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Circulation. 1995;91:445-450

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(Circulation. 1995;91:445-450.)
© 1995 American Heart Association, Inc.

Articles

Improved Defibrillation Threshold With a New Epicardial Carbon Electrode Compared With a Standard Epicardial Titanium Patch

Presented in part at the 66th Annual American Heart Association Meeting, November 1993.

Eckhard U. Alt, MD; Parwis C. Fotuhi, MD; Richard L. Callihan, MD; Dennis L. Rollins, MSEE; Edgar Mestre, MD; Marty P. Combs, BSE; William M. Smith, PhD; Raymond E. Ideker, MD, PhD

From the Departments of Medicine (R.L.C., W.M.S., R.E.I.) and Pathology (D.L.R., R.E.I.), Duke University Medical Center, Durham, NC; the Engineering Research Center for Emerging Cardiovascular Technologies, the Department of Biomedical Engineering of the School of Engineering (W.M.S., R.E.I), Duke University, Durham, NC; and the I. Medical Clinic (E.U.A., E.M., M.P.C), Technische Universität Munich, Germany.

Correspondence to Raymond E. Ideker, MD, PhD, University of Alabama at Birmingham, Volker Hall Room G82A, Box 201, Birmingham, AL 35294.


*    Abstract
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 *Abstract
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down arrowResults
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Background Recent studies show that depending on the type of shock morphology used, 5% to 15% of patients requiring implantable defibrillators cannot be treated with a nonthoracotomy system. In these cases, an epicardial patch–based system becomes necessary. In this study, we investigated a newly developed epicardial carbon electrode as an alternative to a standard epicardial titanium patch.

Methods and Results A tubular epicardial braided carbon electrode of 7F diameter and 14-cm length applied in a U-shape to the epicardium was compared with a standard left ventricular epicardial 15-cm2 titanium mesh patch (CPI Inc). As cathode, a CPI endocardial lead, a Medtronic lead, or a carbon-platinum-iridium prototype electrode was used. Ventricular fibrillation was induced with a 60-Hz generator and allowed to continue for 10 seconds before a shock was given. Two different biphasic shock waveforms (3.2/2- and 6/6-millisecond) were delivered by the six electrode configurations. Eight dogs (weight, 24.5±1.3 kg) underwent an up-down defibrillation protocol. The order of testing the epicardial electrodes, the endocardial cathodes, and the waveform was randomized. With the epicardial carbon electrode, the mean defibrillation threshold (DFT) energy decreased 39% to 56% and the voltage decreased 24% to 35% compared with the titanium patch: from 8.3±2.5 to 4.9±3.6 J with the CPI lead and the 3.2/2-millisecond waveform, from 6.2±2.5 to 2.9±2.1 J with the carbon-platinum-iridium prototype, and from 6.4±3.4 J to 3.5±2.6 J with the Medtronic lead (P<=.05). The DFT determinations with the 6/6-millisecond biphasic waveform showed a similar trend with slightly higher values.

Conclusions Compared with a titanium patch, the new braided epicardial electrode significantly decreases the defibrillation energy requirements. This effect can be maximized by using an endocardial carbon-platinum-iridium prototype as cathode and a short duration biphasic waveform.


Key Words: electrodes • defibrillation • epicardial patches


*    Introduction
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 *Introduction
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down arrowResults
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Over the last two decades, implantable defibrillators have become a well-accepted and widely used therapy for patients at high risk of sudden cardiac death.1 2 3 4 5 The first generations of devices used high-energy shocks through epicardial patch systems.1 2 3 Despite their beneficial effect on prevention of sudden cardiac death, these defibrillators were not perfect devices. Several studies show an increase in transthoracic and transvenous defibrillation energy requirements due to epicardial patches,6 7 8 an increase in ventricular arrhythmias after patch placement,9 10 and the presence of operative and postoperative risk.11 Recent devices offer antitachycardia and antibradycardia pacing and low-energy cardioversion/defibrillation, mainly with transvenous and transvenous/subcutaneous lead configurations. Most patients can be treated with these new devices, but 5% to 15% of patients have high defibrillation thresholds (DFTs); regardless of the negative aspects with epicardial patches, an epicardial patch based–system is necessary in these cases.12 13 14 15 Also, patients who are at risk of ventricular arrhythmias and who undergo cardiac surgery often receive epicardial patches on a prophylactic basis without defibrillator implant. Therefore, the need for epicardial electrodes is real.

