Endocardial Mapping Research Articles

Characterization of myocardial scars: Electrophysiological imaging correlates in a porcine infarct model

Definition of myocardial scars as identified by electroanatomic mapping is integral to catheter ablation of ventricular tachycardia (VT). Myocardial imaging can also identify scars prior to ablation. However, the relationship between imaging and voltage mapping is not well characterized. The purpose of this study was to verify the anatomic location and heterogeneity of scars as obtained by electroanatomic mapping with contrast-enhanced MRI (CeMRI) and histopathology, and to characterize the distribution of late potentials in a chronic porcine infarct model. In vivo 3-dimensional cardiac CeMRI was performed in 5 infarcted porcine hearts. High-density electroanatomic mapping was used to generate epicardial and endocardial voltage maps. Scar surface area and position on CeMRI were then correlated with voltage maps. Locations of late potentials were subsequently identified. These were classified according to their duration and fractionation. All hearts underwent histopathological examination after mapping. The total dense scar surface area and location on CeMRI correlated to the total epicardial and endocardial surface scar on electroanatomic maps. Electroanatomic mapping (average of 1,532 ± 480 points per infarcted heart) showed that fractionated late potentials were more common in dense scars (<0.50 mV) as compared with border zone regions (0.51 to 1.5 mV), and were more commonly observed on the epicardium. In vivo, CeMRI can identify areas of transmural and nontransmural dense scars. Fractionated late diastolic potentials are more common on the epicardium than the endocardium in dense scar. These findings have implications for catheter ablation of VT and for targeting the delivery of future therapies to scarred regions.

3D visualization of myocardial substrate using Delayed Enhancement MRI for pre-planning and guidance of ablation procedures of ventricular tachycardia

Background In patients with prior myocardial infarction, intra-scar surviving fibers may create conducting channels (CC) which are the substrate of most sustained monomorphic ventricular tachycardias (VT). These channels can be identified by endocardial voltage mapping. Recent studies show high correlation between information from endocardial voltage mapping and delayed-enhanced MRI (DE-MRI) images.

Mapeamento epicárdico da taquicardia ventricular sustentada em cardiopatias não isquêmicas

FUNDAMENTO: A complexidade dos circuitos reentrantes relacionados as taquicardias ventriculares diminui os indices de sucesso dos procedimentos de ablacao por radiofrequencia. OBJETIVO: Avaliar se o mapeamento epicardico com multiplos eletrodos realizado simultaneamente com o mapeamento endocardico auxilia na ablacao da taquicardia ventricular (TV) sustentada em pacientes com cardiopatia nao isquemica. METODOS: Vinte e seis pacientes com TV sustentada recorrente, sendo 22 (84,6%) com cardiopatia chagasica cronica, dois (7,7%) com cardiomiopatia dilatada idiopatica e dois (7,7%) portadores de displasia arritmogenica do ventriculo direito, foram submetidos a mapeamento epicardico com dois ou tres microcateteres, com 8 eletrodos cada, simultaneamente ao mapeamento endocardico convencional. Utilizou-se cateter com ponta de 4 mm para ablacao com radiofrequencia (RF) realizada durante a TV induzida. RESULTADOS: Das 33 TVs induzidas, 25 foram mapeadas e 20 tiveram sua origem definida. Onze com origem epicardica e 9 endocardica. A estimulacao ventricular programada nao induziu TV sustentada em 11 (42,0%) dos 26 pacientes apos a ablacao. Eventos como recorrencia da TV e morte ocorreram em 10,0% dos pacientes submetidos a ablacao com sucesso, e em 59,0% dos insucessos, em seguimento ambulatorial medio de 357 ± 208 dias. CONCLUSAO: Circuitos subepicardicos sao frequentes em pacientes com cardiopatia nao isquemica. O mapeamento epicardico com multiplos cateteres realizado simultaneamente com o mapeamento endocardico contribui para a identificacao destes circuitos em um mesmo procedimento.

