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Biomedical subjects

U Sechtem

Publications and source records attributed to U Sechtem.

143 records · Page 8Linked to original sources
PubMed1987

Measurement of canine left ventricular mass by using MR imaging.

This study assessed the capability of ECG-gated MR imaging for quantitating left ventricular mass by means of signal intensity-based and geometric methods for measuring left ventricular mass of normal dogs and dogs with left ventricular hypertrophy. Mass was measured on transverse images encompassing the left ventricle during both diastole and late systole. Partial-volume errors were minimized by measuring the length of the left ventricle on a sagittal image and weighting the mass of end slices accordingly. The range of postmortem left ventricular mass was 61-100 g. The linear relationship between postmortem left ventricular mass and mass measured via MR images correlated closely when MR imaging measurements were done at either end diastole (r = .94) or late systole (r = .94). The standard errors of the estimate were 13.7 and 14.7 g for images gated to end diastole and late systole, respectively. Inter- and intraobserver reproducibility showed excellent agreement (r = .93 and r = .89 for end diastole and r = .99 and r = .93 for late systole, respectively). Thus, left ventricular mass can be quantified accurately and reproducibly over a wide range of masses by using ECG-gated MR imaging.

Animals↗
PubMed1987

Cine MR imaging: potential for the evaluation of cardiovascular function.

MR imaging is valuable in defining cardiac anatomy in a variety of cardiac abnormalities. However, evaluation of cardiac function by this technique has been limited by long imaging times and low temporal resolution. New, recently described pulse sequences shorten imaging time considerably and improve temporal resolution. This paper reports our early experience with cine MR imaging of the heart, a technique of gradient-recalled acquisition in the steady state (GRASS) that uses low flip angles and gradient-recalled echoes. Images were obtained in 36 subjects (14 normal volunteers and 22 patients with coronary artery or valvular heart disease) and displayed in a cinegraphic mode for assessment of cardiac function. The acquisition of 10 to 12 levels, covering the whole heart with up to 24 time frames per level, required a maximum imaging time of only 30 min. Because systole and diastole were readily identified, and the contrast between blood and surrounding structures was excellent, systolic wall thickening, wall motion, and motion of the cardiac valves were visualized easily. Regions of myocardial infarcts were clearly visible and characterized by lack of systolic wall thickening and/or diastolic wall thinning. Turbulence caused signal loss within the flowing blood, which usually had higher signal intensity than myocardium. Therefore, turbulent blood flow in valvular regurgitation and in valvular and subvalvular stenosis could be detected. Cine MR imaging is a promising new technique for the evaluation of myocardial and valvular function.

Adult↗
PubMed1987

Measurement of myocardial infarct size at early and late time intervals using MR imaging: an experimental study in dogs.

The current study assessed the capability of ECG-gated MR imaging to quantitate both the percentage of the left ventricle involved by acute myocardial infarction and the mass of acute myocardial infarction at 3 and 21 days after coronary occlusion in dogs. Infarct mass was measured from gated transverse MR images using computer-generated calculated-T2 images. T2 images provided accentuation of the boundary between infarcted and normal myocardium as well as objective, reproducible calculation of image voxels representing infarcted myocardium. Postmortem and in vivo MR infarct mass and percentage correlated closely at 3 days (r = .98, SEE = 0.73 g; r = .97, SEE = 1.2%), and 21 days (r = .94, SEE = 1.54 g; r = .95, SEE = 1.61%). Left ventricular mass, infarct mass, and percentage of infarct were measured on end-diastolic MR images. Infarct mass at 3 and 21 days was not significantly different, with a mean deviation of 0.63 g. There was close intra- and interobserver reproducibility (r = .99 and r = .90, respectively) for measurement of infarct mass. The quantitative technique employed for determining the mass of acute myocardial infarctions, based on the different T2 relaxation times of infarcted and normal myocardium, provides for objective analysis and reproducibility. With this technique, MR provides an accurate method for assessing the mass of acute infarcts and the percentage of the left ventricle involved by the infarct both early and late after coronary occlusion.

