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Biomedical subjects

M Dick

Publications and source records attributed to M Dick.

At least 37 records · Page 2Linked to original sources
PubMed1993

Sudden cardiac death and the use of implantable cardioverter-defibrillators in pediatric patients. The Pediatric Electrophysiology Society.

BACKGROUND: During the past decade, the implantable cardioverter-defibrillator (ICD) has emerged as the primary therapeutic option for survivors of sudden cardiac death (SCD). Investigation of the clinical efficacy of these devices has primarily assessed outcome in adults with coronary artery disease. The purpose of this cooperative, international study was to evaluate the impact of ICDs on the pediatric population of SCD survivors, based on an analysis of the clinical characteristics and outcomes of young patients who underwent ICD implantation following an episode of life-threatening ventricular tachycardia or resuscitation from SCD. METHODS AND RESULTS: An initial data base, established by contacting the manufacturers of the various commercially and investigationally available devices, identified 177 patients who were less than 20 years of age at the time of initial implantation of an ICD. With this data base as a reference, detailed responses were subsequently obtained from physicians involved in the care of 125 (71%) of these patients. The patients ranged in age from 1.9 to 19.9 years (mean, 14.5 +/- 4 years) and weighted 9.7-117 kg (mean, 44.6 +/- 14 kg). Of the 125 patients, 76% were survivors of SCD, 10% had drug refractory ventricular tachycardia, and 10% had syncope with heart disease and inducible sustained ventricular tachyarrhythmias. The most common types of associated cardiovascular disease were hypertrophic and dilated cardiomyopathies (54%), primary electrical diseases (26%), and congenital heart defects (18%). Ventricular function was abnormal in 46% of the patients. During a mean follow-up of 31 +/- 23 months, at least one ICD discharge occurred in 85 of the 125 (68%) patients. Seventy-three patients (59%) received at least one appropriate ICD discharge, and 25 patients (20%) had one or more spurious or indeterminate discharges. Duration of follow-up > 24 months (p = 0.001) and inducibility of a sustained ventricular arrhythmia (p = 0.05) were correlated with appropriate ICD discharges. There were nine deaths during the study period: five sudden, two due to recurrent ventricular arrhythmias, and two related to congestive heart failure. Abnormal ventricular function (p = 0.002) and prior ICD discharge (p = 0.01) were univariate correlates of patient mortality; by multivariate logistic regression, abnormal ventricular function was the only significant correlate of death (p = 0.005). By actuarial analysis, the estimated overall post-ICD implant survival rates at 1, 2, and 5 years were 95%, 93%, and 85%, respectively. The corresponding sudden death-free survival rates were 97%, 95%, and 90%. CONCLUSIONS: Pediatric patients resuscitated from SCD appear to remain at risk for recurrence of life-threatening tachyarrhythmias. During a mean follow-up of 31 months, the ICD provided an effective therapy for such arrhythmias in the majority of patients in this study. Following ICD implant, impaired ventricular function was the primary factor correlated with mortality. The patterns of ICD discharge observed in young patients and, thus, inferred risk of recurrent life threatening arrhythmias are similar to those of adult survivors of SCD. Thus, the use of ICDs in pediatric patients, with implant selection criteria similar to adults, appears valid.

Adolescent↗
PubMed1993

The long QT syndrome in children. An international study of 287 patients.

