Atrial Fibrillation Therapy in Patients with a CRT Defibrillator with Wireless Telemetry

Electrical treatment of atrial arrhythmias in heart failure patients implanted with a dual defibrillator CRT device. Results from the TRADE-HF study

BACKGROUND

Ventricular and atrial arrhythmias commonly occur in heart failure patients and are a significant source of symptoms, morbidity and mortality. Some specific generators referred to as dual defibrillators, Dual CRT-Ds, have the ability to treat atrial and ventricular arrhythmias. TRADE-HF is a prospective two-arm randomized study aimed at assessing the benefits of complete automatic management of atrial arrhythmias in patients implanted with a dual CRT-D.

METHODS

Primary objective of the TRADE-HF study was to document reduction of unplanned hospital admission for cardiac reasons or death for cardiovascular causes or progression to permanent AF, by comparing fully-automatic device driven therapy for atrial tachycardia or fibrillation (AT/AF) to an in-hospital approach for treatment of symptomatic AT/AF. Randomized Patients were followed every 6months for 3years to assess the primary objective.

RESULTS

Four-hundred-twenty patients have been enrolled in the study. At the end of the study 30 subjects died for cardiovascular causes, 60 had at least one hospitalization for cardiovascular causes and 14 developed permanent AF. Eighty-seven patients experienced a composite event. Hazard Ratio for device-managed automatic therapy arm compared to traditional was 0.987 (95% CI: 0.684-1.503; p=0.951). The primary endpoint analysis resulted in no difference between the device managed and in-hospital treatment arm.

CONCLUSION

The TRADE-HF study failed to demonstrate a reduction in the composite of unplanned hospitalizations for cardiovascular causes or death for cardiovascular causes or progression to permanent AF using automatic atrial therapy compared to a traditional approach including hospitalization for symptomatic episodes and/or in-hospital treatment of AT/AF.

The role of implantable devices to treat atrial fibrillation

In the last decades several nonpharmacological therapies for the treatment and prevention of atrial fibrillation (AF) have been developed. Pacemakers play a potential important role in the nonpharmacological management of AF. In patients with sinus node dysfunction both, atrial and dual-chamber pacing, have been proven to prevent or delay progression to permanent AF compared with ventricular pacing alone. However, in patients without conventional indications for pacing, the utility of pacemakers as a stand-alone therapy has not yet proven. Following the positive results obtained by low energy internal defibrillation, specific implantable devices for AF cardioversion have been developed. Despite implantable atrial defibrillators being possible alternatives for drug refractory AF, industry did not further develop these due to shock discomfort. Newer implantable pulse generators also offer data storage that permits detection of asymptomatic AF. Such a help provided by implantable devices, has been enhanced by the development and spread out of remote monitoring systems.

Early performance of a miniaturized leadless cardiac pacemaker: the Micra Transcatheter Pacing Study

AIMS

Permanent cardiac pacing is the only effective treatment for symptomatic bradycardia, but complications associated with conventional transvenous pacing systems are commonly related to the pacing lead and pocket. We describe the early performance of a novel self-contained miniaturized pacemaker.

METHODS AND RESULTS

Patients having Class I or II indication for VVI pacing underwent implantation of a Micra transcatheter pacing system, from the femoral vein and fixated in the right ventricle using four protractible nitinol tines. Prespecified objectives were >85% freedom from unanticipated serious adverse device events (safety) and <2 V 3-month mean pacing capture threshold at 0.24 ms pulse width (efficacy). Patients were implanted (n = 140) from 23 centres in 11 countries (61% male, age 77.0 ± 10.2 years) for atrioventricular block (66%) or sinus node dysfunction (29%) indications. During mean follow-up of 1.9 ± 1.8 months, the safety endpoint was met with no unanticipated serious adverse device events. Thirty adverse events related to the system or procedure occurred, mostly due to transient dysrhythmias or femoral access complications. One pericardial effusion without tamponade occurred after 18 device deployments. In 60 patients followed to 3 months, mean pacing threshold was 0.51 ± 0.22 V, and no threshold was ≥2 V, meeting the efficacy endpoint (P < 0.001). Average R-wave was 16.1 ± 5.2 mV and impedance was 650.7 ± 130 ohms.

CONCLUSION

Early assessment shows the transcatheter pacemaker can safely and effectively be applied. Long-term safety and benefit of the pacemaker will further be evaluated in the trial.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov ID NCT02004873.

Low efficacy of cardioversion of persistent atrial fibrillation with the implantable cardioverter-defibrillator

AIMS

Atrial fibrillation (AF) and heart failure are conditions that often coexist. Consequently, many patients with an implantable cardioverter-defibrillator (ICD) present with AF. We evaluated the effectiveness of internal cardioversion of AF in patients with an ICD.

