Cost effectiveness of neonatal ECG screening for the long QT syndrome.
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Cohort Studies↗
Biomedical subjects
John K Triedman
Publications and source records attributed to John K Triedman.
Cryoablation for accessory pathways located near normal conduction tissues or within the coronary venous system in children and young adults.
BACKGROUND: Cryoablation may offer advantages over radiofrequency (RF) ablation for certain arrhythmia substrates, such as septal accessory pathways (APs). Data for young patients, especially regarding recurrence risk, require expansion. OBJECTIVES: The purpose of this study was to study institutional outcomes for cryoablation of APs located in potentially difficult septal regions for children and young adults. METHODS: Cryoablation was attempted in 35 young patients (mean age 15.6 years) with 37 APs that were either close to normal conduction tissues or inside the coronary venous system. Outcomes were compared with previously published institutional data for RF ablation at these same locations. RESULTS: Acute cryoablation success was achieved for 29 (78%) of 37 APs. Apart from permanent PR prolongation in one case and right bundle branch block in one other, there were no detrimental effects on normal conduction. At median follow-up of 207 days (range 2-695 days), AP conduction recurred for 13 (45%) of 29 ablated APs. Younger patient age and midseptal AP location correlated with higher likelihood of recurrence. Acute success rates for cryoablation were similar to RF ablation in our laboratory, but recurrence rates were significantly higher (P <.001). CONCLUSION: Cryoablation yields acute success rates comparable with RF ablation for difficult septal APs in young patients. The risk of AP recurrence appears higher after cryoablation, although safety benefits may provide suitable compensation for this deficiency. Methods for creating more effective cryoablation lesions need to be explored.
Adolescent↗
Producing diffuse ultrasound reflections from medical instruments using a quadratic residue diffuser.
Simultaneous visualization of tissue and surgical instruments is necessary during ultrasound-guided medical procedures. Standard minimally invasive instruments are typically metallic and act as strong specular scatterers. As a result, such instruments saturate the image or disappear according to the angle of incidence, obscuring nearby tissue and making it difficult to determine the instrument's precise location. The objective of this study was to produce diffusive reflections from the surface of surgical instruments for improved visualization in ultrasound. A surface profile based on a 2D quadratic residue diffuser (QRD) was employed, which has been demonstrated to reduce specular reflection in other acoustic applications. The backscattered echo amplitude from the diffusive surface at various angles of insonation was measured and compared to that from unmodified metal surfaces and heart tissue surfaces. The QRD resulted in an 8 dB reduction of the specular signal. Furthermore, the dynamic range for angles up to 75 degrees was less than 20 dB for the QRD and more than 65 dB for a flat surface. The QRD surface produces two beneficial results for the simultaneous imaging of instruments and tissue. First, the conspicuity of diffusive surfaces in ultrasound images is markedly improved in comparison with unmodified metal surfaces. Secondly, the echo amplitude of diffusive metal surfaces differs in mean and standard deviation from that of tissue facilitating image enhancement and segmentation.
Acoustics↗
Ablation of nonautomatic focal atrial tachycardia in children and adults with congenital heart disease.
INTRODUCTION: Nonautomatic focal atrial tachycardia (NAFAT) has been characterized in adults with structurally normal hearts. This article characterizes NAFAT in a population of patients with complex congenital heart disease. METHODS AND RESULTS: Electrophysiologic and electroanatomic mapping data and acute outcomes were reviewed in patients undergoing mapping and ablative procedures for atrial tachycardia at Children's Hospital, Boston, between January 1999 and December 2003. Twenty-two NAFAT foci were identified in 17 patients out of 216 patients studied. Fourteen of these 17 patients had congenital heart disease. The average age of the patients with a NAFAT mechanism was 27 years and there was no gender predilection. The presumptive diagnosis based on clinical grounds and surface ECG assessment in 11 of 17 patients with NAFAT was atrial flutter. None of the 17 patients were suspected of having a NAFAT mechanism by noninvasive assessment. Four of the 10 patients had both NAFAT and macroreentrant atrial tachycardias. NAFAT cycle lengths varied widely (200-680 ms) between patients. Sixteen of the 22 NAFAT foci were mapped to the anatomic right atrium (RA). Acute ablative success was achieved in 17 out of 22 foci (77%). CONCLUSION: NAFAT is relatively uncommon in a pediatric tertiary care setting, and in that setting occurs most often in adults with congenital heart disease. NAFAT is indistinguishable from other forms of atrial tachycardia by noninvasive means and can mimic other forms of atrial tachycardia on electrocardiogram. The foci were predominantly found in the RA and were, in most cases, acutely amenable to catheter ablation therapy.
