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Biomedical subjects

R M Freedom

Publications and source records attributed to R M Freedom.

At least 109 records · Page 6Linked to original sources
PubMed1995

Endovascular stents in the pulmonary circulation. Clinical impact on management and medium-term follow-up.

BACKGROUND: The use of endovascular stents to relieve obstructions in the setting of non-balloon dilatable pulmonary artery stenosis has been encouraging. The benefits in management and the potential for restenosis, however, have not been defined. This study attempts to assess the impact of such implants on clinical outcomes and the pattern of stent incorporation within the vessel wall. METHODS AND RESULTS: Fifty-five balloon-expandable stents were implanted in 42 patients 6.1 +/- 4.7 years of age. Patients were followed prospectively (median, 15 months) and recatheterized 1 year after implantation. Thirty-eight patients had the implants positioned percutaneously (49 implants), while 4 patients (6 implants) had intraoperative implantations. There was a diameter increase in the stenotic area of 109 +/- 79% (P < .0001) and a gradient reduction of 74 +/- 26% (P < .0001). Twelve stents straddled the orifice of side-branch pulmonary arteries and reduced flow to the branch vessel acutely in 7 patients. Twenty-nine patients underwent recatheterization, and various degrees and locations of acquired intraluminal narrowing were observed in all cases, particularly in areas of diameter mismatch between the stented and nonstented vessels. Eleven patients had further dilation with diameter improvement. Of the 38 patients who underwent percutaneous implantation, planned surgery for pulmonary artery stenosis was avoided in 33 and deferred in 4 patients. One patient who was considered inoperable had stent implantation as a palliative procedure. Symptomatic improvement was reported in 27 patients, and 15 patients remained asymptomatic. CONCLUSIONS: Endovascular stents have a role in the treatment of pulmonary artery stenoses and positively affect clinical care. The stenosis relief, however, may be tempered by the development of intraluminal stent obstruction, which may require redilation (15 of 55 stents) and mandates long-term follow-up.

Adolescent↗
PubMed1995

Chaotic atrial rhythm in children.

Chaotic atrial rhythm (CAR) usually occurs as a sequela of chronic obstructive lung disease in adults. We report the clinical manifestations and response to therapy in nine children with CAR treated predominantly with propafenone or amiodarone. Age at presentation ranged from 1 day to 30 months; six patients were < or = 2 weeks old. Six patients had tachycardia, and three had congestive heart failure. The atrial rate was 200 to 500 (mean 369 +/- 71) beats/min and the ventricular rate 150 to 300 (mean 251 +/- 37) beats/min. Eight patients had cardiac abnormalities. Intravenous drug therapy was not successful in converting CAR to sinus rhythm in any patient. A mean of four (range three to five) drugs was used in each patient; amiodarone and propafenone, alone or in combination, proved most successful. Seven patients were discharged from the hospital: full control was achieved in three (digoxin and amiodarone in two and digoxin, amiodarone, and procainamide in one), good control in three (digoxin, amiodarone, and propafenone in two and digoxin and propafenone in one), and ventricular rate control in one (digoxin, amiodarone, and propafenone). Two neonates with hypertrophic cardiomyopathy died. Long-term follow-up showed that CAR had resolved in five patients but persisted in two. We conclude that CAR remains difficult to control despite the use of newer antiarrhythmic agents but may resolve during long-term follow-up.

Amiodarone↗
PubMed1995

Reoperation for recurrent aortic coarctation.

