Does change in device detected frequency of non-sustained or diverted episodes serve as a marker for inappropriate shock therapy? Analyses from the INTRINSIC RV and ALTITUDE-REDUCES Trials.

AIMS: Implantable cardioverter-defibrillators (ICDs) treat ventricular tachycardia or fibrillation but may also deliver unnecessary shocks. We sought to determine if the frequency of ICD-detected non-sustained or diverted (NSD) episodes increases before appropriate or inappropriate ICD shocks. METHODS AND RESULTS: We evaluated NSD episodes in the INTRINSIC RV Trial and their relationship to ICD shocks (appropriate and inappropriate). Time from NSD to shock was analysed. Results were validated by utilizing 1495 adjudicated ICD and cardiac resynchronization therapy-defibrillator shocks following NSD episodes collected through the LATITUDE remote monitoring system as part of the ALTITUDE-REDUCES Study. In INTRINSIC RV, 185 participants received 373 shocks; 148 had at least 1 NSD episode. Non-sustained or diverted frequency increased 24 h before the first shock for those receiving an inappropriate (P < 0.01) but not an appropriate shock (P = 0.17). Patients with NSD episodes within 24 h of a shock were significantly more likely to receive inappropriate therapy [odds ratio (OR) = 3.12, P < 0.01]. At the receiver operator curve determined optimal cutoff, an NSD episode within 14 min before shock strongly predicted inappropriate therapy (sensitivity 48%, specificity 91%; OR = 8.8, and P < 0.001). The 14 min cut-off evaluated on an independent dataset of 1495 shock episodes preceded by an NSD in the ALTITUDE-REDUCES Study confirmed these results (sensitivity = 47%, specificity = 85%, OR = 5.0, and P < 0.001). CONCLUSION: Device-detected NSD episodes increase before inappropriate but not appropriate shocks. Novel alerts or automated algorithms based on NSD episodes may reduce inappropriate shocks.

Noise, artifact, and oversensing related inappropriate ICD shock evaluation: ALTITUDE noise study.

BACKGROUND: Approximately 12-21% of implantable cardioverter defibrillator (ICD) patients receive inappropriate shocks. We sought to determine the incidence and causes of noise/artifact and oversensing (NAO) resulting in ICD shocks. METHODS: A random sample of 2,000 patients who received ICD and cardiac resynchronization therapy defibrillator shocks and were followed by a remote monitoring system was included. Seven electrophysiologists analyzed stored electrograms from the 5,279 shock episodes. Episodes were adjudicated as appropriate or inappropriate shocks. RESULTS: Of the 5,248 shock episodes with complete adjudication, 1,570 (30%) were judged to be inappropriate shocks. Of these 1,570, 134 (8.5%) were a result of NAO. The 134 NAO episodes were determined to be due to external noise in 76 (57%), lead connector-related in 37 (28%), muscle noise in 11 (8%), oversensing of atrium in seven (5%), T-wave oversensing in two (2%), and other noise in one (1%). The ICD shock itself resulted in a marked decrease in the level of noise in 60 of 134 (45%) NAO episodes, and the magnitude of this effect varied with the type of NAO (58% for external noise, 35% for muscle, 27% for lead/connector, and 0% for oversensing; P = 0.03). There was no significant difference in NAO likelihood based on type of lead (integrated bipolar 89/1,802 vs dedicated bipolar 9/140, P = 0.67). CONCLUSIONS: External noise and lead/connector noise were the primary causes, while T-wave oversensing was the least common cause of NAO resulting in ICD shock. Noise/artifact decreased immediately after a shock in nearly half of episodes. The specific ICD lead type did not impact the likelihood of NAO.

Long-term outcome after ICD and CRT implantation and influence of remote device follow-up: the ALTITUDE survival study.

