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Biomedical subjects

J Therrien

Publications and source records attributed to J Therrien.

At least 19 recordsLinked to original sources
PubMed2002

Acute myocardial infarction late after Mustard procedure for dextrotransposition of the great arteries.

Systemic right ventricular dysfunction has been closely linked to late mortality and sudden cardiac death in patients with Mustard procedure for dextrotransposition of the great arteries. Two young patients with dextrotransposition of the great arteries late after Mustard procedure who presented with acute transmural myocardial infarction and sudden cardiac death (one patient) without prior exertional angina or causative coronary abnormalities are reported. It is surmised that acute coronary emboli originating from a severely dilated, hypocontractile systemic ventricle were the cause of transmural myocardial infarction. This phenomenon may be an important and as yet unrecognized factor in late morbidity and mortality in such patients.

Adolescent↗
PubMed2001

Impact of pulmonary valve replacement on arrhythmia propensity late after repair of tetralogy of Fallot.

BACKGROUND: Chronic pulmonary regurgitation after repair of tetralogy of Fallot (TOF) may lead to right ventricular dilatation, which may be accompanied by ventricular tachycardia and sudden death. We aimed to examine the effects of pulmonary valve replacement (PVR) on (1) certain electrocardiographic markers predictive of monomorphic ventricular arrhythmia and sudden death and (2) sustained atrial flutter/fibrillation and monomorphic ventricular tachycardia. METHODS AND RESULTS: We studied 70 patients who underwent PVR for pulmonary regurgitation and/or right ventricular outflow tract obstruction late after repair of TOF. Maximum QRS duration and QT dispersion were measured from standard ECGs before PVR and at the latest follow-up. Arrhythmia was defined as sustained atrial flutter/fibrillation or sustained monomorphic ventricular tachycardia. Concomitant intraoperative electrophysiological mapping and/or cryoablation were performed in 9 patients (60%) with preexisting ventricular tachycardia and 6 patients (50%) with preexisting atrial flutter. QRS duration remained unchanged in the study group (P=0.46), but it was significantly prolonged (P<0.001) in a comparable group of patients with repaired TOF who did not undergo PVR. At a mean follow-up of 4.7 years, the incidence of ventricular tachycardia diminished from 22% to 9% (P<0.001), and atrial flutter/fibrillation decreased from 17% to 12% (P=0.32). Intraoperative ablation prevented recurrence of preexisting tachyarrhythmia (0 of 15 patients). CONCLUSIONS: PVR in patients with previous TOF repair and chronic pulmonary regurgitation leads to stabilization of QRS duration and, in conjunction with intraoperative cryoablation, to a decrease in the incidence of preexisting atrial and ventricular tachyarrhythmia. When applicable, this combined approach should be used in patients late after repair of TOF.

Adolescent↗
PubMed2001

Aerobic capacity in adults with various congenital heart diseases.

As an increasing number of patients with congenital heart disease reach adulthood, more information is needed regarding outcomes. The first signs of impaired heart function may appear during exercise testing. The aim of the present study was to establish mean values for maximal oxygen uptake in adults with various congenital heart diseases. Patients from 6 major diagnostic groups were identified, including patients with atrial septal defect (ASD, n = 93), transposition of the great arteries corrected with the Mustard procedure (n = 84), congenitally corrected transposition of the great arteries (CCTGA, n = 41), Tetralogy of Fallot (n = 168), Ebstein's anomaly (n = 37), and Modified Fontan procedure (n = 52). Diminished maximal oxygen uptake was found in all diagnostic groups across age compared with healthy subjects. A significant decrease in maximal oxygen uptake with aging was found in those with ASD (p <0.0001), CCTGA (p = 0.01), and Tetralogy of Fallot (p <0.0001). There was no significant decline, however, in Ebstein's anomaly (p = 0.270), Fontan procedure (p = 0.182), and in the Mustard patients (p = 0.188). All patients achieved significantly lower heart rates than predicted (mean for all groups, p <0.0001). Forced vital capacity values (3.51 L, mean SD +/- 1.02) were lower than predicted values (4.10 L, mean SD +/- 0.90, p <0.0001) for all patients groups except those with ASD. Mean values, however, were within the accepted 20% range of variance. This study showed diminished aerobic capacity in all diagnostic groups when compared with a healthy population. The maximal oxygen uptake values across age groups can be used as reference values in patients with similar diagnoses and as the basis for further research.

