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Biomedical subjects

L Weinert

Publications and source records attributed to L Weinert.

At least 37 records · Page 2Linked to original sources
PubMed1998

Use of color kinesis for evaluation of left ventricular filling in patients with dilated cardiomyopathy and mitral regurgitation.

OBJECTIVES: We tested the feasibility of using analysis of color kinesis images to objectively assess global and regional left ventricular (LV) diastolic function in patients with dilated cardiomyopathy (DCM). In addition, the ability of this technique to track drug-induced changes on LV diastolic properties was studied. BACKGROUND: Diastolic dysfunction contributes to symptomatology in patients with DCM. The assessment of LV diastolic function using conventional Doppler echocardiography is indirect and is confounded by multiple variables. Moreover, the noninvasive evaluation of regional diastolic properties is difficult. In contrast, color kinesis directly tracks and color-encodes regional diastolic endocardial motion. METHODS: We studied 24 patients with DCM and mitral regurgitation (MR) and 24 age-matched normal subjects. Transmitral and pulmonary vein flow velocities were measured using pulsed Doppler echocardiography. Diastolic color kinesis images were used to calculate indexes of magnitude and timing of global and regional diastolic function. Diastolic asynchrony was evaluated in different subgroups of patients with DCM. The effects of drug infusions (nitroprusside and dobutamine) were also studied. RESULTS: Color kinesis indexes of global diastolic function showed significant differences between patients with DCM and normal subjects. Compared with Doppler indexes, color kinesis was less confounded by MR and was capable of differentiating between drug-induced lusitropic and vasodilator effects. Diastolic asynchrony was increased in patients with DCM and severe MR. CONCLUSIONS: Quantitative analysis of global and regional LV diastolic function in patients with DCM using color kinesis is feasible.

Adult↗
PubMed1998

Age dependency of left atrial and left ventricular acoustic quantification waveforms for the evaluation of diastolic performance in left ventricular hypertrophy.

We evaluated diastolic performance in 50 normal subjects and 50 patients with concentric left ventricular (LV) hypertrophy. Age-dependent normal values were determined for LV and left atrial (LA) acoustic quantification parameters. Pulsed wave Doppler echocardiography was also performed on all subjects. Patients with LV hypertrophy had higher peak velocities of atrial contraction and atrial contributions to filling. The acoustic quantification waveforms revealed lower rapid filling percentage of total filling and lower peak rapid filling rates. The LA acoustic quantification analysis confirmed the dependence on active atrial emptying in the patients with LV hypertrophy. There were significant correlations with age for most of the LV and LA acoustic quantification parameters. Acoustic quantification provided confirmatory results in subjects with an abnormal relaxation or restrictive Doppler pattern. In subjects with a normal Doppler pattern, the acoustic quantification was of added diagnostic value, identifying abnormalities in 77% to 80% of the patients.

Adult↗
PubMed1997

Segmental analysis of color kinesis images: new method for quantification of the magnitude and timing of endocardial motion during left ventricular systole and diastole.

BACKGROUND: We describe a method for objective assessment of left ventricular (LV) endocardial wall motion based on Color Kinesis, a new echocardiographic technique that color-encodes pixel transitions between blood and myocardial tissue. METHODS AND RESULTS: We developed a software that analyzes Color Kinesis images and provides quantitative indices of magnitude and timing of regional endocardial motion. Images obtained in 12 normal subjects were used to evaluate the variability in each index. Esmolol, dobutamine, and atropine were used to track variations in LV function in 14 subjects. Objective evaluation of wall motion was tested in 20 patients undergoing dobutamine stress testing. Regional fractional area change, displacement, and radial shortening were displayed as histograms and time curves. Global function was assessed by calculating magnitude and timing of peak ejection or filling rates and mean time of ejection or filling. Patterns of endocardial motion were consistent between normal subjects. Fractional area change and peak ejection rate decreased with esmolol and increased with dobutamine. Time to peak ejection and mean time of contraction were prolonged with esmolol and shortened with dobutamine. Using atropine, we proved that our findings with dobutamine were not secondary to its chronotropic effects. Dobutamine induced regional wall motion abnormalities in 10 patients in 38 segments diagnosed conventionally. Segmental analysis detected abnormalities in 36 of these 38 segments and in an additional 5 of 322 segments. CONCLUSIONS: Analysis of Color Kinesis images allows fast, objective, and automated evaluation of regional wall motion sensitively enough to evaluate clinical dobutamine stress data. This method has significant potential in the diagnosis of myocardial ischemia.

