Radiofrequency Catheter Ablation of Ventricular Tachycardia Late After Myocardial Infarction

Ablation of VT After MI. Radiofrequency catheter ablation is a promising method for controlling ventricular tachycardia (VT) due to prior myocardial infarction. Limitations of mapping and ablation techniques have largely restricted its use to selected patients who have hemodynamically tolerated sustained monomorphic VT that allows catheter mapping. Multiple monomorphologies of VT, which are usually present, often complicate the ablation procedure and interpretation of ablation effects. Ablation is generally restricted to experienced centers and is usually reserved for patients who have failed other therapies. Despite these difficulties, successful ablation can he life-saving in patients with incessant VT and can markedly improve quality of life with frequent shocks from implantable defibrillators.     

Ventricular Tachycardia After Myocardial Infarction: From Arrhythmia Surgery to Catheter Ablation

Ablation of Ventricular Tachycardia. Ventricular tachycardia due to prior myocardial infarction is caused by reentry. Intraoperative mapping at the time of arrhythmia surgery has shown that the reentry circuits arc diverse in size and location. Many circuits are large, extending over several square centimeters. Endocardial excision guided by activation sequence mapping, fractionated sinus rhythm electrograms, or visual identification of scarred subendo-cardium renders 69% to 95% of patients free from inducible ventricular tachycardia, but with an operative mortality that exceeds 8%, at most centers. Catheter ablation is difficult due to limitations of catheter mapping, relatively small size of lesions produced with current techniques, and limited access to intramural and epicardial portions of the reentry circuits. Many problems need to be overcome for catheter ablation to achieve success comparable to that of surgery. At present, only hemodynamically tolerated ventricular tachycardias can he mapped. Progress is being made, and it is likely that catheter ablation will become a viable therapy for subgroups of patients with postmyocardial infarction ventricular tachycardia.     

Ventricular Mapping During Atrial and Right Ventricular Pacing: Relation of Electrogram Parameters to Ventricular Tachycardia Reentry Circuits After Myocardial Infarction

INTRODUCTION: Ventricular tachycardia (VT) late after myocardial infarction is usually due to reentry in the border zone of the infarct area. Identification of critical parts of the VT reentry circuit by catheter mapping without needing to induce VT is a desirable goal for VT ablation. The aim of this study was to develop a model to predict reentry circuit locations based on characteristics of sinus or paced electrograms and pace mapping (PM) recorded from the infarct region. METHODS: Left ventricular electroanatomic mapping with the CARTO mapping system was performed in 16 male patients with recurrent VT late after myocardial infarction. A total of 1072 left ventricular sites were recorded during atrial pacing (AP) and right ventricular pacing (RVP), and the corresponding electrograms were analyzed for their local activation time (LAT), onset (ONS), end (END), duration (DUR), and amplitude (AMP) in each pacing sequence. At 1041 of these sites, PM was performed; the resulting stimulus to QRS intervals (S-QRS) was determined at 931 sites, the remaining 110 sites did not capture. All the obtained parameters were compared with the location of 18 ablation target areas with a radius of 2 cm defined by success of radiofrequency (RF) ablation or entrainment during VT, or both. RESULTS: Of 1072 sites, 227 (21%) were in the target and 845 (79%) were outside the target. All parameters were significantly different (p < 0.05) in AP and in RVP between inside and outside the target in a univariate analysis. In a multivariate analysis LAT, END, DUR, and AMP in AP, END and AMP in RVP, and S-QRS were independent predictors for the target (p < 0.05). A combination of selected parameters of these predictors (DUR in AP, AMP in RVP, and S-QRS) had a specificity of 64% with a sensitivity of 80% for the target. CONCLUSION: The observations suggest that ablation guided by a combination of abnormal electrograms in different rhythms can be useful to ablate VT and reduce the necessity of VT induction. Anatomically fixed regions of block may be important for reentry and be identifiable during sinus rhythm.     

