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M W Dae

Publications and source records attributed to M W Dae.

52 records · Page 3Linked to original sources
PubMed1990

Comparison of transesophageal echocardiographic and scintigraphic estimates of left ventricular end-diastolic volume index and ejection fraction in patients following coronary artery bypass grafting.

Transesophageal echocardiography (TEE) has become a commonly used monitor of left ventricular (LV) function and filling during cardiac surgery. Its use is based on the assumption that changes in LV short-axis ID reflect changes in LV volume. To study the ability of TEE to estimate LV volume and ejection immediately following CABG, 10 patients were studied using blood pool scintigraphy, TEE, and thermodilution cardiac output (CO). A single TEE short-axis cross-sectional image of the LV at the midpapillary muscle level was used for area analysis. Between 1 and 5 h postoperatively, simultaneous data sets (scintigraphy, TEE, and CO) were obtained three to five times in each patient. End-diastolic (EDa) and end-systolic (ESa) areas were measured by light pen. Ejection fraction area (EFa) was calculated (EFa = (EDa - ESa)/EDa). When EFa was compared with EF by scintigraphy, correlation was good (r = 0.82 SEE = 0.07). EDa was taken as an indicator of LV volume and compared with LVEDVI which was derived from EF by scintigraphy and CO. Correlation between EDa and LVEDVI was fair (r = 0.74 SEE = 3.75). The authors conclude that immediately following CABG, a single cross-sectional TEE image provides a reasonable estimate of EF but not LVEDVI.

Adult↗
PubMed1990

Imaging of the heart using metaiodobenzylguanidine.

Catecholamines have profound influences on cardiac function. Mechanisms relating abnormalities in sympathetic innervation to myocardial dysfunction are poorly understood, however. Recent studies have demonstrated the feasibility of noninvasively imaging the sympathetic nerves of the heart using radiolabeled MIBG. This article examines some of the experimental evidence to support the neuronal localization of MIBG. In addition, the early clinical experience is reviewed.

3-Iodobenzylguanidine↗
PubMed1989

Usefulness and limitations of regional cardiac sympathectomy by phenol.

We evaluated the completeness and extent of regional sympathetic denervation of the left ventricle after epicardial painting with phenol in anesthetized dogs. In a region encircled by phenol, the effect of electrical stimulation of efferent sympathetic fibers on myocardial contractility and coronary vascular resistance was completely abolished within 30 min. Denervation extended to untreated regions innervated by sympathetic fibers crossing the phenol line. For at least 4 h after phenol application, intravenous infusion of isoproterenol or coronary arterial infusion of tyramine increased myocardial contractility in the denervated region; norepinephrine content and neurotransmitter uptake were normal, indicating that nerve terminals, postjunctional receptors, and myocardium remained functional. However, after 3-14 days, tissue catecholamine content and transmitter uptake in the encircled area were markedly reduced. The results suggest that careful evaluation is necessary in selecting a fully innervated control region in studies employing regional sympathetic denervation with phenol.

Administration, Topical↗
PubMed1989

Scintigraphic assessment of regional cardiac adrenergic innervation.

To assess the feasibility of noninvasively imaging the regional distribution of myocardial sympathetic innervation, we evaluated the distribution of sympathetic nerve endings, using 123I metaiodobenzylguanidine (MIBG), and compared this with the distribution of myocardial perfusion, using 201Tl. Twenty dogs were studied: 11 after regional denervation, and nine as controls. Regional denervation was done by left stellate ganglion removal, right stellate ganglion removal, and application of phenol to the epicardial surface. Computer-processed functional maps displayed the relative distribution of MIBG and thallium in multiple projections in vivo and excised heart slices in all animals. In six animals, dual isotope emission computed tomograms were acquired in vivo. Tissue samples taken from innervated and denervated regions of the MIBG images were analyzed for norepinephrine content to validate image findings. Normal controls showed homogeneous and parallel distributions of MIBG and thallium in the major left ventricular mass. In the left stellectomized hearts, MIBG was reduced relative to thallium in the posterior left ventricle; whereas in right stellectomized hearts, reduced MIBG was in the anterior left ventricle. Phenol-painted hearts showed a broad area of decreased MIBG extending beyond the area of phenol application. In both stellectomized and phenol-painted hearts, thallium distribution remained homogeneous and normal. Norepinephrine content was greater in regions showing normal MIBG (550 +/- 223 ng/g) compared with regions showing reduced MIBG (39 +/- 44 ng/g) (p less than 0.001), confirming regional denervation. Combined MIBG-thallium functional maps display the regional distribution of sympathetic innervation. This new ability to noninvasively map the distribution of sympathetic nerves with simultaneous comparison to regional perfusion may provide important new insights into mechanisms, whereby an imbalance in sympathetic activity may relate to clinical disorders.

3-Iodobenzylguanidine↗
PubMed1989

Blood pool scintigraphy.