BACKGROUND: The Pediatric Electrophysiology Society studied children with the long QT syndrome (LQTS) to describe the features of LQTS in patients less than 21 years old, define potential "low-risk" and "high-risk" subpopulations, and determine optimal treatment. METHODS AND RESULTS: Patients less than 21 years old were included if either QTc was more than 0.44; they had unexplained syncope, seizures, or cardiac arrest preceded by emotion or exercise; or family history of LQTS. We found 287 patients from 26 centers in seven countries. Mean +/- SD age at presentation was 6.8 +/- 5.6; 9% presented with cardiac arrest, 26% with syncope, and 10% with seizures. Of those with symptoms, 67% had symptoms related to exercise. Family history was positive for long QT interval in 39% and for sudden death in 31%. Hearing loss was present in 4.5%. A normal QTc was present in 6%, and QTc of more than 0.60 was in 13%. Atrioventricular block occurred in 5%, but 13 of 15 patients had second-degree atrioventricular block (2:1), and only two of 287 had complete atrioventricular block. Ventricular arrhythmias were found on 16% of initial routine ECGs: 4% uniform premature ventricular contractions, 5% multiform premature ventricular contractions, 1% monomorphic ventricular tachycardia, and 6% torsade de pointes. Overall, treatment was effective for symptoms in 76% and for ventricular arrhythmias in 60%. There was no difference between propranolol and other beta-blockers in effective treatment. Left stellectomy was performed in nine patients, and defibrillators were implanted in four; no sudden death occurred in these 13 patients. In follow-up (duration, 5.0 +/- 4 years; age, 10.9 +/- 6.3 years), 5% had cardiac arrest, 4% had syncope, and 1% had seizures. The two multivariate predictors of symptoms at follow-up were symptoms at presentation and propranolol failure. Sudden death occurred in 8%; multivariate predictors of sudden death were length of QTc at presentation of more than 0.60 and medication noncompliance. CONCLUSIONS: The appearance of 2:1 atrioventricular block, multiform premature ventricular contractions, and torsade de pointes are relatively more common in children with LQTS than other children and should raise the index of suspicion for LQTS. Because 9% of patients presented with cardiac arrest and no preceding symptoms, perhaps prophylactic treatment in asymptomatic children is indicated. Asymptomatic patients with normal QTc and positive family history may be a low-risk group. Patients with QTc of more than 0.60 are at particularly high risk for sudden death, and if treatment is not effective, consideration should be given to cardiac sympathetic denervation, pacemaker implantation, and perhaps implantation of a defibrillator.

Adrenergic beta-Antagonists↗
PubMed1993

The management of severe subaortic stenosis, ventricular septal defect, and aortic arch obstruction in the neonate.

Neonates with ventricular septal defect and aortic arch obstruction frequently have subaortic stenosis resulting from posterior deviation of the infundibular septum. Because the aortic anulus is often hypoplastic, making direct resection of the infundibular septum through the standard transaortic approach difficult, the optimal method of repair is uncertain. From September 1989 through November 1991, seven patients with ventricular septal defect, coarctation (n = 4), or interrupted aortic arch (n = 3) and severe subaortic stenosis underwent repair with use of a technique that included transatrial resection of the infundibular septum. Their ages ranged from 5 to 63 days (median 15 days) and weights from 1.3 to 5.4 kg (mean 3.1 kg). Only one patient was older than 1 month. The systolic and diastolic ratios of the diameter of the left ventricular outflow tract to that of the descending aorta were 0.53 +/- 0.09 mm (standard deviation) and 0.73 +/- 0.11, respectively. At operation, the posteriorly displaced infundibular septum was partially removed through a right atrial approach by resecting the superior margin of the ventricular septal defect up to the aortic anulus. The resulting enlarged ventricular septal defect was then closed with a patch to widen the subaortic area. In each patient the aortic arch was repaired by direct anastomosis. All patients survived operation; there was one late death from noncardiac causes 3 months after repair. The survivors remain well from 3 to 14 months after repair (mean 8 months). All are in sinus rhythm and none has a residual ventricular septal defect. One patient underwent successful balloon dilation of a residual aortic arch gradient late after repair. No patient has significant residual subaortic stenosis, although one has valvular aortic stenosis. This series suggests that in neonates with ventricular septal defect and severe subaortic stenosis resulting from posterior deviation of the infundibular septum, direct relief can be satisfactorily accomplished from a right atrial approach. This method provides effective widening of the left ventricular outflow tract and is superior to palliative techniques or conduit procedures.

Aortic Arch Syndromes↗
PubMed1992

Decreased levels of soluble amyloid beta-protein precursor in cerebrospinal fluid of live Alzheimer disease patients.

The amyloid beta-protein is deposited in senile plaques and the cerebrovasculature in Alzheimer disease (AD). Since it is derived from proteolytic processing of its parent protein, the amyloid beta-protein precursor (APP), we investigated whether levels of the secreted forms of APP are altered in cerebrospinal fluid (CSF) of AD patients. Quantitative immunoblotting studies with the anti-APP monoclonal antibody P2-1 revealed that probable AD patients had markedly lower CSF APP levels than did demented non-Alzheimer-type patients and healthy control subjects. Using antibody P2-1 in an enzyme-linked immunosorbent assay, we measured CSF levels of APP in a larger population consisting of 13 patients diagnosed with probable AD, 18 patients diagnosed with dementia (non-Alzheimer type), and 16 nondemented, healthy controls. Mean CSF levels of APP were approximately 3.5-fold lower in the live patients diagnosed with probable AD compared to the demented non-Alzheimer-type controls or the nondemented, healthy individuals. These findings suggest that abnormal metabolism of APP is reflected in the extracellular fluids of the central nervous system and that CSF levels of soluble APP provide a useful biochemical marker to assist in the clinical diagnosis of AD.

