Cardiac Resynchronization Therapy-defibrillator Device Research Articles

Potential value of automated daily screening of cardiac resynchronization therapy defibrillator diagnostics for prediction of major cardiovascular events: results from Home‐CARE (Home Monitoring in Cardiac Resynchronization Therapy) study

AimTo investigate whether diagnostic data from implanted cardiac resynchronization therapy defibrillators (CRT-Ds) retrieved automatically at 24 h intervals via a Home Monitoring function can enable dynamic prediction of cardiovascular hospitalization and death.Methods and resultsThree hundred and seventy-seven heart failure patients received CRT-Ds with Home Monitoring option. Data on all deaths and hospitalizations due to cardiovascular reasons and Home Monitoring data were collected prospectively during 1-year follow-up to develop a predictive algorithm with a predefined specificity of 99.5%. Seven parameters were included in the algorithm: mean heart rate over 24 h, heart rate at rest, patient activity, frequency of ventricular extrasystoles, atrial–atrial intervals (heart rate variability), right ventricular pacing impedance, and painless shock impedance. The algorithm was developed using a 25-day monitoring window ending 3 days before hospitalization or death. While the retrospective sensitivities of the individual parameters ranged from 23.6 to 50.0%, the combination of all parameters was 65.4% sensitive in detecting cardiovascular hospitalizations and deaths with 99.5% specificity (corresponding to 1.83 false-positive detections per patient-year of follow-up). The estimated relative risk of an event was 7.15-fold higher after a positive predictor finding than after a negative predictor finding.ConclusionWe developed an automated algorithm for dynamic prediction of cardiovascular events in patients treated with CRT-D devices capable of daily transmission of their diagnostic data via Home Monitoring. This tool may increase patients’ quality of life and reduce morbidity, mortality, and health economic burden, it now warrants prospective studies.ClinicalTrials.gov NCT00376116.

The impact of atrial fibrillation with rapid ventricular rates and device programming on shocks in 106,513 ICD and CRT-D patients

The relationship between shocks, device programming, and atrial fibrillation (AF) with a rapid ventricular rate (AF + RVR) using continuous daily monitoring has not been studied in large number of patients with implantable cardioverter-defibrillators (ICDs). The aim of this analysis was to determine the impact of ICD programming and ventricular rate control during AF on ICD shocks. An observational cohort analysis was performed with dual-chamber ICD and cardiac resynchronization therapy-defibrillator devices. The primary endpoint was spontaneous all-cause shocked episodes per 100 patient-years. Shock reduction programming strategies were entered into a multivariable model including slowest ventricular tachycardia/ventricular fibrillation (VT/VF) detection threshold, number of intervals to detect VF (NID), supraventricular tachycardia (SVT) discriminators ON, antitachycardia pacing (ATP) ON for fast VTs (FVTs) and AF + RVR (AF ≥1 hour for ≥1 day with average ≥110 beats per minute). We also characterized the predictive ability of AF + RVR to identify patients at risk of subsequent shocks. There were 106,513 patients at 2858 institutions, with 2.5 ± 1.4 years of follow-up, 75% being male, age 67 ± 12 years, 59% with dual-chamber ICDs, and 11% with AF + RVR. A total of 22,062 patients (21%) received 82,396 shocks. After adjusting for all variables, AF + RVR, slower VT/VF detection threshold, and shorter VF NID were found to be associated with more shocks (P < .05 for all). Continuous monitoring of AF + RVR identified patients at up to 5-fold increased risk of shocks. Faster VT/VF detection thresholds, longer detection durations, use of SVT discriminators, and delivery of ATP reduces all-cause ICD shocks. Continuous monitoring of AF + RVR identifies patients at the highest risk of future ICD shocks.

