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Biomedical subjects

G Rizzo

Publications and source records attributed to G Rizzo.

At least 163 records · Page 9Linked to original sources
PubMed1993

The development of abnormal heart rate patterns after absent end-diastolic velocity in umbilical artery: analysis of risk factors.

OBJECTIVES: Our objectives were to evaluate the time interval elapsing between the occurrence of absent end-diastolic velocity in the umbilical artery and either the development abnormal fetal heart rate patterns or delivery and to establish the maternal and fetal factors that may affect this interval. STUDY DESIGN: Thirty-seven fetuses free of structural and chromosomal abnormalities in which the development of absent end-diastolic velocity in umbilical artery was evidenced by serial Doppler recordings were studied. At the first occurrence the following factors were considered: gestational age, presence of hypertension or preeclampsia, amniotic fluid index, severity of growth retardation, and 10 different Doppler indices calculated from extracardiac and intracardiac vascular districts. Actuarial statistical methods were applied, with the occurrence of antepartum late heart rate deceleration as the censoring variable. RESULTS: The interval between the first occurrence of absent end-diastolic velocity in umbilical artery and delivery ranged from 1 to 26 days. Indications for delivery were the development of antepartum late heart rate decelerations in 23 fetuses (62.1%) and different maternal or fetal complications in the remaining 14 fetuses. Multivariate analysis revealed that gestational age and the presence of hypertension and pulsations in umbilical vein were the dominant factors in determining the length of this time interval. CONCLUSION: The duration of the time interval between the occurrence of absent end-diastolic velocity in umbilical artery and abnormal heart rate pattern differs considerably among fetuses, and it is mainly determined by gestational age and presence of maternal hypertension and pulsations in umbilical vein.

Blood Flow Velocity↗
PubMed1993

Analysis of risk factors influencing imminent distress in growth-retarded fetuses undergoing oxygen test.

We previously demonstrated a prognostic significance of maternal oxygen test in predicting imminent fetal distress. The purpose of this study was to investigate eventual other factors related to the length of the time interval elapsing between the Doppler diagnosis of brain sparing effect and abnormal fetal heart rate patterns. To this end we considered 101 growth-retarded fetuses free of structural and chromosomal abnormalities with a ratio between the pulsatility indices of umbilical and middle cerebral artery above the 95th centile in presence of a normal fetal heart rate pattern. The factors, other than the oxygen test, analyzed for a potential influence on this time interval were gestational age, presence of hypertension or preeclampsia, amniotic fluid index, severity of growth retardation (centile of the ultrasonographic estimated fetal weight) and 9 different Doppler indices calculated from extra- and intracardiac districts. Statistical actuarial methods were used to determine the effect of these prognostic factors on the duration of this time interval. The occurrence of abnormal fetal heart rate patterns (antepartum late heart rate decelerations) was used as censoring variable. The time interval between the entry in the study and delivery ranged from 1 to 39 days. Indications for delivery were fetal distress in 53 fetuses (52.4%) and different maternal or fetal complications in the remaining 48 fetuses.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed1993

Symptomatic cysts of the pineal gland: stereotactic diagnosis and treatment of two cases and review of the literature.

We report two cases of pineal gland cysts, both in young girls, causing aqueductal stenosis and symptomatic hydrocephalus, which were diagnosed and treated by Talairach's stereotactic method. This procedure permitted aspiration of the cyst content, normalization of aqueductal stenosis, and a differential histological diagnosis. Postoperative computed tomographic scan examination showed a stable reduction of the cystic volume and a complete clearance of the hydrocephalus. At present, the two patients are clinically normal and are leading a productive life (follow-up, 42 and 40 mo). It is important that this kind of nonneoplastic lesion be identified, in order to avoid confusion with pineal tumors and possible inappropriate treatment. Pineal cysts rarely become symptomatic. Up to the present, only 27 symptomatic cases have been described in the literature. Of those, signs of intracystic bleeding were found in 17 of the 21 cases in which the cyst contents were known. Moreover, in our own two cases, numerous hemosiderin-laden macrophages were present in the cystic fluid. We think, therefore, that intracystic bleeding has been the determining factor for the occurrence of symptoms in most of these cases. The authors underline the advantages of this type of stereotactic management, which can provide both diagnosis and treatment and thus avoid the possible risks of surgical excision and/or of radiotherapy.

