Post-myocardial Infarction Ventricular Tachycardia Research Articles

The importance of the right ventricular insertion area for the functional substrate of ventricular tachycardia after myocardial infarction

Abstract Funding Acknowledgements Type of funding sources: None. Background Conducting systematic annotation and ablation of evoked delayed potentials (EDP) in response to short coupled right ventricular extra-stimuli (RV-ES) has improved ablation outcome of post myocardial infarction (MI) ventricular tachycardia (VT). The reported short radiofrequency catheter ablation (RFCA) times suggests the presence of predilection areas for these functional substrates. Purpose To evaluate the electroanatomical characteristics and distribution of EDPs in post-MI patients referred for RFCA of VT. Methods Electroanatomical mapping (EAM) data of 48 post-MI patients (69 ± 9 years, 39 male, LV ejection fraction 36 ± 10%, anterior MI 20 [42%], inferior MI 28 [58%]), who underwent functional substrate mapping and ablation were analyzed. Pre-procedural cardiac CTs of 16 patients (8 anterior, 8 inferior MI) were integrated with EAM data. Infarct extension (defined as bipolar voltage [BV] <3.0mV, dense scar <0.5mV and scar borderzone [BZ] 0.5-3mV) and EDP location were determined based on the AHA 17-segment model of the left ventricle. Results RV-ES was performed during mapping at 2180 LV sites (median 46 per patient, range 8-81) and EDPs were observed at 631 (29%) sites. Patients had a median of 11 (range 1-37) EDP sites. Compared to no-EDP sites, EDP sites had lower BV (median 0.57 mV vs. 0.77 mV, P <0.001), longer duration (median 79 ms vs. 66 ms, P <0.001), and larger number of positive sharp deflections (median 6 vs. 5, P <0.001) during sinus rhythm. Of all EDP sites, 278 (44%), 286 (45%), 64 (10%), and 3 (1%) had BV of <0.5mV, ≥ 0.5mV and <1.5 mV, a BV of ≥1.5 mV and <3.0 mV, and a BV of >3.0 mV, respectively. In the 16 patients with CT image integration, a total of 124/272 segments showed EA scar with a median (IQR, range) of 8 (6-9, 4-12) segments per patient. Any EDP was identified in 71/124 (57%) of segments with EA scar. Of note, 73% of all EDPs in inferior MIs and 64% of all EDPs in anterior MI were located in 4 AHA segments, namely 3,4, 9,10 and 7,8,13,14, respectively, close to the inferior or anterior RV insertion. Such a cluster of EDP sites around the RV insertion was found in 6 (75%) patients with inferior MI and in 7 (88%) patients with anterior MI. Conclusion About 10% of EDPs are identified at sites with BV of ≥1.5mV and <3.0mV during sinus rhythm supporting the recently proposed BV threshold <3.0mV for post-MI scars. EDPs are frequently located near the RV insertion in both inferior MI and anterior MI suggesting a role of the RV insertion in the functional substrate of post-MI VT.

PO-04-170 AUTOMATED CT-BASED PREDICTION OF VENTRICULAR ARRHYTHMIA

Robust risk stratification of post-myocardial infarction (MI) ventricular tachycardia (VT) is desirable to overcome the limitations of left ventricular ejection fraction (LVEF), the currently used criterion for implanting cardiac defibrillator devices. We hypothesized, that a fully automated CT-based technology could predict VT in post-MI patients. A fully automated CT image processing pipeline was implemented including AI-based LV wall segmentation followed by joint analysis and quantification of wall thickness (WT), intramural fat, and myocardial calcification (Fig.1A). A cohort of 132 patients with prior MI (66±11 years, 37±10% LVEF) with implanted cardiac devices underwent CT scan, and were subsequently followed by remote monitoring over an average of 6.6 years (80 ± 31 months). We analyzed the relationship between CT markers (WT, fat, calcification) and VT events at follow-up. Analysis of the wall thickness layers showed the optimal WT-derived marker was the ratio between areas of WT < 3mm and WT< 5mm (no VT 0.57±0.45 vs. VT 0.89±0.55; p<0.01). The amount of myocardial calcification was also found higher in patients with VT (no VT 0.10±0.38ml vs. VT 0.47±1.57ml, p=0.039), while the amount of fat did not differ significantly between groups (no VT 1.14±1.38ml vs. VT 1.21±1.01ml, p=0.771). The optimal cut-off for the WT 3/5mm ratio was 0.3. On Kaplan Meier analysis, this WT ratio was a powerful predictor of VT-free survival (Fig.1B, log rank P<0.01). In contrast, a LVEF<35% was not found to significantly relate to VT-free survival (Fig.1C, P=0.77). Automated analysis of post-MI scar is doable from CT images, allowing for improved risk stratification of future VT. The area of severe wall thinning divided by the total area of thinning appears to be the best marker of risk.

