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Biomedical subjects

W F Shen

Publications and source records attributed to W F Shen.

80 records · Page 5Linked to original sources
PubMed1984

Anterolateral ST segment depression in acute inferior myocardial infarction: angiographic and clinical implications.

We examined the relationship between coronary anatomy and anterolateral ST segment depression during inferior acute myocardial infarction (AMI) in 84 consecutive survivors of inferior AMI, who underwent prospective coronary angiography a median time of 2 weeks after AMI. Multivessel disease was defined as two or more significantly (greater than 70%) stenosed vessels. A QRS scoring system was used to estimate myocardial infarct size. Patients with ST depression had more multivessel disease compared to patients with no ST depression (53% vs 6%, p less than 0.01), more left anterior descending stenoses (36% vs 10% p less than 0.05), and higher QRS scores (5.8 +/- 3.2 vs 2.6 +/- 1.8, p less than 0.01) indicating larger infarcts. Patients with ST depression and one-vessel disease (47%) still had higher QRS scores compared to patients with no ST depression (4.8 +/- 2.9 vs 2.6 +/- 1.8, p less than 0.001) and had an increased prevalence of infarct-related vessels with a terminal branch supplying the left ventricular lateral wall or apex. We conclude that anterolateral ST depression during inferior AMI may indicate the presence of additionally stenosed vessels or that the infarct-related vessel has a large vascular territory. The absence of ST depression virtually precludes multivessel disease.

Adult↗
PubMed1984

Noninvasive assessment of acute effects of nifedipine on rest and exercise hemodynamics and cardiac function in patients with aortic regurgitation.

The acute effects of nifedipine (20 mg sublingually) on hemodynamics and cardiac function were studied at rest and during supine bicycle exercise in 20 patients with aortic regurgitation. At rest, heart rate increased by 13%, systemic vascular resistance decreased by 34% and regurgitant index decreased by 17%. The change in systemic vascular resistance was related to its initial rest level (r = 0.82, p less than 0.001) and to the changes in forward cardiac output (r = 0.58, p less than 0.01) and regurgitant index (r = 0.60, p less than 0.01). Left ventricular end-diastolic and end-systolic volumes, stroke volume and ejection fraction were unchanged, whereas right ventricular ejection fraction increased. During exercise, nifedipine administration further increased heart rate by 8% and decreased systemic vascular resistance by 19%. Both forward stroke volume and forward cardiac output increased, but total left ventricular stroke volume was unchanged, resulting in a significant decrease in regurgitant index. Although left ventricular end-diastolic volume was slightly decreased, end-systolic volume did not increase; thus, ejection fraction was higher than that during control exercise (p less than 0.01). Right ventricular ejection fraction increased further. In aortic regurgitation, the acute administration of nifedipine improved cardiac performance and reduced regurgitation at rest and during exercise as a result of afterload reduction and increased heart rate. Whether these beneficial effects will occur during long-term therapy requires further investigation.

Adult↗
PubMed1983

The QRS scoring system for estimating myocardial infarct size: clinical, angiographic and prognostic correlations.

The relation between a QRS score derived from the routine electrocardiogram and left ventricular function was investigated in 181 patients after myocardial infarction. Patients with left ventricular hypertrophy and conduction defects were excluded. The QRS score correlated closely with the severity of wall motion abnormalities and left ventricular ejection fraction. The more severe the dyssynergy, the higher the QRS score (hypokinesia = 3.0; akinesia = 5.4; dyskinesia = 9.1). The left ventricular ejection fraction (percent) = 66 - (3.3 x QRS score) (correlation coefficient [r] = -0.81, probability [p] less than 0.001). With use of this regression equation, the QRS score predicted angiographic left ventricular ejection fraction to within 12% of the angiographic ejection fraction in 29 of 30 additional patients studied prospectively. The QRS score was also related to clinical functional class. The worse the clinical manifestation of left ventricular dysfunction, the higher the QRS score (Killip class I = 3.5; class II = 6.5; class III = 7.1). A QRS score greater than or equal to 7 had a specificity of 97% and a sensitivity of 59% for predicting an ejection fraction of less than 45%. Patients with a QRS score of 7 or greater had severe wall motion abnormalities, higher peak serum creatine kinase levels, higher prevalence of multivessel coronary disease, poor clinical functional class and an unfavorable outcome. The QRS score provides an inexpensive, clinically useful estimate of left ventricular function after myocardial infarction and can identify patients at high risk.

Adult↗
PubMed1982

Nucleotide sequence of the rrnG ribosomal RNA promoter region of Escherichia coli.

The primary structure of the promoter region for a ribosomal RNA transcription unit (rrnG) of Escherichia coli K12 has been determined. The sequence was obtained from 1 1.5 kbp EcoRI fragment derived from the hybrid plasmid pLC23-30. This fragment contains 455 bp preceding P1 of the rrnG promoter region and 674 bp of the rrnG 16S RNA gene. The sequence before the rrnG promoter region contains an open reading frame (ORF-BG) followed by a possible hairpin structure that resembles other known transcription terminators. The sequence of the rrnG promoter region is similar but not identical to that of rrnA and rrnB. Several minor differences between the sequences of the 16S RNA genes of rrnG and rrnB were also noted. In addition, sequences were found that could generate special structures involving the promoter regions of rrn loci. Such structures are described and their possible involvement in the regulation of ribosomal RNA synthesis is discussed.