Animals↗
PubMed1987

Ventricular septal defect: visualization of shunt flow and determination of shunt size by cine MR imaging.

Cine MR imaging is a new, fast technique that employs low flip angles, short repetition and echo times, and gradient-refocused echoes. This technique was used in three patients with documented ventricular septal defects (VSDs) to obtain transverse and oblique sections of the heart spanning the cardiac cycle. In all patients, cine MR imaging showed high-velocity turbulent blood flow across the defect as areas of low signal intensity extending from the left ventricle to the right ventricle. In the oblique sections oriented parallel to the interventricular septum it was possible to identify the cross-sectional area of the VSD. Quantification of the left-to-right shunt was performed by comparing left and right ventricular stroke volumes determined from end-diastolic and end-systolic volumes of both ventricles. Cine MR imaging provides important functional information and anatomic detail in patients with VSD and may be useful for diagnosis, determination of severity, and noninvasive monitoring of the disease.

Coronary Circulation↗
PubMed1987

Evaluation of pleural and pericardial effusions by magnetic resonance imaging.

MR examinations of 36 patients with pleural and/or pericardial effusions were retrospectively evaluated. The purpose of this study was to determine of MR imaging is capable of differentiating between pleural and pericardial effusions of different compositions using standard electrocardiogram (ECG)-gated and non-gated spin echo pulse sequences. Additional data was obtained from experimental pleural effusions in 10 dogs. The results of this study indicate that old hemorrhages into the pleural or pericardial space can be differentiated from other pleural or pericardial effusions. However, further differentiation between transudates, exudates and sanguinous effusions is not possible on MR images acquired with standard spin echo pulse sequences. Respiratory and cardiac motion are responsible for signal loss, particularly on first echo images. This was documented in experiments in dogs with induced effusions of known composition; "negative" T2 values consistent with fluid motion during imaging sequences were observed in 80% of cases. However, postmortem studies of the dogs with experimental effusions showed differences between effusions with low protein concentrations and higher protein concentrations. We conclude from our study that characterization of pleural and pericardial effusions on standard ECG-gated and non-gated MR examinations is limited to the positive identification of hemorrhage. Motion of the fluid due to cardiac and respiratory activity causes artifactual and unpredictable changes in intensity values negating the more subtle differences in intensity associated with increasing protein content.

Animals↗
PubMed1986

Occlusive and reperfused myocardial infarcts: effect of Gd-DTPA on ECG-gated MR imaging.

In vivo magnetic resonance (MR) imaging was performed to determine the effect of gadolinium-DTPA on MR intensity and relaxation times of occlusive and reperfused acute myocardial infarcts. In 18 dogs the left anterior descending (LAD) coronary artery was ligated. Five hours after LAD artery occlusion, six dogs in group 1 received intravenous Gd-DTPA, 0.5 mmol/kg, and 6 dogs in group 2 received 0.1 mmol/kg. The myocardia of the remaining six dogs (group 3) were reperfused after 1 hour of coronary artery occlusion; these dogs received 0.1 mmol/kg Gd-DTPA intravenously 5 hours later. MR imaging was performed before (control) and 5 minutes after Gd-DTPA administration. Intravenous administration of 0.1 mmol/kg Gd-DTPA significantly improved contrast between infarcted and normal myocardium on T1-weighted spin echo images in group 3. In all groups, T2-weighted precontrast images provided contrast between infarcted and normal myocardium equivalent or better than that provided by T1-weighted postcontrast images. Thus, Gd-DTPA did not improve contrast between ischemically injured and normal myocardium in the early hours after coronary artery occlusion.

Animals↗
PubMed1986

Magnetic resonance imaging of cardiac transplants: the evaluation of rejection of cardiac allografts with and without immunosuppression.

