Search PubMed⌕ Search

Biomedical subjects

D F Teitel

Publications and source records attributed to D F Teitel.

At least 55 records · Page 3Linked to original sources
PubMed1991

Acceleration of blood flow velocity in the carotid artery and myocardial contractility in the newborn lamb.

We investigated the influence of quantitative changes in myocardial contractile state, reflected by changes in the end-systolic pressure-volume relationship (its slope and volume intercept) and by changes in the slope of the relationship between change in pressure per unit time and end-diastolic volume induced by beta-adrenergic stimulation or inhibition, on the Doppler derived blood flow velocity wave form of the carotid artery, using a newborn lamb model. Acceleration time of the velocity wave form was investigated during control state I, during 4 and 8 micrograms/kg/min dobutamine infusion, during control state II, and during 0.5 mg/kg propranolol infusion, respectively. Using multiple linear regression analysis with dummy variables, confounding effects such as interanimal variability were removed. Acceleration time showed a strong relationship to both the slope and the volume intercept of the end-systolic pressure-volume relationship and to the change in pressure per unit time-end-diastolic volume relationship. The relations appeared to be independent of aortic pressure and relative resistance in the vascular bed of the carotid artery. These results indicate that acceleration of cerebral blood velocity may prove to be useful in assessing changes in myocardial contractile state of the newborn.

Animals↗
PubMed1990

Myocardial and systemic oxygenation during severe hypoxemia in ventilated lambs.

We studied the interrelationships among myocardial oxygenation, cardiac output, and systemic oxygenation during acute progressive hypoxemia in the paralyzed and mechanically ventilated lamb. Fractional inspired concentration of oxygen was reduced in five steps to a minimum of 0.05, decreasing arterial oxygen content (CaO2) from 10.9 +/- 2.4 to 2.8 +/- 0.5 ml/dl. Heart rate and stroke volume did not change at any step so that systemic oxygen transport decreased with CaO2. Systemic oxygen consumption fell at CaO2 less than 6 ml/dl. Left ventricular blood flow at maximal hypoxemia increased 277% (249 +/- 27 to 938 +/- 118 ml.min-1.100 g-1) so that left ventricular oxygen delivery and oxygen consumption were maintained. Evidence of anaerobic metabolism occurred when CaO2 was less than four (increase in arterial lactate and hypoxanthine), whereas at this level there was no evidence of inadequate myocardial oxygenation as determined by normal subepicardial: subendocardial blood flow and absence of net lactate production, although coronary sinus PO2 decreased. Although myocardial, cerebral, and adrenal blood flows increased, there was no redistribution of blood flow away from the viscera and skin.

Animals↗
PubMed1990

Changes in the pulmonary circulation during birth-related events.

At birth, pulmonary vascular resistance decreases dramatically, allowing pulmonary blood flow to increase and oxygen exchange to occur in the lungs. To determine the extent to which ventilation of the fetus's lungs, oxygenation of the lungs, and umbilical cord occlusion can account for this decrease in resistance, we studied 16 chronically instrumented, near-term sheep fetuses in utero. We performed the experiment in a sequential fashion: we first studied the effects of ventilation alone (without oxygenation) on pulmonary vascular resistance and blood flow, and then determined the additive effects of oxygenation and cord occlusion. We calculated pulmonary vascular resistance from measurements of vascular pressures and measurements of pulmonary blood flow obtained by injecting radionuclide-labeled microspheres. We found that ventilation alone caused a large but variable increase in pulmonary blood flow, to 401% of control, no change in pulmonary arterial pressure, and a doubling of left atrial pressure. Thus, pulmonary vascular resistance fell dramatically, to 34% of control. Oxygenation caused a modest further increase in pulmonary blood flow and a decrease in mean pulmonary arterial pressure, so resistance fell to 10% of control. Umbilical cord occlusion caused no further changes in pressure, flow, or resistance. Unexpectedly, the fetuses' pulmonary blood flow responses to ventilation fell into two groups: the mean increase was maximal in eight of the 16 fetuses but was only 20% of the cumulative increase in the other eight. We found no differences between the two groups of fetuses to explain their different responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Magnetic resonance imaging of congenital heart disease: sensitivity and specificity using receiver operating characteristic curve analysis.

