753Abstracts / Journal of Electrocardiology 44 (2011) 748–754

Lead aVR “net QRS area” as an index of all 6 limb leads: implicationsfor the diagnosis and follow-up of patients with edematous states,including heart failureJohn E. MadiasMount Sinai School of Medicine of the New York University/Divisionof Cardiology, Elmhurst Hospital Center, Elmhurst, NY

Contemporary electrocardiogram (ECG) machines measure only leads Iand II and calculate online the other 4 limb leads. Consequent to theabove, lead aVR could be used as an index of all 6 limb leads,considering its mathematical relationship with leads I and II [aVR = −(I +II)/2]. This was shown recently using top-to-bottom amplitudes (Amps) ofQRS complexes in a consecutive series of 100 ECGs (Pacing ClinElectrophysiol 2009;32:1567-76): aVR vs ∑I&II, r = 0.95, P = .00005;aVR vs ∑6limbleads, r = 0.81, P = .00005; and ∑I&II vs ∑6limbleads,r = 0.94, P = .00005. However the above-cited mathematical relationshipof leads I, II, and aVR pertain to all instantaneous and simultaneousmeasurements of these 3 leads, which is not accurately reflected by theirAmp. Thus, the bnet QRS areaQ appeared to be a more suitable metricexpressing the equation aVR = −(I + II)/2. Accordingly, a second analysisof the same 100 ECGs yielded the following: aVR vs ∑I&II, r = −0.995,P = .0005; aVR vs ∑6limbleads, r = −0.76, P = .0005; and ∑I&II vs∑6limbleads, r = 0.78, P = .0005. It is concluded that aVR net QRS areareflects leads I and II. However, aVR net QRS area underperforms aVRAmp (r = 0.76 vs r = 0.81) as an index of ∑6limbleads. Thiscounterintuitive finding needs to be reexplored in a much larger series ofECGs. Either way, aVR Amp and the aVR net QRS area are bothexcellent bpoint of careQ indices that could be used in the diagnosis andfollow-up of patients with edematous states, including heart failure.

doi:10.1016/j.jelectrocard.2011.09.037

Impact of successful catheter ablation therapy on electricalrepolarization in patients with repetitive monomorphic ventricularectopy and preserved left ventricular functionA. Schirdewan, A. Marek, A. Gapelyuk, R. Fischer, E. Safak, L. KochDepartment of Cardiology, Charite Campus Benjamin Franklin,Berlin, Germany

Purpose: Repetitive monomorphic ventricular ectopy (RMVE) caninduce electrical remodeling leading to cardiomyopathy that iscompletely reversible with successful catheter ablation. The aim of thisstudy was to examine the relationship between repetitive monomorphicventricular ectopy and repolarization abnormalities in patients withpreserved left ventricular function and the role of catheter ablation inreversing these changes.

Methods: We evaluated 35 consecutive patients (15 men; mean age, 45.5F13.5 years) with RMVE originating from the right or left ventricle. Allpatients underwent catheter ablation therapy. Repeated echocardiography,exercise testing, 24-hour long-term electrocardiogram (ECG), and cardiacmagnetic field mapping (CMFM) were performed before ablation procedureand during the long-term follow-up (FU). Repolarization based on CMFMwas analyzed using a multichannel LT-SQUID system in the state of sinusrhythm. We evaluated the CMFM pattern and quantified the inhomogeneityof the repolarization period using 4 parameters describing asymmetry offield maxima and multipolarity of the electromagnetic field.

Results: The mean LV-EF was 60.8k F 6.5k, and the mean burden ofRMVE before ablation was 26 461 F 12 308 ectopic beats/24 hours. Aftersuccessful ablation procedure (30/35 patients) and a mean FU of 35 F13 months, the burden of RMVE was depressed stable to 83 F 155 ectopicbeats/day. The CMFM revealed 4 types of changes in repolarization fieldpattern (RFP): (a) inhomogeneous RFP before ablation, with no changeduring FU (12/30 patients); (b) inhomogeneous RFP before ablation,complete normalization during FU (9/30 patients); (c) homogeneous fieldpattern before ablation and during FU (7/30 patients); and (d) homogeneousRFP and changing to inhomogeneous RFP during FU (2/30 patients).