Adolescent↗
PubMed2001

Synthesis and characterization of the colistin peptide polymyxin E1 and related antimicrobial peptides.

Two strategies were developed to synthesize the acylated cyclic peptides know as polymyxins. Synthesis of polymyxin E1 and several analogs enabled us to evaluate the minimum inhibitory concentration of individual compounds against Gram-negative bacteria. In this study we also report the first identification of two component peptides in the complex polymyxin fermentation product colistin, a Thr2Ser isoform and an acyl group isomer. Both of these peptides, as well as a known component peptide, Leu7Ile, were similar to polymyxin E1 in potency, suggesting that conservative mutations in the colistin family are functionally inconsequential. In contrast, the acyclic analogs of all of these peptides were inactive, indicating that the characteristic lariat structure of the polymyxins is necessary for antimicrobial activity.

Anti-Bacterial Agents↗
PubMed2001

Exercise capacity in adult patients with congenitally corrected transposition of the great arteries.

OBJECTIVE: To examine cardiopulmonary values, static lung function, and ejection fraction in adult patients with congenitally corrected transposition of the great arteries (CCTGA). PATIENTS AND METHODS: 41 patients who had undergone static lung function testing and cardiopulmonary exercise tests with measurements of ejection fraction were identified at the Toronto Congenital Cardiac Centre for Adults. RESULTS: Aerobic capacity in patients with CCTGA was severely diminished, varying from 30-50% of the results achieved by healthy subjects. Normal values of right ventricular and left ventricular ejection fraction were found. However, the systemic right ventricular ejection fraction increased by 2% from rest to exercise, as opposed to the expected > 5% increase in a healthy population. The pulmonary left ventricular ejection fraction decreased by 2% at peak exercise. CONCLUSION: Diminished values of heart rate, forced expiratory volume in one second (FEV(1)), forced vital capacity, and systolic blood pressure compared to the predicted values may contribute to the reduced maximal oxygen uptake (VO(2)max) found in patients with CCTGA. In addition, a limited increase in systolic right ventricular ejection fraction and a decrease in pulmonary left ventricle contractility suggest a dysfunction of both ventricles.

Adult↗
PubMed2001

Lung function and aerobic capacity in adult patients following modified Fontan procedure.

OBJECTIVE: To examine cardiopulmonary performance in 52 adult patients with a Fontan circulation. DESIGN: Retrospective cohort study. Values of maximum oxygen uptake (VO(2)max), maximum heart rate (HRmax), forced vital capacity (FVC), and forced expiratory volume in one second (FEV(1)) were compared with predictive values for different age groups. Patients were further subdivided into those with a pulmonary artery connection (RA-PA) or right atrium to right ventricle conduit (RA-RV). RESULTS: At late follow up (median 10 years, range 1 to 26 years), patients with Fontan circulation had greatly diminished VO(2)max, HRmax, FVC, and FEV(1) compared with predicted values. Early age at surgery had a positive impact on aerobic capacity. The FEV(1):FVC ratio indicated restrictive lung function. No differences were found with respect to any variable between patients with RA-PA connections and those with RA-RV connections. CONCLUSIONS: Patients with a Fontan circulation have greatly diminished values of aerobic capacity and a restrictive pattern of lung function. Patients with an early surgical procedure obtained higher values of VO(2)max. The theoretical benefits of including the right ventricle in a Fontan circulation were not apparent.

Adult↗
PubMed2000

Pulmonary valve replacement in adults late after repair of tetralogy of fallot: are we operating too late?

