Open access peer-reviewed chapter

Defibrillator Threshold Testing

Written By

Munir Zaqqa

Submitted: July 14th, 2012 Reviewed: August 22nd, 2012 Published: January 9th, 2013

DOI: 10.5772/52594

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1. Introduction

Since implantable cardioverter-defibrillators (ICDs) were first introduced, defibrillator threshold (DFT) testing was considered an integral part of the implant procedure. Performing DFT testing verifies the ability of the ICD in detecting and aborting the lethal arrhythmia it was designed to treat. The process has evolved with the development of the ICD’s and the expanding indications for their usage. Recent studies even questioned the need for DFT assessment. Currently this matter is controversial with no firm guidelines. In this chapter we present the basic information on DFT testing, how to manage high DFT, and then discuss the evidence for and against performing the test.


2. DFT concept

DFT testing is performed by inducing ventricular arrhythmia and then finding the minimal amount of energy delivered by the ICD to defibrillate the myocardium back to sinus rhythm. Central to the concept of determining the DFT, was the discovery since 1930, that electrical shocks themselves can induce ventricular fibrillation (VF) [1]. By giving a shock during the vulnerable period of repolarization, VF could be reproducibly induced. Ventricular tachycardia (VT) may also be induced, but in a relatively small percentage of patients [2]. As the amount of energy delivered during the vulnerable period is increased, a threshold is reached that does not induce VF [3]. This is called the upper limit of vulnerability (ULV) and is proportional to DFT value [4-5]. This concept can be used as a surrogate for DFT [6-7]. Instead of inducing VF and checking the threshold at which it terminates, a different protocol is used that delivers variable strengths of shocks during the vulnerable T-wave phase and then establishes ULV. As compared to regular DFT test, ULV test is done during sinus rhythm and not during VF. Using this approach there is a need for more number of shocks, but less number of times that VF are induced.

The threshold to terminate ventricular fibrillation with ICD’s is usually in the 5 to 30 J range. It was the ability to reduce the energy requirements by 10 folds as compared to external defibrillator that made the ICD a reality [8]. Otherwise the size of the ICD would have to be much bigger to store the needed energy for defibrillation. Although the threshold is expressed in relation to the energy discharged by the ICD, in reality it is the voltage and its duration that is the critical factor in defibrillation [9-10]. Duration has a relatively narrow range to be effective (in the range of few milliseconds). To achieve this precise phase duration of defibrillation, the capacitor discharge is truncated in either a tilt based formula which truncates the discharge after a certain percentage of decay in the voltage has been reached, or more simply in a time based manner after a certain time has elapsed. Voltage is usually in the hundreds of volts range. If voltage is too low it may induce rather than terminate fibrillation as explained earlier. High voltage (above 1000 Volts) is also not without its risks, as it may result in stunning of the myocardium and subsequent electromechanical dissociation [11-12]. The voltage wave form can be manipulated to make defibrillation more effective and therefore require less energy. Biphasic wave, which is the standard now in ICD’s, has reversal of the initial polarity. The initial wave results in charging of the cell membrane as a result of the voltage gradient. The reversal which is termed “burping” is theorized to absorb the initial energy and therefore avoid proarrhythmia [11-12]. The biphasic wave form can be manipulated by changing the initial voltage, and by changing the duration and the ratio of its waves. Different manufactures use different formulas in their devices, and some allow changing of the parameters by the electrophysiologists in case of high DFT.


3. Performing DFT testing

Before doing DFT testing, consent should be taken from the patient explaining the risk and benefit of the procedure. Vital signs should be stable and basic lab results such as electrolytes should be within normal range. There should be no contraindication to performing the test such as severe aortic stenosis or intracavitary thrombus. An external defibrillator should be placed ready next to the patient, preferably with defibrillator patches attached to the patient. As the shock is painful, adequate sedation or short anesthesia should be given with careful monitoring of vital signs and saturation level [14].

After the device is implanted good lead position should be verified by X-ray. The lead is tested to ensure adequate sensing and pacing thresholds and normal impedance values.

