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Biomedical subjects

F A Flachskampf

Publications and source records attributed to F A Flachskampf.

At least 73 records · Page 4Linked to original sources
PubMed1995

Occurrence of transcranial Doppler high-intensity transient signals in patients with potential cardiac sources of embolism. A prospective study.

BACKGROUND AND PURPOSE: Cerebral emboli can be recognized by typical "high-intensity transient signals" (HITS) in the transcranial Doppler (TCD) spectral curves. Patients with potential cardiac sources of embolism are at higher risk for stroke. METHODS: We examined the frequency of HITS in the left middle cerebral artery (MCA) with TCD over periods of 30 minutes in 100 patients having potential cardiac sources of embolism, as indicated by transthoracic or transesophageal echocardiography. RESULTS: Thirty-six (36%) of the patients presented with HITS. Sex, age, sufficient anticoagulation level, antiplatelet therapy, neurological symptoms, and a history of thrombosis had no influence on the prevalence and number of HITS. The patients with a single echocardiographic diagnosis were separated into eight echocardiographically defined groups: patients with (1) atrial fibrillation, (2) coronary artery disease plus ejection fraction of more than 30% including at least three wall segments of hypokinesia/akinesia, (3) coronary artery disease with less than 30% ejection fraction, (4) dilated cardiomyopathy, (5) infectious endocarditis, (6) aortic stenosis, (7) mitral stenosis, and (8) patent foramen ovale. A significant difference in HITS occurrence could not be found in any of the defined groups. Only patients with infectious endocarditis showed a tendency for a higher HITS prevalence. CONCLUSIONS: HITS are common phenomena in patients with potential cardiac sources of embolism. The clinical relevance of these HITS remains unclear.

Adolescent↗
PubMed1995

[Three-dimensional reconstruction of heart valves].

The reconstruction of three-dimensional data sets from two-dimensional echocardiographic images offers several fundamental advantages: 1. more complete data than present in the few standard 2D-view; 2. off-line generation of any desired plane, cut, or perspective after the data set has been acquired; 3. access to quantitative parameters like surface areas (e.g., of valve leaflets or portions of leaflets), volumes, and others, without geometric assumptions. The mitral valve has been the focus of several studies using various techniques of reconstruction of transthoracic or transesophageal images. These studies have shown the mitral annulus to be a non-planar, "saddle-shaped" structure, with an average distance of highest to lowest points of 14 mm in normals. This recognition of mitral annular non-planarity has led to a more stringent echocardiographic definition of mitral valve prolapse. Further studies have shown systolic shrinkage of mitral annular area by about 30% and systolic apico-basal translation of the annulus by approximately 1 cm in normals. In patients with dilated cardiomyopathy, the annulus is flattened, and both cyclic change in annular area and apico-basal translation are significantly reduced. 3D-studies of the left ventricular outflow tract in hypertrophic obstructive cardiomyopathy allow measurement of outflow tract and leaflet surface areas and dynamic spatial visualization of systolic anterior motion of the anterior mitral leaflet. Automated techniques to reconstruct the full grey value data set from a high number of parallel or rotational transesophageal planes allow impressive visualization of normal and diseased mitral and aortic valves or valve prostheses, with special emphasis on generating "surgical" views and perspectives, which cannot be obtained by conventional tomographic imaging.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Valve↗
PubMed1995

[3-dimensional reconstruction of multiplanar transesophageal echocardiography images: a methodologic report with case examples].

First experience with the dynamic three-dimensional reconstruction of transesophageal echocardiographic images in more than 100 patients with various cardiac diseases are reported. Ninety different two-dimensional image planes were acquired for each reconstruction using a conventional multiplanar transducer, connected to a stepper motor and controlled by a computer-based image acquisition system with special software. Acquisition time for one data set was 2.3 +/- 0.9 min, and calculation time to achieve three-dimensional images was 20-45 min. Several cardiac structures were reconstructed and analyzed qualitatively and quantitatively (measurements of distances and areas, volume calculation by Simpson's rule). Image sequences showing three-dimensional depth by gray scale modification were generated. After image acquisition one can select any desired cut plane to achieve perspectives that cannot be obtained by two-dimensional technique. Advantages of three-dimensional echocardiography are the display and potential quantification of pathomorphology of the left ventricle and mitral valve, atrial septal defects, intracardiac masses (i.e., myxomas, vegetations), and direct spatial imaging of complex congenital heart diseases. In principle, three-dimensional data sets have advantages for the quantitative evaluation of irregular formed cardiac structures, since the three-dimensional data set is more complete than cross-sections used in conventional two-dimensional echocardiography. Currently, however, these advantages are limited by the necessity of human interaction to segment the structures of interest.