Preferential Locations for Critical Reentry Circuit Sites Causing Ventricular Tachycardia After Inferior Wall Myocardial Infarction

Reentrant VT Post MI. Introduction : For relatively slow monomorphic ventricular tachycardia (VT) after myocardial infarction, entrainment can be used to identify reentry circuit "isthmus sites" (exit sites and sites proximal to the exit) where radioifrequency (RF) catheter ablation has the greatest likelihood of interrupting reentry. Similarities in coronary and ventricular anatomy may cause such sites to form in preferential locations. The objective of this study is to determine if there are preferential locations for reentry circuit isthmus regions in chronic inferior wall infarctions causing VT.
Methods and Results : Catheter mapping and RF catheter ablation was performed in 21 patients with an old inferior wall myocardial infarction and VT. The inferior wall was divided into 9 anatomic regions: 3 apical, 3 mid, and 3 basal segments. Of 46 different VTs, an endocardial isthmus site was identified in one or more zones in 28 (61%), with 10 VTs having isthmus sites in two or more adjacent regions. Isthmus zones were found in a basal region of the left ventricle in 24 (86%) of 28 VTs, in a mid segment in 9 (32%) VTs, and in an apical segment in 1 (4%) (P = 0.002). Of 30 RF current applications that terminated VT, 21 (70%) were at basal isthmus sites.
Conclusion : The high prevalence of endocardial isthmus zones near the base of the left ventricle suggests that the mitral annulus often plays a role in defining the margins of reentry circuits that cau.se relatively slow VTs after inferior wall myocardial infarction.     

冠心病心肌梗死后室性心律失常经射频导管消融的进展

冠心病心肌梗死后室性心律失常包括急性和陈旧性心肌梗死后的室性心律失常,可导致心功能恶化、猝死、生活质量下降等不良后果,近年来由于对其发病机制的进一步了解,同时在应用心脏三维标测系统引导心肌梗死后室性心律失常的标测和消融、经心外膜标测和消融室性心律失常和应用盐水灌注导管消融等方面有很大进展,心肌梗死后室性心律失常的经射频导管消融已取得较好效果。     

Retrograde Purkinje Potential Activation During Sinus Rhythm Following Catheter Ablation of Idiopathic Left Ventricular Tachycardia

Idiopathic Left VT and Purkinje Potentials . We describe two patients with idiopathic left ventricular tachycardia that were cured by radiofrequency catheter ablation. Tachycardia was inducible by ventricular stimulation and was verapamil sensitive. Two distinct presystolic potentials (PI and P2) were recorded during tachycardia in the mid-septal or inferoapical area, but only one potential (P2) was recorded during sinus rhythm. After catheter ablation at this site, the PI potential was noted after the QRS complex during sinus rhythm, while the P2 was still observed before the QRS complex. The P1 potential showed a decremental property during atrial or ventricular pacing. These data suggest that Purkinje tissue with decremental properties was responsible for the tachycardia mechanism, and that the reentry circuit involving this tissue is likely to be of considerable size.     

Relative Timing of Isolated Potentials During Postinfarction Ventricular Tachycardia and Sinus Rhythm

BACKGROUND: In postinfarction patients, isolated potentials separated by an isoelectric segment from the ventricular electrogram indicate areas of block. Isolated potentials can be recorded during both sinus rhythm and ventricular tachycardia (VT). In an attempt to differentiate bystander pathways from critical sites within a reentry circuit, we compared the relative timing of isolated potentials during VT and sinus rhythm. METHODS: In 19 patients (mean age 68 +/- 6 years) with postinfarction VT who were referred for VT ablation, mapping was performed in the presence and absence of VT. Forty-three sites at which there was concealed entrainment during 35 VT's (mean cycle length 469 +/- 74 ms) displayed an isolated potential separated from the main portion of the ventricular electrogram by an isoelectric segment of >/=30 msec in the presence and absence of VT. The interval between the ventricular electrogram and the isolated potential was measured during VT and baseline rhythm, and the absolute difference (DeltaIPI) was calculated. The DeltaIPI was significantly greater at effective ablation sites (119 +/- 69 ms) than at ineffective ablation sites (30 +/- 28 ms, p < 0.001). The positive predictive value of a DeltaIPI > 85 ms for an effective ablation site was 100%. CONCLUSION: At sites of concealed entrainment, an absolute difference >85 ms between the isolated potential intervals during sinus rhythm and VT is highly specific for a critical area of the VT reentry circuit in post-infarction patients.     