Scintigraphic techniques offer a variety of computer aided analytic methods for the assessment of ventricular size and function. They are objective, quantitative, and reproducible, and contribute to the clinical evaluation of all forms of cardiac disease. In some cases complementary to other methods, the scintigraphic assessment of ventricular function is often unique in the valuable clinical data which they supply.

Cardiac Output↗
PubMed1988

Analysis of thallium-201 "washout" from parametric color coded images.

We developed a parametric washout image which color codes regional washout, and blindly compared enhanced perfusion images in multiple projections with regional washout graphs and images in 25 patients. Washout images permitted true spatial and anatomic assessment of regions viewed en face as well as those seen in tangent, making possible the exclusion of non-coronary irregularities and permitting evaluation of washout over the apparent cavity. "Cavitary" washout was abnormal in 10 of 12 patients with apparent cavitary dilation on the post stress image, but in none without this finding. The distribution and rotation of washout abnormalities seen over the cavity when viewed en face, and the long delay between the termination of stress and post-exercise image acquisition, suggest that apparent cavitary dilation is often related to improved visibility of the 201T1 deficient blood pool due to relative ischemia of the overlying myocardial wall.

Color↗
PubMed1987

Effects of activity on ascending aortic velocity in children with valvar aortic stenosis.

The peak velocity of aortic blood flow was measured in 12 normal children and 20 children with valvar aortic stenosis (AS) by continuous-wave Doppler ultrasound (CWD). Measurements were made at rest, after 2 forms of exercise and, in the 11 children who underwent cardiac catheterization, while under sedation. The exercise was both formal cycle ergometry and a 200-meter jog. The peak velocity in normal children was 1.5 +/- 0.2 m/s at rest, increasing to 2.1 +/- 0.4 m/s (p less than 0.01) after running and to 1.9 +/- 0.4 m/s (p less than 0.01) after cycling. Peak velocity in children with AS was 3.5 +/- 0.8 m/s at rest, increasing to 4.4 +/- 0.8 m/s (p less than 0.01) after running and to 4.5 +/- 0.5 m/s (p less than 0.01) after cycling. The increase in peak velocity was greater in children with AS than in normal children. Measurements of left ventricular (LV) aortic pressure differences by cardiac catheterization were compared to those made by CWD, using the modified Bernoulli equation. The best correlation of the CWD prediction of LV aortic pressure differences was achieved when the children were sedated. The peak velocity of blood flow in the ascending aorta varied with level of activity, and this variability must be considered when using the Bernoulli equation to predict LV aortic pressure differences. CWD prediction of the LV aortic pressure difference was best when the child was sedated (r = 0.98). It is therefore prudent to consider the velocity measurement proximal to the AS to calculate LV aortic pressure differences more accurately unless the child is sedated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Undrained bloody pericardial effusion in the early postoperative period after coronary bypass surgery: a prospective blood pool study.

To assess the clinical importance of hemopericardium after cardiac surgery, serial blood pool scintigrams were performed in 13 random patients throughout the initial hours after coronary artery bypass graft surgery. Scintigraphic measurements of pericardial fluid accumulation and left ventricular ejection fraction were made. Hemodynamics, cardiac, output, and chest tube drainage were monitored; and symptoms of postpericardiotomy syndrome were recorded for a mean of 7.4 months after surgery. Seven of the 13 patients had no scintigraphic evidence of bloody pericardial effusion. Six patients had scintigraphic evidence of bloody pericardial effusion; three of these effusions were small, localized posteriorly, and evident throughout the study. In two other patients large collections of fluid (over 100 ml) developed. In one of these patients increased mediastinal drainage required reoperation. The other patient remained stable although mediastinal drainage decreased. The sixth patient showed a moderate effusion (95 ml) that decreased without evident effusion or drainage when the last image was taken. Two patients (one with evidence of a postoperative bloody effusion), had symptoms of postpericardiotomy syndrome in the follow-up period. This study reports the generally benign occurrence of bloody postoperative mediastinal effusions, the frequent accumulation of substantial amounts of undrained sanguineous fluid, and the lack of connection between the presence and or amount of pericardial blood and the postpericardiotomy syndrome. The importance of these scintigraphic findings can be interpreted only with knowledge of associated mediastinal drainage.

Aged↗
PubMed1983

Phasic blood flow patterns in the superior and inferior venae cavae and umbilical vein of fetal sheep.

Measurements of phasic blood flow in the inferior and superior venae cavae and umbilical vein of fetal sheep (gestational age, 121 to 140 days) were made with chronically implanted electromagnetic flow transducers. In the venae cavae blood flow was inversely related to phasic changes in venous and/or intrathoracic pressure. During fetal apnea a forward surge of flow occurred during ventricular systole (systolic surge) and ventricular diastole (diastolic surge). Slower fetal heart rates were associated with a more prominent diastolic surge. Reductions in afterload caused by acetylcholine administration augmented the peak diastolic venous flow. In contrast, increased afterload caused by hypoxia and norepinephrine administration was associated with increased peak systolic flow. During regular fetal breathing movements the phasic flow pattern was determined largely by the respiratory cycle with the effect of the cardiac cycle superimposed. There was minimal venous pulsation in the intra-abdominal umbilical vein, compared with that of the intrathoracic venae cavae of the apneic fetus. Our findings demonstrate that fetal systemic vascular resistance profoundly influences right atrioventricular filling patterns.

