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Biomedical subjects

D Nykanen

Publications and source records attributed to D Nykanen.

At least 19 recordsLinked to original sources
PubMed2003

Evolution of heart rate control after transplantation: conduction versus autonomic innervation.

In cardiac transplantation, the donor organ is not initially innervated and demonstrates decreased heart rate variability (HRV). However, HRV may improve after several months. The mechanism for HRV improvement has not been elucidated; autonomic "reinnervation" of the donor heart has been proposed. The role of atrioatrial conduction from recipient to donor organ has not been evaluated. We prospectively evaluated cardiac transplant patients with a limited electrophysiology study at the time of their surveillance biopsies. Recordings were made of recipient and donor signals, observing conduction properties between recipient and donor atria. Holter recordings were analyzed and HRV was determined using spectral analysis techniques, recording mean RR interval, low-frequency power (LF), high-frequency power (HF), and the LF/HF ratio. These were compared to published norms. From November 1999 to May 2000, 21 patients (6 female) who underwent cardiac transplantation participated at a median age of 101 months (range, 4.1-217 months). Time posttransplant ranged from 26 days to 71 months. Holter data were available for 20 patients and demonstrated dissociated P waves in 13 (65%). The mean heart rate on Holter was 111 beats per minute (bpm) (range, 85-161 bpm). We were able to record distinct recipient atrial signals in 16 of 21 (76%) patients. The average recipient tissue heart rate was 55% that of the donor heart rate. We documented atrioatrial association in only 1 patient. HRV did not reach normal values for most patients and did not increase with time posttransplantation. The LF values were in the normal range for most patients, whereas 3 patients had normal HF values and 2 patients had values just below normal. Recipients of heart transplantation have a predominantly sympathetic influence of HRV. These preliminary data suggest that atrioatrial conduction does not play a role in reestablishing normal heart rate control following pediatric cardiac transplantation.

Adolescent↗
PubMed2003

Transcatheter management of residual shunts after initial transcatheter closure of a patent arterial duct.

OBJECTIVES: To assess the efficacy and safety of transcatheter reocclusion of persistent leaks following previously attempted transcatheter occlusion of persistent arterial duct. DESIGN: Retrospective study. SETTING: Tertiary pediatric cardiology centre. PATIENTS: From February 1987 through October 1996, trans-catheter occlusion of a residual ductal shunt was attempted in 42 consecutive patients at a median age of 5.0 years (range 1.6 years to 16.2 years). INTERVENTIONS: Fourty patients had successful placement of a double umbrella occluder (n=27) or coils (n=13) across residual shunts. Complications included device embolization in two patients and hemolysis in one patient. OUTCOME MEASURES AND RESULTS: Mean z-score for left ventricular end-diastolic dimension (LVEDD) at initial echocardiography was +2.55 +/- 1.89 (P<0.0001 versus normal); z-score for left pulmonary artery (LPA) diameter was +2.00 +/- 1.52 (P<0.0001). Mean LPA to right pulmonary artery (RPA) diameter ratio was 1.05 +/- 0.18. At follow-up echocardiogram, a median of two years (range six months to 7.7 years) after the second procedure, a shunt was persistent in 3% of the patients. Mean LVEDD and LPA diameter z-value, and mean LPA to RPA diameter had dropped significantly to +0.42 +/- 1.31, +0.07 +/- 1.15 and 0.86 +/- 0.14 (P<0.001), respectively. LPA flow acceleration was present in 25% of patients. Three of nine patients, in whom lung perfusion scan was performed, had left lung perfusion below 40%. Small weight and age at catheterization were significant risk factors for LPA flow disturbance. CONCLUSIONS: Repeat transcatheter occlusion is safe and successful in eliminating residual shunt across the arterial duct. Attention should, however, be addressed to the potential for LPA stenosis and growth, and flow should be regularly assessed.

Adolescent↗
PubMed2001

Outcomes of transcatheter embolization in the treatment of coronary artery fistulas.

Thirteen children (seven male) with coronary artery fistula underwent percutaneous transcatheter occlusion. The age range was 8 months to 14 years (mean, 6.3 years). The fistulas had their origins from the right coronary artery (six), from the left anterior descending coronary artery (three), and from the left circumflex coronary artery (four). Drainage was to the right ventricle (seven), the right atrium (three), and one each to the pulmonary artery, left atrium, and superior caval vein. The fistulas were closed with coils in 10 patients, a Rashkind double-umbrella device in 1 patient, and an Amplatzer Duct Occluder in 2 patients. Complete occlusion was achieved in 9 of 13 patients. Complications consisted of migration of coils in four and transient arrhythmias or changes in the resting electrocardiogram in four patients. Follow-up studies 1 to 31 months (mean, 14.6 months) after occlusion noted only four patients with trivial (clinically insignificant) residual shunts. Owing to various coronary fistula morphologies, transcatheter occlusion requires availability of different embolization techniques. Short-term follow-up supports persistent clinical efficacy and transcatheter closure techniques as the initial form of therapy.

