A national network for the tele-education of Canadian residents in pediatric cardiology.

A trial of 11 video-conferenced teaching sessions for residents in pediatric cardiology was performed by the 7 training programs in Canada in order to share expertise in specialized areas, to expose trainees to educational telemedicine, and to acquaint residents with other programs and personnel. Topics included cardiac pathology, arrhythmias, magnetic resonance imaging, fetal physiology, pulmonary hypertension, and cardiomyopathy. The sessions were evaluated by 93 residents by questionnaire for content and technology. Session content was highly rated. Videoconference picture quality was highly rated, but sound quality and visual aids were rated as neutral or unsatisfactory by a significant minority, related to problems with several early sessions, subsequently corrected. 60% of respondents rated the videoconferences as good as live presentations. Presenters were generally satisfied although they required some adjustments to videoconferencing. The average cost per session was $700 Canadian. Videoconferencing of resident educational sessions was generally well accepted by most presenters and residents, and the trial has formed the basis for a national network. Adequate organizational time, and careful attention to audiovisual needs, are most important. Videoconference guidelines are suggested for presenters based on this experience.

Cerebral blood flow velocity during occlusive manipulation of patent ductus arteriosus in children.

Patent ductus arteriosus (PDA) with left-to-right shunting modifies the Doppler flow pattern of the intracranial circulation. The ability of increases in cerebral blood flow velocity (CBFV) to predict shunt resolution during PDA occlusion was evaluated. A 2 MHz transcranial Doppler (TCD) monitored diastolic and mean CBFV, plus the systolic/mean CBFV ratio in the middle cerebral artery from before (baseline) to immediately after PDA occlusion. Shunt resolution was verified by echocardiography and/or angiography. A minimum of 40% increase in diastolic-CBFV from baseline was considered successful resolution. Patients were age-stratified into group I (< 15 months; n = 23) and group II (> 15 months; n = 10). Thirty-three children were studied (age, 0.1 to 109 months) during surgical (n = 22) or coil occlusions (n = 11). Transcranial Doppler successfully identified shunt resolution in 78% of cases in group I, as compared to 0% in group II (p < 0.01). Identification rate decreased from 79% in cases of minimum ductal diameter of 3 mm (n = 19) to 21% in smaller ductuses (n = 14) (p < 0.01). Body weight and left-atrium size (p = 0.004) in group I and PDA diameter in group II (p = 0.02), were the only preoperative ductal parameters associated with diastolic-CBFV changes after ductus occlusion. Transcranial Doppler detects shunt resolution in infants with moderate to large PDAs.

Cerebral blood flow velocities monitored by transcranial Doppler during cardiac catheterizations in children.

Transcranial Doppler (TCD) was used to evaluate brain circulation during cardiac catheterizations in 32 children requiring pulmonary (n=10) or aortic balloon dilatations (n=2), ductus arteriosus coil insertions (n=5), or angiography (n=15). Cerebral blood flow velocity (CBFV) in the middle cerebral artery was measured before (baseline), during, and after each procedure (mean+/-95%ci). High-intensity transient signals (HITS) were also detected during these maneuvers. Balloon angioplasty decreased CBFV by 63+/-11% from baseline (P < 0.01). Shorter durations of the inflation cycle resulted in earlier CBFV recovery (r=0.78). During angiography, CBFV increased by 11+/-4% (P < 0.01) in all except one case that showed retrograde diastolic flow. Mean total HITS count was 44 (95%ci.limits: 27,74). These signals were more frequently found in septal defects or systemic arterial manipulations. Pediatric cardiac catheterization may impose transient fluctuations in brain perfusion as indicated by TCD, but their clinical implications are uncertain. CBFV changes during balloon angioplasty emphasize the importance of rapid inflation/deflation cycles. TCD can monitor such changes and evaluate preventive measures.

Systolic function of the univentricular heart: comparison of the Simpson's rule with acoustic quantification.