Significant Increase in the Incidence of Ventricular Arrhythmic Events After an Intrathoracic Impedance Change Measured With a Cardiac Resynchronization Therapy Defibrillator

Cardiac resynchronization therapy defibrillator (CRT-D) devices are now capable of monitoring changes in intrathoracic impedance. Intrathoracic impedance monitoring resulting in a fluid index threshold crossing has been proven to predict heart failure (HF) exacerbations. We retrospectively investigated the relationship between changes in intrathoracic impedance and the occurrence of arrhythmic events. From 282 patients with New York Heart Association class III or IV HF who were implanted with a CRT-D device with a fluid index feature based on intrathoracic impedance monitoring capabilities, arrhythmic events were retrospectively analyzed in terms of the threshold crossings. The patients were divided into 2 groups: those with fluid index threshold crossings and those without threshold crossings. A total of 4,725 tachyarrhythmic events were reported in 129 patients (46%), and there were 221 fluid index crossing events in 145 patients (51%) during 10.0 ± 3.2 months. Tachyarrhythmic events were more frequently recorded in patients with threshold crossing events than in those who did not experience a threshold crossing (3,241 vs. 1,484 events, P<0.0001). Ventricular tachyarrhythmic events mainly occurred within the first 30 days after the threshold crossing event; however, a similar trend was not observed for the atrial tachyarrhythmic events. Intrathoracic impedance monitoring may predict arrhythmic events, especially ventricular arrhythmias, in patients with HF and provides an additional management tool.

A Tachycardia classified as Supraventricular by a Cardiac Resynchronization Therapy-Defibrillator Device. What is the Mechanism?

Figure 1. Programmed tachycardia parameters in the Epic II+ HF device. tachycardia (VT), baseline left bundle branch block, and New York Heart Association class III heart failure. The programmed parameters were as follows: base rate 50/min, maximum tracking rate 125/min, sensed/paced atrioventricular (AV) delays 140/190 ms, rate-responsive AV delay— medium, and biventricular pacing with left ventricular first at 35 ms. The thresholds of all three leads were adequate and the programmed output had enough safety margin. The measured P and R waves were >3 mV and >12 mV, respectively. The special sensing parameters for atrial lead were automatic sensitivity with maximum 0.2 mV, decay delay 0 ms, and threshold start of 50% and for the ventricular lead were 0.3 mV, 60 ms, and 62.5%, respectively. The programmed tachycardia parameters were as seen in Figure 1. Stored electrogram (EGM) of an asymptomatic episode diagnosed

Long-Term Outcome After ICD and CRT Implantation and Influence of Remote Device Follow-Up

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 &lt;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.

Antiarrhythmic Effect of Reverse Electrical Remodeling Associated with Cardiac Resynchronization Therapy

Antiarrhythmic and proarrhythmic effects of cardiac resynchronization therapy (CRT) remain controversial. We hypothesized that reverse electrical remodeling (RER) with CRT is associated with reduced frequency of ventricular tachyarrhythmias (VTs). The width of native and paced QRS was measured in lead II electrocardiogram before and 13 ± 7 months after implantation of a CRT defibrillator device in 69 patients (mean age 66.3 ± 13.9; 39 males [83%]) with bundle branch block (BBB) (41 patients with left BBB and three patients with bifascicular block) or nonspecific intraventricular conduction delay (25 patients, 36%), and New York Heart Association class III-IV heart failure. Biventricular pacing was inhibited for 10 seconds to record native QRS. RER was defined as a decrease in the native QRS duration ≥10 ms compared to preimplant. Patients were followed prospectively 24 ± 13 months after assessment for electrical remodeling. RER was observed in 22 patients (32%), among whom QRS duration decreased by 30.9 ± 14.1 ms (P < 0.00001) with similar heart rate and QRS morphology. Native QRS duration increased by 10.3 ± 16.6 ms in the other 47 patients (68%) (P = 0.0001). Baseline mean ejection fraction did not differ between patients with and those without RER (24.9 ± 10.0 vs 24.2 ± 8.6%, NS). During 2 ± 1 years of further follow-up, 19 patients had VTs and 12 patients died. RER was associated with a fourfold decrease in the risk of death or sustained VTs requiring appropriate implantable cardioverter-defibrillator therapies, whichever came first (hazard ratio 0.25; 95% confidence interval 0.08-0.85; P = 0.026). RER of the native conduction with CRT is associated with decreased mortality and antiarrhythmic effect of CRT.