Prior to VF induction, the device is activated and programmed with the amount of energy to be delivered. Ventricular fibrillation is usually induced via the device. There are several methods of VF induction such as programmed ventricular stimulation, T wave shock, fast burst pacing, or by applying low voltage direct current [15]. Following VF induction the patient is monitored carefully until the device detects the arrhythmia and restores it back to sinus rhythm. If the device fails, external defibrillation should be immediately performed.

To find the exact DFT value, this process has to be repeated several times with either a step up, step down, or a binary fashion until DFT or ULV are found [16-17]. Although the term threshold should indicate a value above which defibrillation is successful and below which shocks fail, in reality DFT is a probabilistic phenomenon with a certain percentage of success rate [17-18]. One shock may be successful while a successive one with the same conditions may fail [5]. Despite the poor reproducibility of DFT, it is still a useful parameter, as this value taken with a safety margin above it, gives a high clinical success of VF termination. The standard safety margin is 10 J, although 5 J may be enough [19-20].

DFT testing with several shocks and titrations may be useful in a research protocol, where the exact value has important clinical significance. A simpler, yet safe approach is the defibrillator safety margin (DSM) test [21]. In this method, a single or two VF inductions may be enough. The device is usually programmed to a value that is expected to restore sinus rhythm following induction. This value depends on the operator preference. It is usually an average value that is at least 10 J below the maximum output of the device [22]. If it is successful, then this value should at least be equal to the DFT value. If the shock fails, then step up approach has to be used to find the threshold.

Kelly et al [23]1988945.3%
Winkle et al [24]19892702.6%
Pinski et al [25]199112518%
Epstein et al [26]199219464.6%
Gold et al [27]19971148%
Brodsky et al [28]19997643.1%
Shukla et al [29]200396811%
Russo et al [30]200511396.2%
Theuns et al [31]200512714%
Mainigi et al [32]200612112%
Guenther et al [33]20129751.4%
Cheng et al [34]20122435.3%

Table 1.

Incidence of high DFT

High DFT, defined in most studies as a threshold of < 10 J below the maximum output of the device, is estimated to occur in about 5% of ICD implants (range 1.4 to 18%) (Tables 1) [23-33]. Although the exact value of DFT cannot be predicted in an individual patient prior to testing, there are some clinical parameters associated with increased thresholds (Table 2) [27-29,32-35].

Young age
Low ejection fraction
Hypertrophic cardiomyopathy
Non coronary artery disease
Medications (specially amiodarone)
Larger and small left ventricular sizes
Large body size
Prolonged QRS duration

Table 2.

Clinical factors associated with high DFT ‘s

DFT testing is usually performed introperatively at the time of implant before the pocket is closed to allow intervention in case of high thresholds. Sometimes it is done at the time of discharge or at a later time when the lead has assumed a stable position [28,36].


4. Management of high DFT

If a patient is found to have elevated thresholds, the initial step is to verify that this is not caused by a reversible problem related to the implant procedure itself (table 3). If no reversible cause is found, then there are several options available. These are classified into non-invasive and invasive methods (table 4).

Pericardial effusion
Large pleural effusion
Pulmonary edema
Sedation related such as aspiration and hypoxia
Electrolyte imbalance
Prolonged procedure
Lead dislodgment

Table 3.

Reversible causes of high DFT

Adjustment to improve DFTComment
Non Invasive
Medications [37-41]Particularly amiodarone has been shown to increase thresholds. Medications that potentially decrease thresholds include sotalol and dofetilide.
Lead Polarity [43-44]The RV lead is the anode (positive) vector. It may be changed to cathode (negative).
Vector of defibrillation [41,45]Adding an SVC coil is most effective when a single coil has high resistance of > 58 ohm. If dual coil system is implanted, the vector can be changed electronically.
Wave form [41,46]Change of Tilt and phase duration of shocks is available in some devices and may be optimized individually.
Lead repositioning [47-48]Apical position has lower DFT when compared to a proximal position. Septal and RVOT positions may have lower thresholds
Addition of extra leads to change the vector of the shock [49-51].Subcutaneous array, coronary sinus and azygous vein leads could be introduced to lower thresholds
Upgrading to higher output device

Table 4.