Adolescent↗
Age, size, and lead factors alone do not predict venous obstruction in children and young adults with transvenous lead systems.
BACKGROUND: Venous occlusion is a recognized complication of transvenous pacing, and lead cross-sectional area indexed to body surface area (BSA) has been used to predict venous obstruction in children. OBJECTIVE: The aim of this study was to identify the risk factors and incidence of angiographic venous obstruction after transvenous lead implantation in both children and young adults. METHODS: Contrast venography was obtained in 85 of 90 consecutive patients undergoing repeat pacemaker or ICD procedures from 2002 to 2004 at a single cardiac center. Venograms were graded as complete venous obstruction, significant partial obstruction (>70% with collaterals), or patent. RESULTS: The cohort had a median age of 15.0 years at implant and was divided into two age groups: 3-12 years (n = 35) and 13 years and over (n = 50). After a median interval of 6.5 years, complete obstruction was seen in 11 of 85 patients (13%) and partial obstruction in another 10 patients (12%). No significant differences were seen in the incidence of obstruction between the two age groups although younger patients had a larger lead indexed to BSA ratio (6.82 vs 5.05, P = 0.005). There were no significant differences between obstructed and nonobstructed patients in relation to age, size, growth, or lead factors. CONCLUSION: Transvenous lead systems implanted in young children have a similar incidence of venous occlusion compared to older patients. Furthermore, patient age, body size, and lead characteristics at implant do not clearly predict venous occlusion.
Adolescent↗
Cardiac conduction through engineered tissue.
In children, interruption of cardiac atrioventricular (AV) electrical conduction can result from congenital defects, surgical interventions, and maternal autoimmune diseases during pregnancy. Complete AV conduction block is typically treated by implanting an electronic pacemaker device, although long-term pacing therapy in pediatric patients has significant complications. As a first step toward developing a substitute treatment, we implanted engineered tissue constructs in rat hearts to create an alternative AV conduction pathway. We found that skeletal muscle-derived cells in the constructs exhibited sustained electrical coupling through persistent expression and function of gap junction proteins. Using fluorescence in situ hybridization and polymerase chain reaction analyses, myogenic cells in the constructs were shown to survive in the AV groove of implanted hearts for the duration of the animal's natural life. Perfusion of hearts with fluorescently labeled lec-tin demonstrated that implanted tissues became vascularized and immunostaining verified the presence of proteins important in electromechanical integration of myogenic cells with surrounding re-cipient rat cardiomyocytes. Finally, using optical mapping and electrophysiological analyses, we provide evidence of permanent AV conduction through the implant in one-third of recipient animals. Our experiments provide a proof-of-principle that engineered tissue constructs can function as an electrical conduit and, ultimately, may offer a substitute treatment to conventional pacing therapy.
Animals↗
Intravenous amiodarone for incessant tachyarrhythmias in children: a randomized, double-blind, antiarrhythmic drug trial.
BACKGROUND: Intravenous (IV) amiodarone has proven efficacy in adults. However, its use in children is based on limited retrospective data. METHODS AND RESULTS: A double-blind, randomized, multicenter, dose-response study of the safety and efficacy of IV amiodarone was conducted in 61 children (30 days to 14.9 years; median, 1.6 years). Children with incessant tachyarrhythmias (supraventricular arrhythmias [n=26], junctional ectopic tachycardia [JET, n=31], or ventricular arrhythmias [n=4]) were randomized to 1 of 3 dosing regimens (low, medium, or high: load plus 47-hour maintenance) with up to 5 open-label rescue doses. The primary efficacy end point was time to success. Of 229 patients screened, 61 were enrolled during 13 months by 27 of 48 centers in 7 countries. Median time to success was significantly related to dose (28.2, 2.6, and 2.1 hours for the low-, medium-, and high-dose groups, respectively; P=0.028). There was no significant association with dose for any arrhythmia subgroup, including JET, but the subgroups were too small for an accurate assessment. Adverse events (AEs) were common (87%), leading to withdrawal of 10 patients. There were 5 deaths in the 30-day follow-up period (2 possibly related to the study drug). Dose-related AEs included hypotension (36%), vomiting (20%), bradycardia (20%), atrioventricular block (15%) and nausea (10%). CONCLUSIONS: In children, the overall efficacy of IV amiodarone, as measured by time to success, was dose related but not significantly for any arrhythmia subgroup. AEs were common and appeared to be dose related. Although efficacious for critically ill patients, the dose-related risks of IV amiodarone should be taken into account when treating children with incessant arrhythmias. Prospective, placebo-controlled trials would be helpful in assessing antiarrhythmic drug efficacy in children, because their results may differ from retrospective series and adult studies.
