Gilles Ducharme
Université de Montréal
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Journal of the American College of Cardiology | 1993
David Radzik; André Davignon; Nicolaas H. van Doesburg; Anne Fournier; Thérèse Marchand; Gilles Ducharme
OBJECTIVES To establish the rate of spontaneous closure of atrial septal defects diagnosed before age 3 months, 101 infants (mean age 26 days) with an interatrial shunt confirmed by Doppler echocardiography were followed up for an average of 265 +/- 190 days. BACKGROUND Even if interatrial shunts in the newborn are frequently encountered, little is known about their natural history. METHODS Defect diameter on two-dimensional echocardiography and width of color flow jet were measured in the subcostal view. Right and left ventricular diameters and atrial septal curvature were also studied. Kaplan-Meier curves were obtained to predict age of spontaneous closure in relation to initial defect diameter. RESULTS There was no significant correlation between the diameter of the atrial septal defect and right ventricular/left ventricular ratio or type of septal curvature (vertical or concave toward the left atrium). The classic predominance of girls over boys was observed only for defects > 5 mm. An overall rate of spontaneous closure of 87% was observed. Frequency and timing of closure were inversely correlated to atrial septal defect diameter: closure occurred in 100% (32 of 32) of defects in group 1 (diameter < 3 mm), 87% of defects (39 of 45) in group 2 (diameter 3 to 5 mm), 80% of defects (16 of 20) in group 3 (diameter 5 to 8 mm). Spontaneous closure did not occur in four patients of group 4 (defect > or = 8 mm) during an average follow-up interval of 417 days (range 294 to 597 days). CONCLUSIONS These results suggest that infants with an atrial septal defect < 3 mm need not be followed up as 100% of these defects will be closed by age 18 months; those with a defect 3 to 5 or 5 to 8 mm should be evaluated by the end of the 12th and the 15th month, respectively, when > 80% of these defects will be closed. An atrial septal defect with a diameter > or = 8 mm may have little chance of closing spontaneously and the possibility of surgical correction should be considered. Defects < 3 mm probably do not constitute a cardiac malformation in light of their natural evolution and gender distribution.
American Journal of Cardiology | 1990
Guy Vaksmann; Anne Fournier; André Davignon; Gilles Ducharme; Lucile Houyel; Jean-Claude Fouron
Two hundred twenty-four consecutive patients operated on for tetralogy of Fallot were followed from 1 to 28 years (mean 11). Mean age at surgery was 5.3 years (range 1 to 14). Postoperative right ventricular systolic pressure was 60 mm Hg in 19 of 213 patients (9%). Fourteen patients (6%) had ventricular premature complexes on surface electrocardiograms. Seventy-nine patients underwent treadmill exercise tests, and ventricular premature complexes were induced in 17 (22%). Twenty-four-hour ambulatory monitoring in 92 patients demonstrated significant ventricular arrhythmias (greater than or equal to grade 2 of the Lown classification) in 41 (45%). The frequency of ventricular arrhythmias correlated with length of follow-up and duration of cardiopulmonary bypass. No correlation was found with age at surgery, postoperative right ventricular systolic pressure and importance of conduction defects on electrocardiogram. There were no sudden or unexpected deaths during follow-up.
Communications in Statistics-theory and Methods | 1989
Robert Ctéroux; Gilles Ducharme
A measure of multivariate correlation between two sets of vectors is considered when the underlying joint distribution is a member of the class of elliptical distributions. Its asymptotic distribution is derived under different situations and these results are used to test hypotheses on vector correlation when the underlying joint distribution is non-normal.