Adolescent↗
PubMed1995

[Improved evaluation of prosthetic heart valve regurgitation with multiplanar transesophageal echocardiography].

UNLABELLED: To study the value of the newly introduced multiplane transesophageal transducer technology for the assessment of prosthetic valve regurgitation, 63 consecutive patients with 35 mitral and 33 aortic prostheses (23 bioprostheses and 45 mechanical prostheses) were examined. Transvalvular, paravalvular, and, in mechanical valves, normal or pathological transvalvular regurgitation were identified using first 0 degrees (transverse) and 90 degrees (longitudinal) planes combined with flexion of the echoscope tip and then additionally using multiple intermediary planes by transducer rotation. In a subgroup of 20 patients interobserver variability was evaluated. Both methods showed regurgitation in 56/58 valves; one additional case of regurgitation was seen by multiplane imaging only. However, there were 19 cases of regurgitation not clearly classifiable by biplane technique compared to only three using multiplane technique. Grading of severity was concordant by both modalities in 66 and discordant in only two cases. Observers disagreed on severity in 2/20 cases based on biplane imaging, but in none based on multiplane imaging; classification of regurgitation differed in 6/20 biplane and 1/20 multiplane images respectively. CONCLUSION: Multiplane transesophageal imaging improves classification of prosthetic regurgitation, but has little effect on severity grading.

Adult↗
PubMed1995

Three-dimensional reconstruction of cardiac structures from transesophageal echocardiography.

Although tomographic imaging has been very successful in cardiology,the quantitation of volumes, surfaces, and masses,as well as understanding of complex morphologies would improve by three-dimensional imaging. This review focuses on approaches to 3-D reconstruction from transesophageal echocardiography. In the past, several attempts using either stepwise parallel translation or stepwise rotation of the transducer have been made. In vitro and, to a limited extent, in vivo studies have confirmed high accuracy in calculating left ventricular volumes in such manner. Complex cardiac structures and their motion, such as the mitral annulus, mitral leaflets, atrial septal defects, and others have been reconstructed from patient studies. Although potentially a powerful tool for cardiac imaging with promising quantitation capabilities, progress is needed in particular in the field of border detection to make 3-D imaging practical enough for clinical use.

Computer Graphics↗
PubMed1994

Comparison of transcranial contrast Doppler sonography and transesophageal contrast echocardiography for the detection of patent foramen ovale in young stroke patients.

The prevalence of a patent foramen ovale was assessed by simultaneously performing transesophageal contrast echocardiography and transcranial contrast Doppler sonography (TCD) in 137 subjects (mean age 36 years) with stroke of unclarified etiology (n = 41), clarified etiology (n = 33), and in normal subjects (n = 63; mean age 32 years). Patent foramen ovale was found significantly more often in patients with unclarified than clarified strokes or in normal subjects (66% vs 33%, or 43%). Massive paradoxical embolism through a patent foramen ovale, identified by TCD, occurred significantly (p < 0.01) more often in patients with unclarified (64%) than clarified (27%) strokes or in normal subjects (3%). However, minimal shunts were typical in normal subjects (79%). Patent foramen ovale was detected indirectly by TCD when calculated on the basis of transesophageal contrast echocardiographic findings (sensitivity 89%, specificity 92%). Thus, TCD reliably detects paradoxical cerebral embolism through a patent foramen ovale, and provides important additional information for evaluating its clinical relevance by semi-quantification of embolic contrast material.

Adult↗
PubMed1994

Relationship of aortic regurgitant velocity slope and pressure half-time to severity of aortic regurgitation under changing haemodynamic conditions.

