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Biomedical subjects

D Teitel

Publications and source records attributed to D Teitel.

14 recordsLinked to original sources
PubMed2001

Sequential magnetic resonance monitoring of pulmonary flow with endovascular stents placed across the pulmonary valve in growing Swine.

BACKGROUND: Patients with endovascular stent implantation for the treatment of right ventricular outflow tract obstruction are often left with incomplete relief of the obstruction and significant pulmonary regurgitation. A noninvasive and reproducible method for monitoring such patients is desirable. MRI in the presence of a stent, however, has to overcome the problem of potential metallic artifacts. METHODS AND RESULTS: Under x-ray fluoroscopic guidance, endovascular nitinol stents were placed across the pulmonary valve in 6 young pigs to induce pulmonary regurgitation. Five additional pigs served as controls. Initial MRI was performed after 2 days (13.5+/-1.8 kg) and follow-up after 3 months (32+/-2.9 kg). Pulmonary flow volumes and regurgitant fraction were quantified by velocity-encoded cine (VEC) MRI through (VEC-TS) and distal to (VEC-DS) the stent. VEC-TS was compared with VEC-DS and volumetric measurements of left and right ventricular stroke volumes provided by cine MRI ("gold standard"). Antegrade and retrograde pulmonary flow volumes by VEC-TS were slightly but significantly less than those with VEC-DS and cine MRI. Excellent correlations (r>0.97) for phasic pulmonary flow volumes as measured by VEC-TS and VEC-DS were shown. Pulmonary regurgitant fraction increased from 32.8+/-15% to 49.6+/-17% (P<0.05) over the course of 3 months with VEC-TS. CONCLUSIONS: MRI demonstrates the progression of pulmonary regurgitation in growing swine. VEC MRI has the ability to quantify pulmonary blood flow inside the lumen of nitinol stents. MRI appears to be ideally suited for monitoring patients with endovascular nitinol stents in the pulmonary artery or pulmonary valve position.

Alloys↗
PubMed1992

Chemoreceptor responsiveness in fetal sheep.

Fetal peripheral chemoreceptor responses to arterial O2 saturation and changes in PCO2 have not yet been quantitated. In 24 late-term chronically instrumented fetal sheep, we measured the heart rate response to acute hypoxemia induced by uterine arterial occlusion at various resting O2 saturations (25-86%) and at induced reductions and increases in baseline O2 saturation. As an index of fetal chemoreceptor responsiveness we calculated the fall in heart rate divided by the fall in arterial O2 saturation (delta HR/delta sat). delta HR/delta sat was inversely related to resting O2 saturation at levels less than 65%, but greater than 65% this relationship was no longer present. However, an induced increase in baseline O2 saturation from 66 +/- 12 to 76 +/- 10% decreased delta HR/delta sat from 2.6 +/- 1.6 to 1.8 +/- 1.0, indicating that when resting O2 saturation is greater than 65% there may be adaptation of peripheral chemoreceptors. Below 65%, an induced decrease in baseline O2 saturation increased delta HR/delta sat (to 3.8 +/- 1.8), suggesting a lack of adaptation to lower O2 saturations. Concomitant changes in PCO2, or differences in baseline PCO2, did not affect delta HR/delta sat during uterine arterial occlusion, which suggests that there is no interdependence between O2 and CO2 as a stimulus for the fetal peripheral chemoreceptor. However, acute hypercapnia (n = 24 in 8 fetal sheep) induced bradycardia. Furthermore, this bradycardia was related to the increase in fetal arterial PCO2. We conclude that the fetal peripheral chemoreceptor is sensitive to hypoxemia and hypercapnia and that the hypoxemia response is accentuated with decreases in initial O2 saturation.

Acute Disease↗
PubMed1989

The effects of changes in heart rate and aortic systolic pressure on left ventricular myocardial oxygen consumption in lambs.

To determine whether changes in heart rate and aortic systolic pressure contribute equally to the determination of left ventricular myocardial oxygen consumption, we independently varied heart rate and pressure and compared the resultant oxygen consumption for similar rate-pressure products. In 6 young lambs which underwent atrioventricular node ablation, we varied heart rate by ventricular pacing at 250 beats/min, 300 beats/min, and 120 beats/min while aortic pressure remained stable and varied aortic systolic pressure by infusion of phenylephrine (to 132 +/- 15 mm Hg and 155 +/- 14 mm Hg) and by infusion of sodium nitroprusside (to 79 +/- 6 mm Hg) while heart rate was maintained stable at 200 beats/min. The 3 levels of change in aortic systolic pressure were chosen so that the ratepressure product during the pressure changes matched the rate-pressure product during the heart rate changes. We found that left ventricular myocardial oxygen consumption was the same at all 3 levels of the rate-pressure product whether heart rate was changed and pressure remained stable or pressure was changed and heart rate remained stable. Also, the correlation between oxygen consumption and the rate-pressure product was similar for both heart rate and pressure changes. During nitroprusside infusion at a fixed heart rate, oxygen extraction was significantly lower than during pacing at a heart rate of 120 beats/min when the rate-pressure product was comparable because of the direct vasodilatory effects of nitroprusside. We conclude that heart rate and aortic systolic pressure contribute equally to left ventricular myocardial oxygen consumption at the same rate-pressure product, even though there may be differences in myocardial blood flow and oxygen extraction.