MRI has shown promise for the evaluation of various congenital heart lesions. The current study was designed to assess the sensitivity and specificity of the technique for the evaluation of all major anatomic elements of the heart affected in simple and complex congenital heart disease. MR images of 51 patients (31 males and 20 females, ages 3 to 69 years) with a total of 110 congenital heart lesions were reviewed by a panel of two cardiac radiologists and one pediatric cardiologist, who assessed the cardiac pathoanatomy without knowledge of clinical details and assigned a confidence level to each diagnosis. The true diagnosis was established independently by the findings of angiocardiography and catheterization as well as by surgery, where applicable. ROC curves were generated from the responses, and the sensitivity at a specificity level of 90% was determined. MRI was shown to have a high sensitivity in evaluating great vessel relationships (100%), thoracic aorta abnormalities (94%), ASDs (91%) and VSDs (100%), visceroatrial situs (100%), and loop (100%). Three of five anomalies of the pulmonary and systemic veins were diagnosed by MRI. Right ventricular outflow obstructions (95%) were detected with a much higher sensitivity than lesions of the other valves (aortic valve 52%, mitral valve 62%, tricuspid valve 76%). Spin-echo MRI is a sensitive and specific method for the noninvasive assessment of congenital heart disease, with limitations in the evaluation of some valvular anomalies.

Adolescent↗
PubMed1989

The young lamb can increase cardiovascular performance during isoflurane anesthesia.

Cardiac output and myocardial blood flow decrease dramatically in a dose-dependent pattern in the young lamb during isoflurane anesthesia. This raises important questions about the ability of the young lamb to increase myocardial performance if oxygen delivery were compromised by a decrease in oxygen content during anesthesia and surgery. To investigate the ability of the young lamb to increase oxygen delivery during isoflurane anesthesia, the response to hypoxemia, which is known to increase myocardial performance, was studied in awake 1-week-old lambs. Mean systemic arterial pressure, heart rate, cardiac output, and regional distribution of blood flow were measured during three states: awake, 1.0 minimum alveolar concentration (MAC) of isoflurane in an FIO2 of 1.0, and 1.0 MAC of isoflurane in an FIO2 of 0.09. Stroke volume, total body and myocardial oxygen consumption, and fractional extraction of oxygen were calculated for the total body and for the myocardium. Isoflurane anesthesia decreased mean systemic arterial pressure (70 +/- 8 mmHg), heart rate (222 +/- 29 beats/min), and cardiac output (277 +/- 72 ml.kg-1.min-1) significantly (43 +/- 11 mmHg, 163 +/- 20 beats/min, 191 +/- 34 ml.kg-1.min-1). Hypoxemia returned heart rate to control (191 +/- 23 beats/min), increased stroke volume (1.71 +/- 0.2 ml/kg) above both control (1.23 +/- 0.2 ml/kg) and 1.0 MAC isoflurane levels (1.19 +/- 0.3 ml/kg), and increased cardiac output (325 +/- 61 ml.kg-1.min-1) above the level during 1.0 MAC isoflurane.

Anesthesia, General↗
PubMed1988

Short-term hemodynamic effects of captopril in infants with congestive heart failure.

We studied the short-term hemodynamic effects of captopril in ten infants with congestive heart failure secondary to large left-to-right shunts who were refractory to routine medical management with digoxin and diuretics. During cardiac catheterization, captopril (0.5 to 1.0 mg/kg) was administered by nasogastric tube. For the entire group, mean systemic blood flow, pulmonary blood flow, and the pulmonary-to-systemic blood flow ratio did not change significantly after captopril administration. However, in the seven patients in whom baseline systemic vascular resistance was greater than 20 U/m2, captopril decreased the pulmonary-to-systemic blood flow ratio. In contrast, in the three patients in whom baseline systemic vascular resistance was less than 20 U/m2, captopril increased the pulmonary-to-systemic blood flow ratio. We conclude that captopril acutely decreases the pulmonary-to-systemic blood flow ratio in infants with large left-to-right shunts who have elevated systemic vascular resistance. Renal function must be monitored closely when using captopril.

Captopril↗
PubMed1988

Effect of beta-adrenergic receptor blockade on responses to acute hypoxemia in lambs.

We studied the effects of beta-adrenergic receptor blockade on general circulatory and metabolic responses to moderate (FIO2 = 0.09) acute hypoxemia in newborn (protocol 1) and 3-wk-old (protocol 2) lambs, and on regional blood flow distribution in newborn lambs (protocol 1). Via a left thoracotomy we placed an electromagnetic flow transducer around the ascending aorta and inserted various vascular catheters. After 2 days of recovery, the lambs were studied. In protocol 1, we measured cardiovascular variables and regional blood flow distribution during control conditions, after 45 min of acute hypoxemia, and after 0.5 mg/kg of propranolol during acute hypoxemia. In protocol 2, we measured cardiovascular variables during control conditions and after 45 min of acute hypoxemia with and without propranolol pretreatment. In both groups, propranolol limited the increase in cardiac output and heart rate caused by hypoxemia, and thus decreased oxygen delivery. However, propranolol also decreased oxygen consumption so that pulmonary arterial pO2 was either higher (protocol 1) or the same (protocol 2) as during acute hypoxemia alone. Neither metabolic acidosis nor hypothermia ensued. In protocol 1, propranolol decreased renal, carcass, and most importantly, myocardial blood flows. However, myocardial O2 consumption also fell, coronary sinus pO2 increased, and blood was redistributed toward the subendocardium, suggesting that myocardial perfusion improved. Thus, beta-adrenergic receptor blockade during acute moderate hypoxemia may have a beneficial effect by reducing total body and myocardial oxygen demand in excess of the reduction in oxygen delivery.