BACKGROUND: Outcome data for patients receiving implantable cardioverter-defibrillator (ICD) and cardiac resynchronization therapy-defibrillator (CRT-D) devices treated outside of clinical trials are lacking. No clinical trial has evaluated mortality after device implantation or after shock therapy in large numbers of patients with implanted devices that regularly transmit device data over a network. METHODS AND RESULTS: Survival status in patients implanted with ICD and CRT devices across the United States from a single manufacturer was assessed. Outcomes were compared between patients followed in device clinic settings and those who regularly transmit remote data collected from the device an average of 4 times monthly. Shock delivery and electrogram analysis could be ascertained from patients followed on the network, enabling survival after ICD shock to be evaluated. One- and 5-year survival rates in 185,778 patients after ICD implantation were 92% and 68% and were 88% and 54% for CRT-D device recipients. In 8228 patients implanted with CRT-only devices, survival was 82% and 48% at 1 and 5 years, respectively. For the 69,556 ICD and CRT-D patients receiving remote follow-up on the network, 1- and 5-year survival rates were higher compared with those in the 116,222 patients who received device follow-up in device clinics only (50% reduction; P<0.0001). There were no differences between patients followed on or off the remote network for the characteristics of age, gender, implanted device year or type, and economic or educational status. Shock therapy was associated with subsequent mortality risk for both ICD and CRT-D recipients. CONCLUSIONS: Survival after ICD and CRT-D implantation in patients treated in naturalistic practice compares favorably with survival rates observed in clinical trials. Remote follow-up of device data is associated with excellent survival, but arrhythmias that result in device therapy in this population are associated with a higher mortality risk compared with patients who do not require shock therapy.

Real world evaluation of dual-zone ICD and CRT-D programming compared to single-zone programming: the ALTITUDE REDUCES study.

INTRODUCTION: We evaluated the frequency of appropriate and inappropriate shocks and survival in patients using dual-zone programming versus single-zone programming. METHODS AND RESULTS: For the ALTITUDE REDUCES study, patients were followed for 1.6 ± 1.1 years. The 12-month incidence of any shock was lower for dual-versus single-zone programmed detection at rates ≤170 bpm and between 170-200 bpm (P < 0.001). Appropriate shock rates at 1 year were also lower with dual-zone programming in these rate intervals (single zone 9.1%, 5.4%, P < 0.001, dual zone 6.7%, 4.7%, P < 0.02). There were no detectable differences between single- and dual-zone shock incidence at detection rates ≥ 200 bpm (P = 0.14). Inappropriate shock incidence was less with dual- versus single-zone detection at all detect rates <200 bpm, but not at rates ≥200 bpm (P < 0.001, P = 0.37). The lowest risk of appropriate and inappropriate shock was associated with dual-zone programming and detection rates ≥200 bpm (2.1%). Dual-zone detection was associated with more nonsustained and diverted therapy episodes but these patients did not have an increased risk of death compared to patients with single-zone programming. Patients programmed to low detection rate, single-zone detection and shock-only therapy also had the highest preshock mortality risk (P = 0.05). CONCLUSIONS: Shock incidence is lowest with either single- or dual-zone detection ≥200 bpm. For detection rates <200 bpm, dual-zone programming is associated with a reduction in the incidence of total shocks, appropriate shocks, and inappropriate shocks.

Implantable cardioverter defibrillator electrogram adjudication for device registries: methodology and observations from ALTITUDE.

BACKGROUND: The increasing use of remote monitoring with the associated large retrievable databases provides a unique opportunity to analyze observations on implantable cardioverter-defibrillator (ICD) therapies. Adjudication of a large number of stored ICD electrograms (EGMs) presents a unique challenge. The ALTITUDE study group was designed to use the LATITUDE remote monitoring system to evaluate ICD patient outcomes across the United States. METHODS AND RESULTS: Of 81,081 patients on remote monitoring, a random sample of 2,000 patients having 5,279 shock episodes was selected. The ALTITUDE EGM review committee was comprised of seven electrophysiologists from four institutions. An online EGM adjudication system was designed. Episodes were classified as appropriate (70% of shock episodes) or inappropriate ICD therapies (30%). Light's Kappa was used to assess agreement. Interobserver and intraobserver Kappa scores for dual-chamber ICDs were 0.84 (0.71-0.91) and 0.89 (0.82-0.95), consistent with substantial agreement. Interobserver and intraobserver Kappa scores for single-chamber ICDs were 0.61 (0.54-0.67) and 0.69 (0.59-0.79). The rhythm categories of "nonsustained arrhythmia" and "polymorphic and monomorphic ventricular tachycardia" resulted in the greatest degree of discordant adjudication between reviewers. CONCLUSIONS: This method of adjudication of a large volume of stored EGM data prior to device therapies will allow new observations in regards to device performance and has the potential to improve device programming and design. There was substantial interreviewer agreement for rhythm classification. Agreement was greater for dual-chamber compared to single-chamber devices, indicating the atrial lead adds diagnostic value in rhythm interpretation.