Effect of Radiofrequency Catheter Ablation of Ventricular Tachycardia on Left Ventricular Function in Patients with Prior Myocardial Infarction

Introduction: Successful RF ablation of VT late after MI can involve multiple applications and long lines of RF lesions. The impact on left ventricular function is potentially important, but not well defined. Quantitative echocardiography was used to determine the effect of radiofrequency (RF) ablation on left ventricular function in patients with ventricular tachycardia (VT) after myocardial infarction (MI). Methods and Results: In 62 patients (55 men; age 67 ± 1.1 yr.) who underwent RF ablation for VT late after MI, left ventricular ejection fraction (LVEF) was quantified from digitized echocardiograms performed 1 week before and <72 hours after ablation. Patients received a mean of 25.6 ± 2.2 (range of 3–98) RF lesions. The LVEF pre- and post-ablation did not differ for the group (pre-LVEF 29.8 ± 11.9% vs. post-LVEF 29.5 ± 11.2%, p = 0.626), or for the 30 patients who received >25 RF lesions (Pre-LVEF 28.5 ± 11.1% vs. Post-LVEF 28.1 ± 10.8%, p = 0.74) or for the 7 patients who received >40 RF lesions (Pre-LVEF 29.9 ± 12.7% vs. Post-LVEF 29.2 ± 6.2%, p = 0.84). Although LVEF did not change for the group, LVEF increased >5% in 12/62 (19.4%) pts and decreased 5% in 14/62 (22.5%) pts. Patients with a decrease in EF did not differ from the remaining patients with respect to age, gender, number of RF lesions, or use of a cooled RF catheter, but did have a better initial EF (38.8 ± 12.2% versus 27.2 ± 10.6%, p = 0.001). Conclusion: Multiple RF ablation lesions confined to infarct regions do not measurably affect LV function, but a cautious approach, confining ablation lesions to areas of scar, as was attempted in this study, seems prudent.     

Magnetic Resonance Mapping of Catheter Ablation Lesions After Post-Infarction Ventricular Tachycardia Ablation

ObjectivesThis study sought to describe cardiac magnetic resonance (CMR) characteristics of ablation lesions within post-infarction scar.BackgroundChronic ablation lesions created during radiofrequency ablation of ventricular tachycardia (VT) in the setting of prior myocardial infarction have not been described in humans.MethodsSeventeen patients (15 men, ejection fraction 25 ± 8%, 66 ± 6 years of age) with CMR imaging prior to repeat ablation procedures for VT were studied. Electroanatomic maps from first-time procedures and subsequent CMR images were merged and retrospectively compared with electroanatomic maps from repeat procedures.ResultsThe delay between the index ablation procedure and the CMR study was 30 ± 29 months. Late gadolinium–enhanced CMR revealed a confluent nonenhancing subendocardial dark core within the infarct-related scar tissue in all patients. Intracardiac thrombi were ruled out by transthoracic and intracardiac echocardiography. These core lesions matched the distribution of prior ablation lesions, and corresponded to unexcitable areas at repeat procedures.ConclusionsAblation lesions can be detected by CMR after VT ablation in post-infarction patients and have a different appearance than scar tissue. These lesions can be observed many months after an initial ablation.     

