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Biomedical subjects

M L Young

Publications and source records attributed to M L Young.

At least 55 records · Page 3Linked to original sources
PubMed1994

The electrophysiological effects of antiarrhythmic potential of a secoaporphine, N-allylsecoboldine.

1. A satisfactory antiarrhythmic potential of N-allylsecoboldine, a synthetic derivative of secoaporphine, has been documented. Its effects on the ionic currents of cardiac myocytes and the influence on the electrophysiological properties of the conduction system in Langendorff perfused hearts were investigated. 2. Ionic currents were studied by voltage clamp in the whole cell configuration. N-allylsecoboldine blocked the Na channel with a leftward-shift of its half voltage-dependent inactivation and a slower rate of recovery from the inactivation state. Similarly, calcium inward currents were inhibited but to a much smaller extent. 3. N-allylsecoboldine inhibited the 4-AP-sensitive transient outward K current. Currents through the K1 channels were also reduced. 4. As compared with quinidine, N-allylsecoboldine caused a comparable degree of block on Na and K1 currents but blocked to a lesser extent the Ca and Ito currents. 5. In the perfused whole-heart model, N-allylsecoboldine caused a dose-dependent prolongation in sinoatrial, atrioventricular and His-Purkinje system conduction intervals and prolonged the effective refractory periods of the atrium, AV node, His-Purkinje system and ventricle. However, the basic cycle length was not significantly affected. As compared to quinidine, N-allylsecoboldine exerted less pronounced effects on both the basic cycle length and the atrial and AV nodal refractory periods. 6. We conclude that N-allylsecoboldine predominantly blocks Na and K1 channels and in similar concentrations partly blocks Ca channels and Ito. These effects result in a modification of the electrophysiological properties of the conduction system which provides a satisfactory therapeutic potential for the treatment of cardiac arrhythmias.

Animals↗
PubMed1994

Probability of supraventricular tachycardia recurrence in pediatric patients.

Supraventricular tachycardia (SVT) in pediatric patients is usually associated with a better prognosis than that in adults. However, late recurrence of SVT has been recently described. A total of 90 patients who had their initial SVT episode before 15 years of age were retrospectively studied (2-228 follow-up months; median, 215 months). Concomitantly congestive heart failure was present in 14 (16%) patients, and a cerebrovascular accident occurred in 1 patient. Intravenous verapamil was most frequently used to convert the initial SVT episodes without adverse effects, even in those younger than 1 year of age (9 patients). Older children could also be converted spontaneously or by vagal maneuvers. Patients with SVT recurrence were associated with an older age at initial SVT episodes (p < 0.001). By Kaplan-Meier actuarial analysis, the chance of remaining SVT-free during the follow-up was much lower in patients with initial SVT after 5 years of age than in patients with initial attacks before the age of 1 and between the age of 1 and 5 (p = 0.02 and 0.04, respectively). Even though, about 40% of the patients whose initial attacks occurred during infancy had recurrences 5 years later. Only those who had the initial attacks during the prenatal period remained free from SVT recurrences. Patients with initial SVT episodes during infancy have a longer period without SVT attacks and a lower chance of recurrences; nonetheless, a substantial number of them had recurrence at later childhood except those with initial SVT attacks during the prenatal period.(ABSTRACT TRUNCATED AT 250 WORDS)

Actuarial Analysis↗
PubMed1994

Surgical ablation of Wolff-Parkinson-White syndrome in children and young adults.

From 1988 to 1991, nine patients with structural normal heart, aged 10 to 23 (median 13 years), Wolff-Parkinson-White Syndrome patients were operated at National Taiwan University Hospital. The diagnosis was established by surface electrocardiograms recorded during sinus rhythm and tachycardia, and by complete cardiac electrophysiologic studies. The location of accessory pathways (AP) were: 4 left lateral, 3 right lateral, 1 right posteroseptal and 1 right anteroseptal AV groove. In all 6 patients with manifest WPW syndrome, the location of AP could be correctly predicted by the surface EKG delta wave polarity. In all 9 patients with WPW syndrome, intraoperative epicardial and endocardial mappings confirmed their location. Wide endocardial dissection were undertaken. No surgical morbidities or mortality was encountered except in one case which developed transient postpericardiotomy syndrome. During the follow-up (2 to 4 years), all of them were in sinus rhythm, drug free and tachycardia free. In conclusion, (a) the sites of AP and the arrhythmia mechanisms can be reliably predicted by surface EKG and catheter mapping techniques; (b) surgical cure of supraventricular tachycardia could be achieved safely in children; and (c) surgical ablation still is indicated when catheter ablation is unsuccessful, or when coexistent complex cardiac pathology requires surgical intervention in small children.

Adolescent↗
PubMed1993

Obstructed total anomalous pulmonary venous connection.

