Epidemiology and impact of frailty in patients with atrial fibrillation in Europe

BACKGROUND

Frailty is a medical syndrome characterised by reduced physiological reserve and increased vulnerability to stressors. Data regarding the relationship between frailty and atrial fibrillation (AF) are still inconsistent.

OBJECTIVES

We aim to perform a comprehensive evaluation of frailty in a large European cohort of AF patients.

METHODS

A 40-item frailty index (FI) was built according to the accumulation of deficits model in the AF patients enrolled in the ESC-EHRA EORP-AF General Long-Term Registry. Association of baseline characteristics, clinical management, quality of life, healthcare resources use and risk of outcomes with frailty was examined.

RESULTS

Among 10,177 patients [mean age (standard deviation) 69.0 (11.4) years, 4,103 (40.3%) females], 6,066 (59.6%) were pre-frail and 2,172 (21.3%) were frail, whereas only 1,939 (19.1%) were considered robust. Baseline thromboembolic and bleeding risks were independently associated with increasing FI. Frail patients with AF were less likely to be treated with oral anticoagulants (OACs) (odds ratio 0.70, 95% confidence interval 0.55-0.89), especially with non-vitamin K antagonist OACs and managed with a rhythm control strategy, compared with robust patients. Increasing frailty was associated with a higher risk for all outcomes examined, with a non-linear exponential relationship. The use of OAC was associated with a lower risk of outcomes, except in patients with very/extremely high frailty.

CONCLUSIONS

In this large cohort of AF patients, there was a high burden of frailty, influencing clinical management and risk of adverse outcomes. The clinical benefit of OAC is maintained in patients with high frailty, but not in very high/extremely frail ones.

Left atrial anatomical variations correlate with atrial fibrillation sources near the left atrial ridge

Funding Acknowledgements

Type of funding sources: None.

Background

Anatomical variations and characteristics of the left atrium (LA) may have a previously undescribed effect on source locations in atrial fibrillation (AF). Electrographic flow (EGF) mapping is a novel method used to estimate cardiac action potential flow in the atria that can detect AF sources in patients with persistent AF. The EGF technology offers a revolutionary mapping possibility for AF, however, it is not commercially available yet.

Purpose

This is the first study aiming to investigate the relationship between anatomical characteristics of the LA and non-PV sources detected by EGF in patients with persistent AF.

Methods

We collected cardiac computed tomography (CT) and EGF data from patients who underwent radiofrequency catheter ablation (CA) for persistent AF. EGF mapping creates a spatial and temporal reconstruction of electric potentials derived from endocardial unipolar electrograms. By analyzing EGF maps obtained during CA procedures, we localized non-PV sources in the LA. Patients with individual stable sources with a source activity above threshold (leading source present in more than > 26% of the time) were classified as having an S-Type EGF signature with source-dependent AF. Patients with no stable active source pattern and no leading source with a source activity above threshold were characterized as having a C-Type EGF signature consistent with source-independent AF. We assessed LA anatomical characteristics including size, LAA length, LAA ostial diameter, trajectory of the left superior pulmonary vein (LSPV) and its relation to the LAA on cardiac CT scans. Abutting LAA-LSPV was defined as cases when the LSPV touched the posterior aspect of LAA, and the maximal distance between the two structures was less than 2 mm. Those cases where the distance between LAA and LSPV was more than 2 mm were defined as non-abutting LAA-LSPV.

Results

Thirty patients were included in this study (mean age 62.4±6.8 years):23 patients had an S-Type EGF signature (77%), and 7 patients had a C-Type EGF signature (23%). We identified 10 patients with AF sources near the LA ridge, while twenty patients had no leading source near the LA ridge. LA anatomical characteristics, LAA length and ostial diameter showed no correlation with the presence of a leading source near the ridge. We described 19 patients with abutting LAA-LSPV, and 11 patients with non-abutting LAA-LSPV. Three out of 19 patients presented with a leading source near ridge in the abutting LAA-LSPV group, while 7 out of 11 patients presented with a leading source near ridge in the non-abutting LAA-LSPV group (p=0.01).

