MARENCO, J.P., et al.: Use of the AutoCapture Pacing System with Implantable Defibrillator Leads.
Introduction: Previous studies using various bipolar pacemaker leads have shown that the AutoCapture (AC) Pacing System is able to verify ventricular capture and regulate pacing output, increasing patient safety with respect to unexpected threshold changes and potentially prolonging device longevity. An increasing number of patients with implantable cardioverter defibrillators (ICDs) require ventricular pacing that contributes to a shortening of longevity of these systems. This prospective study tested the compatibility of the AC system with bipolar ICD leads. Methods: The AC algorithm was evaluated prior to ICD testing in 30 ICD recipients. A single coil, active fixation, true bipolar ventricular lead was implanted in 21 patients, and a dual coil, passive fixation, integrated bipolar ventricular lead was implanted in 9 patients. A ventricular evoked response sensitivity test and an AC threshold test were performed using a pacemaker with the ventricular AC algorithm. Results: AC was recommended in 22/30 (73.3%) of implants, including 20/21 (95.2%) with the single coil and 2/9 (22.2%) with the dual coil lead. Mean polarization was lower (
1.23 ± 0.95 mV
vs
3.70 ± 2.33 mV, P = 0.013
) while the mean evoked response was higher (
18.04 ± 8.29 mV
vs
10.13 ± 4.22 mV, P = 0.002
) with the single coil leads. Conclusion: Automatic threshold tracking using the AC is compatible with ICD leads. Leads with lower polarization and greater evoked response are more likely to result in recommendation of AC use. Use of this system offers the potential for increasing ICD generator longevity and improving patient safety in response to late unexpected threshold increases. (PACE 2003; 26[Pt. II]:471–473)
Recording cardiac electrical activity after a countershock has been limited by amplifier saturation. Modifications to our computer-assisted mapping system allowed us to record electrical activity from 56 epicardial electrodes within 5 ms of the end of a countershock. Modifications included the use of solid-state switches to disconnect the filter section of the amplifiers during the shock and changing the low-frequency response of the amplifiers from 0.1 to 10 Hz to filter out large, low-frequency potentials after the shock. Six-millisecond truncated exponential shocks were delivered between the superior vena cava and right ventricular apex through a quadripolar catheter during normal rhythm in seven dogs. As shocks of increasing voltage were delivered during the T-Q interval, progressively more of the epicardium was directly depolarized. A shock of 109 +/- 17 (SD) V directly depolarized the entire epicardium. Shocks of constant voltage were then delivered with increasing prematurity during diastole. As the ventricles became more refractory with increasing shock prematurity, the amount of epicardium depolarized became progressively less. Thus computer-assisted mapping techniques are capable of measuring the area depolarized by a shock during normal rhythm and may be useful during arrhythmias to improve our understanding of defibrillation and cardioversion.
This paper discusses shortcomings of conventional Holter monitoring in paced patients and describes a new technique which permits reliable detection of intermittent pacemaker malfunction and counts pacemaker activity during the recording period. Evaluation of the system of 64 consecutive patients revealed 15 with unsuspected episodic pacemaker dysfunction.
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