Bridge to success: A better method of cryoablation for atrioventricular nodal reentrant tachycardia in children.

BACKGROUND: Cryoablation for atrioventricular nodal reentrant tachycardia (AVNRT) is associated with higher recurrence rates than radiofrequency ablation (RFA). Junctional tachycardia marks procedural success with RFA, but no such indicator exists for cryoablation. OBJECTIVE: The purpose of this study as to determine the impact of voltage mapping plus longer ablation lesions on midterm success of cryoablation for children with AVNRT. METHODS: We performed a single-center retrospective analysis of pediatric patients with AVNRT who underwent cryoablation from 2011 to 2015. Patients ablated using a standard electroanatomic approach (control) were compared with patients ablated using voltage mapping (voltage group). In the voltage group, EnSite NavX navigation and visualization technology (St Jude Medical, St Paul, MN) was used to develop a "bridge" of lower voltage gradients (0.3-0.8 mV) of the posteroseptal right atrium to guide cryoablation. Kaplan-Meier analysis was used to determine freedom from recurrence of supraventricular tachycardia. RESULTS: In all, 122 patients were included (71 voltage, 51 control). There was no difference between groups regarding age, sex, or catheter-tip size. Short-term success was similar in both groups (98.5% voltage vs 92% control; P = .159), but recurrence rates were lower in the voltage group (0% vs 11%, P = .006). Follow-up time was shorter in the voltage group (15 ± 7 months vs 22 ± 17 months, P < .05). The 1-year freedom from recurrence was lower in the voltage group (100% vs 91.5%, P <.05). Ablation times were longer in the voltage group (43.7 ± 20.9 minutes vs 34.3 ± 20.5 minutes, P = .01), but overall procedure times were shorter in the voltage group (157 ± 40 minutes vs 198 ± 133 minutes; P = .018). No significant complication was seen in either group. CONCLUSION: Voltage gradient mapping and longer lesion time can decrease recurrence rates in pediatric patients with AVNRT.

Endomyocardial fibrosis and mural thrombus in a 4-year-old girl due to idiopathic hypereosinophilia syndrome described with serial cardiac magnetic resonance imaging.

We present the case of a 4-year-old girl with idiopathic hypereosinophilia syndrome, endomyocardial fibrosis, and mural thrombus. This condition is rarely seen in children outside the tropics. Myocardial biopsy is historically the standard for diagnosis. Reports in adult literature, however, have shown the utility of cardiac MRI as a non-invasive tool for diagnosis, prognosis, and monitoring. To our knowledge, this is the first reported case with serial cardiac MRI in a child.

Efficacy of implantable cardioverter defibrillators in young patients with catecholaminergic polymorphic ventricular tachycardia: success depends on substrate.

BACKGROUND: The effectiveness of implantable cardioverter-defibrillator (ICD) therapy for the management of catecholaminergic polymorphic ventricular tachycardia (VT) in young patients is not known. ICD discharges are not always effective and inappropriate discharges are common, both resulting in morbidity and mortality. METHODS AND RESULTS: This is a multicenter, retrospective review of young patients with catecholaminergic polymorphic VT and ICDs from 5 centers. ICD discharges were evaluated to determine arrhythmia mechanism, appropriateness, efficacy of therapy, and complications. A total of 24 patients were included. Median (interquartile range) ages at onset of catecholaminergic polymorphic VT symptoms and ICD implant were 10.6 (5.0-13.8) years and 13.7 (10.7-16.3) years, respectively. Fourteen patients received 140 shocks. Ten patients (42%) experienced 75 appropriate shocks and 11 patients (46%) received 65 inappropriate shocks. On actuarial analysis, freedom from appropriate shock at 1 year after ICD implant was 75%. Of appropriate shocks, only 43 (57%) demonstrated successful primary termination. All successful appropriate ICD discharges were for ventricular fibrillation. No episodes of polymorphic VT or bidirectional VT demonstrated successful primary termination. The adjusted mean (95% confidence interval) cycle length of successful discharges was significantly shorter than unsuccessful discharges (168 [152-184] ms versus 245 [229-262] ms; adjusted P=0.002). Electrical storm occurred in 29% (4/14) and induction of more malignant ventricular arrhythmias in 36% (5/14). There were no deaths. CONCLUSIONS: ICD efficacy in catecholaminergic polymorphic VT depends on arrhythmia mechanism. Episodes of ventricular fibrillation were uniformly successfully treated, whereas polymorphic and bidirectional VT did not demonstrate successful primary termination. Inappropriate shocks, electrical storm, and ICD complications were common.

