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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
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↗
PubMed1990

Shone's anomaly: operative results and late outcome.

Shone's anomaly, a congenital cardiac malformation, consists of multiple levels of left heart obstruction including supravalvar mitral ring, parachute mitral valve, subaortic stenosis, and coarctation. The prognosis for patients with Shone's anomaly is poor. To assess operative results and late outcome, we reviewed the records of 30 consecutive patients seen with Shone's anomaly at our institution between 1966 and 1989. Anatomical diagnoses in these patients were supravalvar mitral ring (22 patients), mitral valve abnormalities including parachute mitral valve, fused chordae, or single papillary muscle (26 patients), subaortic gradients (26 patients), and coarctation (29 patients). Nineteen patients had all four lesions. Other common defects were bicuspid aortic valve (19 patients) and ventricular septal defect (20). Two patients were treated medically. The other 28 patients required 84 operative procedures with 18 patients undergoing more than one procedure. Operations included coarctation repair (28 patients), mitral valve repair or replacement (11), ventricular septal defect closure (8), subaortic resection (8), and complex left ventricular outflow tract reconstruction or bypass (4). Age at first operation ranged from 7 days to 7 years (median age, 3 months). There were no operative deaths at the first operation. However, mortality rose to 24% (4/17) after the second operation. All operative deaths were secondary to severe mitral valve disease. The survivors have been followed from 1 to 16 years (mean follow-up, 6 +/- 1 years). There were no late or sudden deaths. Morbidity has included stroke (1), gastrointestinal bleeding (2), permanent heart block (1), and persistent congestive heart failure (6).(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Coarctation↗
PubMed1989

Pulsed Doppler assessment of left ventricular diastolic filling in children with left ventricular outflow obstruction before and after balloon angioplasty.

To assess left ventricular (LV) diastolic filling in children with pressure overload hypertrophy, 12 patients with LV outflow obstruction (7 with aortic valve stenosis and 5 with aortic coarctation) and 12 healthy, age-matched control subjects were examined. Each child underwent M-mode echocardiography and pulsed Doppler examination of the LV inflow. The patients with LV outflow obstruction had cardiac catheterization and balloon angioplasty. Their echo/Doppler examinations were performed in the catheterization laboratory before and immediately after balloon angioplasty. From the M-mode echocardiogram, the LV cavity dimensions and wall thicknesses, LV mass and shortening fraction were measured. The following measurements were made from the Doppler recording: peak velocities at rapid ventricular filling (peak E) and during atrial contraction (peak A), ratio of peak E to peak A velocities, total area under the Doppler curve, percent of the total Doppler area occurring in the first one-third of diastole (0.33 area fraction), percent of the total area occurring under the E wave (E area fraction), percent of the total area occurring under the A wave (A area fraction) and the ratio of E area to A area.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Failure of electrocardiographic monitoring to detect cardiac arrest in patients with pacemakers.

Two children with cardiac pacemakers are described who experienced cardiorespiratory arrest not detected by the electrocardiographic (ECG) monitor. The pacemaker stimuli were interpreted by the monitor as a QRS complex with inhibition of the heart rate alarm, demonstrating the need for reliable non-ECG monitoring in patients with pacemakers. A review of all deaths in children with pacemakers in the last ten years also shows the high association of respiratory failure in patients with congenital heart disease and a pacemaker, underscoring this need. Various non-ECG monitoring modalities are discussed. Finally, analysis of the ECG monitor characteristics contributing to inappropriate sensing of the pacemaker stimulus was performed, showing the direct relation between the pacemaker stimulus amplitude seen by the monitor and the monitor sensitivity with inappropriate sensing, and the inverse relation between the monitor bandwidth and inappropriate sensing. Recommendations for monitor adjustment when monitoring patients with pacemakers are provided.

Adolescent↗
PubMed1989

Repair of truncus arteriosus in the neonate and young infant.

Infants with truncus arteriosus present a difficult management issue. Because of the high operative mortality, repair is often delayed beyond the first 3 to 6 months of age. We reviewed our experience with 11 neonates and young infants with truncus arteriosus undergoing repair (median age, 21 days). Five patients also had major truncal valve insufficiency, and 2 required valve replacement. Right ventricle-pulmonary artery continuity was established with a porcine valved conduit in 3 patients and an aortic or pulmonary homograft in 8. There was 1 operative death (9%; 70% confidence limits, 3%-22%) and 1 late death over a mean follow-up of 21 months (range, 4 to 32 months). Eight of the 9 late survivors are growing normally. Echocardiographic examination revealed normal ventricular function in all patients (mean shortening fraction, 39%). Doppler assessment demonstrated trivial prosthetic or homograft valve regurgitation in 7 patients and mild to moderate obstruction in 5 patients. This recent experience with repair of truncus arteriosus indicates that the operative risk is low even in the neonate. Repair in the first month of life should be recommended before the development of critical congestive heart failure or irreversible pulmonary vascular disease.

