Pacing and clinical electrophysiology : PACE
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Pacing Clin Electrophysiol · Jan 1997
The value of DDD pacing in patients with an implantable cardioverter defibrillator.
Although the beneficial effects of DDD pacing are well known, currently available ICDs provide only fixed rate ventricular antibradycardia pacing. In a consecutive series of 139 patients with ICDs, we have analyzed the need for antibradycardia pacing and the indications for DDD pacing. We also report our initial experience with the Defender 9001 (ELA Medical, France) DDD-ICD. ⋯ Up to 18% of our ICD patients are in need of antibradycardia pacing. Of these pacemaker dependent patients, 80% have an indication for DDD pacing. Our first clinical experience with a DDD-ICD confirms the hemodynamic benefit of AV synchronous pacing in ICD patients with pacemaker syndrome.
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The goal of this study was to determine whether delivering transvenous defibrillation shocks, coordinated with the up/down-slope VF waveform patterns in the shocking lead, would improve the probability of successful defibrillation. Anesthetized swine (32-38 kg, n = 8) were implanted with an RV-->SVC + SQArray transvenous system to measure VF waveform patterns and to deliver shocks. The shocks were generated by a Cardiac Pacemakers Inc. biphasic waveform generator. ⋯ P = NS). However, during high amplitude fibrillation, shocks delivered on the up-slope were significantly more successful than those delivered on the down-slope (Chi-square: 67% vs 39%; P < 0.001). These results suggest that delivering defibrillation shocks during the up-slope of the high amplitude signal in the shocking lead may improve the probability of successful defibrillation of ICDs.
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Twiddler's syndrome may result from pulse generator manipulation or from spontaneous rotation due to movement around an inadequately secured electrode. In this case, the electrode became coiled in the right ventricular outflow tract.
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Pacing Clin Electrophysiol · Nov 1996
Case ReportsVerapamil sensitive incessant ventricular tachycardia in the newborn.
Incessant VTs in infancy are often poorly tolerated. Response to conventional antiarrhythmic therapy is disappointing. The present case involves a 3-week-old infant with an incessant VT of a left bundle branch block, and normal axis morphology. ⋯ Tachycardia persisted despite treatment with adenosine, esmolol, procainamide, and flecainide. Intravenous verapamil suppressed tachycardia and prevented inducibility, and no further recurrences were seen on oral verapamil. This case suggests that some incessant VTs in infancy may be due to calcium channel related afterdepolarizations or triggered activation.
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Pacing Clin Electrophysiol · Nov 1996
Comparative StudyUse of automatic mode change between DDD and AAI to facilitate native atrioventricular conduction in patients with sick sinus syndrome or transient atrioventricular block.
The benefits of the automatic DDD (DDD/AMC) mode in the Chorus II pacemaker (Chorus 6234; Ela Medical Inc.), which automatically switches the modes between DDD and AAI to respect spontaneous AV conduction as much as possible in AAI while preserving safety pacing in DDD during paroxysmal AV block (AVB) only, remain unproven. This study examined the functions of the DDD/AMC mode in 12 patients with sick sinus syndrome (SSS; n = 10) or paroxysmal complete AVB (n = 2). A short-term (24 hours) comparative study between simple DDD mode and the DDD/AMC mode was performed in 8 of the 12 patients, and a medium-term (55.2 +/- 54.6 days) follow-up of the DDD/AMC mode was completed in all 12 patients. ⋯ From the medium-term study, the total AV delay (AV delay plus AV hysteresis) exceeded 300 ms in 6 of the 12 patients in DDD/AMC, and usually became longest during nighttime. From the short- or medium-term study in the 12 patients, two patients preferred the DDD/AMC mode while one preferred the DDD mode. These results suggest that the DDD/AMC mode is useful, at least in SSS patients without > or = 1 degree AVB, by reducing the percentage ventricular pacing.