A total of 1509 patients who had legacy pacemakers or defibrillators underwent 2103 MRIs according to a prespecified safety protocol. No long-term clinically significant adverse events were reported.
Aims
Recent studies have shown that several genetic variants near the PITX2 locus on chromosome 4q25 are associated with atrial fibrillation (AF). However, the mechanism that mediates this ...association remains unclear. Basic murine studies suggest that reduced PITX2 expression is associated with left atrial dilatation. We sought to examine the association between single nucleotide polymorphisms (SNPs) near PITX2 and left atrial size in patients with AF.
Methods
We prospectively enrolled 96 consecutive patients (mean age 60 ± 10 years, 72% male) with drug-resistant AF (57% paroxysmal, 38% persistent, and 5% long-standing persistent) who underwent catheter ablation. Following DNA extraction from blood obtained pre-operatively, SNPs rs10033464 and rs2200733 were genotyped using the Sequenom MassARRAY. Left atrial volume (LAV) was determined using three-dimensional imaging (CT or MRI prior to first ablation) and by investigators blinded to genotype results.
Results
The minor allele frequencies at SNPs rs10033464 and rs2200733 were 0.14 and 0.25, respectively. Using multivariable linear regression, homozygosity for the minor allele at rs10033464 (recessive model) was independently associated with larger LAV (P = 0.002) after adjustment for age, gender, BMI, height, type, and duration of AF, left ventricular ejection fraction, history of hypertension, valve disease, and antiarrhythmic drug use. The strength of the association was reconfirmed in a bootstrap study with 1000 resamplings. In contrast, no association was found between rs2200733 variant alleles and LAV.
Conclusion
SNP rs10033464 near the PITX2 locus on 4q25 is associated with LAV. Left atrial dilatation may mediate the association of common variants at 4q25 with AF.
Magnetic resonance imaging (MRI) is avoided in most patients with implanted cardiac devices because of safety concerns.
To define the safety of a protocol for MRI at the commonly used magnetic ...strength of 1.5 T in patients with implanted cardiac devices.
Prospective nonrandomized trial. (ClinicalTrials.gov registration number: NCT01130896) SETTING: One center in the United States (94% of examinations) and one in Israel.
438 patients with devices (54% with pacemakers and 46% with defibrillators) who underwent 555 MRI studies.
Pacing mode was changed to asynchronous for pacemaker-dependent patients and to demand for others. Tachyarrhythmia functions were disabled. Blood pressure, electrocardiography, oximetry, and symptoms were monitored by a nurse with experience in cardiac life support and device programming who had immediate backup from an electrophysiologist.
Activation or inhibition of pacing, symptoms, and device variables.
In 3 patients (0.7% 95% CI, 0% to 1.5%), the device reverted to a transient back-up programming mode without long-term effects. Right ventricular (RV) sensing (median change, 0 mV interquartile range {IQR}, -0.7 to 0 V) and atrial and right and left ventricular lead impedances (median change, -2 Ω IQR, -13 to 0 Ω, -4 Ω IQR, -16 to 0 Ω, and -11 Ω IQR, -40 to 0 Ω, respectively) were reduced immediately after MRI. At long-term follow-up (61% of patients), decreased RV sensing (median, 0 mV, IQR, -1.1 to 0.3 mV), decreased RV lead impedance (median, -3 Ω, IQR, -29 to 15 Ω), increased RV capture threshold (median, 0 V, IQR, 0 to 0.2 Ω), and decreased battery voltage (median, -0.01 V, IQR, -0.04 to 0 V) were noted. The observed changes did not require device revision or reprogramming.
Not all available cardiac devices have been tested. Long-term in-person or telephone follow-up was unavailable in 43 patients (10%), and some data were missing. Those with missing long-term capture threshold data had higher baseline right atrial and right ventricular capture thresholds and were more likely to have undergone thoracic imaging. Defibrillation threshold testing and random assignment to a control group were not performed.
With appropriate precautions, MRI can be done safely in patients with selected cardiac devices. Because changes in device variables and programming may occur, electrophysiologic monitoring during MRI is essential.
The purpose of this study was to demonstrate that mechanical and electrical activation can be quantified in patients with CRT devices combining cardiovascular magnetic resonance (CMR) and electrical ...myocardial imaging (EMI). Purpose Non-invasively characterize mechanical and electrical activation patterns in patients undergoing cardiac resynchronization therapy (CRT) Methods Patients implanted with biventricular CRT for greater than 9 months (N=10) were mapped with 120 body surface electrodes during both intrinsic activation (device off) and CRT pacing.
Studies have shown that magnetic resonance imaging (MRI) does not have clinically important effects on the device parameters of non-MRI-conditional implantable cardioverter-defibrillators (ICDs). ...However, data on non-MRI-conditional ICD detection and treatment of arrhythmias after MRI are limited.
To examine if non-MRI-conditional ICDs have preserved shock function of arrhythmias after MRI.
Prospective cohort study. (ClinicalTrials.gov: NCT01130896).
1 center in the United States.
629 patients with non-MRI-conditional ICDs enrolled consecutively between February 2003 and January 2015.
813 total MRI examinations at a magnetic field strength of 1.5 Tesla using a prespecified safety protocol.
Implantable cardioverter-defibrillator interrogations were collected after MRI. Clinical outcomes included arrhythmia detection and treatment, generator or lead exchanges, adverse events, and death.
