Tim R. Betts

Electrophysiological Mapping and Ablation of Intra-Atrial Reentry Tachycardia After Fontan Surgery With the Use of a Noncontact Mapping System

BACKGROUNDnAtrial tachyarrhythmias are a complication of Fontan surgery. Conventional electrophysiological mapping and ablation techniques are limited by the complex anatomic and surgical substrate and a high arrhythmia recurrence rate. This study investigates the use of noncontact mapping to identify arrhythmia circuits and guide ablation in Fontan patients.nnnMETHODS AND RESULTSnEleven arrhythmias were recorded in 6 patients. Noncontact mapping improved recognition of the anatomic and surgical substrate and identified exit sites from zones of slow conduction in all clinical arrhythmias. Radiofrequency linear lesions were targeted across these critical zones in 5 patients. One patient underwent surgical cryotherapy. Although immediate success was achieved in 3 of 5 patients with radiofrequency ablation, 2 patients had a recurrence after a mean of 6.4 months of follow-up. The patient who underwent cryoablation remains free of arrhythmias.nnnCONCLUSIONSnNoncontact mapping can identify arrhythmia circuits in the Fontan atrium and guide placement of ablation lesions. Arrhythmia recurrence is high, possibly because of inadequate lesion creation rather than inaccurate mapping and lesion targeting.

Determination of Human Ventricular Repolarization by Noncontact Mapping Validation With Monophasic Action Potential Recordings

Background—Noncontact mapping (NCM) has not been validated as a clinical technique to measure ventricular repolarization. We used NCM to determine repolarization characteristics by analysis of reconstructed unipolar electrograms (UEs) at the same sites as monophasic action potential (MAP) recordings in the human ventricle. Methods and Results—MAPs were recorded from a total of 355 beats at 46 sites in the left or right ventricle of 9 patients undergoing ablation of ventricular tachycardia guided by NCM (EnSite system). Measurements were made during sinus rhythm, constant right ventricular pacing, and ventricular extrastimuli during restitution-curve construction. The EnGuide locator signal was used to document MAP catheter locations on the endocardial geometry. UE-determined activation-recovery interval (ARI) measured at the maximum derivative of the T wave (Wyatt method) and the minimum derivative of the positive T wave (alternative method) was correlated with MAP measured at 90% repolarization (MAP90%) at the same sites. ARI correlated with MAP90% during steady state by the Wyatt method (r=0.83, P<0.001) and the alternative method (r=0.94, P<0.001). Restitution curves constructed from MAP and UE data exhibited the same characteristics, with a mean correlation coefficient of 0.95 (range, 0.90 to 0.99, P<0.001). The error between ARI and MAP90% was greater over a shorter diastolic coupling interval but was not influenced by distance of the sampling site from the multielectrode array. Conclusions—NCM accurately determines steady-state and dynamic endocardial repolarization in humans. Global, high-density, NCM data could be used to characterize abnormalities of human ventricular repolarization.

High-density mapping of left atrial endocardial activation during sinus rhythm and coronary sinus pacing in patients with paroxysmal atrial fibrillation

Introduction: This study was designed to record global high‐density maps of left atrial endocardial activation during sinus rhythm and coronary sinus pacing.

Global Dynamic Coupling of Activation and Repolarization in the Human Ventricle

Background— The ability to determine spatial and dynamic changes in ventricular repolarization may help to understand arrhythmogenic mechanisms in humans. We hypothesized that noncontact mapping could be used to investigate global activation-repolarization coupling in the human ventricle during steady state and premature extrastimulation. Methods and Results— Activation-recovery intervals (ARIs) determined from reconstructed unipolar electrograms by the Ensite system were analyzed during sinus rhythm, constant pacing, spontaneous ventricular ectopic beats, and premature stimulation at intermediate and short coupling intervals in the left or right ventricle of 13 patients (6 female; mean age, 48 years) without structural myocardial disease. ARIs were measured from 32 sites in each ventricle with the use of a method validated with monophasic action potential recordings and unipolar contact electrograms. Global T-wave distribution was displayed on a 3-dimensional geometry of the ventricle, with polarities opposite to the direction of activation during steady state and premature stimulation. There was a significant inverse correlation between activation times and ARIs during sinus rhythm, ventricular ectopy, and premature stimulation (r=0.72, slope=−0.76, P<0.001). Premature stimuli at short coupling intervals flattened the regression slope compared with sinus rhythm (−0.61 versus −0.81; P=0.05), but the global pattern of repolarization was preserved. In comparison to our method, the Wyatt method of ARI measurement failed to demonstrate significant coupling between activation and repolarization (r=0.34, slope=0.19). Conclusions— Global, dynamic repolarization mapping of the human ventricle is feasible. An inverse coupling of activation and repolarization during steady state and premature stimulation may preserve electric stability in the normal ventricle.

Radiofrequency ablation of idiopathic left ventricular tachycardia at the site of earliest activation as determined by noncontact mapping.

Ablation of Idiopathic LV Tachycardia. Introduction. The most effective method for guiding radiofrequency (RF) ablation of idiopathic left ventricular tachycardia (ILVT) has yet to be determined. We investigated the use of noncontact mapping in five patients with this condition.

Inappropriate shock therapy in a heart failure defibrillator.

BETTS, T.R., et al.: Inappropriate Shock Therapy in a Heart Failure Defibrillator. A 63‐year‐old male with dilated cardiomyopathy underwent implantation of a “heart failure” defibrillator capable of biventricular pacing. He received an inappropriate shock 5 hours after the procedure. Stored electrograms revealed that during each sinus beat the ventricular channel recorded up to three separate events. These resulted from far‐field atrial sensing by the coronary venous lead, appropriate right ventricular sensing, then delayed left ventricular sensing (the result of left bundle branch block). As a consequence of far‐field left atrial sensing the two subsequent ventricular electrograms fell within the VF zone. Following an atrial premature beat, VF detection criteria were satisfied and shock therapy delivered. Although coronary venous lead repositioning eliminated far‐field atrial sensing, double counting of the widely split right and left ventricular electrograms still occurred during sinus rhythm. Shortening the programmed AV delay resulted in constant biventricular pacing with a single electrogram.

Endocardial Non-contact Mapping in Pediatric and Grown up Congenital Heart Arrhythmias

Pediatric patients undergoing electrophysiology procedures are a heterogeneous group, ranging from small children with structurally normal hearts and WPW syndrome, to young adults with congenital heart disease who have undergone extensive palliative surgery and have multiple complex arrhythmias. For over a decade radiofrequency ablation has been an effective therapy for “simpler” arrhythmias such as atrioventricular reentry tachycardias, which account for 60–82% of pediatric ablation procedures.1–3 Conventional mapping and ablation techniques abolish accessory pathways with long term success rates of 83–98%.2–7 Radiofrequency ablation of focal atrial tachycardias (a minority of patients) is less successful, with higher recurrence rates.1–3 Pediatric patients with idiopathic ventricular tachycardia have also been successfully ablated.8