Approaches to improve DFT

Changing or stopping a medication associated with high threshold may help the problem [37]. Amiodarone has been particularly quoted in the literature as causing high thresholds [38]. Other possible medications include lidocaine and verapamil. On the other hand, medications that do not affect or potentially reduce DFT include sotalol, dofetilide, beta-blocker and dronedarone [37-40].

There are some programmable parameters in the ICD that can affect DFT. These include polarity of the lead, the vector of defibrillation, and the tilt and duration of the shock wave [41-42]. The lead is configured with an anodal (positive) distal coil. This configuration results in an average reduction of 15% in DFT as compared to a cathodal right ventricular (RV) coil [43]. Reversing it to cathode results in the energy propagating away from the lead instead of “collapsing” towards it. This is theorized to increase the arrhythmia potential. However, changing polarity has been shown to decrease DFT in some of the patients and this configuration can therefore be attempted [44].

A dual-coil, active pectoral lead system is the most commonly used configuration. A proximal coil placed in the superior vena cava (SVC) area has been found to decrease DFT as compared to a single coil system [41,45]. This effect is particularly effective when the single coil resistance is high (above 58 ohm), while the effect on the threshold is mixed with low single coil resistance. Control of proximal coil can be done electronically in a dual coil lead. Addition of an SVC coil might be considered in patients with single coil and high resistance. The proximal coil location should be in the high SVC and brachiocephalic area rather than the low SVC and atrial area as the later is associated with higher DFT value [45].

The phase duration of defibrillation is critical in achieving sinus rhythm [9-10]. The optimal phase duration is not exactly known and it can be optimized in some devices for individual patients with high DFT’s [46].

Changing a nominal parameter should not be taken lightly, as these are the ones tested and proven with clinical research. Any adjustment made to the settings should be verified by repeated induction and the reassurance of a successful defibrillation.

Several invasive choices that reduce DFT are available. Changing the RV lead location may reduce DFT. The standard RV position is the RV apex. This has the advantage of a stable position and good threshold. Alternative lead positions that have good thresholds are the right ventricular outflow tract (RVOT) and the septum. An active fixation system should be used in these areas. A right free wall position has the highest DFT [47-48]. Changing the shock vector may lower DFT. This can be achieved by incorporating subcutaneous array or an additional lead in the azygous vein or the coronary sinus [49-51]. Upgrading to higher output devices may be useful in patients with borderline elevated thresholds.


5. The arguments for and against performing DFT testing

Since implanting ICD’s in the early 1980’s, VF induction and testing the device ability to restore sinus rhythm not only helped in determining DFT’s, but also allowed testing of the sensing capability of the device, the ability of the programmed algorithm to recognize the arrhythmia, and the ability of the capacitors to deliver the stored energy. This was an important step in testing a new device that is designed to treat a lethal arrhythmia. Patients who were found to have high threshold had intervention performed to attempt to lower the DFT’s. If the thresholds could not be lowered then many physicians did not implant the device. This was because of the concern that a shock might change a stable VT into VF and then not be able to terminate it. There were several reports of increased mortality in patients with high DFT and case reports of deaths due to failed defibrillation. [23,28,52-54] (table 5). Intuitively, finding DFT will result in reduced mortality as it allows the recognition of patients who will not respond to the shock and therefore find a subgroup of patients who need further intervention. However, this matter is not so simple.

