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Biomedical subjects

M Pan

Publications and source records attributed to M Pan.

At least 91 records · Page 5Linked to original sources
PubMed1990

Balloon valvuloplasty for mitral restenosis after previous surgery: a comparative study.

We studied 203 patients with mitral stenosis treated by transarterial valvuloplasty. Forty two (group A) had undergone closed (n = 30) or open n = 12) surgical commissurotomy 15 +/- 5 years before. The remaining 161 had not undergone previous surgery (group B). There were no significant differences between both groups in terms of age, sex, functional class, left atrial size, two-dimensional anatomic features of the valve, incidence of mild basal mitral regurgitation, or ejection fraction. A comparative analysis of both groups showed no significant differences in terms of changes in the mean gradient, mitral valve area, and incidence of severe postvalvuloplasty mitral regurgitation (9.5% versus 5.5%). Echo-Doppler follow-up studies (11 +/- 7 months) showed persistent gradient relief in either group. We conclude that the immediate and short-term results of balloon valvuloplasty in patients who had undergone previous surgery are similar to those observed in patients who had not had commissurotomy.

Catheterization↗
PubMed1990

Effect of lipoxygenase inhibitors on Ca2(+)-induced constriction of the rabbit ear artery.

1. The effects of nafazatrom, nordihydroguaiaretic acid (NDGA) and quercetin on Ca2(+)-induced vasoconstriction were studied in isolated rabbit ear arteries. 2. The arteries were perfused with Ca2(+)-free and high K+ (75 mM) Krebs bicarbonate buffer. Constriction of the artery was induced by addition of Ca2+ (1.5 mM) to the perfusion fluid. 3. Indomethacin (1 microM) did not alter the response to Ca2+. 4. Nafazatrom (2 or 5 microM) produced a concentration-dependent inhibition of the constrictor response to Ca2+ ranging from 4 to 23% after 1 hr of perfusion and 26 to 62% after 3 hr. 5. Similar effects were obtained with NDGA and quercetin (0.5 and 1 microM). 6. The inhibitory effects of nafazatrom and quercetin were antagonized by Ca2+ (2.5 mM) or Bay K 8644 (1 microM), a calcium channel activator. 7. Ca2(+)-induced contractions recovered within 30 min after discontinuation of perfusion with quercetin, whereas nafazatrom and NDGA had longer durations of action. 8. These results suggest that inhibitors of lipoxygenase antagonized Ca2(+)-induced vasoconstriction and that products of lipoxygenase metabolism may facilitate Ca2+ entry into vascular smooth muscle cells.

Animals↗
PubMed1990

[Role of percutaneous valvuloplasty in rheumatic mitral valve stenosis. Córdoba-Las Palmas cooperative study].

This article describes our findings on a prospective and cooperative study (Córdoba-Las Palmas) in 203 patients with mitral stenosis who underwent balloon valvuloplasty using a retrograde transarterial technique. We analyzed the immediate and mid-term results, and studied the factors determining an optimal result and those related to the new appearance or worsening of mitral incompetence after the procedure. On the other hand, we analyzed the results of mitral valvuloplasty in patients with previous mitral surgery, mild mitral stenosis and patients dilated while having an acute pulmonary edema. We observed a marked decrease in mean mitral gradient (17 +/- 7 to 6 +/- 3 mmHg; p less than 0.001) as well as a significant increase in mitral valve area (1.02 +/- 0.4 to 2.04 +/- 0.7 cm2; p less than 0.001). Echo-Doppler follow-up did not show significant changes in the residual mitral valve gradient. Multivariate analysis selected, as independent predictors of an optimal result, the presence of a pliable valve and the absence of basal mitral regurgitation. On the other hand, the presence of a lower ejection fraction, an older age and a higher baseline left ventricular endiastolic volume were independent factors determining progression of mitral regurgitation. In patients with previous mitral surgery, the clinical, echo and hemodynamic profiles, as well as the immediate results, were similar to those observed in patients with unoperated mitral stenosis. In the subgroup of mild mitral stenosis, we observed and optimal result in all cases, without major complications. Mitral valvuloplasty was dramatically effective in 8 patients treated during acute pulmonary edema.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[Infarct size determination using enzymatic methods in patients with early coronary recanalization].