In this study, we tested a new epicardial prototype electrode made of braided carbon to compare its energy requirements for defibrillation with a standard epicardial titanium mesh patch in dogs.16 Additionally, we tested three different endocardial electrodes12 17 18 and two different waveforms19 to determine both the properties of this new material and the best endocardial/epicardial combination for defibrillation.


*    Methods
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 *Methods
down arrowResults
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Influence of Epicardial Patches on Defibrillation Threshold
This study was approved by the Institutional Animal Care and Use Committee at Duke University. It conformed to the guidelines of the American Heart Association on Research Animal Use adopted November 11, 1984.

Animal Preparation
In eight mongrel dogs, anesthesia was induced with intravenous pentobarbitol (30 to 35 mg/kg body wt) and maintained with a continuous infusion of pentobarbital at a rate of approximately 0.05 mg/kg per minute.20 21 Succinylcholine (1 mg/kg) was also given intravenously at the time of anesthesia induction. Supplemental doses of succinylcholine (0.25 to 0.5 mg/kg) were given as needed to maintain muscle relaxation. The animals were intubated with a cuffed endotracheal tube and ventilated with room air and oxygen through a Harvard respirator. A peripheral intravenous line was inserted, and normal saline was continuously infused. A femoral arterial line was placed for hemodynamic monitoring as well as for arterial blood gas analysis and electrolyte measurements. Normal metabolic status was maintained throughout the study by taking blood samples every 30 to 60 minutes and correcting any abnormal values. ECG leads were applied for continuous monitoring of lead II. The chest was opened through a median sternotomy, and the heart was suspended in a pericardial cradle. Body temperature was measured and maintained at 35° to 37°C with a thermal mattress and heat lamp. At the end of the study, euthanasia was induced with a potassium chloride injection. The heart was then removed and weighed.

Electrode Configurations
An epicardial titanium mesh patch CPI 040 (Cardiac Pacemakers Inc) with an active electrical surface area of 15 cm2 and a total area of 18 cm2 was compared with a braided tubular carbon electrode of 7F diameter and 14-cm length (Fig 1ADown). After randomization, one of these two epicardial electrodes was positioned on the anterolateral wall of the left ventricle. After the completion of testing of this electrode with all endocardial electrodes and waveforms, it was removed and the other epicardial electrode was positioned on the anterolateral wall of the left ventricle. The patch was securely sutured with six stitches while the U-shaped epicardial carbon wire was sutured with three stitches, describing the outer bounds of the patch (Fig 1BDown). Three different endocardial electrodes were used: (1) an 11F defibrillation electrode CPI Endotak (Cardiac Pacemakers Inc) with a 3.7-cm right ventricular coil, a 6.8-cm-long superior vena caval coil 9 cm proximal from the distal electrode (not used for shocking in this study), and a pacing electrode tip 5 mm distal from the right ventricular electrode; (2) a 10.5F Medtronic 6966 Transvene electrode with a 5-cm defibrillation electrode 25 mm proximal from the pacing tip; and (3) a 10F carbon-platinum-iridium prototype electrode with a 5-cm defibrillation electrode 15 mm proximal to the silicon tip.