BACKGROUND: Recurrence of stenosis is a complication of coarctation repair associated with major long-term morbidity. Persistent or exercise-provoked hypertension may indicate recurrent coarctation. Patients failing or not amenable to balloon dilation should be managed surgically. METHODS: A retrospective chart review was performed. RESULTS: Forty-three patients were identified as having undergone repeat surgical intervention for recurrent aortic coarctation between the years 1976 and 1993 at The Hospital for Sick Children in Toronto. Seventy percent of the children had other congenital cardiac anomalies. Eighty-six percent of patients initially treated by subclavian flap aortoplasty or end-to-end anastomosis were managed at reoperation by patch aortoplasty, and 26% of patients also required augmentation of the transverse arch (under hypothermic circulatory arrest) for accompanying hypoplasia. Three patients underwent a second reoperation; all were treated at this reoperation with tube graft interposition. CONCLUSIONS: No ischemic spinal injury occurred in patients managed with either simple proximal aortic cross-clamping or cardiopulmonary bypass. No patient treated with transverse arch augmentation required further surgical intervention. Mortality at reoperation was 7% (3 patients), similar to that of first-time coarctation repair. At follow-up (mean duration, 4.5 years), 57% of patients are normotensive, with no measurable arm-leg gradient.

Adolescent↗
PubMed1995

Subaortic stenosis in the spectrum of atrioventricular septal defects. Solutions may be complex and palliative.

UNLABELLED: From July 1982 through September 1994, 19 children had operative treatment of subaortic stenosis associated with an atrioventricular septal defect. Specific diagnosis were septum primum defects in 7, Rastelli type A defects in 6, transitional defects in 4, inlet ventricular septal defect with malattached chordae in 1, and tetralogy of Fallot with Rastelli type C defect in 1. Twenty-seven operations for subaortic stenosis were performed. Surgical treatment of the outlet lesion was performed at initial atrioventricular septal defect repair in 3 children and in the remaining 16 from 1.2 to 13.1 years (mean 4.9 years, median 3.9 years) after repair. Eighteen of the 19 children had fibrous resection and myectomy for relief of obstruction. Seven children had an associated left atrioventricular valve procedure. One child received an apicoaortic conduit. Seven children (36.8%) required 8 reoperations for previously treated subaortic stenosis. Time to the second procedure was 2.8 to 7.4 years (mean 4.9 years). Follow-up is 0.4 to 14.0 years (median 5.6 years). Six-year actuarial freedom from reoperation is 66% +/- 15%. The angle between the plane of the outlet septum and the plane of the septal crest was measured in 10 normal hearts (86.4 +/- 13.7) and 10 hearts with atrioventricular septal defects (22.2 +/- 26.0; p < 0.01). The outflow tract can be effectively shortened, widened, and the angle increased toward normal by augmenting the left side of the superior bridging leaflet and performing a fibromyectomy. CONCLUSION: Standard fibromyectomy for subaortic stenosis in children with atrioventricular septal defects leads to a high rate of reoperation. Leaflet augmentation and fibromyectomy may decrease the likelihood of reoperation.

Adolescent↗
PubMed1995

Endovascular stents in pediatric cardiovascular medicine.

Acquired or de novo vascular obstructions can adversely affect the outcomes of management algorithms for children with congenital heart lesions. Although surgical repair is frequently feasible, some acquired or congenital obstructions are difficult to address in the operating theater. Discussed is the recent experience with endovascular stents to relieve such stenoses, and their impact on patient care.

Animals↗
PubMed1995

Right to left interatrial communications after the modified Fontan procedure: identification and management with transcatheter occlusion.

