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Biomedical subjects

J M Dunn

Publications and source records attributed to J M Dunn.

At least 55 records · Page 3Linked to original sources
PubMed1988

Ectopic automatic atrial tachycardia in children: clinical characteristics, management and follow-up.

Ectopic automatic atrial tachycardia, an uncommon type of supraventricular tachycardia in children and adults, has been reported to be resistant to medical therapy, and surgical or cryoblation has been recommended. This report describes 10 infants and children (median age 6 months; range birth to 7.5 years) with automatic atrial tachycardia and their management and follow-up. Digoxin alone was unsuccessful in controlling tachycardia in all 10 patients but decreased the tachycardia rate by 5 to 20% in 8. Intravenous (0.1 mg/kg body weight per dose) and oral propranolol successfully suppressed tachycardia in three of five patients and oral propranolol successfully controlled tachycardia in two of five other patients. Class I antiarrhythmic agents--quinidine (three patients), procainamide (four patients) and phenytoin (three patients)--did not control tachycardia in any patients but made the tachycardia rate worse in three patients. Intravenous (5 mg/kg per dose) and oral amiodarone suppressed tachycardia in three of four patients and oral amiodarone suppressed it in another patient. Thus, intravenous propranolol and amiodarone were effective in acutely suppressing automatic ectopic atrial tachycardia and predicted the response to long-term oral therapy. One patient had persistent tachycardia after surgical ablation of the high right atrial ectopic focus, and another patient had unsuccessful catheter ablation of the high right atrial ectopic focus (25 J). During follow-up (10 to 28 months), ectopic atrial tachycardia resolved completely in four patients and was well controlled in four patients.

Administration, Oral↗
PubMed1988

A rat brain Na+ channel alpha subunit with novel gating properties.

We have constructed a full-length rat brain Na+ channel alpha subunit cDNA that differs from the previously reported alpha subunit of Noda et al. at 6 amino acid positions. Transcription of the cDNA in vitro and injection into Xenopus oocytes resulted in the synthesis of functional Na+ channels. Although the single-channel conductance of the channels resulting from cloned cDNA was the same as that of channels resulting from injection of rat brain RNA, we observed two significant differences in the gating properties of the channels. The Na+ currents from cloned cDNA displayed much slower macroscopic inactivation compared with those from rat brain mRNA. In addition, the current-voltage relationship for currents from cloned cDNA was shifted 20-25 mV in the depolarizing direction compared with currents from rat brain RNA. Coinjection of low MW rat brain RNA restored normal inactivation of the channels indicating the presence of a component, either a structural subunit of the channel complex or a modifying enzyme, necessary for normal gating of the channel.

Amino Acid Sequence↗
PubMed1988

Tocainide: a severe adverse reaction.

Tocainide is a primary analog of lidocaine with antiarrhythmic properties used to treat ventricular rhythm disorders. A 76-year-old man with benign paroxysmal premature ventricular contractions was treated with tocainide and developed a generalized maculopapular lupoid eruption, bleeding from the lips and gingivae, vertigo, gross tremors of the extremities, fever, and short-term memory loss, which required hospitalization. The patient recovered slowly over three months with no permanent sequelae after discontinuing the drug and receiving rigorous supportive care. His excellent physical status and absence of concomitant illness contributed to an uneventful recovery. Tocainide is a potent cardioactive drug with a long biological half-life and should be used with caution.

Aged↗
PubMed1987

Evaluation of changes in cytoplasmic pH in thrombin-stimulated human platelets.

Thrombin causes a dose-dependent cytoplasmic alkalinization of normal human platelets. The pH probe 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) permits an easier and more accurate quantitation of the kinetics of this change previously measured with 9-aminoacridine and 6-carboxyfluorescein (6-CF). We report here a modification of the previously published 6-CF technique and confirm the thrombin-induced cytoplasmic pH change in the human platelet using a second fluorescein derivative, BCECF. Maximal thrombin stimulation raises the resting cytoplasmic pH of the human platelet from 7.0 to 7.25.

Blood Platelets↗
PubMed1987

Oncocytic cardiomyopathy of infancy with Wolff-Parkinson-White syndrome and ectopic foci causing tachydysrhythmias in children.

Two female infants, ages 6 months and 13 months, were first seen in the newborn period with supraventricular tachycardia associated with Wolff-Parkinson-White syndrome. One infant had echocardiographic and angiographic evidence of diffuse cardiomyopathy and died suddenly at home. The other infant was seen initially at 13 months of age with refractory ventricular tachycardia and died following surgical resection of arrhythmogenic foci on the left and right ventricles. Autopsy showed diffuse patchy oncocytic cardiomyopathy in both instances. Serial histologic sections of the cardiac conduction system showed oncocytic involvement of the atrioventricular (AV) node, His bundle, and bundle branches. Both infants had interruption of the anulus fibrosus by oncocytic cells at several sites, resulting in multiple accessory AV and nodoventricular connections. Additionally, patient No. 1 had an accessory AV connection by oncocytic cells in the fatty fibrous tissue of the left AV sulcus. To our knowledge, this is the first report of multiple accessory AV connections of oncocytic cells seen during histologic study. In addition, both infants had oncocytic involvement of the exocrine and endocrine glands. This report discusses the clinicopathologic correlations in these two patients, the literature on oncocytic cardiomyopathy, and the types of dysrhythmias found in these patients and their management.

