Exploring postinfarction reentrant ventricular tachycardia with entrainment mapping

Ablation of ventricular tachycardia by isolating the critical site in a patient with arrhythmogenic right ventricular cardiomyopathy

We describe a patient with arrhythmogenic right ventricular cardiomyopathy in whom ventricular tachycardia (VT) was ablated by isolating a relatively large area of the critical site using catheter ablation. Endocardial mapping showed abnormal fragmented electrograms with delayed potential (DP) from an entire area of the aneurysm. Pace mappings from the aneurysm produced a QRS morphology identical to that of clinical VT. After catheter ablation was performed at the exit site of the VT critical area, programmed stimulation inside the aneurysm captured the DP but not the QRS complexes. These data suggest that VT can be ablated successfully by isolation of the critical area.

Catheter ablation for hemodynamically unstable monomorphic ventricular tachycardia

INTRODUCTION

Hemodynamic collapse precludes extensive catheter mapping to identify focal target regions in many patients with ventricular tachycardia (VT) associated with heart disease. This study tested the feasibility of catheter ablation of poorly tolerated VTs by targeting a region identified during sinus rhythm.

METHODS AND RESULTS

Ablation was attempted in five patients, ages 44 to 59 years, with left ventricular ejection fractions of 0.15 to 0.20 and poorly tolerated VT causing multiple implantable defibrillator therapies (6 to 30 episodes/month). VT was due to prior infarction in three patients and nonischemic cardiomyopathy in two. Target regions were sought that met the following criteria: (1) evidence of slow conduction from fractionated sinus rhythm electrograms and stimulus-QRS delays during pace mapping, and (2) evidence that the region contains the reentrant circuit exit from pace mapping. In 4 of 5 patients, a target region was identified and radiofrequency lesions applied. Ablation abolished all recurrences of VT in 3 of 4 patients during follow-up of 14 to 22 months. There were no complications.

CONCLUSION

Ablation of poorly tolerated VT is feasible in some patients by mapping during sinus rhythm and performing ablation over a region of identifiable scar that contains abnormal conduction and a presumptive VT exit.

Mapping and radiofrequency catheter ablation of the three types of sustained monomorphic ventricular tachycardia in nonischemic heart disease

INTRODUCTION

Sustained monomorphic ventricular tachycardia (VT) associated with nonischemic cardiomyopathy (CMP) is uncommon. Optimal approaches to catheter mapping and ablation are not well characterized, but they are likely to depend on the VT mechanism. The purpose of this study was to evaluate the mechanisms of sustained monomorphic VT encountered in nonischemic CMP and to assess the feasibility, safety, and efficacy of catheter radiofrequency ablation for treatment.

METHODS AND RESULTS

Twenty-six consecutive patients with nonischemic CMP referred for management of recurrent VT were studied. In 16 (62%) patients, VT was related to a region of abnormal electrograms consistent with scar and the response to pacing suggested a reentrant mechanism. In 5 (19%) patients, VT was due to bundle branch or interfascicular reentry. In 7 (27%) patients, the VT mechanism was focal automaticity, 4 of whom had evidence of tachycardia-induced CMP. After catheter ablation targeting parts of reentrant circuits, VT was not inducible in 8 (53%) of 15 patients with scar-related reentry, was modified in 5 (33%) patients, and still was inducible in 2 (13%) patients. Ablation was successful in 5 of 5 patients with bundle branch reentry and in 6 of 7 patients with a focal automaticity mechanism. Overall, catheter ablation abolished clinical recurrence of VT in 20 (77%) of 26 patients during a follow-up of 15 +/- 12 months.

CONCLUSION

Three different mechanisms of VT are encountered in patients with nonischemic CMP. The mapping and ablation approach varies with the type of VT. In this selected population, the overall efficacy was 77%.

Characteristics of electrograms recorded at reentry circuit sites and bystanders during ventricular tachycardia after myocardial infarction

OBJECTIVES

The purpose of this study was to determine the relation of isolated potentials (IPs) recorded during ventricular tachycardia (VT) to reentry circuit sites identified by entrainment.

BACKGROUND

Reentry circuits causing VT late after myocardial infarction are complex. Both IPs and entrainment have been useful for identifying successful ablation sites, but the relation of IPs to the location in the reentry circuit as determined by entrainment has not been completely defined.

METHODS

Data from catheter mapping of 70 monomorphic VTs in 36 patients with prior myocardial infarction were retrospectively analyzed. Entrainment followed by radiofrequency current (RF) ablation was performed at 384 sites. On the basis of entrainment, sites were classified as reentry circuit exit, central-proximal, inner or outer loop sites. Sites outside the circuit were divided into remote and adjacent bystanders.