BACKGROUND: Acoustic quantification (AQ) is a new method of obtaining real-time information about systolic ventricular function. This method establishes a ;blood-tissue interface' and computes an intraventricular blood volume in real time to derive a beat to beat instantaneous ejection fraction. AQ assessment of systolic function has been reported previously in patients with normal cardiotypes and varying degrees of myocardial dysfunction. OBJECTIVE: To determine the potential utility of AQ in patients with abnormal ventricular morphology, in whom systolic function may be difficult to measure by traditional methods. PATIENTS AND DESIGN: Seventeen children (nine females) ranging in age from five days to 18 years (mean 6.9 years) with univentricular left ventricle heart morphology underwent a prospective and comparative echocardiographic study of ventricular function with the use of AQ and manual planimetry (single plane Simpson's rule). Imaging was done during steady state without sedation. Routine scan planes were performed, followed by repeat scanning of the univentricle from the apical four-chamber view in the AQ mode. Subsequently, manual planimetry using Simpson's rule was performed from an online graphical analysis package to measure systolic and diastolic frames from the conventional replay images. These data were used to calculate ejection fraction using standards previously established. The results were then compared with real-time AQ results. SETTING: Tertiary care referral center. RESULTS: Scan time for the combined standard and AQ imaging averaged 45 mins (range 35 to 65 mins). Measured ejection fraction by AQ and manual planimetry were 44 +/- 11% and 46 +/- 10%, respectively. Statistical analysis by repeated measures ANOVA with Bonferroni/Dunn correction (F = 0.6, df = 1,32, P = 0.44) demonstrated significant agreement between AQ and manual planimetry with an intraclass correlation coefficient of 0.93. Bland-Altman analysis was used to provide a graphic display of the clinical significance of differences in the comparison of the two methods of measurement. CONCLUSIONS: These findings support the use of AQ for continuous online determination of indexes of systolic function for patients with univentricular left ventricle morphology. The variability in the morphology inherently present within this group of patients results in a wider variability of determined ejection fraction. Particular attention must be directed to the technical aspects of image acquisition and AQ application to ensure accuracy.

Cardiopulmonary bypass with circulatory arrest in swine: echocardiographic evaluation of left ventricle function and pulmonary vein flow.

Complete two-dimensional echocardiography and Doppler flow studies were performed on 17 swine as part of an experimental protocol involving cardiopulmonary bypass with circulatory arrest. Indices of left ventricular function and pulmonary vein morphology and flow velocity were taken before (17/17) and after bypass (11/17). A total of 70 measurements were available for analysis. Doppler flow velocity within the right pulmonary vein was 0.5 +/- 0.06 m/sec and was 0.52 +/- 0.05 m/sec in the left pulmonary vein. The swine were found to have a marked reduction in left ventricle function compared with that in previous reports, though no statistical difference was seen between pre- and post-cardiopulmonary bypass studies (preoperative shortening fraction was 21 +/- 5% and ejection fraction was 41 +/- 8%; postoperative shortening fraction was 23 +/- 5% and ejection fraction was 42 +/- 7%). Swine with shortening and ejection fractions of < 20% were found to have more unstable hemodynamics during cardiopulmonary bypass.

Liposomal amphotericin B for postoperative Aspergillus fumigatus endocarditis.

A 10-month-old infant girl presented with Aspergillus fumigatus endocarditis localized to a Gore-Tex patch used as part of the repair for double-outlet right ventricle. A new liposomal preparation of amphotericin B combined with surgical vegectomy resulted in a successful outcome with no evidence of disease recurrence at 15 months' follow-up. Echocardiography provided an optimal modality for ongoing evaluation of therapeutic outcome.

Transcatheter stent implantation for recurrent pulmonary venous pathway obstruction after the Mustard procedure.

A 5 year old boy presented with obstruction of the pulmonary venous pathway four years after the Mustard procedure. A successful balloon dilatation of the pulmonary venous pathway was performed but the benefit was transient. Placement of a 10 mm balloon expandable intravascular stent across the recurrent stenosis resulted in complete relief of the obstruction with prompt resolution of the clinical signs. The delivery system was modified to facilitate stent delivery.

Transcatheter management of pulmonary venous pathway obstruction with atrial baffle leak following Mustard and Senning repair.