Conclusion

Our data suggests that non-abutting LAA-LSPV is associated with the presence of AF sources near the LA ridge.

First human experience with catheter ablation using dipole charge density mapping integrated in robotics in the management of atrial fibrillation

Funding Acknowledgements

Type of funding sources: None.

Background

Remote magnetic navigation (RMN) guided catheter ablation (CA) previously demonstrated high efficiency and efficacy in atrial fibrillation (AF) ablation. Heretofore, only the CARTO 3D mapping system was integrated in the RMN system. Recently, a novel high-resolution non-contact mapping system (AcQMap) can be used in combination with the RMN robotic system (AcQMap-RMN).

Purpose

To assess efficiency, efficacy and safety of dipole charge density mapping in RMN guided ablation procedures for AF.

Methods

All patients undergoing pulmonary vein isolation (PVI) or redo-PVI using the AcQMap-RMN system were analyzed. The AcQMap identifies different activation patterns such as focal firing, rotational activity, and localized irregular activation for substrate ablation. Procedural efficiency was characterized by procedure time, total ablation time and radiation doses. Efficacy data were based on 12-month follow up and number of redo procedures. Procedural safety was evaluated by intra- and post-procedural complications.

Results

A number of 71 consecutive patients were included in the study (47 male, 24 female, mean age 60.8±9.9, 49 redo, 22 de novo). Twenty-four patients had paroxysmal (PAF), 47 had persistent AF (persAF). After completing PVI, 42 patients underwent AcQMap based substrate ablation. Twenty-four patients converted to atrial tachycardia/flutter during the ablation. The mean procedure time was 170.5±43.3 min, mean ablation time 1749.6±950.7 s, mean radiation dose was 207.0 (IQR 128.5 - 349.5) mGy. In the PAF group, radiation doses (128.5 vs 256.0 mGy, p=0.00) and application numbers (21.1 vs 37.0, p=0.00) were lower, ablation times were shorter (1312.5 vs 1919.3 s, p=0.02) compared to the persAF patient group. Two patients in the PAF group, and 9 patients in the persAF group had documented recurrence at the 6-month follow-up visits. In the PAF group, 23 patients were AF-free (95.8%), in the persAF group, 34 patients were AF-free at the end of the 12-month follow-up period (72.3%). Six patients had a redo procedure. Two patients were documented with hematoma, as minor post-procedural complication (2.8%).

Conclusion

AcQMap-RMN integration provides high acute and long-term success rates, improved efficiency and low complication rates in paroxysmal and persistent AF ablation.

Novel cryoballoon to isolate pulmonary veins in patients with paroxysmal atrial fibrillation: one-year outcomes in a multicenter study

Background

Recently, a novel cryoballoon (CB; POLARx) has been developed with increased steerability which maintains size and pressure throughout the ablation. Initial clinical data has demonstrated acute procedural safety and efficacy in de novo pulmonary vein isolation (PVI) procedures in patients with paroxysmal atrial fibrillation (AF). However, there are limited studies demonstrating the long-term efficacy of the CB.

Purpose

To evaluate the long-term safety and efficacy of the novel CB in treating paroxysmal AF.

Methods

This was a non-randomized, prospective, multi-center study. Fifty-eight consecutive patients with paroxysmal AF were enrolled at 4 centers for de novo PVI procedures. Cryoablation was delivered for 180s if time to isolation was ≤60s. Otherwise a 240s cryoablation was performed. PVI was confirmed with entrance and exit block testing. Patients were followed for 1 year with 24-hour Holter monitoring at 3, 6, and 12 months. After a 3-month blanking period, recurrence was defined as having any documented, symptomatic episode(s) of AF or atrial tachycardia.

