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Biomedical subjects

R Rokey

Publications and source records attributed to R Rokey.

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

Physiologic observations of pregnant women undergoing prophylactic erythrocytapheresis for sickle cell disease.

Five women in the second or early third trimester of pregnancy underwent prophylactic partial red cell exchange by automated erythrocytapheresis for sickle cell disease. The purpose of this pilot study was to characterize the hematologic, hemodynamic, and metabolic changes associated with this procedure. Pretransfusion hematocrit increased 49 percent by 3 to 5 days after the transfusion. Paired observations indicate a 14-percent drop in maternal oxygen consumption. There was a slight tendency for reduced posttransfusion cardiac output that resulted primarily from changes in maternal heart rate and not from changes in stroke volume. Left ventricular contractility also tended to decrease after transfusion. Neither fetal bradycardia nor alteration in the umbilical circulation by Doppler ultrasound was observed during the transfusion procedures. Despite substantial hematologic alterations, this procedure is associated with small or negligible changes in maternal hemodynamic and metabolic function for minimally symptomatic pregnant patients with sickle cell disease.

Anemia, Sickle Cell↗
PubMed1991

Resolution of ventricular tachycardia and endocardial tuberculoma following antituberculosis therapy.

A 23-year-old woman presented with sustained ventricular tachycardia and was found to have an endocardial mass by echocardiography and by magnetic resonance imaging. The diagnosis of cardiac endocardial tuberculoma was made, and she was treated with antituberculous therapy and an antiarrhythmic drug for one year. After a year, the mass was no longer present, and with all antiarrhythmic medications stopped, ventricular tachycardia could no longer be induced by electrophysiologic study. There has been no clinical recurrence.

Adult↗
PubMed1990

Return of atrial mechanical function following electrical conversion of atrial dysrhythmias.

The return of atrial mechanical function and its relationship to embolic events following cardioversion of atrial arrhythmias is controversial. Fourteen patients with atrial arrhythmias were evaluated with pulsed Doppler echocardiography before and after direct current (DC) cardioversion. The atrial filling fraction increased significantly: 1.14 +/- 4.3% at baseline versus 14.9 +/- 13.3%, 13.4 +/- 11.4%, and 21.9 +/- 13.5% at 5 minutes, 30 minutes, and 24 hours, respectively, following cardioversion. Absent atrial mechanical activity was noted in four patients immediately after cardioversion. Mechanical activity resumed by 30 minutes in one patient and at 24 hours in two others. Those with delayed atrial function had lower stroke volumes and atrial filling fractions following cardioversion. An embolic event occurred in one patient who had immediate return of atrial mechanical activity. This patient also had the largest atrial filling fraction of any patient at 24 hours (41%). These data suggest that the degree of atrial mechanical activity following cardioversion is variable and that embolic episodes are not necessarily related to delayed return of atrial mechanical activity following cardioversion.

Adult↗
PubMed1990

Nuclear magnetic resonance imaging of the pulmonary arteries, subpulmonary region, and aorticopulmonary shunts: a comparative study with two-dimensional echocardiography and angiography.

Twelve patients more than 8 years of age with complex congenital heart disease were evaluated prospectively with nuclear magnetic resonance (NMR) imaging and with echocardiographic and angiographic imaging techniques. The subpulmonary region, main pulmonary artery, right and left pulmonary arteries, and aorticopulmonary shunts were clearly visualized by means of NMR imaging in all patients. Angiography defined the subpulmonary region and main pulmonary artery in all patients, the right and left pulmonary arteries along their length in 11 of 12 patients, and aorticopulmonary shunts in seven of eight patients. Except for the right pulmonary artery, echocardiography defined the remaining structures in less than or equal to 50% of patients. Measurement of the pulmonary artery diameters on NMR images correlated well with the angiographic measurements of both the left (r = 0.96) and right (r = 0.94) pulmonary arteries. These results suggest that NMR imaging may be the preferable noninvasive imaging technique for defining the anatomy of the subpulmonary region, main and left pulmonary arteries, and aorticopulmonary shunts in older patients with congenital cardiovascular disease and that it compares well with the angiographic standard.

