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  • 1
    Electronic Resource
    Electronic Resource
    Transvenous Single Lead Atrial Defibrillation: Efficacy and Risk of Ventricular Fibrillation in an Ischemic Canine Model (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 21 (1998), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Transvenous atrial defibrillation with multiple atrial lead systems has been shown to be effective in models without the potential for ventricular arrhythmias. The specific aim of this study was to evaluate the efficacy and safety of transvenous single lead atrial defibrillation in a canine model of ischemia cardiomyopathy. Ten dogs had ischemia cardiomyopathy induced by repeated intracoronary micmsphere injections. The mean LV ejection fraction decreased from 71%± 9% to 38%± 14% (P = 0.003). Spontaneous atrial fibrillation (AF) developed in four dogs, and in six AF was induced electrically. Atrial defibrillation thresholds (ADFTs) were determined with synchronous low energy shocks using a transvenous tripolar lead with two defibrillation coils (right ventricle, superior vena cava) and an integrated sensing lead (RV coil vs electrode tip). The ADFTs derived by logistic regression were compared at 50% and 90% probability of success (ED50, ED90): ED50 was 2.4 ±1.7 J and 2.9 ±2.1 J, respectively, for 5- and 10-ms monophasic shocks, and 1.8 ± 0.9 J and 2.1 ± 1.3 J, respectively, for 5- and 10-ms biphasic shocks. Immediately after 3 of 2,179 (0.1%) synchronized shocks, ventricular fibrillation (VF) developed. VF was induced in 3 of 1,062 (0.3%) shocks with integrated sensing (RV coil vs electrode tip) compared to 0 of 1,117 shocks when a separate bipolar RV sensing electrode was used for synchronization. In our canine model of ischemic cardiomyopathy, low energy atrial defibrillation via a transvenous single lead system was highly effective. However, there was a small but definite risk of VF induction, which seemed to be greater when an integrated as opposed to a true bipolar RV sensing was used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1998.tb00102.x
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  • 2
    Electronic Resource
    Electronic Resource
    Mechanisms Underlying Different Surface ECG Morphologies of Recurrent Monomorphic Ventricular Tachycardia and Their Modification by Procainamide (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 8 (1997), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: ECG Pleomorphism of Ventricular Tachycardia. Introduction: Distinct surface ECG morphologies (ECGMs), from one episode to the next, of recurrent monomorphic ventricular tachycardia (VT) in the same patient complicate endocardial catheter mapping and the success of ablative therapy. This study investigates the incidence and mechanisms of multiple ECGMs during recurrent monomorphic VTs in a canine model of experimental myocardial infarction (MI). Methods and Results: Computerized ECG analysis and simultaneous endocardial and epicardial activation mapping with a 64 bipolar electrode array were used to analyze the relation between site of VT origin, local activation sequence, and surface ECGM in 72 VT episodes induced in 9 of 17 dogs with experimental MI. Pairwise comparisons of all VTs induced in the same animal were done in drug-free state (47 VTs) and after intravenous procainamide (25 VTs). In drug-free state, VT pairs with similar surface ECGMs manifested endocardial hreak-through sites (BSs) within a distance 〈 10 mm in 46 (100%) of 46 VT pairs compared to 43 (45%) of 95 VT pairs with different surface ECGMs (P 〈 0.0001). Of all 89 VT pairs with endocardial BSs within 〈 10 mm, similar endocardial activation patterns were found in 34 (74%) of 46 pairs with similar ECGMs in contrast to 6 (14%) of 43 pairs with different ECGMs (P 〈 0.001). Similar comparisons of VT pairs induced after intravenous procainamide administration showed that the endocardial BSs were located within 〈 10 mm in 9 (75%) of 12 VT pairs with similar and in 17 (49%) of 95 with different surface ECGMs, respectively (P = NS). Conclusions: In the same heart, similar surface ECGMs of recurrent VT are highly predictive of closely spaced endocardial BSs in drug-free state, hut not after procainamide administration. Nearly half of the VTs with different surface ECGMs still originate from closely spaced endocardial BSs but commonly manifest a change in the endocardial activation spread from this site. Thus, assumptions about different mechanisms and sites of VT origin based on dilTerent surface ECGMs should be made with caution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1997.tb00604.x
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    Paper (German National Licenses)
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