Patient Alert™ to detect ICD lead failure: efficacy, limitations, and implications for future algorithms

Diagnostic Approach to Suspected Lead Failure

Transvenous lead failure associated with cardiac pacing and defibrillation remains an important clinical problem, with an estimated incidence between 1 to 2%. Oversensing of non-physiological signals usually precede lead impedance changes and may result in clinical compliations such as pacing inhibition and inappropriate shocks. Device based algorithms that identify non-physiological signals can be used in conjunction with remote monitoring to facilitate early diagnosis and management of lead failure and avoid serious adverse outcomes. This review highlights mechanisms of lead failure and proposes a diagnostic approach to suspected lead failure.

Retrospective application of Program to Access and Review Trending iNformation and Evaluate coRrelation to Symptoms in patients with Heart Failure criteria for the remote management of patients with cardiac resynchronisation therapy

Aim The Program to Access and Review Trending iNformation and Evaluate coRrelation to Symptoms in patients with Heart Failure (PARTNERS HF) trial elaborated a multiparametric model for prediction of acute decompensation in advanced heart failure patients, based on periodical in office data download from cardiac resynchronisation devices. In this study, we evaluated the ability of the PARTNERS HF criteria to detect initial decompensation in a population of moderate heart failure patients under remote monitoring. Methods We retrospectively applied the PARTNERS HF criteria to 1860 transmissions from 104 patients (median follow up 21 months; range 1-67 months), who were enrolled in our programme of telemedicine after cardiac resynchronisation therapy. We tested the ability of a score based on these criteria to predict any acute clinical decompensation occurring in the 15 days following a transmission. Results In 441 cases, acute heart failure was diagnosed after the index transmission. The area under the curve (AUC) of the score for the diagnosis of acute decompensation was 0.752 (confidence interval (CI) 95% 0.728-0.777). The best score cut-off was consistent with the results of PARTNERS HF: with a score ≥2, sensitivity was 75% and specificity 68%. The odds ratio for events was 6.24 (CI 95% 4.90-7.95; p < 0.001). Conclusions When retrospectively applied to remote monitoring transmissions and arranged in a score, PARTNERS HF criteria could identify HF patients who subsequently developed acute decompensation. These results warrant prospective studies applying PARTNERS HF criteria to remote monitoring.

Generator and lead-related complications of implantable cardioverter defibrillators

BACKGROUND

Increase in the number of patients treated with Implantable Cardioverter Defibrillator (ICD) requests more attention regarding its complications.

OBJECTIVES

This study aimed to assess the generator- and lead-related complications at implantation and during follow-up in the patients who were treated with ICD for primary and secondary prevention reasons.

METHODS

We retrospectively reviewed 255 consecutive patients who underwent transvenous ICD implantation for the first time in a 7-year period and were followed-up for 3 years at Tehran Heart Center. The personal and clinical data of the patients as well as specific data on the ICD implantation were retrieved. The frequency of each of the complications was reported and the study variables were compared between the patients with and without complications using Student's t-test and chi-square test where appropriate. P values less than 0.05 were considered as statistically significant.

RESULTS

Out of a total of 525 implanted leads and 255 implanted devices in 255 patients (mean age = 62.57 ± 13.50 years; male = 196 [76.9%]), complications leading to generator or lead replacement occurred in 32 patients (12.5%). The results revealed no significant difference between the patients with and without complications regarding gender and age (P = 0.206 and P = 0.824, respectively). Also, no significant difference was found between the two groups concerning the ejection fraction (P = 0.271). Lead fracture was the most frequent lead-related complication and was observed in 17 patients (6.6%). Besides, it was mainly observed in the RV leads. Generator-related complications leading to generator replacement were observed in 2 patients (0.7%).

CONCLUSIONS

Despite considerable improvements in the ICD technology, the rate of the ICD complications leading to device replacement and surgical revision, especially those related to the leads, is still clinically important.

Use of remote monitoring in the management of system-related complications in implantable defibrillator patients

Remote monitoring of implantable defibrillators (ICDs) is designed to minimise regular follow-up visits and to facilitate early detection of adverse events. With the increased rate of ICD implantations in today's clinical setting and multiple device advisories, which pose management challenges, this approach becomes very attractive. The aim of this article is to present the role of remote monitoring in the detection of system-related complications, its potential benefits and its barriers in the outpatient management of ICD patients.

Contributions of remote monitoring to the follow-up of implantable cardioverter-defibrillator leads under advisory

Aims

Automatic daily transmission of data from implantable cardioverter–defibrillators (ICDs) enables the remote monitoring of device status and leads function. We report on a 2-year experience with remote monitoring in 40 recipients of high-voltage ICD leads, prone to fracture and under advisory since October 2007.