During a median follow-up of 2.2 years from MRI to latest available ICD interrogation before generator or lead exchange in 536 patients, 4177 arrhythmia episodes were detected, and 97 patients received ICD shocks. Sixty-one patients (10% of total) had 130 spontaneous ventricular tachycardia or fibrillation events terminated by ICD shocks. A total of 210 patients (33% of total) are known to have died (median, 1.7 years from MRI to death); 3 had cardiac arrhythmia deaths where shocks were indicated without direct evidence of device dysfunction.
Data were acquired at a single center and may not be generalizable to other clinical settings and MRI facilities. Implantable cardioverter-defibrillator interrogations were not available for a subset of patients; adjudication of cause of death relied solely on death certificate data in a subset.
Non-MRI-conditional ICDs appropriately treated detected tachyarrhythmias after MRI. No serious adverse effects on device function were reported after MRI.
Johns Hopkins University and National Institutes of Health.
The safety and clinical utility of MRI at 1.5 T in patients with cardiac implantable devices such as pacemakers (PM) and implantable cardioverter-defibrillators (ICD) have been reported. This study ...aims to evaluate the extent of artifacts on cardiac magnetic resonance (CMR) in patients with PM and ICD (PM/ICD).
A total of 71 CMR studies were performed with an established safety protocol in patients with prepectoral PM/ICD. The artifact area around the PM/ICD generator was measured in all short-axis (SA), horizontal (HLA), and vertical long-axis (VLA) SSFP cine planes. The location and extent of artifacts were also assessed in all SA (20 sectors per plane), HLA, and VLA (6 sectors per plane) late gadolinium-enhanced CMR (LGE-CMR) planes. The artifact area on cine CMR was significantly larger with ICD versus PM generators in each plane (P<0.001, respectively). In patients with left-sided ICD or biventricular ICD systems, the percentages of sectors with any artifacts on LGE-CMR were 53.7%, 48.0%, and 49.2% in SA, HLA, and VLA planes, respectively. Patients with left-sided PM or right-sided PM/ICD had fewer artifacts. Anterior and apical regions were severely affected by artifact caused by left-sided PM/ICD generators.
In contrast to patients with right-sided PM/ICD and left-sided PM, the anterior and apical left ventricle can be affected by susceptibility artifacts in patients with left-sided ICD. Artifact reduction methodologies will be necessary to improve the performance of CMR in patients with left sided ICD systems.
BACKGROUND—The association of local electrogram features with scar morphology and distribution in nonischemic cardiomyopathy has not been investigated. We aimed to quantify the association of scar on ...late gadolinium-enhanced cardiac magnetic resonance with local electrograms and ventricular tachycardia circuit sites in patients with nonischemic cardiomyopathy.
METHODS AND RESULTS—Fifteen patients with nonischemic cardiomyopathy underwent late gadolinium-enhanced cardiac magnetic resonance before ventricular tachycardia ablation. The transmural extent and intramural types (endocardial, midwall, epicardial, patchy, transmural) of scar were measured in late gadolinium-enhanced cardiac magnetic resonance short-axis planes. Electroanatomic map points were registered to late gadolinium-enhanced cardiac magnetic resonance images. Myocardial wall thickness, scar transmurality, and intramural scar types were independently associated with electrogram amplitude, duration, and deflections in linear mixed-effects multivariable models, clustered by patient. Fractionated and isolated potentials were more likely to be observed in regions with higher scar transmurality (P<0.0001 by ANOVA) and in regions with patchy scar (versus endocardial, midwall, epicardial scar; P<0.05 by ANOVA). Most ventricular tachycardia circuit sites were located in scar with >25% scar transmurality.
CONCLUSIONS—Electrogram features are associated with scar morphology and distribution in patients with nonischemic cardiomyopathy. Previous knowledge of electrogram image associations may optimize procedural strategies including the decision to obtain epicardial access.
BACKGROUND—The association of scar on late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) with local electrograms on electroanatomic mapping has been investigated. We aimed to quantify ...these associations to gain insights regarding LGE-CMR image characteristics of tissues and critical sites that support postinfarct ventricular tachycardia (VT).
METHODS AND RESULTS—LGE-CMR was performed in 23 patients with ischemic cardiomyopathy before VT ablation. Left ventricular wall thickness and postinfarct scar thickness were measured in each of 20 sectors per LGE-CMR short-axis plane. Electroanatomic mapping points were retrospectively registered to the corresponding LGE-CMR images. Multivariable regression analysis, clustered by patient, revealed significant associations among left ventricular wall thickness, postinfarct scar thickness, and intramural scar location on LGE-CMR, and local endocardial electrogram bipolar/unipolar voltage, duration, and deflections on electroanatomic mapping. Anteroposterior and septal/lateral scar localization was also associated with bipolar and unipolar voltage. Antiarrhythmic drug use was associated with electrogram duration. Critical sites of postinfarct VT were associated with >25% scar transmurality, and slow conduction sites with >40 ms stimulus-QRS time were associated with >75% scar transmurality.
CONCLUSIONS—Critical sites for maintenance of postinfarct VT are confined to areas with >25% scar transmurality. Our data provide insights into the structural substrates for delayed conduction and VT and may reduce procedural time devoted to substrate mapping, overcome limitations of invasive mapping because of sampling density, and enhance magnetic resonance–based ablation by feature extraction from complex images.
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