To evaluate the usefulness of the infarct size determined by serial creatine kinase (CPK) measurements in patients with early reperfusion, we have studied 189 patients meaning in age 59.2 +/- 8.6 years, with acute myocardial infarction treated with streptokinase (STK); 81 of them by intracoronary route (group A), and 108 by intravenous administration (group B). In the group A we performed serial angiographic studies in the following conditions: baseline, immediately after STK infusion and before hospital discharge. In group B we performed only one angiographic control 5 +/- 3 days after. In patients with reperfusion, the parameters of left ventricular function correlated with cumulative creatine kinase release (MAX-CPKr) by linear regression in both groups. We observed a tendency to closer correlations in patients with left anterior descending or circumflex artery as the infarct related artery, in patients without previous infarction and in those who did not receive electrical shock for ventricular arrhythmias. In patients with unsuccessful reperfusion (n = 11), we also obtain a significant correlation (r = 0.72) between ejection fraction and MAX-CPKr. The slope of the regression line (b = 7.7 X 10(-5) was steeper (p less than 0.05) than that observed in recanalized patients, who were evaluated within the first 3 days (b = 2.2 X 10(-5), after 8 +/- 5 days (b = 2.7 X 10(-5), or before discharge, at 22 +/- 9 days (b = 2.6 X 10(-5).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

Abrupt homeostatic responses to transient intracardiac occlusion during balloon valvuloplasty.

The present study analyzes the hemodynamics of intracardiac occlusive periods during balloon mitral or aortic valvuloplasty and compares them with immediate plasma levels of atrial natriuretic factor (ANF), vasopressin and renin activity. Forty-nine patients were studied; 33 of them had mitral stenosis and 16 had aortic stenosis. The mean age was 52 +/- 17 years. During dilations pressures were monitored from the ascending aorta and left atrium. Plasma levels of ANF, vasopressin and renin were serially determined at baseline, after diagnostic procedures, within 15 to 30 seconds after the first 2 occlusive dilations, and 1 and 7 hours later. There were no significant changes in plasma renin throughout the study stages. ANF and vasopressin significantly increased after the dilations. These hormonal changes were related to the significant hemodynamic changes observed during intracardiac occlusion. The left atrial pressure correlated directly and significantly (r = 0.54, p less than 0.001) with plasma ANF levels throughout the conditions. On the other hand, the plasma vasopressin also correlated (r = 0.76, p less than 0.001) with systemic pressure in an exponential fashion. These findings show that abrupt releases of ANF and vasopressin occur immediately after intracardiac occlusive periods as a response to the acute and transient hemodynamic changes observed.

Adolescent↗
PubMed1989

Angiographic follow-up after balloon angioplasty for coarctation of the aorta.

Balloon angioplasty for coarctation of the aorta was performed in 45 patients; 17 (Group 1) were infants (mean age 34 +/- 43 days). This study focuses on the remaining 28 patients (Group 2), children and adults ranging in age from 2 to 31 years (mean 13 +/- 8). Two patients had had previous surgery for coarctation; in the remaining 26 the coarctation had not been surgically treated. Twenty patients (71%) had a discrete type of coarctation; the remaining eight had a diffuse or eccentric stenosis. Angiographic studies of the aorta were performed before and immediately after angioplasty in all 28 patients; 16 (57%) of them also underwent angiographic reevaluation 10 +/- 2 months later. The pressure gradient decreased immediately after angioplasty and was unchanged at follow-up. Residual gradient at follow-up ranged from 0 to 40 mm Hg (mean 11 +/- 13). Patients with a discrete type of coarctation had a lesser residual gradient than did patients with other anatomic types of coarctation. Angiographically, the stenosis also decreased after angioplasty (68 +/- 10% versus 24 +/- 17%; p less than 0.01); a new small, but significant decrease was observed at follow-up (9 +/- 18%; p less than 0.05). A quantitative analysis of the aorta at different levels revealed no significant changes proximal and distal to the coarctation segment; however, at the level of coarctation, a significant (p less than 0.01) and homogeneous increment was observed after dilation that was unchanged at follow-up. One (6%) of 16 reevaluated patients had a clear aneurysm at the site of dilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

In vivo administration of interleukin 1 elicits increased Ia antigen expression on B cells through the induction of interleukin 4.