Acute Disease↗
PubMed1988

Chronic anemia in the newborn lamb: cardiovascular adaptations and comparison to chronic hypoxemia.

The cardiovascular adaptations to chronic anemia were studied in the newborn lamb and then compared with the adaptations to chronic hypoxemia. Eight chronically instrumented newborn lambs underwent repeat isovolemic exchange transfusions to maintain their Hb concentrations at 60% of normal for age. Hemodynamic studies were performed twice weekly for 2 wk after which time regional blood flows were measured using radionuclide-labeled microspheres. The major compensatory responses after 2 wk of anemia were moderate increases in heart rate (229 +/- 20 versus 187 +/- 15 beats/min) and cardiac output (226 +/- 36 versus 165 +/- 38 ml/kg/min), an increase in fractional extraction of oxygen (65 versus 40%), and a redistribution of regional blood flow. Blood flows to the heart and brain increased whereas blood flows to the viscera and carcass did not change. These compensatory responses were different from those that occur during chronic hypoxemia: specifically, cardiac output did increase, growth was not suppressed, and the pattern of redistribution of regional blood flows was different. The dissimilar effects of anemia (decreasing systemic oxygen content) versus hypoxemia (decreasing systemic oxygen tension) on local tissue receptors and peripheral chemoreceptors may account for these differences.

Adaptation, Physiological↗
PubMed1988

Regulation of cardiac output with controlled heart rate in newborn lambs.

To determine the factors regulating cardiac output in newborn lambs and to examine the effects of age after birth, we altered heart rate, afterload, preload, and myocardial contractility in eight younger lambs, 5 to 13 days old, and seven older lambs, 15 to 36 days old. To control heart rate, we ablated the atrioventricular node by injecting formalin into the region of the node, and paced the right ventricle at a baseline heart rate of 200 beats/min. After the lambs recovered from surgery, we performed two protocols. In the first protocol we assessed the effects of changing heart rate by pacing the ventricle at various rates. We also examined the effect of altering afterload and preload at a fixed heart rate: afterload was increased by infusing phenylephrine and decreased by infusing nitroprusside. Preload was increased by infusing blood or 0.9% NaCl solution over 2 min. In the second protocol, we increased myocardial contractility by infusing isoproterenol at a fixed heart rate. Increasing heart rate above baseline levels caused no significant increase in cardiac output in the younger lambs (3.9 +/- 4.0%, mean +/- SD), and only small increases in the older lambs (11.4 +/- 6.7%). Decreasing heart rate, however, resulted in a progressive decrease in cardiac output in both groups of lambs. Decreasing afterload caused no significant increase in cardiac output in the younger lambs (1.4 +/- 14.0%) and only a small increase in the older lambs (11.1 +/- 1.9%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Circulatory adjustments to postnatal life.

Dramatic changes occur in the cardiovascular system at birth. The circulation changes from one characterized by the presence of central shunts, a relatively low combined ventricular output, right ventricular dominance, and pulmonary vasoconstriction, to a circulation in series with a high cardiac output equally divided between the two ventricles, and a greatly dilated pulmonary vascular bed. To understand the mechanisms that initiate these profound changes, studies that separate the components of the birth process in the chronically instrumented fetus must be continued, along with biochemical studies of isolated tissues to determine the cellular and subcellular events that mediate these changes. Understanding the many processes that control perinatal cardiovascular development will assist the physician in treating those infants in whom the transition from the fetal to the neonatal circulation is abnormal.

Animals↗
PubMed1987

Serum erythropoietin levels in patients with congenital heart disease.