OBJECTIVE: To describe unusual venous communications from the right to the left atrium resulting in cyanosis after the modified Fontan procedure, and their management with transcatheter occlusion. METHODS: Between September 1992 and November 1994, eight patients were assessed for persistent cyanosis after a modified Fontan procedure. Desaturation was found to be caused by unusual venous shunts originating at atrial level, and transcatheter occlusion with either a double umbrella or coil was attempted. RESULTS: Three types of venous channels were identified. The first type of communication consisted of thin long tortuous channels originating from the right atrial wall, and draining into the left atrium through a capillary network. The second type of communication was in the superior anterior portion of the atrial baffle, incorporating the pectinate muscles of the right atrium, draining into the neoleft atrium. These channels were shorter and often fanned out into small vessels toward the right atrial appendage. In each instance, the shunts were in the superior suture line of a lateral tunnel modification of the Fontan procedure. The third type of communication originated from the inferior vena cava, connecting inferior phrenic veins to pericardial veins and subsequently to the left atrium, at or close to the ostium of the left pulmonary veins. Before device occlusion, the room air aortic oxygen saturation was 88(SD 4)% (range 84% to 94%), and increased to 95(3)% (range 91% to 100%) following occlusion (PL << 0.001). The mean right atrial pressure was 14(4)mm Hg and remained unchanged after occlusion. In six patients there was complete shunt obliteration, while in two both occluded with umbrella devices, a small residual leak persisted. No complication occurred during or immediately after catheterisation. CONCLUSIONS: Unusual venous communications can evolve after the Fontan procedure, resulting in the development or persistence of cyanosis. Some of these communications may be present preoperatively as normal veins draining into the right atrium, enlarging with the increased atrial pressure after surgery. These observations affect long term function after the Fontan procedure. Transcatheter occlusion of these communications is technically feasible and effective, although recurrence may occur.

Adolescent↗
PubMed1995

Endovascular stents in children under 1 year of age: acute impact and late results.

OBJECTIVES: To review efficacy and safety of endovascular stent implants in children < 1 year of age with congenital heart lesions. DESIGN: Retrospective study of patients in a tertiary care setting. PATIENTS: 26 children (median age of 4.7 months, range 2 days to 1 year) with various vascular obstructive lesions. INTERVENTION: Percutaneous or intraoperative implantation of balloon expandable endovascular stents. RESULTS: Optimal stent placement was obtained in 31 of the 37 deployed implants. Complications resulted primarily from stent malpositioning and one episode of bleeding at a puncture site. Stent implantation in three patients with a restrictive arterial duct allowed for patency and five patients with conduit stenosis had mean (SD) right ventricule to systemic artery pressure ratios falling from 0.99 (0.20) to 0.52 (0.18) (P < 0.05). In 10 patients with pulmonary artery stenosis, the mean vessel diameter increased from 2.8 (0.9) mm to 5.8 (1.4) mm (P << 0.001). No clinical improvement was seen in two patients because of diffuse hypoplasia of the pulmonary vessels. Nine of 10 patients with miscellaneous obstructive lesions improved clinically. Recatheterisation was performed in 19 patients (median 8 months, range 12 days to 28 months) and 11 patients required redilatation (17 stents). CONCLUSIONS: Stent implantation is technically feasible in infants and under specific circumstances may provide an alternative to surgical palliation or avoid reoperation. The long term impact on clinical course, however, involves further interventions directed at stent management.

Arterial Occlusive Diseases↗
PubMed1995

Determinants of success in pediatric cardiac patients undergoing extracorporeal membrane oxygenation.

BACKGROUND: The purpose of this retrospective study is to determine the possible predictors of successful cardiac recovery using extracorporeal membrane oxygenation (ECMO) and the practical limits of ECMO support. METHODS: Information was gathered on 31 consecutive children with myocardial failure who could not be resuscitated with other means and underwent ECMO at the Hospital for Sick Children before January 1994. RESULTS: Of the children who underwent ECMO as a means of cardiac rescue, 14/31 (45%) were weaned successfully. Two distinct groups of children were evident based on their initial indications for ECMO: those who had postcardiotomy myocardial dysfunction (n = 25) and those with cardiomyopathy or myocarditis (n = 6). Children with residual defects after cardiotomy (n = 10) did not survive ECMO. Four of the 6 children with cardiomyopathy or myocarditis were weaned successfully. In either group of patients ECMO support beyond 6 days failed to resuscitate the myocardium; all attempts to violate this "time barrier" in our study inevitably failed. CONCLUSIONS: Postcardiotomy residual defects are a contraindication to ECMO. If children with residual defects are excluded, successful weaning from ECMO can be achieved in almost 70%, with almost all recovery occurring with the first 6 days of ECMO.

Cardiac Catheterization↗
PubMed1994

Postoperative follow-up of fibromuscular subaortic stenosis.