Predictors of early mortality in implantable cardioverter-defibrillator recipients.

AIMS: Multiple trials have shown that implantable cardioverter defibrillators (ICDs) prolong survival in secondary and primary prevention populations. However, in spite of the efficacy of these devices in terminating life-threatening arrhythmias, total mortality remains high. METHODS AND RESULTS: We evaluated 1703 patients (mean age: 67 +/- 12 years, 82% male) with conventional ICD indications, who were enrolled and followed between 2001 and 2004 at 128 US centres. Patients were followed for up to a year, and vital status was obtained for 1655 patients (97%, median follow-up: 377 days). There were 183 deaths within 1 year of ICD implantation (1-year mortality rate: 16%). Predictors of mortality included a history of atrial fibrillation (AF, P < 0.0001), diabetes (P = 0.0001), failure to use cholesterol-lowering medications (P < 0.001), use of digitalis and derivatives (P < 0.0001), use of diuretics (P < 0.0001), low body mass index (BMI, P < 0.0001), increasing age (P < 0.0001), low left ventricular ejection fraction (P < 0.0001), low activity hours (P < 0.0001), elevated resting heart rate (P = 0.014), low mean arterial pressure (MAP, P = 0.007), and poor functional status (New York Heart Association class, P < 0.0001). In multivariate modelling, AF (P < or = 0.001), diabetes (P = 0.004), BMI (P = 0.001), MAP (P = 0.040), and functional class (P = 0.006) predicted mortality. CONCLUSION: In this population undergoing ICD implantation, poor functional status, low MAP, diabetes, low BMI, and AF were strongly associated with death within a year.

Frequency, duration, and predictors of newly-diagnosed atrial fibrillation following dual-chamber pacemaker implantation in patients without a previous history of atrial fibrillation.

The Silent Atrial Fibrillation Detection With Stored EGMs (SAFE) registry is the first prospective study to characterize the incidence, duration, and predictors of atrial high-rate episodes (AHREs) in patients without previous clinically diagnosed atrial fibrillation after dual-chamber pacemaker implantation. Patients underwent in-clinic device interrogation at 2 weeks and then 3, 6, and 12 months after implantation. An AHRE was defined as an atrial tachyarrhythmia with an atrial rate > or =180 beats/min lasting > or =5 minutes. During the first month after pacemaker implantation, AHREs were identified in 68 patients (4.6%). Thirty-four of these patients (50%) did not have AHREs beyond the first month after implantation; these patients were older than those who continued to have AHREs (79 +/- 9 vs 74 +/- 12 years, p = 0.05). Within the first 6 months after pacemaker implantation, 150 patients (10%) experienced a total of 455 AHREs, of which only 28 (6%) prompted clinical visits. The 6-month freedom from an AHRE was 82%. Overall, 75% of patients with AHREs had multiple episodes; most AHREs lasted 5 to 60 minutes. In conclusion, 6 months after dual-chamber pacemaker implantation, 10% of patients experienced > or =1 AHRE, usually lasting 5 to 60 minutes. Some patients had AHREs only within the first 30 days after implantation, suggesting the possibility of transient atrial proarrhythmia related to lead insertion.