Testing involves induction of ventricular fibrillation in patients with significant heart disease with a potential for morbidity and mortality. Complications associates with DFT testing include worsening heart failure, hemodynamic compromise, cerebrovascular accidents and even deaths. In the Canadian Experience study by Bernie et al which looked at 19,067 patients, thirty five patients (0.18%) had serious complications [61]. The recognition of the complications was coupled with improvements in the lead and defibrillator technology. In addition, ICD use expanded considerably after studies showed its benefit not only in secondary but also in primary prevention of sudden death. This changed the risk benefit ratio of DFT testing. Several studies gradually emerged that questioned the need to find DFT (table 5). This lack of benefit of DFT testing shown in several studies may be explained by several factors:

  • The comparison of the mortality in patients who had DFT testing versus those who did not have a test may be a biased by excluding unstable patients from DFT testing and including them in the non tested group.

  • The comparison should include the morbidity and mortality associated with the test itself and also the problems related to the intervention to reduce DFT. Even simple measures such as changing a medication and reprogramming the ICD could have an impact on mortality, not to mention possible complications associated with invasive interventions. The shock itself done during the test may have an impact on patients with established cardiac disease. Defibrillation has been shown to increase troponin level [62]. Any shock, even when inappropriate, has been associated with increased mortality [63].

  • DFT does not predict future successful defibrillation in a reliable manner [18]. This may be related to the probabilistic nature of the test. It has also been shown that DFT change acutely and chronically [64-65]. This could result in the improvement of high DFT, but may also result in a patient with normal DFT developing high thresholds with time. It is estimated that about 29% of deaths in ICD recipients are still due to arrhythmias that could not be terminated by the ICD [66].

  • Ventricular fibrillation induced in the hospital is not the same as the real world arrhythmia. Induced VF tends to be more organized than spontaneous VF [67]. In the clinical setting, many patients have ventricular tachycardia rather than VF or even do not have any arrhythmia at all during the lifetime of the implant [2,68-69]. For these patients DFT test may be misleading or may not have any relevance at all.

It is therefore important to have to prospective randomized study to give us a clear answer. One prospective, but not randomized study (SAFE-ICD) showed no benefit of DFT testing [60]. The result of an ongoing study (SIMPLE trial) may give a more clear direction once finished [70].

The approach to DFT testing has changed over time. A recent study in 111 Italian centers over the period 2007 to 2010 involving 2,082 patients documented the trend change [71]. It reported DFT testing to be performed in 38% of patients with the incidence declining annually from 36% in 2007 to 28% in 2010. In 13% of centers, the test was performed routinely, and in 38% it was not performed at all. The reasons for not performing DFT testing in this survey were the policy of the center in 44%, a primary indication for the implant in 31% and doing a device replacement in 15%. Not doing DFT testing can certainly make the ICD implant simpler. The simplification is not just related to the procedure itself, but starts with the initial step of taking the consent from the patient. It is not a simple task to explain the risk to the patient in a lay term without confusing him. A physician has to explain that after the surgery has finished successfully, there will be a need to stop the heart; and that there is a chance, even though very small, that he may have a problem like stroke or that we may not be able to restore his heart to beat back again.

Favor DFT testing
Marchlinski et al[54]198833Patients with low DFT (n=19) had 100% success rate of clinical arrhythmia termination as compared to 73% (n=14) in the high threshold group
Pires et al[22]2006835Long term survival was lower in the no DFT testing group (n=203) in comparison to DFT and safety margin testing (n=632)
Hall et al[55]2007112Higher mortality seen in patients who did not have DFT testing because of contraindication (n=55) as compared to a random sample who had DFT testing performed (n=57)
Against DFT testing
Epstein et al[26]19921946There was improved mortality among patients with high DFT who received ICD (n=71) versus those who did not receive ICD (n=16)
Russo et al[30]20051139No difference in mortality among patients with high DFT who had intervention (n=34) versus who did not have intervention (n=37)
Blatt et al[56]2008717No difference in mortality between lower (< or =10 J) (n=547) versus higher (n=170) DFT groups
Bianchi et al[57]2009291No difference in mortality between Italian centers that perform DFT testing routinely (n=137) versus centers that do not perform DFT testing (n=154)
Michowitz et al[58]2011256No difference in mortality between CRT-D patient who had DFT testing (n=204) versus who did not have DFT testing (n=52)
Codner et al[59]2012213No difference in mortality between DFT testing (n=80) and no DFT testing (n=133) groups
Brignole et al[60]20122120Prospective but non randomized evaluation of DFT testing (n=836) versus no DFT testing (n=1284) showed no difference in mortality

Table 5.