OBJECTIVES: The purpose of this study is to evaluate right ventricular (RV) volume and function after pulmonary valve replacement (PVR) and to address the issue of optimal surgical timing in these patients. BACKGROUND: Chronic pulmonary regurgitation (PR) following repair of tetralogy of Fallot (TOF) leads to RV dilation and an increased incidence of sudden cardiac death in adult patients. METHODS: We studied 25 consecutive adult patients who underwent PVR for significant PR late after repair of TOF. Radionuclide angiography was performed in all at a mean of 8.2 months (+/- 8 months) before PVR and repeated at a mean of 28.0 months (+/- 22.8 months) after the operation. Right ventricular (RV) end-systolic volume (RVESV), RV end-diastolic volume (RVEDV) and RV ejection fraction (RVEF) were measured. RESULTS: Mean RVEDV, RVESV and RVEF remained unchanged after PVR (227.1 ml versus 214.9 ml, p = 0.74; 157.4 ml versus 155.4 ml, p = 0.94; 35.6% versus 34.7%, p = 0.78, respectively). Of the 10 patients with RVEF > or = 0.40 before PVR, 5 patients (50%) maintained a RVEF > or = 0.40 following PVR, whereas only 2 out of 15 patients (13%) with pre-operative values <0.40 reached an RVEF > or = 0.40 postoperatively (p < 0.001). CONCLUSIONS: Right ventricular recovery following PVR for chronic significant pulmonary regurgitation after repair of TOF may be compromised in the adult population. In order to maintain adequate RV contractility, pulmonary valve implant in these patients should be considered before RV function deteriorates.

Adolescent↗
PubMed2000

Right ventricular long axis function in adults and children with Ebstein's malformation.

OBJECTIVES: To assess right ventricular function in adults and children with Ebstein's anomaly. DESIGN: Prospective study. SETTING: Tertiary referral centre. SUBJECTS: Fifteen patients (8 adults and 7 children) with Ebstein's anomaly and 14 healthy controls. INTERVENTIONS: Transthoracic echocardiography was performed in all. Right ventricular function was assessed from long axis M-mode recordings of the right atrio-ventricular free wall. Total systolic excursion as well as peak shortening and lenghtening rates of the right ventricle were measured. RESULTS: Children and adult patients with Ebstein's anomaly differed in terms of age at diagnosis, the adult group having been diagnosed later 19.8+/-15.8 vs. 5.9+/-6.2 years, P<0.05. Measures of right ventricular long axis function in children with Ebstein's anomaly showed a significantly reduced systolic excursion 1.4+/-0.4 vs. 2.4+/-0.53 cm, P<0.05 and peak lenghtening rate; early 8.04+/-4.3 vs. 11.8+/-2.4 cm/s and late 6.14+/-3.6 vs. 10.6+/-4.3 cm/s, P=0.05 compared to controls. In contrast, measurements of right ventricular long axis function in adults with Ebstein's anomaly showed no significant difference when compared to the control group. Transtricuspid Doppler flow velocities were not different between patient's groups and corresponding controls. CONCLUSION: The right ventricle assessed by this simple, non-invasive technique reveals a significantly reduced systolic and diastolic function in children with Ebstein's malformation compared to controls but a 'normal' right ventricular function comparable to controls in adult patients. Significant right ventricular dysfunction in children with Ebstein's anomaly could account for their earlier presentation. Long term follow up of the right ventricular abnormalities is needed in such children to discover more about the natural history of the disease.

Adult↗
PubMed2000

Repaired coarctation: a "cost-effective" approach to identify complications in adults.

OBJECTIVES: The study was done to determine the most "cost-effective" approach to follow adults after repair of coarctation of the aorta. BACKGROUND: Recoarctation and/or aneurysm formation following surgical repair or angioplasty for coarctation of the aorta carry a significant morbidity and mortality. Various screening tests to detect such complications are used, but little is known of their sensitivities and specificities; as a consequence, the most "cost-effective" approach to follow such patients is undefined. METHODS: Retrospective analysis was done on the sensitivity and specificity of symptomatology, physical examination, electrocardiogram, chest radiograph, exercise testing and transthoracic echocardiography to detect recoarctation and/or aneurysm formation in 84 adult patients following surgical repair or angioplasty of coarctation of the aorta, using magnetic resonance imaging (MRI) as the gold standard test. RESULTS: Echocardiography had the highest sensitivity in detecting recoarctation (87%) and chest radiograph the highest sensitivity in detecting aneurysm formation (67%). Combined clinical visit and echocardiography had a high sensitivity for diagnosing recoarctation and/or aneurysm formation (97%), but performing a clinical visit and an MRI on every patient without any prior screening test emerged as the most "cost-effective" strategy. CONCLUSIONS: The most "cost-effective" approach to diagnose complications at the site of repair in patients after surgical repair or balloon angioplasty of coarctation of the aorta appears to be the combination of clinical assessment and MRI scan on every patient. If MRI resources are scant, performing a clinical assessment plus a transthoracic echocardiography and an MRI on patients with positive results is an acceptable alternative.

