Adult↗
PubMed1986

Long-term prognosis of surgical treatment of renovascular hypertension: a fifteen-year experience.

To determine the long-term prognosis for hypertension control, mortality, renal function, and maintenance of renal blood flow in patients operated on to control renovascular hypertension, we studied 60 patients managed surgically between 1969 and 1984. Thirty-six patients had atherosclerotic disease, 22 had fibromuscular dysplasia, one had neurofibromatosis, and one had a combination of atherosclerosis and pyelonephritis. We confined the analysis to the 58 patients with pure atherosclerosis or fibromuscular dysplasia. In the atherosclerosis group 14 patients died and the results of hypertension control in the remaining 22 were classified as cured, three (14%); improved, 15 (68%); failed, one (5%); and unknown, three (14%). In the fibromuscular dysplasia group one patient died and results of hypertension control in the remaining 21 patients were (1) cured, 10 (48%); improved, 10 (48%); and failed, one (5%). The 5- and 10-year survival rates were 79% and 40%, respectively, for the atherosclerosis group and 95% and 89%, respectively, for the fibromuscular dysplasia group. Renal function was well maintained for patients in both groups. The mean serum creatinine value was 1.4 mg/dl in the atherosclerosis group and 1.0 mg/dl in the fibromuscular dysplasia group. To evaluate the effect of operation on the maintenance of renal blood flow we compared the blood flow of the operated and unoperated sides in patients who had a unilateral operation and had a second kidney for comparison. Eight of these patients had scans in each of the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Radiocolloid liver imaging in hepatic steatosis.

In a review of 60 patients with fatty infiltration of the liver documented by Xe-133 imaging, 43% had normal radiocolloid liver images, and 57% had abnormal images with various combinations of hepatomegaly, mottling, splenomegaly, and splenic shift of radioactivity. None, however, showed focal defects. Fatty infiltrates do not simulate mass lesions on the radiocolloid study of the liver, and an area of photon deficiency in the presence of hepatic steatosis points to an additional pathologic process. The interpretation of the radiocolloid liver image is unhindered by fatty infiltration when searching for discrete space-occupying lesions.

Adult↗
PubMed1985

Improvement in resting ventricular performance following coronary bypass surgery.

To assess the changes in resting left ventricular (LV) function following coronary bypass surgery, technetium 99m-labeled multiple equilibrated blood pool gated scans were performed in 53 consecutive patients at rest, before operation, and at 24 hours and 1 week after operation. Left ventricular ejection fraction (LVEF) and end-diastolic volume (EDV) were measured. The LVEF increased significantly from a preoperative value of 49 +/- 2% to 56 +/- 2% at 24 hours after operation (p less than 0.05) and 56 +/- 2% at 1 week following operation (p less than 0.05 compared with the preoperative value). The EDV also exhibited significant changes, decreasing from a preoperative value of 148 +/- 8 ml to 91 +/- 11 ml at 24 hours (p less than 0.001) and 114 +/- 9 ml at 1 week (p less than 0.01 compared with the preoperative value). When the patients were divided into two groups according to the preoperative LVEF (Group 1, LVEF of greater than or equal to 50%; Group 2, LVEF of less than 50%), the observed changes were similar. This study demonstrates significant improvement in resting LV function 24 hours following coronary bypass surgery. This improvement persists at 1 week and is not related to the degree of preoperative impairment. We conclude that the combination of successful revascularization and optimal myocardial protection can result in significant improvement of LV function at rest.

Adult↗
PubMed1985

Tc-99m red blood cell venography in deep venous thrombosis of the lower limb. An overview.

Tc-99m red blood cell venography is a simple and sensitive technique for the diagnosis of deep vein thrombosis of the lower limb. The static high count blood pool images of the deep venous system of the leg are readily interpretable and show good correlation with contrast venography. The advantages and limitations of this technique in the clinical setting are discussed in detail in this review.

Erythrocytes↗
PubMed1985

Perfusion lung scanning: differentiation of primary from thromboembolic pulmonary hypertension.

Of eight patients with pulmonary arterial hypertension, final diagnosis established by autopsy or angiography, four had primary hypertension and four hypertension from thromboembolism. The perfusion lung scan was distinctly different in the two groups. The lung scan in primary pulmonary hypertension was associated with nonsegmental, patchy defects of perfusion, while in thromboembolic hypertensives it was characterized by segmental and/or lobar defects of perfusion with or without subsegmental defects. The perfusion lung scan is a valuable, noninvasive study in the evaluation of the patient with pulmonary hypertension of undetermined cause and in the exclusion of occult large-vessel pulmonary thromboembolism.

Adult↗
PubMed1984

Early diagnosis of myositis ossificans with Tc-99m diphosphonate imaging.