Adolescent↗
Three-dimensional echo-guided beating heart surgery without cardiopulmonary bypass: atrial septal defect closure in a swine model.
OBJECTIVE: In this study, we tested 3 techniques of atrial septal defect closure under real-time 3-dimensional echocardiography guidance in a swine model. METHODS: The operations were conducted under the sole guidance of a modified real-time 3-dimensional echocardiography guidance system with a x4 matrix transducer (Sonos 7500, Philips Medical Systems, Andover, Mass). Eighteen swine were anesthetized, and after median sternotomy, the echo probe was applied directly to the surface of the right atrium. To create an atrial septal defect, balloon atrial septostomy and atrial septal defect enlargement were performed. Subsequently, 3 different techniques of atrial septal defect closure were attempted: group I, direct suture closure; group II, closure of the atrial septal defect using the Amplatzer device (AGA Medical Corp, Golden Valley, Minn); and group III, patch closure of the atrial septal defect (n = 6 each). RESULTS: Real-time 3-dimensional echocardiography guidance provided sufficient spatial resolution and a satisfactory frame rate to provide a "virtual surgeon's view" of the relevant anatomy during the entire procedure. All atrial septal defects were enlarged, and the mean final size was 8.5 +/- 1.8 mm. Atrial septal defect closure was successfully accomplished with all the 3 surgical techniques examined. In groups I and III, the needles (1-3 sutures) and staples (6-12 staples) penetrated the tissue and patch material consistently, whereas in group III, the Amplatzer atrial septal defect device was easily deployed. There was no incident device/staple embolization or air introduction. Neither intraoperative 2-dimensional color Doppler echocardiography nor postmortem macro-evaluation revealed any residual shunts. CONCLUSIONS: Beating heart atrial septal defect closure under real-time 3-dimensional echocardiographic guidance is feasible and, unlike catheter-based devices, applicable for any type of secundum atrial septal defect.
Animals↗
Comparison of modern steroid-eluting epicardial and thin transvenous pacemaker leads in pediatric and congenital heart disease patients.
OBJECTIVE: Optimal pacemaker lead choice in pediatric patients eligible for either epicardial or transvenous leads remains unclear. We compared performances of modern thin transvenous (TTV) and steroid-eluting epicardial (SEE) leads in patients followed at one pediatric center. METHODS: Retrospective review of patients with qualifying leads implanted from August 1997 to March 2004. Threshold energy (TE) at implant and follow-up, sensing thresholds, lead complications, and repeat pacing-related procedures were analyzed. Lead performances were compared using t-tests, Wilcoxon rank-sum tests and Cox regression. Survival curves were plotted using Kaplan-Meier analysis. RESULTS: A total of 370 implant procedures, 521 leads, and 1549 visits were evaluated. In all, 256 leads were SEE (49%, 184 implants) and 265 were TTV (51%, 186 implants). Median follow-up was 29 months (range 1-80 months). Patients with SEE systems were younger at implant (6 vs. 17 yrs, p < 0.001), and more had congenital heart defects (82% vs. 57%, p < 0.001). At follow-up, ventricular TEs were higher for SEE leads at implant (p < 0.001), 1 month (p < 0.001), and up to 4 years (p = 0.019). When compared across all follow-up durations combined, TTV TEs were significantly lower than SEE TEs for both atrial and ventricular leads (p < 0.001). A total of 70 repeat procedures were performed in 60 patients during the study period, which comprised 18% of SEE and 14% of TTV system patients (p = NS). In all, 18 TTV and 19 SEE leads failed (p = NS). Estimated freedom from lead failure at 1, 3, and 5 years was 97%, 88%, 85% for TTV leads and 96%, 92%, and 58% for SEE leads (log rank P = NS). CONCLUSIONS: Both SEE and TTV leads showed good mid-term performance and survival in our cohort. Higher TEs seen for SEE leads, especially ventricular and unipolar leads, may result in higher current drain and thus more generator replacements than TTV systems. Lead failure rates were comparable across lead types. TTV leads offer a promising alternative to SEE systems in terms of performance for young patients without intracardiac shunting who do not require open-chest surgery for another indication.