Animals↗
PubMed1988

The role of beta-adrenoreceptor stimulation and contractile state in the preterm lamb's response to altered ductus arteriosus patency.

A model of patent ductus arteriosus in premature lambs was created to study the relative importance of beta-adrenoreceptor stimulation and increased myocardial contractility. In 39 fetal lambs (133 +/- 2, +/- SD days gestation, term 145 days), the ductus arteriosus was infiltrated with formalin, and a snare was placed around it to regulate its patency. One day later, the lambs were delivered, given sheep surfactant, paralyzed, and mechanically ventilated. Microsphere measurements of left ventricular output were made between 4 and 6 h after delivery. When the ductus was opened, there was no change in heart rate, but there were significant increases in left ventricular output, stroke volume, left ventricular end-diastolic pressure, and peak dP/dt. The increase in peak dP/dt due to opening the ductus was greater than that due to an increase in left ventricular end-diastolic pressure alone and was accompanied by an increase in norepinephrine secretion from the left ventricle. Propranolol (1 mg/kg) was used to evaluate the effect of beta-adrenergic tone on left ventricular output and contractility. The left atrium was paced in both control and propranolol-treated lambs. When the ductus was closed, propranolol significantly decreased stroke volume and peak dP/dt without changing left ventricular end-diastolic pressure or systemic vascular resistance. During a saline volume load (50 ml/kg over a 3-min period), propranolol-treated lambs had a reduced stroke volume and peak dP/dt despite similar values of left ventricular end-diastolic pressure and resistance as those of control lambs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Redistribution of regional blood flow and oxygen delivery in experimental cyanotic heart disease in newborn lambs.

Redistribution of regional blood flow is an important compensatory response to acute hypoxemia which preserves oxygen delivery to the most vital organs. It is not known if this change in blood flow persists when hypoxemia is prolonged, as occurs in cyanotic congenital heart disease. Chronic hypoxemia was produced in newborn lambs by creating pulmonary stenosis and an atrial septal defect. Oxygen saturation was maintained at 60-70% of control for 2 wk. Distribution of cardiac output was then measured with radionuclide-labeled microspheres. As compared with control, chronic hypoxemia did not alter total cardiac output. Regional blood flow was redistributed, however, the pattern of this redistribution was different from that seen during acute hypoxemia. Myocardial and cerebral blood flows, which increase during acute hypoxemia, return to control levels during chronic hypoxemia. Renal, splenic, gastrointestinal, carcass, and skin blood flows remain decreased. Hemoglobin gradually increases so that after 2 wk of hypoxemia total systemic oxygen delivery returns toward control. However, oxygen delivery to all organs except the heart and brain is reduced. Thus, although cardiac output and total systemic oxygen delivery return toward normal during chronic hypoxemia, these measurements may not reflect important regional variations in blood flow and oxygen delivery. Decreased oxygen and substrate delivery to the gastrointestinal tract, liver, and carcass may account for the alterations of metabolism and growth seen in the newborn with cyanotic congenital heart disease.

Animals↗
PubMed1987

Effects of birth-related events on blood flow distribution.

At birth, the cardiovascular system changes dramatically; arterial blood pressure, heart rate, and cardiac output increase, and blood flow distribution undergoes regional changes. To determine whether these changes are related to certain events occurring at birth, we studied 18 chronically instrumented fetal sheep at 133-138 days gestational age. We measured fetal vascular pressures and heart rate and injected radionuclide-labeled microspheres to determine combined ventricular output and its distribution. Rhythmic ventilation of the fetuses with a gas mixture that produced no change in arterial blood gases decreased heart rate slightly from 173 +/- 25 to 152 +/- 16 beats/min, but changed neither mean arterial blood pressure nor combined ventricular output. Ventilation with oxygen decreased mean descending aortic and pulmonary arterial pressures, but had no significant effect on heart rate or combined ventricular output; subsequent umbilical cord occlusion had no significant effect on these variables. There was a redistribution of blood flow, however. Ventilation alone increased pulmonary blood flow from 159 +/- 68 to 641 +/- 513 ml.min-1.100 g wet weight-1, and oxygenation increased it further to 1040 +/- 426. Ventilation alone and ventilation with O2 decreased blood flow to most other fetal organs, notably the adrenal glands, brain, and heart, in a manner related to changes in arterial oxygen tension. Occlusion of the umbilical cord increased blood flow to the adrenal glands and brown fat, and also to the liver from the portal vein and hepatic artery. The changes in regional blood flow initiated by ventilation, oxygenation, and umbilical cord occlusion are similar to those occurring at birth and may play an important role in postnatal adaptation.