Serum erythropoietin levels were measured by radioimmunoassay in 146 children and young adults with congenital heart disease to assess the relationship between erythropoietin and clinical factors (heart failure, anemia, cyanosis) and hemodynamic variables affecting oxygen delivery and utilization. Erythropoietin values were in the normal range (10 to 30 microU/mL) in 73% (58 of 80) of the patients with and 82% (54 of 66) of those without cyanosis. Elevated erythropoietin values in cyanotic patients were associated with lower mixed venous oxygen saturation and tension than in cyanotic patients with normal erythropoietin levels, even though the degree of polycythemia was similar. In contrast, most of the acyanotic patients who had elevated erythropoietin levels were anemic. Of the blood oxygen measurements, mixed venous oxygen saturation and tension had the closest inverse correlation with erythropoietin values. The normal erythropoietin values in most patients are in accord with other observations that show that an elevation in erythropoietin level in response to hypoxia will be transient if it results in a rise in hemoglobin concentration "appropriate" to the degree of hypoxia. Persistent elevation of erythropoietin in patients with congenital heart disease may indicate harmful impairment of hemoglobin production that is potentially correctable.

Adolescent↗
PubMed1987

The cardiovascular effects of isoflurane in lambs.

The effects of 1.0 and 1.5 minimum alveolar concentrations (MAC) of isoflurane on mean systemic arterial pressure, heart rate, stroke volume, cardiac output, total body oxygen consumption, myocardial oxygen consumption, and regional distribution of blood flow were studied in newborn lambs. Fractional extraction of oxygen for the total body and for the myocardium were calculated. MAC for isoflurane was first determined in eight lambs less than 10 days old. The mean value obtained was 1.51%. Six different lambs were used for cardiovascular study. Heart rate, stroke volume, cardiac output, and mean systemic arterial pressure decreased significantly during isoflurane anesthesia. Mean systemic arterial pressure and cardiac output decreased in a dose-dependent manner. Heart rate decreased significantly at 1.0 MAC isoflurane, but no further at 1.5 MAC. Stroke volume decreased only at 1.5 MAC. Cardiac output and total body oxygen consumption decreased by similar amounts at 1.0 MAC. Although cardiac output fell further at 1.5 MAC, oxygen consumption did not. Fractional extraction of oxygen increased only at 1.5 MAC. Myocardial blood flow and oxygen consumption decreased in parallel at 1.0 MAC, with no significant change during 1.5 MAC. Myocardial fractional oxygen extraction did not change. Although blood flow to all six body regions decreased significantly from control at both concentrations of isoflurane, blood flow to all organs except the adrenal did not differ significantly during 1.0 and 1.5 MAC. The authors conclude that a decrease in oxygen requirement during isoflurane anesthesia results in an appropriate decrease in oxygen delivery, with no apparent diversion of cardiac output from non-vital to vital organs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Effects of birth-related events on central blood flow patterns.

We determined the effects of three components of the birth process on central blood flow patterns in fetal sheep. We instrumented 16 fetal sheep at 133.0 +/- 1.2 days gestation, inserting various intravascular catheters, intubating the trachea, and placing an inflatable balloon around the umbilical cord. After 2-3 days, we determined central blood flow patterns using radionuclide-labeled microspheres under control conditions, during positive pressure ventilation without oxygenation, during ventilation with 100% O2, and after umbilical cord occlusion. The foramen ovale right to left shunt was essentially abolished, decreasing from 102 +/- 48 to 66 +/- 40 ml/min/kg with ventilation, and to only 13 +/- 10 ml/min/kg with oxygenation. The ductus arteriosus right to left shunt decreased progressively, from a control level of 224 +/- 64 to 6 +/- 10 ml/min/kg after umbilical cord occlusion. A ductus arteriosus left to right shunt appeared with oxygenation (41 +/- 26 ml/min/kg) and increased to 65 +/- 43 ml/min/kg after cord occlusion. Left ventricular output increased progressively as a percentage of combined ventricular output (from a control value of 34.8 to 59.5% after cord occlusion), and increased absolutely with ventilation (from 134 +/- 44 to 211 +/- 87 ml/min/kg). However, right ventricular output decreased (from a control value of 258 +/- 75 to 144 +/- 36 ml/min/kg after cord occlusion) so that combined ventricular output did not change. Although the transition from the fetal to neonatal circulatory pattern was accomplished by simulating these three components of the birth process, none is alone responsible for the large increase in combined ventricular output normally seen at birth.

Animals↗
PubMed1985

Recognition of fetal arrhythmias by echocardiography.