OBJECTIVES: This study attempted to determine whether early subaortic resection at lower levels of obstruction reduces the rate of recurrence of subaortic stenosis or reduces secondary damage to the aortic valve, or both. BACKGROUND: Fibromuscular subaortic stenosis is a progressive condition, and at present it is unclear whether early operation reduces the recurrence rate along with decreasing the incidence of aortic insufficiency. METHODS: Thirty-seven patients with fibromuscular subaortic stenosis and no other significant cardiac abnormality who underwent open subaortic resection were evaluated. The preoperative, early and late postoperative catheterization or echocardiographic findings as well as the operative reports were reviewed. The median age at operation was 6.4 years (range 1.1 to 17.3). The entire group has been followed up postoperatively for a median of 5.2 years (range 1.1 to 11). Mean systolic gradients across the left ventricular outflow tract were used for the purpose of this study. RESULTS: There was a significant correlation between the preoperative mean systolic gradient and the incidence of preoperative aortic regurgitation and late postoperative aortic valve thickening as well as the incidence and degree of late postoperative aortic regurgitation. Late postoperative gradient and degree of aortic regurgitation correlated significantly with the follow-up interval. Aortic regurgitation was progressive in some patients despite subaortic resection. A preoperative mean gradient > 30 mm Hg provided a reasonable cutoff for the likelihood postoperatively of needing a reoperation, having a postoperative shelf, a thickened aortic valve, moderate aortic regurgitation or a gradient of > 10 mm Hg. CONCLUSIONS: Our results suggest that although early subaortic resection may not reduce the rate of recurrence of fixed subaortic stenosis, it is likely to reduce acquired damage to the aortic valve.

Adolescent↗
PubMed1994

Clinical efficacy and safety of intravenous Amiodarone in infants and children.

The effectiveness and safety of intravenous amiodarone in children are not well established. This study reviewed its use in 30 infants and children for life-threatening tachyarrhythmias: 18 patients (19 episodes) with supraventricular tachycardia, and 12 with ventricular tachycardia. Eighteen patients had structural heart defects with arrhythmias that occurred after surgery. The mean loading dose was 5 mg/kg infused over 1 hour, with a starting maintenance dose of 5 micrograms/kg/min. In 18 treatment episodes, amiodarone was used alone or in combination with digoxin. Thirteen patients received amiodarone combined with other antiarrhythmic agents. Intravenous amiodarone was effective or partially effective in 94% of patients, achieving a therapeutic effect in a median time of 1 day (range 1 hour to 5 days). The mean effective maintenance dose was 9.5 micrograms/kg/min (13.7 mg/kg/day), and median treatment duration was 5 days (range 1 to 30). Adverse effects occurred in 18 patients (58%), however none necessitated termination of amiodarone therapy. Potentially significant electrocardiographic abnormalities occurred in 5 patients during combination antiarrhythmic therapy with propafenone. Sinus bradycardia requiring temporary postoperative pacing occurred in 3 patients treated with amiodarone alone. Intravenous amiodarone used alone or in combination therapy is an effective treatment for resistant, life-threatening arrhythmias in infants and children. Combination drug therapy with propafenone must be used cautiously. Potential bradycardia pacing may be necessary during administration of amiodarone after surgery.

Adolescent↗
PubMed1994

Small aortic root in childhood: surgical options.