Journal of Cardiovascular Pharmacology | 1992
Lucile Houyel; Anne Fournier; Gilles Ducharme; Claude Chartrand; André Davignon
Sotalol is a beta-blocker with class III antiarrhythmic properties that has recently been used in children for the treatment of supraventricular and ventricular arrhythmias. However, little is known about its electrophysiologic effects on the immature heart. Using intracardiac electrocardiographic recordings and stimulation techniques, 15 canine neonates (8-15 days) and 15 adult mongrel dogs were studied with cumulative doses of sotalol (0.5, 1, 2, and 4 mg/kg plus an additional dose of 8 mg/kg for neonates). Heart rate decreased significantly in the two groups, but more in adult dogs (-43% in adult dogs versus -25% in neonates, p less than 0.05). There was no significant change for QRS duration and His-Purkinje system conduction time interval. QT and atrioventricular nodal conduction time intervals increased in adult dogs and neonates. Sinus node recovery time increased significantly in the two groups, but more in adult dogs. Refractory periods of the atrioventricular (AV) node increased significantly in neonates. Atrial flutter was no longer inducible in 12 of 15 neonates after the 2 mg/kg dose. Atrial effective refractory period increased significantly more in neonates (96%, p less than 0.001) than in adult dogs (58%, p less than 0.001). Ventricular effective refractory periods increased significantly both in neonates (46%) and adult dogs (50%), in a similar way. In conclusion, sotalol has greater electrophysiologic effects on the immature heart at the atrial level when compared to the adult, and similar effects on the refractory period of AV node and ventricle.
The Journal of Pediatrics | 1985
Josée S. Lafond; Jean-Claude Fouron; Harry Bard; Gilles Ducharme
To determine whether acute alcohol ingestion during pregnancy could affect fetal myocardial function, studies were carried in six chronically catheterized fetal sheep during maternal alcohol infusion. Absolute ethyl alcohol (0.8 ml/kg) was administered to the mother over 10 minutes via the jugular vein. These infusions were repeated every 30 minutes during 3 hours, and peak maternal and fetal blood concentrations close to 200 mg/dl alcohol were reached. Fetal PCO2 decreased from a baseline of 43.15 +/- 3.75 to 36.13 +/- 2.6 torr 1 hour after the start of alcohol infusion (P less than 0.05). Similarly, pH rose from 7.37 +/- 0.027 to 7.44 +/- 0.015 (P less than 0.05). Both values returned to baseline level at the end of alcohol infusion. PO2 remained within physiologic limits. The systolic time intervals of the fetal heart showed a rapid and prolonged modification. The pre-ejection period from 58 +/- 8 to 66 +/- 4 msec (P less than 0.05) during the infusion; this change was related to an increase in the isometric contraction period. The ratio of the pre-ejection period over the ejection time was also significantly increased (P less than 0.01), and remained elevated until the end of the experiment (12 hours). A rise in fetal systolic and diastolic pressures was observed at about 2 hours after the start of the alcohol infusion, and lasted 4 hours. This study suggests that an episode of maternal alcohol intoxication causes rapid depression of fetal myocardial contractility that is maintained several hours after cessation of alcohol ingestion.
Communications in Statistics-theory and Methods | 1987
Gilles Ducharme; Philip Milasevic
In this article, the asymptotic distribution of the circular median is derived for symmetric distributions on the circle. Its asymptotic relative efficienty with respect to the mean direction and to an estimator proposed by Watson (1983) is then examined. Special attention is given to the cases where the underlying distribution is von Mises and contaminated von Mises. It is seen that the circular median can perform more efficiently than both estimators in presence of outliers.
Neonatology | 1988
Jean-Claude Fouron; François Heitz; Anna-Maria Carceller; Gilles Ducharme; Nicolaas H. van Doesburg; André Davignon
UNLABELLED In order to assess possible changes in myocardial relaxation occurring during the neonatal period, M-mode echocardiograms were recorded serially in 9 normal term infants and in another group of 10 one-month-old infants. The tracings were studied with an M-mode calculator. Although individual variations were greater in the data collected during the first 24 h, no significant difference was found in the indices of diastolic function of the left ventricle during the first 4 days of age. The following changes were observed between data recorded at 4 days and 1 month, respectively: normalized peak rate of left ventricle filling, 4.03 vs. 4.71 cm/s; diastolic peak velocity of early posterior motion of aortic root, 1.89 vs. 5.15 cm/s; peak velocity of left ventricle posterior wall motion in diastole, 3.31 vs. 3.50 cm/s; mitral valve EF slope, 59.05 vs. 84.92 mm/s; left ventricle isometric relaxation time, 43.88 vs. 28.50 ms. IN CONCLUSION (1) greater individual variations are observed in indices of left ventricle diastolic function during the first day of life, and (2) significant increase in left ventricle compliance occurs during the first month of life. These changes should play a critical role in the clinical course of newborn with cardiopulmonary disease.