Electrical storm originating from a left ventricular epicardial scar in a patient with completely normal endocardial voltage

We report a patient with non-ischemic dilated cardiomyopathy presenting with an electrical storm because of a poorly tolerated monomorphic ventricular tachycardia. Electroanatomical mapping revealed a scar restricted to the epicardium, whereas the endocardial voltage map was completely normal. Epicardial catheter ablation based on substrate mapping and limited pace and entrainment mapping eliminated the tachycardia.

Long-Term Outcomes of Combined Epicardial and Endocardial Ablation of Monomorphic Ventricular Tachycardia Related to Hypertrophic Cardiomyopathy

Monomorphic ventricular tachycardia (MMVT) is rare in patients with hypertrophic cardiomyopathy (HCM). There are limited data on the utility of catheter ablation for the treatment of MMVT in this population. This study details a series of case reports from multiple centers where combined epicardial-endocardial ablation was performed in a highly selected group of patients with HCM-related MMVT. The cohort consisted of 10 patients with HCM-related MMVT. Pericardial access was achieved using the percutaneous subxyphoid approach. Epicardial and endocardial ventricular 3D bipolar voltage maps were generated. Ablation sites were identified using a combination of entrainment, activation, late/fractionated potential, and pace mapping. Electrophysiological-identified epicardial scar was present in 8 (80%) patients, endocardial scar in 6 (60%), and no scar in 1 (10%). In the 5 patients with inducible, stable MMVT, 3 cases were successfully terminated with ablation from the epicardium and 1 from the endocardium. The case that failed catheter ablation required surgical cryoablation to abolish the incessant VT. In the remaining 5 patients, 4 underwent epicardial and endocardial ablation of sites with good pace maps and late/fractionated potentials. No ablation was performed in the remaining patient because of noninducibility and lack of identifiable scar. After 37±17 months (limits, 2 to 62 months; median, 37 months), the freedom from recurrent implantable cardioverter-defibrillator shocks was 78% (7/9 patients) in those who underwent ablation. In highly selected patients with HCM, combined epicardial and endocardial mapping and ablation is a feasible and reasonably efficacious option for MMVT if refractory to aggressive trials of antiarrhythmic drugs and antitachycardia pacing.

Successful Epicardial Catheter Ablation of a Septal Ventricular Tachycardia after Myocardial Infarction

A 55-year-old man underwent catheter ablation of ventricular tachycardia (VT) after anterior myocardial infarction. Although electrophysiological study suggested that the VT originated from the septum, biventricular endocardial irrigated radiofrequency ablation failed to interrupt the VT. Epicardial ablation at the site located halfway between the lesions in the right and left ventricles via a pericardial approach eliminated the VT, suggesting that the VT likely originated from the top of the septum. When VTs originating from the upper septum are refractory to endocardial ablation, epicardial mapping and ablation may be considered because only that site may be accessible with an epicardial approach.

Ultra High-Density Multipolar Mapping With Double Ventricular Access: A Novel Technique for Ablation of Ventricular Tachycardia

Ultra High-Density Multipolar Mapping With Double Ventricular Access. Analogous to the use of circular loop catheters to guide ablation around the pulmonary veins, it may be advantageous to use a multipolar catheter in the ventricle for rapid mapping and to guide ablation. We describe a technique using double access into the left ventricle for multipolar electroanatomic mapping and ablation of scar-mediated ventricular tachycardia (VT). Double access into the left ventricle was obtained via transseptal technique. Endocardial mapping was performed via the first transseptal sheath using a steerable duodecapolar catheter. Higher density mapping was performed in areas of dense scar (<0.5 mV) and border zone (0.5-1.5 mV). All late potentials (LPs) observed on the 20 poles were tagged and pacemapping was performed at these sites for comparison with the clinical or induced VT 12-lead template. If VT was hemodynamically tolerated, entrainment mapping was attempted at sites demonstrating diastolic activity. Ablation was performed through the second transseptal sheath with an open-irrigated catheter at target sites identified by LPs, pacemapping, and/or entrainment on the duodecapolar catheter. Seventeen patients (88% ischemic cardiomyopathy) underwent electroanatomic mapping and ablation with double transseptal access. The mean number of endocardial mapping points was 819 ± 357 with an average mapping time of 31 ± 7 minutes. The mean number of VTs induced was 2.8 ± 1.6, mean cycle length 418 ms ± 101. LPs were seen in all patients during endocardial mapping with the duodecapolar catheter. Good (56%) and perfect (44%) pacemaps were seen in all patients when performed. Concealed entrainment, guided by the earliest diastolic activity seen on the duodecapolar catheter, was demonstrated in 4 patients (24%). Acute success was achieved in 94% of patients with complete success in 47% and partial success in 47%. The intermediate success rate (free of VT recurrence) was 69%, with an average follow-up of 8 ± 3 months. Mapping and ablation of scar-mediated VT using a multipolar catheter results in ultra high-density delineation of the left ventricular substrate. A novel double ventricular access strategy has the potential to facilitate identification of LPs, pacemapping, and entrainment mapping.

