Atrial fibrillation reduces the atrial impedance amplitude during cardiac cycle: a novel detection algorithm to improve recognition of atrial fibrillation in pacemaker patients

Loop Recorder Detected High Rate of Atrial Fibrillation Recurrence after a Single Balloon- or Basket-Based Ablation of Paroxysmal Atrial Fibrillation: Results of the MACPAF Study

Purpose

Pulmonary vein isolation (PVI) is an established approach to treat symptomatic non-permanent atrial fibrillation (AF). Detecting AF recurrence after PVI is important, if discontinuation of oral anticoagulation after ablation is considered.

Methods

Patients with symptomatic paroxysmal AF were enrolled in the prospective randomized mesh ablator vs. cryoballoon pulmonary vein (PV) ablation of symptomatic paroxysmal AF study, comparing efficacy and safety of the HD Mesh Ablator^® (C.R. Bard, Lowell, MA, USA) and the Arctic Front^® (Medtronic, Minneapolis, MN, USA) catheter. Rhythm status post-PVI was closely monitored for 1 year using the implantable loop recorder (ILR) Reveal XT^® (Medtronic Minneapolis, MN, USA).

Results

The study was terminated after the first interim analysis due to the inability of the HD Mesh Ablator^® to achieve the predefined primary study endpoint, an exit block of all PVs. After a 90-day blanking period, 23 (62.2%) out of 37 study patients (median 63.0 years; 41% females) had at least one episode of AF. AF recurrence was associated with AF episodes during the blanking period {hazard ratios (HR) 5.10 [95% confidence interval (CI) 1.21–21.4]; p = 0.038}, and a common left-sided PV ostium [HR 4.17 (95%CI 1.48–11.8); p = 0.039] but not with catheter type, age, gender, cardiovascular risk profile, or left atrial volume. There was a trend toward AF recurrence in patients without complete PVI of all PV (p = 0.095). Overall, 337 (59.4%) out of 566 ILR-detected episodes represented AF. Comparing patients with AF recurrence to those without, there was no difference in cognitive performance 6 months post-ablation.

Conclusion

Using an ILR, in more than 60% of all patients with paroxysmal AF, a recurrence of AF was detected within 12 months after ablation. In patients with a common PV ostium, the first generation balloon-based catheter is obviously less effective.

Clinical trials

http://Clinicaltrials.gov NCT01061931.

Performance of an implantable automatic atrial fibrillation detection device: impact of software adjustments and relevance of manual episode analysis

AIMS

Implantable loop recorders (ILRs) with specific atrial fibrillation (AF) detection algorithms (ILR-AF) have been developed for continuous AF monitoring. We sought to analyse the clinical value of a new AF monitoring device and to compare it to serial 7-day Holter.

METHODS AND RESULTS

Sixty-four consecutive patients suffering from paroxysmal AF were included in this prospective analysis and received an ILR-AF. Manual electrogram analysis was performed for each automatically detected episode and each was categorized into one of three possible diagnoses: 'no AF', 'definite AF', and 'possible AF' (non-diagnostic). Analysis was performed separately before and after a software upgrade that was introduced during the course of the study. A subgroup of patients (51 of 64) underwent AF catheter ablation with subsequent serial 7-day Holter in comparison with the ILR-AF. A total of 333 interrogations were performed (203 before and 130 after software upgrade). The number of patients with AF misdetection was significantly reduced from 72 to 44% following the software upgrade (P = 0.001). The number of patients with non-diagnostic interrogations went from 38 to 16% (P = 0.001). Compared with serial 7-day Holter, the ILR-AF had a tendency to detect a higher number of patients with AF recurrences (31 vs. 24%; P = 0.125).

CONCLUSIONS

The rate of AF detection on ILR-AF may be higher compared with standard AF monitoring. However, false-positive AF recordings hamper the clinical value. Developments in device technology and device handling are necessary to minimize non-diagnostic interrogations.

Measuring impedance in congestive heart failure: current options and clinical applications

Measurement of impedance is becoming increasingly available in the clinical setting as a tool for assessing hemodynamics and volume status in patients with heart failure. The 2 major categories of impedance assessment are the band electrode method and the implanted device lead method. The exact sources of the impedance signal are complex and can be influenced by physiologic effects such as blood volume, fluid, and positioning. This article provides a critical review of our current understanding and promises of impedance measurements, the techniques that have evolved, as well as the evidence and limitations regarding their clinical applications in the setting of heart failure management.