Acute Lead Dislodgements and In-Hospital Mortality in Patients Enrolled in the National Cardiovascular Data Registry Implantable Cardioverter Defibrillator Registry

We sought to describe the incidence of acute lead dislodgements and the consequences of these events in patients enrolled in the National Cardiovascular Data Registry (NCDR) Implantable Cardioverter-Defibrillator (ICD) Registry. Lead dislodgements are common adverse events in patients undergoing ICD implants. Little is known regarding who is at risk and the consequences of these events. Patients enrolled between April 2006 and September 2008 were included. Acute lead dislodgement was defined as movement of the lead requiring another procedure for repositioning before discharge. Acute dislodgement occurred in 2,628 of 226,764 patients. Univariate variables associated with dislodgements included older age, female sex, and patients with atrial fibrillation, chronic lung disease, cerebrovascular disease, nonischemic cardiomyopathy, and lower ejection fractions (all p < 0.002). After multivariate adjustment, factors associated with an increased risk for dislodgement included New York Heart Association functional class IV heart failure, atrial fibrillation/flutter, having a cardiac resynchronization therapy-defibrillator device, and procedures performed by physicians trained under alternative pathways. A teaching/training hospital setting was not a factor (p = 0.64). Acute dislodgements had increased odds for other adverse events including cardiac arrest, cardiac tamponade, device infection, pneumothorax, and in-hospital death even after adjustment for potential confounders (all p < 0.0001). Acute lead dislodgements occur more often in patients with more comorbidities and in patients undergoing implants by nonelectrophysiology-trained implanters. These events were strongly associated with increased odds for in-hospital death.

BIVentricular versus right ventricular antitachycardia pacing to terminate ventricular tachyarrhythmias in patients receiving cardiac resynchronization therapy: The ADVANCE CRT-D Trial

This multicenter, prospective, randomized, controlled, parallel trial compares the efficacy of biventricular (BIV) versus right ventricular (RV) antitachycardia pacing (ATP) in terminating all kinds of ventricular tachycardia (VT). Five hundred twenty-six patients implanted with a cardiac resynchronization therapy defibrillator (CRT-D) device were enrolled and randomized 1:1 to either BIV (266) or RV (260) ATP (single burst 8 pulse, 88% coupling interval) and were followed up for 12 months. During 12 months' follow-up, 1,077 ventricular episodes in 180 patients were detected and classified: 634 true VTs divided into 69 ventricular fibrillation (VF) (11%), 202 fast ventricular tachycardia (FVT) (32%), and 363 VT (57%). A comparable first ATP efficacy (BIV 65% vs RV 68%, P = .59) was observed in FVT + VT, in VT zone (BIV 62% vs RV 71%, P = .25), and in FVT zone (BIV 71% vs RV 61%, P = .34). A trend toward lower accelerations during ATP applied to FVT was observed in the BIV group (3.5% BIV vs 10.2% RV, P = .163). No syncope/presyncope occurred during ATP for FVT in the BIV group versus 4 events (3.2%) in the RV group (P = .016). biventricular ATP was more effective in treating FVT in coronary artery disease (CAD) patients (P = .032), whereas both modalities presented similar efficacy in patients with non-CAD etiology (P = .549). Antitachycardia pacing is effective in patients implanted with a CRT-D device. No significant differences in efficacy emerged between BIV- and RV-delivered ATP in the general population, whereas BIV ATP seems to present a safer profile in ischemic patients.

