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VT Ablation in Patients With Intramural Scar
Study Questions:
What is the effect of a stepwise, cardiac magnetic resonance imaging (cMRI)-guided ablation approach for ventricular tachycardia (VT) in patients with intramural scar?
Methods:
Over a 5-year period, 42 patients with VT and predominantly intramural scarring on cMRI were included. Patients underwent a stepwise ablation strategy consisting of: 1) localized ablation via conventional mapping techniques, and 2) additional “extensive ablation” covering cMRI identified scar if VT was still inducible. More specifically, the left and right ventricular endocardium were mapped if intramural scar was present in the left ventricular septum, the left ventricular endocardium and epicardium were mapped for free wall scar, and areas of the predominant scar were targeted in cases of multifocal scarring. The surface closest to the scar was ablated first. Outcomes were compared to a historical control group comprised of 19 patients with nonischemic cardiomyopathy (NICM) who underwent localized VT ablation only (no cMRI). A novel measurement, the scar-depth index (SDI), was used to calculate the percentage of scar at different depths from the nearest surface and was correlated with outcomes.
Results:
Of the 42 patients, 38 had NICM, median follow-up was 17 years, 67% (28) had history of prior ablation, and 69% (29) had scar in the interventricular septum. Acute procedural success was achieved in 57% (24), with 11 rendered noninducible after extensive ablation (cMRI guided). Total scar and scar volumes did not correlate with outcomes. An SDI (0-3 mm depth) >52.5% predicted ablation success. SDI (>5 mm depth) >16.5% was associated with unsuccessful ablation. SDI (>5 mm depth) was associated with worse long-term clinical events. One-year freedom from recurrent VT, death, or cardiac transplant was observed in 76% (32/42) overall, in 69% (18/26) of the extensive ablation group, and in 37% (7/19) of the control group.
Conclusions:
A stepwise ablation strategy utilizing cMRI in patients with VT and intramural scar was safe and effective. A new measurement of scar depth correlated with short- and long-term outcomes.
Perspective:
This pilot study demonstrates the potential of cMRI-guided assessment of scar location and scar depth for procedure planning in and risk assessment of patients with intramural scar-mediated VT. The authors describe a new approach for evaluating the characteristics of the clinically relevant scar. VT emanating from intramural scar is difficult to ablate. Emerging alternative or adjunctive strategies include bipolar ablation, ethanol ablation, retractable needle ablation, and half-normal saline irrigation. All of these can cause collateral damage to surrounding structures, but may be needed in those with deeper scar. Obtaining high-quality cMRIs can be challenging as well, depending on the expertise of the hospital or institution. Most of these patients will have implantable-cardioverter defibrillators (source of artifact) and many will need expeditious workup of their arrhythmia and cardiomyopathy.
Clinical Topics: Arrhythmias and Clinical EP, Cardiac Surgery, Cardiovascular Care Team, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Prevention, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Cardiac Surgery and Arrhythmias, Cardiac Surgery and Heart Failure, Acute Heart Failure, Heart Transplant, Interventions and Imaging, Magnetic Resonance Imaging
Keywords: Arrhythmias, Cardiac, Cardiomyopathies, Catheter Ablation, Diagnostic Imaging, Endocardium, Heart Failure, Heart Transplantation, Magnetic Resonance Imaging, Pericardium, Risk Assessment, Secondary Prevention, Tachycardia, Ventricular, Ventricular Septum
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