Ventricular Tachycardia Originating from Apical Septum in a Case with Dilated Cardiomyopathy: Correlation of Electroanatomical Data with Post-Mortem Histology

Introduction: We report a 41-year-old male of pleomorphic ventricular tachycardia (VT) complicated with dilated cardiomyopathy, treated with RF ablation, followed by autopsy of the heart. Case Presentation: 12-lead ECG during one of VTs exhibited rS pattern in leads V1 to V6, consistent with septoapical origin. Bipolar endocardial voltage map revealed small zone of low voltage in the left ventricular (LV) apex. Good pacemap was obtained from the right ventricular (RV) apex, but was not obtained from the LV apex. Activation map revealed the earliest activation site in both RV and LV apex. No diastolic potentials during the ongoing VT were detected. The VT was terminated by several RF deliveries at LV apex, but remained inducible. On autopsy of the heart, scattered fibrosis was observed in midmyocardium of LV, and was more prominent in septum than in LV free wall. The lesions produced by RF delivery were non-transmural in RV septum (a depth of 6 mm) and LV free wall (2.5 mm). Conclusion: The VT originated from apical, intraseptal injured myocardium with a breakthough to the RV, which could not effectively ablate from either apex.

Ventricular Tachycardia Originating from Heart-Like Left Ventricular Diverticulum Diagnosed by Carto Merge System

A 67 year-old man was referred to our hospital because of pre-syncope and palpitation. The 12-lead ECG recorded during ventricular tachycardia (VT) showed a right bundle branch block and left superior axis QRS morphology, consistent with that of left basal posterior wall origin. After admission, multidetector Computed Tomography (MDCT) showed no finding of coronary artery but left ventricular (LV) diverticulum of the left basal posterior wall. In the electrophysiological study, endocardial voltage mapping during sinus rhythm revealed the presence of a low voltage area in the LV diverticulum. Isolated delayed potential was recorded between low and normal voltage at the edge of LV diverticulum. Pace mapping at the delayed potential recording site produced the same QRS morphology as that of clinical documented VT and PVCs. However, given the thin walls of the LV diverticulum, cardiac surgery under general anesthesia rather than radiofrequency application by the catheter was indicated and performed. After surgery, VT and the PVCs disappeared on 24-hr Holter ECG. The patient was discharged without antiarrhythmic therapy and had no cardiac events during 6 months follow-up. This case illustrates how the CARTOMERGE system can allow our precise understanding of 3D anatomy of LV, accurate risk assessment of catheter ablation and optimal therapeutic strategy for VT originating from LV anomaly.