Multicenter randomized study of anticoagulation guided by remote rhythm monitoring in patients with implantable cardioverter-defibrillator and CRT-D devices: Rationale, design, and clinical characteristics of the initially enrolled cohort: The IMPACT study

Atrial fibrillation and atrial flutter are common cardiac arrhythmias associated with an increased risk of stroke in patients with additional risk factors. Anticoagulation ameliorates stroke risk, but because these arrhythmias may occur intermittently without symptoms, initiation of prophylactic therapy is often delayed until electrocardiographic documentation is obtained. The IMPACT study is a multicenter, randomized trial of remote surveillance technology in patients with implanted dual-chamber cardiac resynchronization therapy defibrillator (CRT-D) devices designed to test the hypothesis that initiation and withdrawal of oral anticoagulant therapy guided by continuous ambulatory monitoring of the atrial electrogram improve clinical outcomes by reducing the combined rate of stroke, systemic embolism, and major bleeding compared with conventional clinical management. For those in the intervention group, early detection of atrial high-rate episodes (AHRE) generates an automatic alert to initiate anticoagulation based on patient-specific stroke risk stratification. Subsequently, freedom from AHRE for predefined periods prompts withdrawal of anticoagulation to avoid bleeding. Patients in the control arm are managed conventionally, the anticoagulation decision prompted by incidental detection of atrial fibrillation or atrial flutter during routine clinical follow-up. The results will help define the clinical utility of wireless remote cardiac rhythm surveillance and help establish the critical threshold of AHRE burden warranting anticoagulant therapy in patients at risk of stroke. In this report, we describe the study design and baseline demographic and clinical features of the initial cohort (227 patients).

Left Ventricular Mechanical Assist Devices and Cardiac Device Interactions: An Observational Case Series

Nonpulsatile left ventricular assist devices (LVADs) are increasingly used for treatment of refractory heart failure. A majority of such patients have implanted cardiac devices, namely implantable cardioverter-defibrillators (ICDs) or cardiac resynchronization therapy-pacemaker (CRT-P) or cardiac resynchronization therapy-defibrillator (CRT-D) devices. However, potential interactions between LVADs and cardiac devices in this category of patients remain unknown. We reviewed case records and device logs of 15 patients with ICDs or CRT-P or CRT-D devices who subsequently had implantation of a VentrAssist LVAD (Ventracor Ltd., Chatswood, Australia) as destination therapy or bridge to heart transplantation. Pacemaker and ICD lead parameters before and after LVAD implant were compared. In addition, ventricular tachyarrhythmia event logs and potential electromagnetic interference reports were evaluated. Right ventricular (RV) sensing decreased in the first 6 months post-LVAD. Mean R-wave amplitude preimplant was 10.9 +/- 5.25 mV compared with 7.2 +/- 3.4 mV during follow-up (P = 0.02). RV impedance also decreased from 642 +/- 240 ohms at baseline to 580 +/- 212 ohms at follow-up (P = 0.007). There was a significant increase in RV stimulation threshold following implantation of the LVAD from 0.8 +/- 0.6 V at baseline to 1.4 +/- 1.0 V in the first 6 months postimplant (P = 0.01). A marked increase in ventricular tachyarrhythmia burden was observed in three patients. One patient displayed electromagnetic interference between the LVAD and defibrillator, resulting in inappropriate defibrillation therapy. LVADs have a definite impact on cardiac devices in respect with alteration of lead parameters, ventricular tachyarrhythmias, and electromagnetic interference.

Twiddler's syndrome in a patient with a biventricular-defibrillator device

A 69-year-old man with previous myocardial infarction and proximal three-vessel coronary artery disease underwent coronary bypass grafting, with an epicardial lead placed on the lateral left ventricular wall during surgery. A cardiac resynchronization therapy-defibrillator (CRT-D) device was subsequently implanted using active right atrial and right ventricular leads, with the pulse generator placed in a pre-pectoral pocket. Four weeks later, the right atrial lead was failing to sense or capture, and chest X-ray revealed it had pulled out of the myocardium and coiled up behind the device; a diagnosis of Twiddler's syndrome was made. Twiddler's syndrome is unusual in patients with CRT-D devices and may cause symptoms such as inappropriate shocks and hiccups. Placement of the pulse generator in a sub-pectoral position may help prevent it.

