Rescue Ablation of Electrical Storms in a Patient with Remote Myocardial InfarctionKatherine Fan Grantham Hospital Hong Kong SARPatient Mr. LnM/64nHistory of inferior MI 1989- MVR for papillary muscle rupture and severe MRnIschemic cardiomyopathy (EF 30%)nVT 1997- ICD implanted / generator change 2002nChronic smoker/ COPDVentricular ArrhythmiasnICD (single-chamber) 1997nAmiodarone added in 2001 for PAF/ NSVTnRecurrent VT episodes in 3/2005 with increased dosage of amiodaronenDeveloped SOB- diagnosed amiodarone induced pulmonary fibrosis: Amiodarone stopped/ High dose steroids requiredn-blockers / sotalol- not tolerated exacerbation of COPDnRecurrent VT episodes- mexiletine started but complicated by neurological signs (limb tremor and gait instability)Electical StormsnNov 2005- admitted after recurrent ICD shocksnInterrogations: n58 episodes of VT detectednMost terminated with ATPnSome accerlerated to fast VT which was then termianted with cardioversion shocksnEarly re-initiation of VTVT MorphologiesLBBB/ Left superior axis QRSRBBB/ Right superior axis QRSATPRBBB/R sup LBBB/ L supRBBB/ R supMitral valve prothesisRAOINFSinus RhythmVT 1VT 2Lesions CreatedTermination of VT (RF #38!)onRFCatheter Ablation of the Mitral Isthmus for VT associated with Inferior Infarction Wilber et al. Circulation 1995;92:3481-3489By virtue of its narrow By virtue of its narrow dimension, the isthmus dimension, the isthmus became the vulnerable became the vulnerable point to interrupt this point to interrupt this circumferential activationcircumferential activationRBBB/ Right superior axisLBBB/Left superior axisMitral Isthmus Ventricular TachycaridanCritical zone of slow conduction activated parallel to mitral isthmus in either direction resulting in 2 distinct but characteristic QRS configurationsnLBBB with left superior axis- rS in V1 and aVR/ R in V6, I, aVLnRBBB with right superior axis- R in V1 and aVR/ QS in V6, I, aVLLBBB/LADRBBB/RADWilber et al. Circulation 1995Dynamic Substrate Map Sinus RhythmLow Voltage Zone RAO viewInferior viewDynamic Substrate Map Ventricular TachycardiaRAO viewInferior viewLow Voltage Zone Composite Substrate ProfileDSM Sinus RhythmComposite Substrate MapDSM VTFixed BlockFunctional BlockMarked LesionsRAO viewInferior viewAnother Marked LesionsRAO viewInferior viewSubstrate-Orientated VT AblationnA definite trigger or delineated scar has been characterized as a requirement for substrate orientated ablation of intractable unmappable VTnTargetsnCritical isthmusnAreas of slow conductionnExit sites- often located at the border of the scarred myocardiumScar Border Zone SubstratenVT originated from area of diseased tissue surrounding dense scarnBased on surgical approaches to treat VT (sub- endoardial resection), methods of ablating ischemic VT by “ substrate mapping” in SR have been used successfully in pts with drug refractory hemodynamically unstable MMVTnUse electroanatomical voltage mapping to define regions of scar and viable endocardium in SR followed by ablations in the border zone regionsAnatomical vs Functional Substrate Limitation of Voltage Mapping during SRnBoundaries of the isthmus could be functional lines of block not detected during SRnDispersion of voltage (heterogeneity) in scar areas may appear only when activated at VT rate and/or orientationnPost MI structural remodeling Alteration of anisotropy depended on electrotonic loads and orientationSummarynSuccessful ablation of mitral isthmus for VT associated with remote inferior infarctionnCharacteristic of VT morphologies and its corresponding activation mappings demonstratednDynamic substrate mapping during SR and VT provided complimentary data on substrate identification (anatomical vs functional)Ventricular Tachycardia 1Ventricular Tachycardia 2Relationship Between Successful Ablation Sites and the Scar Border Zone Defined by Substrate Mapping for Ventricular Tachycardia Post-MI Verma et al. JCE 2005:16:465-471295981579 23* Dense scar= bipolar voltage 0.5mVSuccessful Ablation Within ScarnCritical isthmus may originate in scar and exit in border zone or may exist entirely within scarnThin strands of surviving myocytes “zigzagging” through dense areas of scar- substratenThick layers of survivung myocardium existing beneath dense endocardial scar- ?return path of circuitnLinear ablations that extend outside of the scar border and into the regions of dense infarction may be requirednSome advocated targeting sites within scar by identification of isolated, delayed components of local EGMAnatomical Substrate vs Electrophysiological SubstratenAnisotropy- determined by cell orientation/ morphology and cell-to-cell connections (gap junctions) nDiseased state (eg MI/ heart failure)- structural remodeling alters the ansiotropy and increases its heterogeneity and potential for arrhythmia developmentn? Extent of “ functional substrate” depends on the electrotonic loads and orientationnE