Two patients presenting with pulmonary venous baffle obstruction following Mustard or Senning repair of transposition of the great arteries were successfully treated with percutaneous balloon dilatation. At the time of baffle dilatation, a significant systemic to pulmonary venous Mustard baffle leak was successfully closed with a Rashkind ductal occluder device. Specific features pertaining to the morphology of the baffle defect that allowed successful catheter occlusion are discussed and compared to that found in a Senning patient. The important adjunctive role of transoesophageal echocardiography within the catheterization laboratory is emphasized.

Intravascular stent prosthesis for right ventricular outflow obstruction.

OBJECTIVES: This study was designed to assess the impact of implantation of balloon-expandable stents on right ventricular outflow obstruction in children with congenital heart disease. BACKGROUND: Intravascular stenting has been established as a useful treatment in adults with coronary and peripheral vascular disease. Its application in the treatment of infants and children with pulmonary, systemic and right ventricular conduit obstruction resistant to balloon angioplasty is limited. METHODS: A total of 24 stainless steel stents were implanted in 17 patients. Five stents were placed within right ventricular to pulmonary artery conduits, 17 in branch pulmonary arteries and 1 in an aortopulmonary collateral vessel. Follow-up time has ranged from 1 to 14 months, with 6 patients having hemodynamic and angiographic studies greater than 1 year after stent placement. The mean age at implantation was 7.4 +/- 5.6 years and the mean weight 33 +/- 16 kg. RESULTS: Optimal stent position was obtained in 22 of 24 implantations. In one patient the stent slipped from the delivery balloon and was left positioned in the inferior vena cava. No embolization or thrombotic event has been documented. Among patients with right ventricular to pulmonary artery conduit obstruction, the gradient was immediately reduced from 85 +/- 30 mm Hg to 35 +/- 20 mm Hg after stent implantation; however, three patients required conduit replacement because of persistent obstruction with elevated right ventricular pressures (82 +/- 16 mm Hg). In 10 of 11 patients with pulmonary artery stenosis, clinical improvement was noted in association with enlargement of vessel diameter by 92% +/- 90% (range 17% to 355%) and the gradient reduction of 22 +/- 24 mm Hg to 3 +/- 4 mm Hg. CONCLUSIONS: These data support the view that intravascular stenting will become an important adjunct in the management of children with congenital heart disease.

Clinical impact of balloon angioplasty for branch pulmonary arterial stenosis.

The clinical impact of percutaneous balloon angioplasty on the management of patients with native or postoperative pulmonary arterial stenosis was reviewed. Seventy-four patients underwent 110 angioplasty procedures. Mean age at dilation was 6.7 +/- 5.3 years (range 0.2 to 18.1), 17 patients were aged less than 1 year, mean follow-up was 37.7 +/- 22.8 months (range 16 to 96), and 34 patients (44%) had follow-up angiography. Pulmonary artery dilation was acutely successful in 53% of patients, 17% had recurrent stenosis, and 5% had complications. The impact on subsequent care was favorably influenced in 26 of 74 patients (35%) with either complete resolution of stenosis (n = 7), optimizing future surgical conditions (n = 14), reduction in right ventricular pressure by greater than 20% (n = 3), or improvement of ipsilateral lung perfusion (n = 2). No patient previously considered inoperable was subsequently considered suitable for surgical repair owing to the intervention. No correlation was found between success and cardiac diagnosis (p = 0.48), site of stenosis (p = 0.78), balloon-vessel ratio (p = 0.42), or whether the stenotic area consisted of native or synthetic material (p = 0.22). No predictive factors for success could be defined, and often there was only a transient clinical impact. Due to the low complication risk and potential for a beneficial result, it still appears prudent to offer angioplasty as an initial therapeutic modality in this setting.

Transcatheter occlusion of the persistently patent ductus arteriosus. Forty-month follow-up and prevalence of residual shunting.