The effects of the in vivo administration of interleukin 1 (IL 1) on lymphocytes from lymph node and spleen were analyzed. Mice received five daily subcutaneous (s.c.) injections of various doses of human recombinant IL 1 beta. Either 1 or 7 days after IL 1 treatment, spleens, popliteal and inguinal lymph nodes were collected. Lymphadenosis and splenomegaly were observed in the IL 1-treated animals. Lymph nodes from IL 1-treated mice contained a higher percentage of B cells than controls, and B cells from IL 1-treated mice expressed dramatically increased levels of Ia antigen. Lymphadenosis and splenomegaly, as well as the changes in subset distributions and Ia expression were transient. Concomitant treatment of mice with IL 1 and anti-IL 4 monoclonal antibody suppressed IL 1 effects on B cell Ia expression, but not on the B/T cell ratio. In situ hybridization analyses revealed that IL 1 treatment induced the expression of mRNA for IL 4, interferon-gamma, and IL 2 in lymph node and spleen cells. The distribution of cells expressing the various cytokine mRNA was markedly different between the spleens and lymph nodes.

Animals↗
PubMed1988

Physiopathology of transient ventricular occlusion during balloon valvuloplasty for pulmonic or aortic stenosis.

Hemodynamic observations were made at different cardiac levels during transient balloon occlusion at the time of aortic or pulmonary valvuloplasty in 37 patients (mean age 8 +/- 9 years); 22 had pulmonary stenosis and 15 had aortic stenosis (6 valvular and 9 discrete subvalvular types). Eighty-two tentative dilatations were performed in patients with pulmonary stenosis and 61 in patients with aortic stenosis. The hemodynamics of the right and left heart were monitored during inflation-deflation time. From selected tracings mean beat-to-beat pressures curves were constructed during occlusion-recovery time. The cycle length (RR interval) did not change significantly during occlusion, except for patients with pulmonary occlusion and patent foramen ovale, where a significant increase in cycle length (p less than 0.01) was observed during recovery time. The mean maximal increase in ventricular pressure reached 95% of basal values for the right ventricle and 58% for the left ventricle. The hypertension was retrogradely transmitted to all cardiac chambers. Angiographic observations during occlusion suggest that the atrioventricular valves and the foramen ovale, when patent, become escape orifices during occlusion, for adapting and relieving intracavitary pressures. The ventricle seems to adapt to sudden occlusion by generating hypertensive and hypokinetic contractions, with atrioventricular regurgitation.

Aortic Valve Stenosis↗
PubMed1988

Ca2+ antagonists and inhibitory effects of dopamine on isolated rabbit ear artery.

Rabbit ear arteries were isolated and perfused with Krebs-bicarbonate buffer. Brief periods of supramaximal nerve stimulation caused reproducible constriction of the arteries, which was inhibited by dopamine (EC50 approximately equal to 0.1 microM). Verapamil or flunarizine (at 1 or 5 microM) antagonized this inhibitory effect of dopamine. The maximal effect of verapamil, 5 microM was reached after 8 min and that of flunarizine, 5 microM after 40 min of perfusion with the drug. The antagonism of dopamine by verapamil, even at 5 microM, was incomplete (approximately equal to 80%), whereas flunarizine, 5 microM completely antagonized the effect of dopamine. Nitrendipine, nimodipine, or nisoldipine, at either 1 or 5 microM, or solvent (ethanol, 0.03%) had no significant effect on dopamine-induced inhibition of vasoconstriction even after perfusion for 40 min. Antagonism of dopamine at central synapses may conceivably explain reported Parkinsonian side effects of flunarizine. Our results suggest a mechanism for the tendency of flunarizine to cause Parkinsonism and an explanation why 1,4-dihydropyridines are not likely to have this side effect.

