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Biomedical subjects

R Lisbona

Publications and source records attributed to R Lisbona.

At least 37 records · Page 2Linked to original sources
PubMed1991

Whole body retention of Tc-99m phosphate in Paget's disease of bone.

The effectiveness of the 24-hour whole body retention of Tc-99m MDP in monitoring disease activity was evaluated in 58 patients with Paget's disease of bone. Patients had baseline 24-hour retention studies, bone scans, radionuclide bone blood-flow studies, and alkaline phosphatase and OH-Proline level measurements. Increased retention of Tc-99m MDP was present in 88% (51/58) of individuals while alkaline phosphatase and OH-Proline were respectively elevated in 100% (58/58) and 64% (35/55) of patients. Forty-seven examinations were further obtained to evaluate changes in retention with therapy. Retention correctly reflected response to treatment in 89.3% of follow-ups versus 85.1% with alkaline phosphatase (n = 47). It was accurate in 90.9% of patients versus 75% for OH-Proline (n = 44). We conclude that the retention study, while not absolutely correlative with Pagetic activity, still is useful in grading the condition. It is a simple additional step that monitors the global severity of lesions localized on bone scans.

Aged↗
PubMed1991

Detection of miliary tuberculosis by Ga-67 scintigraphy.

Two patients are presented in whom pulmonary accumulation of Ga-67 led to an early diagnosis of miliary tuberculosis and its prompt treatment. Their chest radiographs were unremarkable and thus noncontributory to the diagnostic process.

Aged↗
PubMed1991

Subclinical cardiac dysfunction in sarcoidosis.

Clinically apparent myocardial disease is infrequent in sarcoidosis. However, autopsy data show myocardial involvement in up to 30 percent of patients. Unexplained exertional symptomatology is a common complaint in patients with sarcoidosis. In this study, we investigated whether abnormal cardiac function might limit exercise performance in patients with sarcoidosis without overt cardiac involvement. We studied exercise responses in 35 patients with sarcoidosis and compared them with 28 untrained controls. Seventy-seven percent of the patients were symptomatic. Pulmonary function test results were lower in the group with sarcoidosis than normal controls, but they were within normal range. Only one patient had evidence of ventilatory limitation to exercise. Sixteen (46 percent) patients had abnormally increased heart rates (HRs) at rest prior to exercise testing and/or with exercise. Rapid HRs were confirmed during daily activities by continuous ambulatory electrocardiographic (ECG) monitoring. Left ventricular ejection fraction (LVEF) was measured to determine if systolic dysfunction could account for abnormal HR responses. Of patients with abnormally increased HRs, five had LVEFs less than 50 percent, and eight had normal LVEFs, of whom 75 percent had tachycardia at rest. Retrospective comparison of HR responses and LVEF between patients who did or did not receive corticosteroids revealed no significant differences between groups. We conclude that abnormal HR responses in patients without evident cardiac sarcoidosis are common and exertional symptoms in this population are often associated with chronotropic abnormalities. The exact mechanisms underlying the chronotropic abnormalities are unclear, but they likely include ventricular systolic dysfunction, sinus node dysfunction from granulomatous infiltration, or combinations of the two.

Adult↗
PubMed1990

Assessment of cardiac function in patients who were morbidly obese.

Cardiac function of 30 patients who were morbidly obese was studied before bariatric surgery. Twelve patients were studied 13 +/- 4 months after surgery. These patients had a mean age of 37.1 +/- 2.9 years and a body mass index of 50.0 +/- 1.4 kg/m2. Cardiac function was measured by echocardiography, radionuclide angiography scanning, and right heart catheterization. To determine the degree of cardiac dysfunction, the patients were studied with exercise and intravenous fluid challenges. Ultrasonography produced evidence of myocardial thickening with an increased interventricular septum in eight patients (32%) and increased left ventricular mass in 17 patients (53%). The radionuclide scan suggested that morbid obesity was associated with a significantly (p less than 0.05) increased end-diastolic volume and decreased left ventricular ejection fraction as compared with patients who were of normal weight. With exercise the patient who was of normal weight had an increase in the end-diastolic volume, stroke volume, and heart rate, but the patient who was morbidly obese only increased heart rate to produce the necessary increase in cardiac output. Right heart catheterization indicated that the relationship of the pulmonary wedge pressure and the left ventricular stroke work index was abnormal in 14 of 29 patients (48.3%) and depressed in six of 29 patients (20.7%) with exercise. One liter of fluid caused an abnormal relationship of the pulmonary wedge pressure and the left ventricular stroke work index in 12 of 30 patients (40%) and a depressed response in 10 of 30 patients (33.3%). Cardiac studies were repeated in 12 patients after a 54.8 +/- 1.9 kg weight loss. Echocardiography indicated a decrease in dilatation (27.3% to 9.1%) and a significant (p less than 0.05) decrease in hypertrophy (45.5% to 0%). After the weight loss, radionuclide and right heart catheterization studies indicated improved cardiac function with reduced filling pressures and increased left ventricular work during fluid and exercise challenges. These results support the presence of obesity-related cardiomyopathy with ventricular dysfunction, which appears to be caused by a noncompliant ventricle. Significant weight loss achieved with gastroplasty results in increased ventricular compliance and improved cardiac function.