Circulation | 1986
Ana-Maria Carceller; Jean-Claude Fouron; Jeffrey F. Smallhorn; Jl Cloez; N H van Doesburg; Pierre Mauran; Gilles Ducharme; C Pernot; André Davignon
Fifty-one patients with uncomplicated transposition of the great arteries (TGA) and normal pulmonary pressure who were 10 to 20 years old and 69 normal subjects matched for age were studied by M mode echocardiography. Left ventricular internal dimensions and posterior wall thickness showed positive correlation with the body surface area in the TGA as well as in the control groups. Values for these parameters in the TGA group were generally smaller than those in the normal population. Septal thickness of patients with TGA (5.9 +/- 1 mm) was also smaller than that in the control group (6.6 +/- 1 mm) (p less than .01). Septal motion was normal in 11 patients with TGA and paradoxical in 19 patients in this group. In the other 21 patients the septum was flat. The following systolic time intervals of the left ventricle were found for patients with TGA: preejection period (PEP) 64 +/- 11 msec, ejection time (ET) 310 +/- 37 msec, and PEP/ET 0.21 +/- 0.04. These values were significantly different from those of the right ventricle for the normal population: PEP 77 +/- 12 (p less than .01), ET 327 +/- 25 (p less than .05), and PEP/ET 0.24 +/- 0.03 (p less than .01). Shortening fraction and mean velocity of circumferential fiber shortening (49 +/- 7% and 1.6 +/- 0.3 circ/sec, respectively) were also significantly higher (p less than .01) in patients with TGA than in the control group (33 +/- 4% and 1.1 +/- 0.2 circ/sec). These data should help achieve reliable quantitative and qualitative interpretations of echocardiograms of patients with TGA.
Journal of Theoretical Biology | 1992
Pierre Jolicoeur; Gilles Ducharme
Sampling experiments are done on the maximum likelihood estimator, k = tan ( f ), of the slope of the bivariate normal major axis, which is often used on log-transformed data to estimate allometry exponents. The slope tan ( f ) becomes highly variable in small samples from populations with low correslations. Moreover, the corresponding angle, f = arc tan ( k ), is biased toward zero because it has an axial distribution of which the axial mode is not situated at zero and in which angles falling outside of the [−90°, +90°] range are interpreted as narrower angles of the opposite sign. However, the usual notions of linear ( scalar ) average and bias are not appropriate for directional or axial data. If the axial distribution of angle f is transformed into a directional distribution by doubling angles, the vector of the numerators of the direction cosines of the doubled angle 2 f is unbiased, and the corresponding expected vector of direction cosines points in the proper direction to within order O( N −2 ). For the preceding reasons, the utilization of the usual estimators k = tan ( f ) and f = arc tan ( k ) may be considered as legitimate. Procedures are suggested for combining independent estimates of the slope of the major axis validly into a single estimate.
Annals of the Institute of Statistical Mathematics | 1994
Bernard Boulerice; Gilles Ducharme
Directional data analysis usually assumes that the observations are recorded according to a coordinate system whose origin coincides with the center of their support. However, it may happen that the observer does not sit at this center and record the directions from another point. The object of this paper is to investigate the statistical behavior of such decentered directions. First we derive the family of distributions of these directions and produce statistical procedures that recover some information about the underlying process. An important special case is explored in details and compared with the Langevin model. Finally, an example is given where the introduced family of models makes physical sense and well fits the observations.