Adolescent↗
PubMed1993

Uterine artery Doppler velocity waveforms in twin pregnancies.

OBJECTIVE: To compare uterine artery resistance index values in twin and singleton pregnancies, to examine eventual modifications of these values in twin pregnancies complicated by gestational hypertension and preeclampsia, and to determine whether resistance index values in twin pregnancies could predict the development of gestational hypertension and preeclampsia. METHODS: In a cross-sectional study, reference limits for gestation were constructed for the uterine artery resistance index (higher, lower, and mean values) in 96 uncomplicated twin pregnancies and compared to the reference limits constructed from 315 normal singleton pregnancies. Uterine artery resistance indexes obtained in 53 twin pregnancies complicated by either gestational hypertension or preeclampsia were compared with the newly established nomograms. The clinical efficacy of the uterine artery resistance index to predict hypertensive complications was evaluated prospectively in 64 twin pregnancies studied at 20-24 weeks' gestation. RESULTS: In both singleton and twin pregnancies, uterine artery resistance indexes decreased linearly with advancing gestation. However, twin pregnancies showed significantly different slopes and constant values, resulting in lower resistance indexes at all gestational ages examined. No significant differences were found when comparing resistance indexes in all patients with gestational hypertension or preeclampsia to the reference limits. Statistically significant differences were obtained for the higher (P < or = .05) and mean (P < or = .01) resistance indexes when the comparison was restricted to preeclamptic patients. In the twin pregnancies studied at 20-24 weeks' gestation, the diagnostic efficacy of the uterine artery resistance index for predicting the development of gestational hypertension and/or preeclampsia was disappointingly low (k < 0.10). CONCLUSIONS: Resistance index values in the uterine artery are lower in twin pregnancies than in singleton pregnancies. Gestational hypertension and preeclampsia may occur in twin pregnancies despite normal uterine artery velocity waveforms, suggesting a limited role of this measurement in the management and prediction of hypertensive complications in twin pregnancies.

Arteries↗
PubMed1993

A procedure for patient repositioning and compensation for misalignment between transmission and emission data in PET heart studies.

A procedure for patient repositioning and compensation for misalignment between transmission and emission data in positron emission tomography (PET) heart studies has been developed. Following the transmission scan (TR1), patients are moved from the scanner bed for the administration of the tracer, and repositioned when ready for the emission scan (EM1). A short postinjection transmission scan (TR2) is performed at the end of the EM1 study. TR1 and TR2 images are compared to recognize misalignment between transmission and emission studies. TR1 sinograms are compensated for misalignment to allow for a proper attenuation correction. The procedure has been tested on phantom and [18F]FDG PET heart studies. Misalignments down to 2.5 mm translation and 1 degree rotation in the transaxial plane and 4 mm in the axial direction can be recognized and compensated for. The procedure is suitable for clinical purposes, allowing reduction of patient time on the scanner bed, increased patient comfort and significant increase of patient throughput.

Deoxyglucose↗
PubMed1993

Doppler studies of deteriorating growth-retarded fetuses.

Intrauterine growth retardation continues to be one of the major problems in obstetrics and still greatly contributes to perinatal mortality and morbidity. This paper reviews the role of Doppler ultrasonography in the antenatal assessment of fetuses with intrauterine growth retardation. Recent developments in this field are described with particular emphasis on the pathophysiologic background of the hemodynamic modification of fetuses with intrauterine growth retardation. Doppler ultrasonography allows the prediction of the development of intrauterine growth retardation in selected populations and the identification among a population of small-for-gestational-age fetuses, those really at risk of unfavorable outcome. Finally, the modifications occurring after the establishment of the growth retardation with the progression of fetal deterioration are described in an attempt to clarify the natural history of this condition. To this end, the longitudinal changes of Doppler indices of placental vessels, fetal arterial vessels, fetal heart, and venous circulation are described, and their complex interrelationship is analyzed. The knowledge of these mechanisms may be useful in deciding the timing of delivery.

Cardiac Output↗
PubMed1992

Inferior vena cava flow velocity waveforms in appropriate- and small-for-gestational-age fetuses.