Adult↗
PubMed1989

Long-term stepwise sustained improvement in left ventricular ejection fraction after myocardial infarction.

Radionuclide left ventricular ejection fraction, end-diastolic volume, and exercise capacity were determined in 34 selected patients who survived a first Q wave anterior infarction. Patients were included in the study if they had no subsequent cardiac events (unstable angina or myocardial infarction) during the average follow-up period of 47 months (range = 36 to 70 months); none was treated with thrombolysis, coronary angioplasty, or bypass grafting. Overall, mean left ventricular ejection fraction increased from 28 +/- 10% 1 month after infarction to 33 +/- 10% at 3 years (p less than 0.01); mean end-diastolic volume decreased from 217 +/- 99 ml to 171 +/- 80 ml (p less than 0.002). Stepwise improvement in left ventricular ejection fraction occurred in 15 of these patients (group B) and was associated with a significant increase in exercise capacity. Mean ejection fraction in group B was 26 +/- 7% at 1 month and 41 +/- 10% at 3 years (p less than 0.001). In all of these patients there was improved regional wall motion in the noninfarct zone, whereas five patients also showed improvement in the infarct zone. The results indicate a progressive improvement in left ventricular function that occurs over time in some patients after first Q wave anterior infarction, independent of intervention.

Adult↗
PubMed1989

A demonstration of vascular proliferation in response to arteriovenous reversal in the ischemic canine hind limb.

Patients with diffuse peripheral vascular disease, resulting in inadequate arteriographic runoff, and/or multiple failed bypasses almost inevitably face amputation. We have previously used an arteriovenous reversal (AVR) procedure at the popliteal level to salvage severely ischemic canine hind limbs. This procedure is followed by the development of an intense network of new vessels in the proximity of the arteriovenous anastomosis. The present study was designed to define the nature of these vessels and their role in providing nutrient perfusion to the limb. Using an established model to create severe limb ischemia. AVR was performed in 24 dogs. Tissue perfusion and neovascularization were assessed by angiography, transcutaneous oximetry (TcpO2), tritiated thymidine uptake combined with autoradiography, and histologic capillary density measurements. Angiography revealed the intense vascular network in the region of the anastomosis by postoperative Day 22 in all dogs. TcpO2 on Day 1 was indicative of severe ischemia in the operated calf compared to controls (12 vs 80 mm Hg, P less than 0.01) but returned to normal by Day 22 (81 vs 76 mm Hg). A progressive, significant increase in tritiated thymidine uptake was seen by Day 22 (0.36 vs 0.27 microCi/g, P = 0.005); on autoradiography 95% of these labeled nuclei in the operated limbs were in endothelial cells compared to only 5% in the control limbs. Finally, capillary density studies of the calf muscles showed a substantial increase in the operated limbs (mean, 1011 vs 605 cap/mm2, P = 0.0004). These studies suggest that the dramatic increase in vascularity observed angiographically following AVR in a severely ischemic limb consists primarily of a rapidly expanding capillary network.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Imaging of small cell carcinoma using 131I-labelled antibodies to vasopressin associated human neurophysin (VP-HNP)