Noninvasive Identification of Ventricular Tachycardia-Related Conducting Channels Using Contrast-Enhanced Magnetic Resonance Imaging in Patients With Chronic Myocardial Infarction: Comparison of Signal Intensity Scar Mapping and Endocardial Voltage Mapping

We performed noninvasive identification of post-infarction sustained monomorphic ventricular tachycardia (SMVT)-related slow conduction channels (CC) by contrast-enhanced magnetic resonance imaging (ceMRI). Conduction channels identified by voltage mapping are the critical isthmuses of most SMVT. We hypothesized that CC are formed by heterogeneous tissue (HT) within the scar that can be detected by ceMRI. We studied 18 consecutive VT patients (SMVT group) and 18 patients matched for age, sex, infarct location, and left ventricular ejection fraction (control group). We used ceMRI to quantify the infarct size and differentiate it into scar core and HT based on signal-intensity (SI) thresholds (>3 SD and 2 to 3 SD greater than remote normal myocardium, respectively). Consecutive left ventricle slices were analyzed to determine the presence of continuous corridors of HT (channels) in the scar. In the SMVT group, color-coded shells displaying ceMRI subendocardial SI were generated (3-dimensional SI mapping) and compared with endocardial voltage maps. No differences were observed between the 2 groups in myocardial, necrotic, or heterogeneous mass. The HT channels were more frequently observed in the SMVT group (88%) than in the control group (33%, p < 0.001). In the SMVT group, voltage mapping identified 26 CC in 17 of 18 patients. All CC corresponded, in location and orientation, to a similar channel detected by 3-dimensional SI mapping; 15 CC were related to 15 VT critical isthmuses. SMVT substrate can be identified by ceMRI scar heterogeneity analysis. This information could help identify patients at risk of VT and facilitate VT ablation.

Stepwise Approach of Endocardial and Epicardial Substrate Modification for Ventricular Tachycardia Late after Myocardial Infarction—The Importance of Infarction Site and Size—

Objectives: The purpose of this study was to assess the need of epicardial ablation for ventricular tachycardia (VT) late after myocardial infarction (MI). Methods: Substrate endocardial electroanatomic mapping was performed for VT late after MI. Arrhythmogenic substrate was defined as a low voltage are (<1.5 mV), or fractionated or late potentials during sinus rhythm. Endocardial ablation were performed, followed by epicardial mapping and ablation if no endocardial substrate was present or endocardial ablation failed. Results: 70 patients (63 male; age 66±10 years) with VT late after MI underwent ablation. 41 VTs in 30 patients with anterior MI and 64 VTs in 40 patients with postero-inferior MI were targeted. Acute success for targeted VTs was achieved in 68/70 (97%) patients, while in 11/70 (16%) patients faster VTs remained inducibile. Epicardial mapping and ablation was required in 6/70 (9%) patients demonstrating 7/105 VTs. All patients requiring epicardial access had postero-inferior MIs. Endocardial low voltage area in the patients required epicardial access was smaller than those in the remaining posteroinferior MI patients (23±19 cm2 vs. 68±40 cm2; p<0.05). Follow-up was not available for 7 patients. After the initial procedure, VT recurred in 30/63 (48%) patients during 23±17 months of follow-up. Conclusions: Epicardial mapping and ablation is rarely required in patients with small postero-inferior MI.

The Change of Preferential Internodal Pathways during Sympathetic Stimulation

Background: The preferential internodal pathways (INP), which impulses travel from the sinus to the AV node (AVN), have been contested. This study evaluated the INP at baseline and during sympathetic stimulation.Methods: Using 3-dimensional endocardial mapping, the conduction via INP and the earliest atrial activation site (EAS) were evaluated in 57 atrial fibrillation patients without sinus dysfunction (48 men, 54±12 years) during conscious anesthesia. Anterior, middle and posterior INPs were defined as the tracts travel via the Bachmann bundle, behind superior vena cava, and along the crista terminalis (CT) to the AVN, respectively.Results: At baseline, the location of unicentric EAS (n=42) was superior, mid and inferior parts of the CT in 28, 14 and 0 patients, respectively. The fastest INP was anterior and middle INP in 28 and 14 patients, respectively. During the isoproterenol infusion of 7–10 µg/min, 52 patients had unicentric EAS. The anterior and middle INP was the fastest INP in 43 and 9 patients, respectively. All patients having the superior CT as the EAS at baseline (n=28) and during isoproterenol infusion (n=43) had the anterior INP as the fastest INP. No patient had inferior INP as the fastest INP.Conclusions: The preferential INP was closely associated with the location of EAS. During sympathetic stimulation, the EAS was the superior CT, making the anterior INP as the fastest preferential conduction.

