based studies A rapid increase in the rate and speed (sprint test) of VT may be more effective at uncovering catecholamine-provoked arrhythmias Additional Testing Echocardiography With regard to arrhythmias, particularly ventricular arrhythmias, many decisions concerning management and risk are based on whether there is a structurally and functionally normal heart; thus echocardiographic assessment is imperative The Ebstein malformation or congenitally corrected transposition of the great arteries in which there can be an Ebstein-like malformation of the systemic AV valve and hypertrophic cardiomyopathy occur in association with WPW syndrome.157 Incessant arrhythmias such as AET, JET, and PJRT can result in ventricular dysfunction; therefore initial and ongoing echocardiographic assessment is indicated in children presenting with these arrhythmias In adults with a high burden of ventricular ectopy, arrhythmia-induced cardiomyopathy is described and cases of this have been reported in children Finally, in children with congenital heart disease, the appearance of arrhythmias may suggest a worsening of the hemodynamic status, and echocardiographic assessment is warranted ▪ Cardiac MRI: Certain conditions are best assessed by MRI, including ARVC and myocarditis, and there is increasing evidence of the importance of MRI in assessing for fibrosis in hypertrophic cardiomyopathy ▪ Laboratory evaluations: Blood chemistry testing is important when QT prolongation is identified, especially if there is no family history of LQTS, since low levels of potassium and magnesium can result in QT prolongation Atrial tachycardias including AF can be seen in the setting of hyperthyroidism Finally, serum drug testing should be performed in patients where the clinical scenario, arrhythmias, and ECG seem consistent with an intentional or accidental overdose, illicit drug use, or changes in renal/hepatic function that could affect the clearance of prescription medications Most antiarrhythmic agents have the potential to be proarrhythmic; thus, in a patient taking these agents, a new arrhythmia or conduction change should prompt the testing of blood levels when possible Electrophysiologic Study Although initially conceived as a diagnostic tool, the EPS is now performed mostly in the setting of a catheter ablation procedure Many of the diagnostic portions of the study are still undertaken in this setting Transesophageal Electrophysiologic Study This is a less invasive tool and may be helpful in situations where diagnostic information is needed but the child is too small for an invasive catheter procedure or in situations where there is not enough information to merit the study A specially designed bipolar catheter is placed in the nares with the electrode tip in the region of the left atrium Electrograms are sought where there are atrial and ventricular recordings but only atrial pacing can be performed with this technology Atrial pacing is undertaken to initiate tachycardia; assess atrial, AV nodal, or accessory pathway characteristics; or to terminate tachycardia The relationship of atrial and ventricular electrograms allows for a determination of association or dissociation between the two chambers Studies have confirmed diagnostic accuracy, similar to that of an invasive EPS.158 This is a less invasive way to provide risk assessment in children with asymptomatic WPW syndrome.159 Invasive Electrophysiologic Study Procedure Anesthesia Most pediatric EPSs are undertaken in association with a catheter ablation; in this setting, general anesthesia is often used, but there is a trend toward avoiding inhalational anesthetics Propofol is most commonly used Anesthesia minimizes discomfort, decreases memory of the procedure, and decreases movement during the procedure for greater safety.160 However, if ablation is not anticipated and the procedure is likely to be short, conscious sedation may be adequate, depending on the patient and the laboratory experience Adult procedures are often done with sedation rather than anesthesia, and the original risk stratification studies in WPW syndrome were performed without anesthesia.50 There are concerns about the effects of anesthesia on myocardial tissue conduction and refractoriness Studies have shown that neither propofol nor isoflurane anesthesia altered sinuatrial or AV node function in pediatric patients undergoing RF catheter ablation161 and that intravenous anesthesia had no effect on arrhythmia induction or slow-pathway ablation in patients with documented AV nodal reentrant tachycardia (AVNRT).162 Furthermore, propofol has not shown a clinically significant effect on accessory pathway characteristics.163 Catheters There are a variety of multipole catheters that allow pacing and sensing and can be placed in any chamber, although the standard approach is placement in the high right atrium, right ventricular apex, and through the anterosuperior part of the tricuspid valve to record electrical activity from the His bundle (Fig 22.25) These sites are usually accessed from a femoral venous approach When catheter ablation is planned, a multipole catheter is placed in the coronary sinus to record atrial and ventricular electrograms from the left AV groove, usually accessed from subclavian or jugular venous approach Catheters are not placed in the left ventricle or left atrium unless indicated by the tachycardia substrate The RV apical catheter can be repositioned in the RVOT for ventricular stimulation studies ... way to provide risk assessment in children with asymptomatic WPW syndrome.159 Invasive Electrophysiologic Study Procedure Anesthesia Most pediatric EPSs are undertaken in association with a catheter ablation; in this setting, general anesthesia is often used, but there is a trend toward avoiding... Studies have shown that neither propofol nor isoflurane anesthesia altered sinuatrial or AV node function in pediatric patients undergoing RF catheter ablation161 and that intravenous anesthesia had no effect