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Biomedical subjects

C C Chen

Publications and source records attributed to C C Chen.

At least 685 records · Page 38Linked to original sources
PubMed1980

Two dimensional echocardiography in mitral, aortic and tricuspid valve prolapse. The clinical problem, cardiac nuclear imaging considerations and a proposed standard for diagnosis.

The mitral valve prolapse syndrome may present with a variety of clinical manifestations and has proved to be a common cause of nonspecific cardiac symptoms in clinical practice. Primary and secondary forms must be distinguished. Myxomatous degeneration appears to be the common denominator of the primary form. The diagnostic standard of this form has not previously been defined because the detection of mitral leaflet tissue in the left atrium (prolapse) on physical examination or angiography is nonspecific. M mode echocardiography has greatly enhanced the recognition of this syndrome but has not proved to be the best diagnostic standard because of its limited view of mitral valve motion. The advent of two dimensional echocardiography has provided the potential means for specific identification of the mitral leaflet motion in systole and can be considered the diagnostic standard for this syndrome. Primary myxomatous degeneration with leaflet prolapse is not localized to the mitral valve. Two dimensional echocardiography has detected in preliminary studies tricuspid valve prolapse in up to 50 percent and aortic valve prolapse in about 20 percent of patients with idiopathic mitral valve prolapse.

Angiocardiography↗
PubMed1980

Echocardiographic detection of coronary artery disease. Detection of effects of ischemia on regional myocardial wall motion and visualization of left main coronary artery disease.

M mode and cross-sectional echocardiographic studies at rest have been used to detect regional left ventricular wall motion abnormalities as a sign of hemodynamically significant coronary artery disease. These techniques have proved to be fairly specific but not highly sensitive. Detection of new regional wall motion abnormalities with cross-sectional echocardiography during exercise appeared practical in 80 percent of patients in preliminary studies; the finding of such abnormalities is highly specific for the presence of coronary artery disease and, with this approach, the sensitivity of echocardiography is improved. Thus, patients with anatomically severe coronary artery disease on angiography may not manifest an echocardiographic abnormality in regional wall motion even during exercise. The direct noninvasive detection of the left main coronary artery in up to 90 percent of patients studied with cross-sectional echocardiography using the short axis or apical approach, or both, has been well defined. A high sensitivity and specificity of detecting anatomically severe left main coronary artery disease using the criteria of both luminal impingement and the presence of high intensity echoes have been confirmed. Further advances in imaging techniques may allow for better definition of the coronary arterial tree.

Coronary Disease↗
PubMed1980

Tricuspid regurgitation in tricuspid valve prolapse demonstrated with contrast cross-sectional echocardiography.

To determine the prevalence of tricuspid regurgitation in patients with tricuspid valve prolapse and to define further the criteria for the diagnosis of tricuspid regurgitation on contrast echocardiography, evaluation was made of 45 patients who had adequate contrast studies. There were four groups of patients: Group A, 10 healthy control subjects with no evidence of structural heart disease on cardiac catheterization; group B, 10 patients with classic clinical evidence of tricuspid regurgitation; group C, 10 patients with cross-sectional echocardiographic evidence of mitral valve prolapse without tricuspid valve prolapse; and group D, 15 patients with both mitral and tricuspid valve prolapse on cross-sectional echocardiography. Tricuspid regurgitation was sought in each group by using the subxiphoid echocardiographic approach with peripheral venous injection of saline solution. The diagnosis required the presence of microcavitations in both the inferior vena cava and hepatic veins for at least three consecutive cardiac cycles. Tricuspid regurgitation was observed in no patients in group A, 10 of 10 patients in group B, 0 of 10 in groups C and 6 of 15 (40 percent) in group D. Contrast cross-sectional echocardiography proved to be a reliable technique for identifying tricuspid regurgitation with a high degree of specificity and sensitivity. Patients with tricuspid valve prolapse had a 40 percent prevalence rate of tricuspid regurgitation. This finding may identify a subgroup that requires particularly careful clinical follow-up care.

Adolescent↗
PubMed1980

Purification and characterization of histidyl-transfer RNA synthetase from Neurospora crassa.

Histidyl-tRNA synthetase (L-histidine:tRNAHis ligase (AMP-forming), EC 6.1.1.21) has been purified 921-fold from crude extracts of lyophilized mycelia of Neurospora crassa. Sodium dodecyl sulfate gel electrophoresis at pH 8.9 of the purified enzyme yields one band with an apparent Mr of 62 500. The estimated Mr by Sephadex gel filtration is 125 000. Thus the native histidyl-tRNA synthetase of N. crassa is a dimer, composed of two identical subunits. The Km values determined in the enzyme-catalyzed esterification of [14C]-histidine to tRNAHis are: for histidine, 5.8 x 10(-6 M, for ATP, 5.9 x 10(-4) M, and for tRNAHis, 1.2 x 10(-7) M. Effects of various intermediates of the histidine, tryptophan and arginine biosynthetic pathways on histidyl-tRNA synthetase activity were studied. The Ki values for imidazoleglycerol phosphate and histidinol (histidine intermediates and competitive inhibitors of the enzyme) are 1.1 x 10(-2) M, 1.3 x 10(-6) M, respectively. The Ki for indoleglycerol phosphate (a tryptophan intermediate and non-competitive inhibitor) is 1.2 x 10(-3) M.