The purpose of this study was to evaluate the potential of magnetic resonance imaging (MRI) in vivo for the characterization of tissue changes associated with acute myocardial rejection after cardiac transplantation. Of 15 dogs that underwent heterotopic cardiac transplantation, six served as untreated controls, and nine received immunosuppressive therapy (25 mg/kg/day cyclosporine, 1 mg/kg/day prednisone). Serial electrocardiographically gated MRI (spin-echo technique) and histologic examinations of allograft biopsy samples were performed for each dog at 2 to 3, 7 to 10, 14 to 17, and 26 to 29 days after transplantation and immediately after animals were killed. Untreated allografts showed a significant increase (p less than .01) in T2 (spin-spin) relaxation time (T2 = 66 +/- 8 msec) and intensity values compared with values in the native hearts (T2 = 44 +/- 6 msec) as early as 1 week after transplantation. The significant difference in T2 values could be observed in vivo as well as on postmortem examination and corresponded to histologic progression of the rejection process. There was no significant difference in T1, T2, or intensity values in cyclosporine-treated allografts and native hearts except in two dogs in which T2 relaxation times and signal intensity in the transplanted hearts increased simultaneously with histologic evidence of rejection, indicating failure of immunosuppressive therapy. There was a significant correlation between histologic grading of severity of rejection and T2 relaxation times of the cardiac transplants (r = .72). Likewise, there was a significant linear relationship between T2 values in vivo and percent water content when the differences between native hearts and allografts were compared (r = .92, p less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

MRI of reperfused myocardial infarct in dogs.

The current study evaluated the capability of magnetic resonance imaging (MRI) to detect acutely injured myocardium in the first 5 hr after a 1-hr period of occlusion followed by reperfusion of the coronary artery and to determine if magnetic relaxation times could be used to differentiate injured from normal myocardium. Fourteen dogs underwent left anterior descending coronary arterial occlusion for 1 hr, followed by reperfusion. Electrocardiographic gated MRI was performed before and during coronary artery occlusion and immediately after reperfusion, and serially up to 5 hr postreperfusion. In all dogs with postmortem evidence of myocardial infarction (n = 7), regional increase of signal intensity was observed in the anterior wall of the left ventricle as early as 30 min after reestablishing blood flow to the jeopardized myocardium. The area of increased signal intensity in the myocardium conformed to the site of myocardial infarction found at autopsy. The signal intensities of the jeopardized myocardium were significantly (p less than 0.01) greater than those of normal myocardium at 30 to 300 min postreperfusion. The T2 (spin-spin) relaxation time was significantly (p less than 0.05-p less than 0.01) prolonged in the region of the reperfused myocardial infarct at 30 min (59.6 +/- 13.1 msec) and remained prolonged up to 300 min (62.6 +/- 12 msec) postreperfusion compared with the T2 of normal myocardium (40.6 +/- 5.2 msec). Of the remaining seven dogs, four developed fatal arrhythmias during the reperfusion procedure and three dogs had no evidence of myocardial infarction at pathologic examination. Signal intensities and T2 relaxation times in these three dogs did not change during the experiment. Thus, acutely infarcted and reperfused myocardium can be detected by in vivo gated MRI, using the spin-echo technique, as early as 30 min after reperfusion. The jeopardized myocardium is characterized by a prolonged T2 relaxation time and, therefore, best visualized on T2-weighted images.

Animals↗
PubMed1986

MRI of the normal pericardium.

The visibility and thickness of the pericardium, as depicted by MRI, and the changes of these parameters over the cardiac cycle were determined in 18 normal subjects. Gated, cycled, multisection images were obtained in the transaxial orientation. Using a score-point system for quantification, there was better visualization of the low-intensity pericardial line during systole as compared with diastole (p less than 0.005). Pericardial thickness was 1.2 +/- 0.5 mm in diastole and 1.7 +/- 0.5 mm in systole (p less than 0.001) as measured in a midventricular section in front of the right ventricle; both values exceeded the thickness of 0.4 to 1.0 mm reported for anatomic measurements of pericardial thickness. The layer of normal pericardial fluid present in the pericardial space should also have low intensity, and it likely contributes to the overall pericardial thickness as visualized by MRI. Since MRI is sensitive to the small amount of normal pericardial fluid and depicts its anatomic distribution, it should be valuable in detection and quantification of even small pericardial effusions.