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  		Figure 1. A, Drawings show electrode positions for the epicardial patch (1), the epicardial carbon wire (2), the right ventricular defibrillation catheter (3), and the pacing catheter (4). B, Photograph: The epicardial carbon electrode inscribes the outer bounds of the patch on the anterolateral wall of the left ventricle. It is sutured to the heart by three stitches. {/TITL;;;left;stack}

Only one endocardial electrode at a time was placed into the right ventricle for testing. The order in which each endocardial electrode was inserted and removed was determined by randomization. Each of the three leads was placed in the right ventricular apex through a right jugular incision under fluoroscopic guidance. Through a left jugular incision, a pacing catheter for induction of fibrillation and backup pacing was positioned in the right ventricle. The position of all endocardial leads was also verified manually.

Defibrillation Protocol and Data Acquisition
Defibrillation success was determined by a threshold value.22 23 Eight animals underwent defibrillation trials. The animal was randomized to have the epicardial patch or the carbon lead placed first. After placement of the epicardial electrode, the three endocardial electrodes were randomized and the first electrode was positioned in the right ventricle. The DFT was determined with one of the two biphasic waveforms. After determination of this threshold, the second waveform was tested. The first endocardial lead was removed, and this procedure was repeated with the second and then the third endocardial lead. After all six different DFT determinations with the first epicardial electrode were performed, it was removed. The second epicardial electrode was placed, and the three endocardial electrodes and the two waveforms were again tested in random order.

Defibrillation testing was performed by following a modified up-down protocol24 starting with a leading edge voltage of 400 V. The initial step size was 40 V. If the first shock failed, then incremental 40-V shocks were performed until a defibrillation success occurred. If the first shock succeeded, then decremental 40-V shocks were performed until the shock failed. After a reversal point was established, the step size was decreased to 20 V. The DFT was defined as the lowest voltage to defibrillate.

Ventricular fibrillation was induced by 60-Hz alternating current through the right ventricular apex pacing electrode, with the return electrode attached to the animal's chest wall. Fibrillation was allowed to continue for 10 seconds before attempting defibrillation. A failed shock was followed by a rescue shock of higher voltage delivered between the electrodes. If the rescue shock failed, it was followed by internal defibrillation with paddles given by a Life-Pak 8 defibrillator (Physio-Control Corp). A minimum of 4 minutes elapsed between each fibrillation-defibrillation attempt. Fibrillation was not reinitiated until blood pressure and heart rate had returned to normal. The defibrillation electrodes were connected to an external defibrillator (HVS-02, Ventritex Inc). The defibrillator delivered a dual-capacitor biphasic shock from a 150-µF capacitor bank. The truncated exponential biphasic shock utilized a second phase of opposite polarity to the first, with the second-phase leading edge voltage equal to the first-phase trailing edge voltage rounded to the nearest 10 V. For the first phase, the epicardial electrode was the anode and the endocardial electrode was the cathode. Two biphasic waveforms were tested, one with a first-phase duration of 3.2 milliseconds and a second-phase duration of 2 milliseconds, the other with durations of 6/6 milliseconds. There was a 1-millisecond delay between phases for both biphasic waveforms. The actual current and voltage waveforms delivered to the electrodes were obtained by isolating and recording the current across a 0.25-{Omega} resistor in series with the electrodes and a 1:4 resistor divider in parallel with the electrodes. These waveforms were digitized at 20 kHz and recorded by a Data Precision 6100 waveform analyzer. Signal analysis software within the analyzer was used to obtain impedance and energy measurements. The data were transferred to a Sun workstation and to a Macintosh computer for analysis.

Statistical Analysis
The data are expressed as the mean and standard deviation for energy, voltage, current, and impedance for all DFT determinations. Statistical analysis was performed with ANOVA and Friedman tests, and multiple comparisons between groups were based on rank sums.25 Significance was defined as P<=.05.


*    Results
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*Results
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The DFTs were analyzed to (1) compare the epicardial patch and the epicardial carbon wire electrode, (2) find the best right ventricular electrode/epicardial electrode configuration, and (3) compare the two biphasic waveforms with the different electrodes.