Importance of Right Ventricular Mapping and Ablation for Ventricular Tachycardia in Postinfarction Patients.

The characteristics of patients with post-myocardial infarction (PMI) ventricular tachycardia (VT) who require right ventricular (RV) ablation are underreported. The aims of this study were to examine the characteristics and outcomes of patients undergoing PMI VT ablation who have target sites in the right ventricle and to compare patient and VT characteristics between patients with free wall vs septal RV target sites. Consecutive patients undergoing ablation for PMI VT with target sites located within the right ventricle were included. Patients were stratified on the basis of the presence of free wall vs septal RV target sites. Among 277 consecutive patient undergoing PMI VT ablation, 30 (11%) had RV target sites (mean age 68.71 ± 9.5 years, 29 men [97%], mean left ventricular ejection fraction [LVEF] 28.7% ± 16.7%). Twenty patients had only septal VTs, and 10 patients had only free wall VTs. Fifty-seven VTs with RV targets (1.9 ± 1.4 per patient, mean cycle length 338± 90ms, 53 left bundle branch, 36 superior axis) were induced. Patients with RV free wall VTs had greater rates of RV dysfunction (80% vs 30%; P=0.023) but had greater LVEFs (38.3% ± 21.06% vs 23.9% ± 11.93%; P=0.02). Overa mean follow-up period of 3.4 ± 3.2 years, patients with RV septal target sites had worse survival free of VT, transplantation, or left ventricular assist device placement after ablation (log-rank P< 0.05). The arrhythmogenic substrate in PMI patients often involves the right ventricle, including the septum and free wall. The presence of RV dysfunction and greater LVEF were associated with the presence of RV free wall target sites. Patients with only RV septal target sites had worse postablation outcomes.

Abstract 14991: Local Prolongation of Repolarization Prevents Post Myocardial Infarction Ventricular Tachycardia

Introduction: Reentry is the predominant mechanism underlying ventricular arrhythmias in chronic myocardial infarction patients. Reentry can be prevented by prolonging effective refractory period, thereby blocking reexcitation of recently activated tissue. This is currently achieved with systemically administered class III antiarrhythmic drugs. These therapies are limited by their risk of provoking ventricular arrhythmias by off-target effects. Hypothesis: Local prolongation of repolarization in healthy myocardium adjacent to the exit site attenuates reentry and postinfarction arrhythmias. Method and results: We used a pig model and generated myocardial infarction by balloon occlusion of the left anterior descending coronary artery and performed epicardial mapping 6 weeks later during Langendorff-perfusion. Programmed stimulation induced reentry leading to ventricular premature beats and sustained ventricular tachycardia (VT). Local injection of Sotalol adjacent to the infarcted myocardium prolonged repolarization and prevented VT after programmed stimulation. To translate these experimental findings to the patient situation we used a virtual heart based on data from a patient suffering from postmyocardial infarction VTs. The patient underwent pre-ablation cardiac late gadolinium enhanced- magnetic resonance imaging followed by geometrical reconstruction of the left ventricle and computational electrophysiological modelling of VT induction. We used a rapid pacing protocol to induce VT and determined the site where the activation front exited the infarct zone and reactivated the adjacent normal myocardium. Next, we prolonged repolarization of the normal myocardium adjacent to the exit site with 50 ms and performed rapid pacing to induce VT. This only resulted in a single premature ventricular beat after which sinus rhythm restored. Conclusion: Our experimental and in silico findings show the potential of local prolongation of repolarization a novel potentially genetic anti-arrhythmic therapy in post-infarction patients.

Lipomatous Metaplasia Enables Ventricular Tachycardia by ReducingCurrent Loss Within theProtected Corridor.

