Esra Gucuk Ipek

Lack of regional association between atrial late gadolinium enhancement on cardiac magnetic resonance and atrial fibrillation rotors

BACKGROUND The extent of left atrial (LA) late gadolinium enhancement (LGE), as a surrogate for fibrosis, has been associated with atrial fibrillation (AF) recurrence after catheter ablation. Furthermore, there is ex vivo evidence that islands of fibrosis may anchor fibrillatory rotors. OBJECTIVE The purpose of this study was to examine the anatomical association of AF rotors with LA and right atrial (RA) LGE on cardiac magnetic resonance. METHODS The cohort included 9 patients with persistent AF (mean age 61.1 ± 9.7 years) who underwent LGE cardiac magnetic resonance before AF ablation using the focal impulse and rotor modulation system. The extent of LA and RA LGE was quantified globally and in each of the 7 sectors: LA posterior/inferior wall, anterior wall, roof, left and right pulmonary vein antra, and RA lateral and septal regions. The multivariable association of rotor incidence with global and per sector LGE extent was examined using multivariable Bernoulli logistic regression estimated by generalized estimating equations. RESULTS The mean RA and LA volumes were 113.2 ± 37.31 and 143.03 ± 58.25 mL, respectively. The mean RA and LA LGE burden was 17.2% ± 11.0% and 17.4% ± 14.4%, respectively. A total of 18 LA rotors and 9 RA rotors were identified in all patients. No univariable or multivariable association was observed between global or per sector LGE extent and focal impulse and rotor modulation rotor incidence. CONCLUSION In this cohort of patients, there was no association between AF rotor incidence and the global or regional extent of RA and LA LGE.

Safety of Magnetic Resonance Imaging in Patients with Cardiac Devices

Background Patients who have pacemakers or defibrillators are often denied the opportunity to undergo magnetic resonance imaging (MRI) because of safety concerns, unless the devices meet certain criteria specified by the Food and Drug Administration (termed “MRI‐conditional” devices). Methods We performed a prospective, nonrandomized study to assess the safety of MRI at a magnetic field strength of 1.5 Tesla in 1509 patients who had a pacemaker (58%) or an implantable cardioverter–defibrillator (42%) that was not considered to be MRI‐conditional (termed a “legacy” device). Overall, the patients underwent 2103 thoracic and nonthoracic MRI examinations that were deemed to be clinically necessary. The pacing mode was changed to asynchronous mode for pacing‐dependent patients and to demand mode for other patients. Tachyarrhythmia functions were disabled. Outcome assessments included adverse events and changes in the variables that indicate lead and generator function and interaction with surrounding tissue (device parameters). Results No long‐term clinically significant adverse events were reported. In nine MRI examinations (0.4%; 95% confidence interval, 0.2 to 0.7), the patients device reset to a backup mode. The reset was transient in eight of the nine examinations. In one case, a pacemaker with less than 1 month left of battery life reset to ventricular inhibited pacing and could not be reprogrammed; the device was subsequently replaced. The most common notable change in device parameters (>50% change from baseline) immediately after MRI was a decrease in P‐wave amplitude, which occurred in 1% of the patients. At long‐term follow‐up (results of which were available for 63% of the patients), the most common notable changes from baseline were decreases in P‐wave amplitude (in 4% of the patients), increases in atrial capture threshold (4%), increases in right ventricular capture threshold (4%), and increases in left ventricular capture threshold (3%). The observed changes in lead parameters were not clinically significant and did not require device revision or reprogramming. Conclusions We evaluated the safety of MRI, performed with the use of a prespecified safety protocol, in 1509 patients who had a legacy pacemaker or a legacy implantable cardioverter–defibrillator system. No long‐term clinically significant adverse events were reported. (Funded by Johns Hopkins University and the National Institutes of Health; ClinicalTrials.gov number, NCT01130896.)

Factors impacting complication rates for catheter ablation of atrial fibrillation from 2003 to 2015

Aims Complications from catheter ablation for atrial fibrillation (AF) are well described. Changing aspects of AF ablation including patient populations referred, institutional experience, and emerging catheter and pharmacological options may impact complication rates. We assessed procedural complication trends in AF ablation patients from 2003‐2015 to identify what factors affect adverse event rates. Methods and results We evaluated consecutively enrolled patients undergoing initial AF ablation from 2003 through 2015. Statistical analyses were performed to identify predictors of increased risk for major complications, which were defined as death, stroke, atrio‐oesophageal fistula, phrenic nerve injury, cardiovascular events requiring blood transfusions or procedural interventions, or non‐cardiovascular events requiring intervention. A total of 1475 patients (mean age 59.5 ± 10.5, 82% male) were evaluated. Major complications occurred in 3.9% (n = 58) of cases, including vascular access‐site haematoma (1.3%), cardiac tamponade (1.1%), and cerebrovascular accident (CVA) (0.9%). Univariate analysis revealed increased risk of complications associated with hypertension (P = 0.048), CHA2DS2VASc score ≥1 (P = 0.015), and early institutional experience (P = 0.003). Populations with higher CHA2DS2VASc scores underwent AF ablation more frequently over time (P < 0.001). Novel catheters and anticoagulants did not appreciably affect complication rates. Multivariate analysis adjusting for hypertension, CHA2DS2VASc score, and institutional experience showed that higher CHA2DS2VASc score and early institutional experience were independent predictors of adverse events. Conclusion Patient characteristics reflected in CHA2DS2VASc scoring and early institutional experience predict increased complication rates following AF ablation. Despite more patients with higher CHA2DS2VASc scores undergoing AF ablation, complication rates fell over time as institutional experience increased.