Preliminary studies are reported on the use of 131I-labelled antibodies against vasopressin associated human neurophysin to image tumors in patients with small cell carcinoma of the lung (SCCL). The rabbit polyclonal antibodies used in these studies were affinity purified on columns of neurophysin-Sepharose. Patients were pre-screened for the presence of neurophysin producing tumors by plasma RIA. Six patients who screened positive received approximately 1 mCi/70 kg body weight of radioiodinated antibody preparation, and scintigraphy was subsequently performed at 24 h, 48 h, and 72 h using a subtraction technique based on simultaneous imaging with radiopharmaceutical agents labelled with technetium-99m. Tumor was clearly demonstrated at 72 h in all five patients who had measurable lesions at the time of study, while no positive image was noted for one patient in complete clinical remission. Since approximately 70% of all SCCL patients have neurophysin-producing tumors, our findings suggest that neurophysin antibodies may be effectively used to scan tumors in a majority of patients with SCCL.

Aged↗
PubMed1989

Effect of cardiac output on gravity-dependent and nondependent inequality in pulmonary blood flow.

To examine the effect of cardiac output (CO) on the gravity-nondependent distribution of pulmonary blood flow, 2 X 10(6) 99mTc-labeled albumin microspheres (20 microns) were injected at end expiration into dogs (anesthetized, supine, and breathing room air spontaneously). Two animals were injected at their resting CO, two were injected during increased CO (arteriovenous fistulas induced), and two were injected at low CO (phlebotomy induced). The chest was opened and the lungs were removed, drained of blood, and dried while fully inflated. Single-photon emission-computed tomography was performed on the dry lungs to map the distribution of activity in transverse, coronal, and sagittal slices. The results confirmed the presence of a central-peripheral gravity-nondependent gradient and showed that increases in CO were associated with increases in absolute flow to both the central and peripheral regions of the lung with persistence of the central-peripheral gradient. These observations were further confirmed by direct imaging of midcoronal slices. Examination of the average flow in vertical and horizontal slices showed that, when zone 1 was not present, changes in CO affected all slices uniformly, such that when the CO doubled, the absolute flow in every slice in all three planes also doubled. We conclude that, with the exception of recruitment and derecruitment of vascular channels in the upper regions of the lung (zone 1), when CO changes, the blood flow everywhere in the lung changes uniformly and in proportion to the CO. This uniform increase in blood flow is consistent with the three-dimensional nature and resistive properties of the pulmonary vascular tree.

Animals↗
PubMed1989

Prognosis in patients with low left ventricular ejection fraction after myocardial infarction. Importance of exercise capacity.

The measurement of left ventricular ejection fraction (LVEF) plays a key role in many strategies for managing patients after acute myocardial infarction. We tested the hypothesis that exercise capacity 1 month after myocardial infarction provides additional information in patients with a low LVEF and therefore assists in risk stratification. One hundred fifteen patients, with documented myocardial infarction and LVEF less than 35% by gated radionuclide scan 1 month after acute myocardial infarction, were followed up for 2 months to 7 years. Exercise capacity was estimated from a treadmill test 1 month after infarction. Using the Cox proportional hazards model, exercise capacity was a significant predictor of death or reinfarction. The relative risk of death, based on a comparison between the lowermost quintile (less than 4 METS) and uppermost quintile (greater than 7 METS), was 3.5 (95% confidence interval, 1.1-9.7); the relative risk in the fourth, third, and second quintile was 2.7, 2.1, and 1.6, respectively. In a multivariate analysis, the observed effect of a good exercise capacity was independent of LVEF. These data indicate that in patients with a low LVEF after myocardial infarction, useful prognostic information can be obtained from exercise testing.

Exercise↗
PubMed1989

Regional pulmonary perfusion following human heart-lung transplantation.

Ventilation and perfusion scans were obtained in six subjects who had undergone heart-lung transplantation with consequent denervation of the cardiopulmonary axis. Two of the subjects had developed obliterative bronchiolitis, which is believed to be a form of chronic rejection. Their pulmonary function tests demonstrated airflow obstruction and their scintigraphic studies were abnormal. In the remaining four subjects without obstructive airways disease, ventilation and planar perfusion scans were normal. Single photon emission computed tomography imaging of pulmonary perfusion in these patients revealed a layered distribution of blood flow indistinguishable from that of normal individuals. It is concluded that neurogenic mechanisms have little influence on the pattern of local pulmonary blood flow at rest.

Adult↗
PubMed1989

Scintigraphic and ultrasound features of giant hemangiomas of the liver.