Remote Active Monitoring in Patients With Heart Failure (RAPID-RF): Design and Rationale

Heart failure (HF) ambulatory disease management programs appear to offer the greatest benefit to HF patients at highest risk, defined as having New York Heart Association (NYHA) functional Class III or IV symptoms. The Latitude Patient Management System is the first HF management tool to use wireless telemetry present in a cardiac resynchronization therapy defibrillator (CRT-D) device that is linked to remotely collect blood pressure and weight measures, permitting a single transmission reporting device data. Potential advantages of this system include ease of data transmissions, correlation among measures of HF status, arrhythmic events, and device performance. However, the use and ultimate utility of these combined features for patient management are untested. The Remote Active Monitoring in Patients with Heart Failure (RAPID-RF) study is a multicenter registry that will enroll up to 1000 patients on the Latitude Patient Management System from approximately 100 centers. The primary objective is to examine physician responses to Latitude Active Monitoring data alerts by assessing alert-related medical interventions. Minimum follow-up will be 3 months after implant with a maximum follow-up time of 24 months after implant. The RAPID-RF study will provide important preliminary data on how remotely collected HF and arrhythmic surveillance data alter the management of HF patients with CRT-D devices.

Pacing Evaluation—Atrial SUpport Study in Cardiac Resynchronization Therapy (PEGASUS CRT): Design and rationale

Cardiac resynchronization therapy (CRT) has been demonstrated to be an effective heart failure (HF) therapy. All pivotal trials of CRT to date have used atrial-synchronous biventricular pacing wherein there is no or minimal atrial pacing. In clinical practice, however, physicians often program CRT devices to have atrial rate support pacing, either by increasing the lower rate limit or by activating the rate sensor. The purpose of this study is to evaluate the effect of empiric atrial support pacing in patients with HF who have received a CRT defibrillator (CRT-D) device. PEGASUS CRT is a multicenter, 3-arm, randomized clinical trial of approximately 1200 patients receiving a CRT-D device. For the first 6 weeks after implant, devices are programmed to DDD with a lower rate limit of 40 beats/min. At 6 weeks, patients are randomized to DDD-40, DDD-70, or DDDR-40. All randomized patients are followed for 1 year, and at each visit, mortality, HF events, quality of life, New York Heart Association class, and atrial and ventricular arrhythmic episodes are evaluated. An exercise substudy will also be conducted, enrolling a minimum of 375 patients. Patients in this substudy will complete 2 cardiopulmonary exercise tests to evaluate the effect pacing mode has on exercise capacity. This randomized controlled trial will address whether empiric atrial support pacing is of clinical benefit to patients with HF who receive a CRT-D device.

Acute Evaluation of Programmer‐Guided AV/PV and VV Delay Optimization Comparing an IEGM Method and Echocardiogram for Cardiac Resynchronization Therapy in Heart Failure Patients and Dual‐Chamber ICD Implants

Intracardiac delay optimization of biventricular and dual-chamber pacing devices currently relies on time-consuming echocardiographic measurements. A novel intracardiac electrogram (IEGM) method for atrioventricular (AV/PV) and interventricular (VV) delay optimization was developed, which can be performed during routine device follow-up. In this prospective, nonrandomized, multi-center trial, patients previously implanted with St. Jude Medical cardiac resynchronization therapy defibrillator (CRT-D) devices or dual-chamber implantable cardioverter defibrillators (ICDs) underwent standard AV/PV and/or VV delay optimization guided by Doppler echocardiogram measurements of the maximum aortic velocity time integral (aortic VTI). Aortic VTI measurements applying the IEGM method recommended delays were then obtained in all patients. Fifty-eight patients (age: 68 +/- 11 years; 81% male; 74% ischemic) and 57 patients (age: 71 +/- 10 years; 74% male; 71% ischemic) were enrolled for AV/PV and VV delay evaluation, respectively. An independent core lab determined the maximum aortic VTIs. Data analysis of the AV, PV, and VV delays demonstrated the concordance correlation coefficient (CCC) between the standard method aortic VTI values and the IEGM method aortic VTI values was 97.5%, 96.1%, and 96.6%, respectively. All analyses demonstrated that the CCC > 90% (P < 0.05). The automated programmer-based IEGM method provides a reliable and simpler alternative to standard techniques for the optimization of AV/PV and VV delay settings in patients with CRT-D devices and dual-chamber ICDs.