Post-myocardial infarction ventricular tachycardia (VT) is due to re-entry through surviving conductive myocardial corridors across infarcted tissue. However, not all conductive corridors participate in re-entry. This study sought to test the hypothesis that critical VT corridors are more likely to traverse near lipomatous metaplasia (LM) and that current loss is reduced during impulse propagation through such corridors. Among 30 patients in the Prospective 2-center INFINITY (Intra-Myocardial Fat Deposition and Ventricular Tachycardia in Cardiomyopathy) study, potential VT-viable corridors within myocardial scar or LM were computed from late gadolinium enhancement cardiac magnetic resonance images. Because late gadolinium enhancement highlights both scar and LM, LM was distinguished from scar by using computed tomography. The SD of the current along each corridor was measured. Scar exhibited lower impedance than LM (median Z-score -0.22 [IQR: -0.84 to 0.35] vs -0.07 [IQR: -0.67 to 0.54]; P&lt; 0.001). Among all 381 corridors, 84 were proven to participate in VT re-entry circuits, 83 (99%) of which traversed or were adjacent to LM. In comparison, only 13 (4%) non-VT corridors were adjacent to LM. Critical corridors adjacent to LM displayed lower SD of current compared with noncritical corridors through scar but distant from LM (2.0[IQR: 1.0 to 3.4] μA vs 8.4 [IQR: 5.5 to 12.8] μA; P&lt; 0.001). Corridors critical to VT circuitry traverse infarcted tissue through or near LM. This association is likely mediated by increased regional resistance and reduced current loss as impulses traverse corridors adjacent to LM.

Myocardial calcification is associated with endocardial ablation failure of post-myocardial infarction ventricular tachycardia.

In patients with post-myocardial infarction (post-MI) ventricular tachycardia (VT), the presence of myocardial calcification (MC) may prevent heating of a subepicardial VT substrate contributing to endocardial ablation failure. The aims of this study were to assess the prevalence of MC in patients with post-MI VT and evaluate the impact of MC on outcome after endocardial ablation. In 158 patients, the presence of MC was retrospectively assessed on fluoroscopy recordings in seven standard projections obtained during pre-procedural coronary angiograms. Myocardial calcification, defined as a distinct radiopaque area that moved synchronously with the cardiac contraction, was detected in 30 patients (19%). After endocardial ablation, only 6 patients (20%) with MC were rendered non-inducible compared with 56 (44%) without MC (P = 0.033) and of importance, 8 (27%) remained inducible for the clinical VT [compared with 9 (6%) patients without MC; P = 0.003] requiring therapy escalation. After a median follow-up of 31 months, 61 patients (39%) had VT recurrence and 47 (30%) died. Patients with MC had a lower survival free from the composite endpoint of VT recurrence or therapy escalation at 24-month follow-up (26% vs. 59%; P = 0.003). Presence of MC (HR 1.69; P = 0.046), a lower LV ejection fraction (HR 1.03 per 1% decrease; P = 0.017), and non-complete procedural success (HR 2.42; P = 0.002) were independently associated with a higher incidence of VT recurrence or therapy escalation. Myocardial calcification was present in 19% of post-MI patients referred for VT ablation and was associated with a high incidence of endocardial ablation failure.

Epicardial voltage mapping in patients with postinfarction ventricular tachycardia: a pilot study

Introduction. Radiofrequency ablation (RFA) is an established treatment of post-myocardial infarction ventricular tachycardia (VT). Endocardial VT ablation can be insufficient for VT termination when the scar is intramural/epicardial.Purpose: to assess the extent of epicardial electrophysiological VT substrate in patients with remote myocardial infarction.Materials and methods. Thirteen patients with sustained postinfarction VT, who signed an informed consent, were included into the study. All patients underwent full clinical evaluation. Electroanatomical voltage bi- and unipolar mapping of endocardial and epicardial surfaces was performed. Maps were evaluated for the presence of low-voltage areas and local abnormal ventricular activity (LAVA). RFA was performed at LAVA sites. The end-point of the procedure was scar LAVA abolition and VT noninducibility (procedure success). VT recurrence was detected using an implantable cardioverter-defibrillator and/or ECG monitoring.Results. Epicardial access was successful in 12 patients. Epicardial access was performed at a first procedure in 7 patients, 4 patients had a history of previous endocardial ablation. Epicardial LAVA sites were detected in 9 patients. Endocardial and epicardial arrhythmogenic substrate localization coincided in 8 patients. One patient had only epicardial scar, 1 patient had only septal endocardial scar. In one patient LAVA sites had different localizations on epicardial and endocardial maps. Acute ablation success was noted in 12 patients.Conclusion. In our patient group transmural scar and epicardial electrophysiological arrhythmogenic substrate was detected in 82% of cases. Isolated endocardial ablation may be unsuccessful, in such cases epicardial mapping and ablation might be useful.