Fetal arrhythmias were detected in 33/198 high risk pregnancies from 21 weeks to term. Using the two-dimensional echocardiographic image of the fetal heart as a guide, the M-mode beam was directed to define the motion of the ventricular and atrial walls and atrioventricular valve or semilunar valves. Atrial contraction was defined either by the atrial wall motion or from the A-point of the atrioventricular valve. Ventricular contraction was defined by closure of the atrioventricular valve (C-point), the onset of ventricular wall contraction, or from the semilunar valve opening. Ladder diagrams of the sequence of atrial and ventricular activation were constructed to define the temporal sequence of these events. Premature atrial contractions were present in 12. In one fetus this arrhythmia converted into supraventricular tachycardia while in the other 11 fetuses the course was benign. Two fetuses had premature ventricular contractions. Supraventricular tachycardia was noted in five fetuses. One with hydrops at 29 weeks returned to sinus rhythm following maternal administration of procainamide. A second hydropic fetus with paroxysmal atrial tachycardia and hydrops failed to respond to digitalis, propranolol, procainamide, verapamil, or amiodarone, and died shortly after cesarean section. Two mature fetuses had tachycardia close to term and were treated after cesarean section. One fetus with runs of atrial tachycardia died in utero. Three fetuses had complete heart block, two of whom were from mothers with connective tissue diseases. In four fetuses, there was bradycardia of less than 100/minute lasting more than 30 seconds, but these episodes disappeared in 2 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Arrhythmias, Cardiac↗
PubMed1985

Developmental changes in myocardial contractile reserve in the lamb.

We have assessed serial changes in myocardial contractility and reserve in the normal lamb over the first month of life using an in vivo adaptation of the endsystolic pressure-volume relationship. Via a left thoracotomy, we insert a catheter tip pressure transducer into the left ventricle, affix an echo transducer onto the left ventricular epicardium, place an electromagnetic flow transducer around the pulmonary artery, and insert catheters for monitoring and infusions. We measure contractility by generating left ventricular wall stress-volume index (the cube of dimension) curves, at the same time increasing afterload by infusing phenylephrine. The slope of the endsystolic wall stress-volume index relationship is our index of contractility. Weekly studies were performed at rest and during isoproterenol infusion in 12 animals, and after propranolol administration in four. The data showed a progressive decrease in resting contractility but no change in maximal contractility during isoproterenol infusion over the 4 wk. Taking each week separately, the average increase in contractility during isoproterenol infusion was small at 1 wk (13%), moderate at 2 and 3 wk (24 and 26%, respectively), and large at 4 wk (79%). beta-Adrenergic blockade with propranolol caused a significant decrease in contractility in three of four animals studied at 1 wk, in only one of four animals at 2 wk, and in none of four animals at 3 or 4 wk. Thus, the newborn lamb shows a limited reserve in contractility that increases progressively with age; the limited reserve appears secondary to a high resting beta-adrenergic state.

Animals↗
PubMed1984

Comparison of M-mode echocardiographic measurement of right ventricular wall thickness obtained by the subcostal and parasternal approach in children.

Right ventricular (RV) wall thickness was measured from M-mode echocardiograms at end-diastole from both the parasternal and subcostal approaches in 50 children of various body surface areas (0.24 to 1.68 m2). The measurements were obtained from M-mode recordings generated from sector scans to ensure precise location and position. Twenty-three children had normal hearts, and 27 had various congenital heart defects that may be associated with RV hypertrophy. Corresponding measurements of the RV wall thickness at end-diastole from the 2 approaches were similar. Subcostal echocardiographic measurement of RV wall thickness was found to be a reliable alternative to parasternal measurement in children with normal hearts and in those with congenital heart disease and RV hypertrophy.

Cardiomegaly↗
PubMed1984

Two-dimensional echocardiographic determination of aortic and pulmonary artery sizes from infancy to adulthood in normal subjects.

The aorta, right pulmonary artery and pulmonary trunk were measured from the 2-dimensional echocardiogram (2-D echo) of 110 normal subjects aged 1 day to 18 years. The vessel diameters were measured from the parasternal short-axis view, the suprasternal long-axis view and the suprasternal short-axis view. Measurements were made at end-systole and at end-diastole and in both an axial and lateral direction where possible. When analyzed with respect to body surface area (BSA), the echocardiographic measurements were linearly related to the square root of the BSA, and there was inequality of variance around the relation. To establish a range of normal values for each vessel dimension, a weighted regression analysis was used to produce estimates of the regression line and a set of tolerance intervals. The systolic vessel dimension was larger than the diastolic vessel dimension and the measurement of a vessel in an axial direction was larger than the measurement of the same vessel in a lateral direction. In general, when a vessel was measured in several views, the largest diameter was obtained using the view that imaged the vessel in cross section. These data on normal values for the echocardiographic measurement of the aorta and pulmonary arteries at different BSAs should be useful for identifying patients with abnormalities in arterial size and for the serial assessment of arterial size in children who have undergone surgical or medical therapy.

Adolescent↗