Acetylcholine↗
PubMed1982

A new technique for perfusion fixation and contrast enhancement of foetal lamb myocardium for electron microscopy.

A technique of perfusion fixation following elective diastolic cardiac arrest was developed to obtain excellent preservation of foetal lamb hearts for morphological studies with electron microscopy. A technique was developed to markedly enhance the contrast of embedded material by treating thin sections with tannic acid prior to lead staining. This technique has been particularly useful for quantitative morphometric analysis.

Animals↗
PubMedDate not supplied

Imaging of myocardial sympathetic innervation with metaiodobenzylguanidine.

The sympathetic nervous system has profound influences on myocardial function and pathophysiology. The heart is densely innervated with sympathetic nerves, which are distributed on a regional basis. Heterogeneity of myocardial sympathetic innervation, or autonomic imbalance, has long been hypothesized as a major mechanism underlying sudden cardiac death. Only in the past few years has it been possible to evaluate abnormalities in heart innervation in the intact animal. Recent developments in cardiac imaging have lead to the ability to map the distribution of the sympathetic nerves in vivo, with radiolabeled metaiodobenzylguanidine. As a result, pathophysiologic mechanisms that relate alterations in sympathetic nerve activity to disease processes are now being explored.

3-Iodobenzylguanidine↗
PubMedDate not supplied

Fast acquisition of myocardial SPECT images with Tc-99m sestamibi for the diagnosis of coronary artery disease.

BACKGROUND: Shortening the acquisition time for myocardial single-photon emission computed tomographic (SPECT) imaging increases patient comfort and laboratory throughput. The purpose of this study was to compare the diagnostic accuracy for coronary artery disease detection of myocardial SPECT images acquired in 5 to 10 minutes versus 25 minutes using Tc-99m methoxyisobutylisonitrile (Tc-99m sestamibi) and a single-head gamma camera. METHODS AND RESULTS: Forty-one subjects had a standard 1-day rest/stress Tc-99m sestamibi myocardial SPECT study. Two sets of rest and stress images were acquired on the same day for each subject. One set of images was acquired with a 5- to 10-minute fast acquisition protocol; the second set of images was acquired with a 25-minute standard protocol. The accuracies of the fast and standard protocols for identifying individuals with and without coronary artery disease were equivalent. Accuracy was 76% for the fast protocol and 73% for the standard protocol in individuals with at least one coronary stenosis > or = 70%. The accuracies of the two protocols for identifying individual coronary arteries with stenoses > or = 70% also were equivalent. Accuracy was 77% for the fast protocol and 74% for the standard protocol. CONCLUSIONS: SPECT myocardial images may be acquired in as little as 5 to 10 minutes using Tc-99m sestamibi and a 1-day rest/stress protocol. Accuracy is equivalent to that attained in studies with longer imaging times.

Aged↗
PubMedDate not supplied

Potential added value of three-dimensional reconstruction and display of single photon emission computed tomographic gated blood pool images.

BACKGROUND: Single photon emission computed tomographic (SPECT) acquisition provides potential advantages for blood pool imaging. However, the method has been little applied. METHODS: An improved method of three-dimensional (3-D) reconstruction and display of SPECT equilibrium blood pool scintigrams and related phase data was developed. Dynamic slices and volume-rendered dynamic 3-D images were displayed. Images were viewed from each of 34 solid angles referenced to a sphere surrounding the reconstruction field. Each image pixel was "painted" with intensity-coded regional amplitude and color-coded for its phase angle. The method was applied to evaluate the cardiac anatomy, regional contraction, and related conduction sequence at rest in 17 patients. Twelve had normal left ventricular function including 7 patients with minimal septal preexcitation. Five patients had abnormal left ventricular function, including 2 with left bundle branch block. RESULTS: Slices contained all of the functional information, but necessary data integration was time-consuming and evaluation of chamber size and anatomy was difficult. Three-dimensional projection images condensed and integrated the data, presenting new vantage points on anatomy, contraction, and conduction not otherwise available in the clinically limited angulations of planar images. This provided excellent visual separation of cardiac chambers with full and increased visualization of right and left ventricular wall motion in all segments compared with the conventional projections acquired clinically (p < 0.05). Atria and great vessels were well separated with evident size and function. Phase-angle progression paralleled the electrocardiogram, permitting bypass pathway localization and the direct noninvasive localization of posteroseptal pathways. CONCLUSIONS: The 3-D method permits greater access to and utilization of SPECT blood pool image data. It suggests specific advantages for clinical use.

Adult↗