Inappropriate Shocks In Patients Research Articles

Inappropriate subcutaneous implantable cardioverter-defibrillator shocks due to T-wave oversensing can be prevented: Implications for management

Inappropriate shocks (IASs) complicate implantable cardioverter-defibrillator (ICD) therapy. The management of IASs in patients with a subcutaneous ICD (S-ICD) differs from that in patients with a conventional ICD because of different sensing algorithms and programming options. To describe the management of IASs in patients with an S-ICD. Patients were implanted with an S-ICD between February 2009 and July 2012. The prevalence data and clinical determinants of IASs were prospectively collected. In the case of T-wave oversensing (TWOS), an exercise test was performed, and all possible sensing vectors were screened for TWOS. The absence of TWOS defined a suitable vector. Eleven of 69 patients (54% men; mean age 39 ± 14 years; 73% primary prevention) received IASs after 8.9 ± 10 months of implantation (10.8% annual incidence rate). In 8 cases, TWOS caused IASs. Seven of these IASs occurred during exercise and 1 during atrial fibrillation with a high ventricular rate. To manage TWOS, in 7 of 8 patients the sensing vector was changed and in 5 of 8 patients the (un)conditional zone was changed. Hereafter, IASs recurred in 3 of 8 patients, in 2 because of programming errors. Hence, after reprogramming, we observed no IASs in 87.5% of the patients with TWOS during a follow-up of 14.1 ± 13 months. IASs due to TWOS in the S-ICD can be managed by reprogramming the sensing vector and/or the therapy zones of the device using a template acquired during exercise. Exercise-optimized programming can reduce future IASs, and standard exercise testing shortly after the implantation of an S-ICD may be considered in patients at an increased risk for TWOS.

Incidence of atrial tachyarrhythmias in patients with early repolarization syndrome and Brugada syndrome: analysis of patients with implantable cardioverter defibrillators

Purpose: The electrocardiographic early repolarization syndrome (ERS) is associated with a risk of sudden cardiac death (SCD). It has not been known whether the arrhythmogenic substrate in patients with ERS is restricted to the ventricular level. The aim of this retrospective study was to evaluate the incidence of inappropriate shocks (IS) due to atrial tachyarrhythmias (ATAs) in patients with ERS as compared with Brugada syndrome (BrS). Methods: We analyzed data from 47 consecutive patients diagnosed with ERS and BrS who underwent implantable cardioverter defibrillator (ICD) implantation from May 1998 to December 2011. Three in patients with BrS had paroxysmal atrial fibrillation (AF). The clinical data were collected and analyzed for all events with shocks. Results: Seventeen patients with ERS (age 38.6±11.1, male=14) and 30 patients with BrS (43.6±11.3, male = 29) were enrolled. Twelve patients experienced AF after defibrillation for ventricular arrhythmia (6 in ERS vs. 6 in BrS, P = NS). During a mean follow-up of 5.3±4.5 years in the ERS and 4.4±4.0 years in the BrS, five patients received appropriate shock (3 in ERS vs. 2 in BrS, P = 0.25). There was no significant difference in the prevalence of ATAs in patients who diagnosed ERS compared with patients in BrS from pre- to post- ICD implantation (9 in ERS vs. 12 in BrS, P = 0.54). Three of 17 (17.6%) ERS and 6 of 30 (20.0%) BrS patients received IS due to ATAs during this periods (Figure, P = 0.72). ![Figure][1] Figure 1 Conclusions: ATA occurred not infrequently in patients with ERS and ICD implantation. There were no differences in the occurrence of ATA and IS in patients with ERS as compared to patients with BrS. [1]: pending:yes

