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.
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.
From: 2011 SCMR/Euro CMR Joint Scientific Sessions Nice, France 3-6 February 2011 Author details1-Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, ...USAEMPTY2-Philips Healthcare, Cleveland, OH, USAEMPTY3-Institute for Biomedical Engineering, University and ETH Zurich, Zurich, SwitzerlandEMPTY4-Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, USAEMPTY5-Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD, USAEMPTY Supplemental Information: The second independent navigator provides motion compensation for the phase reference images. figure omitted; refer to PDF Methods Imaging was performed on a 3T system (Philips Healthcare, Best, The Netherlands) using a 32-channel cardiac array coil (InVivo, Gainsville FL).
Abstract only Introduction: Imaging tissue heating during RF ablation may permit more accurate placement and titration of ablation lesions. Standard proton resonance frequency shift MRI thermography, ...however, is limited by sensitivity to physiologic motion and scanner phase drift between acquisition of ablation and reference pre-heating images. The aim of this study is to assess the feasibility of referenceless MRI thermography which addresses this limitation by eliminating need for a separate pre-heating image but has not yet been applied to cardiac ablation. Methods: An MRI compatible copper electrode catheter was inserted into the left ventricle in 6 dogs. Gradient recalled echo images were acquired while applying RF power in 3W increments until high impedance was reached. Gross pathology was obtained. The pre-heating image was estimated from the ablation image phase component (A) by unwrapping phase (B), masking the catheter tip region where heating was expected (C), and extrapolating phase from unmasked regions of the heart using a fourth order polynomial fit (D). Thermography images were then computed using standard methods (E). Thermography lesion extent was defined by tissue temperature above 50°C. Electrode artifact was defined by darkened myocardium adjacent to the catheter tip on the magnitude component of the ablation image. Results: Transmural lesion extent by referenceless MR thermography was within 20% of that obtained by pathology (inset F) in the four cases where the electrode artifact transmurality was less than 25%. However, thermography and pathology lesion extent differed by over 60% in the two cases where electrode artifact transmurality was greater than 40%. Conclusion: Referenceless MR thermography of cardiac RF ablation is possible and may permit more practical MR thermography monitoring of cardiac ablation. Reducing electrode artifact by using lower magnetic susceptibility materials appears required for more reliable temperature assessment.
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