Biomedical subjects
Publications and source records attributed to M L Young.
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.
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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.
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.
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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)
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.
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.
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.
By using extrastimulation technique the effective refractory period (ERP) of the atrioventricular (AV) node is conventionally defined as the longest A1A2 interval at which conduction of A2 is blocked within the node. With the prolongation of the AV nodal transit time that is associated with this technique, the delayed AV nodal arrival of the A1 impulse will cause an overestimation of the true interval if the A1A2 interval is used as the gauge. Under this condition, the conventional approach will not accurately delineate the ERP of the AV node. However, this prolongation of the nodal transit time can be calculated by subtracting the basal conduction time from the conducted A-H interval. By subtracting out the prolongation from the longest A1A2 at which A2 impulse is blocked, not only an interval more indicative of the true AV nodal ERP can be obtained, but also the apparent discrepancies between the in vitro and human AV nodal recovery curves disappear.
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We used an isolated perfused heart model to assess the effects of graded hypoxia (95, 45, 20, 10, or 0% O2, exposure for 5 min) on the adult and neonatal (0-3 days) rabbit atrioventricular (AV) node. The AV nodal function was assessed by measuring the A-H interval at a constant atrial pacing cycle length, the longest pacing cycle length resulting in Wenckebach periodicity [Wenckebach cycle length (WCL)] and the AV nodal effective refractory period (AVNERP). The A-H intervals remained stable in neonatal hearts until O2 saturation was decreased to 10%. On the other hand, the A-H intervals began to increase in adult rabbit hearts at 20% O2. In 95% O2, the AV nodal WCL was longer in adult hearts than in the neonatal hearts (165 +/- 8 ms vs. 142 +/- 7 ms). The effect of hypoxia on the AV nodal WCL was significantly greater in adult hearts than in neonatal hearts when the O2 saturation was decreased to 20% (a 54% increase in adults vs. a 14% increase in neonates, P = 0.02). The difference was greater at lower levels of O2. In 95% O2 at comparable basis driving cycle length (240 ms), the A-H intervals were equal in neonatal and adult hearts (43 +/- 3 vs. 43 +/- 7 ms), but the AVNERP of the neonates was significantly longer than that of the adults (133 +/- 21 vs. 97 +/- 19 ms, P = 0.007).(ABSTRACT TRUNCATED AT 250 WORDS)
The indirectly estimated sinoatrial conduction time has been widely used in children to assess sinus node (SN) function, but has never been validated in pediatric patients. Using a standard quadripolar catheter with high amplification and low-pass filters, SN electrograms were recorded in 11 of 26 (42%) pediatric cardiac patients (age range 10 months to 18 years) with normal SN function. The sinoatrial conduction time was measured directly from the SN electrogram and estimated indirectly by the premature stimulation and continuous pacing methods. The direct sinoatrial conduction time (15 to 91 ms) in these 11 patients (ages 1 to 18 years) correlated well with that estimated by the premature stimulation method (r = 0.81, n = 9, p less than 0.01). There was a poor correlation between the direct and continuous pacing methods (r = 0.53, n = 8, p = 0.17). It was concluded that SN electrograms can be recorded in children and that there is a good correlation between the directly measured sinoatrial conduction time and the indirectly estimated sinoatrial conduction time by the premature stimulation method.
A patient with sick sinus syndrome following the Senning operation was also found to have concealed atrial parasystole during intracardiac electrophysiological study. This atrial parasystolic pattern could be converted to atrial bigeminy by changing the atrial drive rate.
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A 12 years old boy with frequent episodes of palpitation was found, by the electrophysiologic study, to have an atrioventricular (AV) nodal tachycardia. Endocardial mapping during surgery revealed that the earliest retrograde atrial depolarization of the tachycardia occurred at the posterior part of Koch's triangle. Under normothermic cardiopulmonary bypass, perinodal dissection was performed above the tricuspid annulus at the coronary sinus region. The retrograde VA conduction disappeared. Post-surgery the antegrade conduction had a Mobitz type I block which had returned to normal after the fourth month follow-up.