Adrenergic beta-Agonists↗
PubMed1997

Contractile reserve in patients with peripartum cardiomyopathy and recovered left ventricular function.

OBJECTIVES: Peripartum cardiomyopathy is a rare complication of pregnancy. Thirty percent of patients with this disorder are reported to recover baseline ventricular function within 6 months of delivery, but the ability of these ventricles to respond to hemodynamic stress is unknown. The aim of this investigation was to quantitatively assess the contractile reserve of patients with a history of peripartum cardiomyopathy and recovered left ventricular function. STUDY DESIGN: Baseline left ventricular contractility was assessed by use of the load and heart rate-independent relationship between end-systolic stress and rate-corrected velocity of fiber shortening. Data were acquired from "recovered" patients (10.5 +/- 11.6 months after delivery) and compared with data from matched nonpregnant controls with use of two-dimensionally targeted M-mode echocardiography and calibrated subclavian pulse tracings that were recorded over a wide range of afterloads (end-systolic stress) generated by methoxamine (1 mg/min) infusion. Contractile reserve was assessed by a dobutamine challenge (5 micrograms/kg/min) and quantified as the vertical deviation of the dobutamine end-systolic stress minus the corrected velocity of fiber shortening data point from the baseline contractility line. RESULTS: Patients with peripartum cardiomyopathy and matched controls had normal baseline heart rates, blood pressures, ventricular dimensions, and left ventricular function. Contractile reserve, however, was reduced in patients with recovered peripartum cardiomyopathy (0.30 +/- 0.12 vs 0.17 +/- 0.04 circ/sec, p < 0.03). CONCLUSIONS: Women with a history of peripartum cardiomyopathy who have regained normal resting left ventricular size and performance have decreased contractile reserve revealed by the use of a dobutamine challenge test. Ventricles of these women may respond suboptimally to hemodynamic stress in spite of evidence of recovery by routine echocardiographic evaluation.

Adrenergic beta-Agonists↗
PubMed1997

Doppler echocardiographic reference values for healthy rhesus monkeys under ketamine hydrochloride sedation.

Cardiac ultrasound is a noninvasive technique that is commonly used to serially evaluate cardiac structure and function. Recent advances in Doppler-Echocardiography enable the ultrasonographer to perform a sophisticated noninvasive assessment of cardiovascular physiology. The Rhesus monkey is a frequently used non-human primate animal model of human cardiovascular disease because this species closely models human anatomy and physiology. However, while this species is frequently used in cardiovascular research, standardized echocardiographic values generated from large numbers of normal Rhesus are not available. In the present study, we performed cardiac ultrasound imaging on 28 healthy Rhesus monkeys to obtain normal reference values of cardiovascular structure and function in this species. Nomograms were generated from these data by plotting parameters of cardiovascular geometry and function with body weight. These normal reference data were compared to previously reported values obtained from prior studies that used noninvasive, invasive, and morphometric techniques.

Anesthetics, Dissociative↗
PubMed1996

Echocardiographic quantification of regional left ventricular wall motion with color kinesis.

BACKGROUND: Color kinesis is a new technology for the echocardiographic assessment of left ventricular wall motion based on acoustic quantification. This technique automatically detects endocardial motion in real time by using integrated backscatter data to identify pixel transitions from blood to tissue during systole on a frame-by-frame basis. In this study, we evaluated the feasibility and accuracy of quantitative segmental analysis of color kinesis images to provide objective evaluation of regional systolic endocardial motion. METHODS AND RESULTS: Two-dimensional echocardiograms were obtained in the short-axis and apical four-chamber views in 20 normal subjects and 40 patients with regional wall motion abnormalities. End-systolic color overlays superimposed on the gray scale images were obtained with color kinesis to color encode left ventricular endocardial motion throughout systole on a frame-by-frame basis. These color-encoded images were divided into segments by use of custom software. In each segment, pixels of different colors were counted and displayed as stacked histograms reflecting the magnitude and timing of regional endocardial excursion. In normal subjects, histograms were found to be highly consistent and reproducible. The patterns of contraction obtained in normal subjects were used as a reference for the objective automated interpretation of regional wall motion abnormalities, defined as deviations from this pattern. The variability in the echocardiographic interpretation of wall motion between two experienced readers was similar to the diagnostic variability between the consensus of the two readers and the automated interpretation. CONCLUSIONS: Color kinesis is a promising new tool that may be used clinically to improve the qualitative and quantitative evaluation of spatial and temporal aspects of global and regional wall motion. In this initial study, segmental analysis of color kinesis images provided accurate, automated, and quantitative diagnosis of regional wall motion abnormalities.

