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Biomedical subjects

J A Till

Publications and source records attributed to J A Till.

At least 19 recordsLinked to original sources
PubMed2000

Sudden death in a child with an unusual accessory connection.

An 8-year-old boy with Wolff-Parkinson-White syndrome died suddenly whilst exercising. He had been well with no immediate preceding symptoms of an arrhythmia, and was receiving no drugs. As an infant he had suffered recurrent episodes of atrioventricular reciprocating tachycardia (AVRT) and had documented pre-excited atrial fibrillation. At electrophysiological (EP) study, the refractory periods of his two accessory pathways were less than 220 ms. Drugs were discontinued at 4 years of age when he remained asymptomatic. Autopsy confirmed a very unusual accessory pathway. It was a muscular connection between the base of the right atrial appendage and the right ventricle, distant from the annulus of the tricuspid valve.

Child↗
PubMed1997

Depolarization-repolarization inhomogeneity after repair of tetralogy of Fallot. The substrate for malignant ventricular tachycardia?

BACKGROUND: We have previously shown that QRS prolongation (> or = 180 ms) is a risk marker for sustained ventricular tachycardia (VT) late after repair of tetralogy of Fallot (rTOF). We have now examined the dispersion of QT and its components QRS and JT, in an attempt to determine whether any association exists between these measurements and the presence of VT in these patients. METHODS AND RESULTS: QRS duration and QT/QRS/JT dispersion were measured manually from standard ECGs in 10 syncopal rTOF patients (21.4 +/- 4.6 years after repair; group 1) with QRS > or = 180 ms and with documented VT and were compared with 9 rTOF patients with QRS > or = 180 ms and no VT (group 2), 40 rTOF patients with QRS < 180 ms and no clinical arrhythmias (group 3), and 40 nontetralogy control subjects (20 with right bundle-branch block [group 4] and 20 with normal ECG patterns [group 5]). Mean QT dispersion (62 +/- 36 ms) in the tetralogy patients was greater than in the nontetralogy control subjects (34 +/- 10 ms, P < .001). There were significant differences in all measured parameters between groups 1 and 3 and more importantly between groups 1 and 2. QRS dispersion in group 1 also correlated with QRS duration but not with JT dispersion. CONCLUSIONS: Our data suggest that both depolarization and repolarization abnormalities are associated with VT after rTOF. Furthermore, increased QT, QRS, and JT dispersions, combined with a QRS > or = 180 ms, refine risk stratification for VT in these patients.

Adult↗
PubMed1995

Mechanoelectrical interaction in tetralogy of Fallot. QRS prolongation relates to right ventricular size and predicts malignant ventricular arrhythmias and sudden death.

BACKGROUND: Life-threatening ventricular arrhythmia and sudden death remain serious late complications after tetralogy of Fallot repair. Nevertheless, there remains no clear way of predicting which patients are at risk. METHODS AND RESULTS: The study population included a total of 178 adult survivors (mean follow-up, 21.4 years) of tetralogy of Fallot repair who were currently attending our clinic. Mechano-electrical relations were sought in 41 of the patients (mean follow-up, 23.6 years) who were operated on by one surgeon and who were prospectively studied with a 12-lead ECG, chest radiography, and two-dimensional and Doppler echocardiography. Nine patients (mean follow-up, 17 years) from the total group of 178 were identified as having had sustained ventricular tachycardia (8 with near-miss sudden death), and their ECGs, Holter monitor readings, electrophysiological studies, and chest radiographs were reviewed. The case notes of an additional 4 patients with postoperative sudden cardiac death also were available for review. QRS duration in the 41 patients in whom mechanoelectrical interaction was sought ranged between 90 and 200 milliseconds and correlated with cardiothoracic ratio (CTR) on chest radiography (r = .64, P < .001) and with right ventricular size on echocardiography (r = .43, P < .02). Twenty of the 41 patients had restrictive right ventricular Doppler physiology (reduced ventricular compliance) with mean QRS duration of 129.3 +/- 20 milliseconds and mean CTR of 0.51 +/- 0.03. The remaining 21 patients with no evidence of right ventricular restriction had prolonged QRS duration of 157.5 +/- 13.2 milliseconds (P < .001) and CTR of 0.55 +/- 0.04 (P < .04) compared with the restrictive. In the 9 patients with ventricular tachycardia, the QRS duration ranged from 180 to 230 milliseconds (mean, 198.9 +/- 17.6 milliseconds), and the CTR ranged from 0.54 to 0.9 (mean, 0.67 +/- 0.12) (P < .0001 and P < .01, respectively, compared with patients without life-threatening arrhythmias). All patients with documented sustained ventricular tachycardia and the 4 patients with sudden death had a QRS duration of > or = 180 milliseconds (100% sensitivity). CONCLUSIONS: Chronic right ventricular volume overload after tetralogy of Fallot repair is related to diastolic function and correlated with QRS prolongation. The risk of symptomatic arrhythmia is high when marked right ventricular enlargement and QRS prolongation develop. A QRS duration on the resting ECG of > or = 180 milliseconds is the most sensitive predictor of life-threatening ventricular arrhythmias yet described.