Racial disparity in the utilization of implantable-cardioverter defibrillators among patients with prior myocardial infarction and an ejection fraction of

Age-adjusted sudden cardiac death rates are highest for black patients compared with other racial groups. The prophylactic implantation of an implantable cardioverter-defibrillator (ICD) provides a significant reduction in sudden cardiac death and overall mortality in patients after myocardial infarctions with significant left ventricular systolic dysfunction. The purpose of this study was to determine whether black patients with left ventricular systolic dysfunction were less likely than white patients to receive ICDs for the primary prevention of sudden cardiac death. Data from the National Registry to Advance Heart Health (ADVANCENT) were analyzed to determine which patients with histories of myocardial infarctions and ejection fractions

Prognostic value of heart rate variability footprint and standard deviation of average 5-minute intrinsic R-R intervals for mortality in cardiac resynchronization therapy patients.

BACKGROUND: Cardiac resynchronization therapy devices provide effective therapy for heart failure. Heart rate variability (HRV) parameters in the device such as HRV footprint and SD of average 5-minute intrinsic R-R intervals (SDANN) are related to autonomic function and may be used to identify patients with a higher risk of mortality. METHODS: We examined the relationship between HRV and mortality in a prospective cohort study. The 842 patients (mean age, 67.7 +/- 11.2; 23.5 % female; New York Heart Association class III, 88.6%; class IV, 11.4%) included in the analysis were implanted with a cardiac resynchronization therapy with defibrillation device and had baseline HRV measurements available. RESULTS: During a median of 11.6 months of follow-up, 7.8% (66/842) of patients died. Heart rate variability footprint and SDANN were significant predictors of mortality (all P < .05); patients with lower HRV values were at greater risk for death, compared with patients with higher HRV values. Heart rate variability changes over time tended to predict the risk of mortality in follow-up (P = nonsignificant); patients with low baseline HRV and small changes in HRV during the follow-up period were at the highest risk for death (7% mortality for SDANN and 8.9% for HRV footprint), and patients with high baseline HRV and large changes in HRV were at the lowest risk (1.5% mortality for SDANN and 2.4% for HRV footprint). Results were consistent when adjusted for age, sex, body mass index, and diastolic blood pressure. CONCLUSIONS: Continuously measured device HRV parameters provide prognostic information about patient mortality that may be helpful for risk stratification.

Efficacy and temporal stability of reduced safety margins for ventricular defibrillation: primary results from the Low Energy Safety Study (LESS).

BACKGROUND: Traditionally, a safety margin of at least 10 J between the maximum output of the pulse generator and the energy needed for ventricular defibrillation has been used because lower safety margins were associated with unacceptably high rates of failed defibrillation and sudden cardiac death. The Low Energy Safety Study (LESS) was a prospective, randomized assessment of the safety margin requirements for modern implantable cardioverter-defibrillator (ICD) systems. METHODS AND RESULTS: A total of 636 patients undergoing initial ICD implantation with a dual-coil lead and active pulse generator were evaluated. The defibrillation threshold (DFT) and enhanced DFT (DFT+ and DFT++) were measured using a modified step-down protocol. Conversion testing of induced ventricular fibrillation before discharge, at 3 months, and at 12 months was performed, as was randomization to chronic programming at either 2 steps above DFT++ or maximal output. The induced ventricular fibrillation data had conversion success rates of 91.4%, 97.9%, 99.1%, 99.6%, and 99.8% for safety margins of 0, 1, 2, 3, and 4 steps above the DFT++, respectively. A margin of 4 to 6 J was adequate to maintain high conversion success over time (98.9% before discharge versus 99.2% at 12 months; P=NS). Over a mean follow-up of 24+/-13 months, conversion of spontaneously occurring ventricular tachyarrhythmias >200 bpm was identical (97.3%), despite a safety margin difference of 5.2+/-1.1 J for the 2-step group versus 20.8+/-4.2 J for maximal output. CONCLUSIONS: With a rigorous implantation algorithm, a safety margin of about 5 J is adequate for safe implantation of modern ICD systems.

The buddy wire technique: accessing lateral coronary veins while maintaining coronary sinus position.