Studies favoring and against DFT testing.


6. Conclusion

The approach to DFT testing has changed since ICD’s were first introduced. It has changed from being an essential part performed in all the patients to being done in less than one third of the patients at current time. The need for DFT testing is a balance between benefit and risk with studies showing conflicting results. Most recent studies show equal benefit risk ratio for DFT testing. A prospective randomized study is needed to resolve the issue and there is currently one being performed. When this study is finished it should give a more clear answer regarding this issue.


  1. 1. WiggersC. J.WegriaR.1940Ventricular fibrillation due to single, localized induction and condenser shocks applied during the vulnerable phase of ventricular systole.Am J Physiol128500505
  2. 2. ZimaE.GergelyM.Soó al.2006The effect of induction method on defibrillation threshold and ventricular fibrillation cycle lengthJ Cardiovasc Electrophysiol.Apr17437781
  3. 3. YashimaM.KimY. al.2003On the mechanism of the probabilistic nature of ventricular defibrillation thresholdAm J Physiol Heart Circ Physiol.Jan2841H24955
  4. 4. DayJ. D.DoshiR. N.BelottP.Birgersdotteret al.2007Inductionless or limited shock testing is possible in most patients with implantable cardioverter- defibrillators/cardiac resynchronization therapy defibrillators: results of the multicenter ASSURE Study (Arrhythmia Single Shock Defibrillation Threshold Testing Versus Upper Limit of Vulnerability: Risk Reduction Evaluation With Implantable Cardioverter-Defibrillator Implantations).Circulation.May 8;1151823829
  5. 5. SwerdlowC. al.1996Comparative reproducibility of defibrillation threshold and upper limit of vulnerability.Pacing Clin Electrophysiol.Dec1912 Pt 1210311
  6. 6. HwangC.SwerdlowC. D.KassR. al.1994Upper limit of vulnerability reliably predicts the defibrillation threshold in humans.Circulation.Nov905230814
  7. 7. SwerdlowC. D.AhernT.KassR. al.1996Upper limit of vulnerability is a good estimator of shock strength associated with 90% probability of successful defibrillation in humans with transvenous implantable cardioverter-defibrillators.J Am Coll Cardiol.Apr27511128
  8. 8. MirowskiM.MowerM. M.ReidP. al.1982The automatic implantable defibrillator. New Modality for treatment of life-threatening ventricular arrhythmias.Pacing Clin Electrophysiol.May53384401
  9. 9. KrollM. W.SwerdlowC. D.2007Optimizingdefibrillation waveforms for ICDs.J Interv Card Electrophysiol.Apr18324763Epub 2007 Jun 1. Review.
  10. 10. al.2010High defibrillation threshold: the science, signs and solutionsIndian Pacing Electrophysiol J.Jan 71012139
  11. 11. MitchellL. B.PinedaE. al.2002Sudden death in patients with implantable cardioverter defibrillators: The importance of post-shock electromechanical dissociation.Journal of the American College of Cardiology3913231328
  12. 12. XieJ.WeilM. al.1997High-energy defibrillation increases the severity of postresuscitation myocardial dysfunction.CirculationJul 15;9626838
  13. 13. SwerdlowC. D.FanW.BrewerJ. E.1996Charge-burping theory correctly predicts optimal ratios of phase duration for biphasic defibrillation waveforms.Circulation.Nov 1949227884
  14. 14. Marquié al.2007Can we implant cardioverter defibrillator under minimal sedation?Europace.Jul9754550
  15. 15. EulerD. E.WhitmanT. A.RobertsP. al.1999Low voltage direct current delivered through unipolar transvenous leads: an alternate method for the induction of ventricular fibrillation.Pacing Clin Electrophysiol.Jun226 Pt 190814