RESULTS

Isolated potentials were recorded at 50% (51 of 101) of reentry circuit exit, central and proximal sites as compared with only 8% (11 of 146, p < 0.001) of inner loop and outer loop sites and only 1.8% (2 of 106) of remote bystander sites (p < 0.001). Isolated potentials were also present at 45% of adjacent bystander sites. At central and proximal sites the presence of an IP increased the incidence of tachycardia termination by RF to 47.5% from 24% (p = 0.05). At exit sites tachycardia termination occurred frequently regardless of the presence or absence of IPs (45% vs. 48%, p = NS). Isolated potentials at exit, central and proximal sites had a shorter duration at sites where ablation terminated VT than at sites without termination (20.9 +/- 9.6 ms vs. 35.7 +/- 15.3 ms, p < 0.001).

CONCLUSIONS

Isolated potentials are a useful guide to sites in the central-proximal region of the reentry circuit, but often fail to identify exit sites where ablation is successful. Entrainment and analysis of electrograms provide complementary information during mapping of VT.

Ablation of ventricular tachycardia in the setting of coronary artery disease

Ablation of reentrant ventricular tachycardia (VT) is an accepted therapy for certain patients with VT caused by coronary artery disease (CAD). Its use is currently limited to patients with sustained, monomorphic, hemodynamically tolerated VT. The use of entrainment in mapping reentrant VT has made possible increasingly accurate localization of critical sites on the reentrant pathway that are amenable to ablation. Recent work has examined the accuracy with which various mapping criteria are able to predict successful ablation of reentrant VT in patients with CAD. Other recent studies have investigated attempted ablation of all inducible VTs in patients with multiple VT morphologies. In the future, substrate mapping may make possible ablation of VT in patients with nonsustained or fast, hemodynamically unstable VTs, thus allowing VT ablation to become a first-line therapy for many patients with VT in the setting of CAD.

Ablation of ventricular tachycardia with a saline-cooled radiofrequency catheter: anatomic and histologic characteristics of the lesions in humans

INTRODUCTION

In animal models, active cooling of the electrode during radiofrequency (RF) ablation allows creation of larger lesions, presumably by increasing the power that can be delivered without coagulum formation. These RF lesions have not been characterized in human myocardium in regions of infarction and scarring.

METHODS AND RESULTS

Cooled-tip RF catheter ablation of ventricular tachycardias (VTs) was performed in two patients who had severe congestive heart failure and subsequently underwent cardiac transplantation. The first patient had four different monomorphic VTs. RF applications along the inferoseptal margin of a scarred region abolished all inducible VTs. The second patient had sarcoidosis involving the myocardium and four different inducible VTs. RF current applied at an inferobasal VT exit and at the right and left septa failed to abolish the VTs. The explanted hearts were examined at the time of cardiac transplantation 18 and 21 days later, respectively. Lesions extended to depths up to 7 mm, reaching clusters of myocardial cells deep to regions of fibrosis. Microscopically, the ablation sites contained coagulation necrosis with hemorrhage, surrounded by a rim of granulation tissue.

CONCLUSION

Saline-irrigated RF catheter ablation produces relatively large lesions capable of penetrating deep into scarred myocardium.

Entrainment/mapping criteria for the prediction of termination of ventricular tachycardia by single radiofrequency lesion in patients with coronary artery disease

BACKGROUND

A variety of mapping criteria have been proposed to localize critical sites at which radiofrequency (RF) can predictably terminate reentrant ventricular tachycardia (VT) caused by coronary artery disease. The purpose of this study was to determine the accuracy of using a combination of 3 mapping criteria in predicting termination of VT by a single RF lesion.

METHODS AND RESULTS

Fifteen consecutive patients with coronary artery disease and recurrent sustained VT underwent an attempted RF ablation of 20 monomorphic VTs. Successful termination of VT by a single RF lesion was predicted if all the following mapping criteria were met: (1) an exact QRS match in the 12-lead ECG during entrainment; (2) a return cycle length </=10 ms of the VT cycle length; (3) presystolic potentials (<70% of VT cycle length) with an activation time to the QRS within 10 ms of the stimulus to QRS. Inability to meet these 3 criteria was considered to predict failure of VT termination by RF energy at that site. RF ablation was applied to 44 left ventricular sites in 20 VTs at which at least 1 of the mapping criteria was met. VT was terminated with a single RF lesion in 19 of 19 sites meeting all criteria; RF failed to terminate VT at 24 of 25 sites at which all 3 criteria were not met (P<0.0005).