Results

Acute isolation with the CB was achieved in 230 of 231 pulmonary veins (99.6%) with 5.2±1.5 cryoapplications per patient (1.3±0.6 cryoapplications per vein). There were 4 patients (6.9%) with phrenic nerve injury (3 resolved during the index procedure; 1 resolved at 6 months follow-up). One serious adverse device event was reported: femoral arterial embolism event occurring 2 weeks post index procedure (1.7%). Of the 56 patients that had complete 12-month follow-up, 43 (76.8%) were free from recurrent atrial arrhythmias.

Conclusion

Initial multicenter clinical experience with the novel CB has demonstrated long-term safety and efficacy of PVI in patients with paroxysmal AF. Further studies are underway to confirm these findings.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Boston Scientific

Contemporary management of patients with atrial fibrillation in the Netherlands and Belgium: a report from the EORP-AF long-term general registry

BACKGROUND

Contemporary data regarding the characteristics, treatment and outcomes of patients with atrial fibrillation (AF) are needed. We aimed to assess these data and guideline adherence in the EURObservational Research Programme on Atrial Fibrillation (EORP-AF) long-term general registry.

METHODS

We analysed 967 patients from the EORP-AF long-term general registry included in the Netherlands and Belgium from 2013 to 2016. Baseline and 1‑year follow-up data were gathered.

RESULTS

At baseline, 887 patients (92%) received anticoagulant treatment. In 88 (10%) of these patients, no indication for chronic anticoagulant treatment was present. A rhythm intervention was performed or planned in 52 of these patients, meaning that the remaining 36 (41%) were anticoagulated without indication. Forty patients were not anticoagulated, even though they had an indication for chronic anticoagulation. Additionally, 63 of the 371 patients (17%) treated with a non-vitamin K antagonist oral anticoagulant (NOAC) were incorrectly dosed. In total, 50 patients (5%) were overtreated and 89 patients (9%) were undertreated. However, the occurrence of major adverse cardiac and cerebrovascular events (MACCE) was still low with 4.2% (37 patients).

CONCLUSIONS

Overtreatment and undertreatment with anticoagulants are still observable in 14% of this contemporary, West-European AF population. Still, MACCE occurred in only 4% of the patients after 1 year of follow-up.

"Edge Effect" of (32)p radioactive stents is caused by the combination of chronic stent injury and radioactive dose falloff

BACKGROUND

Radioactive stents have been reported to reduce in-stent neointimal thickening. An unexpected increase in neointimal response was observed, however, at the stent-to-artery transitions, the so-called "edge effect." To investigate the factors involved in this edge effect, we studied stents with 1 radioactive half and 1 regular nonradioactive half, thereby creating a midstent radioactive dose-falloff zone next to a nonradioactive stent-artery transition at one side and a radioactive stent-artery transition at the other side.

METHODS AND RESULTS

Half-radioactive stents (n=20) and nonradioactive control stents (n=10) were implanted in the coronary arteries of Yucatan micropigs. Animals received aspirin and clopidogrel as antithrombotics. After 4 weeks, a significant midstent stenosis was observed by angiography in the half-radioactive stents. Two animals died suddenly because of coronary occlusion at this mid zone at 8 and 10 weeks. At 12-week follow-up angiography, intravascular ultrasound and histomorphometry showed a significant neointimal thickening at the midstent dose-falloff zone of the half-radioactive stents, but not at the stent-to-artery transitions at both extremities. Such a midstent response (mean angiographic late loss 1.0 mm) was not observed in the nonradioactive stents (mean loss 0.4 to 0.6 mm; P< 0.01).

CONCLUSIONS

The edge effect of high-dose radioactive stents in porcine coronary arteries is associated with the combination of stent injury and radioactive dose falloff.