  16. 16. ShorofskyS. R.PetersR. W.RashbaE. al.2004Comparison of step-down and binary search algorithms for determination of defibrillation threshold in humans.Pacing Clin Electrophysiol.Feb27221820
  17. 17. SwerdlowC. D.RussoA. M.DegrootP. J.2007The dilemma of ICD implant testing.Pacing Clin Electrophysiol.May305675700Review.
  18. 18. DegrootP. J.ChurchT. al.1997Derivation of a defibrillator implant criterion based on probability of successful defibrillation.Pacing Clin Electrophysiol.Aug208 Pt 192435
  19. 19. MarchlinskiF. E.FloresB.MillerJ. al.1988Relation of the intraoperative defibrillation threshold to successful postoperative defibrillation with an automatic implantable cardioverter defibrillator.Am J Cardiol.Sep 16273938
  20. 20. GoldM. al.2002Efficacy and temporal stability of reduced safety margins for ventricular defibrillation: primary results from the Low Energy Safety Study (LESS).Circulation.Apr 301051720438
  21. 21. al.2005One conversion of ventricular fibrillation is adequate for implantable cardioverter-debibrillator implant: An analysis from the low energy safety study (LESS).Heart Rhythm211722
  22. 22. PiresL. A.2007Defibrillation testing of the implantable cardioverter defibrillator: when, how, and by whom?Indian Pacing Electrophysiol J.Aug 17316675
  23. 23. KellyP. A.CannomD. al.1988The automatic implantable cardioverter-defibrillator: efficacy, complications and survival in patients with malignant ventricular arrhythmias.J Am Coll Cardiol.Jun116127886
  24. 24. WinkleR. A.MeadR. H.RuderM. al.1989Long-term outcome with the automatic implantable cardioverter-defibrillator.J Am Coll Cardiol.May136135361
  25. 25. PinskiS. L.VanerioG.CastleL. al.1991Patients with a high defibrillation threshold: Clinical characteristics, management, and outcome.Am Heart J1221 Pt 18995
  26. 26. EpsteinA. E.EllenbogenK. A.KirkK. al.1992Clinical characteristics and outcome of patients with high defibrillation thresholds.A multicenter study. Circulation.Oct864120616
  27. 27. GoldM. R.KhalighiK.KaveshN. al.1997Clinical predictors of transvenous biphasic defibrillation thresholds.Am J Cardiol.Jun 15791216237
  28. 28. BrodskyC. M.ChangF.VlayS. C.1999Multicenter evaluation of implantable cardioverter defibrillator testing after implant: the Post Implant Testing Study (PITS).Pacing Clin Electrophysiol.Dec2212176976
  29. 29. ShuklaH. H.FlakerG. al.2003High defibrillation thresholds in transvenous biphasic implantable defibrillators: clinical predictors and prognostic implications.Pacing Clin Electrophysiol.Jan261 Pt 1448
  30. 30. RussoA. M.SauerW.GerstenfeldE. al.2005Defibrillation threshold testing: is it really necessary at the time of implantable cardioverter-defibrillator insertion?Heart Rhythm.May2545661
  31. 31. TheunsD. A.Szili-TorokT.JordaensL. J.2005Defibrillation efficacy testing: long-term follow-up and mortality.Europace.Nov7650915
  32. 32. MainigiS. K.CooperJ. M.RussoA. al.2006Elevated defibrillation thresholds in patients undergoing biventricular defibrillator implantation: incidence and predictors.Heart Rhythm.Sep3910106
  33. 33. GuentherM.RauwolfT.BrüggemannB.Gerlach2012Pre-hospital discharge testing after implantable cardioverter defibrillator implantation: a measure of safety or out of date? A retrospective analysis of 975 patientsEuropaceFeb14221723
  34. 34. al.2012Incidence and clinical predictors of low defibrillation safety margin at time of implantable defibrillator implantationJ Interv Card Electrophysiol.Jun34193100