P357Epicardial abnormal electrical activity in unselected patients with ischemic ventricular tachycardia: a pilot mapping study

Abstract Background radiofrequency catheter ablation (RFA) on the endocardial ventricular surface is widely used for post-myocardial infarction (post-MI) ventricular tachycardia (VT) treatment. It has been described that about 10% of patients with post-MI require additional epicardial ablation for successful VT termination. However, there is still lack of data regarding the extent of scarring and the presence of local abnormal ventricular electrical activity (LAVA, low-voltage and/or fractionated signals) on the epicardial surface in patients with ischemic VT. Purpose to assess the extent of epicardial electrophysiological substrate in patients with remote myocardial infarction and indications for VT ablation. Methods thirteen out of 59 patients with sustained ischemic VT (12 men; mean age 59,9 ± 9,5) and without previous cardiac surgery signed an informed consent to undergo epicardial mapping and comprized the study population. Endocardial access was used previously as primary method in 4 patients ICD/ CRT-D had been previously implanted in 11 patients: mean left ventricle ejection fraction was 38,8 ± 10,6 %: hemodynamically unstable VT was present in 10 patients; the most frequent scar localization by ECG and transthoracic echocardiography – left ventricle (LV) inferior wall (10 patients), LV lateral wall – (7 patients). All patients underwent full clinical evaluation. Electrophysiological procedure and catheter ablation was performed under general anesthesia. Epicardial access was obtained through percutaneous subxyphoid puncture. Voltage mapping of endocardial and epicardial surfaces was performed. Maps were evaluated for the presence of LAVA. Ablation was performed at sites of LAVA on either side of the ventricular wall. Results epicardial access was successful in 12 patients. Bi- and unipolar mapping was successfully performed and analyzed in 11 subjects. LAVA was present in all but one patient on endocardial surface and in 9 (82%) out of 12 patients on epicardial surface. Localization of endocardial and epicardial LAVA coincided in 8 (67%) patients suggesting transmural ischemic scar. One patient had only epicardial scar, 1 patient had septal endocardial scar without LAVA on the epicardial surface. In one patient LAVA sites were localized on different left ventricle walls. More extensive unipolar than bipolar endocardial scar area was found (11,8 (IQR:2,0;31,6) vs 45,8 (IQR:17,1;86,5) сm2; р=0,03). Epicardial unipolar scar area prevailed over bipolar scar area: median 46.0 cm2 (IQR: 15.9;55.5) vs 107.7 cm2 (IQR: 84.3;168.9) р=0,04. LAVA epicardial area was wider than endocardial: 19.7 cm2 (IQR: 2.3; 29.7) vs 4.1 cm2 (IQR: 0.4; 23.8) р=0.03. Conclusion according to the results of our pilot study in unselected patients with ischemic VT, epicardial arrhythmogenic substrate was detected in 82% of cases. Epicardial LAVA area significantly prevailed over endocardial LAVA area.

Multisize Electrodes for SubstrateIdentification in IschemicCardiomyopathy: Validation by Integration of Whole Heart Histology.

This study sought to evaluate the value of combined electrogram (EGM) information provided by simultaneous mapping using micro- and conventional electrodes in the identification of post-myocardial infarction ventricular tachycardia substrate. Ventricular tachycardias after myocardial infarction are related to scars with complex geometry. Scar delineation and ventricular tachycardia substrate identification relies on bipolar voltages (BV) and EGM characteristics. Early reperfusion therapy results in small, nontransmural scars, the details of which may not be delineated using 3.5 mm tip catheters. Nine swine with early reperfusion myocardial infarction were mapped using Biosense Webster's QDOT Micro catheter, incorporating 3 microelectrodes at the tip of the standard 3.5 mm electrode. Analysis of EGM during sinus rhythm, right ventricular pacing, and short-coupled right ventricular extrastimuli was performed. The swine were sacrificed and mapping data were projected onto the heart. Transmural biopsies (n=196) corresponding to mapping points were obtained, allowing a head-to-head comparison of EGM recorded by micro- and conventional electrodes with histology. To identify scar areas using standard electrodes, unique cutoff values of unipolar voltage<5.44mV, BV<1.27mV (conventional), and BV<2.84mV (microelectrode) were identified. Combining the information provided by unipolar voltage and BV mapping, the sensitivity of scar identification was increased to 93%. Micro-EGM were better able to distinguish small near-fields corresponding to a layer of viable subendocardium than conventional EGM were. The combined information provided by multisize electrode mapping increases the sensitivity with which areas of scar are identified. EGM from microelectrodes, with narrower spacing, allow identification of near-fields arising from thin subendocardial layer and layers activated with short delay obscured in EGM from conventional mapping catheter.