Animals↗
PubMed1987

Novel monocyte-like properties of microglial/astroglial cells. Constitutive secretion of lysozyme and cystatin-C.

Evidence implicates cells belonging to the mononuclear phagocytic system (MPS) in the development of some forms of amyloidosis (10, 22). Whether or not the MPS is involved in central nervous system amyloidosis is not known. As a first step to address this issue, microglial and astroglial cells isolated from mouse brains were cultured and characterized as to the properties they may share with other members of the MPS. It was shown by light and electron microscopy that both cell types phagocytose latex particles, but that only microglial cells engulf immunoglobulin sensitized erythrocytes. By means of immunohistochemical, immunofluorescence, and immunoblotting techniques, it was established that the cells contain and secrete lysozyme as well as the proteinase inhibitor cystatin-C (-gamma trace). Cystatin-C was distributed in the cytoplasm and the nucleus and was strikingly associated with filaments and bundles of fibrils. Another enzyme, commonly used to distinguish cells belonging to the MPS, is alpha-naphthyl butyrate esterase. Shortly after their isolation, only the microglial cells were positive, but on continued culturing, increasing numbers of astroglial cells became positive for alpha-naphthyl butyrate esterase. By day 22, almost all of the cells were positive. Freshly isolated cells were negative for the monocyte-specific antigen Mac-1. However, after 4 days, cells with the morphology of microglia had become positive, whereas astroglia failed to exhibit this antigen with up to 22 days in culture. Thus, both astroglia and microglia have properties in common with cells of the MPS which may be useful for future studies. However, on fresh isolation only microglia were indistinguishable from monocytes for all features tested.

Animals↗
PubMed1986

Perinatal myocardial infarction: a case report and review of the literature.

Myocardial infarction in the perinatal period is a rare occurrence, usually associated with congenital heart lesions or isolated coronary artery abnormalities. In the absence of structural heart disease the most common etiologies are intrauterine asphyxia and thromboembolic coronary occlusion. A paradoxical embolus usually arises from a thrombus in the ductus venosus or umbilical vein and reaches the coronary circulation via normal fetal circulatory pathways. We describe a case of perinatal myocardial infarction due to thromboembolism of the coronary artery secondary to an intrauterine renal vein thrombosis. The difficulties encountered in making an accurate premortem diagnosis are emphasized as well as the poor prognosis of myocardial infarction in the perinatal period.

Coronary Disease↗
PubMed1985

Chronic hypoxemia in the newborn lamb: cardiovascular, hematopoietic, and growth adaptations.

We have created a model of chronic hypoxemia in the newborn lamb by decreasing pulmonary blood flow in the presence of an atrial septal defect. Via a left lateral thoracotomy, we place an inflatable balloon around the pulmonary artery and perform an atrial septostomy under direct vision. We also insert several vascular catheters and place an electromagnetic flow transducer around the ascending aorta. Three days after surgery, we inflated the balloon in 11 lambs such that arterial oxygen saturation decreased to 60 to 75%. Studies were performed on these lambs twice weekly and weekly on 12 normoxemic lambs. Growth decreased sharply (47 +/- 123 versus 221 +/- 82 g/day) at the onset of hypoxemia and remained low, although oxygen consumption followed the normal gradual decline. Heart rate remained elevated throughout the study. Arterial PCO2 levels decreased from 40 +/- 5 to 35 +/- 7 torr and remained low. Systemic blood flow decreased at balloon inflation but quickly returned to normal. Mixed venous saturation was low, but could decrease further with shivering. Systemic oxygen delivery decreased initially but returned to normal as Hb concentration rose (from 9.4 +/- 1.5 to 12.5 +/- 2.2 g/dl). P50 increased normally over the study period. Four of the 11 hypoxemic lambs died during the study. These data show that, in the chronically hypoxemic newborn, systemic oxygen delivery is maintained primarily by a rising Hb. Total body oxygen consumption is maintained at rest but is redistributed away from anabolic requirements and toward cardiorespiratory work. This signal to decrease growth occurs despite less than maximal oxygen extraction at rest.