Conclusion: Only 30k of the patients show normal repolarization pattern.Repolarization abnormalities are present in 70k of patients with RMVE and

preserved LV function. In 43k of them, a complete reversal ofrepolarization changes after successful catheter ablation was observed.

doi:10.1016/j.jelectrocard.2011.09.038

Improving safety of automatic defibrillation through rejection of noisyelectrocardiogram segments by ICG analysisIan Thompson, Cesar NavarroJohn Anderson Heartsine Technologies, Belfast, Northern Ireland

Objective: A major impediment to an accurate diagnosis of a patient'selectrocardiogram (ECG) by automatic defibrillators is the presence of noiseat the point of contact between electrodes and patient. In some cases, thisnoise can be severe enough to cause a shock to be inaccurately advised. It isproposed to detect when too much noise is present through a considerationof the impedance cardiogram (Z). A detection of an overly noisyenvironment will prevent a shock diagnosis from occurring and eliminatethe possibility of a shock being erroneously delivered to a patient.

Methodology and Main Results: The diagnostic algorithm uses the ICGsimultaneously obtained from the patient to classify the ECG as noisy or not.The algorithm operates by first obtaining the derivative (dZ/dt) of the ICG. IfdZ/dt rises above a certain threshold value, determined by the A-to-D value,then a flag is raised to indicate a noisy signal. The average of this flag (either0 or 1 at any particular sample) is taken from a moving time window over aperiod of 0.75 seconds (128 samples at a sample rate of 170.66/s). If thismoving average rises above 0.5, then the algorithm is prevented frommaking a shock diagnosis at the current sample and for the following4 seconds to ensure no shock is delivered during the noisy period.To test the effectiveness of the algorithm, patient electrodes are used torecord both ECG and ICG using a shock-disabled device. Subjects aremade to undergo certain exercises intended to create a noisy ECG thatis capable of provoking a shock diagnosis by the defibrillator. Theseinclude walking, running, simulation of a seizure, and simulation of anunstable environment (such as the back of an ambulance) with theelectrodes attached. Each exercise is performed for 2 minutes followedby a 30-second rest. The algorithm was successful in preventing a shockin all cases, with all the exercise periods being correctly identified astoo noisy for accurate diagnosis.

Conclusions: The impedance cardiogram provides an accurate and effectiveway of preventing erroneous shock diagnoses. This can be applied to reducethe possibility of automatic defibrillators incorrectly diagnosing shocks inboth noisy environments and from improper use of the device.

doi:10.1016/j.jelectrocard.2011.09.039

Local injury current on intracardiac electrogram after appropriateand inappropriate electrical therapies delivered by an implantablecardioverter-defibrillatorLarisa G. Tereshchenko, Ronald D. BergerThe Johns Hopkins University School of Medicine, Baltimore, MD

Background: We previously demonstrated that local injury current (LIC),observed on the near-field (NF) right ventricular (RV) electrograms (EGMs),can occur after an implantable cardioverter-defibrillator (ICD) shock duringdefibrillation threshold testing. Local injury current, but not ICD shock,predicted subsequent pump failure death or hospitalization due to heartfailure exacerbation. Acute LIC is a transient phenomenon, and whether LICappears after appropriate and inappropriate ICD therapies is unknown. In thiswork, we systematically describe NF RV EGM morphology observed afterappropriate and inappropriate ICD therapies, delivered due to spontaneousevents, occurring at least 1 month after ICD implantation.

Methods: Near-field RV EGM for 10 seconds after delivered ICD therapywas compared with baseline EGM in 420 events that occurred in 134 patients(mean age, 60.8F 14.8 years; 106 [79k] men). Themagnitude of elevated ordepressed potential immediately after the major fast EGM deflection wasdefined as LIC, and its ratio to the peak-to-peak EGM amplitude was definedas relative LIC. Local injury current of at least 1 mV or relative LIC of at least15k was considered significant.