Reference ranges of inferior vena cava flow velocities were constructed from a cross-sectional study of 118 appropriate-for-gestational-age fetuses of 18 to 40 weeks of gestation. Blood flow velocity waveforms were recorded with color and pulsed Doppler equipment. Peak velocities and time velocity integrals were measured from inferior vena cava during systole, early diastole, and atrial contraction. The systolic-to-diastolic ratios between the peak velocities and time velocity integrals were calculated, and the reverse flow with atrial contraction was quantified as the percentage of forward flow (percentage of reverse flow). Recordings were also obtained from 79 small-for-gestational-age fetuses free of structural and chromosomal abnormalities, divided into three groups according to umbilical artery velocity waveforms: normal pulsatility index values (group 1, n = 26), pulsatility index greater than 95th percentile of our reference limits but presence of end-diastolic velocities (group 2, n = 33), and absence of end-diastolic velocities (group 3, n = 20). Fourteen fetuses of groups 2 and 3 were also studied at weekly intervals until the onset of antepartum late heart rate decelerations. In appropriate-for-gestational-age fetuses no changes were evident in peak velocities and time velocity integrals ratios, whereas the percentage of reverse flow significantly decreased with gestation. No significant differences were found between these values and those obtained in small-for-gestational-age fetuses of group 1. A significant increase of peak velocities and time velocity integrals ratios and of percentage of reverse flow was evidenced in fetuses of both group 2 and 3. The fetuses of groups 2 and 3 with a percentage of reverse flow above the 95% confidence interval showed a poorer perinatal outcome when compared with the fetuses of the same groups but with values inside the normal range. In the 14 fetuses longitudinally followed up until the onset of late heart rate decelerations a significant and progressive increase of peak velocities and time velocity integrals ratios and percentage of reverse flow was evidenced in spite of minimal changes in the pulsatility index from both umbilical artery and different peripheral fetal vessels. This study presents evidence that in small-for-gestational-age fetuses with abnormal Doppler-measured placental resistance the modified flow velocity patterns in the inferior vena cava seem to deteriorate progressively with advancing gestation.

Blood Flow Velocity↗
PubMed1992

Umbilical vein pulsations: a physiologic finding in early gestation.

OBJECTIVES: The purpose of this study was to establish the incidence of umbilical vein pulsations in normal early pregnancies and to evaluate whether these pulsations are related to Doppler-measured vascular resistances in umbilical artery or central venous flow patterns. STUDY DESIGN: We performed a cross-sectional study on 257 uneventful pregnancies at 7 to 16 weeks of gestation by means of transvaginal color and pulsed Doppler ultrasonography. Blood flow velocity waveforms were recorded from the umbilical artery, umbilical vein and, in 48 cases, also from fetal inferior vena cava. RESULTS: Pulsations in the umbilical vein were evidenced in all cases until 8 weeks. From this gestational age on pulsations progressively disappeared, becoming completely absent at greater than or equal to 13 weeks. The incidence of pulsations in the umbilical vein was unrelated to umbilical artery pulsatility index values, the incidence of absent end-diastolic flow in umbilical artery, and fetal heart rate. In the inferior vena cava, reverse flow during atrial contraction was significantly higher (p less than or equal to 0.002) in cases with umbilical vein pulsations than in those cases without pulsations at a similar gestational age. CONCLUSIONS: Pulsations in the umbilical vein are physiologically present during the first trimester of pregnancy and seem to be related to inferior vena cava flow patterns.

Adult↗
PubMed1992

Errors introduced by tissue heterogeneity in estimation of local cerebral glucose utilization with current kinetic models of the [18F]fluorodeoxyglucose method.