With the advent of echocardiography, total anomalous pulmonary venous connection (TAPVC) can be readily diagnosed without much difficulty. However, noninvasive detection of the presence of pulmonary venous obstruction in TAPVC remains a difficult issue. During a 5.5-year period, 42 patients were found to have TAPVC by catheterization, surgery, and/or autopsy: 17 had supracardiac drainage, 13 paracardiac drainage, nine infracardiac drainage, and three mixed drainage. Obstruction to pulmonary venous drainage was found in 24 patients (57%). Patients with right isomerism tended to have a higher incidence of pulmonary venous obstruction than those with the usual atrial arrangement (80% vs. 44%, p < 0.05). Color Doppler combined with cross-sectional echocardiography provided accurate delineation of drainage sites in 93% cases (39 of 42). Among the 39 cases with correct echocardiographic delineation of the drainage site, obstruction was detected by echocardiography in 22 cases with a sensitivity of 100% (22 of 22) and a specificity of 85% (17 of 20). Therefore, complete echocardiography, including cross-sectional images and color Doppler proved to be a reliable tool in the detection of drainage sites and pulmonary venous obstruction in TAPVC.

Cardiac Catheterization↗
PubMed1993

Cardiovascular stability with rapid intravenous infusion of ondansetron.

The acute cardiovascular effects of rapid iv administration of the antiemetic ondansetron, a selective serotonin (5-HT3) receptor antagonist were determined in a randomized, blinded, placebo-controlled study. Measurements of heart rate, blood pressure, oxygen saturation and respiratory rate were made preoperatively over a five-minute period which followed a two-minute infusion of the medication. Intraoperative and postoperative data were not collected. None of the variables recorded changed significantly during the infusion or in the observation period which followed. Within the limitations of this study, we detected no cardiovascular change in the five minutes between the end of the drug infusion and the induction of anaesthesia.

Adult↗
PubMed1993

Unregulated self-medication in an ambulatory surgery population.

The objective of this study was to determine whether unregulated self-medication in an ambulatory surgery population was a significant problem in terms of the incidence and nature of drugs detected. We asked 67 consecutive patients who presented for elective ambulatory surgery at a university medical center to volunteer for serum and urine testing with the assurance of confidentiality. All patients denied nonprescription drug use. Initial testing was for amphetamines, barbiturates, benzodiazepines, cocaine, opiates, phencyclidine (PCP), tetrahydrocannabinol (THC) and alcohol. Of the 64 patients who agreed to be tested, 16 patients tested positive for at least one of the above substances; 4 patients demonstrated residua of 2 or 3 substances. No distinctive characteristic of those with evidence of drug use could be identified. We believe that the 25% of patients who tested positive in this group is a conservative estimate of possible unrecognized drug use. We have demonstrated a significant incidence of substance abuse in the ambulatory surgery environment. These findings have serious safety implications, and a higher awareness of possible nonprescription drug use in this environment is needed in medical and support personnel.

Adult↗
PubMed1992

Infantile cardiac hemangioendothelioma.

A 4-month-old infant with cardiac hemangioendothelioma presented with thrombocytopenia, and pericardial effusion, as well as signs and symptoms of heart failure. This is the first reported case of infantile cardiac hemangioma successfully treated with steroids.

Heart Atria↗
PubMed1992

Role of Pseudomonas aeruginosa outer membrane protein OprH in polymyxin and gentamicin resistance: isolation of an OprH-deficient mutant by gene replacement techniques.

The cloned oprH gene of Pseudomonas aeruginosa was mutated by inserting a 1.4-kbp fragment that encodes tetracycline resistance. This mutated gene was then incorporated into the P. aeruginosa chromosome by homologous recombination. Growth of the resultant oprH::tet mutant in Mg(2+)-deficient medium had little effect on susceptibility to polymyxin B, gentamicin, or EDTA unless the mutant was complemented by the cloned oprH gene in plasmid pGB25. In contrast, growth of the parent strain on Mg(2+)-deficient medium resulted in resistance to all three agents. These data support the hypothesis that overexpression of OprH under Mg(2+)-deficient growth conditions is conditionally required for resistance to these three agents.

Bacterial Outer Membrane Proteins↗
PubMed1992

Total cavopulmonary connection for surgical treatment of complex congenital heart disease.

Diversion of vena caval flow directly into the pulmonary circulation--total cavopulmonary connection--has been tried at our hospital for two years as an alternative to the modified Fontan procedure for surgical treatment of complex congenital heart disease other than tricuspid atresia in 26 cases with six operative mortalities. The causes of death were low cardiac output in four, uncontrollable paroxysmal supraventricular tachycardia in one and airway obstruction in one. Except for one late death which occurred three months after surgery due to sepsis, the 19 patients who survived the operation were followed up for four to 27 months (mean 15 months). All of them improved clinically (NYHA Class 1). Graded bicycle exercise tests were performed in five of them at three to 12 months after surgery, and their exercise tolerance was comparable to that of patients with an atriopulmonary connection. In conclusion, total cavopulmonary connection is an acceptable alternative to the modified Fontan operation for surgical treatment of complex congenital heart disease, although longer follow-up is necessary.