Giant hemangiomas of the liver are clinically distinct from smaller and more innocent hemangiomas as they are more prone to complications. On imaging with ultrasound, they can also be readily confused with hepatoma, metastatic disease, or focal nodular hyperplasia. Nine giant hemangiomas (maximal diameter greater than 8 cm) were studied by scintigraphy and ultrasound. In all instances, the fill-in of the lesion on [99mTc]RBC scintigraphy indicated the diagnosis of hemangioma, adding specificity to the screening sonographic study. The pattern of fill-in on scintigraphy also appeared to be size dependent with lesions less than 11 cm in diameter equilibrating uniformly, while larger abnormalities intensified in centripetal fashion.

Erythrocytes↗
PubMed1988

Quantification of spatial blood flow distribution in isolated canine lung.

Single photon emission computed tomography (SPECT) in intact dogs and humans suggests that blood flow in the lung (Qr) is distributed so that at isogravity a large gradient in Qr exists between the core and the periphery. To confirm such findings, we injected (IV) six anesthetized healthy dogs (approximately 30 kg) with 20 mCi technetium-99m (Tc-99m)-labeled albumin macroaggregates. At injection, the dogs were in the supine position and breathing spontaneously. Injections were given at end expiration. The animals were killed and their chests opened; their lungs were removed and dissected free of other tissue, and the blood was drained. The lungs were inflated to full capacity, and warm (50 degrees C) air was blown into them for about 18 hours to dry them. The fully inflated and dry lungs were placed supine, and SPECT was performed to determine the 3-D distribution of activity. After SPECT was completed, either a coronal slice or a sagittal slice (1 cm thick) was cut and imaged directly by placing it against the gamma camera collimator for 6 minutes. The tomographic images of flow distribution in coronal slices (isogravity) revealed that independent of gravity, Qr in the central region of the lungs was greater than that in the periphery. Furthermore, the central-peripheral gradient was discernible within the individual lobes. The direct images of slice confirmed these findings. Tomographic images of sagittal slices showed that heterogeneities in Qr in the vertical (direction of gravity) and horizontal direction (isogravity) were comparable.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Effect of body posture on spatial distribution of pulmonary blood flow.

Single-photon emission-computed tomography (SPECT) on intact dogs and humans suggests that one aspect of regional blood flow in the lung (Qr) is independent of gravity, e.g., the gradient in Qr between the core and the periphery. To further evaluate these findings, six anesthetized healthy dogs (approximately 30 kg), two in the supine posture, two in the prone posture, and two suspended in the upright posture, breathing spontaneously, were injected (iv) at end expiration with 20 mCi99mTc-labeled albumin macroaggregates. The animals were killed, their chests were opened, their lungs were removed and dissected free of other tissue, and the blood was drained. The lungs were dried by blowing warm air (50 degrees C) while they were inflated to full capacity for about 18 h. The fully inflated and dry lungs were placed in the supine position and SPECT was performed to determine the three-dimensional distribution of activity. One hundred and twenty projections of the activity in the entire lungs were obtained at 3 degrees steps with a rotating gamma camera and stored in computer memory. Once SPECT was completed, either a coronal slice or a sagittal slice (1 cm thick) was cut and imaged directly by placing it against the gamma camera collimator for 6 min. The tomographic-reconstructed slices revealed that at isogravity, in all body postures, Qr in the central region of the lungs was up to 10 times that in the periphery. Furthermore, the central-peripheral gradient was discernible within the individual lobes. The direct images of slices also confirmed these findings. Although flow inequalities independent of gravity were present, the central region with the highest flow often was closer to the dependent regions of the lungs, suggesting that gravity had some influence on the final distribution. The results suggest that factors other than gravity also play an important role in the distribution of pulmonary blood flow. These factors may be related to the conductance of the vascular pathways that lead to different regions in the lungs.

Animals↗
PubMed1988

Role of scintigraphy in focally abnormal sonograms of fatty livers.