The slope and pressure half-time of the aortic regurgitant velocity spectrum have been used as non-invasive markers of regurgitant severity. Recent in vitro and theoretical work, however, has suggested a confounding effect of systemic vascular resistance and left ventricular compliance on these parameters. To study this situation in vivo, we have investigated the determinants of the aortic regurgitant velocity profile in an animal model of aortic regurgitation in which the regurgitation was induced surgically and in which the afterload was varied pharmacologically. Specifically, we examined the relationship of slope and pressure half-time of the aortic regurgitant velocity profile to the severity of aortic regurgitation under varying conditions of afterload using multilinear analysis. Slope varied directly with regurgitant orifice area and inversely with systemic vascular resistance and both left ventricular and aortic compliance (all P < 0.001). Pressure half-time related to these variables in the opposite direction. When the regurgitant orifice was variable in size, slope related directly (P < 0.001) and half-time inversely to the severity of the aortic regurgitation (the clinically expected response). In contrast, when the regurgitant orifice area was constant, slope varied inversely (P < 0.001) and half-time varied directly (P < 0.07) with the severity of the aortic regurgitation. Following nitroprusside infusion, slope tended to increase (P = 0.08) and pressure half-time tended to shorten (P = 0.08) despite a significant reduction in the regurgitant fraction (P = 0.009). Similarly, following dopamine infusion, a significant increase in regurgitant fraction (P = 0.01) was associated with a slight fall in aortic regurgitation slope and a lengthening of the half-time.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Transoesophageal pacing echocardiography for detection of restenosis after percutaneous transluminal coronary angioplasty.

Non-invasive documentation of restenosis after successful percutaneous transluminal coronary angioplasty (PTCA) remains a problem. Thus, transoesophageal pacing echocardiography (TPE) with simultaneous rapid atrial pacing via the same probe, a recently validated method for detection of coronary artery disease, was used in 60 patients for detection of restenosis after successful PTCA (54 patients with one and six patients with multivessel PTCA). The patients came for routine follow-up angiography 5.4 +/- 3.7 months after PTCA regardless of clinical status. Restenosis (diameter stenosis > or = 50%) was demonstrated in 22 patients. Disease progression in previously normal vessels was noted in three additional patients. Results for detection of restenosis and disease progression were compared to exercise ECG and in 40 patients to Tc-99m methoxy-isobutyl-isonitrile (MIBI)-radionuclide perfusion imaging. Diagnostic standard exercise ECG could be performed in only 38 patients, due to peripheral vascular disease, joint disease or premature exhaustion in the rest of patients. TPE was non-diagnostic in two patients due to ineffective pacing or patient discomfort. Sensitivity of TPE for detection of restenosis and disease progression after PTCA was 84% compared with 50% and 86% for exercise ECG and Tc-99m MIBI-SPECT (P < 0.03 and ns), respectively. Specificity of TPE (85%) was also higher than that of exercise ECG (59%, P < 0.03) and comparable to the specificity of MIBI-SPECT (84%). Overall accuracy of TPE was far superior to exercise ECG and similar to MIBI-SPECT (84% vs 54% and 85%) (P = 0.0007 and ns, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1994

Altered left ventricular diastolic function post-atrial pacing in coronary artery disease and left ventricular hypertrophy: further insights by pulmonary venous flow analysis.