The TableDown compares the DFTs for two epicardial and the three endocardial electrodes for the two biphasic waveforms. Expressed are the mean and standard deviation for leading edge voltage, leading edge current, mean impedance of the first phase, and total energy of both phases at DFT. Statistical comparison was performed for the epicardial patch versus the epicardial carbon wire.


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  		Table 1. Results With 3.2/2-Millisecond Biphasic Waveform and With the 6/6-Millisecond Biphasic Waveform

Compared with the titanium patch, the epicardial carbon wire decreased the leading edge voltage requirements for defibrillation with the 3.2/2 (6/6)-millisecond biphasic waveform: 27% (24%) with the CPI lead, 35% (32%) with the carbon-platinum-iridium right ventricular-prototype, and 28% (30%) with the Medtronic lead (P<=.05 for 3.2/2 ms). Total energy also decreased 41% (39%) with the CPI lead, 53% (56%) with the carbon prototype, and 45% (45%) with the Medtronic lead (P<=.05 for 3.2/2 ms). Mean values for current decreased between 25% and 29% (15% and 29%) except for the Medtronic electrode. Impedance was 4% to 10% (6% to 14%) lower for the epicardial carbon configurations compared with the respective configurations with the epicardial patch. With the exception of the Medtronic electrode with the 6/6-millisecond waveform, voltage and energy at DFT decreased significantly compared with the epicardial patch irrespective of the right ventricular electrode or waveform when the epicardial carbon electrode was used for defibrillation (P<.05). The absolute values for the energy decreased with the shorter waveform, whereas the mean voltage was unchanged or increased slightly (Fig 2ADown and 2BDown).



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  		Figure 2. Bar graphs show epicardial carbon electrode (Carb) compared with the epicardial patch (Patch) for defibrillation leading edge voltage (V), total energy (J), current (A), and mean impedance ({Omega}) of the first phase at defibrillation threshold. Shown are the mean and standard deviation for the 3.2/2-millisecond waveform (A) and the 6/6-millisecond waveform (B) broken down individually for the three transvenous right ventricular electrodes (CPI Endotak, Carbon Prototype, and Medtronic 6966). *Significance is expressed as P<=.05.

The lowest DFT was achieved with a 3.2/2-millisecond pulse duration and the epicardial carbon wire combined with the endocardial carbon-platinum-iridium prototype (2.93±2.12 J). The highest DFT was found with the CPI right ventricular lead in combination with the titanium patch and the 6/6-millisecond waveform (8.71±3.20 J).

This beneficial effect of the epicardial carbon electrode and of the shorter impulse duration on total energy can be seen in Fig 3Down. In this figure, the DFT determinations for the three endocardial right ventricular electrodes were combined, and the mean value and standard deviation were calculated. This demonstrates the significant decrease (P<=.01) in energy when defibrillating by the epicardial carbon wire irrespective of the endocardial electrode used, especially when using the shorter pulse duration of 3.2/2 milliseconds.



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  		Figure 3. Bar graph shows total energy (J) at defibrillation threshold found with the epicardial carbon wire (Carbon) compared with the epicardial patch (Patch). Results shown are for the calculated mean and standard deviation of all three transvenous right ventricular electrodes together (CPI Endotak, Carbon Prototype, and Medtronic 6966) separated for the two waveforms of 3.2/2-millisecond and 6/6-millisecond duration. **Significance is expressed as P<=.01.

Independently comparing the individual data and the mean values for leading edge voltage, impedance, current, and total energy for the three different endocardial electrodes with the epicardial electrode or with the patch, we found that for the right ventricular carbon electrode there was a significantly lower voltage, current, and energy compared with the CPI electrode. The impedance was also significantly lower with the right ventricular carbon-platinum-iridium electrode compared with the CPI and Medtronic right ventricular electrode. The configuration of epicardial carbon electrode to right ventricular carbon-platinum-iridium prototype electrode resulted in six of eight dogs being defibrillated with energies below 2.4 J.