Adolescent↗
Inability to cannulate the coronary sinus in patients with supraventricular arrhythmias: congenital and acquired coronary sinus atresia.
We report 4 cases of congenital and acquired coronary sinus ostial atresia incidentally found during electrophysiologic assessment for supraventricular arrhythmias. Congenital variants consisted of coronary sinus drainage predominantly via persistent left superior vena cavae and partial coronary sinus unroofing into the left atrium. The acquired variant was inadvertently produced during surgery for cor triatriatum. A variety of electrophysiologic substrates including right and left-sided accessory pathways and both typical and atypical AV nodal reciprocating tachycardia were identified. Approaches to imaging and accessing the coronary sinus when the os cannot be cannulated are discussed, including a search for right atrial accessory venous collaterals, venography to rule-out a persistent left superior vena cava, and coronary angiography.
Adolescent↗
Prospective trial of electroanatomically guided, irrigated catheter ablation of atrial tachycardia in patients with congenital heart disease.
BACKGROUND: Ablation success rates reported for atrial tachycardia (AT) patients with congenital heart disease (CHD) is lower than the rates reported for other varieties of supraventricular tachycardia. Retrospective studies suggest these rates might be increased by the use of irrigated radiofrequency (RF) ablation. OBJECTIVES: The purpose of this study was to determine whether irrigated RF ablation increases ablation success rates in patients with CHD and AT. METHODS: Patients were studied in a prospective, randomized, nonblinded manner. The operator was limited to use of randomized therapy (standard or irrigated ablation) for the first 6 minutes of RF application to each targeted arrhythmia. Lesion characteristics were recorded, and acute ablation success was ascertained. Structured clinical follow-up was performed over a 6-month period. RESULTS: Forty-seven ATs were targeted in 26 patients; 72% of these ATs were ablated. Within the 6-minute randomization period, no difference in success rates of standard and irrigated catheters was noted. However, crossover from standard to irrigated ablation more likely was successful than vice versa (irrigated: 8 successes/8 attempts vs standard: 1 success/4 attempts, P = .018), and overall success was greater using irrigated catheters (66% vs 33%, P = .019). Mean delivered power was slightly higher in irrigated lesions (32.5 W vs 30.2 W, P = .025), and mean temperature was much lower (33.5 degrees C vs 59.3 degrees C, P < .001). A composite AT intensity score was significantly reduced compared with preablation values at 6-month follow-up of all patients. CONCLUSIONS: Ablation of ATs in patients with CHD results in symptomatic improvement over short-term follow-up. Irrigated ablation may result in higher acute success rates in these patients.
Adolescent↗
Identification of cardiac rhythm features by mathematical analysis of vector fields.
Automated techniques for locating cardiac arrhythmia features are limited, and cardiologists generally rely on isochronal maps to infer patterns in the cardiac activation sequence during an ablation procedure. Velocity vector mapping has been proposed as an alternative method to study cardiac activation in both clinical and research environments. In addition to the visual cues that vector maps can provide, vector fields can be analyzed using mathematical operators such as the divergence and curl. In the current study, conduction features were extracted from velocity vector fields computed from cardiac mapping data. The divergence was used to locate ectopic foci and wavefront collisions, and the curl to identify central obstacles in reentrant circuits. Both operators were applied to simulated rhythms created from a two-dimensional cellular automaton model, to measured data from an in situ experimental canine model, and to complex three-dimensional human cardiac mapping data sets. Analysis of simulated vector fields indicated that the divergence is useful in identifying ectopic foci, with a relatively small number of vectors and with errors of up to 30 degrees in the angle measurements. The curl was useful for identifying central obstacles in reentrant circuits, and the number of velocity vectors needed increased as the rhythm became more complex. The divergence was able to accurately identify canine in situ pacing sites, areas of breakthrough activation, and wavefront collisions. In data from human arrhythmias, the divergence reliably estimated origins of electrical activity and wavefront collisions, but the curl was less reliable at locating central obstacles in reentrant circuits, possibly due to the retrospective nature of data collection. The results indicate that the curl and divergence operators applied to velocity vector maps have the potential to add valuable information in cardiac mapping and can be used to supplement human pattern recognition.