Left ventricular filling dynamics during acute pacing-induced myocardial ischaemia were assessed using transoesophageal atrial pacing and simultaneous Doppler measurements of pulmonary venous and mitral flow. All patients (10 with CAD and 12 with left ventricular hypertrophy due to hypertrophic cardiomyopathy; HCM) were in sinus rhythm and patients with mitral insufficiency were excluded. Data were compared with those of a control group (n = 10). Measurements were obtained at baseline (heart rate 84 +/- 14 beats.min-1) and immediately after atrial pacing via the same transoesophageal echocardiography (TEE) probe after stepwise increase of the pacing rate to 133 +/- 12 beats.min-1. Heart rate immediately after pacing was 83 +/- 13 beats.min-1. Time velocity integrals (TVI) were calculated at baseline and after pacing for the following flows: early (E) and late (A) mitral flows, as well as antegrade systolic (S), diastolic (D) and retrograde diastolic (R) pulmonary venous flows. In the control group none of the flow parameters changed significantly after pacing compared with baseline data. In contrast, in CAD patients, the TVI of the E wave, the TVI E/A ratio as well as the pulmonary venous flow changed significantly after pacing (7.3 to 5.5 cm, P < 0.05, 1.7 to 1.1, P < 0.01 and 1.0 to 2.1 cm, P < 0.001, respectively). HCM patients also showed significant changes: TVI E/A ratio post-pacing decreased from 1.9 to 1.4 (P < 0.05), and the pulmonary venous reverse flow integral increased from 1.3 to 2.8 cm (P < 0.0001). Analysis of variance showed the TVI E/A ratio to be significantly dependent on pacing (P = 0.012). The pulmonary venous retrograde flow was found to be influenced by the presence of disease (P = 0.033 before and P = 0.0001 after pacing) and in all cases by pacing (before vs after pacing; P = 0.0001). Pacing resulted in significantly different changes in the TVI E/A ratio and the TVI of the retrograde pulmonary venous flow for CAD and HCM patients compared with those of control subjects. In patients with CAD and HCM, rapid atrial pacing results in a decreased early to late ventricular filling ratio because of impaired relaxation, despite presumably increased filling pressure. Retrograde pulmonary venous flow increased because of increased filling pressure and operating left ventricular stiffness.

Adult↗
PubMed1993

Comparative evaluation of bicycle and dobutamine stress echocardiography with perfusion scintigraphy and bicycle electrocardiogram for identification of coronary artery disease.

In 66 patients with suspected coronary artery disease (CAD), exercise electrocardiography (ECG), exercise echocardiography, dobutamine stress echocardiography (dosage, 5 to 40 micrograms/kg/min), single-photon emission computed tomography (SPECT) using methoxy-isobutyl-isonitrile (MIBI) and coronary angiography were performed prospectively to compare methods for detecting CAD. CAD was defined as 70% luminal area stenosis in at least 1 coronary artery at coronary angiography. Significant CAD was present in 50 patients. Compared with exercise ECG, exercise echocardiography, dobutamine stress echocardiography and MIBI-SPECT had a significantly higher sensitivity (52% vs 80, 79 and 89%; p < 0.01, p < 0.01 and p < 0.001, respectively). There were no significant differences in sensitivity between exercise echocardiography, dobutamine stress echocardiography and MIBI-SPECT. Specificity of MIBI-SPECT was lowest (71%), whereas exercise ECG, exercise and dobutamine echocardiography had higher specificities (93, 87 and 81%, respectively). Significance, however, was not achieved. Differences in overall accuracy between exercise echocardiography (82%), dobutamine stress echocardiography (80%) and MIBI-SPECT (85%) were not significant. Comparison with accuracy of exercise ECG (62%) was significant (p < 0.05, p < 0.05 and p < 0.01, respectively). In 1-vessel disease, exercise ECG had a lower sensitivity (45%) than exercise and dobutamine echocardiography and MIBI-SPECT (79, 78 and 84%; p < 0.02, p < 0.02 and p < 0.01, respectively). Regarding the 24 patients with false-negative exercise ECG results, 67% had positive exercise echocardiography findings, 71% positive dobutamine echocardiography results and 84% positive technetium-99m MIBI-SPECT results.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Planimetry of orifice area in aortic stenosis using multiplane transesophageal echocardiography.