Adult↗
PubMed1986

MRI of the abnormal pericardium.

To evaluate the use of MRI in the diagnosis of pericardial disease, 63 patients with pericardial abnormalities or clinically suspected pericardial disease were studied retrospectively. Twenty-three patients had pericardial effusion, 19 patients had pericardial thickening, and 11 patients were referred for evaluation of masses with possible pericardial involvement. The other 10 patients were referred for differentiation of constrictive pericarditis from restrictive cardiomyopathy and eventually were found to have pericardial hematoma or normal pericardium as assessed by MRI. The calculated size of pericardial effusion by MRI showed a good correlation with semiquantitative echocardiographic estimations. MRI could demonstrate fibrinous adhesions in patients with uremic pericarditis. It was also of great value in the differential diagnosis of constrictive pericarditis vs restrictive cardiomyopathy. Pericardial thickness of more than 4 mm was found in patients with constrictive pericarditis. Normal pericardial thickness was demonstrated by MRI in the three patients with restrictive cardiomyopathy. MRI diagnosed hemopericardium correctly as the cause of constrictive symptoms in two patients. Pericardial thickening in patients after cardiac surgery was commonly found by MRI and usually was not associated with clinical signs of constrictive pericarditis. MRI proved to be useful in the diagnosis of pericardial cysts and in the evaluation of paracardiac masses with possible pericardial involvement. MRI is an important technique in the evaluation of the pericardium. It can provide important additional information when diagnosis cannot be made adequately by other noninvasive imaging techniques.

Adolescent↗
PubMed1985

[Analysis of right atrium function in patients with chronic pressure overload of the right ventricle].

Right atrial function was evaluated in 16 patients with and without chronic right ventricular pressure overload. A simultaneous right atrial pressure recording using a catheter-tip-micromanometer and right atrial volume determination using cross-sectional echocardiography were performed. The pressure-volume curve of the right atrium was composed of an a-loop and a v-loop. The ratio of active atrial emptying to right ventricular stroke volume in patients with right ventricular pressure overload was significantly larger than in the control group (36 +/- 6% vs. 23 +/- 5%, p less than 0.04). The right atrial work was also significantly greater in patients with right ventricular pressure overload (6.2 +/- 2.0 mWs) than in normal subjects (4.2 +/- 2.0 mWs, p less than 0.04). The ratio of active atrial emptying to ventricular stroke volume and right atrial work were significantly related in both control group and patients with right ventricular pressure overload (r = 0.83). Right atrial work also showed a significant linear correlation with right atrial work before active atrial emptying (r = 0.92). We conclude that in patients with right ventricular pressure overload the right atrium shows more pronounced active emptying and contributes to better diastolic filling of the right ventricle.

Angina Pectoris, Variant↗
PubMed1985

[Pathophysiology of tricuspid insufficiency: analysis of the motion of the tricuspid valve annulus using 2-dimensional echocardiography].

We investigated tricuspid annular motion in patients with pulmonary hypertension and in normal controls to determine the greatest minimal diameter and percentage shortening of the tricuspid annulus required for functional tricuspid regurgitation. 73 patients were studied by 2-dimensional echocardiography: a control group of 30 patients (group I); 43 patients had pulmonary hypertension, 9 of whom were still in sinus rhythm (group II), the other 34 patients had atrial fibrillation. 19 of these showed competent tricuspid valve with contrast echocardiography (group III), whereas the 15 remaining patients had functional tricuspid regurgitation (group IV). An analysis of shape and position changes of tricuspid annulus during the heart cycle was performed. The maximal diameter (mm/m2) in the apical 4 chamber view was in group I 17.5 +/- 1.4, in group II 20.7 +/- 3.2 (vs. group I p less than 0.05), in group III 19.0 +/- 3.4 (vs. group II NS) and in group IV 25.7 +/- 6.0 (vs. group III p less than 0.001). The values for the minimal annular diameter (mm/m2) were in group I 13.7 +/- 1.2, in group II 17.4 +/- 3.5 (vs. group I p less than 0.01), in group III 16.6 +/- 3.3 (vs. group II NS) and in group IV 23.6 +/- 5.7 (vs. group p less than 0.001). The percent decrease (%) in group I was 21.5 +/- 3.3, in group II 17.0 +/- 6.9 (vs. group I p less than 0.05), in group III 12.8 +/- 4.7 (vs. group II p less than 0.05) and in group IV 7.9 +/- 3.4 (vs. group III p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiography↗
PubMed1984

[Heart lesions caused by blunt trauma. Echocardiographic follow-up studies].