Animals↗
PubMed1985

Perinatal oxygen delivery and cardiac function.

In this review, we have considered interrelationships between blood flow and oxygen requirements of the body during fetal and neonatal development. During fetal life, blood is oxygenated in the placenta and returns to the fetus through the umbilical vein. The ductus venosus serves as a bypass of umbilical venous blood from the hepatic microcirculation. Preferential streaming of blood in the inferior vena cava facilitates delivery of well-oxygenated ductus venosus blood to the brain and heart. During fetal stress of hypoxia or umbilical cord compression, flow through the liver and ductus venosus is modified to facilitate oxygen delivery to the fetal body and local organ vascular responses, and to maintain blood flow and oxygen delivery to vital organs, such as the brain, heart, and adrenal gland. During fetal life, immaturity of the fetal myocardium accounts for limited ability for cardiac output to be augmented when ventricular filling pressure is increased above the resting level; yet immediately after birth, cardiac output increases dramatically. Experimental evidence points to an important role of prenatal thyroid hormone in maturation of the myocardium for postnatal requirements. In association with the increase in oxygen requirements after birth, cardiac output increases, but because resting requirements for blood flow are high, there is a limited ability for cardiac output to be increased further. With postnatal development, cardiac output requirements in relation to body weight decrease, partly in parallel with reduced oxygen requirements related to body weight, but also as a result of rightward shift of the oxygen dissociation curve as fetal hemoglobin is replaced by adult hemoglobin. Understanding the circulatory and metabolic changes that occur in the perinatal period and the mechanisms of response to stress is important in management of the newborn infant with cardiorespiratory distress.

Animals↗
PubMed1983

Developmental changes in oxygenation and circulatory responses to hypoxemia in lambs.

We studied moderate [fractional inspired O2 (FIO2) 0.09] and severe (FIO2 0.06) hypoxemia in 21 lambs (group 1, 1 wk old; group 2, 3-4 wk old; group 3, 5-7 wk). With moderate hypoxemia, all groups increased heart rate, cardiac output, and pulmonary arterial pressure and decreased systemic and pulmonary vascular resistance; cardiac output and pulmonary arterial pressure increases were less in group 1, because of higher resting values. With severe hypoxemia, heart rate increased similarly, cardiac output was unchanged, and aortic pressure fell associated with severe metabolic acidosis or arrhythmias. Regional blood flow changed similarly in all groups; heart and brain flow increased, carcass flow was unchanged, and skin, GI tract, and kidney flow fell. O2 consumption (VO2) and mixed venous PO2 decreased, though O2 saturation was higher in group 1 due to the lower O2 half-saturation pressure of hemoglobin. With a given decreased VO2 there was more metabolic acidosis in older lambs and an increased VO2 after termination of hypoxemia, suggesting greater O2 debt. As in the fetus, young lambs are better able to tolerate a decreased VO2 than older lambs.

Aging↗
PubMed1981

Metabolic abnormalities in the idiopathic Fanconi syndrome: studies of carbohydrate metabolism in two patients.

Two patients with idiopathic Fanconi syndrome and glucose intolerance were studied from a metabolic perspective. They had fasting hyperglycemia, massive glucosuria, insulinopenia, ketosis, and elevated serum free fatty acids. There was a markedly blunted insulin secretory response to glucagon, tolbutamide, glucose, and arginine. One patient had the findings of diabetic retinopathy and a sensory neuropathy. Neither patient could convert galactose to glucose, but they did not have galactosemia. As a result of these studies, and previous reports in which similar changes were noted, we conclude that diabetes mellitus may occur in patients who have had idiopathic Fanconi syndrome for many years.

Adolescent↗
PubMedDate not supplied

Pediatric angiocardiography with iohexol.

A nonionic contrast medium (iohexol) was evaluated for safety and efficacy in pediatric angiocardiography in this study of 15 patients, age 6 to 82 months. Patients carried a preliminary diagnosis of congenital heart disease. Subjects were injected with iohexol, 350 mg iodine/ml of solution with an average volume of 2.46 ml/kg of body weight at a rate of 9 to 14.5 ml/sec. The parameters evaluated included vital signs, intravascular BP, ECG changes, discomfort, and adverse reactions. No adverse reactions were noted in 14 of 15 patients. No significant changes in axillary temperature of ECG were observed. Intravascular blood pressure showed only moderate changes. After 24 hours, creatine phosphokinase (CPK) plasma concentrations increased significantly. Serum electrolytes remained unchanged. Image quality was deemed excellent considering variations in injection site and flow condition of the heart. Iohexol caused remarkably little discomfort and no adverse effects.

Angiocardiography↗