Aortic valve replacement in the pediatric population is complicated by the often complex nature of the left ventricular outflow tract obstruction. Techniques to enlarge the annulus frequently are necessary. From 1977 to 1991, 32 children underwent an annular enlargement procedure at The Hospital for Sick Children, Toronto. During this same era, 110 children underwent a total of 138 aortic valve replacements. Eleven had the annulus enlarged with a posterior patch technique and implantation of a valve (mechanical 8, porcine heterograft 2, homograft 1) ranging from 20 to 25 mm in diameter. Twenty-two children had an anterior annular enlargement (aortoventriculoplasty) and aortic valve replacement with a valve (mechanical 8, porcine 2, homograft 12) 12 to 27 mm in diameter. One child had a posterior patch enlargement performed, followed by a second operation involving anterior annular enlargement. There was one early death in the posterior annuloplasty group and one late death due to failure of a bioprosthetic valve. There were five hospital deaths in the anterior annuloplasty group (22%; 70% confidence interval [CI], 14% to 32%) and two late deaths. Actuarial survival for the 32 children was 78% (70% CI, 70% to 86%) at 5 years and 65% (70% CI, 48% to 82%) at 10 years after repair. Younger children (age less than 1 year) had a significantly worse survival at 5 years (33%; 70% CI, 14% to 52%) than older children (88%; 70% CI, 82% to 95%). The survivors are well, and no reoperations have been necessary because of the children's outgrowing their valve.

Adolescent↗
PubMed1994

Risk factors for atrial tachyarrhythmias after the Fontan operation.

OBJECTIVES: The purpose of this study was to define the incidence and risk factors for atrial tachyarrhythmias after the Fontan operation. BACKGROUND: Atrial tachyarrhythmias cause morbidity after the Fontan operation. Causative factors may be affected by the type of systemic to pulmonary connection. METHODS: The Fontan operation was performed in 270 consecutive patients between 1982 and 1992. The mean age at operation was 7.0 +/- 4.3 years. Direct atriopulmonary connection was used in 138 patients (51%), total cavopulmonary connection in 94 (35%) and right atrial to right ventricular connection in 38 (14%). RESULTS: Atrial tachyarrhythmias were seen early postoperatively in 55 patients (20%), preoperative atrial tachyarrhythmia being the only risk factor. Follow-up was achieved for 228 early survivors (97%) at a mean interval of 4.4 years. There were 20 late deaths. Late atrial tachyarrhythmias were noted in 29% of patients who received an atriopulmonary connection, 14% of those who received a total cavopulmonary connection and 18% of those who received a right ventricular connection (p < 0.02). Significant risk factors as determined by univariate and multiple logistic regression analysis were atriopulmonary connection type (odds ratio 0.40 for total cavopulmonary relative to atriopulmonary connection [p < 0.05] and 0.37 for right ventricular relative to atriopulmonary connection [p = 0.08]), longer follow-up interval (odds ratio 1.32 for each consecutive year [p < 0.002]) and atrial tachyarrhythmia in the operative period (odds ratio 6.31 [p < 0.0001]). CONCLUSIONS: Early postoperative atrial tachyarrhythmias, length of follow-up and atriopulmonary connection are significant independent risk factors for the presence of late atrial tachyarrhythmias.

Analysis of Variance↗
PubMed1994

Transcatheter patent ductus arteriosus occlusion: application in the small child.

OBJECTIVES: This study intended to evaluate application of transcatheter occlusion of the patent ductus arteriosus in children < 10 kg body weight. BACKGROUND: Transcatheter occlusion of the patent ductus arteriosus in the child weighing > 10 kg has been proved safe and effective. METHODS: We reviewed 74 consecutive patients weighing < 10 kg (median 8.1 kg, range 3.98 to 10) and aged 4 to 30 months (median 13 months) who underwent patent ductus arteriosus occlusion between June 1986 and November 1992. A modification of the delivery system to facilitate application in small children is described. RESULTS: A 12-mm device was implanted in 50 patients and a 17-mm device in 24. Three device embolizations occurred early in the experience, and one required removal because of hemolysis associated with a moderate residual shunt. One 17-mm device was removed at catheterization because of acute compromise to left pulmonary artery flow after implantation. Prevalence of residual shunting was 33% at 6 months, 20% at 12 to 18 months and 17% at 2-year follow-up and was not related to device, age, weight or size of the patent ductus. Altered flow to the left pulmonary artery was noted in seven patients (9.9%), with more significant compromise associated with the 17-mm device. CONCLUSIONS: Transcatheter patent ductus arteriosus occlusion is feasible in the small child < 10 kg, particularly with the use of a modified delivery system. However, implantation of a 17-mm device in this patient population may impair flow to the left lung and should be reserved for the symptomatic child.