Abnormalities, Multiple↗
PubMed1989

Concealed anterograde accessory pathway conduction during the induction of orthodromic reciprocating tachycardia.

The purpose of this study was to determine whether concealed anterograde accessory pathway conduction occurs during the induction of orthodromic tachycardia by an atrial extrastimulus (S2). Sixteen patients with an overt (n = 9) or concealed (n = 7) accessory pathway had inducible orthodromic tachycardia by S2 during an atrial drive (S1) cycle length of 500 to 650 ms. A ventricular extrastimulus (S3) was introduced coincident with the His depolarization resulting from S2 during the longest S1S2 interval that reproducibly induced orthodromic tachycardia. The S1S3 interval was decreased in 10 ms steps until S3 reached ventricular refractoriness. Retrograde accessory pathway conduction of S3 in the presence and absence of S2 was compared at the same S1S3 intervals. In the absence of S2 there was retrograde accessory pathway conduction after S3 in each patient. In the presence of S2, in patients with overt pre-excitation, retrograde accessory pathway conduction after S3 was absent in one patient, prolonged in four patients and present only after long S1S3 intervals in three patients. Only one patient had unchanged retrograde conduction regardless of the presence or absence of S2. In patients with a concealed accessory pathway, retrograde accessory pathway conduction after S3 was absent in five patients and was prolonged in two. Thus, concealed anterograde accessory pathway conduction was present in 15 of 16 patients at the time of orthodromic tachycardia induction. In conclusion, concealed anterograde accessory pathway conduction occurs in a majority of patients with an overt or a concealed accessory pathway during induction of orthodromic tachycardia by an atrial extrastimulus.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Psychosocial responses of children to cardiac pacemakers.

To examine the psychosocial responses of children and adolescents with a cardiac pacemaker and compare their responses to those of their peers, we evaluated 30 pediatric pacemaker patients, aged 7 to 19 years, and two age- and sex-matched comparison groups, including 30 patients with similar heart disease but without pacemakers and 30 physically healthy children, using standardized psychometric tests and a specific interview format. We postulated that children with pacemakers would experience greater stress in psychosocial adaptation. No significant differences on standardized measures of trait anxiety, self-competence, or self-esteem were found between the pacemaker group and the comparison groups. In contrast, pacemaker subjects were significantly (p less than 0.05) more external in their locus-of-control orientation than were healthy subjects, suggesting a diminished sense of personal control and less autonomy. Pacemaker subjects, particularly the older ones, had significantly (p less than 0.05) greater knowledge of pacemaker systems than did subjects in the other two groups, facilitating the use of intellectualization as a coping mechanism. The pacemaker patients were likely to be as fearful of social rejection as of potential pacemaker failure. All three groups identified potential negative peer reactions toward an individual with a pacemaker. The patients with cardiac disease but without pacemakers and the healthy subjects perceived significant (p less than 0.05) social and emotional differences between patients with pacemakers and their peers, but the pacemaker patients did not view themselves as different from their peers. This study demonstrates healthy psychosocial adaptation of children with cardiac pacemakers. Although these children appear to cope effectively with the stress of their life situation through the use of denial and intellectualization, they may experience problems both in the development of autonomy and in social isolation and rejection.

Adolescent↗
PubMed1989

Transcatheter electrical ablation of accessory pathways in children.

Supraventricular tachycardia (SVT), the most common sustained symptomatic arrhythmia of childhood, is often supported by a manifest or concealed accessory pathway. Permanent interruption of the accessory pathway usually requires surgical division. Recent experience with electrical ablation of posterior septal pathways in adults prompted us to apply the technique to children. Six children, ages 8 to 15 years, underwent a complete electrophysiological study followed by transcatheter electrical ablation. Five of the 6 children, 3 with a right posterior septal and 2 with a left posterior septal pathway, were approached with the ablation catheter at the os of the coronary sinus. In the remaining patient, a left lateral pathway was mapped with an electrode catheter in the coronary sinus and then approached with the ablation catheter through the patent foramen into the left atrium. Two patients are asymptomatic 18-24 months postablation; one patient had return of anomalous conduction between 7 and 21 days after ablation. Two patients had transient interruption of anomalous conduction, whereas one patient experienced no effect. We conclude that in carefully selected patients, transcatheter electrical ablation offers an alternative to surgery for permanent interruption of an accessory pathway.