射频消融室性早搏治疗特发性和心肌梗死后恶性室性心动过速

报道射频消融室性早搏 (简称室早 )治疗特发性或心肌梗死 (MI)后恶性室性心动过速 (VT)各 1例。例 1女性 2 6岁 ,因阵发性心悸 1年 ,加重伴晕厥 4天入院。动态心电图示频发单形室早和短阵VT。无器质性心脏病证据。入院后第 3天无诱因出现意识丧失 ,持续约 2min自行缓解 ,心电图示多形性VT ,导致VT的室早形态与临床中频发室早相同。例 2男性 6 4岁 ,急性广泛前壁MI半个月后出现VT ,尽管经冠状动脉血运重建、纠正心力衰竭、多种抗心律失常药物等治疗 3个月 ,VT仍频繁发作 ,VT发作时伴明显血流动力学障碍 ,有时转为心室颤动 ,多需直流电复律。 2例消融术中均出现频发室早 ,形态与临床上诱发VT的室早形态相同。例 1心室猝发刺激诱发出多形性VT伴阿 斯综合征发作。例 2心室程序电生理刺激可诱发出 4种形态持续性VT。例 1结合激动和起搏标测 ,在右室流出道消融室早成功 ;例 2在左室间隔部向右室凸出的室壁瘤周围标测到室早时提前体表QRS波 5 0ms的Purkinje纤维电位 ,在此处消融室早成功。例 1随访 2 1个月无晕厥。例 2术后继续口服抗心律失常药物治疗 ,随访 10个月无晕厥和持续性VT。结论 :在部分特发性或急性MI患者中消融诱发VT的室早可能根治恶性VT。     

Anterior Q-Wave Infarction Complicating Attempted Catheter Electrode Ablation of Ventricular Tachycardia

This report describes an attempt to treat recurrent ventricular tachycardia by catheter electrode ablation. The procedure failed to control the arrhythmia and resulted in a Q-wave anteroseptal myocardial infarction. The potential complications of catheter electrode ablation in the normal ventricle are emphasized.     

Analysis During Sinus Rhythm of Critical Sites in Reentry Circuits of Postinfarction Ventricular Tachycardia

Background: Critical sites within reentry circuits of postinfarction ventricular tachycardia (VT) were identified during sinus rhythm (SR) and VT to determine whether electrogram characteristics during SR may be helpful in identifying successful ablation sites. Methods: In 33 patients (mean age 67 ± 11 yrs) with prior infarction, mapping and radiofrequency (RF) catheter ablation of 57 hemodynamically-tolerated VT's (cycle length 478 ± 96) were performed. The morphologies of electrograms (EGM) at sites of concealed entrainment (CE) were compared during SR and VT. RF energy was delivered at 94 sites (51 successful and 43 unsuccessful ablation sites). Results: During SR, isolated potentials (IP), but not late potentials (LP) recorded via the mapping catheter, were associated with successful ablation. At 29/39 sites with an IP during sinus rhythm, an isolated diastolic potential (IDP) also was present during VT, whereas at 4 sites IP's were present only during SR (p < 0.001). At 11/29 sites where isolated potentials were present during SR and VT, the morphology of the isolated potential during VT and SR was similar; and all but one of these sites were successful ablation sites (p = 0.01). The EGM amplitude during VT correlated with the amplitude during SR (R = 0.9, p < 0.001). An identical pacemap was present during SR at 33/94 sites; this was not associated with successful ablation. Conclusion: SR mapping may be helpful in identifying critical sites of reentry in postinfarction VT. At sites within the reentry circuit, characteristics of sinus rhythm EGM's that are associated with successful ablation include the presence of IP's, but not the presence of LP's.     

Ventricular Late Potentials Are Associated with the Presence of Viable Myocardium After Anterior Myocardial Infarction