Accuracy of combined endocardial and epicardial electroanatomic mapping of a reperfused porcine infarct model: A comparison of electrofield and magnetic systems with histopathologic correlation

Contact mapping of the ventricle with NAVX has not been validated. This study sought to compare the accuracy of infarct mapping between NAVX and CARTO using a histopathologic gold standard. A closed-chest porcine infarction model was created by circumflex artery occlusion. After 4 to 12 weeks, 7 subjects underwent high-density endocardial and epicardial mapping using CARTO (Biosense Webster, Diamond Bar, California) and NAVX (St. Jude Medical, St. Paul, Minnesota) mapping systems. After mapping, animals were euthanized and histopathologic examination was used to quantify areas of scar at depths of 1 to 4 mm. Using a single-point acquisition approach with CARTO and a multipoint acquisition approach with the NAVX, endocardial and epicardial maps created using CARTO consisted of 360 ± 121 points performed in 54 ± 23 minutes/361 ± 90 points in 41 ± 13 minutes compared with 697 ± 132 points in 35 ± 8 minutes/1,303 ± 207 points in 30 ± 11 minutes using NAVX. At a 2-mm depth from the endocardial and epicardial surface, the mean scar area quantified by histopathology was 9.5 ± 8.7 cm(2) and 6.2 ± 4.8 cm(2), respectively. Correlation between histopathology and electroanatomic maps was excellent (r = 0.88, CARTO and 0.92, NAVX). Correlation between scar area determined by CARTO and NAVX was good (r = 0.88, P <.0001). Balloon occlusion-reperfusion of the circumflex artery creates a localized patchy infarction in the inferolateral wall. Multipolar mapping achieves higher density in a shorter period of time and increases the detection of late potentials. A strong correlation between CARTO and NAVX exists, and both systems demonstrate good correlation with histopathologic quantification of scar.

Value and limitations of electromechanical endocardial mapping in the assessment of global and regional left ventricular function and transmural extent of infarction: a comparison with cardiovascular magnetic resonance

To determine the relation between electromechanical endocardial mapping (EEM) and cardiac magnetic resonance (CMR) derived functional and viability parameters in patients with a large myocardial infarction. Forty-two patients with a large ST-elevation myocardial infarction underwent both EEM and CMR four months after primary percutaneous coronary intervention. EEM was performed to assess linear local shortening (LLS), unipolar voltage (UV) and bipolar voltage (BV). CMR cine imaging was performed to determine left ventricular global volumes, ejection fraction and regional function. Late gadolinium enhancement was used to assess size and transmural extent of infarction. Average LLS, UV and BV differed significantly between normal and dysfunctional segments (9.8 vs. 7.3, 11.8 vs. 9.7 and 3.3 vs. 2.8 for LLS, UV and BV respectively; p<0.001 for LLS and UV, p=0.006 for BV). In addition, average LLS, UV and BV, differed significantly between non-, subendocardial and transmural enhanced segments (10.8 vs. 8.8 vs. 5.0, 12.3 vs. 10.5 vs. 9.5 and 3.5 vs. 3.0 vs. 2.3 for LLS, UV and BV, respectively, p<0.001 for all variables). Although regional EEM data showed reasonable correlation with CMR, specific cut-off values for EEM parameters could not be established. EEM may be helpful in determining both the regional function and the transmural extent of infarction in patients with a large myocardial infarction. However, correlation with CMR parameters was moderate and exact cut-off values for EEM parameters could not be established. Further development of this potentially very useful modality is needed before it can be advocated for exact border-zone endocardial injection.