Association of Left Atrial Local Conduction Velocity With Late Gadolinium Enhancement on Cardiac Magnetic Resonance in Patients With Atrial Fibrillation

Background—Prior studies have demonstrated regional left atrial late gadolinium enhancement (LGE) heterogeneity on magnetic resonance imaging. Heterogeneity in regional conduction velocities is a critical substrate for functional reentry. We sought to examine the association between left atrial conduction velocity and LGE in patients with atrial fibrillation. Methods and Results—LGE imaging and left atrial activation mapping were performed during sinus rhythm in 22 patients before pulmonary vein isolation. The locations of 1468 electroanatomic map points were registered to the corresponding anatomic sites on 469 axial LGE image planes. The local conduction velocity at each point was calculated using previously established methods. The myocardial wall thickness and image intensity ratio defined as left atrial myocardial LGE signal intensity divided by the mean left atrial blood pool intensity was calculated for each mapping site. The local conduction velocity and image intensity ratio in the left atrium (mean±SD) were 0.98±0.46 and 0.95±0.26 m/s, respectively. In multivariable regression analysis, clustered by patient, and adjusting for left atrial wall thickness, conduction velocity was associated with the local image intensity ratio (0.20 m/s decrease in conduction velocity per increase in unit image intensity ratio, P<0.001). Conclusions—In this clinical in vivo study, we demonstrate that left atrial myocardium with increased gadolinium uptake has lower local conduction velocity. Identification of such regions may facilitate the targeting of the substrate for reentrant arrhythmias.

Fully automatic segmentation of left atrium and pulmonary veins in late gadolinium‐enhanced MRI: Towards objective atrial scar assessment

To realize objective atrial scar assessment, this study aimed to develop a fully automatic method to segment the left atrium (LA) and pulmonary veins (PV) from late gadolinium‐enhanced (LGE) magnetic resonance imaging (MRI). The extent and distribution of atrial scar, visualized by LGE‐MRI, provides important information for clinical treatment of atrial fibrillation (AF) patients.

Comparison of preexisting and ablation-induced late gadolinium enhancement on left atrial magnetic resonance imaging

BACKGROUND Postablation atrial fibrillation recurrence is positively associated with the extent of preexisting left atrial (LA) late gadolinium enhancement (LGE) on magnetic resonance imaging (MRI), but negatively associated with the extent of postablation LGE regardless of proximity to the pulmonary vein antra. The characteristics of pre- vs postablation LA LGE may provide insight into this seeming paradox and inform future strategies for ablation. OBJECTIVE The purpose of this study was to define the characteristics of preexisting vs ablation-induced LA LGE. METHODS LGE-MRI was prospectively performed before and ≥3 months after initial ablation in 20 patients. The intracardiac locations of ablation points were coregistered with the corresponding sites on axial planes of postablation LGE-MRI. The image intensity ratio (IIR), defined as the LA myocardial MRI signal intensity divided by the mean LA blood pool intensity, and LA myocardial wall thickness were calculated on pre- and postablation images. RESULTS Imaging data from 409 pairs of pre- and postablation axial LGE-MRI planes and 6961 pairs of pre- and postablation image sectors were analyzed. Ablation-induced LGE revealed a higher IIR, suggesting greater contrast uptake and denser fibrosis, than did preexisting LGE (1.25 ± 0.25 vs 1.14 ± 0.15; P < .001). In addition, ablation-induced LGE regions had thinner LA myocardium (2.10 ± 0.67 mm vs 2.37 ± 0.74 mm; P < .001). CONCLUSION Regions with ablation-induced LGE exhibit increased contrast uptake, likely signifying higher scar density, and thinner myocardium as compared with regions with preexisting LGE. Future studies examining the association of postablation LGE intensity and nonuniformity with ablation success are warranted and may inform strategies to optimize ablation outcome.

Association of left atrial epicardial adipose tissue with electrogram bipolar voltage and fractionation: Electrophysiologic substrates for atrial fibrillation.