Targeting the Hidden Substrate Unmasked by Right Ventricular Extrastimulation Improves Ventricular Tachycardia Ablation Outcome After Myocardial Infarction.

This study sought to determine whether ablation of hidden substrate unmasked by right ventricular extrastimulation (RVE) improves ablation outcome of post-myocardial infarction (MI) ventricular tachycardia (VT). In patients with small or nontransmural scars after MI, part of the VT substrate may be functional and,in addition, masked by high-voltage far-field signals arising from adjacent normal myocardium. In 60 consecutive patients, systematic analysis of electrograms recorded from the presumed infarct area was performed during sinus rhythm, RV pacing at 500 ms, and during a short-coupled RV extrastimulus. Sites showing low-voltage, near-field potentials with evoked conduction delay in response to RVE were targeted. In 37 (62%) patients, ablation target sites located in areas with normal voltage during sinus rhythm were unmasked by RVE (hidden substrate group). These patients had better left ventricular function (36 ± 11% vs. 26 ± 12%; p= 0.003), smaller electroanatomical scars (<1.5 mV), and smaller dense scars (<0.5 mV) (median 59 and 14 cm2 vs. 82 and 44 cm2; p= 0.044 and p= 0.003) than did those in whom no hidden substrate was identified (overt substrate group). During a median follow-up of 16 months, 13 (22%) patients had VT recurrence. Patients with hidden substrate had a lower incidence of VT recurrence (12-month VT-free survival 89% vs. 50% in patients with overt substrate; p=0.005). Compared with a historical cohort of 90 post-MI patients matched for left ventricular function and electroanatomical scar area, in whom no RVE was performed, patients in the hidden substrate group had a higher 1-year VT-free survival (89% vs. 73%; p= 0.039). Hidden substrate ablation unmasked by RVE improves ablation outcome in post-MI patientswithsmall or nontransmural scars.

Long-Term Outcome of Substrate Modification in Ablation of Post-Myocardial Infarction Ventricular Tachycardia.

Long-term results of substrate modification for ablation of ventricular tachycardia (VT) have not been reported. We report long-term outcomes of substrate elimination targeting local abnormal ventricular activities (LAVA) for post-myocardial infarction VT. One hundred fifty-nine consecutive patients undergoing first ablation were included (65±11 years, 92% implantable cardioverter defibrillators, 54% storms, and 73% appropriate shocks). LAVA were identified in 92% and VT was inducible in 73%. Complete LAVA elimination and noninducibility after ablation were achieved in 64% and 85%. During a median follow-up of 47 months (interquartile range, 34-82), single-procedure ventricular arrhythmia (VA)-free survival was 55% (10% storms and 19% shocks). The VA-free survival was 73%, 68%, 61%, 55%, and 49% after 1, 2, 3, 4, and 5 years, respectively. Complete LAVA elimination was associated with improved outcomes: VA-free survival of 82% at 1 year and 61% at 5 years. In the subgroup treated with multielectrode mapping and real-time image integration, VA-free survival was 86% and 65% at 1 year and 4 years, respectively. Including repeat procedures in 18% of pts (1.3±0.6 ablations/pt) outcomes improved to 69% VA-free survival (2% storms and 9% shocks) during median 46-month follow-up. Overall survival was 91% at 1 year and 77% at 5 years of follow-up. In this monocentric study, substrate modification targeting LAVA for post-myocardial infarction VT resulted in a substantial reduction of VT storm and implantable cardioverter defibrillator shocks and up to 49% of patients free from arrhythmia at 5 years after a single procedure. Complete LAVA elimination, multielectrode mapping, and real-time integration were associated with improved VA-free survival.