Adolescent↗
PubMed2001

Total cavopulmonary connections in children with a previous Norwood procedure.

BACKGROUND: Outcomes of the Fontan operation in children initially palliated with the modified Norwood procedure are incompletely defined. METHODS: From August 1993 to January 2000, 45 patients (mean age 2.6 +/- 1.1 years, weight 12.7 +/- 2.8 kg) who were palliated with staged Norwood procedures (hypoplastic left heart syndrome, n = 32; nonhypoplastic left heart syndrome, n = 13) underwent a modified Fontan operation. Preoperative features included moderate/severe atrioventricular valve regurgitation (n = 5, 11%), reduced ventricular function on echocardiography in 11 patients, McGoon index 1.56 +/- 0.38, and pulmonary artery distortion in 18 patients (40%). RESULTS: A lateral tunnel (n = 16) or an extracardiac conduit (n = 29) connection with fenestration in 38 patients (84%) was used. Concomitant procedures included pulmonary artery reconstruction (n = 24, 53%), atrioventricular valve repair (n = 4, 9%) or replacement (n = 1). Before Fontan, 12 patients (27%) had an intervention to address neoaortic obstruction, and 7 patients required balloon dilation/stenting of the left (n = 5) or right pulmonary artery (n = 5). Intraoperatively, left (n = 5) or right pulmonary artery (n = 1) stenting was performed in 5 patients (11%). On follow-up, 8 patients required additional interventional procedures to address left pulmonary artery narrowing (n = 5), or venous (n = 5) or arteriopulmonary collaterals (n = 1). Perioperative mortality was 4.4% (n = 2). There were 2 late deaths at a mean follow-up of 39 +/- 20 months. CONCLUSIONS: In relatively high-risk patients, midterm results of the Fontan operation for children initially palliated with the Norwood procedure were good. Combined interventional-surgical treatment algorithms can lead to improved outcomes.

Child↗
PubMed2001

Outcomes of intraoperative device closure of muscular ventricular septal defects.

BACKGROUND: The surgical management of muscular ventricular septal defects (mVSD) in the small infant is a challenge particularly when multiple and associated with complex cardiac lesions. Devices for percutaneous implantation have the advantage of ease of placement and for the double umbrella designs a wide area of coverage. We reviewed our experience and clinical outcomes of intraoperative mVSD device closure for such defects in small infants. METHODS: Since October 1989, intraoperative VSD device closure was a component of the surgical strategy in 14 consecutive patient implants (median age, 5.5 months; range, 3 to 11 kg), whose defects were thought difficult to approach using conventional techniques. Nine patients had associated complex cardiac lesions, 10 multiple mVSDs, and 4 patients had a previous pulmonary artery banding. RESULTS: There were 2 early deaths, 1 in a severely ill child who preoperatively had pulmonary hypertension and left ventricular failure and another in a patient with a hypoplastic left heart. Mean pulmonary to systemic flow ratio before device insertion was 3.5:1. Complete closure was achieved in 5 patients and clinically insignificant residual shunts persisted in 7. In 2 infants with significant residual lesions concomitant pulmonary artery banding was required. Postoperative mean pulmonary to systemic flow ratio was 1.7:1. In follow-up of the 12 surviving infants (mean, 41 months), 8 had complete closure and 3 persistent residual shunts. One patient with no residual shunting required heart transplantation for progressive ventricular failure 9 years after operation. All devices were well positioned on postoperative echocardiograms. There was 1 late death due to aspiration in a patient with a tiny residual shunt. CONCLUSIONS: Infants requiring operative intervention with mVSDs are difficult to manage and have an increased mortality and morbidity. Intraoperative VSD device placement for closure of mVSDs is feasible, can avoid ventriculotomy, division of intracardiac muscle bands, and is ideally suited for the neonate or infant.

Echocardiography↗
PubMed2001

The effect of implantation of aortic stents on compliance and blood flow. An experimental study in pigs.