Myositis ossificans is primarily a disorder of young adults, whereby an area of muscle mass undergoes progressive ossification. The authors review a case in which the patient's presentation was somewhat atypical, and where the course of disease was unusually prolonged. Examination of the soft tissue lesion using Tc-99m diphosphonate bone scans was helpful in establishing the diagnosis and in determining the full extent of the process early in its evolution.

Adult↗
PubMed1984

The diagnostic and prognostic value of renal allograft biopsy.

We prospectively studied 89 patients to assess the diagnostic use of renal allograft biopsy in the first three months after transplantation. These biopsies were done in patients in whom diagnosis was not clear or clinical rejection was deemed to be severe. Clinical diagnosis at initial biopsy was compared with the morphological diagnosis. To determine if morphological data improved the prognostic usefulness of the clinical data, we performed multiple logistic regression relating clinical variables at initial biopsy and histological changes in the transplant to the outcome of 120 patients one year after biopsy. The clinical and morphological diagnosis differed in 41 of 89 patients (46%). Of 120 patients in the prognostic study, 35 returned to dialysis during the first year following transplantation. Using multiple logistic regression, a categorical variable that took into account both the serum creatinine and its rate of change before biopsy was the best clinical predictor of return to dialysis. Further increase in chi 2 occurred with type of donor, number of transfusions, and age. Using the clinical variables we produced an index, from 0 to 1 to predict outcome. Only 8 had index less than 0.2, of whom 7 returned to dialysis. The best morphological predictor of outcome was interstitial hemorrhage. Further increase in chi 2 was obtained with vascular endothelial proliferation, glomerular endothelial swelling, and glomerular necrosis. With an index derived from the morphological variables only 11 had index less than 0.2, of whom 9 returned to dialysis. Combining both clinical and morphological data, the best predictor of return to dialysis was interstitial hemorrhage, followed by creatinine, glomerular endothelial swelling, and type of donor. Using both clinical and morphological variables we produced another index to predict outcome. A group of 65 patients had index greater than 0.8, of whom 63 (94%) did not return to dialysis, and 18 patients had index less than 0.2, 17 of whom returned to dialysis. The remaining 12 patients in the dialysis group and 15 in the nondialysis group had indices greater than 0.2 less than 0.8. We conclude that a transplant biopsy yields important diagnostic and prognostic information. Unexpected diagnoses were made in 46% of cases. The addition of morphological data to the clinical data available at time of biopsy greatly improved the prediction of return to dialysis.

Biopsy↗
PubMed1984

Correlative electrocardiographic studies in myocardial infarction.

The electrocardiogram remains our first and most widely available tool to study myocardial infarction. We have attempted to suggest that we must be both more circumspect and adventurous in its use. The traditional electrocardiographic labels imply a level of precision that is unwarranted and so obscure real, often clinically important differences that exist among patients. We believe the electrocardiogram becomes more powerful when it is used with other noninvasive tests, and all such tests are best interpreted within rather than removed from the clinical context. We suggest as well that frequently after infarction, zones of viable muscle exist that are still vulnerable to ischemia. These zones may lie within or be remote from the actual infarct region, and noninvasive tests should be milked for clues that these regions are present, for while there is little to be done for necrotic tissue after infarction, there is considerable therapy available, both medical and surgical, to rescue tissue at risk of ischemia after infarction.

Electrocardiography↗
PubMed1983

Hemodynamic effects of encainide in patients with ventricular arrhythmia and poor ventricular function.

Gated cardiac scanning was used to evaluate the hemodynamic effects of encainide in 19 patients (1 woman) with complex ventricular arrhythmia and depressed left ventricular (LV) function (ejection fraction less than 45%). Patients were 36 to 80 years old (average 61). All were candidates for long-term encainide therapy after having failed with currently available antiarrhythmics. Sixty-three percent had congestive heart failure before they received encainide. All were evaluated in the hospital before encainide therapy by a gated cardiac scan performed at least 3 days after discontinuing all antiarrhythmic drugs. Patients received oral encainide in doses of 75 to 200 mg. Gated cardiac scans were repeated 1 to 2 weeks later when an 80% reduction in frequency of premature ventricular complexes was observed on a 24-hour Holter recording. No patient had worsening of congestive heart failure during encainide therapy. Encainide did not significantly affect ejection fraction, which averaged 22 +/- 10% before and 25 +/- 14% (SD) after encainide (difference not significant [NS]). Other hemodynamic variables, including heart rate, blood pressure, stroke volume and end-diastolic volume, remained unchanged during encainide therapy. Digoxin blood levels in 10 patients averaged 1.04 +/- 0.43 before and 1.22 +/- 0.47 mg/ml (NS) during encainide therapy. Thus, encainide given orally in clinically effective doses does not appear to have significant hemodynamic effects in patients with ventricular arrhythmia and depressed LV function.

Adult↗