OBJECTIVES: The purpose of this study was to investigate whether the orifice area in aortic stenosis can be determined accurately and reliably by multiplane transesophageal echocardiography. BACKGROUND: Monoplane transesophageal echocardiography has been used for planimetry of aortic valve orifice areas; however, obtaining a precise short-axis view is sometimes impossible. METHODS: In 41 consecutive patients with known valvular calcific aortic stenosis (20 men, mean age 64 +/- 9 years), aortic valve orifice area was measured by planimetry using a multiplane transesophageal echocardiographic probe that allows full rotation of the cross-sectional plane. Results were compared with invasive measurements obtained by the Gorlin formula and areas determined noninvasively by transthoracic echocardiography using the continuity equation. RESULTS: Multiplane transducer technology enabled the rotation of the cross-sectional plane from an exactly aligned long-axis view of the stenosed valve to a precise short-axis view without moving the tip of the echocardiographic probe, thus achieving an orifice cross section at a level predetermined in the long-axis view. Planimetry was feasible in 38 patients (93%). In three patients with pinhole stenosis (area determined by the Gorlin formula < 0.4 cm2), the valve area could not be exactly delineated. Correlation between areas derived by transesophageal echocardiographic planimetry (0.56 +/- 0.31 cm2) and by the Gorlin formula (0.58 +/- 0.31 cm2) was excellent (r = 0.95; standard deviation of regression [SDR] = 0.054; Y = 0.92X + 0.085, where Y = Gorlin area and X = planimetry area). Correlation between Gorlin- and continuity equation-derived areas (0.65 +/- 0.46 cm2) was r = 0.79; for continuity equation- and transesophageal planimetry-derived areas it was r = 0.83. Severe aortic stenosis (valve area < or = 0.75 cm2) was predicted with high sensitivity (96%) and specificity (88%). CONCLUSIONS: Multiplane transesophageal echocardiography is a practical and accurate clinical tool for the assessment of the severity of aortic stenosis.

Aged↗
PubMed1993

Transesophageal echocardiography for prosthetic valve evaluation: is it always necessary?

Transesophageal echocardiography provides excellent images of mitral and aortic prostheses, due to its higher resolution and less interference from other cardiac structures. Since the introduction of transesophageal echocardiography, it has proved to be valuable for the evaluation of prosthetic heart valves. "Classic" indications include the evaluation of prosthetic valve endocarditis, the search for paravalvular abscesses, and the assessment of regurgitation in mechanical, especially mitral, prostheses. New technical developments such as biplane or multiplane transducers enhance the diagnostic capabilities of the technique. Transesophageal echocardiography can also have advantages in recognizing obstructive lesions such as thrombi or pannus, and help understand the complex morphology of prostheses in grafts. Transesophageal echocardiography should be considered a backup technique whenever transthoracic echocardiography, which always remains the primary approach, is inconclusive or negative in the presence of clinically suspected prosthetic valve malfunction.

Aortic Valve↗
PubMed1993

[New procedures in transesophageal echocardiography: multiplane transesophageal echocardiography and transesophageal stress echocardiography].

Multiplane transesophageal echocardiography is a new development in transducer technology, which allows by rotation of the transducer to obtain not only transverse and longitudinal planes but also all intermediate planes. Exterior control allows continuous rotation of the scanning plane from the conventional transverse plane, corresponding to 0 degree, to the longitudinal plane, corresponding to 90 degrees and further to a left-right inverted transverse plane, corresponding to 180 degrees. Although the echoscope tip, which houses the rotatable transducer, is slightly larger than conventional probes, in our clinical experience of well over 400 cases, intubation of the esophagus is not more difficult than with the mono- or biplane probe. In comparison with the biplane technique the adjustment of intermediate planes is easier and less unpleasant for the patient, since mechanical irritation due to sideward flexion of the probe is less often necessary. Plane rotation, effected by control buttons in the echoscope handle, takes eight seconds from 0 degree to 180 degrees. The probe incorporates a 5 MHz phased array transducer, which alternatively works at 3.7 MHz. Pulsed, continuous and color Doppler are also integrated. Multiplane transesophageal echocardiography was used to investigate several clinical questions. In 41 patients with aortic valve stenosis the valve area was determined by planimetry. The valve area was measured in an individually aligned short axis view (between 50 degrees and 70 degrees). A high correlation (r = 0.95; Y = 0.9 X + 0.1; p < 0.01) with invasively determined valve areas by the Gorlin formula was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Isovolumic relaxation time varies predictably with its time constant and aortic and left atrial pressures: implications for the noninvasive evaluation of ventricular relaxation.