Cardiomyopathies↗
PubMed1987

The inframammary incision for median sternotomy in pediatrics.

Median sternotomy offers the ideal exposure for most cardiac and mediastinal procedures. One infrequently mentioned morbidity of the traditional median sternotomy is the unsightly scar, especially in pediatric and adolescent patients who are extremely sensitive about their body appearance. We report our experience using a bilateral inframammary "butterfly" incision on 31 patients in association with a median sternotomy to provide excellent exposure and an improved cosmetic result.

Breast↗
PubMed1987

Local wound care in the diabetic.

Since wounds in patients with diabetes will heal slowly at best, and since they are so much more susceptible to infection and the infection will be more devastating, the old adage of "first do no harm" must be adhered to. Diabetics have poor circulation, poor resistance to infection, and poor local nutrition. Their white blood cell killing power is decreased by the hypoxia from poor circulation and by the periodic hyperglycemia. The periodic hypoglycemia and decreased insulin interferes with the energy for healing and for host defenses. Because of this poor healing and low resistance, the use of strong, toxic chemicals should be avoided. They all inhibit healing and/or increase the risk of infection. Vigorous, repeated debridement of necrotic, devitalized tissue along with old blood, exudates, and tissue fluids is essential. This includes sharp debridement and mechanical debridement through high-pressure irrigation and frequent wet to dry fine mesh gauze dressings. The choice of bandaging material should be determined by the desired action on the wound, such as protection, debridement, and so on. The idea is to restore the conditions in the wound to normal physiology.

Asepsis↗
PubMed1986

Recurrent obstruction after subclavian flap repair of coarctation of the aorta in infants. Can it be predicted or prevented?

Recoarctation is a problem in some patients after subclavian flap aortoplasty. To investigate the reason for recoarctation, we reviewed the records of 26 infants who underwent subclavian flap repair for symptomatic coarctation of the aorta at less than 3 months of age between June, 1979, and December, 1983. Age at repair ranged from 2 to 65 days (median 16 days) and weight from 2.1 to 4.9 kg (median 3.4 kg). In 14 patients the coarctation was associated with significant intracardiac defects (complex in six). There were two intraoperative deaths and one early death (surgical mortality 12%). The survivors were followed from 6 weeks to 66 months (median 12 months). Five survivors (22%), all operated on at less than 14 days of age, developed severe recoarctation 6 weeks to 6 months (median 5 months) after repair. The obstruction appeared to be due to lumen obliteration by shelf-life posterior wall tissue. Morphometric analysis of preoperative angiograms showed no correlation between recoarctation and distance between the left subclavian artery and the site of coarctation, length of the isthmus, diameter of the isthmus, combined cross-sectional area of the left subclavian artery and isthmus, or the ratio of the combined cross-sectional area of the left subclavian artery and isthmus to the cross-sectional area of the descending thoracic aorta. Recoarctation did not correlate with weight at operation, but it correlated significantly with age at aortoplasty (p = 0.02). The results suggest that intrinsic abnormalities of the periductal aortic wall are responsible for recoarctation after subclavian flap aortoplasty. Particular attention to this abnormal tissue at repair may prevent early recurrence in young infants.

Age Factors↗
PubMed1986

Bioavailability of indomethacin tablets in men volunteers.

Indomethacin bioavailability was compared in 22 healthy men who received two tablet dosage formulations and a capsule formulation of indomethacin in a three-way crossover study. In each study period, 50 mg of the indomethacin formulation (25-mg or 50-mg tablets or 50-mg capsules) was administered as a single dose to fasting subjects. Thirteen blood samples were collected at intervals over 24 hours after each dose. Urine samples were collected for 12 hours before each dose and 48 hours after each dose. Serum indomethacin concentrations were measured by a gas chromatographic procedure. The extent of indomethacin absorption for the two tablet formulations was not significantly different from that for the reference capsule. A trend toward earlier and higher peak serum concentrations with the capsule was observed. There was less than 20% difference in mean values for area under the concentration-time curve (AUC) for the three formulations. More than 75% of the subjects had serum concentrations falling between 75 and 125% of the mean serum concentrations. The extent of absorption of indomethacin from the two tablet formulations was similar to that from the capsule.

Administration, Oral↗
PubMed1985

Aneurysm of main pulmonary artery in a neonate with airway obstruction and heart failure: long-term survival after pulmonary artery aneurysmectomy and patent ductus arteriosus ligation.