Adult↗
PubMed1996

Feasibility of aortic diameter measurement by multiplane transesophageal echocardiography for preoperative selection and preparation of homograft aortic valves.

BACKGROUND: Preoperative knowledge of the aortic annular diameter could enable the preoperative selection and preparation of an appropriately sized homograft aortic valve. OBJECTIVE: The aims of this study were to prospectively determine whether the combined use of transthoracic and multiplane transesophageal echocardiography allows accurate preoperative aortic annular measurements for the selection and preparation of adequately sized homograft aortic valves and to retrospectively evaluate the influence of the echocardiographic approach (transthoracic vs transesophageal) and the reader's level of experience on the accuracy of these measurements. METHODS: Aortic annular measurements were performed before the operation by an experienced reader who used a combination of transthoracic and multiplane transesophageal images of 25 patients (mean age 52 +/- 13 years) referred for homograft aortic valve replacement. Measurements were also performed retrospectively by three additional readers with different levels of training in echocardiography. These readers acquired aortic annular diameters from prerecorded tapes and obtained measurements from each echocardiographic modality independently. All values were compared with the surgical measurement obtained with a ring valve sizer. RESULTS: With the combined echocardiographic approach, excellent agreement was found between preoperative echocardiographic and surgical measurements (mean difference +/- 2 standard deviations = 0.2 +/- 1.4 mm). All echocardiographic data were found to be within 2 mm of the surgical measurement. These measurements were used to select and prepare the aortic homograft valve before insertion. The accuracy of annular measurements appeared to increase in parallel to the level of experience. The aortic annular measurements obtained retrospectively by a second experienced reader were more accurate with the use of transesophageal than with transthoracic echocardiography (p < 0.01). In contrast, the echocardiographic modality had no influence on the accuracy of measurements of less experienced readers (p > 0.2). CONCLUSIONS: Preoperative measurement of the aortic annular diameter by transthoracic and multiplane transesophageal echocardiography is accurate and clinically feasible. Preoperative knowledge of the aortic annular diameter may be used to select and prepare the aortic homograft, improving valve availability and reducing ischemic time.

Adult↗
PubMed1994

Noninvasive method for determination of arterial compliance using Doppler echocardiography and subclavian pulse tracings. Validation and clinical application of a physiological model of the circulation.

BACKGROUND: The Poiseuillian model of the arterial system currently applied in clinical physiology does not explain how arterial pressure is maintained during diastole after cessation of pulsatile aortic inflow. Arterial pressure-flow relations can be more accurately described by models that incorporate arterial viscoelastic properties such as arterial compliance. Continuous pressure and flow measurements are needed to evaluate these properties. Since the techniques used to date to acquire such data have been invasive, physiological models of the circulation that incorporate these properties have not been widely applied in the clinical setting. The purpose of this study was (1) to validate noninvasive methods for continuous measurement of central arterial pressure and flow and (2) to determine normal reference values for arterial compliance using physiological models of the circulation applied to the noninvasively acquired pressure and flow data. METHODS AND RESULTS: Simultaneously acquired invasive and noninvasive aortic pressures (30 patients), flows (8 patients), and arterial mechanical properties (8 patients) were compared. Pressure was measured by high-fidelity catheter aortic micromanometer (invasive) and calibrated subclavian pulse tracing (noninvasive). Aortic inflow was determined from thermodilution-calibrated electromagnetic flow velocity data (invasive) and echo-Doppler data (noninvasive). Arterial compliance was determined for two- and three-element windkessel models of the circulation using the area method and an iterative procedure, respectively. Once validated, the noninvasive methodology was used to determine normal compliance values for a reference population of 70 subjects (age range, 20 to 81 years) with normal 24-hour ambulatory blood pressures and without Doppler-echocardiographic evidence for structural heart disease. The limits of agreement between invasive and noninvasive pressure data, compared at 10% intervals during ejection and nonejection, were narrow over a wide range of pressures, with no significant differences between methods. Invasive and noninvasive instantaneous aortic inflow values differed slightly but significantly at the start of ejection (P < .05), but during the latter 90% of ejection, values for the two methods were similar, with narrow limits of agreement. Total vascular resistance and arterial compliance values derived from invasive and noninvasive data were similar. Arterial compliance values for the normal population using the two-element model (C2E) ranged from 0.74 to 2.44 cm3/mm Hg (mean, 1.57 +/- 0.38 cm3/mm Hg), with a beat-to-beat variability of 5.2 +/- 3.9%. C2E decreased with increasing age (r = -.73, P < .001) and tended to be higher in men (1.67 +/- 0.41 cm3/mm Hg) than in women (1.51 +/- 0.35 cm3/mm Hg, P = .07). Compliance values for the three-element model (C3E) were predictably smaller than for the two-element model (mean, 1.23 +/- 0.30; range, 0.59 to 2.16 cm3/mm Hg, P < .001 versus C2E) but correlated with C2E values (r = .81, P < .001) and were also inversely related to age (r = -.56, P < .001). Ridge regression and principal component analyses both showed the compliance value to be a composite function whose variation could be best predicted by consideration of simultaneous values for five major hemodynamic determinants: heart rate, mean flow, mean aortic pressure, minimal diastolic pressure, and end-systolic pressure. Multivariate analysis revealed age and sex to be independent predictors of compliance (P < .01 for both). There were no differences in compliance between black and white subjects. CONCLUSIONS: Noninvasive methods can be used to acquire the hemodynamic data necessary for clinical application of physiological models of the circulation that incorporate arterial viscoelastic properties such as arterial compliance. The strong inverse linear relation between model-based compliance estimates and age mandates incorporation of this demographic parameter in