The effects of tissue heterogeneity on the estimation of regional cerebral glucose utilization (rCMRglc) in normal humans with [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG) and positron emission tomography (PET) were compared with respect to the various kinetic models of the [18F]FDG method. The kinetic models were conventional homogeneous tissue models of the [18F]FDG method, with (4K Model) and without (3K Model) a rate constant to account for an apparent loss of [18F]2-fluoro-2-deoxy-D-glucose-6-phosphate ([18F]FDG-6-P), and a tissue heterogeneity model (TH Model). When either of the kinetic models designed for homogeneous tissues was applied to heterogeneous tissues, estimates of the rate constant for efflux of [18F]FDG from the tissue (k2*) and of the rate constant for phosphorylation of [18F]FDG (k3*) decreased as the duration of the experimental period was increased. When the 4K Model was used, estimates of the rate constant for the apparent dephosphorylation of [18F]FDG-6-P (k4*) were significantly greater than zero and fell with increasing duration of the experimental period. Although the TH Model included no term to describe an apparent dephosphorylation of [18F]FDG-6-P, the fit of the TH Model to the time course of total tissue radioactivity was at least as good as and often better than the fit of the 4K Model in the 120-min period following the pulse of [18F]FDG. Hence, the high estimates of k4* found in PET studies of less than or equal to 120 min can be explained as the consequence of measuring radioactivity in a heterogeneous tissue and applying a model designed for a homogeneous tissue; there remains no evidence of significant dephosphorylation of [18F]FDG-6-P in this time period. Furthermore, use of the 4K Model led to an overestimation of rCMRglc; whole-brain glucose utilization calculated with the 4K Model was greater than 20% higher than values usually obtained in normal humans by the model-independent Kety-Schmidt technique. rCMRglc was accurately estimated by the TH Model and, in experimental periods sufficiently long to minimize the effects of tissue heterogeneity, also by the original 3K Model of the deoxyglucose method.

Adult↗
PubMed1992

The effect of ageing on plasma albumin and plasma protein binding of diazepam, salicylic acid and digitoxin in healthy subjects and patients with renal impairment.

1. Plasma albumin concentration was measured in 118 healthy subjects (aged between 18 and 87 years), in 95 renal patients with creatinine clearances between 15 and 50 ml min-1 (aged between 14 and 79 years) and in 101 uraemic patients maintained on chronic haemodialysis (aged between 27 and 83 years). 2. There was a significant (P less than 0.001) negative correlation between albumin concentration and age in healthy subjects, but no correlation in patients with low creatinine clearance or in uraemic patients. 3. The ex vivo plasma binding of diazepam (1 microM), salicylic acid (2 mM) and digitoxin (37 nM) was studied in groups of age-selected young and aged healthy subjects in patients with low creatinine clearance and in patients with uraemia. The unbound fractions of diazepam and salicylic acid were about double in old compared with young healthy subjects whereas they were similar in young and old patients with lowered creatinine clearance. In uraemic patients, ageing did not affect the binding of salicylic acid whereas the unbound fraction of diazepam was slightly but significantly greater in elderly subjects. The unbound fraction of digitoxin was independent of age in both healthy subjects and in those with renal disease. 4. Decreased plasma binding of diazepam and salicylic acid was partially corrected by extensive dialysis of plasma. The lower plasma binding of diazepam and salicylic acid associated with ageing may be ascribed to the effects of endogenous displacers and to hypoalbuminaemia. The influence of these two factors appears to be drug-dependent.

Adolescent↗
PubMed1992

Prediction of fetal outcome in small for gestational age fetuses: comparison of Doppler measurements obtained from different fetal vessels.

Blood flow velocity waveforms were recorded from different vascular districts including umbilical artery, descending aorta, renal artery, internal carotid artery and middle cerebral artery in a population of 120 small for gestational age fetuses free from structural and chromosomal abnormalities. The pulsatility index from each vessel as well as the ratios between the pulsatility indices from peripheral and cerebral vessels were calculated and related to perinatal outcome. The pulsatility index of middle cerebral artery resulted the most efficient measurement to predict the development of perinatal adverse outcome when each vessel was considered singularly, however, better results were achieved when the ratios between pulsatility indices were related to perinatal outcome; this is mot evident for the ratio between the pulsatility indices of umbilical artery and middle cerebral artery. Our results suggest the usefulness of this ratio in differentiating small for gestational age fetuses at risk of unfavorable outcome.

Adult↗
PubMed1992

Accelerated cardiac growth and abnormal cardiac flow in fetuses of type I diabetic mothers.