Balloon dilation of coarctation of the aorta has been found to be an effective modality for treatment. Recently, in the older child and adult, implantation of endovascular stents has been considered a clinical alternative to dilation alone. Little is known, however, of the effect of implantation of stents on aortic compliance. To investigate this impact of implantation, we studied 18 piglets, divided into experimental and control groups. At median weight of 14 kg, 2 pairs of ultrasonic crystals were implanted on the aortic wall. After 1 week, all animals underwent catheterization. In the experimental group, a 3 cm long balloon expandable stent was implanted in the descending thoracic aorta between the pairs of crystals. Measurements of arterial pressure and dimensions were performed before implantation and immediately thereafter, and at follow-up catheterization. The index of stiffness, beta, and the the elastic modulus of aortic pressure-strain, were calculated as indexes of arterial compliance. The change in compliance during the period of study was not different between groups. At follow-up, no difference was observed between groups in the velocity of the aortic pulse wave, the augmentation index, or the maximum velocity of flow of blood. The stents remained patent and did not affect aortic growth or medial wall thickness. There was no difference between groups in levels of plasma renin activity and serum aldosterone. In this animal model studied over the short term, therefore, implantation of stents does not affect aortic compliance. Further studies are required to elucidate the long term effects of stents on the hemodynamics affecting the aortic wall and local flow dynamics.

Animals↗
PubMed2001

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.

Canada↗
PubMed2000

Balloon angioplasty of native coarctation: clinical outcomes and predictors of success.

OBJECTIVES: We sought to investigate the clinical impact of balloon angioplasty for native coarctation of the aorta (CoA) and determine predictors of outcome. BACKGROUND: Balloon dilation of native CoA remains controversial and more information on its long-term impact is required. METHODS: Hemodynamic, angiographic and follow-up data on 69 children who underwent balloon angioplasty of native CoA between 1988 and 1996 were reviewed. Stretch, recoil and gain of CoA circumference and area were calculated and related to outcomes. RESULTS: Initial systolic gradients (mean +/- SD, 31+/-12 mm Hg) fell by -74+/-27% (p < 0.001), with an increase in mean CoA diameters of 128+/-128% in the left anterior oblique and 124+/-87% in the lateral views (p < 0.001). Two deaths occurred, one at the time of the procedure and one 23 months later, both as a result of an associated cardiomyopathy. Seven patients had residual gradients of >20 mm Hg. One patient developed an aneurysm, stable in follow-up, and four patients had mild dilation at the site of the angioplasty. Freedom from reintervention was 90% at one year and 87% at five years with follow-up ranging to 8.5 years. Factors significantly associated with decreased time to reintervention included: a higher gradient before dilation, a smaller percentage change in gradient after dilation, a small transverse arch and a greater stretch and gain, but not recoil. CONCLUSION: Balloon dilation is a safe and efficient treatment of native CoA in children. Greater stretch and gain are factors significantly associated with reintervention, possibly related to altered elastic properties and vessel scarring.

Angioplasty, Balloon↗
PubMed2000

Implantation of endovascular stents for hypoplasia of the transverse aortic arch.

Hypoplasia of the transverse aortic arch is commonly associated with aortic coarctation. Persistent or recurrent obstruction can occur at this level after successful repair of the native coarcted segment. The purpose of this report is to present a new technique to treat such lesions, namely with implantation of a balloon-expandable stent. This approach was used successfully in 4 children with such hypoplasia occurring after repair of coarctation. Implantation led to both anatomical and physiological relief of obstruction in all. The patients tolerated the procedure, and there were no major adverse events.

Adolescent↗
PubMed1999

Endovascular stent implantation to relieve extrinsic right pulmonary artery compression due to an enlarged neoaorta.

This case report describes extrinsic compression of the right pulmonary artery, following aortic reconstructive surgery, to create a neo-ascending aorta in a 5-year-old boy with aortic atresia, coarctation of the aorta, and a ventricular septal defect, in an effort to achieve a biventricular circulation (Yasui operation). The obstruction was successfully relieved by transcatheter implantation of a balloon-expandable stent.

Aorta↗
PubMed1999

Stent implantation to create interatrial communications in patients with complex congenital heart disease.

A restrictive interatrial communication can complicate the management of complex congenital heart disease. The purpose of this report is to present a new technique to achieve a patent and reliable interatrial communication by using an endovascular stent. A stent was successfully implanted across a fenestrated extracardiac conduit in two patients with low cardiac output after Fontan operations and across the interatrial septum in a patient with double inlet left ventricle and severe left atrioventricular stenosis. The procedures were uncomplicated and all patients showed immediate hemodynamic improvement. Cathet. Cardiovasc. Intervent. 47:310-313, 1999.

Child, Preschool↗
PubMed1999

Endovascular stent implantation for the management of postoperative right ventricular outflow tract obstruction: clinical efficacy.