Methods and results

The ICDs were remotely monitored as well as systematically interrogated in the ambulatory department every 3 months. The patients were also seen in case of abnormal lead impedance, or other manifestations consistent with lead dysfunction. Over a mean follow-up of 22 ± 4 months after ICD implantation, four lead dysfunctions were suspected because of remotely transmitted oversensing of noise artifacts, abrupt rise in pacing impedance, or both. A lead fracture needing lead replacement was confirmed in three patients (7.5%), two of them before any inappropriate therapy and one after the delivery of three inappropriate shocks. No lead failure was observed in the remaining 36 patients, either at the time of ambulatory visits or during remote monitoring.

Conclusion

Remote monitoring allowed the early and reliable detection of ICD leads failure without requiring any patient intervention.

Monitoring capabilities of cardiac rhythm management devices

Since the advent of the first generation pacemakers, solely providing rate support, we have witnessed a technological outburst in the type and complexity of implantable devices. The introduction of implantable cardioverter defibrillators and later of cardiac resynchronization therapy devices enriched our therapeutic arsenal for the management of patients with heart failure and/or high risk of sudden cardiac death. In addition, during the last decade, newer generation cardiac rhythm management devices (CRMs) have been capable to provide a continuously expanding pool of diagnostic information derived by novel monitoring capabilities. Although at present the clinical role of this information is undervalued, it is evident that the clinical exploitation of data derived by CRMs may transform the standards of care for our patients by providing timely applied individualized diagnosis and treatment. In this context, even in the absence of solid data supporting the use of this information in everyday clinical practice, improving our familiarity with currently available monitoring algorithms is a prerequisite for the electrophysiologist who keeps in pace with the rapidly evolving technologies of CRMs and is prepared for their future role on clinical practice.

Causes of ventricular oversensing in implantable cardioverter-defibrillators: implications for diagnosis of lead fracture

BACKGROUND

Implantable cardioverter-defibrillator (ICD) ventricular oversensing may result in inappropriate therapy, which may be triggered by lead/connection issues that require surgical revision or physiologic oversensing that may be resolved with reprogramming. The sensing integrity counter (SIC) is an oversensing diagnostic that increments for very rapid ventricular intervals < or =130 ms.

OBJECTIVE

The purpose of this study was to determine the causes of a high SIC and the ability of additional diagnostics to differentiate lead/connection issues from other causes of oversensing for patients with normal impedance.

METHODS

Frequent SICs were identified in patients during routine follow-up visits. To diagnose the cause of oversensing, patients wore a modified 24-hour digital Holter monitor that recorded ECG, ventricular electrogram, and the ICD Marker Channel (Medtronic). Recordings were reviewed to determine the causes of oversensing. Patients with confirmed oversensing and adequate data were analyzed. The number of SICs per day and the presence of a nonsustained tachycardia (NST) episode with ventricular mean cycle length <220 ms were retrieved from stored ICD data.

RESULTS

Forty-eight patients had a median of 13 SICs/day. Presumed lead/connection issues occurred in 23% of patients, whereas physiologic oversensing occurred in 77% of patients. A rapid NST was recorded more commonly in patients with lead/connection issues than in those without (9/11 vs 1/37; P < .0001).

CONCLUSION

Oversensing resulting in frequent, very short intervals typically are caused by either lead/connection issues or physiologic signals. The additional finding of rapid NSTs usually indicates a lead/connection issue, even in the absence of impedance abnormalities.

Remote monitoring and follow-up of pacemakers and implantable cardioverter defibrillators

In the era of communication technology, new options are now available for following-up patients implanted with pacemakers (PMs) and defibrillators (ICDs). Most major companies offer devices with wireless capabilities that communicate automatically with home transmitters, which then relay data to the physician, thereby allowing remote patient follow-up and monitoring. These systems are being widely used in the USA for remote follow-up, and have been more recently introduced in Europe, where their adoption is increasing. In this article, we describe the currently existing systems, review the available evidence in the literature regarding remote follow-up and monitoring of PMs and ICDs, and finally discuss some unresolved issues.

Downloadable Algorithm to Reduce Inappropriate Shocks Caused by Fractures of Implantable Cardioverter-Defibrillator Leads

Background— The primary method for monitoring implantable cardioverter-defibrillator lead integrity is periodic measurement of impedance. Sprint Fidelis leads are prone to pace-sense lead fractures, which commonly present as inappropriate shocks caused by oversensing.