Animals↗
PubMed1988

Effects of BAY K 8644 on the responses of rabbit ear artery to electrical stimulation.

BAY K 8644 at 6.25 nM to 1 microM enhanced, in a concentration-dependent manner, both phases of the vasoconstrictor response of the isolated perfused rabbit ear artery to electrical stimulation. At 1 microM, BAY K 8644 enhanced the constrictor response by more than 250%. To study possible involvement of neurotransmitter release in the enhancement of the vasoconstrictor response by BAY K 8644, rabbit ear arteries were preincubated with [3H]norepinephrine and stimulated either electrically (for 1 or 5 min) or by 60 mM K+. BAY K 8644 (1 microM) had no effect on tritium release caused by 1-min periods of electrical stimulation. However, tritium release caused by 5-min periods of electrical stimulation or by 60 mM K+ was enhanced in the presence of BAY K 8644. It was concluded that BAY K 8644 enhances vasoconstrictor effects of electrical stimulation of rabbit ear artery by primarily a direct agonist action on Ca2+ channels in vascular smooth muscle cells. Following sustained depolarization, however, the drug may also enhance the release of neurotransmitter from sympathetic nerve endings. Under certain conditions, this release may contribute to the overall action of BAY K 8644.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1987

Human fetal pancreas--a potential source for transplantation.

Human fetal pancreas (HFP) represents an ideal tissue source for transplantation into diabetic patients. Transplantation of HFP lacks many of the technical problems associated with whole organ transplantation and HFP is readily available. In order to proceed with clinical HFP transplantation it must be demonstrated that HFP can reverse experimentally induced diabetes, that HFP can respond to glucose challenge in a manner similar to adult tissue, and that the immunogenicity of HFP can be reduced. We transplanted HFP (13-17 weeks gestational age) beneath the kidney capsule of streptozotocin-induced diabetic BALB/c nu/nu mice. Within 6 to 8 weeks following transplantation, 6 out of 7 (88%) animals became normoglycemic. Oral glucose tolerance tests were performed to determine in vivo graft function. Results in cured animals were identical to those of normal BALB/c nu/nu mice. In vitro insulin response to glucose challenge demonstrated that grafted HFP was capable of insulin secretion in the presence of high glucose while fresh fetal tissue was not. Human passenger leukocytes, identified immunohistologically at various times after transplantation with monoclonal antibodies to HLA-DR and Leu 10, were greatly reduced by 32 weeks posttransplant. Our data demonstrate that HFP will differentiate and mature in the diabetic nude mouse and that human passenger leukocyte content can be reduced. These findings suggest that HFP is functionally suitable for transplantation into diabetic patients.

Animals↗
PubMed1987

Assessment of Björk-Shiley and porcine mitral valve dysfunction by m-mode echocardiographic left ventricular dimension.

In this study of 46 patients with mitral valve prostheses, we report on the accuracy of the left ventricular maximum filling velocity (LVMFV) index as a diagnostic tool for valve dysfunction. Echocardiographic left ventricular internal dimensions were measured every 0.05 seconds, and every measure was transferred to an axis system. The tangent to this curve was traced at the point of maximum rate of increase of dimension, and the slope in mm/sec represents the LVMFV index. Six patients, each with an obstructed mitral valve prosthesis, had a reduced LVMFV index (p < 0.001). On the other hand, eight patients with a paravalvular leak showed a LVMFV index significantly higher (p < 0.05) than patients with a normally functioning mitral valve prosthesis. The results of this study suggest that analysis of the LVMFV index can be a useful and reliable substitute for other noninvasive diagnostic techniques in evaluating certain patients with suspected prosthetic mitral valve malfunction.

Journal Article↗