Predictors of Appropriate Defibrillator Therapy Among Patients with an Implantable Defibrillator That Delivers Cardiac Resynchronization Therapy

The purpose of this study was to determine predictors of appropriate implantable defibrillator (ICD) therapy among patients with heart failure who are treated with a cardiac resynchronization therapy-defibrillator (CRT-D). Patients enrolled in the Ventak CHF/Contak CD study were treated with a CRT-D device and were required to have NYHA class II-IV CHF, QRS duration > or = 120 msec, and a class I or II indication for an ICD. The study database was retrospectively analyzed during the 6-month postimplant period to identify predictors of appropriate ICD therapy. Five hundred and one of the 581 patients enrolled in the trial had successful device implantation and were included in this analysis. Patients were mostly male (83%), 66 +/- 11 years old, and had coronary artery disease (69%), a mean left ventricular ejection fraction (EF) = 0.22 +/- 0.07, and NYHA class II (33%), III (58%), or IV (9%) CHF symptoms. During 6 months of follow-up, 73 of 501 (14%) patients received an appropriate ICD therapy. Two independent predictors of appropriate therapy were identified: a history of a spontaneous, sustained ventricular arrhythmia (HR = 2.05; 95% CI = 1.31-3.20; P = 0.002) and NYHA class IV CHF (HR = 1.81; 95% CI = 1.10-2.96; P = 0.019). When patients with NYHA class II were excluded from analysis, a history of a sustained ventricular arrhythmia and the presence of NYHA class IV CHF symptoms remained as independent predictors of appropriate ICD therapy. In a select population of advanced heart failure patients receiving a CRT-D, NYHA class IV CHF was a powerful independent predictor of appropriate ICD therapy. Approximately one-quarter of the patients with NYHA class IV CHF who received a CRT-D device received an appropriate ICD therapy within 3 months after implant. Additional studies are needed to confirm an association between class IV CHF symptoms and an increased frequency of ICD shocks.

Wireless remote monitoring for patients with atrial tachyarrhythmias

A 2008 expert consensus statement recommended an in-person follow-up visit between 2 and 12 weeks after the placement of a new cardiovascular implantable electronic device (CIED).To assess outcomes associated with adherence to the experts’ recommendations.By using data from the National Cardiovascular Data Registry’s (NCDR®) ICD Registry™ linked to Medicare claims, we studied the association between follow-up within 2–12 weeks after CIED placement between January 1, 2005, and September 30, 2008, and all-cause mortality and risk of readmission within 1 year.Compared with patients who did not receive the recommended follow-up (n = 43,060), those who did (n = 30,256) were more likely to be older, white, to have received a cardiac resynchronization therapy-defibrillator device, to have more advanced heart failure symptoms, and to have nonischemic dilated cardiomyopathy. In Cox proportional hazards models adjusted for patient demographic and clinical factors, mortality was lower (hazard ratio [HR] 0.93; 95% confidence interval [CI] 0.88–0.98; P = .005) but cardiovascular readmission was higher (HR 1.04; 95% CI 1.01–1.08; P = .012) among patients who received initial follow-up within 2–12 weeks after CIED placement compared with those who did not. There was no association between CIED follow-up and readmission for heart failure (HR 1.00; 95% CI 0.96–1.05; P = .878) or device-related infection (HR 1.22; 95% CI 0.98–1.51; P = .075).Follow-up within 2–12 weeks after CIED placement was independently associated with improved survival but increased cardiovascular readmission. Quality improvement initiatives designed to increase adherence to experts’ recommendations may be warranted.