CONCLUSIONS

To maximize success and minimize the number of RF lesions in patients with infarct-related VT, all the above 3 mapping criteria should be met before the application of RF energy.

Histopathologic effects of radiofrequency catheter ablation in previously infarcted human myocardium

INTRODUCTION

The use of catheter-based radiofrequency (RF) ablation for the treatment of ventricular tachyarrhythmias due to previous myocardial infarction has been steadily increasing. The histopathologic changes caused by this technique are not well described in humans.

METHODS AND RESULTS

Three patients with hemodynamically tolerated ventricular tachycardias (VTs) due to previous myocardial infarction underwent endocardial mapping and catheter based RF ablation. All patients received between 5 and 11 RF lesions each of 60-second duration. One patient underwent myocardial resection of a left ventricular aneurysm 1 day following RF ablation, one expired 7 days after RF ablation, and one expired 9 months after RF ablation. None of the deaths occurred as a result of RF ablation. Pathologic specimens obtained early after RF ablation revealed areas of focal acute inflammation and fibrin deposition. Later specimens revealed several focal areas of fibrosis and granulation tissue. Specimens obtained late after RF ablation revealed a dense band of fibrosis, measuring 17 x 17 x 5 mm (1,250 mm3).

CONCLUSION

Catheter-based RF ablation of ischemic VT in humans causes lesions that initially resemble coagulation necrosis. This is followed by the development of an inflammatory infiltrate and, finally, the development of fibrosis. Repeated application of RF ablation may result in much larger lesions than have been previously reported.

Clinical and electrophysiologic features of idiopathic left ventricular aneurysm with sustained ventricular tachycardia

We examined 10 patients with idiopathic left ventricular (LV) aneurysm with sustained ventricular tachycardia (VT) (Id-An group), and compared them with those in 16 age- and sex-matched patients who had postinfarction aneurysm and VT (MI-An group) to clarify detailed clinical and electrophysiologic characteristics of idiopathic LV aneurysm. The clinical and laboratory data and results of electrocardiography, electrophysiologic, and morphologic examinations in the two groups were compared. In the Id-An group, the LV aneurysms were located more often at the posterior and/or inferior wall, while in the MI-An group, they were more often located at the anterior and/or apical wall (P<0.001). The LV end-diastolic volume index was significantly smaller and the LV ejection fraction was significantly higher in the Id-An group (P<0.001). The size of the aneurysm and the area with abnormal electrograms in the Id-An group were significantly smaller than those in the MI-An group (P<0.005 and P<0.001, respectively). The inducibility of VT was high in both groups, and ventricular pacing during VT showed entrainment phenomenon in most of the patients. Thus, in both groups, the abnormal electrograms were closely associated with the wall motion abnormality, and reentry was suggested as the mechanism of VT. In the Id-An group, since the lesions were anatomically and electrophysiologically confined to the posterior and/or inferior wall, the global LV function was more well preserved compared with the MI-An group.

Catheter ablation of ventricular tachycardia in patients with right ventricular dysplasia: Identification of target sites by entrainment mapping techniques

OBJECTIVE

To identify target sites for radiofrequency ablation of ventricular tachycardia (VT) by entrainment mapping techniques in patients with arrhythmogenic right ventricular dysplasia.

METHODS

Entrainment mapping and radiofrequency ablation of eight VTs was performed in seven patients. Radiofrequency ablation was applied at 31 reentry circuits sites that were classified based on findings during entrainment.

RESULTS

By entrainment criteria the 31 sites were classified as: exit sites (n = 12), proximal sites (n = 6), and outer loop sites (n = 13). Radiofrequency current application terminated VT at 7 of 31 sites: 2 of 12 exit sites (17%), 4 of 6 proximal sites (67%), and 1 of 13 outer loop sites (8%).

CONCLUSION

Radiofrequency ablation terminated VTs most often at sites proximal to the exit as opposed to outer loop sites and exit sites (P = 0.05). The critical isthmus for ablation of VT in right ventricular dysplasia often may be distant to the exit.

Mid-diastolic potential is related to the reentrant circuit in a patient with verapamil-sensitive idiopathic left ventricular tachycardia

We report a case of verapamil-sensitive idiopathic ventricular tachycardia in which a mid-diastolic potential (MDP) 45 msec preceding the Purkinje potential (P potential) was recorded. Pacing during the tachycardia caused concealed entrainment, and the stimulus-QRS interval was equal to the P potential-QRS interval. The interval between the last pacing stimulus and the next P potential (postpacing interval) was longer than the ventricular tachycardia cycle length, but the MDP was orthodromically activated. These findings suggest that the MDP was on the reentrant circuit and the P potential was not on the reentrant circuit, but a bystander.