*    Discussion
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*Discussion
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Based on the positive experience with carbon materials in antibradycardia pacing,26 27 we examined carbon fibers and tested their possible use as defibrillation electrodes.28 The carbon electrodes used in this study were designed at the Technische Universität München.

In this study, we compared a newly developed tubular epicardial electrode made of braided carbon filaments to a standard epicardial patch. We also studied three different right ventricular electrodes and two different biphasic waveform durations. The reason for the study was to find a possible alternative to the epicardial patch that would defibrillate with low voltage and energy.

Our results for the endocardial/epicardial configurations gave DFTs that are comparable to those found in previous studies of our group. Dixon et al29 reported low DFTs for large contoured epicardial patches while Tang et al19 reported low energy requirements with large epicardial patches in conjunction with short biphasic waveforms. Guse et al30 demonstrated the possibility of low-energy defibrillation with four subcutaneous patches and endocardial leads. In this study, we also achieved low DFTs (2.93 J), but the endocardial/epicardial electrode configuration tested used a much smaller epicardial electrode.

A possible limitation of our study was the use of an open chest model. However, Kallok et al31 showed no difference in the DFT for a closed chest compared with an open chest determination using epicardial patches.

Both epicardial electrodes were positioned over the same region of the anterolateral wall of the left ventricle. The patch was sutured with several stitches to ensure good tissue contact. The carbon wire was sutured with three stitches in a U-shaped position describing the outer bounds of the patch. The geometrical area described by the two anodes was thus the same, but due to the outer insulation of the patch, the area within the U-shaped area with the carbon wire was slightly larger than the area covered by the titanium mesh of the patch. The direct electrode-tissue interface area for the patch is 15 cm2, compared with 3 cm2 calculated for the tubular carbon electrode (14-cm length, 7F diameter).

When the study was designed, our primary focus was to investigate an epicardial electrode that should be more easily applied on the epicardium, and we hoped to achieve similar or only slightly higher DFTs compared with standard patch placement. To our surprise, the voltage, energy, and current for defibrillation at DFT significantly decreased with the carbon electrode, yet impedance remained almost the same. A possible explanation for the lower defibrillation requirements despite primarily constant impedance values is a larger minimum potential gradient32 33 34 35 created by the carbon wire. Another possible explanation is a better electrode-tissue interface, as is seen with the carbon tips of bradycardia pacing electrodes,27 causing less polarization at the interface with more impedance contributed by the tissue because of the slightly different location of the carbon wire.

We used three different endocardial defibrillation catheters and two waveforms, as described in our previous study.18 We aimed to repeat our previous comparison of the three endocardial leads and to find the best of the six endocardial/epicardial electrode and waveform combinations for defibrillation. As in the previous study, the configurations with the carbon-platinum-iridium prototype electrode demonstrated the lowest DFTs.18 By combining the epicardial carbon wire and the endocardial carbon-platinum-iridium prototype and by using a short waveform, the defibrillation energy was significantly decreased by more than 50% compared with the least beneficial combination of electrodes and waveform duration.

The reason for the statistically significant lower impedance for the epicardial carbon compared with the patch when used in combination with the right ventricular carbon electrode remains unclear. A possible explanation is the high electrical surface of the carbon due to the microstructure of the multiple carbon fiber filaments, which may allow delivery of more current and voltage in a shorter time.18 28

The basic mechanism for the lower defibrillation energy requirements with a tubular electrode describing only the outer bounds of a patch is currently not fully understood. Some part of the mechanism may be attributed to carbon. A great deal of the lower DFT with this new concept may be attributed to the U-shape and location of the electrode. The extent of the effect attributable to the material and the extent to the shape and location needs to be evaluated in further studies.

