|Year : 2017 | Volume
| Issue : 1 | Page : 49-51
Clinical implications of real time implantable cardioverter-defibrillator high voltage lead short circuit detection
Roy Chung1, Patricia D Garrett1, Brian Wisnoskey2, Mandeep Bhargava1, Bruce L Wilkoff1
1 Department of Cardiovascular Medicine, Section of Cardiac Electrophysiology and Pacing, Cleveland Clinic, Cleveland, Ohio, USA
2 Regional Arrhythmia Specialist, St. Jude Medical, Austin, Texas, USA
|Date of Web Publication||19-Jun-2017|
Bruce L Wilkoff
9500 Euclid Avenue, Cleveland, Ohio 44195
Source of Support: None, Conflict of Interest: None
Implantable cardioverter-defibrillator lead failures are uncommon and predicting impending failure is challenging. We described a clinical case of a successful defibrillation despite initial detection of low high voltage impedance using Dynamic Tx algorithm, by withholding therapy if there is a short circuit and changing its shocking vector to an alternate one.
Keywords: Dynamic Tx, implantable defibrillator lead failure, ventricular fibrillation
|How to cite this article:|
Chung R, Garrett PD, Wisnoskey B, Bhargava M, Wilkoff BL. Clinical implications of real time implantable cardioverter-defibrillator high voltage lead short circuit detection. Int J Heart Rhythm 2017;2:49-51
|How to cite this URL:|
Chung R, Garrett PD, Wisnoskey B, Bhargava M, Wilkoff BL. Clinical implications of real time implantable cardioverter-defibrillator high voltage lead short circuit detection. Int J Heart Rhythm [serial online] 2017 [cited 2019 Oct 16];2:49-51. Available from: http://www.ijhronline.org/text.asp?2017/2/1/49/208454
| Introduction|| |
Premature insulation failure among the defibrillation leads may be associated with electrical failure. Nonetheless, replacing recalled leads with potential lead failure by extraction is not practical due to its inherent risk. Anew algorithm has been developed to detect real time lead short circuit.
| Case Report|| |
An 80-year-old man with complex cardiac history including ischemic cardiomyopathy (ejection fraction [13±5] %) and chronic atrial fibrillation (AF) had a single chamber implantable cardioverter-defibrillator (ICD) placed 13 years previously for primary prevention. The patient had received ICD therapies for both ventricular tachycardia and AF with rapid ventricular rates. He subsequently underwent atrioventricular nodal ablation and his device was upgraded to a cardiac resynchronization therapy defibrillator (CRT-D) 10 months before presenting to our center. Hardware included a Quadra Assura™ CRT-D model 3365-40C (St. Jude Medical, Sylmar, CA, USA), an SPL SP02 dual-coil right ventricular (RV) ICD lead (Ventritex, Sunnyvale, CA, USA), and Quartet™ quadripolar left ventricular pacing lead model 1458Q (St. Jude Medical, Sylmar, CA, USA).
The patient noted the ICD's vibratory alert which also triggered a Merlin.net™ PCN remote transmission documenting a high-voltage (HV) lead issue. Further review demonstrated 7 episodes in the ventricular fibrillation (VF) zone. The first episode with electrogram confirming VF and successful 36 J shock delivered for conversion. HV lead impedance (HVLI) with this episode was 51 Ω. For the second VF episode, the shock was aborted as the shock impedance was <10 Ω from RV to superior vena cava (SVC) and Can indicating potential HV lead issue. The device then initiated the DynamicTx™ algorithm by withholding therapy and modifying the shocking configuration to the RV to Can configuration (impedance of 72 Ω) with successful shock delivered for conversion after short redetection time [Figure 1]. There were 6 additional VF episodes requiring ICD therapies. In each event, the device identified the compromised shocking vector, switched defibrillation configurations, and successfully converted the rhythm with 40 J shocks [Figure 2].
|Figure 1: Intracardiac electrogram showing detection of ventricular fibrillation, attempt at high-voltage therapy, and detection of an overcurrent resulting in the withholding of therapy (0 J). Following a short (6 interval) redetection period, the shocking configuration is modified from the right ventricular to Can and successful delivery of a maximum output (40.0 J) shock occurs. HV = High voltage, VF = Ventricular fibrillation.|
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|Figure 2: Episode summary detailing successful termination of a ventricular fibrillation episode by a 36 J shock (4:15 AM). Subsequent episodes show the detection of overcurrent situation in the programmed RC to superior vena cava and Can configuration, alteration in the shock vector to right ventricular to Can, and successful delivery of shock therapy 6 additional times over the next 20 h. VF = Ventricular fibrillation, VT = Ventricular tachycardia.|
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The algorithm-triggered remote interrogation results were confirmed in person and the ICD was reprogrammed to remove the SVC coil (RV to Can configuration) with successful defibrillation threshold testing performed in the electrophysiology laboratory.