Adolescent↗
PubMed1989

Long-term results of catheter ablation of a posteroseptal accessory atrioventricular connection in 48 patients.

Forty-eight patients with a posteroseptal accessory atrioventricular (AV) connection underwent catheter ablation of the accessory AV connection with 200-400 J shocks delivered by a standard defibrillator. Cathodal shocks were delivered through the proximal pair of electrodes of a 6F quadripolar electrode catheter positioned in the coronary sinus such that the proximal electrodes straddled the ostium (12 patients) or the third electrode from the tip was at the ostium (36 patients). A 16-cm patch electrode positioned on the back or anterior chest served as the anode. Two to 4 shocks were delivered (total, 635 +/- 198 J, mean +/- SD). The cathether ablation procedure was clinically successful in eliminating symptomatic tachycardias in in 32 of 48 patients (67%) during a mean follow-up of 26 +/- 19 months. A long-term follow-up electrophysiology study was performed in 27 of the 32 patients who had a successful clinical outcome, and this showed that conduction through the accessory AV connection was completely absent in 25 patients and present but impaired in two patients. The success rate was significantly higher in patients with a concealed accessory AV connection (13 of 13, 100%) than in patients with manifest preexcitation (19 of 35, 54%; p less than 0.001). Among the 12 patients in whom the proximal electrodes of the ablation catheter straddled the ostium of the coronary sinus, one patient developed cardiac tamponade requiring needle pericardiocentesis; there were no instances of cardiac tamponade among the 36 patients in whom the third electrode from the tip was at the ostium of the coronary sinus. Other complications were AV block requiring a permanent pacemaker and transient atrial tachycardia in one patient each and an asymptomatic pericardial effusion in three patients. In conclusion, with the catheter ablation technique described in this study, a successful clinical outcome may be achieved in approximately two thirds of patients who have a posteroseptal accessory AV connection, and the risk of serious complications is low. This technique is particularly well suited to patients with a concealed posteroseptal accessory AV connection, in whom the success rate is higher than in patients with manifest preexcitation.

Adult↗
PubMed1989

Sequence of the variant thyroxine-binding globulin of Australian aborigines. Only one of two amino acid replacements is responsible for its altered properties.

A form of thyroxine-binding globulin (TBG) with reduced affinity for hormone and increased susceptibility to heat and acid denaturation has been identified in Australian Aborigines (TBG-A). Results of heat denaturation of TBG established that the TBGA allele is X linked and has a frequency of 50.9% in Western Australian Aborigines. The sequence of an isolated TBGA allele differed at two positions from that of the normal TBG allele (TBGC). One substitution was in codon 191, ACA (threonine) rather than GCA (alanine), and the other was in codon 283, TTT (phenylalanine) instead of TTG (leucine). These nucleotide substitutions resulted in the loss of sites for the enzymes Bgl 1 and Tth 111 II, respectively. The nucleotide substitutions in the TBG-A allele was confirmed by digestion of genomic DNA segments amplified using the polymerase chain reaction. The Bgl 1 and Tth 111 II sites were absent in the genes of two Aboriginal men expressing TBG-A and were present in those of three Aboriginal and six Caucasian males expressing TBG-C. The TBG gene of a seventh Caucasian male possessed the Bgl 1 site but had lost the Tth 111 II site; sequencing of this allele revealed only the substitution in codon 283 identical to that in the TBGA allele. As the biochemical properties of TBGPhe-283 expressed by this individual were indistinguishable from normal TBGLeu-283, we believe that the abnormal properties of TBG-A are due to substitution of alanine for threonine at residue 191.

Adolescent↗
PubMed1989

Visual orientation estimation.

A systematic error is reported in orientation estimation, in that on average, estimates are closer to the vertical axis than are the stimuli by up to 6 degrees. This systematic error results from a specific mechanism that may be related to depth perception, and that is avoided in certain circumstances or when other mechanisms take over. For example, the estimates of one observer who was a well-trained professional draughtsman did not show this systematic error. Furthermore, for all observers tested, estimation of clock time is not subject to the regular orientation estimation error. Rather, observers tend to estimate times as slightly further from the quarter hour than they really are. Orientation judgement channel capacity was also studied under various conditions. The number of discriminable orientations is far above the magic number "7" limit, reaching over 20 in optimal circumstances. The distribution of discriminable orientations is nonlinear, in that these are more closely packed about the horizontal and vertical axis than at the oblique.

Attention↗