Adolescent↗
PubMed1990

Cor triatriatum dexter: antemortem diagnosis in an adult by cross sectional echocardiography.

Cor triatriatum dexter is a rare cardiac abnormality in which the right atrium is subdivided into two distinct chambers. This anomaly is generally attributed to the persistence of the right sinus venosus valve and it is frequently associated with severe malformations of other right heart structures. The antemortem diagnosis of the membrane may be difficult and its presence is often only established at necropsy. In a woman of 56 with Ebstein's anomaly the echocardiographic features of cor triatriatum dexter were examined before and during cardiac catheterisation. These investigations showed the position of the membrane, that there was no gradient between the two atrial chambers, and that there were perforations in the centre of the membrane.

Cor Triatriatum↗
PubMed1989

Usefulness of nuclear magnetic resonance imaging for evaluation of pericardial effusions, and comparison with two-dimensional echocardiography.

Nuclear magnetic resonance (NMR) imaging clearly delineates cardiovascular structures without interference from overlying bone and lung tissue. The techniques of NMR imaging and echocardiography were compared in 26 patients with pericardial effusions, 10 of whom had associated pleural effusions. In those patients with fluid detected by both techniques, estimated size of the effusion tended to be somewhat larger by NMR. NMR imaging detected several small pericardial effusions that were not visualized by echocardiography. Both techniques demonstrated loculation well, although NMR imaging was better for detecting fluid located superiorly at the aortic pericardial reflection site, medially at the border of the right atrium and posteriorly at the left ventricular apex. In the 14 patients with documented exudative effusions (10 pericardial, 4 pleural) NMR signals of varying intensity were present in the effusion. One patient had a documented transudative effusion and no NMR signal was observed in the fluid. NMR imaging clearly distinguished pericardial from pleural effusions. NMR imaging is indicated when a suspected pericardial effusions is not detected by echocardiography or when specific localization or fluid characterization is desired.

Adolescent↗
PubMed1989

Nuclear magnetic resonance imaging of acute myocardial infarction within 24 hours of chest pain onset.

The present study was intended to establish the feasibility, safety and usefulness of conventional spin-echo nuclear magnetic resonance (NMR) imaging for the detection of acute myocardial infarction within 24 hours of the onset of chest pain. Monitoring facilities were established in the NMR imaging suite that provided the same level of reliability and safety found in a standard coronary care unit. An imaging protocol was developed that allowed the acquisition of a complete study in 30 minutes while providing useful information about mechanical function and myocardial tissue contrast. Eighteen postthrombolysis patients were imaged within 21 +/- 2 hours of chest pain onset. No patient developed recurrent chest pain or arrhythmias in the NMR imaging suite. Relatively T2-weighted spin-echo images (echo time = 60 ms; repetition time = heart rate) provided interpretable images in 16 patients. Fourteen normal subjects were imaged for comparison. Thirteen of 16 patients had an increase in signal intensity in the region of the infarction. Regional wall thickening was assessed using a floating endocardial centroid technique. Wall motion abnormalities detected by NMR corresponded to those noted by 2-dimensional echocardiography and contrast angiography. Sensitivity, specificity and accuracy for the detection of infarction were 93, 80 and 87%, respectively, when signal intensity and wall thickening abnormalities were combined. In summary, NMR imaging is feasible in patients with acute myocardial infarction within 24 hours of chest pain onset. The study can be conducted safely and it provides useful information about acute myocardial infarction.

Adult↗
PubMed1989

Maternal hemodynamic effects of uterine contractions by M-mode and pulsed-Doppler echocardiography.