Methods and Results— We developed and tested an algorithm to enhance early identification of lead fractures and to reduce inappropriate shocks. This lead-integrity algorithm, which can be downloaded into presently implanted implantable cardioverter-defibrillators, alerts the patient and/or physician when triggered by either oversensing or excessive increases in impedance. To reduce inappropriate shocks, the lead-integrity algorithm increases the number of intervals to detect (NID) ventricular fibrillation when triggered. The lead-integrity algorithm was tested on data from 15 970 patients with Fidelis leads (including 121 with clinically diagnosed fractures) and 95 other fractured leads confirmed by analysis of returned product. The effect of the NID on inappropriate shocks was tested in 92 patients with 927 shocks caused by lead fracture. Increasing the NID reduced inappropriate shocks ( P <0.0001). The lead-integrity algorithm provided at least a 3-day warning of inappropriate shocks in 76% (95% CI, 66 to 84) of patients versus 55% (95% CI, 43 to 64) for optimal impedance monitoring ( P =0.007). Its positive predictive value was 72% for lead fractures and 81% for lead fractures or header-connector problems requiring surgical intervention. The false-positive rate was 1 per 372 patient-years of monitoring.

Conclusions— A lead-integrity algorithm developed for download into existing implantable cardioverter-defibrillators increases short-term warning of inappropriate shocks in patients with lead fractures and reduces the likelihood of inappropriate shocks. It is the first downloadable RAMware to enhance the performance of nominally functioning implantable cardioverter-defibrillators and the first implantable cardioverter-defibrillator monitoring feature that triggers real-time changes in ventricular fibrillation detection parameters to reduce inappropriate shocks.

Remote monitoring in implantable defibrillator therapy

The major device manufacturers have introduced systems for remote patient monitoring. These remote monitoring systems promise more efficient patient management, especially in today's clinical setting with the growing number of defibrillator implantations. The aim of this article is to present the role of remote patient monitoring in implantable cardioverter-defibrillator follow-up, its potential benefits and its barriers to widespread diffusion. (Neth Heart J 2008;16:53-6.).

Sensing failure associated with the Medtronic Sprint Fidelis defibrillator lead

INTRODUCTION

The diameter of implantable cardioverter-defibrillator (ICD) leads has become progressively smaller over time. However, the long-term performance characteristics of these smaller ICD leads are unknown.

METHODS

We retrospectively evaluated 357 patients who underwent implantation of a Medtronic Sprint Fidelis defibrillating lead at two separate centers between September 2004 and October 2006. Lead characteristics were measured at implant, at early follow-up (1-4 days post implant), and every 3-6 months thereafter.

RESULTS

During the study period, 357 patients underwent implantation of the Medtronic Sprint Fidelis lead. The mean R-wave measured at implant through the device was not different (P = NS) when compared with that measured at first follow-up (10.5 +/- 5.0 mV vs 10.7 +/- 5.1 mV). Forty-one patients (13%) had an R-wave amplitude <or= 5 mV measured through the device at implant. Of those patients with an R-wave amplitude <or= 5 mV at implant measured through the device, 63% (n = 26) remained <or= 5 mV for the duration of follow-up. The mean time to R-wave amplitude <or= 5 mV was 96.2 +/- 123 days. During follow-up, 65 (18%) patients developed R-wave <or= 5 mV. Overall 10 lead revisions (2.8%) were performed during the first year of follow-up.

CONCLUSION

Abnormal R-wave sensing is frequently observed during follow-up with the Medtronic Fidelis ICD lead. Lead revision was necessary in 2.8% of the patients, most often (8 of 10) due to abnormal R-wave sensing along with elevated pacing threshold. Whether this issue is limited to this lead or reflects a potential problem with all downsized ICD leads merits further investigation.

Unusual cause for an increase of the sensing integrity counter in a patient with inappropriate implantable cardioverter-defibrillator therapy

We describe the case of a patient who presented with multiple implantable cardioverter-defibrillator (ICD) shock discharges 12 months after device implantation. Upon device interrogation, intermittent oversensing of electrical noise and potential ICD lead failure were suggested by a significant increase in the sensing integrity counter (SIC), a cumulative count of very short ventricular sensed intervals. Analysis of stored episodes, however, revealed that inappropriate ICD therapy had been caused by intermittent T-wave oversensing (TWO), and that the increase of the SIC resulted from the coincidence of TWO and premature ventricular complexes (PVCs). T-wave oversensing resolved and the SIC did not increase any more during follow-up after adjustment of ventricular sensitivity. The coincidence of TWO and PVCs should therefore be considered as an uncommon cause for short ventricular sensed intervals in ICD patients presenting with a suspect increase in the SIC.