Electrophysiological Differences between the Epicardium and the Endocardium of the Left Atrium

Electrophysiological properties of the atrial endocardium compared to epicardium are not well understood. The purpose of this study was to compare the electrophysiological properties and vulnerability to arrhythmia induction from these regions. Transseptal endocardial and percutaneous epicardial mapping were performed in a porcine model (n = 7). Two opposing 4-mm electrophysiological catheters were positioned endocardially and epicardially. A circular mapping catheter (CMC) was positioned at the ostium of the common inferior pulmonary vein (CIPV) recording left atrial (LA)-PV potentials. Endocardial and epicardial effective refractory periods (ERPs) at two basic cycle lengths (CLs) of 600 and 400 ms were recorded from four anatomic locations (CIPV, LA appendage, right superior PV, and LA posterior wall). Atrial repetitive response (ARR) induction was also tested from endocardial and epicardial sites. Overall, 254 ERP measurements (mean 36.3 per animal) and 84 induction attempts (mean 12 per animal) were performed. The ERP was significantly shorter in the epicardium compared to the endocardium at basic CL of 400 ms (P = 0.006) but not at CL of 600 ms (P = 0.2). In addition, only the epicardium demonstrated ERP shortening when the CL of the basic drive was shortened (P = 0.03). ARR could be induced more often from the epicardium (P = 0.002) and fibrillatory activity with epicardial/endocardial dissociation was recorded (n = 3). Also, the earliest PV activation site on the CMC was noted to be different in 16.5% of cases during epicardial and endocardial pacing. The electrophysiological characteristics of the atrial epicardium are different from the endocardium with a shorter ERP and more frequent ARR induction by programed stimulation.

Accuracy of epicardial electroanatomic mapping and ablation of sustained ventricular tachycardia merged with heart CT scan in chronic Chagasic cardiomyopathy

As damage to coronary arteries is a potential complication of epicardial RF catheter ablation (EPRFCA), the procedure must be associated with coronary angiography. Chronic Chagasic cardiomiopathy (CCC) is a disease where epicardial VT are common. Eletroanatomic mapping merged with computed totmography (CT) scan data is a useful tool for mapping the endocardium, and its accuracy in guiding ablation on the epicardium was not adequately evaluated so far. Compare electronatomic map merged with Heart CT to fluoroscopy for epicardial ablation of CCC. Describe the distribution of the scars on CCC. We performed epicardial and endocardial mapping and ablation using CARTO XP V8 on eight patients and merged the map with coronary arteries CT scan using at least three landmarks. To compare the 3D image obtained with CARTO MERGE and the 2D fluoroscopic image obtained during the ablation procedure, we used computer graphic software (Inkscape™) in order to prove that the images were equivalent and to compare the distance between the catheter tip on fluoroscopy to catheter tip on 3D EA map. EPRFCA was successfully performed in all patients and they did not present recurrence for at least 3-month follow-up. The mean difference between the tip of the catheter on fluoroscopy and on the 3D model was 6.03 ± 2.09mm. Scars were present in the epicardium and endocardium and most of patients presented with posterior wall scars and RV scar. The combination of electroanatomic map and CT coronary artery scan data is feasible and can be an important tool for EPRFCA in patients with CCC and VT.

Isolated Potentials and Pace‐Mapping as Guides for Ablation of Ventricular Tachycardia in Various Types of Nonischemic Cardiomyopathy

In patients with prior infarction, isolated potentials (IPs) during sinus rhythm reflect fixed scar and often indicate sites critical for ventricular tachycardia (VT). The purpose of this study was to determine the value of IPs in conjunction with pace-mapping to guide VT ablation in patients with various types of nonischemic cardiomyopathy. Mapping and ablation of VT were performed in 35 consecutive patients (26 men, age 55 ± 13 years, ejection fraction 0.31 ± 0.14) with VT and various etiologies of nonischemic cardiomyopathy. Pace-mapping was performed at sites with low voltage. Radiofrequency energy was delivered at sites with concealed entrainment or matching pace-maps. One hundred ninety-five VTs (mean cycle length 363 ± 88 ms) were induced. Sites with prespecified ablation criteria displaying IPs during sinus rhythm were recorded in 21 of 35 patients (60%, IP-positive). In these patients, a total of 216 sites meeting prespecified ablation criteria were identified and 146 of 216 sites (68%) displayed IPs. Fifteen of 21 IP-positive patients (71%) no longer had inducible VT after ablation. In 14 of 35 patients, no sites with IPs where prespecified ablation criteria were met were identified (IP-negative) despite combined endocardial and epicardial mapping in 7 of 14 patients. Only 1 of 14 IP-negative patients (7%) no longer had inducible VT at the end of the ablation procedure. During a mean follow-up of 18 ± 13 months, 14 of 21 IP-positive patients (67%) remained arrhythmia-free, compared to 1 of 14 IP-negative patients (7%; P < 0.01). Half of the IP-negative patients had major adverse events due to recurrent arrhythmias, compared to none in IP-positive patients. IPs in conjunction with pace-mapping are helpful for identifying critical isthmus areas for ablation of VT in patients with various types of nonischemic cardiomyopathy. Patients with nonischemic cardiomyopathy in whom the arrhythmogenic substrate is characterized by IPs have a more favorable outcome than patients in whom IPs are absent.

