Voltage and propagation mapping: New tools to improve successful ablation of atrioventricular nodal reentry tachycardia.

INTRODUCTION: Mapping system is useful in ablation of atrioventricular nodal reentry tachycardia (AVNRT) and localization of anatomic variances. Voltage mapping identifies a low voltage area in the Koch triangle called low-voltage-bridge (LVB); propagation mapping identifies the collision point (CP) of atrial wavefront convergence. We conducted a prospective study to evaluate the relationship between LVB and CP with successful site of ablation and identify standard value for LVB. MATERIALS AND METHODS: Three-dimensional (3D) maps of the right atria were constructed from intracardiac recordings using the ablation catheter. Cut-off values on voltage map were adjusted until LVB was observed. On propagation map, atrial wavefronts during sinus rhythm collide in the site representing CP, indicating the area of slow pathway conduction. Ablation site was selected targeting LVB and CP site, confirmed by anatomic position on fluoroscopy and atrioventricular ratio. RESULTS: Twenty-seven consecutive patients were included. LVB and CP were present in all patients. Postprocedural evaluation identified standard cut-off of 0.3-1 mV useful for LVB identification. An overlap between LVB and CP was observed in 23 (85%) patients. Procedure success was achieved in all patient with effective site at first application in 22 (81%) patients. There was a significant correlation between LVB, CP, and the site of effective ablation (p = .001). CONCLUSION: We found correlation between LVB and CP with the site of effective ablation, identifying a voltage range useful for standardized LVB identification. These techniques could be useful to identify ablation site and minimize radiation exposure.

Analysis of electrical and mechanical left atrial properties in patients with persistent atrial fibrillation.

The study of left atrial (LA) mechanical function during atrial fibrillation (AFib) can provide valuable information, particularly if such profiling is related to the cavity electrical substrate and conveys prognostic information. To assess if there is any relation between LA mechanical and electrical asynchrony and if such evaluation can be of interest in stratifying AFib patients. 50 patients with persistent AFib who underwent electrical cardioversion (CV) were evaluated with pre-CV atrial electrograms (AEGs). Electrical asynchrony was classified according to Wells' patterns of AEGs, ranging from most organized (I) to most dispersed (III) one. LA mechanical asynchrony was addressed by transthoracic 2D-speckle-tracking echo and quantified according to time-to-peak standard deviation (TP-SD) of wall strains and their peak values (PS) before CV, after 24 h, at 1 month. Pre-CV a linear, inverse relation between TP-SD and PS (p < 0.001) and a direct linear relation between TP-SD and Wells' classes (p = 0.04) were observed. With sinus rhythm TP-SD decreased (p = 0.023) and PS increased (p < 0.001), suggesting improved LA mechanical milieu. A multivariate analysis, testing the effects of baseline variables in predicting post-CV recurrence of AFib, revealed that amount of TP-SD variation pre/24 h post-CV was the only independent predictor at 6 months (p = 0.046). Speckle tracking-derived LA parameters can describe LA wall forces during AFib, categorizing the asynchronous mechanistic profile of AFib that correlates with the degree of the dispersed LA electrical activity. The amount of changes in LA mechanical asynchrony pre/post-CV seems to have prognostic relevance in predicting SR maintenance.

Inappropriate implantable cardioverter-defibrillator discharges unrelated to supraventricular tachyarrhythmias.

AIMS: The development of implantable cardioverter-defibrillators (ICDs) with QRS morphology discrimination and dual-chamber sensing capabilities has improved the differentiation of supraventricular from ventricular tachycardias (VTs). Inappropriate ICD discharges may result from extracardiac signals caused by electromagnetic interference (EMI), because of electric fields and leakage currents from domestic or medical electrical devices, damaged sensing leads, and various cardiac and extracardiac signals that mimic VT and/or ventricular fibrillation. The aim of our study was to determine retrospectively the incidence and clinical relevance of these ICD behaviours and offer possible therapeutic solutions. METHODS AND RESULTS: We have observed inappropriate discharges unrelated to supraventricular arrhythmias in 13 (3.9%) of the 336 patients implanted with ICDs in our centre from 1989 to 2005. Seven patients received inappropriate shocks following exposure to external EMI: improperly grounded electric stove, electrically powered watering system, hydro-massage bath, electrical pruner, electrocautery current during cardiac surgery, transcutaneous electric nerve stimulation. In four patients, spurious discharges were related to internal noise of the ICD system from inappropriate lead connections. In two cases, erroneous antitachycardia therapy was delivered following different body signals oversensing (T-wave oversensing, wide QRS double-counting and myopotentials). In nine patients, non-invasive solutions prevented further inappropriate therapies (avoidance of EMI, malfunctioning atrial lead exclusion, ventricular sensing reprogramming). In four patients, surgical revision of the system was required (lead connections or position revision). CONCLUSION: In our experience, inappropriate ICD discharges unrelated to supraventricular arrhythmias occurred in about 4% of ICD patients. A careful evaluation of clinical data and telemetric information (lead impedance, sensed R-wave, stored electrograms) is essential in order to understand the nature of inappropriate ICD discharges and to select the most appropriate solution.

Closed loop stimulation in prevention of vasovagal syncope. Inotropy Controlled Pacing in Vasovagal Syncope (INVASY): a multicentre randomized, single blind, controlled study.

OBJECTIVES: To determine whether dual-chamber rate-adaptive Closed Loop Stimulation (CLS) could prevent recurrence of Vasovagal Syncope (VVS). BACKGROUND: During VVS, an increase in myocardial contractility associated with a reduction of ventricular filling produces an increase in baroreceptor afferent flow and a consequent decrease in the heart rate. The CLS algorithm is a form of rate-adaptive pacing, which responds to myocardial contraction dynamics, by measuring variations in right ventricular intracardiac impedance: during an incipient VVS it could increase paced heart rate and avoid bradycardia, arterial hypotension and syncope. METHODS: Fifty patients (27 males, mean age 59+/-18 year) with severe and recurrent vasovagal syncope and positive Head Up Tilt Test (HUTT) with cardioinhibition, received a CLS pacemaker (INOS2, Biotronik GmbH Co., Germany). The primary end point was recurrence of two VVSs during a minimum of 1 year of follow-up. Randomization between DDD-CLS and DDI mode (40 bpm) pacing was performed only during the first stage of the study (first year): 9/26 randomized to DDI mode (control group) and 17/26 in DDD-CLS mode. All the 24 patients recruited in the second stage of the study (second year) were programmed in DDD-CLS mode. RESULTS: Of the nine patients randomized to the DDI mode, seven had recurrences of syncope during the first year. At the end of the first year the nine patients were reprogrammed to the CLS mode and no syncope occurred after reprogramming. The 41 patients programmed to CLS had a mean follow-up of 19+/-4 months: none reported VVS, only four (10%) reported occasional presyncope and their quality of life greatly improved. Positive HUTT at the end of the first year failed to predict the clinical response to CLS pacing. CONCLUSIONS: The study demonstrates the effectiveness of CLS pacing in preventing cardioinhibitory VVS. A possible placebo effect of pacemaker implantation occurred in 22% of patients.