Entrainment mapping and radiofrequency catheter ablation of ventricular tachycardia in right ventricular dysplasia

OBJECTIVES

The purpose of this study was to determine if entrainment mapping techniques and predictors of successful ablation sites previously tested in coronary artery disease can be applied to ventricular tachycardia (VT) in arrhythmogenic right ventricular dysplasia (ARVD).

BACKGROUND

VT in ARVD has not been well characterized. Reentry circuits in areas of abnormal myocardium are the likely cause, but these circuits have not been well defined.

METHODS

Mapping of 19 VTs in 5 patients with ARVD was performed. At 58 sites pacing entrained VT and radiofrequency current (RF) was applied to assess acute termination of VT.

RESULTS

Sites classified as exits, central/proximal, inner loop, outer loop, remote bystander and adjacent bystander were identified by entrainment criteria. The reentrant circuit sites were clustered predominantly around the tricuspid annulus and in the right ventricular outflow tract (RVOT). RF ablation acutely terminated VT at 13 sites or 22% of the applications. Of the 19 VTs, eight were rendered noninducible and three were modified to a longer cycle length. In 2 patients ablation at a single site abolished two VTs.

CONCLUSION

VT in ARVD shows many of the characteristics of VT due to myocardial infarction. Entrainment mapping techniques can be used to characterize reentry circuits in ARVD. The use of entrainment mapping to guide ablation is feasible.

Radiofrequency catheter ablation of ventricular tachycardia after myocardial infarction

BACKGROUND

Patients with ventricular tachycardia (VT) after myocardial infarction often have multiple morphologies of inducible VT, which complicates mapping and is viewed by some as a relative contraindication to ablation. Attempting to identify and target a single "clinical" VT is often limited by inability to obtain 12-lead ECGs of VTs that are terminated emergently or by defibrillators. This study assesses the feasibility of ablation in patients selected without regard to the presence of multiple VTs by targeting all VTs that allow mapping.

METHODS AND RESULTS

Radiofrequency catheter ablation targeting all inducible monomorphic VTs that allowed mapping was performed in 52 patients with prior myocardial infarction. Antiarrhythmic drug therapy had failed in 41 (79%) patients including amiodarone in 36 (69%) patients. An average of 3.6+/-2 morphologies of VT were induced per patient. More than 1 ablation session was required in 16 (31%) patients. Complications occurred in 5 (10%) patients, including 1 (2%) death caused by acute myocardial infarction. During follow-up 59% of patients continued to receive amiodarone; 23 (45%) had implantable defibrillators. During a mean follow-up of 18+/-15 months (range 0 to 51 months) 1 patient died suddenly, 2 died from uncontrollable VT, and 5 died from heart failure. Three-year survival rate was 70+/-10%, and rate for risk of VT recurrence was 33+/-7%.

CONCLUSIONS

Radiofrequency catheter ablation controls VT that is sufficiently stable to allow mapping in 67% of patients despite failure of antiarrhythmic drug therapy and multiple inducible VTs. However, ablation was largely adjunctive to amiodarone and defibrillators in this referral population.

Identification and ablation of macroreentrant ventricular tachycardia with the CARTO electroanatomical mapping system

Monomorphic ventricular tachycardias associated with regions of scar are most commonly due to reentry. Catheter based techniques have recently been described for mapping of reentry circuits. Fluoroscopic methods have obvious limitations when attempting to map large ventricular reentry circuit and localize target-sites of radiofrequency ablation. Three-dimensional right ventricular endocardial mapping was performed in a 38-year-old patient with ventricular tachycardia 28 years after surgical correction of tetralogy of Fallot by using the CARTO electroanatomical system. The map of electrogram voltage showed low amplitude electrograms over the anterior wall of the right ventricle extending into the right ventricular outflow tract, consistent with the location of the ventriculotomy scar. Recording of local activation time was combined with entrainment mapping to define the macroreentrant circuit during ventricular tachycardia. Since the activation propagated through a broad path around the right ventriculotomy scar, ablation was performed by creating a line of block, which was facilitated by tagging of the lesion sites on the endocardial activation map. Large ventricular reentry circuits can be identified and interrupted by creation of a line of block to interrupt a broad path. A practical approach to mapping combining analysis of electrogram voltage, activation sequence, and entrainment is presented.