Adult↗
PubMed1994

Aerodynamic and temporal disruptions of speech in laryngeal insufficiency.

OBJECTIVES: To describe the effects of laryngeal insufficiency on aerodynamic and temporal aspects of speech breathing and speech production. DESIGN: A survey study with statistical comparisons of patient and normal subject groups. SETTING: Private and institutional practice. PATIENTS: A convenience sample of 23 subjects with laryngeal insufficiency was compared with a volunteer sample of 20 normal-speaking subjects. Patients had frank unilateral recurrent nerve paralysis-paresis or idiopathic laryngeal insufficiency as verified by videostrobolaryngoscopy. MAIN MEASURES: Mean airflows, air volumes, and durations for speech inspirations, speech phrases, and non-inspiratory pauses during samples of monologue speech. RESULTS: In comparison with the normal group, the patient group had significantly (P < .01) higher expiratory airflows and volumes during speech and reduced speech phrase durations. In addition, breaths per minute, inspiratory minute volume, and inspiratory airflow were significantly (P < .01) higher for the patient group. An experimental measure of aerodynamic yield for speech increased the statistical separation of the patient and normal groups compared with analyses using simple expiratory airflow measures alone. CONCLUSIONS: Insufficient contact of the true vocal folds during speech can affect more than just voice quality. Likely effects include (1) reduced speech phrase duration, (2) increased breaths per minute, (3) increased inspiratory minute volume, and (4) increased inspiratory airflow rate.

Adult↗
PubMed1994

Ebstein's anomaly: presentation and outcome from fetus to adult.

OBJECTIVES: This study was conducted to investigate the presentation and outcome of patients with Ebstein's anomaly of the tricuspid valve. BACKGROUND: Ebstin's anomaly may present at any age and has a highly variable clinical course. Previous natural history studies have been based on clinical and angiographic diagnosis and have included mainly older children and adults. Echocardiography, however, has facilitated fetal and neonatal diagnosis so that the natural history needs to be redefined. METHODS: We reviewed 220 cases of Ebstein's anomaly presenting from fetal to adult life between 1958 and 1991, with 1 to 34 years of follow-up. RESULTS: The most common presentation in each age group was abnormal routine prenatal scan for fetuses (86%), cyanosis for neonates (74%), heart failure for infants (43%), incidental murmur for children (63%) and arrhythmia for adolescents and adults (42%). Early presentation was frequently associated with other cardiac lesions, usually pulmonary stenosis or atresia. Surgery was undertaken at some stage in 86 (39%) of the 220 patients. Actuarial survival for all liveborn patients was 67% at 1 year and 59% at 10 years. There were 58 deaths, including 26 from heart failure, 19 perioperative and 8 sudden. Predictors of death included echocardiographic grade of severity at presentation (relative risk 2.7 for each increase in grade, 95% confidence limits 1.6 to 4.6), fetal presentation (6.9, confidence limits 1.6 to 16.5) and right ventricular outflow tract obstruction (2.1, confidence limits 1.1 to 4.4). Morbidity was mainly related to arrhythmias and late hemodynamic deterioration. Of 155 survivors, 129 (83%) were in functional class 1 and 104 (67%) were receiving no medical therapy. CONCLUSIONS: In Ebstein's anomaly, fetal and neonatal presentation is associated with a poor outcome and can be predicted by the echocardiographic appearance and presence of associated lesions. In older children and adults, incidental findings and arrhythmia are common and the long-term outcome is superior.

Adolescent↗
PubMed1993

Time-shift, trial, and gender effects on vocal perturbation measures.