Cardiac Catheterization↗
PubMed1993

Ventriculo-coronary arterial connections in pulmonary atresia with intact ventricular septum, and their influences on ventricular performance and clinical course.

To define the influence of ventriculo-coronary (VC) arterial connections on ventricular performance and late outcome, and associated wall motion abnormalities in patients with pulmonary atresia and intact ventricular septum, 21 patients aged > or = 6 months (mean 4.3 +/- 3.3 years, range 0.5 to 11.8) were reviewed. Ventricular volumes, mass, systolic functional variables and regional wall motion were measured using biplane ventricular cineangiography. Fourteen patients had VC connections, 11 of whom had coronary artery abnormalities. In comparing patients with VC connections and coronary abnormalities (group I) with those without coronary abnormalities (group II), no hemodynamic differences were observed, except the expected increased right-to-left ventricular systolic pressure ratio in group I (1.33 +/- 0.24 vs 0.72 +/- 0.50). Wall motion abnormalities were observed in 8 patients (7 in group I, and only 1 in group II [p < 0.05]). Ejection fraction in patients with abnormal wall motion was significantly lower (50 +/- 6% vs 57 +/- 7%; p < 0.05) and ventricular systolic pressure ratio significantly higher (1.46 +/- 0.16 vs 0.80 +/- 0.45; p < 0.05) than in those with normal wall motion. Five patients died during follow-up, all of whom had wall motion abnormalities. The findings suggest that patients with VC connections and coronary abnormalities have a higher incidence of wall motion abnormalities, which may reflect ongoing ischemia, and are at risk for late death.

Analysis of Variance↗
PubMed1993

Retrobronchial vertical vein in totally anomalous pulmonary venous connection to the innominate vein and its specific occurrence in right isomerism.

Recently, a case of right isomerism with totally anomalous pulmonary venous connection (TAPVC) to the innominate vein through a vertical vein that ascended in the mediastinum posterior to the left-sided main bronchus was encountered. This retrobronchial vertical vein that has not been described previously in patients with TAPVC to the innominate vein prompted the performance of a retrospective analysis of 44 cases with TAPVC to the innominate vein in which angiography had been performed. The 44 cases consisted of 36 patients with situs solitus, 7 with right isomerism, and 1 with left isomerism. The spatial relation of the vertical vein to the adjacent pulmonary artery and main bronchus could be defined in 41 cases. The vertical vein was retrobronchial in 4 of 5 cases with right isomerism in which the location of the vertical vein could be defined with certainty. No case with situs solitus or left isomerism was associated with a retrobronchial vertical vein. In all 4 patients with a retrobronchial vertical vein, angiographic evidence of obstruction of pulmonary venous drainage was present, and was due to an extrinsic bronchial compression in 2 and to an intrinsic narrowing of the vertical vein in 2.

Abnormalities, Multiple↗
PubMed1993

Transcatheter occlusion of the patent ductus arteriosus in the presence of mild isthmal hypoplasia.

Between January 1990 and February 1992, 5 asymptomatic patients were identified with hypoplasia of the aortic isthmus at the time of cardiac catheterization for closure of a small patent ductus arteriosus. Isthmal diameters measured from lateral aortograms were 62 +/- 11% of age-matched controls. All patients had a small communication occluded with a 12 mm device and remained asymptomatic at 6-30 months follow up. Residual shunting was demonstrated by color Doppler in 2 patients. No child has developed an arm-leg systolic blood pressure gradient or systemic hypertension. Following device placement, Doppler interrogation across the isthmus in 2 patients demonstrated a velocity shift of 2.1 m/s. Transcatheter occlusion of the patient ductus arteriosus associated with mild isthmal hypoplasia of the aortic arch appears safe and effective and does not result in a clinically significant impairment to isthmal flow in short-term follow-up.

Aortic Coarctation↗