  35. 35. QuinE. M.CuocoF. A.ForcinaM. al.2011Defibrillation thresholds in hypertrophic cardiomyopathy.J Cardiovasc Electrophysiol.May22556972
  36. 36. GoldbergerJ. al.1997Utility of predischarge and one-month transvenous implantable defibrillator tests.Am J Cardiol79822e6
  37. 37. DoppA. L.MillerJ. M.TisdaleJ. E.2008Effect of drugs on defibrillation capacity.Drugs68560730Review
  38. 38. HohnloserS. al.2006Effect of amiodarone and sotalol on ventricular defibrillation threshold: the optimal pharmacological therapy in cardioverter defibrillator patients (OPTIC) trial.CirculationJul 1111421049
  39. 39. SimonR. D.SturdivantJ. L.LemanR. al.2009The effect of dofetilide on ventricular defibrillation thresholds.Pacing Clin Electrophysiol.Jan321248
  40. 40. al.2012Chronic oral amiodarone but not dronedarone therapy increases ventricular defibrillation threshold during acute myocardial ischemia in a closed-chest animal modelJ Cardiovasc Pharmacol.Jun5965238
  41. 41. KrollM. W.SchwabJ. O.2010Achieving low defibrillation thresholds at implant: pharmacological influences, RV coil polarity and position, SVC coil usage and positioning, pulse width settings, and the azygous vein.Fundam Clin Pharmacol.Oct;2455617310.1111/j.1472-8206.2010.00848.x.Review
  42. 42. al.2010High defibrillation threshold: the science, signs and solutionsIndian Pacing Electrophysiol J.Jan 71012139
  43. 43. OlsovskyM. R.ShorofskyS. R.GoldM. R.1998Effect of shock polarity on biphasic defibrillation thresholds using an active pectoral lead system.J Cardiovasc Electrophysiol.Apr943504
  44. 44. ZienciukA.LubińskiA.Kró al.2007Effects of shock polarity reversal on defibrillation threshold in an implantable cardioverter-defibrillator.Kardiol Pol.May655495500
  45. 45. GoldM.Val-MejiasJ.LemanR. al.2008Optimization of superior vena cava coil position and usage for transvenous defibrillationHeart Rhythm5394
  46. 46. DenmanR. A.UmesanC.MartinP. al.2006Benefit of millisecond waveform durations for patients with high defibrillation thresholdsHeart RhythmMay3553641
  47. 47. CrossleyG. al.2009A prospective randomized trial of defibrillation thresholds from the right ventricular outflow tract and the right ventricular apexPacing Clin Electrophysiol.Feb32216671
  48. 48. YangF.PattersonR.2008Optimal transvenous coil position on active-can single-coil ICD defibrillation efficacy: a simulation studyAnn Biomed Eng36165967
  49. 49. al.2001Comparison of the efficacy of a subcutaneous array electrode with a subcutaneous patch electrode, a prospective randomized study.Int. J. Cardiol.78247
  50. 50. SeowS. C.TolentinoC. al.2011Azygous vein coil lowers defibrillation threshold in patients with high defibrillation thresholdEuropaceJun1368258
  51. 51. al.2010Coronary sinus shocking lead as salvage in patients with advanced CHF and high defibrillation thresholdsPacing Clin Electrophysiol.Aug33896772
  52. 52. LehmannM. al.1994Sudden death in recipients of first generation implantable cardioverter defibrillators: Analysis of terminal eventsParticipating investigators. J Interv Cardiol75487503
  53. 53. WinkleR. A.MeadR. H.RuderM. A. Gaudiani1989Long-term outcome with the automatic implantable cardioverter-defibrillator.J Am Coll Cardiol.May136135361
  54. 54. MarchlinskiF. E.FloresB.MillerJ. al.1988Relation of the intraoperative defibrillation threshold to successful postoperative defibrillation with an automatic implantable cardioverter defibrillator.Am J Cardiol.Sep 16273938