1219Comparison of procedural endpoints for ablation of post-myocardial infarction ventricular tachycardia

1219Comparison of procedural endpoints for ablation of post-myocardial infarction ventricular tachycardia

QRS/T-wave and calcium alternans in a type I diabetic mouse model for spontaneous postmyocardial infarction ventricular tachycardia: A mechanism for the antiarrhythmic effect of statins

The incidence of sudden arrhythmic death is markedly increased in diabetics. The purpose of this study was to develop a mouse model for postmyocardial infarction (post-MI) ventricular tachycardia (VT) in the diabetic heart and determine the mechanism of an antiarrhythmic effect of statins. ECG transmitters were implanted in wild-type (WT), placebo, and pravastatin-treated type I diabetic Akita mice. MIs were induced by coronary ligation, and Ca2+ transients were studied by optical mapping, and Ca2+ transients and sparks in left ventricular myocytes (VM) by the Ionoptix system and confocal microscopy. Burst pacing of Akita mouse hearts resulted in rate-related QRS/T-wave alternans, which was attenuated in pravastatin-treated mice. Post-MI Akita mice developed QRS/T-wave alternans and VT at 2820 ± 879 beats per mouse, which decreased to 343 ± 115 in pravastatin-treated mice (n = 13, P <.05). Optical mapping demonstrated pacing-induced VT originating in the peri-infarction zone and Ca2+ alternans, both attenuated in hearts of statin-treated mice. Akita VM displayed Ca2+ alternans, and triggered activity as well as increased Ca2+ transient decay time (Tau), Ca2+ sparks, and cytosolic Ca2+ and decreased SR Ca2+ stores all of which were in part reversed in cells from statin treated mice. Homogenates of Akita ventricles demonstrated decreased SERCA2a/PLB ratio and increased ratio of protein phosphatase (PP-1) to the PP-1 inhibitor PPI-1 which were reversed in homogenates of pravastatin-treated Akita mice. Pravastatin decreased the incidence of post-MI VT and Ca2+ alternans in Akita mouse hearts in part by revering abnormalities of Ca2+ handling via the PP-1/PPI-1 pathway.

Impact of New Technologies and Approaches for Post-Myocardial Infarction Ventricular Tachycardia Ablation During Long-Term Follow-Up.

During the past years, many innovations have been introduced to facilitate catheter ablation of post-myocardial infarction ventricular tachycardia. However, the predictors of outcome after ablation were not thoroughly studied. From 2009 to 2013, consecutive patients referred for post-myocardial infarction ventricular tachycardia ablation were included. The end point of the procedure was complete elimination of local abnormal ventricular activities (LAVA) and ventricular tachycardia (VT) noninducibility. The predictors of outcome with primary end point of VT recurrence were assessed. A total of 125 patients were included (age: 64±11 years; 7 women) for 142 procedures. The left ventricle was accessed via transseptal, retrograde aortic, and epicardial approaches in 87%, 33%, and 37% of patients, respectively. Three-dimensional electroanatomical mapping system was used in 70%, multipolar catheter in 51%, and real-time image integration in 38% (from magnetic resonance imaging in 39% and multidetector computed tomography in 93%) of patients. Before ablation, VT was inducible in 75%, and endocardial/epicardial LAVA were present in 88%/75%. After ablation, complete LAVA elimination was achieved in 60%, and VT noninducibility in 83%. During a median follow-up of 850 days (interquartile range, 439-1707), VT recurrence was observed in 36%. Multivariable analysis identified 3 independent outcome predictors: the ability to achieve complete LAVA elimination (R(2)=0.29; P<0.0001; risk ratio=0.52 [0.38-0.70]), the use of real-time image integration (R(2)=0.21; P=0.0006; risk ratio=0.49 [0.33-0.74]), and the use of multipolar catheters (R(2)=0.08; P=0.05; risk ratio=0.75 [0.56-1.00]). Achievement of complete LAVA elimination and use of scar integration from imaging and multipolar catheters to focus high-density mapping are independent predictors of VT-free survival after catheter ablation for post-myocardial infarction ventricular tachycardia.