Three jitter and three shimmer measures were examined for: (1) the stability of the measured values with respect to shifts in sample site (starting point of window in the token) and (2) the effects of trial and gender. The perturbation measures and their coefficients of variation for windows starting from five different but adjacent cycles showed a dependence on sample size. Their variability with regard to shifts in sample site decreased asymptotically with increasing size. The data suggested no statistically significant trial effect except for APQ and no statistically significant gender effect except for absolute jitter. It is speculated that relatively long smoothing windows for shimmer (such as the one used for APQ) would allow the effects of slow vocal modulations (e.g., tremor) to accentuate, especially for lower pitch speakers.

Adult↗
PubMed1993

Interactive effects of local smoothing window size and fundamental frequency on shimmer calculation.

Slow amplitude modulation of human voice was approximated by a sinusoidal wave. The theoretical effects of smoothing window size, F0, and modulation frequency on window amplitude average as well as calculated shimmer were mathematically derived. Subsequently, the theoretical predictions were tested using idealized and real voice signals from normal speakers. The theoretical and experimental results suggest that shimmer (when calculated using a smoothing window) is a function of window duration and modulation frequency. Window duration when defined as a constant number of pitch periods varies from speaker to speaker depending on their F0. It may not be desirable to use local smoothing windows with a constant number of cycles for shimmer computation, especially if voices with known low-frequency amplitude modulations but notably different fundamental frequencies are compared.

Aged↗
PubMed1992

Histopathological findings in three children with His bundle tachycardia occurring subsequent to cardiac surgery.

This report concerns three children with His bundle tachycardia who died following cardiac surgery. At autopsy the conduction system was examined in detail. In all three, the sinus node was intact and supplied by a well-formed artery. Haemorrhagic tracks were identified invading the penetrating atrioventricular bundle. The tracks originated from stitches placed close to the conduction tissue. The hypothesis that disruption of the conduction tissue results in an arrhythmogenic focus is discussed.

Bundle of His↗
PubMed1991

Atrial pacing as an adjunct to the management of post-surgical His bundle tachycardia.

OBJECTIVE: To examine the benefits of restoring atrioventricular synchrony to children with His bundle tachycardia after operation for congenital heart disease. DESIGN: Review of clinical outcome of adopting the technique of R wave synchronised atrial pacing as an adjunct to the management of His bundle tachycardia from September of 1987 till June of 1990. PATIENTS: Eleven consecutive children (aged between 3 days and 13 years) with haemodynamically significant His bundle tachycardia after cardiopulmonary bypass surgery. INTERVENTIONS: Atrial pacing synchronised either manually or automatically to the R wave of the His bundle tachycardia was implemented so that atrial depolarisation preceded the following R wave by an appropriate PR interval. RESULTS: An immediate and sustained increase in mean systemic blood pressure (average 15 mm Hg, range 6-30 mm Hg) was seen with the onset of atrial pacing in 10 of the 11 children. One child, who had undergone a Fontan procedure, developed atrial flutter shortly after the onset of atrial pacing and required direct current cardioversion. Four children died. Of the seven survivors, six have sustained sinus rhythm which returned between two and 10 days after the onset of tachycardia. One of the survivors has severe neurological impairment attributed to a period of low cardiac output during tachycardia; the others are alive and well. In those children who did badly the mean time between arrhythmia occurrence and the start of atrial pacing or cooling or both was nine hours; in those who did well it was one hour. CONCLUSIONS: Atrial pacing synchronous with the His bundle is a useful adjunct in the management of children with His bundle tachycardia after surgery for congenital cardiac disease.

Adolescent↗
PubMed1990

Endocardial pacing in infants and children 15 kg or less in weight: medium-term follow-up.

Twenty-four children 15 kg or less in weight (range 2.8-15 kg) underwent implantation of a permanent pacemaker using the transvenous technique of lead placement. During a follow-up period of 2 months to 6 years 1 month (median 3 years 6 months) eight children suffered complications, six of which necessitated reoperation. These included: lead fracture in two, infection in two, transient myocardial dysfunction in one, generator migration in one, premature battery depletion in one, and threshold rise in one. A loop of redundant ventricular lead positioned in the atrium at the time of implant is successfully unravelling in all children. One child died during the follow-up period of a pneumonia unrelated to her pacemaker. The other children are growing and developing normally and the cosmetic appearance has proved acceptable in all cases.

Body Weight↗
PubMed1990

Exercise ability after Mustard's operation.