Alzheimer Disease↗
PubMed1992

Congenital muscular dystrophy presenting with respiratory failure.

Respiratory failure is an unusual initial manifestation of congenital muscular dystrophy. The authors describe a case of congenital muscular dystrophy in a patient presenting with rhabdomyolysis at birth. Despite an initially poor prognosis, aggressive respiratory therapy during the neonatal period permitted normal subsequent development. The muscular dystrophy predominantly involved the respiratory muscles.

Biopsy↗
PubMed1992

Intermediate-term survival and functional results after arterial repair for transposition of the great arteries.

An assessment of late morbidity and mortality is essential before arterial repair can be considered truly corrective for patients with transposition of the great arteries. We describe the early and intermediate-term results in 126 patients who underwent arterial repair. Operation was performed at a median age of 6 days, with 76 patients operated on within the first 7 days of life. Coronary artery anatomy differed from the usual arrangement in 37 patients. Simultaneous procedures included ventricular septal defect closure (35) and repair of interrupted aortic arch (2) or coarctation (5). Hospital mortality was seven of 126 (5.5%), with three deaths among the most recent 100 patients (3%). There were one late, noncardiac death and one late death after reoperation. Reoperation for pulmonary artery stenosis was required in 10 of the first 63 patients (16%), all of whom underwent pulmonary artery reconstruction with separate patches for closure of the coronary excision sites. Of the last 63 patients, all of whom underwent pulmonary artery reconstruction with a single pantaloon-shaped pericardial patch, one (2%) required reoperation for pulmonary artery stenosis. Doppler flow studies and echocardiography performed in 115 of 119 surviving patients at a mean of 12 months after repair demonstrated normal left ventricular function, minimal left ventricular outflow gradients, and no more than trivial aortic regurgitation. Peak gradient across the right ventricular outflow tract was 19 +/- 3 mm Hg in patients with separate pulmonary artery patches and 5 +/- 2 mm Hg in those with a single pantaloon patch (p = 0.0001). Follow-up is 96% complete from 1 month to 8 years after operation (mean 2.5 years). The actuarial survival rate at 5 years, including operative mortality, was 92%. All patients are in sinus rhythm, and none requires antiarrhythmic medications. These data suggest that pulmonary artery reconstruction with a single pantaloon patch may be associated with a decreased requirement for reoperation. Intermediate-term survival and functional results are excellent after arterial repair for transposition of the great arteries.

Actuarial Analysis↗
PubMed1991

Homeoboxes in cnidarians.

Homeoboxes have previously been documented from various phyla of triploblastic, coelomate and pseudocoelomate, animals. We report here the first homeoboxes from cnidarians, a phylum of diploblastic organisms thought to occupy a near-basal position in metazoan phylogeny. We have sequenced three partial (77 bp) fragments of Antennapedia (Antp) class homeoboxes from the hydroids Hydractinia symbiolongicarpus and Eleutheria dichotoma. A pair of fragments, Cnox-2-Hs and Cnox-2-Ed, from the two species differ in nucleotide sequences but have identical derived amino acid sequences. A gene tree produced by parsimony analysis shows that these two fragments cluster within the Antp homeobox lineage. The third fragment, Cnox-1, clusters as a sister group of the other Antp class homeoboxes.

Amino Acid Sequence↗
PubMed1991

Current treatment for Wolff-Parkinson-White syndrome: results and surgical implications.