The increased traffic has been accompanied by increased risk of blunt thoracic trauma. Trauma caused by the steering wheel leads to thoracic damage with serial rib fractures frequently involving cardiac damage. Apart from routine estimation of MB-CK and daily recording of the ECG echocardiographic follow-up is of considerable importance. Cardiac trauma may be recognised more promptly than by ECG and potential late complications can be outlined in time.

Aged↗
PubMed1984

[Determination of the size of the right atrium in patients with pulmonary hypertension using 2-dimensional echocardiography].

Normal values for right atrial area and tricuspid annular diameter and their percentage shortening measured from the two-dimensional echocardiographic four-chamber view are now available. In this study right atrial size of patients with pulmonary hypertension is evaluated and the results compared with the M-mode findings of the right ventricle in order to detect pulmonary hypertension. Hemodynamics and echocardiograms of 60 patients (mean age 57 +/- 10 years) with mitral stenosis III-IV NYHA and concomitant pulmonary hypertension were examined. 20 patients in group I with atrial fibrillation had additional functional tricuspid incompetence. Unlike the 20 patients in group II, who had atrial fibrillation, the remaining 20 in group III were still in sinus rhythm. The mean pulmonary artery pressure was 44.1 +/- 9.3 mmHg in group I, in group II 33.9 +/- 6.3 mmHg (grp. I vs. grp. II p less than 0.001) and in group III 33.2 +/- 7.1 mmHg (grp. II vs. grp. III ns). The end-systolic index of the right atrial area in group I was 19.6 +/- 5.7 cm2/m2 and thus significantly greater than in group II with 10.6 +/- 2.3 cm2/m2 (p less than 0.001) and in group III with 9.1 +/- 2.5 cm2/m2 (p less than 0.001). The maximal diameter of the tricuspid annulus measured 24.6 +/- 5.5 mm/m2 in group I, 18.9 +/- 3.5 mm/m2 in group II (grp. I vs. grp. II p less than 0.001) and 20.2 +/- 2.2 mm/m2 in group II (grp. I vs. grp. II p less than 0.001) and 20.2 +/- 2.2 mm/m2 in group III.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMedDate not supplied

MRI assessment of myocardial viability: comparison with other imaging techniques.

The identification of dysfunctional but viable myocardium in patients with coronary artery disease with or without a history of myocardial infarction is of paramount clinical importance since viable myocardial areas are most likely to benefit from revascularization, whereas revascularization of scar tissue will not lead to improvement of left ventricular function. In some patients cardiac catheterization itself already provides important clues to the presence of viable myocardium based on the degree of wall motion abnormalities, post-extrasystolic improvement of wall motion, the presence of collateral vessels or persisting angina in a patient with single vessel disease. However, due to the complexity of viability assessment especially in patients with severely depressed left ventricular function and multi-vessel disease, viability tests are usually requested after the results of coronary angiography are known. Among the diagnostic armamentarium to identify viable myocardium the most established techniques are single photon emission computed tomography (SPECT), positron emission tomography (PET) if available and dobutamine stress-echocardiography. With the application of magnetic resonance imaging (MRI) in clinical cardiology an important and exciting diagnostic tool has been added for the prospective identification of viable myocardium for purposes of guiding therapeutic interventions in individual patients. This article reviews comparative studies between MRI and established imaging techniques like PET, SPECT and dobutamine-echocardiography with respect to the assessment of viable myocardium in patients with acute myocardial infarction and chronic coronary artery disease.

Angina Pectoris↗