Twenty children who were well six to 12 years after undergoing Mustard's operation for transposition of the great arteries were studied. Each child performed a graded maximal treadmill test with measurements of gas exchange and oxygen saturation, and had electrocardiography carried out. Nineteen were also catheterised, and oxygen consumption was measured so that pulmonary and systemic flow could be calculated. Compared with 20 age and size matched controls, seven of the patients had normal exercise tolerance (as judged by a maximal oxygen consumption of greater than 40 ml/kg/min), 10 showed a moderate reduction (30-39 ml/kg/min), and three were more seriously limited. None of the patients with normal exercise tolerance had obstruction of venous return but six of those with mild impairment of exercise ability had partial or complete obstruction of one or both of the vena cavas. More severe limitation was associated with pulmonary vascular disease and fixed ventricular outflow tract obstruction. Formal exercise testing of apparently well children who have undergone Mustard's operation identifies those with haemodynamic abnormalities that may require intervention.

Adolescent↗
PubMed1990

Plasma concentration of atrial natriuretic peptide in spontaneous atrioventricular re-entrant tachycardias of childhood.

Plasma atrial natriuretic peptide was measured in 13 children between the ages of 1 week and 2 years 9 months during atrioventricular re-entrant tachycardia and 15 minutes after the restoration of sinus rhythm. There was a significant decline in atrial natriuretic peptide during sinus rhythm. Plasma concentrations of the peptide were significantly higher during tachycardia in seven infants under 1 year than in the six older children. The heart rates and the duration of tachycardia were not significantly different in the two age groups. Cardiac failure was present in five of seven children under 18 weeks of age during tachycardia but in none of the older children. The plasma concentration of atrial natriuretic peptide did not significantly correlate with duration of tachycardia or heart rate. If tachycardia occurs in young infants the low functional reserve capacity of the developing heart leads to cardiac failure more frequently and it is likely that this was the cause of the significantly higher plasma concentration of atrial natriuretic peptide in the younger children.

Adenosine↗
PubMed1989

Paediatric use of flecainide in supraventricular tachycardia: clinical efficacy and pharmacokinetics.

Twenty three children with recurrent supraventricular tachycardia were treated with flecainide. Twenty one of these received intravenous treatment during an attack (2 mg/kg over 10 minutes). The tachycardia was terminated in 17. After an intravenous bolus of flecainide, blood samples were drawn at regular intervals for analysis of flecainide concentration over 48 hours. Pharmacokinetic variables were calculated--median terminal half life 7.5 hours, median volume of distribution 6.2 l/kg, and median plasma clearance 7.2 ml/min/kg. There was a significant correlation between half life and age. Twenty of the children received long term treatment with an oral preparation of flecainide to prevent further attacks. Twelve had no further attacks and 16 were considered to have good control. Two children suffered potentially serious arrhythmogenic effects soon after the start of oral treatment and flecainide had to be stopped. During oral treatment regular blood samples were drawn and plasma concentrations were analysed to assess the therapeutic range. This did not differ substantially from that proposed in adults (400-800 micrograms/l). Eight children were electively withdrawn from oral flecainide to see whether they really needed it. Blood samples for measurement of flecainide concentration were drawn after their last oral dose. Pharmacokinetic variables were calculated: time to maximum concentration 2 hours, median terminal half life 7.9 hours. For the combined data from patients receiving intravenous and oral treatment there was a significant correlation between elimination half life and age. An intravenous dose of 2 mg/kg over at least 10 minutes and an initial oral dose of 6 mg/kg/day in three divided doses is recommended. Treatment should be started in hospital so that children in whom the drug may be arrhythmogenic can be identified and plasma concentrations measured to identify patients in whom lack of efficacy is caused by underdosage.

Administration, Oral↗
PubMed1988

Long-term treatment of severe dysarthria: a case study.

This case study describes the long-term treatment and changing symptoms in a single subject with dysarthria secondary to basilar artery thrombosis. Initially, the subject was anarthric. Treatment efforts thereafter were directed toward modifying speech respiration, velopharyngeal function, articulatory precision, speech intensity, and speech intelligibility. A variety of treatment and measurement techniques are illustrated. The behavioral change resulting from each of the treatments was small. However, when combined, these small gains in conjunction with some neurological recovery resulted in significantly improved communication and quality of life for this subject. Implications for management of similar subjects are discussed.

Behavior Therapy↗