Catecholaminergic polymorphic ventricular tachycardia found in an adolescent after a methylenedioxymethamphetamine and marijuana-induced cardiac arrest.

OBJECTIVE: To illustrate the challenges of managing patients with acute, undiagnosed arrhythmias through a case that demonstrates a possible association between catecholaminergic polymorphic ventricular tachycardia, a genetically determined severe arrhythmia disorder that often presents as either syncope or sudden death, and 3,4-Methylenedioxymethamphetamine ("Ecstasy") combined with marijuana, which are often considered safe drugs by users. DESIGN: Case report. SETTING: Pediatric intensive care unit. PATIENT: A 15-yr-old male collapsed suddenly after ingesting an unknown substance and smoking marijuana. He was successfully resuscitated by first-responder chest compressions and rescue breaths along with a single 100-J shock by paramedics. He was intubated and transferred to a pediatric intensive care unit. Initial cardiac workup was negative but severe instability on vasopressors and a family history of intermittent palpitations and syncope in his brother raised suspicion for catecholaminergic polymorphic ventricular tachycardia. Identification of the unknown substance required coordination with a toxicology laboratory. INTERVENTIONS: The patient had extremely labile cardiovascular responses to vasopressors. On day 5, his blood pressure was stable and he was extubated. A full cardiac workup, including a catheterization (preadmission to pediatric intensive care unit), electrocardiogram, cardiac magnetic resonance imaging were done to screen out most structural arrythmogenic diseases. A specific genetic test for catecholaminergic polymorphic ventricular tachycardia was sent. MEASUREMENTS AND MAIN RESULTS: The patient's methylenedioxymethamphetamine blood level was 87 ng/mL approximately 12 hrs after ingestion. Given the 3-8 hr half-life of methylenedioxymethamphetamine, it is likely that levels were toxic at the time of ingestion (>110 ng/mL). Marijuana may have provided a synergistic critical catecholamine release to trigger an arrhythmia. Genetic testing showed a ryanodine receptor-2 mutation that was consistent with catecholaminergic polymorphic ventricular tachycardia. CONCLUSIONS: While an initial cardiac workup for an acute, undiagnosed arrhythmia may be negative, family history may be a simple, essential component of patient management and disease diagnosis. This case demonstrates a possible association between methylenedioxymethamphetamine, marijuana, and catecholaminergic polymorphic ventricular tachycardia. All genetic and structural arrythmogenic disorders should be considered when working up a patient with presumed toxin-induced arrhythmias.

Cryoablation with an 8-mm tip catheter for pediatric atrioventricular nodal reentrant tachycardia is safe and efficacious with a low incidence of recurrence.

BACKGROUND: Cryoablation with 4- and 6-mm tip ablation catheters has been demonstrated to be safe and effective in the treatment of atrioventricular nodal reentrant tachycardia (AVNRT) in pediatric patients, albeit with a higher rate of clinical recurrence. Limited information is available regarding efficacy, mid-term outcomes, and complications related to the use of the 8-mm Freezor Max Cryoablation catheter (Medtronic, Minneapolis, MN, USA) in pediatric patients. METHODS: We performed a retrospective review of all pediatric patients with normal cardiac anatomy who underwent an ablation procedure for treatment of AVNRT using the 8-mm tip Cryoablation catheter at three large pediatric academic arrhythmia centers. RESULTS: Cryoablation with an 8-mm tip catheter was performed in 77 patients for treatment of AVNRT (female n = 40 [52%], age 14.8 +/- 2.2 years, weight 62.0 +/- 13.9 kg). Initial procedural success was achieved in 69 patients (69/76, 91%). Transient second- or third-degree atrioventricular (AV) block was noted in five patients (6.5%). There was no permanent AV block. Of the patients successfully ablated with Cryotherapy, there were two recurrences (2/70, 2.8%) over a follow-up of 11.6 +/- 3.3 months. CONCLUSION: Cryoablation with an 8-mm tip ablation catheter is both safe and effective with a low risk of recurrence for the treatment of AVNRT in pediatric patients.

Cryoablation for atrioventricular nodal reentrant tachycardia in young patients: predictors of recurrence.