  55. 55. al.2007Comparison of outcomes in patients undergoing defibrillation threshold testing at the time of implantable cardioverter-defibrillator implantation versus no defibrillation threshold testing.Cardiol J1454639
  56. 56. BlattJ. A.PooleJ. E.JohnsonG. al.2008SCD-HeFT Investigators. No benefit from defibrillation threshold testing in the SCD-HeFT (Sudden Cardiac Death in Heart Failure Trial).J Am Coll Cardiol.Aug 125275516
  57. 57. BianchiS.RicciR. al.2009Primary prevention implantation of cardioverter defibrillator without defibrillation threshold testing: 2-year follow-upPacing Clin Electrophysiol.May3255738
  58. 58. al.2011Defibrillation threshold testing fails to show clinical benefit during long-term follow-up of patients undergoing cardiac resynchronization therapy defibrillator implantationEuropaceMay1356838
  59. 59. CodnerP.NevzorovR.KusniecJ. Haim2012Implantable cardioverter defibrillator with and without defibrillation threshold testingIsr Med Assoc J.Jun1463436
  60. 60. BrignoleM.OcchettaE.BongiorniM. al.2012SAFE-ICD Study Investigators. Clinical Evaluation of Defibrillation Testing in an Unselected Population of 2,120 Consecutive Patients Undergoing First Implantable Cardioverter-Defibrillator Implant.J Am Coll Cardiol.Jul 24.
  61. 61. al.2008Complications Associated with Defibrillation Threshold Testing: The Canadian ExperienceHeart Rhythm5387390
  62. 62. JoglarJ. A.KesslerD. J.WelchP. al.1999Effects of repeated electrical defibrillations on cardiac troponin I levels.Am J Cardiol83270272A6.
  63. 63. DaubertJ. P.ZarebaW.CannomD. S.2008MADIT II Investigators. Inappropriate implantable cardioverter-defibrillator shocks in MADIT II: frequency, mechanisms, predictors, and survival impact.J Am Coll Cardiol.Apr 85114135765
  64. 64. SchwartzmanD.CallansD. J.GottliebC. al.1996Early postoperative rise in defibrillation threshold in patients with nonthoracotomy defibrillation lead systems: Attenuation with biphasic shock waveforms.J Cardiovasc Electrophysiol76483493
  65. 65. VendittiF. J.JrMartinD. al.1994Rise in chronic defibrillation thresholds in nonthoracotomy implantable defibrillator.Circulation891216223
  66. 66. MitchellL. B.PinedaE. A.TitusJ. al.2002Sudden death in patients with implantable cardioverter defibrillators: The importance of post-shock electromechanical dissociation.J Am Coll Cardiol39813231328
  67. 67. LeverN. A.NewallE. G.LarsenP. D.2007Differences in the characteristics of induced and spontaneous episodes of ventricular fibrillation.Europace910541058
  68. 68. WathenM. S.De GrootP. J.SweeneyM. al.2004Prospective randomized multicenter trial of empirical antitachycardia pacing versus shocks for spontaneous rapid ventricular tachycardia in patients with implantable cardioverter-defibrillators: Pacing Fast Ventricular Tachycardia Reduces Shock Therapies (Pain-FREE Rx II) trial results.Circulation11025912596
  69. 69. TrappeH. al.1997Long-term follow up of patients with implantable cardioverter-defibrillators and mild, moderate, or severe impairment of left ventricular functionHeartSep7832439
  70. 70. HealeyJ. S.HohnloserS. al.2012The rationale and design of the Shockless IMPLant Evaluation (SIMPLE) trial: A randomized, controlled trial of defibrillation testing at the time of defibrillator implantationAm Heart J.Aug164214652
  71. 71. StefanoB.PietroR. al.2011Defibrillation testing during implantable cardioverter-defibrillator implantation in Italian current practice: the Assessment of Long-term Induction clinical ValuE (ALIVE) projectAm Heart J.Aug16223907

Written By

Munir Zaqqa

Submitted: July 14th, 2012 Reviewed: August 22nd, 2012 Published: January 9th, 2013