Fatty infiltration of the liver may cause a range of focal abnormalities on hepatic sonography which may simulate hepatic nodular lesions. Discrete deposits of fat or islands of normal tissue which are uninvolved by fatty infiltration may stand out as potential space-occupying lesions on the sonograms. Twelve patients with such focally abnormal ultrasound images were referred for liver scintigraphy with 133Xe and 99mTc colloidal SPECT studies to clarify the issue. These examinations helped identify, in nine of 12 patients, the innocent nature of the sonographic abnormalities which were simply related to the fat deposition process. Further, [99mTc]RBC scans defined the additional pathologic process in three patients in whom actual space-occupying lesions were indeed present in the liver. Scintigraphy has an important role to play in the understanding of focal hepatic ultrasound abnormalities particularly in unsuspected hepatic steatosis.

Aged↗
PubMed1987

Comparison of the effects of pindolol and propranolol on exercise performance in patients with angina pectoris.

The effects of pindolol (mean dose 17 +/- 8 mg/day), a beta-blocking drug with intrinsic sympathomimetic activity (ISA), and propranolol (130 +/- 40 mg/day) on exercise performance in 11 patients with stable angina pectoris were compared. Doses were titrated to symptoms. The design was a randomized, double-blind, crossover protocol with 8 weeks of treatment with each drug. At the end of each drug period, subjects performed 3 exercise tests: a symptom-limited test on a cycle ergometer with measurement of gas exchange parameters; a steady-state exercise test to measure cardiac output by the CO2 rebreathing method; and a supine exercise test with radionuclide angiography. The ISA effect of pindolol was evident at rest in that the heart rate of 82 +/- 4 beats/min was higher than with propranolol (70 +/- 3). At low levels of exercise heart rate, cardiac output and O2 consumption (VO2) were still higher. However, there was no difference in cardiac output or VO2 at higher levels of exercise and no difference in the VO2 at the anaerobic threshold and peak exercise. Peak VO2 was 1,344 +/- 108 ml/min with propranolol and 1,350 +/- 116 with pindolol therapy. There were also no differences in ejection fraction or cardiac volumes at rest or during exercise. The incidence of side effects was similar with both drugs and there was no significant preference for either medication. In conclusion, patients with angina treated with pindolol had the same peak exercise performance as with an 8:1 equivalent dose of propranolol (clinically equivalent), although at lower levels of exercise, VO2, cardiac output and heart rate were higher from the ISA of pindolol.

Angina Pectoris↗
PubMed1987

The relationship between central venous pressure and pulmonary capillary wedge pressure during aortic surgery.

Twenty-three ASA physical status II-III patients scheduled for elective abdominal aortic surgery were studied preoperatively with multiple unit gated acquisition angiography (MUGA) scan to determine the resting left ventricular and right ventricular ejection fractions (LVEF and RVEF respectively). Intraoperatively pulmonary capillary wedge pressure (PCWP) and central venous pressure (CVP) were measured in each patient at five different time periods in the horizontal, 24 degrees head up, and 24 degrees head down table tilt positions. The correlation between absolute values and changes in PCWP and CVP, and the degree to which preoperative knowledge of LVEF and RVEF predicted these correlations were examined. Resting LVEF ranged from 0.1 to 0.84. Thirteen of the 23 patients failed to show significant correlation (p less than 0.05) between the absolute values of PCWP and CVP either before and/or after aortic crossclamp. When the correlation coefficients from this analysis were ranked against LVEF, there was a weak but significant correlation before aortic crossclamp (r = 0.41), but not after. The correlation between a change in PCWP and a change in CVP was significant for the 23 patients at all time intervals, before and after aortic crossclamp. However, the prediction of a change of PCWP value from a known change of CVP value ranged in accuracy from +/- 3 mmHg to +/- 12.5 mmHg. The study suggests that if the filling pressures of both ventricles need to be assessed during aortic surgery, then the PCWP and CVP must be independently measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Technetium-99m red blood cell venography of the lower limb in symptomatic pulmonary embolization.

Tc-99m RBC venography of the legs was obtained in 42 patients with primary pulmonary symptomatology and a diagnosis of pulmonary embolization. In 31 of these 42 patients (74%), the nuclear venogram revealed the presence of deep vein thrombosis (DVT) and a source of embolization. Of the 31 patients with leg DVT documented by venography, 13 (42%) showed thrombosis confined to the calf. Clinical findings suggested that only 20 of the 31 patients (65%) with DVT could have harboured a source of embolization in the legs. Tc-99m RBC venography is a useful noninvasive test for the global and comprehensive assessment of patients with symptomatic pulmonary embolization.

Adult↗