Adolescent↗
PubMed1992

Efficacy of balloon valvuloplasty in treating mild pulmonary stenosis.

Balloon pulmonary valvuloplasty (BPV) is a well accepted treatment for moderate and severe pulmonary stenosis. However, the efficacy of BPV in treating mild pulmonary stenosis is still unanswered. Therefore, the efficacy of BPV in treating patients with mild pulmonary stenosis was compared to that in treating patients with moderate or severe pulmonary stenosis. A total of 46 patients with pulmonary stenosis were arbitrarily divided into 3 groups; Group I consisted of 9 patients with a pressure gradient less than 40 mm Hg, Group II consisted of 5 patients with a pressure gradient ranged from 40 to 50 mm Hg, and Group III consisted of 32 patients with a gradient greater than 50 mm Hg. Following BPV, the gradient reduced significantly in all 3 groups (p less than 0.05 in each group). The efficacy of BPV in the 3 groups was evaluated and compared by two parameters; one is the percentage of gradient reduction, the other is the right ventricular pressure ratio (RV post-bpv/RV pre-bpv). The percentage of gradient reduction in Group I, II, and III were 28 +/- 20, 55 +/- 17 and 70 +/- 9% respectively. The right ventricular pressure remained 84 +/- 11, 59 +/- 16, and 46 +/- 12% of pre-valvuloplasty level in Group I, II and III respectively. If the efficacy of BPV was compared among the 3 groups. Groups III had the best efficacy and Group I had the worst.(ABSTRACT TRUNCATED AT 250 WORDS)

Catheterization↗
PubMed1992

The utility of preoperative electrocardiograms in the ambulatory surgical patient.

To determine the utility of preoperative screening electrocardiograms (ECGs) among ambulatory surgery patients, we reviewed the charts of 751 consecutive adult patients who underwent ambulatory surgery. Data were collected on demographic characteristics, coexisting medical problems, American Society of Anesthesiologists physical status score, preoperative ECG results, adverse intraoperative cardiovascular events, and postoperative cardiovascular complications. In our study population of relatively healthy outpatients, preoperative ECGs were abnormal in 42.7% of patients. Age, increased physical status score, and male gender were associated with a greater incidence of abnormal preoperative ECGs. There were 12 adverse cardiovascular perioperative events among the 751 patients (1.6%), and the preoperative ECG may have been clinically useful in six of these 12 patients. Neither preoperative ECGs nor results of preoperative screening questionnaires were predictive of adverse cardiovascular perioperative events. These findings question the utility of preoperative ECGs in the ambulatory surgery setting, especially among younger, relatively healthy patients.

Adolescent↗
PubMed1991

Junctional ectopic tachycardia in infancy: report of two cases.

Junctional ectopic tachycardia (JET) in infancy is one of the serious arrhythmias which can be fatal. Typical features of JET include rapid and irregular heart beats with atrioventricular dissociation. Two cases of JET are reported: Case 1 was a 35-week-gestational age newborn who was found to have hydropsy and fetal tachycardia at the 21st week of gestational age. Antiarrhythmic agents including digoxin, propranolol and verapamil were administered to his mother to treat the fetal arrhythmia without success. JET was recognized at birth which was spontaneously converted into a sinus rhythm at 1 month of age. The maternal history revealed that two previous pregnancies ended in hydrops fetalis, and one of these was documented to have fetal tachycardia. Case 2 was a 6-month-old male infant with JET and congestive heart failure. After failure of various antiarrhythmic agents, amiodarone finally slowed down his heart rate and controlled his congestive heart failure.

Anti-Arrhythmia Agents↗
PubMed1990

Emotional responses of athletes to injury.

Increased participation in sports is associated with increased related injuries. This study was conducted to identify the emotional responses of athletes to injury and to determine which responses might interfere with rehabilitation and necessitate psychologic or psychiatric intervention. In 72 patients, follow-up surveillance was continued from the time of injury until resumption of sports activity. Patients completed the Emotional Responses of Athletes to Injury Questionnaire and the Profile of Mood States (POMS) test, and significant differences were found when the POMS scales of depression and anger were compared with college norms. Mean POMS scores were compared (by multivariate analysis of variance) by sex, age, and severity of injury. No gender differences were found, and only for anger were age groups significantly different (younger athletes were most angered). Three severity-of-injury groups (based on the duration of time the athlete was unable to participate in sports) were also compared. The most seriously injured group experienced significantly more tension, depression, and anger and less vigor than college norms, a mood disturbance that lasted 1 month. Emotional disturbance can occur after a sports-related injury, and its prompt recognition may facilitate the athlete's optimal rehabilitation and a safe return to participation in sports.

Adolescent↗