Inappropriate Shocks in Patients with ICDs: Single Chamber versus Dual Chamber

BackgroundDespite the technological evolution of the implantable defibrillator, one of the questions that remains is the possible benefit of the dual chamber versus single chamber implantable cardioverter defibrillator (ICD) in reducing inappropriate shocks.ObjectiveTo evaluate which type of device provides fewer inappropriate shocks (dual chamber versus single chamber) in patients with implantable cardioverter defibrillators (ICDs).MethodsMeta-analysis of randomized studies published in the literature comparing dual-chamber implantable cardioverter defibrillators to single chamber devices which have been known to cause, as an evaluated endpoint, inappropriate shocks. ResultsThe dual-chamber implantable cardioverter showed no benefit in reducing the number of inappropriate shocks. In fact, the opposite was shown. In the analysis of fixed effects, the association tended to favor single-chamber implantable cardioverter defibrillators (OR = 1.53, CI 95%: 0.91-2.57), despite the absence of statistical significance (p = 0.11). We highlight the heterogeneity observed in the results (I2 = 53%), which motivated a replication of the analysis using a model of random effects. However, significant differences remained in the occurrence of inappropriate shocks in both groups (OR = 1.1, 95% CI: 0.37-3.31; p = 0.86). To complement the analysis, we proceeded to perform sensitivity analysis, which showed that the exclusion of a study resulted in the lowest heterogeneity observed (I2=24%) and the association with inappropriate shocks significantly favored the single chamber cardiodefibrillator (OR = 1.91; 95% CI: 1.09-3.37; p = 0.27).ConclusionsIt was determined that there was no clear evidence of superiority of any of the devices evaluated.

PHS20 Cost Associated to the Management of Inappropriate Shocks in Patients With an Implantable Cardioverter Defibrillator – Cardina Study

Inappropriate shocks are the most common complications of ICD, causing a negative effect on patients' morbidity and mortality. Little is known with regards to the cost associated to the management of IS. The aim of the study was to determine IS related factors and to evaluate its associated hospital cost. All patients implanted with an ICD where retrospectively analyzed through clinical chart reviews in a Spanish hospital from 2003 to 2011. Demographic variables, baseline cardiomyopathy, comorbidities, indication and type of ICD implanted were registered. During the follow up period we identified the presence of IS, its reasons and associated costs. A total of 227 patients were implanted with an ICD, mean age 63.2 years (26-82). Eighty-six percent were men, 64.6% with ischemic cardiomyopathy, 78.4% with heart failure, 70.4% with EF<35% and 13.1% with AF. The proportion of single, dual and three chambers ICD was 54.6%, 20.3% and 25.1% respectively. After a median follow up of 4.46 years, 27 patients had had 42 IS episodes. Average time since implant to first IS was 1.3 years (range 0.02 to 3.84 years). Patients suffering from IS had higher mortality (33.3% vs 13.7%; p<0.05). Amost 67% of the episodes were due to supraventricular tachycardia, 12% to noise detection, 19% to Wave T overdetection and 2.3% due to other causes. Sixty-three percentages of the episodes generated an emergency visit and a 39% generated a non-scheduled visit to the cardiologist. Seven episodes (16.7%) required hospitalization, six of whom required a surgical intervention. Average length of stay was 5.1 days. Finally, overall mean hospital cost appeared to be €5,175 per episode. The cost of inappropriate shocks is driven by the reason of its cause. The great majorities of the episodes were due to supraventricular arrhythmias and finally resolved without the need for hospitalization.

A fully automatic, implantable cardioverter-defibrillator algorithm to prevent inappropriate detection of ventricular tachycardia or fibrillation due to T-wave oversensing in spontaneous rhythm