Algorithms↗
From selective parasympathetic modulation of AV node to rate control therapy.
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Atrial Fibrillation↗
Relation of right ventricular pacing in tetralogy of Fallot to electrical resynchronization.
Prolonged QRS duration is a marker of increased sudden death risk in tetralogy of Fallot. Right ventricular pacing increased QRS duration in this population and could be counteracted with optimization of the atrioventricular interval in a subset of patients, potentially offering right ventricular resynchronization in patients with baseline right bundle branch block. Effective pacing therapy may require site-specific placement of pacing leads and precise pacemaker programming.
Adult↗
Patient, procedural, and hardware factors associated with pacemaker lead failures in pediatrics and congenital heart disease.
OBJECTIVES: To examine outcomes of children with pacemakers over a 22-year period and identify risk factors for lead failure. BACKGROUND: Small patient size, structural cardiac abnormalities, and growth may complicate pediatric pacemaker management. Better knowledge of risk factors for lead failure in these patients may help improve future outcomes. METHODS: All pacemaker patients followed at one pediatric center 1980-2002 were included. Lead failures were identified retrospectively as leads repaired, replaced, or abandoned due to fracture, insulation break, dislodgement, or abnormalities in pacing or sensing. Risk factors were identified using logistic regression and Cox analyses. RESULTS: A total of 1007 leads were implanted in 497 patients during the study period (5175 lead-years). Median age at implant was 9 years (0-55); 64% of patients had structural congenital heart disease. Median follow-up time was 6.2 years (0-22). Lead failure occurred in 155 leads (15%), and 115 patients (23%), with 28% of patients experiencing multiple failures. Significant independent correlates of lead failure included age <12 years at implant, history of structural congenital heart defects, and epicardial lead placement. Younger patients (<12 years) experienced significantly more lead fractures than older children (P = .005), while patients with congenital heart defects experienced more exit block. Epicardial leads were more likely to fail due to fracture or exit block, while transvenous leads failed more due to insulation breaks or dislodgements. CONCLUSIONS: Pediatric pacing patients have a high incidence lead failures. These occur most commonly in younger patients, structural congenital heart disease, and those with epicardial lead systems. Approaches to pacing system implantation and follow-up in these patients need to be individualized, with special attention to minimizing risk of lead failures. Our findings suggest that expanded utilization of transvenous systems in smaller patients seems justified when anatomy permits.
Adolescent↗
Outcomes of radiofrequency catheter ablation of atrioventricular reciprocating tachycardia in patients with congenital heart disease.
OBJECTIVES: Assessment of clinical outcomes of catheter ablation of atrioventricular reciprocating tachycardias in patients with congenital heart disease (CHD). BACKGROUND: Atrioventricular reciprocating tachycardias occur in patients with CHD and may be poorly tolerated. METHODS: Retrospective review of all 105 such ablations in 83 patients performed between 03/90 and 02/02 at one institution. RESULTS: The dominant arrhythmia mechanism was accessory pathway (70 patients, 84%), and the most common indications were drug-refractory tachycardia, life-threatening arrhythmia, and elective presurgical ablation. Congenital heart disease diagnoses were diverse, with one third of patients having Ebstein's anomaly. Twenty patients (24%) had catheter access limited by prior surgeries or occluded vascular access. Of 109 accessory pathways (APs), 74 (68%) were manifestly preexcited, and 71 (65%) were located on the right atrioventricular groove. Fourteen patients (20%) had multiple pathways. There were 2 major complications (1 death, 1 hemorrhage), and 3 minor complications (5.5% of procedures). Acute success rate was 80% per procedure, 82% for left- and 70% for right-sided APs. Acute success rates for patients with Ebstein's anomaly were similar to patients with other CHD diagnoses, but Ebstein's patients were more likely to have recurrence. At 44 +/- 35 months follow-up, successful ablation was achieved in 59% of procedures and 68% of patients, with 19 patients (23%) undergoing one or more repeat ablations. CONCLUSIONS: Compared to patients with normal cardiac anatomy, patients with CHD of all varieties have lower rates of acute and long-term success for ablation for atrioventricular reciprocating tachycardias.