A neonate was seen with complete atelectasis of the left lung secondary to compression of the left main bronchus by a congenital aneurysmal main pulmonary artery. Operation consisted of pulmonary artery aneurysmectomy and ligation of an associated patent ductus arteriosus. Follow-up (3 years after operation) demonstrated complete resolution of the atelectasis and congestive heart failure.

Airway Obstruction↗
PubMed1985

Evaluation of absorbable polyglycolic acid mesh as a wound support.

The ideal wound-support material would reinforce a wound early in the healing process when intrinsic wound strength is the weakest, yet disappear over time, preventing many of the untoward late effects seen with currently utilized nonabsorbable materials. This study was designed to evaluate the effectiveness of a newly designed absorbable material, polyglycolic acid mesh (Dexon), as a buttress for abdominal wounds closed under moderate tension. Young male rats (n = 211) were divided into three experimental groups. Animals in groups 1 (n = 96) and 2 (n = 95) had a 1.2 cm2 midline abdominal wall defect created and closely primarily. Animals in group 2 had a 2 X 5 cm piece of polyglycolic acid mesh sutured to the anterior abdominal wall overlying the closed abdominal defect. Animals in group 3 (n = 20) were unoperated controls. The animals in groups 1 and 2 were killed 1, 2, 3, 4, and 5 weeks after surgery. The entire anterior abdominal wall was removed and placed upon a bursting strength testing device. Bursting strength determinations of the supported and unsupported abdominal closures revealed that the strength of the wounds reinforced with polyglycolic acid mesh was significantly greater than unsupported wounds at 1, 2, and 3 weeks after surgery. Wounds supported with mesh had bursting strengths similar to unoperated abdomens by the first postoperative week. This study demonstrates that abdominal wall defects in rats closed primarily develop increased wound strength when the closure is supported by absorbable polyglycolic acid mesh. The use of an absorbable material may alleviate potential late complications associated with implantation of nonabsorbable materials. The clinical application of such a material remains to be determined.

Abdominal Muscles↗
PubMed1985

Morphological observations of mineralizing pericardium cardiac grafts.

Pericardial patch grafts were implanted in the hearts of young sheep for periods ranging from two to 120 days. Explants seven to 21 days old revealed the formation of a "pseudoneointima" (PNI) on the blood contacting surface of the pericardium. The PNI was more heavily mineralized than the pericardium. Mineralization was most intense on the blood contacting surface of the PNI and on the chamber surface of the pericardium. After three weeks of implantation, the PNI was much thinner and was organized into a thin fibrous capsule without any signs of mineralization. In the pericardium, mineral deposits were seen in fibroblasts. Moreover, cell-related mineralization was evident prior to calcification of the surrounding collagen matrix.

Animals↗
PubMed1984

Congenital cardiac anomalies associated with the DiGeorge syndrome: a neonatal experience.

The DiGeorge syndrome is a rare congenital abnormality of absent of hypoplastic thymus and parathyroid glands. Thirty neonates who had cardiac lesions and the DiGeorge syndrome are reviewed. The early mortality for 10 neonates undergoing palliative procedures was 80%. Seventy-five percent of the deaths were secondary to sepsis. Twenty neonates did not undergo palliative procedures. In this group, early mortality was 60% and late mortality was 65%. Sixty percent of the deaths in this group were associated with sepsis, with cardiac failure responsible for the remaining deaths. Survival in both groups has improved with appropriate treatment of the immunological and metabolic consequences of the DiGeorge syndrome.

Abnormalities, Multiple↗
PubMed1984

Vascular rings and slings: long-term follow-up of pulmonary function.

Between 1968 and 1983, 54 patients underwent surgery for symptomatic aortic arch and pulmonary artery anomalies at St Christopher's Hospital for Children. Presenting symptoms included stridor, wheeze, apnea, recurrent pulmonary infections, or dysphagia. Diagnosis was established with chest roentgenogram, bronchoscopy, barium esophagram, and arteriography. Four types of vascular anomalies were encountered; double aortic arch (24 patients), right aortic arch with left ligamentum arteriosum (17 patients), anomalous innominate artery (10 patients), and pulmonary artery sling (three patients). There were no intraoperative deaths and only one postoperative death. All surviving patients had immediate relief of their severe respiratory or swallowing symptoms. Mild respiratory symptoms persisted postoperatively from 3 months to 4 years and included frequent or severe upper respiratory infections, persistent cough, stridor and pneumonia. Five of the 53 surviving patients were lost to follow up. The remaining 48 patients were followed from 6 months to 14 years and all but one patient noted complete resolution of all respiratory symptoms. Twenty-nine patients at follow up were old enough to undergo pulmonary function testing including vital capacity, functional residual capacity, and inspiratory and expiratory flow volume loops. Seventeen of these 29 asymptomatic patients consented to these studies, and nine of these patients had abnormal flow volume loops indicative of significant central airway obstruction; the other eight studies were normal. We conclude that surgical repair for vascular rings and slings is safe and symptomatically efficacious. However, anatomic tracheal or bronchial distortion persists in a significant number of these patients as evaluated by pulmonary function studies.

Adolescent↗