The computation of MR image distortions caused by tissue susceptibility using the boundary element method

Static field inhomogeneity in magnetic resonance (MR) imaging produces geometrical distortions which restrict the clinical applicability of MR images, e.g., for planning of precision radiotherapy. The authors describe a method to compute distortions which are caused by the difference in magnetic susceptibility between the scanned object and the surrounding air. Such a method is useful for understanding how the distortions depend on the object geometry, and for correcting for geometrical distortions, and thereby improving MR/CT registration algorithms. The geometric distortions in MR can be directly computed from the magnetic field inhomogeneity and the applied gradients. The boundary value problem of computing the magnetic field inhomogeneity caused by susceptibility differences is analyzed. It is shown that the boundary element method (BEM) has several advantages over previously applied methods to compute the magnetic field. Starting from the BEM and the assumption that the susceptibilities are very small (typically O(10(-5)) or less), a formula is derived to compute the magnetic field directly, without the need to solve a large system of equations. The method is computationally very efficient when the magnetic field is needed at a limited number of points, e.g., to compute geometrical distortions of a set of markers or a single surface. In addition to its computational advantage the method proves to be efficient to correct for the lack of data outside the scan which normally causes large artifacts in the computed magnetic field. These artifacts can be reduced by assuming that at the scan boundary the object extends to infinity in the form of a generalized cylinder. With the adaptation of the BEM this assumption is equivalent to simply omitting the scan boundary from the computations. To the authors' knowledge, no such simple correction method exists for other computation methods. The accuracy of the algorithm was tested by comparing the BEM solution with the analytical solution for a sphere. When the applied homogeneous field is 1.5 T the agreement between both methods was within 0.11.10(-6) T. As an example, the method was applied to compute the displacement vector field of the surface of a human head, derived from an MR imaging data set. This example demonstrates that the distortions can be as large as 3 mm for points just outside the head when a gradient strength of 3 mT/m is used. It was also observed that distortion within the head can be described accurately as a linear scaling in the axial direction.

Analysis and correction of geometric distortions in 1.5 T magnetic resonance images for use in radiotherapy treatment planning

The aim of this study is to investigate and correct for machine- and object-related distortions in magnetic resonance images for use in radiotherapy treatment planning. Patients with brain tumours underwent magnetic resonance imaging (MRI) in the radiotherapy position with the head fixed by a plastic cast in a Perspex localization frame. The imaging experiments were performed on a 1.5 T whole body MRI scanner with 3 mT m-1 maximum gradient capability. Image distortions, caused by static magnetic field inhomogeneity, were studied by varying the direction of the read-out gradient. For purposes of accuracy assessment, external and internal landmarks were indicated. Tubes attached to the cast and in the localization frame served as external landmarks. In the midsagittal plane the brain-sinus sphenoidalis interface, the pituitary gland-sinus sphenoidalis interface, the sphenoid bone and the corpora of the cervical vertebra served as internal landmarks. Landmark displacements as observed in the reversed read-out gradient experiments were analysed with respect to the contributions of machine-related static magnetic field inhomogeneity and susceptibility and chemical shift artifacts. The machine-related static magnetic field inhomogeneity in the midsagittal plane was determined from measurements on a grid phantom. Distortions due to chemical shift effects were estimated for bone marrow containing structures such as the sphenoid bone and the corpora of the cervical vertebra using the values obtained from the literature. Susceptibility-induced magnetic field perturbations are caused by the patient and the localization frame. Magnetic field perturbations were calculated for a typical patient dataset.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of respiration induced motion of the kidneys on the accuracy of radiotherapy treatment planning, a magnetic resonance imaging study

An MRI study has been performed to determine the respiration induced motion of the kidneys. Under normal respiration conditions displacements of the left and right kidney varied from 2 to 24 mm and 4 to 35 mm, respectively. Under forced respiration conditions displacements were larger and ranged from 10 to 66 mm for the left kidney and 10 to 86 mm for the right kidney. The influence of kidney motion on the radiation dose was determined for patients irradiated on the total abdomen for ovarian cancer with shielding of the kidneys during part of the treatment. The kidney motion resulted in a larger fraction of the kidney volume receiving a dose between 20 and 22 Gy.