Adolescent↗
Radiofrequency catheter ablation of ventricular tachycardia in children and young adults with congenital heart disease.
OBJECTIVES: The aim of this study was to expand data on outcomes for radiofrequency catheter ablation (RFCA) of ventricular tachycardia (VT) in young patients and to identify obstacles to success. BACKGROUND: Ablation of VT is performed infrequently in young patients. Published experience has been limited to case reports and small descriptive series. METHODS: A retrospective review of 97 consecutive VT ablation procedures involving 62 patients at a single institution from 1990 to 2003 was undertaken. All intention-to-treat procedures were analyzed. RESULTS: Mean age was 13.9 +/- 9.4 years. Procedures were categorized according to VT mechanism as follows: idiopathic right ventricle (n = 37); idiopathic left ventricle (n = 24); congenital heart disease (n = 20); or other structural disease (n = 16). Acute success was achieved in 58 (60%) of 97 procedures. Of the 39 failures, 33 were aborted cases due to inability to induce sufficient ectopy for mapping in 12, high-risk location near the His bundle or coronary artery in 11, unstable VT in 7, and anatomic obstacles in 3. Recurrence rate after acutely successful RFCA was 34% (20/58 procedures) at a mean follow-up of 3.8 +/- 2.0 years. Ultimately, long-term success was achieved in 38 (61%) of 62 patients after a mean of 1.6 +/- 0.9 procedures, with the highest success rate (87%) for idiopathic left ventricular tachycardia. CONCLUSIONS: When analyzed on a strict intention-to-treat basis, a long-term success rate of 61% is observed with ablation of VT in young patients. Inability to induce stable VT for precision mapping and certain high-risk VT locations can be significant obstacles to success.
Adolescent↗
Three-dimensional echocardiography-guided atrial septectomy: an experimental study.
OBJECTIVES: The surgical feasibility of beating-heart atrial septectomy under the guidance of two different types of real-time 3-dimensional echocardiography systems was examined. METHODS: A modified real-time 3-dimensional echocardiography system with a x4 matrix transducer (Sonos 7500; Philips Medical Systems, Andover, Mass) or a mechanical 1-dimensional array transducer (SSD-5500; Aloka Co, Ltd, Tokyo, Japan) was used. Small porcine atrial septal defects (n = 8) were enlarged with a Kerrison bone punch in the tank model. In the animal studies, small atrial septal defects (n = 8) were enlarged with the same device through a transatrial port. In both experiments, the area of the atrial septal defect measured by real-time 3-dimensional echocardiography was compared with the area measured directly. RESULTS: Real-time 3-dimensional echocardiography provided satisfactory images and sufficient anatomic detail for the atrial septectomy in both experimental settings. All the atrial septal defects were successfully enlarged; an increase of as much as 293% of the preoperative atrial septal defect area was achieved in the tank experiment, and an increase of as great as 449% of the preoperative area was achieved in the animal experiment. The size of the atrial shunt was increased significantly after the atrial septectomy relative to that before the surgery (P <.0001). The percentage enlargement of the atrial septal defect measured by real-time 3-dimensional echocardiography was strongly correlated with that measured directly (both r(2) = 0.997, P <.0001) Bland-Altman analysis showed close agreement between the results obtained by the two measurement methods in both models. CONCLUSIONS: Real-time 3-dimensional echocardiography provides satisfactory images and sufficient anatomic detail for atrial septectomy. This experiment demonstrates the surgical feasibility of a beating-heart intracardiac procedure such as atrial septectomy under real-time 3-dimensional echocardiographic guidance.
Animals↗