T-wave oversensing (TWOS) may cause inappropriate shocks in patients with implantable cardioverter-defibrillator (ICD). Programming options to prevent TWOS are usually implemented only after TWOS has occurred, and they may compromise sensing of ventricular fibrillation (VF). To evaluate an ICD algorithm that differentiates TWOS from ventricular tachycardia (VT) or VF to prevent inappropriate detection of VT/VF when TWOS occurs. We developed a TWOS algorithm based on both the differential frequency content of R vs T waves and their alternating pattern. Algorithm parameters were developed from a database of stored electrograms. The algorithm was validated on a hardware system consisting of actual ICD circuitry by using an independent database of stored electrograms including inappropriate detections of both VT/VF caused by spontaneous TWOS and induced true VF to assess delays in detection. We tested 83 inappropriate detections of VF due to TWOS from 22 patients. All 22 patients had at least 1 successful rejection of TWOS, and rejection was effective in 80 of the 83 episodes. After adjustment for multiple episodes per patient, specificity was 96.6% (95% confidence interval 90.3%-98.8%). In 166 episodes of true VF in 92 patients, the sensitivity for VF detection was 100% (95% confidence interval 98.2%-100%) at a nominal sensitivity of 0.3 mV; the new TWOS algorithm did not delay the detection of VF. A novel TWOS rejection algorithm is designed to operate in real time. The algorithm reduced inappropriate detections of VF in spontaneous TWOS episodes by 96.6% while maintaining 100% sensitivity for detecting true VF.

Inappropriate Shocks in Patients With Fidelis® Lead Fractures: Impact of Remote Monitoring and the Lead Integrity Algorithm

The role of remote monitoring combined with lead integrity algorithm (LIA) in patients with Fidelis (Medtronic Inc., Minneapolis, MN, USA) lead fractures is not well defined. We retrospectively identified patients with Fidelis lead fractures at our institution, documenting all pertinent data (remote monitoring use, clinical presentation, lead fracture diagnosis criteria). Patients were classified into subgroups based on the type of home monitoring and whether LIA was uploaded before lead fracture. Subgroups were compared based on delivery of inappropriate shocks (IS). A total of 131 patients (mean age 62 ± 16 years, 70% male, 69% primary prevention implants) were followed until lead fracture (average 32 ± 12 months). IS were delivered in 21% of patients (n = 11/52) with LIA versus 52% (n = 41/79) without LIA, P < 0.001. LIA significantly decreased the number of IS (2.1 ± 1.0 IS vs 7.9 ± 12 IS, P < 0.001) and significantly increased the number of patients diagnosed through audible alert (P < 0.001). Wireless monitoring significantly decreased the time interval to reprogram defibrillators OFF (mean 1.5 ± 1 days vs 15.6 ± 18 days with nonwireless CareLink [Medtronic Inc.] and 12.4 ± 20 days without CareLink, P < 0.001); 14% of patients with LIA and wireless monitoring combined received IS. Without LIA, 63% of patients with wireless monitoring received IS. This study confirms that LIA significantly decreases IS therapy in patients with Fidelis lead fractures. Wireless technology enhances LIA benefits by significantly shortening time to reprogram defibrillators. However, despite the "best scenario" of combining LIA and wireless monitoring, 14% of patients with lead fractures still get IS. Further refinements of detection algorithms are required to eliminate this significant clinical problem.

A Higher than Expected Prevalence of AV Nodal Reentrant Tachycardia in Patients Receiving Implantable Cardioverter‐Defibrillators

Epidemiologic studies have indicated that the prevalence of paroxysmal supraventricular tachycardia (SVT) is approximately two to three of 1000 persons, of whom 50-60% have atrioventricular node reentrant tachycardia (AVNRT). Although SVT has been reported to account for a significant portion of inappropriate shocks in patients receiving implantable cardioverter-defibrillators (ICDs), the incidence of AVNRT is unknown. To define the incidence of AVNRT in patients with ICDs. Of 426 patients followed with an ICD, 15 patients with AVNRT were identified (3.5%). AVNRT was noted preimplant in eight patients. One had remote AVNRT and had undergone radiofrequency (RF) ablation several years prior to ICD implantation. Three patients had known episodes and underwent RF ablation prior to ICD implant. Four had AVNRT induced at preimplant electrophysiology study and three had RF ablation prior to ICD implant. Seven patients had clinical episodes of AVNRT after ICD implant and six of seven received inappropriate ICD therapy for AVNRT. All seven patients underwent RF ablation for treatment of AVNRT. No patient who underwent RF ablation had further clinical episodes of SVT, and only one had further inappropriate ICD therapy for sinus tachycardia. The substantially higher prevalence of AVNRT in our followed ICD population (3.5%) compared to the general population may be due to detection bias or electroanatomic changes in the atrioventricular nodal area induced by the accompanying heart disease. In any case, further studies to evaluate the inducibility of AVNRT prior to ICD implant, its prognostic implications, and the role of RF ablation to prevent inappropriate shocks are warranted.

