Approximately five to ten percent of patients who receive implantable cardioverter defibrillators (ICDs) will experience high defibrillation thresholds (DFTs) at implant.1, 2 In addition, an unknown number of ICD patients will experience rising DFTs due to disease progression and/or changes in drug regimens.
DeFT Response Technology is engineered to help physicians and health care professionals respond to problematic high DFTs quickly and skillfully.
St. Jude Medical’s portfolio of advanced options offers clinically proven, non-invasive, front-line approaches to managing high DFTs, including:
- Programmable Pulse Widths - Designed to deliver energy efficiently.
- Programmable Tilt - Although tilt has questionable clinical value,3 St. Jude Medical ICDs offer programmable tilts for those physicians who are not yet familiar with the concepts of programmable pulse widths. Research has yet to determine a tilt that is optimal for all patients.
- Programmable Polarity - Unlike some manufacturers, St. Jude Medical ICDs start with an optimized polarity; however, the option to re-program polarity is available.
- Programmable Shocking Vectors - Change the shocking vector by pressing a button to remove or add the SVC coil.
- Unsurpassed Delivered Energy (36 J) - No other devices on the market deliver more energy than St. Jude Medical ICDs.
Facts about high DFTs
- Optimizing the defibrillation waveform pulse widths may result in lower DFTs in patients with high DFTs4, 5
- Up to 6% of all ICD patients may lose a significant portion of their safety margin due to the combined effects of lead system maturation and concomitant amiodarone use6
- Defibrillation thresholds and rates of sudden arrhythmic death are significantly higher in patients with chronic kidney disease compared to those without7
- Chronic amiodarone therapy may increase defibrillation energy requirements by approximately 62%8
- Acute amiodarone loading may cause DFTs to rise9
- Biphasic shocks with a shorter second phase may lower DFTs in patients undergoing NYHA Class III antiarrhythmic drug therapy10
- DFTs may rise in the pediatric and congenital heart disease populations11
- Patients with Brugada syndrome have a high prevalence of high defibrillation energy requirement12
- Although results from the LESS study indicate that safety margins lower than 10 J may be warranted in some patients, 4% (30) of the 702 patients originally enrolled in this study were subsequently dropped from the study because of high DFTs13
Certain drugs may cause DFTs to rise, including:
- Mexilitine14
- Carvedilol15,16
- Viagra17
- Effexor18
1Russo A et al: Defibrillator implantation testing: how can patients who require system modification to obtain an adequate safety margin for defibrillation be identified? JACC 2005; Circulation Supplements (Feb 1): 104A, 1080.
2Shukla H et al: High defibrillation thresholds in transvenous biphasic implantable defibrillators: clinical predictors and prognostic implications. PACE 2003; 26 (1 Pt 1):44-48.
3Nanthakumar K et al. Systematic evaluation of the determinants of defibrillation efficacy. Heart Rhythm 2005; 2:36-41.
4Denman R et al. Does optimizing an ICD’s defibrillation waveform result in a lower defibrillation threshold (DFT)? Heart Rhythm 2004; (1, 1, May Supplement):S275-878.
5Mouchawar G et al. ICD waveform optimization: a randomized, prospective, pair-sampled multicenter study. PACE 2000; 23 (11, part II): 1992-95.
6Ellenbogen K et al. Upward DFT shift as a cause of sudden death; XIIth World Conference on Cardiac Pacing and Electrophysiology. Clinical Cardiac Pacing and Electrophysiology; ICPES 2003, 199-202.
7Wase A et al. Impact of chronic kidney disease upon survival among implantable cardioverter-defibrillator recipients. Journal of Interventional Cardiac Electrophysiology 2004; 11:199-204.
8Pelosi F, Oral H et al. Effect of chronic amiodarone therapy on defibrillation energy requirements in humans. J Cardiovasc Electrophysiol 2000; 11:736-740.
9Nielsen TD et al. Effect of acute amiodarone loading on energy requirements for biphasic ventricular defibrillation. American Journal of Cardiology 2001; 88:446-447.
10Merkely B et al. Shortening the second phase duration of biphasic shocks: effects of class III antiarrhythmic drugs on defibrillation efficacy in humans. Cardiovasc Electrophysiol 2001; 12:824-27.
11Stephenson EA et al. Utility of routine follow-up defibrillator threshold testing in congenital heart disease and pediatric populations. J Cardiovasc Electrophysiol 2005; 16:69-73.
12 Watanabe H et al. Unsuccessful internal defibrillation in Brugada syndrome: focus on refractoriness and ventricular fibrillation cycle length. J Cardiovasc Electrophysiol 2005; 16:262-266.
13Mann DE et al. The low energy safety study (LESS): rationale, design, patient characteristics, and device utilization. Am Heart J 2002; 143:199-204.
14Crystal E, Ovsyshcher IE et al. Mexiletine related chronic defibrillation threshold elevation: case report and review of the literature. PACE 2002; 25:507-8.
15Melichercik J et al. Rise of defibrillation energy requirement under carvedilol therapy. PACE 2001; 24 (9, part I): 1417.
16McBride BF et al. Does the use of beta-blocker or choice of beta-blocker impact the defibrillation threshold? Circulation 2004; 110: #2907, 111-625.
17Shinlapawittayatorn K et al. Sildenafil citrate (Viagra) markedly increases defibrillation threshold in swine. Journal of the American College of Cardiology 2005; #1107-248, 110A.
18Carnes CA et al. Elevated defibrillation threshold with venlafaxine (Effexor) therapy. Pharmacotherapy 2004; 24 (8):1095-98.