The DynamicTx™ algorithm received Food and Drug Administration approval in June 2013 and has been available in the latest models of St. Jude Medical ICD and CRT-D. This algorithm measures the current through the HV defibrillation circuit at the immediate onset of shock delivery to verify lead integrity before therapy (844 V in this case). Intended for dual coil defibrillation leads, the algorithm attempts the first shock in the programmed configuration, nominally RV coil to SVC coil and Can. In the case of below normal HVLI during shock delivery, an “overcurrent” (>60 amperes) is detected. The device withholds therapy and reconfigures the HV shocking configuration to RV coil to Can. After a 6 interval tachycardia redetection, the device completes its charging and attempts again to deliver therapy in the first alternative RV coil to Can configuration at full output. If this alternate configuration displays an overcurrent a second alternate configuration, RV coil to SVC coil configuration is utilized. During an episode, 6 attempts at therapy delivery will be made before ending an episode. Working shocking vector configuration is not programmed the end of a therapy as noted in this patient's case. Activation of the DynamicTx™ results in three programmable alerts: (1) a vibratory patient notifier; (2) a programmer alert displayed upon interrogation; and (3) a remote monitoring alert. These alerts indicate the presence of a possible HV lead issue that an alternative shock configuration has been attempted and the HVLI is out of range.
| Discussion|| |
It is well understood that the lead comprises the most vulnerable portion of the cardiac implantable electronic device system and that ICD leads have a finite life span with various contributing factors. In addition, mechanisms of lead failure vary among different defibrillation lead families. The Medtronic Sprint Fidelis is associated with fracture in the sense-pace conductor or cables resulting in oversensing, inappropriate shocks, and/or loss of pacing; whereas in the St. Jude Medical Riata family, the initial manifestation is most commonly conductor externalization. Development of the Medtronic Lead Integrity Alert™, designed in response to Sprint Fidelis recall, has been shown to be effective in reducing inappropriate shocks and detecting lead failure. The DynamicTx algorithm was designed to address the limitations inherent in using lead noise and/or secondary electrical parameters in an attempt to predict lead failure during HV therapy delivery. This algorithm was developed after the St. Jude Medical recall on 80,000 Riata and Riata ST leads in the USA in December 2011. Externalization of the HV cable conductors to the SVC and RV coils creates the potential for a short anywhere the opposite polarity components are in close contact resulting in a high current drain and potential electrical failure of the circuitry. Externalization rates are as high as 24.2% for the 8 Fr 1580 series and 9.3% for the 7 Fr 7000 series. Rates of electrical failure are higher in the 8 Fr as compared to the 7 Fr Riata leads (5.2% vs. 3.3%) over a 5 years median follow-up. Confounding these findings is that Riata conductor externalization is poorly correlated with electrical failure. Of note, a recent meta-analysis comprised 23 independent studies and >12,000 Riata leads found that the rate of electrical failure in the presence of conductor externalization was 17.3% while in its absence was 2.7%. Failure of these leads has been reported during HV delivery without warning predominantly from shorts in the subcutaneous pocket between the RV cable and the Can electrode but also under the SVC coil shorting to the RV cable. Surveillance monitoring of these leads through testing in person or remotely often does not show abnormalities. In our case, lead failure was noted 15 min after successful HV shock delivery. Importantly, this lead is not a Riata lead, yet failed between the SVC coil and RV cable, and was successfully detected and treated. This algorithm is unique in that it provides a mechanism to deliver alternative defibrillation therapy without compromising device function due to conductor short circuit and overcurrent situations in the event of a lead failure.
Mizobuchi et al. reported a case using where this algorithm detected a Riata lead issue and successfully altered the shocking configuration during defibrillation testing at device change. Our case presents several unique features. It represents the first documented application of DynamicTx resulting in patient rescue in an out of hospital cardiac arrest. In addition, it highlights the capability of the device to apply the algorithm successfully in the event of multiple VF episodes. This case also provides documentation that, while is a potential management tool for the Riata lead family, it works on non-Riata ICD leads as well.
| Conclusion|| |
Managing leads under advisory remains a complex and confusing task. Typically, clinicians rely upon indirect parameters such as impedance, sensing, and capture trends; however, these are not always indicative of a catastrophic lead failure. The greatest clinical concern is failure of the lead during defibrillation therapy. This algorithm provides a unique solution to the challenge of managing lead failure that occurs during the attempt to deliver HV therapy.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]