BACKGROUND: Percutaneous closure of the persistently patent ductus arteriosus with the Rashkind prosthesis is an established effective therapeutic modality, although some patients are left with residual shunting. To evaluate this, a retrospective study of the prevalence of persistent shunting over a 40-month period in the first 190 patients was undertaken. METHODS AND RESULTS: All patients (male 45, female 145; mean age, 3.9 +/- 3.6 years; range, 5 months to 20 years) had serial clinical and color-flow echocardiographic follow-up at 6-12-month intervals (range, 6-40 months). Four patients required surgical removal of an embolized device, leaving a cohort of 186 patients in whom 196 procedures were performed, resulting in successful placement of 195 devices (43 17-mm [22%] and 152 12-mm [78%]). Complications occurred in seven of 195 procedures (3.6%). Nine of 10 attempted reocclusions (all with 12-mm devices) were successful. The prevalence of residual shunting was 38% at 1 year, 18% at 2 years, and 8% at 40 months. Patients with ductus measuring less than 4 mm had a higher success of initial occlusion. Thirty-four patients were left with residual shunting determined by color-flow Doppler study, but no anatomic or echocardiographic features were found predictive for residual shunting. All remain asymptomatic with 26 (76%) having no detectable murmur, two (6%) a continuous murmur, and six (18%) a systolic murmur. CONCLUSIONS: Catheter occlusion will obviate the need for surgery in the majority of patients presenting with persistently patent ductus arteriosus. Reocclusion has been found feasible in those with continuous murmurs (nine of nine) and should be offered early because it is unlikely for spontaneous closure to occur in this group. It appears prudent to follow those with small residual shunting because further spontaneous closure can occur.

A femoral vein-femoral artery loop technique for aortic dilatation in children.

Balloon aortic dilatation is now a recognized therapy for aortic stenosis in children. Using retrograde approaches with either single or double balloons, successful dilatation can be readily achieved, but with little control of balloon position across the valve. We describe a femoral vein-femoral artery loop technique via a transseptal approach which facilitates antegrade crossing of the stenotic aortic valve and allows optimal balloon control and simultaneous pressure gradient recording during the procedure.

Therapeutic monitoring and pharmacokinetic evaluation of procainamide in neonates.

Past experience with the disposition of procainamide hydrochloride (PA) in neonates is restricted to a single case study involving placental transfer. We studied aspects of PA pharmacokinetics in three neonates who received constant-rate infusion therapy. Results indicated that the total serum clearance of PA is similar to the adult value, but elimination half-lives of both PA and N-acetylprocainamide (NAPA) were slightly prolonged and volume of distribution was variable. Pharmacokinetic evaluations in a renally compromised neonate confirmed that total PA clearance and the renal clearance of both PA and NAPA were reduced, although not to the extent expected for the degree of renal impairment. Peritoneal dialysis was used concurrently and may have contributed to the elimination process. We believe that our experience provides important preliminary guidelines for the management of PA therapy in neonates.

Reocclusion for persistent shunting after catheter placement of the Rashkind patent ductus arteriosus occluder.

Between February 1986 and January 1989, 105 percutaneous catheter occlusions of patent ductus arteriosus were undertaken, with six patients having residual left-to-right shunting confirmed by colour-flow Doppler nine months to years after initial occlusion. Five of six had successful reocclusion by placement of a second 12 mm Rashkind device. All successful reocclusions had continuous murmurs. Colour-flow Doppler characterized residual shunting as a discrete jet coursing superior to the device in five and through the pods in one. No left pulmonary artery obstruction was detected following placement of the second device. All patients were discharged the day of or the day following reocclusion.

Serial measurements of cerebral blood flow velocity in preterm infants during the first 72 hours of life.

Serial measurements of cerebral blood flow velocity (CBFV) were made in 29 preterm infants, using continuous wave Doppler ultrasound. CBFV was measured in both anterior cerebral arteries and quantitative measurements of CBFV were determined using the area under the velocity curve. In all ventilated infants, CBFV increased significantly during the first 6 hours of life and continued to increase until 16 hours of age. Thereafter, CBFV remained relatively constant. This increase in CBFV was primarily the result of increased diastolic flow. Three infants who had evidence of intraventricular haemorrhage on cranial ultrasound, had similar CBFV compared with the infants with no evidence of haemorrhage. Two infants died and both demonstrated areas of periventricular leukomalacia at autopsy. These infants had a prolonged period of low CBFV. These measurements provide normal data for ventilated, preterm infants. As previously suggested in term infants, the initial rise in CBFV may be secondary to closure of the ductus although a generalized decrease in peripheral vascular resistance could also be a contributing factor. Fluctuations in CBFV rather than individual readings are probably more important in the genesis of IVH. An episode of significantly reduced CBFV is a poor prognostic sign.