Simulation of susceptibility artifacts in 2D and 3D Fourier transform spin-echo and gradient-echo magnetic resonance imaging

A method is presented for simulating susceptibility artifacts in 2D and 3D spin-echo and gradient-echo imaging of arbitrary susceptibility distributions. The method incorporates object induced field perturbations in the time domain (k-space) and is demonstrated for spherical nonuniformities in susceptibility. Both simulations and experimental results for multi-slice 2D and 3D imaging of phantoms and human subjects are provided.

Numerical analysis of the magnetic field for arbitrary magnetic susceptibility distributions in 3D

This paper demonstrates a method to calculate the magnetic field distribution in and around a 3D object when it is magnetized by a strong homogeneous magnetic field. The numerical technique is based on the explicit finite difference method. The calculation method is validated against analytical solutions for a sphere. As an application cylinders with different ratios of lengths and diameter are studied.

Susceptibility artifacts in 2DFT spin-echo and gradient-echo imaging: the cylinder model revisited

Susceptibility-induced geometry and intensity distortions are a familiar observation in MR imaging. In the past few years several attempts have been made to aid in the understanding of susceptibility artifacts by means of simulation studies. Although these studies, which were mostly carried out with simple test objects, have produced some qualitative insight into chi-artifacts, the results lacked precision in describing finer details. In this paper we show the discrepancy between theory and experiment in previous work to be the result of an inadequate theoretical approach. In most studies so far, delta B0 effects are taken into account in the frequency domain, that is, after Fourier transformation of the data. In our view the simulation should follow the actual sequence of events in an imaging experiment and deal with the effect of error fields in the time domain (k-space) already. The correctness of this view is demonstrated here by comparing the results of time and frequency domain simulation against experimental observation for a coaxial cylinder phantom, a widely used model in this type of work. Having established the superiority of the time domain simulation, we demonstrate its use in predicting chi-artifacts under various experimental conditions, for example, in spin-echo and gradient-echo imaging with a reduced number of phase-encoding steps.

Numerical analysis of the magnetic field for arbitrary magnetic susceptibility distributions in 2D

We describe a numerical technique for calculating the 2D magnetic field in arbitrary magnetic susceptibility distribution. The technique we used is the explicit finite difference method with an addition of the Du Fort-Frankle algorithm. The proposed algorithm is unconditionally stable and has excellent convergence properties. For simple geometries, numerical results were compared against analytical solutions and appeared to be in excellent agreement.

Analysis of machine-dependent and object-induced geometric distortion in 2DFT MR imaging

Geometric distortion in MR imaging predominantly arises from the inhomogeneity of the static field and the nonlinearity of the gradients. It is the purpose of this paper to analyse the object and machine related contributions to geometric distortion in order to determine which corrections are necessary for attaining a specified precision. System related imperfections were measured by systematic variation of the strength, direction, and polarity of the read-out gradient in imaging experiments on a grid of cylindrical sample tubes. For the 1.5-T system used in this study, static field related errors up to 7 mm and gradient related errors up to 4 mm were observed (midcoronal plane, FOV 400-mm, G-read between 0.5 and 3.0 mT/m). Field related errors were shown to be inversely proportional to gradient strength, whereas gradient related errors turned out to be virtually independent of gradient strength. It therefore seems recommendable to always apply the strongest available selection and read-out gradients when geometric fidelity is given preference to signal-to-noise considerations. Correction of system related geometric distortions in MR images can readily be performed by table lookup. Object-induced distortions of the gradient fields were studied by experiments on a grid of sample tubes immersed into a cylindrical water bath of variable saline concentration. These experiments revealed a negligible influence of the object on the gradient error distribution, and lead to the conclusion that correction for the nonlinearity of the gradients only requires the application of system dependent correction factors. Object-related distortions of B0 were studied by conventional SE and fat-suppressed IR experiments on phantoms and human subjects. In these experiments the polarity of the read-out gradient was reversed. Subtraction images showed significant object-induced inhomogeneities of the static field at tissue-air interfaces and in the immediate vicinity of the object being imaged. A first attempt to correct for object related B0 inhomogeneities was made by contour analysis of the source images. At present this correction still has to be done manually.