There is compelling data to place the coronary sinus lead (CSL) in a lateral or posterolateral tributary. Coronary sinus venography often demonstrates the absence of easily accessible lateral veins or those with sufficient size to accommodate the CSL. The operator may choose to deploy the CSL in the anterior vein but publications and experience highlight the lack of resynchronization benefit when the CSL is deployed in this location. There is often a posterolateral vessel or the middle cardiac vein (MCV) originating from near the coronary sinus (CS) os. These vessels require the operator to pull the CS guide essentially out of the CS to allow successful access. Cannulation of the coronary sinus (CS) is often challenging, and the risk of losing access to the CS may dissuade the implanter from attempting access to a vessel near the CS os. We describe a technique to access vessels near the CS os while maintaining secure position in the main body of the CS.

Impact of shock energy and ventricular rhythm on the success of first shock therapy: the ALTITUDE first shock study.

BACKGROUND: The efficacy of shock in converting different ventricular tachyarrhythmias has not been well characterized in a large natural-practice setting. OBJECTIVE: To determine shock success rate by energy and ventricular rhythm in a large cohort of patients with implantable cardioverter-defibrillators. METHODS: Two thousand patients with 5279 shock episodes were randomly sampled for analysis from the LATITUDE remote monitoring system. Within an episode, the rhythm preceding therapy (shock or antitachycardia pacing [ATP]) was adjudicated. Patients who died after unsuccessful implantable cardioverter-defibrillator shocks did not transmit final remote monitoring data and were not included in the study. RESULTS: Of 3677 shock episodes for ventricular tachyarrhythmia, 2679 were treated with shock initially and were classified as monomorphic ventricular tachycardia ( n = 1544), polymorphic/monomorphic ventricular tachycardia (n = 371), or ventricular fibrillation (n = 764). The success rate after the first, second, and final shock averaged 90.3%, 96.4%, and 99.8%, respectively. After unsuccessful initial ATP (n = 998), the first, second, and final shock was successful in 84.8%, 92.9%, and 100% of the episodes. The success rate after the first or second shock was significantly lower after failed ATP compared to shock as first therapy (both P<.001). Among episodes treated initially with shock, the success rate for monomorphic ventricular tachycardia (89.2%) when treated with energy level ≤ 20 J was significantly higher than that for ventricular fibrillation (80.8%) (P = .04). The level of shock energy was a significant predictor of the success of the first shock (odds ratio 1.16; 95% confidence interval 1.03-1.30; P = .013). CONCLUSIONS: The success rate of first shock as first therapy is approximately 90%, but was lower after failed ATP. Programming a higher level of energy after ATP is suggested.

Survival after shock therapy in implantable cardioverter-defibrillator and cardiac resynchronization therapy-defibrillator recipients according to rhythm shocked. The ALTITUDE survival by rhythm study.

OBJECTIVES: This study sought to determine if the risk of mortality associated with inappropriate implantable cardioverter-defibrillator (ICD) shocks is due to the underlying arrhythmia or the shock itself. BACKGROUND: Shocks delivered from ICDs are associated with an increased risk of mortality. It is unknown if all patients who experience inappropriate ICD shocks have an increased risk of death. METHODS: We evaluated survival outcomes in patients with an ICD and a cardiac resynchronization therapy defibrillator enrolled in the LATITUDE remote monitoring system (Boston Scientific Corp., Natick, Massachusetts) through January 1, 2010. First shock episode rhythms from 3,809 patients who acutely survived the initial shock were adjudicated by 7 electrophysiologists. Patients with a shock were matched to patients without a shock (n = 3,630) by age at implant, implant year, sex, and device type. RESULTS: The mean age of the study group was 64 ± 13 years, and 78% were male. Compared with no shock, there was an increased rate of mortality in those who received their first shock for monomorphic ventricular tachycardia (hazard ratio [HR]: 1.65, p < 0.0001), ventricular fibrillation/polymorphic ventricular tachycardia (HR: 2.10, p < 0.0001), and atrial fibrillation/flutter (HR: 1.61, p = 0.003). In contrast, mortality after first shocks due to sinus tachycardia and supraventricular tachycardia (HR: 0.97, p = 0.86) and noise/artifact/oversensing (HR: 0.91, p = 0.76) was comparable to that in patients without a shock. CONCLUSIONS: Compared with no shock, those who received their first shock for ventricular rhythms and atrial fibrillation had an increased risk of death. There was no significant difference in survival after inappropriate shocks for sinus tachycardia or noise/artifact/oversensing. In this study, the adverse prognosis after first shock appears to be more related to the underlying arrhythmia than to an adverse effect from the shock itself.