Infarct transmurality as a criterion for first-line endo-epicardial substrate–guided ventricular tachycardia ablation in ischemic cardiomyopathy

There is no consensus on the appropriate indications for the epicardial approach in substrate ablation of post-myocardial infarction (MI) ventricular tachycardia (VT). The purpose of this study was to investigate whether infarct transmurality (IT) could identify patients who would benefit from a combined first-line endo-epicardial approach. Before ablation, IT was assessed by contrast-enhanced cardiac magnetic resonance imaging (hyperenhancement ≥75% of the wall thickness in ≥1 segment), echocardiography (dyskinesia/akinesia + hyperrefringency + wall thinning), computed tomography (wall thinning), or scintigraphy (transmural necrosis). Prospectively from January 2011, an endocardial approach was used in patients with subendocardial MI (group 1) and a combined endo-epicardial approach in patients with transmural MI (group 2). Outcomes in both groups were compared with those in patients with transmural MI and only endocardial approach due to previous cardiac surgery or procedure performed before January 2011 (group 3). The primary end point was VT/ventricular fibrillation recurrence-free survival. Ninety patients (92.2% men; mean age 67.4 ± 9.8 years) undergoing VT substrate ablation were included: group 1, n = 34; group 2, n = 24; group 3, n = 32. During a mean follow-up duration of 22.5 ± 13.7 months, 5 patients in group 1 (14.7%), 3 patients in group 2 (12.5%), and 13 patients in group 3 (40.6%) had VT recurrences (P = .011). Time to recurrence was the shortest in group 3 (log-rank, P = .018). The endocardial approach in patients with transmural MI was associated with an increased risk of recurrence (hazard ratio 4.01; 95% confidence interval 1.41-11.3; P = .009). The endocardial approach in patients with transmural MI undergoing VT substrate ablation is associated with an increased risk of recurrence. IT may be a useful criterion for the selection of a first-line combined endo-epicardial approach.

Abstract 20209: Spontaneous Post Myocardial Infarction Arrhythmia is Potentiated by Calcium Alternans in Type I Diabetic Akita Mice

Introduction: Myocardial infarction (MI) is the most common cause of mortality in diabetes. Diabetics have been shown to be twice as likely to die suddenly from MI out of hospital compared to non diabetic patients. The mechanism of sudden death in the diabetic population is unclear. Here we use the Akita Type I diabetic mouse as an animal model for the study of post MI ventricular tachycardia arrhythmias (VT) and the role of abnormalities of Ca2+ homeostasis in the pathogenesis of post MI VT. Methods: To determine the effect of MI on the incidence of VT, EKG transmitters were implanted into WT and Akita mice. MIs were generated by permanent ligation of the left coronary artery resulting in infarctions affecting more than 30% of the LV as demonstrated by echocardiographic analysis and TTC staining. Dual calcium-voltage optical mapping was performed on the isolated Langendorf heart after MI. Left ventricular myocytes were isolated for calcium imaging studies. Sarcomere shortening and Ca2+transients were measured by Ionoptix system and Ca2+ sparks by confocal microscopy. Results: Compared to WT, Akita diabetic mice developed a high incidence of non sustained and sustained VT in the first 30h post MI peaking at 18 h. Epicardial optical mapping demonstrated pacing induced: Ca2+ alternans which was most marked in the peri-infarction zone of Akitas and VT also originating in the peri-infarction zone in the Akita mice, but not in WT. Single cardiomyocytes from Akita displayed both contractile and Ca2+ alternans when pacing rate was increased above 3Hz, but none in cells from WT mice. Ca2+ imaging studies were performed to determine whether alterations in Sacroplasmic reticulum(SR) Ca2+ function contributes to Ca2+ alternans. In Akita myocytes, Ca2+ transient decay time( Tau) was significantly increased ( 0.171±0.01s, N=23 ) compared to WT(0.139±0.007s, N=20, P&lt;0.05), The frequency of spontaneous Ca2+ sparks in Akita mocytes increased from 0.043 ± 0.003 sparks/100μm/s (N=23) in the WT to 0.266 ± 0.023 sparks/100μm/s ( P&lt;0.05, N=36). Conclusions: The type 1 diabetic Akita mice demonstrate a high incidence of spontaneous post MI VT associated with pronounced Ca2+ alternans in the peri-infarction zone and abnormalities of Ca2+ homeostasis.