From July 1986 to January 1991, 123 patients with Wolff-Parkinson-White syndrome underwent operation for ablation of aberrant conduction pathways. There were 85 male and 38 female patients ranging in age from 11 months to 68 years. Associated anomalies included Ebstein's anomaly, sudden death syndrome, coronary artery disease, cardiomyopathy, abdominal aortic aneurysm, neurofibromatosis, other arrhythmias, or other complex congenital heart disease. Forty-one patients had multiple accessory pathways. Operative results showed a 7% initial failure rate, which dropped to 3% after reoperation. One patient had undergone previous operation for Wolff-Parkinson-White syndrome at another institution. Procedures performed concomitantly included mitral or tricuspid valve repair or replacement (6), right ventricular conduit replacement, subaortic resection, Fontan repair, corrected transposition repair, coronary artery bypass, and placement of an automatic internal cardioverter defibrillator. There was no operative mortality. Late follow-up is 27 +/- 16 months, and complications included mitral regurgitation and myocardial infarction. By comparison, in the last 12 months 124 patients with the Wolff-Parkinson-White syndrome underwent catheter ablation using radiofrequency current. There were 9 patients with multiple pathways. One hundred twelve patients (90%) had all accessory atrioventricular connections ablated and have remained free of symptomatic tachycardia. There have been 12 failures (10%), of which 5 have had operation and 7 are being treated medically. Mean follow-up is 7 +/- 5 months, and complications included circumflex coronary artery occlusion, excessive bleeding, valve perforation, and cerebral vascular accident.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Short- and long-range processes in structure-from-motion.

Human ability to detect 3-D structure in an array of 2-D moving dots was tested. Under limited exposure time, we found high detection rates only when the 2-D motion was restricted to the spatio-temporal region of short-range motion. Long-range moving dots failed to produce a strong impression of 3-D structure and yielded only weak detection rates. This result is consistent with the view that the processing of long-range motion is more serial than that of short-range motion.

Depth Perception↗
PubMed1991

Natural history of isolated atrial flutter in infancy.

To clarify the natural history of isolated (i.e., without associated congenital cardiac anomalies) atrial flutter in infancy, we reviewed the clinical course in nine patients who were seen with this arrhythmia in the first year of life (range 1 day to 4 months). Atrial flutter was identified by the typical sawtooth pattern in leads II, III, and aVF of the surface electrocardiogram or the pattern of atrial flutter on an atrial electrogram recorded through the esophagus. The mean cycle length of the atrial flutter was 151 msec (atrial rate 397 beats/min). Six of the nine patients had other perinatal problems, such as immune and nonimmune hydrops fetalis (two patients), pneumonia (one patient), anemia (five patients), or low birth weight (one patient). In all patients the rhythm reverted to normal, either spontaneously (two patients), with overdrive pacing (four patients), or after oral digoxin therapy (three patients). No consistent temporal relationship between digoxin administration and conversion was observed; conversion was instantaneous in the four patients who received atrial overdrive pacing. Four patients were discharged receiving digoxin therapy (6 months to 1 year). One patient had supraventricular tachycardia after discharge that was controlled with digoxin. No recurrence of atrial flutter was observed among the nine patients during a mean follow-up of 6.8 years (range 0.2 to 20 years). We conclude that isolated atrial flutter in infancy is rare, has a good prognosis, may be related to transient perinatal events, and often spontaneously converts to normal sinus rhythm; however, when it does not, it will respond to transesophageal pacing. Acute and chronic digoxin therapy is probably unnecessary.

Apgar Score↗
PubMed1991

Use of radiofrequency current to ablate accessory connections in children.

BACKGROUND: Several investigators have recently ablated electrophysiologically mapped accessory connections in the adult human myocardium by using radiofrequency current. To examine the effectiveness and safety of radiofrequency current for ablation of accessory connections in children, 20 consecutive patients (age, 3-18 years) with preexcitation and/or supraventricular tachycardia were evaluated by electrophysiological study. METHODS AND RESULTS: Nineteen of the 20 patients were completely studied and demonstrated accessory connections. After identification of the earliest retrograde atrial activation site, a steerable 7F catheter (with a 4-mm-long electrode at the distal tip) was placed within the ventricular cavity ipsilateral to the accessory connection and positioned at the atrioventricular valve annulus directly opposite the earliest point of retrograde atrial activation. Radiofrequency current was delivered at 50-65 volts for 10-60 seconds at a frequency of 500 kHz. Radiofrequency pulses were delivered for two to 26 trials. Upon completion of radiofrequency trials, repeat electrophysiological testing was performed. Thirteen of 19 subjects (68%) experienced definite successful ablation of their accessory pathway; an additional patient had probable successful ablation, yielding an overall success rate of 74%. Eighty-seven percent of individuals with a left-sided pathway had permanent ablation and 100% with a manifest left-sided pathway experienced successful ablation. Only 29% of the first seven patients had a successful result; in contrast, 92% of the next 12 patients had successful interruption of their accessory pathways. After ablation, 4-day continuous electrocardiographic telemetry disclosed no significant arrhythmias. CPK enzyme rises peaked at 12-24 hours. The rise was excessive and associated with general anesthesia in five patients. The isoenzyme MB fraction rose mildly in five other patients and returned to normal within 72 hours. No clinical or electrocardiographic evidence of myocardial ischemia was detected. Follow-up for 4-12 months indicates no return of preexcitation or tachycardia in any patient whose accessory connection was successfully ablated. CONCLUSIONS: This experience indicates that radiofrequency current is an effective and safe technique for ablation of accessory connections in children.