OBJECTIVE: Extracardiac conduits between the right ventricle and pulmonary arteries commit patients to multiple reoperations. We reviewed our experience with stent implantation in obstructed conduits. METHODS: Between 1990 and 1997, stents were implanted across 43 conduits. The median age at procedure was 6 years (0.5-17 years), and the median interval between conduit insertion and stent implantation was 2.4 years (0.3-14 years). RESULTS: Mean systolic right ventricular pressures and gradients, respectively, decreased from 71 +/- 18 mm Hg and 48 +/- 19 mm Hg before to 48 +/- 15 mm Hg and 19 +/- 13 mm Hg after stent placement. Mean percentage of predicted valve area for body surface area increased from 26% +/- 12% to 48% +/- 17% after stent placement. Fifteen patients underwent a second transcatheter intervention (dilation or additional stent), and 2 patients, a third, allowing further postponement of surgery in 8 patients. One sudden death occurred 2.8 years after stent placement. Surgical conduit replacement has occurred in 20 patients. Body growth was maintained during follow-up. Freedom from surgical reintervention was 86% at 1 year, 72% at 2 years, and 47% at 4 years. Higher right ventricular pressure and gradient before and after stent placement and lower percentage of predicted valve area for body surface area after stent placement were associated with shorter palliation. CONCLUSION: Endovascular stent placement across obstructed conduits is a safe and effective palliation that allows for normal body growth.

Cardiac Catheterization↗
PubMed1999

Interventional cardiac catheterization.

Over the past decade, transcatheter interventions have become increasingly important in the treatment of patients with congenital heart lesions. These procedures may be broadly grouped as dilations (e.g., septostomy, valvuloplasty, angioplasty, and endovascular stenting) or as closures (e.g., vascular embolization and device closure of defects). Balloon valvuloplasty has become the treatment of choice for patients in all age groups with simple valvar pulmonic stenosis and, although not curative, seems at least comparable to surgery for congenital aortic stenosis in newborns to young adults. Balloon angioplasty is successfully applied to a wide range of aortic, pulmonary artery, and venous stenoses. Stents are useful in dilating lesions of which the intrinsic elasticity results in vessel recoil after balloon dilation alone. Catheter-delivered coils are used to embolize a wide range of arterial, venous, and prosthetic vascular connections. Although some devices remain investigational, they have been successfully used for closure of many arterial ducts and atrial and ventricular septal defects. In the therapy for patients with complex CHD, best results may be achieved by combining cardiac surgery with interventional catheterization. The cooperation among interventional cardiologists and cardiac surgeons was highlighted in a report of an algorithm to manage patients with tetralogy of Fallot or pulmonary atresia with diminutive pulmonary arteries, involving balloon dilation, coil embolization of collaterals, and intraoperative stent placement. In this setting, well-planned catheterization procedures have an important role in reducing the overall number of procedures that patients may require over a lifetime, with improved outcomes.

Adolescent↗
PubMed1998

The physiology of the bidirectional cavopulmonary connection.

This article reviews the indications for the bidirectional cavopulmonary connection and demonstrates its efficacy in reducing mortality for the Fontan procedure. The indications for adding an additional source of pulmonary blood flow to the bidirectional cavopulmonary connection are discussed, but this issue remains controversial. Also unclear is whether the bidirectional cavopulmonary connection promotes symmetric growth of the pulmonary arteries, or whether growth of the left pulmonary artery is disadvantaged. Finally, systemic venous collateralization is a well-recognized sequel after cavopulmonary connection. The clinical implications of this collateralization are reviewed.

Anastomosis, Surgical↗
PubMed1998

Complications associated with pediatric cardiac catheterization.

OBJECTIVES: The aim of this study was to determine the relative risks of pediatric diagnostic, interventional and electrophysiologic catheterizations. BACKGROUND: The role of the pediatric catheterization laboratory has evolved in the last decade as a therapeutic modality, although remaining an important tool for anatomic and hemodynamic diagnosis. METHODS: A study of 4,952 consecutive pediatric catheterization procedures was undertaken. RESULTS: Patient ages ranged from 1 day to 20 years (median 2.9 years). One or more complications occurred in 436 studies (8.8%) and were classified as major in 102 and minor in 458, with vascular complications (n=189; 3.8% of procedures) the most common adverse event. Arrhythmic complications (n=24) were the most common major complication. Death occurred in seven cases (0.14%) as a direct complication of the procedure and was more common in infants (n=5). Independent risk factors for complications included a young patient age and undergoing an interventional procedure. CONCLUSIONS: Complications continue to be associated with pediatric cardiac catheterization. Efforts should be directed to improving equipment for flexibility and size, and finding alternative methods for vascular access. Patient age and interventional studies are risk factors for morbidity and mortality.

Adolescent↗