OBJECTIVES: To determine the growth patterns of the fetal heart and the development of cardiac function during gestation in fetuses of diabetic mothers, and to compare these findings with those of normal fetuses. METHODS: Serial M-mode and Doppler echocardiographic recordings were made at 4-week intervals in 14 fetuses of well-controlled type I insulin-dependent diabetic mothers and in ten control fetuses at 20-36 weeks' gestation. The following variables were measured: interventricular septal thickness, left ventricular wall thickness, right ventricular wall thickness, ratio between the peak velocities during early passive ventricular filling and active atrial filling at the level of the atrioventricular valves, peak velocities, and time to peak velocity at the level of the ascending aorta and pulmonary artery. RESULTS: In both groups of fetuses, all of the indices increased linearly with gestation. However, fetuses of diabetic mothers showed significant differences in the slope and intercept values for the function describing the growth of the interventricular septum (P less than or equal to .001) and the right and left ventricular wall thicknesses (P less than or equal to .01), resulting in accelerated cardiac growth. The function describing the development of the ratios between early and active ventricular filling showed differences in slope and intercept values at the level of both the mitral (P less than or equal to .001) and tricuspid valves (P less than or equal to .001), resulting in a lower rate of increase during diabetic pregnancy when compared with control fetuses. Significantly higher intercept values were found in the functions describing the increase of peak velocities in the aorta and pulmonary artery in fetuses of diabetic mothers (P less than or equal to .01), whereas the slopes were similar to those of control fetuses. No differences were found in the time to peak values between the groups of fetuses. No relationships were found between the echocardiographic results and the metabolic control of pregnancy or fetal characteristics. CONCLUSIONS: This study suggests that strict maternal diabetes control does not exclude accelerated fetal cardiac growth and abnormal development of cardiac function.

Adult↗
PubMed1992

Changes of pulsatility index from fetal vessels preceding the onset of late decelerations in growth-retarded fetuses.

Thirty-six growth-retarded fetuses selected from a population of 214 cases were studied by Doppler ultrasonography at weekly intervals for at least 4 weeks between the diagnosis of Doppler abnormalities suggestive of the existence of the brain-sparing effect (ie, ratio between umbilical artery and middle cerebral artery pulsatility indexes [PIs] above the 95th percentile of our reference limits) to the onset of antepartum late fetal heart rate (FHR) decelerations. Recordings were made from the umbilical artery, descending aorta, renal artery, internal carotid artery, and middle cerebral artery and the PIs were calculated. Statistically significant changes in PI occurred in all the vessels studied. However, different trends were found when the modifications in cerebral vessels were compared with those in fetal peripheral vascular beds and in the umbilical artery. In cerebral arteries, a nadir of vasodilatation was reached 2 weeks before the onset of antepartum late FHR decelerations, whereas significant changes in the peripheral and umbilical vessels occurred close to the onset of abnormal FHR patterns. This study demonstrates that despite a brain-sparing effect, there are further Doppler-detectable modifications in fetal circulation that differ between the cerebral and peripheral vascular beds.

Cerebrovascular Circulation↗
PubMed1992

Interindividual variability in the concentrations of albumin and alpha-1-acid glycoprotein in patients with renal or liver disease, newborns and healthy subjects: implications for binding of drugs.

The concentrations of human plasma albumin (HPA) and alpha-1-acid glycoprotein (AAG) were measured in the serum obtained from 84 healthy subjects, 56 umbilical cords, 41 patients with renal failure, 65 patients maintained on chronic hemodialysis and 46 patients with liver cirrhosis. Severity of liver dysfunction was assessed with the use of Pugh et al. [1973] classification. Of the cirrhotic patients, 12, 22 and 12 patients were classified as mild, moderate and severe liver dysfunction, respectively. The coefficient of variation of AAG was greater than HPA in all groups of subjects, and the variability of HPA and AAG is increased in patients compared to healthy subjects. As the liver dysfunction progresses, HPA concentration decreases whereas, the average AAG concentration is not changed in mild, moderate and severe liver dysfunction. The coefficients of variation for HPA and AAG in moderate and severe liver disease is over twice those for healthy subjects. The concentration of HPA is normally distributed in all groups of subjects, with the exception of the cord serum. The frequency distribution of AAG was normal in healthy subjects whereas, it was asymmetric, being positively skewed, in newborn, in renal and liver patients. The wide interindividual variability and the not-normal frequency distribution of AAG in liver or renal patients make its mean of little value in defining a group. Neither HPA nor AAG correlated with the clearance of creatinine in renal patients. In liver disease, HPA and AAG did not correlate with GPT and GOT activities, prothrombinic activity and bilirubin concentration. HPA did not correlate with AAG in any group.

Adolescent↗