Registro Español de Ablación con Catéter. XIII Informe Oficial de la Sección de Electrofisiología y Arritmias de la Sociedad Española de Cardiología (2013)

Introduction and objectivesThis report presents the results of the 2013 Spanish Catheter Ablation Registry. MethodsData were collected using 2 systems: retrospectively by completing a dedicated form and prospectively by reporting to a central database. Each participating center chose 1 of the 2 data collection methods. ResultsEighty centers voluntarily contributed data to the registry. A total of 11 987 ablation procedures were performed, with a mean (standard deviation) of 149 (105) procedures per center. The 3 main arrhythmic substrates treated were atrioventricular nodal reentrant tachycardia (n=2959; 24.6%), cavotricuspid isthmus ablation (n=2700; 22.5%), and atrial fibrillation (n=2201; 18.4%). The number of ventricular ablation procedures was similar to the 2012 activity, but there was a slight increase in procedures for scar-related postmyocardial infarction ventricular tachycardia. The success rate was 94.4%, major complications occurred in 1.8%, and the mortality rate was 0.03%. ConclusionsIn line with previous reports, the data from the 2013 registry show a continuing increase in the number of ablations performed. Overall, there was a high success rate and few complications. Ablation of complex substrates has continued to increase.Full English text available from:www.revespcardiol.org/en

Spanish Catheter Ablation Registry. 13th Official Report of the Spanish Society of Cardiology Working Group on Electrophysiology and Arrhythmias (2013)

Introduction and objectivesThis report presents the results of the 2013 Spanish Catheter Ablation Registry. MethodsData were collected using 2 systems: retrospectively by completing a dedicated form and prospectively by reporting to a central database. Each participating center chose 1 of the 2 data collection methods. ResultsEighty centers voluntarily contributed data to the registry. A total of 11 987 ablation procedures were performed, with a mean (standard deviation) of 149 (105) procedures per center. The 3 main arrhythmic substrates treated were atrioventricular nodal reentrant tachycardia (n=2959; 24.6%), cavotricuspid isthmus ablation (n=2700; 22.5%), and atrial fibrillation (n=2201; 18.4%). The number of ventricular ablation procedures was similar to the 2012 activity, but there was a slight increase in procedures for scar-related postmyocardial infarction ventricular tachycardia. The success rate was 94.4%, major complications occurred in 1.8%, and the mortality rate was 0.03%. ConclusionsIn line with previous reports, the data from the 2013 registry show a continuing increase in the number of ablations performed. Overall, there was a high success rate and few complications. Ablation of complex substrates has continued to increase.

Very Early Onset of Amiodarone-Induced Pulmonary Toxicity

Amiodarone is a widely used antiarrhythmic agent. Among its various adverse effects, amiodarone-induced pulmonary toxicity (APT) is the most life threatening complication, which has been described mostly in patients who have been in treatment with high accumulative doses for a long duration of time. However, amiodarone therapy in short-term duration induced APT was rarely reported. We describe a case of a 54-year-old man who is presented with symptoms of APT after a few days of therapy for post-myocardial infarction ventricular tachycardia. For early diagnosis and successful treatment, awareness and high suspicion of this rare type of early onset APT is crucial in patients with amiodarone therapy.

Multielectrode contact mapping to assess scar modification in post-myocardial infarction ventricular tachycardia patients

Substrate-based approaches for ablation of unmappable ventricular tachycardia (VT) are strictly dependent on high-density mapping of the scar. Ultra-high-density mapping with multielectrode catheters facilitates an accurate and faster definition of sites critical for re-entry, due to the possibility of simultaneous recordings of local potential from different pairs of electrodes. Multipolar catheters can be advanced to map the endocardial or the epicardial surface. A strong correlation between the scar area determined by electroanatomical mapping and the histopathological scar size has been demonstrated. A double-transeptal technique allows for an accurate definition of target sites. The complex scar architecture has been investigated by ultra-high-density mapping, let the identification of islets of heterogeneity where electrograms adjacent to the preserved myocardium have an higher incidence of late potentials. Pacing manoeuvres can easily be performed from any pair of electrode, to demonstrate the involvement of late potentials into the VT circuit. This strategy allows for a clear-cut validation of late potential abolishment, and may offer advantages to shorten procedural and fluoroscopy times. Large series are necessary to definitively assess the potential role of multielectrode mapping as a guide for the substrate ablation approach in post-myocardial infarction VT patients.