Background: The aim of the study was to evaluate the relationship between myocardial viability (MV) detected by Tl‐201 rest/redistribution protocol (RR‐SPECT) and the presence of ventricular late potentials (VLPs) in acute myocardial infarction (AMI). We analyzed signal‐averaged ECGs (SAECGs) in 28 patients (age 57 ± 10 years) with a first anterior AMI within 48 hours of symptoms (SAECG1) and prior to discharge (SAECG2). VLPs were defined according to the presence of filtered QRS (QRS‐D) > 114 ms and duration of low amplitude signals (LAS) a 30 ms or root mean square voltage (RMS40) < 25 μ;V, using a 25‐Hz filter, or a duration of LAS > 39 ms or RMS40 < 20 μ;V, using a 40‐Hz filter. RR‐SPECT was performed 17 ± 6 days after AMI. Segments were considered viable when counts were > 60% in early images or when a fill‐in > 10% was detectable on delayed images of those segments with a first count between 31% and 59%. Methods: Patients were divided into two groups: with MV (group 1 = 16 patients) if almost one third of segments appeared to be viable; without MV (group 2 = 12 patients). No difference was found between the two groups in SAECG1, whereas, using a 25‐Hz filter, a greater QRS‐D (106.6 ± 13.5 vs 93.5 ± 6 ms) and LAS (31.2 ± 8.7 vs 18.1 ± 6.4 ms) as well as a smaller RMS40 (43 ± 33.5 vs 71.3 ± 30.4 μ;V) characterized the SAECG2 of group 1. Sensitivity and specificity of VLPs in detecting MV were 31% and 100%. When using cut‐off values derived from median distribution of the population (QRS‐D & 99 ms, LAS a 24 ms and RMS40 > 51 μ;V), sensitivity raised to 75% and specificity was 92% with a positive and negative predictive value of 92% and 73%. Conclusions: The presence of MV is associated with a greater incidence of VLPs. SAECG performed at the time of discharge may facilitate the identification of patients with μ;V after anterior AMI.     

Role of Epicardial Mapping in Catheter Ablation of Postmyocardial Infarction Ventricular Tachycardia

The role of epicardial mapping for radiofrequency (RF) catheter ablation of postmyocardial infarction monomorphic ventricular tachycardia (VT) is still under investigation. We present two septuagenarian patients with a history of myocardial infarction, poor left ventricular function, and drug-refractory monomorphic VT who were treated with RF catheter ablation. The first patient had a history of myocardial infarction, left ventricular aneurysm, and mitral valve replacement complicated by recurrent drug refractory VT and congestive heart failure. The second patient had ischemic cardiomyopathy and VT and was implanted with a cardioverter defibrillator and subsequently suffered repeated episodes of VT refractory to multiple antiarrhythmic drugs. In both patients, coronary sinus mapping was performed with a multipolar catheter as endocardial mapping did not reveal satisfactory sites for ablation. Epicardial catheter mapping provided stable electrograms and identification of areas of slow conduction during VT. RF lesions guided by epicardial mapping resulted in successful ablation of VT and no recurrence at long-term follow-up. This report emphasizes the potential usefulness of coronary sinus mapping as an adjuvant to endocardial mapping to guide VT ablation.     

Functional Late Potential Analysis With Exercise Testing to Identify Patients Prone to Ventricular Tachycardia After Myocardial Infarction

Objective: Exercise induced ischemia or heart rate acceleration may unmask late potentials or provoke functional changes, which might be important factors to improve the low positive predictive value of late potential analysis at rest for postinfarction risk stratification. However, methodological refinements are required to detect late potentials with exercise. Methods: We, therefore, investigated the surface-electrocardiogram in 100 patients after myocardial infarction (50 with sustained ventricular tachycardia [group I], 50 patients without ventricular arrhythmias [group II], and in 15 normals before and immediately after bicycle exercise test using Spectrotemporal Mapping (STM) with fast Fourier transform (FFT) and Simson method and introduced selective signal averaging. Results: In group I, 30 out of 50 patients showed late potentials at rest, after selective signal averaging also recognizable immediately after exercise in all of these patients, however, with a time-shift of 18 ± 13 ms into the ST-segment. Twelve out of 50 patients of group I with only transient late potentials tended to have inducible and recurrent ventricular tachycardia with a shorter cycle length. In group II, 4 out of 50 patients had late potentials at rest and 2 out of 46 patients developed them during exercise. Transient pathological Simson method was associated with transmural ischemia. Conclusions: Thus, detection of the effects of exercise on late potential analysis is possible with selective signal averaging immediately after exercise. Exercise unmasks late potentials not detectable at rest by their time-shift into the ST-segment. Using this method, patients that would have been lost with conventional late potential analysis, could be identified.