Efficacy of Remote Monitoring Systems for Reducing Inappropriate Shocks in Patients with ICD

Introduction: Inappropriate shocks (IAS) were associated with increased risk of mortality and deterioration of QOL in pts with ICD. To investigate the efficacy of remote monitoring systems (RM) for reducing IAS.Methods: We retrospectively reviewed consecutive 202 pts who had been implanted ICDs from 2005. Incidence of IAS and device-related problems were reviewed in 101 pts under RM (CareLink (n=95)/HomeMonitoring (n=6)) during ≤2 yrs and in 101 control-pts (C) who underwent conventional scheduled-checks during ≤2 yrs after ICD implantation.Results: Age, gender, AF, single-chamber ICD, Fidelis-lead, VF detection rate, treatment with amiodarone and β blockers were not significantly different between RM and C groups, except for idiopathic VF (26 vs. 18%; p<.05) and LVEF (48 vs. 42%; p<.05). Kaplan-Meier survival curve revealed significant reduction of IAS under RM compared to C group (p=0.032). A total of 10/15 device-related problems were detected in C/RM groups. Device problems were more often confirmed just after IAS in C than RM group (80 vs. 27%; p<.01). In RM group, 73% of problems had been managed 2±2 days after data detection and did not cause IAS. Multiple regression analysis showed that RM (OR; 0.29, 95%CI; 0.11–0.78, p<.05) and age (OR; 0.97, 95%CI; 0.94–0.996, p<.05) were independently associated with IAS.Conclusions: Incidence of IAS may be reduced under RM which enables us to detect device-related problems before the delivery of IAS from ICD.

Aktueller Stellenwert von Amiodaron in der antiarrhythmischen Therapie

Decades after its registration, amiodarone is still regarded as the most effective antiarrhythmic drug available for the treatment of tachyarrhythmias. Amiodarone is classified as a class III antiarrhythmic drug. In addition to the prolongation of cardiac repolarization, its leading pharmacologic features are sodium and calcium channel block, nonselective β-adrenergic inhibition as well as high lipophilicity and a very long plasma half-life. In patients with paroxysmal atrial fibrillation, amiodarone is the most effective antiarrhythmic drug in maintaining sinus rhythm. Furthermore, it prevents ventricular arrhythmias, such as frequent ventricular extrasystoles or nonsustained runs of ventricular tachycardia, as well as sustained ventricular tachycardia and ventricular fibrillation. In patients with increased risk for sudden cardiac death, e.g., with severely depressed left ventricular function, amiodarone is a highly effective and safe antiarrhythmic drug. In addition, amiodarone has been shown to reduce the number of appropriate and inappropriate shocks in patients with an implantable cardioverter-defibrillator. During long-term amiodarone treatment, typical side effects including corneal microdeposits, blue-gray skin discoloration, photosensitivity, hypothyroidism, hyperthyroidism, peripheral neuropathy, optical neuritis and hepatotoxicity accrue. Upon cessation of medication, these are almost always reversible. Irreversible, severe adverse effects, such as pulmonary toxicity, are very rare under the currently used maintenance dose of 200 mg/day. With regard to its side effect profile, an adequate follow-up of patients including laboratory values, lung function tests, and visual acuity is necessary.

