REACT DX registry: Real world REACTion to atrial high rate episodes detected in implantable cardioverter-defibrillator recipients with a DX lead.

BACKGROUND: Atrial fibrillation (AF) is associated with significant morbidity and is predicted by atrial high rate events. The early detection of AF is paramount to timely interventions to reduce the morbidity of AF. The DX ICD system combined with Home Monitoring® allows for continuous atrial rhythm monitoring without the need for a dedicated atrial lead. OBJECTIVE: To establish the reaction to and timing of reactions to the detection of atrial high rate episodes (AHRE). METHODS: A prospective cohort of DX ICD systems was followed up and the response to AHREs was collected and evaluated. RESULTS: A total of 234 patients were enrolled; an AHRE ⩾ 6 min was detected in 13.7% of patients (n= 32) within a mean follow-up duration of 16 months. A high rate of oral anticoagulation (OAC) prescription was seen with the detection of AHREs in patients with a not-low risk CHA2DS2-VASc score. There was a delay in this prescription highlighting the potential to improve the timeliness of patient care in this group of patients. CONCLUSIONS: The DX ICD system provides rapid and ongoing atrial rhythm monitoring such that physicians are rapidly aware of AHRE without the need for a dedicated atrial lead, but local protocols are needed to improve the response time of anti-coagulation prescription.

Cardiac Autonomic Dysfunction and Incidence of de novo Atrial Fibrillation: Heart Rate Variability vs. Heart Rate Complexity.

BACKGROUND: The REACT DX registry evaluates standard therapies to episodes of long-lasting atrial tachyarrhythmias and assesses the quality of sensing and stability of the lead and the implantable cardioverter-defibrillator (ICD) (BIOTRONIK Lumax VR-T DX and successors) over at least a 1-year follow-up period. OBJECTIVE: To study the association between the risk of de novo device-detected atrial fibrillation (AF), the autonomic perturbations before the onset of paroxysmal AF and a 7-days heart rate variability (7dHRV) 1 month after ICD implantation. METHODS: The registry consists of 234 patients implanted with an ICD, including 10 with de novo long-lasting atrial tachyarrhythmias with no prior history of AF. The patients were matched via the propensity-score methodology as well as for properties directly influencing the ECGs recorded using GE CardioMem CM 3000. Heart rate variability (HRV) analysis was performed using standard parameters from time- and frequency-domains, and from non-linear dynamics. RESULTS: No linear HRV was associated with an increased risk of AF (p = n.s.). The only significant approach was derived from symbolic dynamics with the parameter "forbidden words" which distinguished both groups on all 7 days of measurements (p < 0.05), thereby quantifying the heart rate complexity (HRC) as drastically lower in the de novo AF group. CONCLUSION: Cardiac autonomic dysfunction denoted by low HRC may be associated with higher AF incidence. For patients with mild to moderate heart failure, standard HRV parameters are not appropriate to quantify cardiac autonomic perturbations before the onset of AF. Further studies are needed to determine the individual risk for AF that would enable interventions to restore autonomic balance in the general population.

Cost Saving Potential of an Early Detection of Atrial Fibrillation in Patients after ICD Implantation.

Atrial fibrillation (AF) is a relevant comorbidity in recipients of implantable cardioverter-defibrillators (ICD). Latest generation single-chamber ICD allow the additional sensing of atrial tachyarrhythmias and, therefore, contribute to the early detection and treatment of AF, potentially preventing AF-related stroke. The present study aimed to measure the impact on patient-related costs of this new ICD compared to conventional ICD. A Markov model was developed to simulate the long-term incidence of stroke in patients treated with a single-chamber ICD with or without atrial sensing capabilities. The median annual cost per patient and its difference, the number of strokes avoided, and the cost per stroke avoided were estimated. During a 9-year horizon, the costs for the ICD and stroke treatment were €570 per patient-year for an ICD with atrial sensing capabilities and €491 per patient-year for a conventional ICD. Per 1,000 patients, 4.6 strokes per year are assumed to be avoided by the new device. Higher CHA2DS2-VASc scores are associated with higher numbers of avoided strokes and larger potential for cost savings. Apart from clinical advantages, the use of ICD with atrial sensing capabilities may reduce the incidence of stroke and, in high-risk patients, may also contribute to reduce overall health care costs.

Feasibility of atrial sensing via a free-floating single-pass defibrillation lead for dual-chamber defibrillators.

BACKGROUND: Detection and misclassification of rapidly conducted atrial fibrillation (AF) and marked sinus tachycardia by implantable cardioverter defibrillators (ICD) can result in the delivery of inappropriate therapies. Continuous atrial sensing may improve the differentiation between supraventricular and ventricular tachycardia. The present approach is to implant a separate atrial pacing lead connected to a dual-chamber defibrillator. We hypothesized that a free-floating single-pass defibrillation lead reliably senses the atrial electrical activity. The aim of the study was to assess during implantation the efficacy of a custom-built free-floating single-pass defibrillation lead and to record sinus rhythm (SR), induced AF, and atrial flutter (Afl). METHODS: The free-floating single-pass defibrillation lead (Biotronik, Berlin, Germany) had an atrial bipole with 10 mm spacing and a distance between the atrial bipole and the electrode tip of 13.5, 15 or 17-cm. The lead was temporarily implanted in 15 patients during an ICD implantation. Fifteen seconds recordings were made during SR and after the induction of AF and Afl as well as during induced ventricular fibrillation. The amplitude and the time that the amplitude was less than 0.3 mV were assessed. RESULTS: The amplitude during SR (2.1 +/- 1.4 mV) was significantly higher compared with the amplitudes for Afl (1.3 +/- 0.5 mV; p < 0.02) and AF (0.7 +/- 0.5 mV; p < 0.001). Low amplitudes were not observed during SR and rarely during Afl (1.6 +/- 3.1%), but they were observed 19.9 +/- 15.9% of the time during AF (p < 0.05). The correlation coefficients between SR and AF amplitudes were r = 0.25, between SR and Afl amplitudes r = 0.31, and between AF and Afl amplitudes r = 0.41. During the ventricular fibrillation conversion test 9 patients were in continuous SR. The P-wave amplitude before the induction of ventricular fibrillation was 2.1 +/- 1.4 mV. The signal during ventricular fibrillation decreased to 1.1 +/- 0.7 mV and increased immediately after the termination of ventricular fibrillation to 1.6 +/- 0.8 mV. CONCLUSIONS: The recorded unfiltered signals indicate that SR as well as AF and Afl can immediately be detected after the implantation of the new free-floating single-pass defibrillation lead. High signal amplitude during SR did not predict high amplitude during AF or Afl. During induced ventricular fibrillation the P-wave amplitude decreased intermittently.