Nineteen normotensive term gravid women were studied by M-mode and pulsed-Doppler echocardiography to noninvasively evaluate the hemodynamic consequences of uterine contractions on maternal left ventricular function. These laboring subjects were placed in the left lateral decubitus position with epidural labor anesthesia. Ejection fraction was not affected by firm contractions, although a small increase in left ventricular end-diastolic measurements was noted. There was a tendency for maternal heart rate to decrease (-5%); however, this trend was not statistically significant. A 16% increase in left ventricular stroke volume (75 +/- 15 to 89 +/- 17 ml) (p less than 0.001) was associated with an overall 11% augmentation of maternal cardiac output (6.31 +/- 1.79 to 7.12 +/- 1.93 L/min) (p less than 0.001). These findings support the hypothesis that uterine contractions increase maternal stroke volume through autotransfusion of uteroplacental blood and cardiac preload augmentation during normal labor.

Cardiac Output↗
PubMed1989

Assessment of myocardial systolic wall thickening using nuclear magnetic resonance imaging.

A quantitative nuclear magnetic resonance (NMR) imaging method of evaluating regional left ventricular function was compared with histochemical evidence of infarction in dogs and functional measurements in patients. Short-axis images of the heart were obtained at end-diastole and at 100 ms intervals thereafter. Regional diastolic left ventricular wall thickness and maximal percent systolic wall thickening were measured at the level of the papillary muscles in each of six segments. In six normal dogs, the mean end-diastolic wall thickness was 9 +/- 1.6 mm, and the mean maximal percent thickening was 61 +/- 11%. In eight dogs with a 4 day old infarct, maximal percent thickening was 5 +/- 8% (p less than 0.001) in the infarcted segments. In 10 normal human volunteers, the mean end-diastolic wall thickness was 10.1 +/- 1 mm, and the mean maximal percent systolic wall thickening was 60 +/- 18%. Reduced maximal percent systolic wall thickening was defined as a value greater than or equal to 2 SD below the mean value obtained in normal volunteers. Seven patients with regional wall motion abnormalities were independently assessed by NMR imaging and biplane ventriculography. With a sensitivity of 94% and a specificity of 80%, NMR imaging demonstrated reduced maximal percent systolic wall thickening in the same segments identified as akinetic or dyskinetic by biplane ventriculography. Thus, abnormalities of regional systolic wall thickening are accurately identified with this quantitative imaging technique.

Adult↗
PubMed1989

Assessment of tissue iron overload by nuclear magnetic resonance imaging.

PURPOSE: The ability of stored intracellular iron to enhance magnetic susceptibility forms the basis by which tissue iron can be detected by nuclear magnetic resonance (NMR) imaging. We used this technique to assess myocardial, spleen, and liver iron content in patients with known or suspected iron overload disorders. PATIENTS AND METHODS: Spin echo NMR images were obtained in 30 patients; 20 had chronic anemias treated by multiple blood transfusions, five had idiopathic hemochromatosis, and five had non-hemochromatotic liver disease with elevated serum ferritin levels and no stainable iron on liver biopsy. The acquisition of oblique images through the short axis of the left ventricle permitted assessment of left ventricular function, while demonstrating the liver and spleen on the same image. Iron content was assessed using a signal intensity ratio of organ (spleen, liver, or myocardium) to skeletal muscle. RESULTS: In patients with multiple blood transfusions, iron content was highest in liver, followed by the spleen. Significant iron overload was detected in the myocardium of only one patient. Left ventricular systolic wall thickening was normal in patients receiving multiple blood transfusions. Two patients with treated idiopathic hemochromatosis had normal signal intensity ratios, and three untreated patients had evidence of significant deposits of iron in the liver and spleen as indicated by a reduction in signal intensity ratios (0.2 +/- 0.01 and 0.9 +/- 0.01, respectively). Five patients with non-hemochromatotic liver disease and high serum ferritin levels had normal signal intensity ratios by NMR imaging. CONCLUSION: NMR imaging is a useful method of detecting tissue iron and distinguishing disease due to iron overload. Myocardial iron deposition is a late event, occurring after accumulation of iron in the spleen and liver.

Adult↗
PubMed1988

Monitoring of acutely ill patients during nuclear magnetic resonance imaging: use of a time-varying filter electrocardiographic gating device to reduce gradient artifacts.

A time-varying filter electrocardiographic gating device designed to reduce NMR-induced gradient artifacts during NMR imaging of the acutely ill cardiac patient is described. When used in conjunction with multiple electrocardiographic display monitors, accurate assessment of the electrocardiogram for morphologic changes and arrhythmias during all phases of the NMR examination is possible.