Adolescent↗
PubMed1999

Outcome of pregnancy in patients with congenitally corrected transposition of the great arteries.

To assess maternal and fetal outcome of pregnancy in patients with congenitally corrected transposition of the great arteries, we reviewed 19 patients (18 retrospectively) who had 45 pregnancies. Their ages ranged from 18 to 40 years (mean 27) at the time of pregnancy. Thirty-six percent of the pregnancies were undertaken while patients were cyanosed, 7% in patients with unpaced complete heart block, and 16% were undertaken after surgical repair of the associated anomalies. Change in functional class and maternal cardiovascular complications during pregnancy were analyzed as well as number of live births, miscarriages, elective termination of pregnancies, timing of delivery, and incidence of cardiac defects in the live offspring. Five patients (26% of patients) developed cardiovascular complications during pregnancy, namely congestive heart failure (3 patients), worsening cyanosis (1 patient), and cerebrovascular accident (1 patient). No maternal deaths occurred. There were 27 live births (60%), 12 miscarriages (27%), and 6 elective terminations of pregnancy (13%). Cyanosis was a significant risk factor for miscarriage. One live offspring had congenital heart disease. Close follow-up of these patients during pregnancy, by a team of experienced physicians, is recommended.

Abortion, Spontaneous↗
PubMed1999

Patent Ductus Arteriosus.

In the absence of irreversible pulmonary hypertension, closure of clinically detectable patent ductus arteriosus (PDA) is usually recommended in adults. Device closure obviates the need for general anesthesia and a surgical incision and eliminates postoperative pain, long convalescence, and lifelong scarring. Over the past 20 years, the efficacy and safety of transcatheter device closure of PDA in adults has been established. Even though the immediate success rate is lower with transcatheter device closure than with surgical closure, transcatheter reintervention for residual clinical shunts is very effective at abolishing residual leaks. The late complete closure rate, as determined by echocardiography, is very similar with surgical closure and with device closure. The clinical significance of silent residual shunts is unknown. In patients with silent residual shunts, the use of prophylactic antibiotics is as of yet recommended. Occlusion devices should be used whenever possible in adults, and surgical closure of patent ducts should be reserved for patients with larger ducts. The method of ductal closure should be selected on the basis of the quality of and experience with available interventional and surgical resources. Emerging minimally invasive surgical treatments seem promising, but further experience and follow-up are needed before widespread application of these techniques can be recommended.

Journal Article↗
PubMed1999

Resistivity and phase in localized BIA.

We describe a system for highly reproducible non-invasive rf impedance measurements as a function of position along body segments such as the thigh. Results are reported for mainly healthy male and female subjects ranging in age from 19 to 65 and in body-mass index from 15 to 40. A principal conclusion is that the phase of the impedance falls monotonically with increasing distance from the knee, with average values substantially above what is found using standard, whole-body bioelectrical impedance analysis (BIA). To compensate for thigh shape, the data are further analysed using an anatomical model based on reasonable approximations for the distributions of muscle, fat and bone, yielding values of the effective resistivity for current flow parallel to the muscle fibres. The phase and resistivity results are discussed with reference to the whole-body BIA study of maintenance haemodialysis patients by Chertow et al, and in regard to possible physiological correlations observed in this work.

Adult↗
PubMed1999

Reversal of protein losing enteropathy with prednisone in adults with modified fontan operations: long term palliation or bridge to cardiac transplantation?

Protein losing enteropathy (PLE), defined as severe loss of serum protein into the intestine, occurs in 4-13% of patients after the Fontan procedure and carries a dismal prognosis with a five year survival between 46% and 59%. Chronically raised systemic venous pressure is thought to be responsible for the development of PLE in these patients, with perhaps superimposed immunological or inflammatory factors. The success rate of contemporary medical, transcatheter, and surgical treatments attempting to reduce systemic venous pressure ranges from 19% to 40%. Prednisone treatment for PLE has been tried, with variable success rates reported in children. The effect of prednisone in adult patients with PLE after the Fontan procedure is largely unknown. Two cases of PLE in adults (a 39 year old woman and a 25 year old man) after modified Fontan procedure who responded dramatically to oral prednisone treatment are reported, suggesting that a trial of this "non-invasive" treatment should be considered as long term palliation or bridge to cardiac transplantation.

Adult↗