Catheter Ablation of Ventricular Tachycardias Due to Forward and Reverse Propagation Across a Reentrant Circuit Inside a Nonischemic Biventricular Aneurysm

A 64-year-old recipient of implantable cardioverter defibrillator presenting with a 4.7 × 3.3 cm nonischemic, biventricular aneurysm developed multiple electrical storms due to ventricular tachycardia (VT) with 2 distinct QRS morphologies. Endocardial electroanatomical mapping revealed the presence of a low-voltage area corresponding to the aneurysm, where multiple delayed potentials were recorded. Activation mapping and entrainment pacing of both VT revealed the, respectively, forward and reverse propagation of the wavefront across a single reentrant circuit inside the ventricular aneurysm. Delivery of 3 applications of radiofrequency energy to a critical segment of the reentrant pathway eliminated both VT and the electrical storms.

Substrate Characterization and Catheter Ablation for Monomorphic Ventricular Tachycardia in Patients With Apical Hypertrophic Cardiomyopathy

VT Ablation in Apical Hypertrophic Cardiomyopathy. Monomorphic ventricular tachycardia (VT) is uncommon in apical hypertrophic cardiomyopathy (HCM). The purpose of this study was to define the substrate and role of catheter ablation for VT in apical HCM. Four patients with apical HCM and frequent, drug refractory VT (mean age of 46 ± 10 years, left ventricular [LV] ejection fraction; 54 ± 14%) underwent catheter ablation with the use of electroanatomic mapping. Endocardial mapping was performed in 4 patients and 3 patients underwent epicardial mapping. In 3 patients, VT was related to areas of scar in the apical LV where maximal apical wall thickness ranged from 14.5 to 17.8 mm, and 2 patients had apical aneurysms. Endocardial and epicardial substrate mapping revealed low voltage (<1.5 mV) scar in both endocardial and epicardial LV in 2 and only in the epicardium in 1 patient. Inducible VT was abolished with a combination of endocardial and epicardial ablation in 2 patients, but was ineffective in the third patient who had intramural reentry that required transcoronary ethanol ablation of an obtuse marginal vessel for abolition. The fourth patient had focal nonsustained repetitive VT from right ventricular outflow tract (RVOT), consistent with idiopathic RVOT-VT, that was successfully ablated. During follow-ups of 3-9 months, all patients remained free from VT. Monomorphic VT in apical HCM can be due to endocardial, epicardial or intramural reentry in areas of apical scar. Epicardial ablation or transcoronary alcohol ablation is required in some cases.

Epicardial Macroreentrant Ventricular Tachycardia Associated with a Left Ventricular Aneurysm

A 62-year-old man with severe coronary artery disease and a left ventricular aneurysm underwent catheter ablation of ventricular tachycardia (VT) with right bundle branch block QRS morphology. Endocardial bipolar voltage mapping with standard threshold settings demonstrated no low-voltage areas within the aneurysm. Catheter ablation of the epicardial surface of the aneurysm eliminated the VT. Endocardial bipolar voltage mapping with any other settings could not predict the site of the epicardial arrhythmogenic substrate whereas endocardial unipolar voltage mapping could. Endocardial unipolar voltage mapping may be helpful for predicting epicardial arrhythmogenic substrates.