Adolescent↗
PubMed1993

Peripartum heart failure associated with prolonged tocolytic therapy.

beta-Adrenergic receptor agonist tocolysis has been reported to cause noncardiogenic pulmonary edema. We report an association between chronic terbutaline therapy and cardiomyopathy in peripartum women. Among 15 gravidas who had peripartum heart failure, 4 had received prolonged terbutaline tocolysis. Although those four patients had completely normalized ventricular function, only 7 of the 11 others recovered. We suggest that gravidas receiving long-term beta-sympathomimetic tocolysis undergo close evaluation of cardiac function.

Cardiomyopathies↗
PubMed1991

Venous air embolism. Diagnosis by spontaneous right-sided contrast echocardiography.

This report describes the definitive diagnosis of venous air-embolism by documentation of spontaneous echo contrast in the right cardiac chambers following removal of a jugular venous catheter in a patient with hepatic failure. This complication was potentiated by the presence of concurrent hepatic coagulopathy which prejudiced effective hemostasis at the central venous puncture site.

Catheterization, Central Venous↗
PubMed1991

Prediction of aortic annulus diameter by two-dimensional echocardiography. Application in the preoperative selection and preparation of homograft aortic valves.

The preoperative selection and preparation of an appropriately sized homograft aortic valve would allow delay of surgery if a suitable valve were unavailable, thus pre-emptying inventory limitations, and a decrease of ischemic time in cases of isolated aortic valve replacement. An accurate preoperative measurement of the aortic annulus diameter is the prerequisite for such selection. The aortic annulus diameter was measured retrospectively in a blinded fashion from the two-dimensional echocardiograms of 62 patients who underwent aortic valve replacement with mechanical or bioprosthetic valves. Measurements were obtained with electronic calipers by two observers. Confidence in the accuracy of the measurement obtained was ranked on a scale from 1 to 5. The mean difference between echocardiographic measurements and prosthetic valve sizes was 0.39 +/- 0.46 mm (mean +/- 2SD) for observer 1 and -0.26 +/- 1.44 mm for observer 2. Ninety-eight percent of observer 1 measurements and 80% of observer 2 measurements were within 1.5 mm of the prosthetic valve size (p less than 0.01 for differences between observers). Confidence scores were higher for observer 1 and for both observers were related to accuracy. The aortic annulus diameter of eight patients scheduled for homograft aortic valve replacement was measured prospectively with the same technique. There was an excellent agreement between the two-dimensional echocardiographic measurements and the surgical measurements. In the last 5 consecutive patients, the echocardiographic measurement was used for the preoperative selection and preparation of the appropriate valve. In conclusion, measurement of the aortic annulus diameter by two-dimensional echocardiography is feasible and clinically useful for the preoperative selection and preparation of homograft aortic valves.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Valve↗
PubMed1990

Pericardial window: mechanisms of efficacy.