BACKGROUND: Recurrence rates of atrioventricular nodal reentry tachycardia (AVNRT) after cryoablation continue to remain high despite excellent initial success rates. Our objective was to evaluate the clinical outcomes of cryoablation for AVNRT with the 4-mm and 6-mm tip cryoablation catheters in a young population and to elicit predictors of arrhythmia recurrence. METHODS: We retrospectively reviewed all patients who underwent cryoablation for AVNRT at the UCSF/Stanford Pediatric Arrhythmia Center from January 2004 to February 2007. RESULTS: One hundred fifty-four patients (age 13.7 years (3.2-24.4)) underwent cryoablation for AVNRT of which 144 patients had inducible AVNRT (123 sustained and 21 nonsustained) and 10 had presumed AVNRT. Initial success was achieved in 95% (146/154), with no difference between the 4-mm (93%) and 6-mm (98%) cryoablation catheter tips (P = 0.15). There was no permanent atrioventricular (AV) block. Transient third-degree AV block occurred in nine patients (6%), with no difference between the 4-mm (4%) and 6-mm (9%) tip (P = 0.13). AVNRT recurrence was documented in 14% in a median time of 2.5 months (0.25-20). Recurrences were lower with the 6-mm (9%) versus the 4-mm (18%) tip, but this did not reach statistical significance (P = 0.16). With univariate analysis, a longer fluoroscopy time was the only significant factor associated with recurrence. Multivariate analysis failed to identify any significant predictor of AVNRT recurrence. CONCLUSION: Outcomes of cryoablation for AVNRT continue to be good without the complication of AV block. We could not identify any specific parameter associated with AVNRT recurrence. Further improvements in cryoablation technique will be necessary to reduce recurrences.

Cryoablation versus radiofrequency ablation for treatment of pediatric atrioventricular nodal reentrant tachycardia: initial experience with 4-mm cryocatheter.

BACKGROUND: Initial reports have shown cryoablation to be safe and efficacious for treatment of atrioventricular nodal reentrant tachycardia (AVNRT). No direct comparisons of cryoablation vs radiofrequency (RF) catheter ablation in pediatric patients have been made. OBJECTIVES: The purpose of this study was to compare the outcomes of cryothermal vs RF catheter ablation for treatment of AVNRT in pediatric patients. METHODS: We retrospectively reviewed consecutive ablation procedures for treatment of AVNRT at a single arrhythmia center. The RF group consisted of patients who underwent RF ablation from 2002 until cryothermy became available. The cryoablation group consisted of patients who underwent cryothermal ablation from 2004 to 2005. The groups were compared for procedural and electrophysiologic outcomes. RESULTS: RF (n = 60, age 14 +/- 4 years) and cryoablation (n = 57, age 14 +/- 4 years) groups had similar demographic and baseline parameters. Procedural times were shorter in the RF group (RF ablation 112 +/- 31 minutes vs cryoablation 148 +/- 46 minutes, P < .001). Fluoroscopy times were comparable (RF ablation 21 +/- 15 minutes vs cryoablation 20 +/- 13 minutes, P = .77). In an intention-to-treat analysis, success of the procedure was 100% for RF ablation and 95% for cryoablation (P = .11). No permanent AV block occurred in either group. Recurrence rates were higher for the cryoablation group, but this did not reach statistical significance (RF ablation 2% vs cryoablation 8%, P = .19). CONCLUSION: Cryoablation appears to be similar to RF for ablation of AVNRT with respect to short-term efficacy and safety of the procedure in a pediatric population. Recurrence rates are higher with cryoablation.

Utility of Holter electrocardiogram in iron-overloaded hemoglobinopathies.

Cardiac arrhythmias are among the leading causes of morbidity and mortality of transfusion-dependent, iron-overloaded beta-thalassemia patients. Routine screening with Holter electrocardiogram has been recommended; however, infrequent electrocardiographic changes limit its clinical usefulness. The purpose of this study was to determine the diagnostic yield of Holter electrocardiogram monitoring and its correlation with patient symptoms and disease status. A retrospective analysis was performed on 27 transfusion-dependent thalassemia patients who underwent cardiac questionnaire and Holter screening yearly, in addition to echocardiogram and quantitative iron-level determination. Four patients had clinically significant arrhythmias detected on Holter screening, while 2 patients developed severe cardiac complications secondary to arrhythmias within 1 year of follow-up of normal Holter screening. Early detection of cardiac events among transfusion-dependent thalassemia patients with Holter electrocardiography is not clinically effective. Other screening modalities, including the transtelephonic event recorder, should be evaluated in arrhythmia surveillance.