In our experience, no other electrode material used has such high flexibility and pliability—therefore allowing good contact with the beating heart—as the carbon-based electrode. Our results were obtained by placing the carbon electrode onto the heart via thoracotomy. Depending on further trials, in the future this may allow a small epicardial carbon electrode to be placed by a minimally invasive procedure.35 36 We conclude that the carbon electrode placed on the epicardium to describe the outer bounds of the region normally encompassed by a patch electrode is a promising possible alternative for the standard patch electrode and deserves further investigation.

Conclusions
Within the limitations of our model, these results demonstrate a significant decrease in voltage, energy, and current requirements for defibrillation with an epicardial carbon wire electrode compared with a standard epicardial patch. The defibrillation energy can be additionally lowered by using an endocardial carbon-platinum-iridium electrode and a short biphasic waveform. Carbon may be a possible alternative material for defibrillation electrodes. The flexibility and pliability of the epicardial carbon wire may be beneficial in several respects. The mechanisms of replacing the patch with a single electrode describing its outer bounds need further evaluation, as do possible future means of noninvasive placement of the epicardial carbon electrode.


*    Acknowledgments
 
This study was supported in part by National Institutes of Health research grants HL-42760, HL-44066, and NC-93-SA-05 and The National Science Foundation Engineering Research Center Grant CDR-8622201. The authors wish to thank Ellen Dixon-Tulloch, Jenny Hagler, Sharon Melnik, and Robert Walker for their technical assistance and Kurt Ulm, MD, for his statistical consulting.

Received April 14, 1994;
*    References
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up arrowDiscussion
*References
 