METHODS

Retrospectively, we included 27 consecutive ICD patients with persistent AF who underwent internal cardioversion using the ICD. When ICD cardioversion failed, external cardioversion was performed.

RESULTS

Patients were predominantly male (89 %) with a mean (SD) age of 65 ± 9 years and left ventricular ejection fraction of 36 ± 17 %. Only nine (33 %) patients had successful internal cardioversion after one, two or three shocks. The remaining 18 patients underwent external cardioversion after they failed internal cardioversion, which resulted in sinus rhythm in all. A smaller left atrial volume (99 ± 36 ml vs. 146 ± 44 ml; p = 0.019), a longer right atrial cycle length (227 (186-255) vs. 169 (152-183) ms, p = 0.030), a shorter total AF history (2 (0-17) months vs. 40 (5-75) months, p = 0.025) and dual-coil ICD shock (75 % vs. 26 %, p = 0.093) were associated with successful ICD cardioversion.

CONCLUSION

Internal cardioversion of AF in ICD patients has a low success rate but may be attempted in those with small atria, a long right atrial fibrillatory cycle length and a short total AF history, especially when a dual-coil ICD is present. Otherwise, it seems reasonable to prefer external over internal cardioversion when it comes to termination of persistent AF.

Continuous monitoring of atrial fibrillation in heart failure

In patients with atrial fibrillation (AF) undergoing cardiac resynchronization therapy (CRT) for heart failure, continuous monitoring of the percentage of biventricular BiV% pacing has shown that the greatest improvement and reduction in mortality occur with a BiV pacing greater than 98%. Continuous monitoring of BiV pacing has improved the CRT management of patients with AF. Continuous monitoring has generated important new questions about anticoagulant therapy, which require randomized trials. Anticoagulant therapy should probably be considered in patients who have a high risk of thromboembolism according to standard scoring systems.

Is An Atrial Defibrillator Still An Option In Treating Patients With Atrial Fibrillation?

Atrial fibrillation (AF) is a common disorder associated with significant morbidities and presents several challenges for the control of symptoms and prevention of long-term implications. Atrial defibrillators (ADs), used for rhythm control in patients with symptoms refractory to medical therapy, can detect recurrences of the arrhythmia, allow prompt patient-directed treatment, and have the potential to reduce hospitalizations and improve quality of life. The efficacy of this form of therapy is highest in patients with paroxysmal AF, and with the use of a coronary sinus shocking lead. While R-wave synchronized shocks are a prerequisite for a safe use, the procedure is well tolerated and usually not associated with long-term psychological side effects. Limitations of ADs include acute and chronic complications related to cardiac rhythm device implantation, the requirement in some cases for more than one shock to terminate AF, the discomfort from shocks, as well as the need for sedation to alleviate pain from the shocks. With the ever-expanding role of catheter-based therapies for AF, it seems that the role of ADs in this regard is rather limited.

Significant increase in the incidence of ventricular arrhythmic events after an intrathoracic impedance change measured with a cardiac resynchronization therapy defibrillator

BACKGROUND

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.

METHODS AND RESULTS

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.

CONCLUSIONS

Intrathoracic impedance monitoring may predict arrhythmic events, especially ventricular arrhythmias, in patients with HF and provides an additional management tool.

Early detection of adverse events with daily remote monitoring versus quarterly standard follow-up program in patients with CRT-D

BACKGROUND

A relative high rate of clinical and device-related adverse events (AE) is generally reported in patients with implantable defibrillators for cardiac resynchronization therapy (CRT-D). Aim of this study was to compare a daily remote monitoring (RM) to a standard program of in-office visits.

METHODS AND RESULTS

We retrospectively analyzed RM database and hospital files of 99 CRT-D consecutive patients who were visited in the out-patient clinic every 3-4 months; thirty-three patients were in addition controlled remotely with RM (RM group). Kaplan-Meier curves of clinical or device-related AE-free rates were obtained. During a median follow-up of 7 months, clinical AEs were: ventricular and atrial arrhythmias in 14 and 11 patients, low CRT pacing in nine, heart failure, strokes, or death in 15. Device-related AEs were: insufficient pacing/sensing performances in nine patients, lead dislodgement in five. As comparing the RM group with the remaining patients, Kaplan-Meier curves of clinical AEs diverged to significantly different rates: 23.8% (confidence interval [CI] 0.1%-47.5%) in the RM group and 48.7% (21.6-75.7%) in the remaining patients (P = 0.00002), with a hazard ratio of 0.14 (CI 0.06-0.37). Nondivergent Kaplan-Meier curves were obtained for device-related AE-free rates.

CONCLUSION

CRT-D patients followed with quarterly in-office visits without a daily RM system had an 86% higher risk of delayed detection of clinical AEs, during a median follow-up of 7 months.