The isovolumic relaxation time (IVRT) is an important noninvasive index of left ventricular diastolic function. Despite its widespread use, however, the IVRT has not been related analytically to invasive parameters of ventricular function. Establishing such a relationship would make the IVRT more useful by itself and perhaps allow it to be combined more precisely with other noninvasive parameters of ventricular filling. The purpose of this study was to validate such a quantitative relationship. Assuming isovolumic relaxation to be a monoexponential decay of ventricular pressure (pv) to a zero-pressure asymptote, it was postulated that the time interval from aortic valve closure (when pv = p(o)) until mitral valve opening (when pv = left atrial pressure, pA) would be given analytically by IVRT = tau[log(p(o))-log(pA)], where tau is the time constant of isovolumic relaxation and log is to the base e. To test this hypothesis we analyzed data from six canine experiments in which ventricular preload and afterload were controlled nonpharmacologically. In addition, tau was adjusted with the use of beta-adrenergic blockade and calcium infusion, as well as with hypothermia. In each experiment data were collected before and after the surgical formation of mitral stenosis, performed to permit the study of a wide range of left atrial pressures. High-fidelity left atrial, left ventricular, and aortic root pressures were digitized, the IVRT was measured from the aortic dicrotic notch until the left atrioventricular pressure crossover point, and tau was calculated by nonlinear least-squares regression.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Calculation of atrioventricular compliance from the mitral flow profile: analytic and in vitro study.

The quantitative assessment of ventricular diastolic function is an important goal of Doppler echocardiography. Hydrodynamic analysis predicts that the net compliance (Cn) of the left atrium and ventricle can be quantitatively predicted from the deceleration rate (dv/dt) of the mitral velocity profile by the simple expression: Cn = - A/rho dv/dt, where A is effective mitral valve area and rho is blood density. This formula was validated using an in vitro model of transmitral filling where mitral valve area ranged from 0.5 to 2.5 cm2 and net compliance from 0.012 to 0.023 cm3/(dynes/cm2) (15 to 30 cm3/mm Hg). In 34 experiments in which compliance was held constant throughout the filling period, net atrioventricular compliance was accurately calculated from the E wave downslope and mitral valve area (r = 0.95, p less than 0.0001). In a second group of experiments, chamber compliance was allowed to vary as a function of chamber pressure. When net compliance decreased during diastole (as when the ventricle moved to a steeper portion of its pressure-volume curve), the transorifice velocity profile was concave downward, whereas when net compliance increased, the velocity profile was concave upward. Application of the preceding formula to these curved profiles allowed instantaneous compliance to be calculated throughout the filling period (r = 0.93, p less than 0.001). Numeric application of a mathematic model of mitral filling demonstrated the accuracy of this approach in both restrictive and nonrestrictive orifices.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Function↗
PubMed1992

Transoesophageal stress echocardiography for pre-operative detection of patients at risk of intra-operative myocardial ischaemia.

Patients with coronary artery disease have an increased risk of developing intra-operative myocardial ischaemia and peri-operative myocardial infarction. Pre-operative identification of patients at risk of developing peri-operative myocardial ischaemia is often difficult or even impossible due to the inability of the patient to perform an exercise test. For those unable to perform physical exercise a system has recently been described combining transoesophageal echocardiography with simultaneous transoesophageal atrial pacing via the same probe to detect pacing-induced wall motion abnormalities, a sign of coronary artery disease. In a prospective study, 20 patients with clinically suspected coronary artery disease undergoing hip replacement were examined pre-operatively by transoesophageal stress echocardiography. During the subsequent operation the incidence of intra-operative ischaemia was evaluated again in all 20 patients by transoesophageal echocardiography. In eight of the 20 patients (40%) wall motion abnormalities could be induced by transoesophageal stress echocardiography pre-operatively. Intra-operative wall motion abnormalities occurred in six of these eight patients. In two patients with wall motion abnormalities induced by transoesophageal stress echocardiography no abnormalities occurred during surgery. However, in those in whom wall motion abnormalities did occur during operation they occurred in the same left ventricular segment as those initiated by stress echocardiography. None of the patients without pre-operatively inducible wall motion abnormality developed them during surgery. No patient developed a myocardial infarction intra- or post-operatively. Thus, preoperative transoesophageal stress echocardiography is a valuable technique for the detection of patients who may develop ischaemic wall motion abnormalities during surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