Precise Measurement of Pediatric Defibrillation Thresholds

Completed

Conditions: Pediatrics
Defibrillators, Implantable

Interventions: Diagnostic Test: Defibrillator threshold testing
Other: Observation of post-shock intrinsic cardiac rhythm

Registration Number: NCT01043562

Lead Sponsor: Boston Children's Hospital

Brief Summary: Patients who receive an implantable cardioverter-defibrillator (ICD) usually undergo testing at the end of the ICD procedure to measure the amount of energy able to successfully defibrillate the heart (defibrillation threshold testing, or DFT). This study proposes to perform that measurement in pediatric patients already undergoing clinically necessary ICD procedures, with the measurement performed using a binary search method that has been previously validated in adult cohorts. We hypothesize that pediatric DFTs, when precisely measured, may be lower than previously assumed from extrapolation of adult data.

Detailed Description: Not available

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 20

Inclusion Criteria

Current follow-up at Children's Hospital Boston
Children with current or planned ICDs who are scheduled by their primary electrophysiologist for clinically necessary assessment/re-assessment of defibrillation threshold
If the patient has an ICD system with a non-transvenous shock coil: weight ≤35kg at time of initial implant, with current weight <50kg
If the patient has an ICD system with a conventional transvenous shock coil: current weight ≤60kg

Exclusion Criteria

Clinical failure of any system component not able to be addressed by hardware repair or exchange
Hemodynamic instability that in the judgment of the primary electrophysiologist warrants abbreviation of DFT assessment
Unsuccessful induction of fibrillation during DFT testing

Study & Design

Study Type: OBSERVATIONAL

Study Design: Not specified

Arm && Interventions

Group	Intervention	Description
Pediatric ICD pts	Defibrillator threshold testing	Inclusion criteria for study participants included: 1) weight ≤60 kg, 2) new or existing ICD system, and 3) clinically necessary assessment of the defibrillation efficacy of the ICD system. Transvenous systems utilized a high-voltage ICD coil with active-fixation lead attached to the right ventricular endocardial surface, whereas non-transvenous systems depended upon a high-voltage shocking coil placed within the pericardial, subcutaneous or pleural space. To be included in the post-shock pacing portion of the study, adequate sinus and AV node function had to be present at baseline. Exclusion criteria included 1) tenuous hemodynamic status felt to warrant abbreviation of the defibrillation efficacy testing or 2) inability to induce fibrillation during defibrillation threshold testing (DFT).
Pediatric ICD pts	Observation of post-shock intrinsic cardiac rhythm	Inclusion criteria for study participants included: 1) weight ≤60 kg, 2) new or existing ICD system, and 3) clinically necessary assessment of the defibrillation efficacy of the ICD system. Transvenous systems utilized a high-voltage ICD coil with active-fixation lead attached to the right ventricular endocardial surface, whereas non-transvenous systems depended upon a high-voltage shocking coil placed within the pericardial, subcutaneous or pleural space. To be included in the post-shock pacing portion of the study, adequate sinus and AV node function had to be present at baseline. Exclusion criteria included 1) tenuous hemodynamic status felt to warrant abbreviation of the defibrillation efficacy testing or 2) inability to induce fibrillation during defibrillation threshold testing (DFT).

Primary Outcome Measures

Name	Time	Method
Defibrillation Threshold	During clinical ICD procedure, as a single event	The defibrillation threshold is a measure of the minimum amount of energy (in Joules) that is able to successfully defibrillate an episode of ventricular fibrillation. This measurement is specific to each individual patient with his/her specific defibrillator configuration. There are several different strategies to measuring this in an individual patient; this study utilized the binary search protocol.

Secondary Outcome Measures

Name	Time	Method
Intrinsic Heart Rate in the Immediate Post-defibrillation Period	During clinical ICD procedure, as a single event	A patient will be considered to have an intrinsic slow heart rate in the period of time immediately following defibrillation (20 seconds) if any of the following are observed: \>7 paced beats, asystole \>4 seconds, or experienced \>10% decrease in systolic blood pressure.
Do DFTs Vary by Type of ICD Systems Implanted?	During clinical ICD procedure, as a single event	The defibrillation threshold (as measured in Joules as already described in the details regarding the primary outcome) will be compared between patients with two distinct general types of implanted defibrillator systems: 1) transvenous ICD systems (defibrillator leads located inside the vein and attached to the endocardial surface of the heart) and 2) non-transvenous ICD systems (including all other types of debrillation systems).