Base Sequence↗
PubMed1981

Nucleotide sequence at the end of the gene for the RNA polymerase beta' subunit (rpoC).

We have determined the DNA sequence surrounding the transcription terminator following rpoC, the gene that codes for the beta' subunit of RNA polymerase in E. coli K12. The 2044 bp sequence obtained contains the distal 335 codons of rpoC followed by a 212 bp non-coding region and a second open reading frame (ORFa) of 179 codons. The final 181 nucleotides of the sequence form the 5' end of a third open reading frame (ORFb). The in vivo 3' end of the rpoC mRNA was located by analysis of RNA/DNA hybrids cleaved with nuclease S1 (S1 mapping). These results indicated that the major transcription termination of the rplJL-rpoBC transcription unit occurs a short distance past the translation stop codon for rpoC. Four regions of symmetry, suggesting secondary structure in the mRNA, were found in the DNA sequence near the rpoC translation termination codon. The last of these hairpin structures is similar to other rho-independent transcription terminators and its 3' end coincides with the end of the rpoC mRNA as predicted by S1-mapping. Inspection of the open reading frames indicates that rpoC uses a high percentage of codons that are recognized by the major tRNA species of E. coli while ORFa and ORFb contain many codons recognized by minor tRNA species. ORFa specifies a very basic peptide.

Base Sequence↗
PubMedDate not supplied

A comparison of the effects of beta-blockers with and without intrinsic sympathomimetic activity on hemodynamics and left ventricular function at rest and during exercise in patients with coronary artery disease.

The effects on hemodynamics and left ventricular function of propranolol and pindolol, beta-blockers without and with intrinsic sympathomimetic activity (ISA), respectively, were compared in six men with stable exertional angina at rest and during symptom-limited bicycle exercise. The study was controlled and double blinded, and the order of drug administration was randomized. The dosage of each drug (propranolol 0.15 mg/kg i.v., pindolol 0.02 mg/kg i.v.) was chosen to reduce exercise tachycardia by approximately 18%. Exercise capacity and duration were similar after each drug, and both drugs similarly reduced ST depression during exercise. At rest, propranolol significantly reduced heart rate, systolic arterial pressure, rate-pressure product, stroke volume index, cardiac index, and left ventricular ejection fraction, and increased systemic vascular resistance. In contrast, pindolol significantly reduced only the rate-pressure product and cardiac index, and to a lesser extent than propranolol. During exercise on the other hand, both drugs reduced the heart rate, arterial pressure, rate-pressure product, and cardiac index to a similar degree. Neither drug altered pulmonary artery wedge pressure, systemic vascular resistance, stroke volume index, left ventricular ejection fraction, or left ventricular end-diastolic and end-systolic volume indices. At equipotent beta-blocking dosages, ISA in pindolol reduced the effects of beta-blockade on resting hemodynamics and left ventricular function compared to propranolol, but during exercise the influence of ISA was reduced; and both pindolol and propranolol exert similar effects on hemodynamics and left ventricular function.

Adult↗
PubMedDate not supplied

Clinical significance of intracavitary spontaneous echo contrast in patients with dilated cardiomyopathy.

To assess the occurrence rate and major determinants of spontaneous echo contrast and to examine its impact on thromboembolic events and mortality in patients with dilated cardiomyopathy, 86 hospitalized patients (73 men and 13 women, mean age 63 +/- 11 years) with dilated cardiomyopathy who underwent transthoracic and transesophageal echocardiographic examinations were followed up for a mean of 20 +/- 13 months. Spontaneous echo contrast was observed in 36 patients (42%) and was detected only with the transesophageal approach. It was seen in the left atrium in 33 patients, in both right and left atria in 1 patient, in both left atrium and left ventricle in 1 patient, and in the descending aorta in 1 patient. Spontaneous echo contrast was more frequent in the presence of atrial fibrillation (p < 0.05), left atrial enlargement (p < 0.02) and severely depressed left ventricular function (p < 0.01), but was less common in patients with moderate to severe mitral regurgitation (p < 0.05). This imaging phenomenon was the only significant independent predictor of intracardiac thrombus formation and previous and subsequent thromboembolic events. During follow-up, there were 26 deaths, and survival in patients with spontaneous echo contrast was significantly lower than in those without it (p < 0.02). A spontaneous echo contrast is commonly detected with transesophageal echocardiography in patients with dilated cardiomyopathy especially in the presence of atrial fibrillation, left atrial enlargement and severe left ventricular dysfunction. This imaging phenomenon represents an important marker for thromboembolic risk and may influence the treatment and clinical outcome of these patients.

Adolescent↗