Design and rationale of the assessment of proper physiologic response with rate adaptive pacing driven by minute ventilation or accelerometer (APPROPRIATE) trial.

Rate-adaptive sensors are designed to restore a physiologic heart rate response to activity, in particular for patients that have chronotropic incompetence (CI). Limited data exist comparing two primary types of sensors; an accelerometer (XL) sensor which detects activity or motion and a minute ventilation (MV) sensor, which detects the product of respiration rate and tidal volume. The APPROPRIATE study will evaluate the MV sensor compared with the XL sensor for superiority in improving functional capacity (peak VO(2)) in pacemaker patients that have CI. This study is a double-blind, randomized, two-arm trial that will enroll approximately 1,000 pacemaker patients. Patients will complete a 6-min walk test at the 2-week visit to screen for potential CI. Those projected to have CI will advance to a 1-month visit. At the 1-month visit, final determination of CI will be done by completing a peak exercise treadmill test while the pacemaker is programmed to DDDR with the device sensors set to passive. Patients failing to meet the study criteria for CI will not continue further in the trial. Patients that demonstrate CI will be randomized to program their rate-adaptive sensors to either MV or XL in a 1:1 ratio. The rate-adaptive sensor will be optimized for each patient using a short walk to determine the appropriate response factor. At a 2-month visit, patients will complete a CPX test with the rate-adaptive sensors in their randomized setting.

Changes in heart rate variability, quality of life, and activity in cardiac resynchronization therapy patients: results of the HF-HRV registry.

BACKGROUND: Cardiac resynchronization therapy (CRT) is a viable therapy in the treatment of heart failure (HF). Heart rate variability (HRV) is a prognostic marker of HF and mortality and is a sign of autonomic dysfunction. Acute improvements in measures of HRV have been demonstrated after CRT in small clinical studies. The purpose of the present study was to evaluate changes in HRV and patient outcomes over time and the relationship between these changes in a large generalized sample of patients who received CRT with defibrillator (CRT-D). METHODS: The Heart Failure-Heart Rate Variability (HF-HRV) registry enrolled 1,421 patients who received a CRT-D device capable of measuring HRV. Patients were followed for a 1-year period. Device diagnostics, including HRV footprint; standard deviation of averaged normal R to R intervals (SDANN); and mean, minimum, and maximum heart rate were measured at each visit, in addition to activity log, New York Heart Association (NYHA) class, and quality of life (QOL) data. RESULTS: This large sample of HF patients showed an overall improvement in SDANN (69.2 +/- 25.5, 78.5 +/- 27.8, 79.4 +/- 27.2, 80.7 +/- 28.2) and HRV footprint (31.5 +/- 11.8, 33.4 +/- 12.3, 34.2 +/- 12.2, 34.5 +/- 12.3) at the 2 week, 3 month, 6 month, and 12 month visits, respectively (both P < 0.001). There were also significant changes over time in clinical status (improved QOL, increased activity, and improved NYHA, all P < 0.0001), with the greatest changes occurring between the 2 week and 3 month visits. CONCLUSION: In conclusion, these study results demonstrate that device measured HRV parameters and patient outcomes significantly improve after receipt of CRT.

T-wave oversensing in implantable cardiac defibrillators is due to technical failure of device sensing.

The expanded indications for the use of implantable cardioverter defibrillators (ICDs) for primary prevention of sudden cardiac death have increased concerns about inappropriate delivery of therapies. Dual-chamber systems have improved the capacity of ICDs to differentiate ventricular arrhythmias from supraventricular arrhythmias. Still, T-wave oversensing is a major source of inappropriate therapy. It is likely the true incidence of T-wave oversensing is greater than reported as documented events reflect only those stored in a device memory. Reviewing cases of T-wave oversensing that failed noninvasive correction; we found successful resolution resulted from generator replacement. We conclude that T-wave oversensing is due to inadequate signal processing by some ICD generators.