Adolescent↗
PubMed1991

[Relative rigidity of standardized gutta-percha points].

Gutta-percha points often crack off when inserted in small and curved root canals before they have reached the full length of the canal. The goal of this investigation was to determine the relative rigidity of standardized gutta-percha points from different producers. It seems that not only significant differences between gutta-percha points of various producers, but also distinct variations between gutta-percha points from the same producer were detected. Several reasons for the differing rigidity of gutta-percha points are discussed.

Gutta-Percha↗
PubMed1991

Identification of a serum protein polymorphism via two-dimensional electrophoresis. Family and population studies in two genetically isolated groups: North American Hutterites and Australian aborigines.

We report the identification and initial family and population studies of a previously undescribed serum protein polymorphism with two allelic forms. It was discovered in Hutterites, a reproductively isolated religious sect, and is also present in Australian aborigines and a sample of Chicago residents. A two-allele model is consistent with the segregation pattern observed in five kindreds within our initial study group. This polymorphism, provisionally designated SPPM-158, appears as a horizontal (charge-based) doublet in silver-stained ISO-DALT high-resolution two-dimensional electrophoresis gels. It is a low-concentration polypeptide (approximately 1 mg/dL) that has an apparent MWSDS of 43.6 kD and an isoelectric point of approximately 5.5. We infer that it circulates as a multimer or in a high-molecular-weight (greater than 200 kD) complex with other proteins because it is not observed in normal body fluids derived from physiologically ultrafiltered plasma such as amniotic fluid, urine, or cerebrospinal fluid; however, it is present in urine of patients with glomerular proteinuria. The high heterozygosity rates imply utility of this new serum protein marker for both forensic and population studies.

Australia↗
PubMed1990

Ventricular arrhythmias in postoperative tetralogy of Fallot.

Ventricular arrhythmias in patients after total surgical repair of tetralogy of Fallot have been associated with late sudden death. In this large multicenter retrospective study of 359 patients with postoperative tetralogy of Fallot, spontaneous ventricular premature complexes (VPCs) on 24-hour ambulatory electrocardiographic monitoring and laboratory-induced ventricular tachycardia (VT) by electrophysiologic stimulation were analyzed. The mean age at surgical repair was 5 years and the mean follow-up duration after repair was 7 years. Spontaneous VPCs on ambulatory monitoring were found in 48% and induced VT on electrophysiologic stimulation was found in 17% of patients. Both spontaneous VPCs and induced VT were significantly related to delayed age at repair, longer follow-up interval, symptoms of syncope or presyncope and right ventricular systolic hypertension (greater than 60 mm Hg) (p less than 0.05), but not to right ventricular diastolic pressure greater than 8 mm Hg. The VPCs on ambulatory monitoring were more complex with increasing age at repair and follow-up duration. Induction of VT on electrophysiologic stimulation correlated with spontaneous VPCs including VT on 24-hour ambulatory electrocardiographic monitoring. The electrophysiologic stimulation protocol varied and the induction of VT increased with a more aggressive stimulation protocol. While induced sustained monomorphic VT was related to all forms of spontaneous VPCs, induced nonsustained polymorphic VT was related to more complex forms of VPCs on ambulatory monitoring. VT was not induced in asymptomatic patients who had normal 24-hour ambulatory electrocardiographic monitoring and normal right ventricular systolic pressure. (ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