Amino Acyl-tRNA Synthetases↗
PubMed1980

Rheumatic mitral stenosis:cross-sectional echocardiographic analysis.

Twenty-one patients with rheumatic mitral stenosis diagnosed by both M-mode echocardiography and hemodynamic findings were subjected to detailed cross-sectional echocardiographic studies. The age of the patients ranged from 27 to 79 years with 76% females. Left ventricular longitudinal, short axis, and apical four-chamber cross-sectional echocardiographic views were obtained in each patient. Three predominant patterns of anterior mitral leaflet motion on left ventricular longitudinal view were observed and correlated with the severity of mitral stenosis: Pattern A (eight patients) with diastolic leaflet doming and restricted leaflet tip motion. Pattern B (eight patients) tip and body leaflet motion, and Pattern C (five patients) with the entire leaflet motion restricted. Mitral valve prolapse as a rebound phenomenon was observed in three patients who had marked leaflet doming in Pattern A and two had severe obstruction. The longitudinal cross-sectional echocardiography was superior to the apical view in assessing the diastolic doming motion of the anterior mitral leaflet. Thus, longitudinal cross-sectional echocardiographic analysis of the pliability and degree of doming of the anterior of the pliability and degree of doming of the anterior mitral leaflet is valuable in estimating the severity of mitral stenosis.

Adult↗
PubMed1980

Echocardiographic features of atrioventricular and ventriculoatrial conduction.

The potential application of diagnostic ultrasound to understanding of the hemodynamic effects of various rhythm and conduction disturbances has not been fully explored. To investigate the change in cardiac function associated with various atrioventricular (A-V) sequencing intervals during cardiac pacing, simultaneous M mode and two dimensional echocardigraphic and hemodynamic studies were performed in 23 dogs. One to one A-V and ventriculoatrial (V-A) sequential pacing at cycle lengths of 400 and 300 ms revealed a stepwise reduction in left ventricular pressure and cardiac output as the A-V interval was changed from +100 to -100 ms. These reductions in cardiac hemodynamics were associated with decreases in left ventricular and increases in left atrial dimensions determined with echocardiography. Mitral valve excursion and the duration of valve opening remained constant over the entire range of A-V intervals. There was angiographic evidence of retrograde blood flow from the left atrium into the pulmonary venous system at an A-V interval of -50 and -100 ms, but no evidence of mitral regurgitation. Thus, correlative echocardiographic and hemodynamic studies can suggest multiple pathophysiologic mechanisms contributing to the decrements in cardiac function observed during tachyarrhythmias with intact A-V conduction as well as those occurring consequent to A-V nodal Wenckebach cycles.

Animals↗
PubMed1980

A new approach to visualize the left main coronary artery using apical cross-sectional echocardiography.

Patients undergoing coronary arteriography were studied to evaluate the feasibility of use of cross-sectional echocardiography to detect the left main coronary artery. Visualization of the left main coronary artery from the cardiac apex was attempted using a cranial transducer angulation. With this approach, the left main coronary artery was adequately visualized in 27 of 35 consecutive patients (77 percent) who were prospectively evaluated; in 12 of the 27 the bifurcation was clearly seen. In 26 of the 27 patients cross-sectional echocardiography correctly assessed the patency of the left main coronary artery as judged with coronary angiography. One patient had a false positive echocardiographic study; there were no false negative studies. A comparison of the short axis versus apical cross-sectional techniques in another group of 30 patients revealed the superiority of the apical approach in visualization of the left main coronary artery and its bifurcation; combined use of both techniques allowed for a 93 percent (rate of) success. Thus, apical cross-sectional echocardiography permits visualization of the left main coronary artery and its bifurcation and, therefore, has the potential for detecting left main coronary obstructive lesions.

Adult↗
PubMed1980

Noninvasive diagnosis of the cardiomyopathies.

The presenting clinical features of the cardiomyopathies are nonspecific. Echocardiography is useful in detecting patients with cardiomyopathy and determining proper management. Echocardiography can be used to determine both cardiac structural measurements and cardiac function.

Aortic Stenosis, Subvalvular↗
PubMed1980

Detecting left main coronary artery disease by apical, cross-sectional echocardiography.

To test the feasibility of imaging the left main coronary artery (LMCA) noninvasively as a means of detecting left main coronary artery disease, we studied 73 patients who underwent cardiac catheterization and cross-sectional echocardiography. Fifty-two had a normal LMCA (controls) and 21 had significant obstruction (greater than or equal to 50% luminal reduction). The apical, tomographic, cross-sectional, phased-array, echocardiographic approach was used, and the LMCA was imaged in 52 of 73 patients (71%). In 34 of 36 controls (94%) the LMCA was correctly judged as having no luminal obstruction. In the other two, and asymmetric, high-intensity echo in one wall of the artery suggested atherosclerotic disease, but coronary angiography revealed no obstruction. In 12 of 16 patients (75%) in whom significant LMCA disease was imaged, obstruction was predicted by echocardiographic criteria of either luminal irregularity or an asymmetric, high-intensity echo in the arterial wall. This preliminary study suggests that cross-sectional echocardiography appears to be a feasible, noninvasive technique to image the LMCA and to detect hemodynamically significant luminal obstruction.

Adult↗