Electrocardiography↗
PubMed1988

Serial changes in nuclear magnetic resonance relaxation times after myocardial infarction in the rabbit: relationship to water content, severity of ischemia, and histopathology over a six-month period.

To determine the serial changes in T1 and T2 relaxation times of myocardial infarction, and their relationship to observed changes in water content, regional myocardial blood flow, and histopathology, rabbits were studied at 14 time intervals ranging from 30 min to 6 months after coronary artery ligation. All values were compared to a control group. Hearts were subdivided into infarct and normal segments for measurement of blood flow, water content, and relaxation times (20-MHz spectrometer); other hearts were excised intact for histopathologic studies. T1 relaxation time of infarcted myocardium did not change significantly compared to control over the 6-month study period. T2 relaxation time increased (P less than 0.0001) at 3 days and returned to baseline by 2 months. Consonant with the increase in T2 of infarct, nuclear magnetic resonance (NMR) images at 3 days demonstrated an increase in signal intensity of infarct compared to surrounding normal myocardium. At 6 months, marked myocardial thinning was observed without changes in signal intensity. Changes in T2 of infarcted myocardium were not related to changes in water content or severity of ischemia, but correlated best with infarct healing and scar formation as detected on histopathology. In conclusion, the findings of this study indicate that T2 relaxation time of the infarcted myocardium increases markedly at 3 days and remains elevated for 2 months. These changes correlate best with the onset and progression of infarct healing. These data demonstrate the potential of T2-weighted NMR imaging for assessing healing patterns following ischemic myocardial injury.

Animals↗
PubMed1988

Noninvasive maternal stroke volume and cardiac output determinations by pulsed Doppler echocardiography.

Sixteen obstetric patients with pulmonary artery catheters were studied by two-dimensional and pulsed Doppler echocardiography to compare prospectively pulsed Doppler-and thermodilution-derived estimations of left ventricular stroke volume and cardiac output. Systolic aortic flow velocity waveforms were obtained by pulsed Doppler ultrasound from the apical five-chamber echocardiographic window. Aortic diameters were obtained by two-dimensional echocardiography from the left parasternal long axis view. The mean (+/- SEM) aortic diameter averaged 2.1 +/- 0.1 cm, with a mean calculated aortic valve area of 3.6 +/- 0.2 cm2. The mean aortic flow velocity integral was 21.8 +/- 0.8 cm. This information was used to calculate aortic stroke volume and cardiac output. Thermodilution- and Doppler-derived estimations for maternal stroke volume (r = 0.86) and cardiac output (r = 0.94) were significantly correlated when aortic diameter measurements based on a leading vessel edge method were used. Our findings verify the accuracy of an important noninvasive technique for quantitating maternal stroke volume and cardiac output by pulsed Doppler echocardiography. This methodology should provide an alternative approach to invasive monitoring in the study of normal and abnormal maternal circulatory hemodynamics.

Aorta↗
PubMed1988

Electrocardiographic gating and monitoring in NMR imaging.

ECG gating and monitoring during NMR imaging may be achieved reliably by applying the principles in this tutorial. In order to use the ECG signal both for triggering and for patient monitoring it must have a prominent R-wave, while at the same time must have little artifact from gradient switches or the Lorentz voltage across the aorta, and not be significantly distorted by gradient switching artifacts. The twin goals of no image artifacts and minimal ECG artifacts may be achieved by the following means: (1) using ECG electrodes with minimal metal, (2) selecting electrodes and cables with no ferrous metals, (3) placing the limb electrodes close together, (4) placing the line between the limb electrodes and the leg electrode parallel to the magnetic flux lines and, if possible, parallel to the transverse component of the gradient flux lines, (5) keeping the area between the limb electrodes and the leg electrode small, (6) placing that area in the center of the imager and (7) twisting or braiding the cables. Following these principles allows artifact-free images and reliable ECG monitoring during ECG-gated NMR imaging examinations.

Electrocardiography↗