  1. Mirowski M, Reid PR, Mower MM, Watkins L, Gott VL, Schauble JF, Langer A, Heilmann MS, Kolenik SA, Fischell RE, et al. Termination of malignant ventricular arrhythmias with an implanted automatic defibrillator in human beings. N Engl J Med. 1980;303:322-324. [Medline] [Order article via Infotrieve]
  2. Echt DS, Armstrong K, Schmidt P, Oyer PE, Stinson EB, Winkle RA. Clinical experience, complications, and survival in 70 patients with the automatic implantable cardioverterdefibrillator. Circulation. 1985;71:289-296. [Abstract/Free Full Text]
  3. Marchlinski FE, Flores BT, Buxton AE, Hargrove WC III, Addonizio VP, Stephenson LW, Harken AH, Doherty JU, Grogan EW Jr, Josephson ME. The automatic implantable cardioverter-defibrillator: efficacy, complications, and device failures. Ann Intern Med. 1986;104:481-488.
  4. Kelly PA, Cannom DS, Garan H, Mirabal GS, Harthorne JW, Hurvitz RJ, Vlahakes GJ, Jacobs ML, Ilvento JP, Buckley MJ, et al. The automatic implantable cardioverter defibrillator: efficacy complications and survival in patients with malignant ventricular arrhythmias. J Am Coll Cardiol. 1988;11:1278-1286. [Abstract]
  5. Powell AC, Fuchs T, Finkelstein DM, Garan H, Cannom DS, McGovern BA, Kelly E, Vlahakes GJ, Torchiana DF, Ruskin JN. Influence of implantable cardioverter-defibrillators on long-term prognosis of survivors of out-of-hospital cardiac arrest. Circulation. 1993;88:1083-1092. [Abstract/Free Full Text]
  6. Lerman BB, Deale OC. Effect of epicardial patch electrodes on transthoracic defibrillation. Circulation. 1990;81:1409-1414. [Abstract/Free Full Text]
  7. Walls JT, Schuder JC, Curtis JJ, Stephenson HE, McDaniel WC, Flaker GC. Adverse effects of permanent cardiac internal defibrillator patches on external defibrillation. Am J Cardiol. 1989;64:1144-1147. [Medline] [Order article via Infotrieve]
  8. Callihan RL, Dahl RW, Idriss SF, Wolf PD, Smith WM, Ideker RE. Defibrillation threshold measurements using an endocardial lead configuration with and without inactive epicardial patch in dogs. Circulation. 1993;88(suppl I):I-592. Abstract.
  9. Kim SG, Fisher JD, Furman S, Gross J, Zilo P, Roth JA, Ferrick KJ, Brodman R. Exacerbation of ventricular arrhythmias during the postoperative period after implantation of an automatic defibrillator. J Am Coll Cardiol. 1991;18:1200-1206. [Abstract]
  10. Hii JT, Gillis AM, Wyse DG, Sheldon RS, Duff HJ, Mitchell LB. Risks of developing supraventricular and ventricular tachyarrhythmias after implantation of a cardioverter-defibrillator, and timing the activation of arrhythmia termination therapies. Am J Cardiol. 1993;71:565-568. [Medline] [Order article via Infotrieve]
  11. Mosteller RD, Lehmann MH, Thomas AC, Jackson K. Operative mortality with implantation of the automatic cardioverter-defibrillator. Am J Cardiol. 1991;68:1340-1345.[Medline] [Order article via Infotrieve]
  12. Saksena S. Defibrillation thresholds and perioperative mortality associated with endocardial and epicardial defibrillation lead systems: the PCD investigators and participating institutions. PACE Pacing Clin Electrophysiol. 1993;16:202-207. [Medline] [Order article via Infotrieve]
  13. Winter J, Vester EG, Kuhls S, Kantartzis M, Perings C, Pauschinger M, Strauer BE, Bircks W. Defibrillation energy requirements with single endocardial (Endotak) lead. PACE Pacing Clin Electrophysiol. 1993;16:540-546. [Medline] [Order article via Infotrieve]
  14. Fromer M, Brachmann J, Block M, Siebels J, Hoffmann E, Almendral J, Ohm OJ, den Dulk K, Coumel P, Camm J, et al. Efficacy of automatic multimodal device therapy for ventricular tachyarrhythmias as delivered by a new implantable pacing, cardioverter-defibrillator: results of a European multicenter study incorporating 102 implants. Circulation. 1992;86:363-374. [Abstract/Free Full Text]
  15. Bardy GH, Hofer B, Johnson G, Kudenchuk PJ, Poole JE, Dolack GL, Gleva M, Mitchell R, Kelso D. Implantable transvenous cardioverter-defibrillators. Circulation. 1993;87:1152-1168.[Abstract/Free Full Text]
  16. Fotuhi P, Alt E, Mestre E, Callihan R, Dixon-Tullock E, Schömig A, Ideker R. Improved defibrillation thresholds with a new epicardial electrode made of braided carbon compared to a standard epicardial patch. Circulation. 1993;88(suppl I):I-216. Abstract.