BACKGROUND Epicardial adipose tissue (EAdT) is metabolically active and likely contributes to atrial fibrillation (AF) through the release of inflammatory cytokines into the myocardium or through its rich innervation with ganglionated plexi at the pulmonary vein ostia. The electrophysiologic mechanisms underlying the association between EAdT and AF remain unclear. OBJECTIVE The purpose of this study was to investigate the association of EAdT with adjacent myocardial substrate. METHODS Thirty consecutive patients who underwent cardiac computed tomography as well as electroanatomic mapping in sinus rhythm before an initial AF ablation procedure were studied. Semiautomatic segmentation of atrial EAdT was performed and registered anatomically to the voltage map. RESULTS In multivariable regression analysis clustered by patient, age (-0.01 per year) and EAdT (-0.29) were associated with log bipolar voltage as well as low-voltage zones (<0.5 mV). Age (odds ratio [OR]: 1.02 per year), male gender (OR: 3.50), diabetes (OR: 2.91), hypertension (OR: 2.55), and EAdT (OR: 8.56) were associated with fractionated electrograms, and age (OR: 2.80), male gender (OR: 3.00), and EAdT (OR: 7.03) were associated with widened signals. Age (OR: 1.03 per year) and body mass index (OR: 1.06 per kg/m2) were associated with atrial fat. CONCLUSION The presence of overlaying EAdT was associated with lower bipolar voltage and electrogram fractionation as electrophysiologic substrates for AF. EAdT was not a statistical mediator of the association between clinical variables and AF substrate. Body mass index was directly associated with the presence of EAdT in patients with AF.

The association of baseline left atrial structure and function measured with cardiac magnetic resonance and pulmonary vein isolation outcome in patients with drug-refractory atrial fibrillation

BACKGROUND Prognostic significance of left atrial (LA) function in patients with atrial fibrillation (AF) is poorly defined. OBJECTIVE To examine the association of LA function measured with cardiac magnetic resonance (CMR) feature-tracking and AF recurrence following catheter ablation. METHODS One hundred and twenty-one AF patients (72% paroxysmal, mean age 59 ± 10 years) were enrolled. Baseline LA function was measured by calculating passive, active, and total emptying fractions (LAEF) and analysis of global longitudinal strain and strain rates. Patients were followed up for recurrence of AF or atrial tachycardia (AT). Hazard ratios for recurrence were calculated using Cox proportional models adjusted for potential clinical confounders, type of AF, left ventricular ejection fraction, AF duration, LA volume, and late gadolinium enhancement (LGE). RESULTS During a mean follow-up of 18 ± 9 months, 52 patients (43%) experienced recurrent AF/AT. Patients with recurrent AF/AT had higher baseline LA volume index and lower LA passive, and total LAEF (P < .05 for all). The baseline peak LA strain and strain rates in all phases of LA function were lower in the AF/AT recurrence group (P < .01 for all). In multivariable analysis total LAEF, peak LA strain, and systolic and late diastolic strain rates were associated with recurrence. Both peak LA strain and total LAEF improved prediction of recurrent AT/AF compared to the baseline clinical model, including LA LGE (C statistic 0.82 vs 0.77, P < .05 for both total LAEF and peak LA strain). CONCLUSIONS LA reservoir function was independently associated with recurrent AF/AT after PVI and can additionally improve risk stratification in patients undergoing PVI.

Clinical predictors of cardiac magnetic resonance late gadolinium enhancement in patients with atrial fibrillation

Aims This study aims to examine the association of clinical co-morbidities with the presence of left atrial (LA) late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR). Previous studies have established the severity of LA LGE to be associated with atrial fibrillation (AF) recurrence following AF ablation. We sought to determine whether baseline clinical characteristics were associated with LGE extent among patients presenting for an initial AF ablation. Methods and results The cohort consisted of 179 consecutive patients with no prior cardiac ablation procedures who underwent pre-procedure LGE-CMR. The extent of LA LGE for each patient was calculated using the image intensity ratio, normalized to the mean blood pool intensity, corresponding to a bipolar voltage ≤0.3 mV. The association of LGE extent with baseline clinical characteristics was examined using non-parametric and multivariable models. The mean age of the cohort was 60.9 ± 9.6 years and 128 (72%) were male. In total, 56 (31%) patients had persistent AF. The mean LA volume was 118.4 ± 41.6 mL, and the mean LA LGE extent was 14.1 ± 10.4%. There was no association with any clinical variables with LGE extent by quartiles in the multivariable model. Extent of LGE as a continuous variable was positively, but weakly associated with LA volume in a multivariable model adjusting for age, body mass index, AF persistence, and left ventricular ejection fraction (1.5% scar/mL, P = 0.038). Conclusion In a cohort of patients presenting for initial AF ablation, the presence of pre-ablation LA LGE extent was weakly, but positively associated with increasing LA volume.

Safety of Implanted Cardiac Devices in an MRI Environment

Magnetic resonance imaging (MRI) has evolved into an essential diagnostic modality for the evaluation of various conditions. In line with the increase in MRI applications, the use of cardiac implantable electronic devices (CIED) is growing and many of the CEID recipients of today may require MRI examinations in the future. Traditionally, MRI examination of CIED recipients has been considered a contraindication. However, recent studies have provided strong evidence that MRI can safely be performed in selected patients with specific precautions. This review highlights the interactions of MRI with CIEDs, summarizes the literature, and outlines the Johns Hopkins Safety Protocol.