Although the term implies a persistent communication through which fluid might drain, how a pericardial window works is not clear. We believe that the mechanism of success is not window but rather fusion of the epicardium to the pericardium with obliteration of the potential space. To evaluate this, we studied 28 patients, all of whom underwent a subxiphoid pericardial window procedure with tube drainage maintained until output was minimal. There were no operative deaths, and 26 patients (92.9%) obtained permanent relief. Postoperative echocardiograms demonstrated thickening of the pericardium/epicardium and obliteration of the pericardial space. Autopsy performed on 4 patients who died of their underlying malignancy confirmed this fusion, which begins as an inflammatory process. A subxiphoid pericardial window relieves effusions with a low operative mortality and good long-term success (92.9%, 26 of 28). This success is dependent on the inflammatory fusion of the epicardium to pericardium and not maintenance of a window. Tube decompression should be maintained until fluid output is minimal to allow apposition and fusion of the two surfaces.

Adult↗
PubMed1988

Role of the beta 2 adrenoceptor in mediating positive inotropic activity in the failing heart and its relation to the hemodynamic actions of dopexamine hydrochloride.

In patients with severe congestive heart failure, it has been suggested that since myocardial beta 1 adrenoceptors are selectively down-regulated, activation of beta 2 receptors may be a preferable approach to augmenting contractility. Accordingly, dopexamine hydrochloride (1, 2 and 4 micrograms/kg/min) and dopamine (2 and 4 micrograms/kg/min) were administered to 8 patients with dilated cardiomyopathy. Left ventricular (LV) dimensions, thicknesses and pressures were obtained using simultaneous high-fidelity pressure measurements and echocardiographic recordings. LV contractility was assessed using the load-independent relation between LV end-systolic wall stress and rate-corrected velocity of fiber shortening. Cardiac index increased in a dose-related manner with both drugs, and was accompanied by a decline in systemic vascular resistance, a measure of peripheral arteriolar tone. LV end-diastolic pressure was unaltered except for a decrease from 29 +/- 6 to 19 +/- 5 mm Hg (p less than 0.017) at the highest dose of dopexamine hydrochloride. Heart rate was unchanged during the infusion of dopamine but increased significantly with dopexamine hydrochloride. LV end-systolic wall stress, a measure of LV internal load, decreased with both drugs. With dopamine, a dose-dependent positive inotropic effect was observed. Dopexamine hydrochloride, at the 4 micrograms/kg/min infusion dose, exerted a mild positive inotropic effect comparable to that noted with dopamine at 2 micrograms/kg/min. Thus, dopamine and dopexamine hydrochloride improved overall LV performance. With dopamine, a substantial positive inotropic effect occurred in association with a reduction in LV afterload. The increased cardiac index observed with dopexamine hydrochloride was due primarily to peripheral vasodilatation and a positive chronotropic effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1979

Determination of right atrial and right ventricular size by two-dimensional echocardiography.

No data are available on determining right atrial and right ventricular size by two-dimensional echocardiography. We performed two-dimensional echocardiograms on eight human right-heart casts obtained at autopsy and on 50 patients who underwent complete left- and right-heart catheterization. Measurement of individual dimensions of the long and short axes of the right atrium and ventricle from right heart casts closely correlated with the volume of these structures as determined by water displacement. Further, individual dimensions by cross-sectional echo correlated well with actual casts dimensions. Subsequently, echocardiographic measurements of right atrial and ventricular long and short axes were obtained in the apical four-chambered view in a group of normals and compared with a group of patients with right ventricular volume overload states. Mean values for right atrial short-axis and long-axis measurements were greater in right ventricular volume overload patients than in normals: 6.5 +/- 0.3 vs 3.6 +/- 0.1 cm, and 6.0 +/- 0.3 vs 4.2 +/- 0.1 cm, respectively (both p less than 0.001). In addition, measurements of both individual dimensions as well as planed area of the right ventricle were greater in right ventricular volume overload patients than in normals: maximal short axis 6.1 +/- 0.3 vs 3.5 +/- 0.2 cm, mid-short axis 6.1 %/- 0.4 vs 2.8 +/- 0.2 cm, and area 40 +/- 2.6 vs 18 +/- 1.2 cm2 (all p less than 0.001). There were no differences in right ventricular long-axis measurement. Two-dimensional echocardiography provided better separation of normals from right ventricular volume overload patients than did M-mode techniques. Thus, two-dimensional echocardiography, with the apical four-chambered view, enables accurate visualization of the right atrium and ventricle in almost all patients. Futher, measurements of right atrial and right ventricular size by two-dimensional echocardiography readily distinguish normal patients from those with right ventricular volume overload.

Adolescent↗