Lead integrity alert algorithm decreases inappropriate shocks in patients who have Sprint Fidelis pace-sense conductor fractures

The Medtronic Sprint Fidelis high-voltage implantable cardioverter-defibrillator (ICD) lead is prone to fracture. The majority of fractures involve the pace-sense (P/S) conductors and may result in multiple inappropriate shocks. The Medtronic lead integrity alert (LIA) algorithm was designed to improve early detection of transient P/S conductor fractures and to decrease the incidence and number of inappropriate shocks. The purpose of this prospective single-center study was to assess the effectiveness of the LIA algorithm for warning patients of an impending Sprint Fidelis P/S conductor fracture and for decreasing the incidence and number of inappropriate shocks. The study population included all patients who had Sprint Fidelis leads and Medtronic ICD pulse generators that were implanted and followed at the Minneapolis Heart Institute. Patients were evaluated in the clinic every 3 to 4 months or by remote monitoring using the Medtronic CareLink system. When the LIA algorithm was released in August 2008, the RAMware was downloaded to the pulse generator of all patients with the Sprint Fidelis lead. Patients and family members received educational materials and were given a demonstration of the audible alerts. Between October 2004 and January 2010, 52 (11.3%) of 461 Sprint Fidelis leads failed in the study population. Inappropriate shocks were the first sign of lead failure in 18 (69%) of the 26 patients who did not have the LIA compared to 4 (17%) of 23 patients who had the LIA (P = .0004). Patients who experienced inappropriate shocks without the LIA received an average of 13.2 +/- 13.6 inappropriate shocks (range 2-54) versus 3.0 +/- 2.0 inappropriate shocks (range 2-6) in patients who had the LIA (P = .017). The audible alert was effective in 70% (16/23) and 35% (6/17) of patients with and without the LIA, respectively, whose alerts were programmed ON (P = .053). Overall, 8 (32%) of 25 patients whose audible alerts were triggered did not immediately hear or recognize the tone. The LIA appears to be an effective method for detecting most Sprint Fidelis lead fractures and for decreasing the incidence and number of inappropriate shocks. However, a better method for alerting patients and caregivers is needed.

Strategy to Eliminate Inappropriate Shocks Secondary to T‐Wave Oversensing in a Biventricular ICD

T-wave oversensing represents a common cause of inappropriate shocks in patients with implanted cardiac defibrillators. This case report demonstrates a strategy of device programming using V-V pace delay (sequential rather than simultaneous biventricular pacing) to eliminate T-wave oversensing without decreasing sensitivity to detect true tachyarrhythmia.

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

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. 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. 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.

Effects of Antiarrhythmic Drugs on Inappropriate Shocks in Patients With Implantable Cardioverter Defibrillators

Patients with atrial fibrillation (AF) or congestive heart failure (CHF) are more vulnerable to inappropriate shocks from implantable cardioverter-defibrillators (ICDs), but the effect of antiarrhythmic drugs in these patients remains unknown. A total of 55 patients with AF and/or CHF (New York Heart Association functional class > or =III) who had ICDs were divided into 3 groups [amiodarone (n=24), sotalol (n=12), beta-blocker (n=19)] and the cumulative rates of inappropriate shocks were compared. The baseline characteristics of the 3 groups were not significantly different. The 4-year event rate of inappropriate shocks was 27.3% in the amiodarone group, 54.3% in the sotalol group, and 70.6% in the beta-blocker group (amiodarone vs beta-blocker: log-rank p=0.003; sotalol vs beta-blocker: log-rank p=0.16; amiodarone vs sotalol: log-rank p=0.29). Amiodarone reduced the risk of inappropriate shocks significantly as compared with beta-blockers (hazard ratio (HR) 0.17; 95% confidence interval (CI) 0.05-0.64; p=0.008), whereas sotalol did not (HR 0.57; 95%CI 0.19-1.68; p=0.3). Amiodarone was discontinued in 4 patients (16.7%) because of pulmonary toxicity and the dose was reduced in 4 patients (16.7%) because of a thyroid function abnormality. Amiodarone is more effective than sotalol or beta-blockers in preventing inappropriate ICD shocks in patients with AF or CHF, but it has a significant risk of drug-related adverse effects.