  17. Bach SM Jr, Barstad J, Harper N, Mayer D, Moser S, Smutka M, Theis R, Wollins J. Initial clinical experience: Endotak—implantable transvenous defibrillator system. J Am Coll Cardiol. 1989;13:65A. Abstract.
  18. Fotuhi P, Alt E, Callihan R, Melnick S, Mestre E, Rollins D, Ideker R. Endocardial carbon braid electrodes: new approach to lowering defibrillation thresholds. Circulation. 1993;88(suppl I):I-593. Abstract.
  19. Tang ASL, Yabe S, Wharton JM, Dolker M, Smith WM, Ideker RE. Ventricular defibrillation using biphasic waveforms: the importance of phasic duration. Am Coll Cardiol. 1989;13:207-214. [Abstract]
  20. Babbs CF. Effect of pentobarbital anesthesia on ventricular defibrillation threshold in dogs. Am Heart J. 1978;95:331-337. [Medline] [Order article via Infotrieve]
  21. Gill RM, Sweeney RJ, Reid PR. The defibrillation threshold: a comparison of anesthetics and measurement methods. PACE Pacing Clin Electrophysiol. 1993;16:708-714. [Medline] [Order article via Infotrieve]
  22. Davy JM, Fain ES, Dorian P, Winkle RA. The relationship between successful defibrillation and delivered energy in open-chest dogs: reappraisal of the `defibrillation threshold' concept. Am Heart J. 1987;113:77-84. [Medline] [Order article via Infotrieve]
  23. McDaniel WC, Schuder JC. The cardiac ventricular defibrillation threshold: inherent limitations in its application and interpretation. Med Instrum. 1987;21:170-176. [Medline] [Order article via Infotrieve]
  24. Bourland JD, Tacker WA Jr, Geddes LA. Strength-duration curves for trapezoidal waveforms of various tilts for transchest defibrillation in animals. Med Instrum. 1978;12:38-41. [Medline] [Order article via Infotrieve]
  25. Hollander M, Wolfe DA. Nonparametric Statistical Methods. New York, NY: John Wiley & Sons; 1973:138-184.
  26. Mugica J, Henry L, Attuel D, Lazarus B, Duconge R. Clinical experience with 910 carbon tip leads: comparison with polished platinium leads. PACE Pacing Clin Electrophysiol. 1986;9:1230-1238. [Medline] [Order article via Infotrieve]
  27. Mund K, Richter G, Weidlich E, Fahlström U. Electrochemical properties of platinum, glassy carbon and pyrographite as stimulating electrodes. PACE Pacing Clin Electrophysiol. 1986;9:1225-1229. [Medline] [Order article via Infotrieve]
  28. Alt E, Theres H, Heinz M, Albrecht K, Georg H, Blömer H. A new approach towards defibrillation electrodes: highly conductive isotropic carbon fibers. PACE Pacing Clin Electrophysiol. 1991;14:1923-1928. [Medline] [Order article via Infotrieve]
  29. Dixon EG, Tang ASL, Wolf PD, Meador JT, Fine MJ, Calfee RV, Ideker RE. Improved defibrillation thresholds with large contoured epicardial electrodes and biphasic waveforms. Circulation. 1987;76:1176-1184. [Abstract/Free Full Text]
  30. Guse PA, Kavanagh KM, Alferness CA, Wolf PD, Rollins D, Hagler J, Smith WM, Ideker RE. Defibrillation with low voltage using a left ventricular catheter and four cutaneous patch electrodes in dogs. PACE Pacing Clin Electrophysiol. 1991;14:443-451. [Medline] [Order article via Infotrieve]
  31. Kallok MJ. The influence of opening the thorax on defibrillation threshold in canines. PACE Pacing Clin Electrophysiol. 1989;12:70-79. [Medline] [Order article via Infotrieve]
  32. Zipes DP, Fischer J, King RM, Nicoll A, Jolly WW. Termination of ventricular fibrillation in dogs by depolarizing a critical amount of myocardium. Am J Cardiol. 1975;36:37-44. [Medline] [Order article via Infotrieve]
  33. Chen P-S, Wolf PD, Claydon FJ III, Dixon EG, Vidaillet HJ Jr, Danieley ND, Pilkington TC, Ideker RE. The potential gradient field created by epicardial defibrillation electrodes in dogs. Circulation. 1986;74:626-636. [Abstract/Free Full Text]
  34. Tang ASL, Wolf PD, Afework Y, Smith WM, Ideker RE. Three-dimensional potential gradient fields generated by intracardiac catheter and cutaneous patch electrodes. Circulation. 1992;85:1857-1864. [Abstract/Free Full Text]
  35. Beckman DJ, Crevey BJ, Foster PR, Bandy M, Evans M. Subxiphoid approach for implantable cardioverter defibrillator in patients with previous coronary bypass surgery. PACE Pacing Clin Electrophysiol. 1992;15:1637-1638. [Medline] [Order article via Infotrieve]
  36. Frumin H, Goodman GR, Pleatman M. ICD implantation via thoracoscopy without the need for sternotomy or thoracotomy. PACE Pacing Clin Electrophysiol. 1993;16:257-260.[Medline] [Order article via Infotrieve]



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