Outcomes of Catheter Ablation of Ventricular Tachycardia in the Setting of Structural Heart Disease.

Sustained ventricular tachycardias are common in the setting of structural heart disease, either due to prior myocardial infarction or a variety of non-ischemic etiologies, including idiopathic dilated cardiomyopathy, hypertrophic cardiomyopathy, and arrhythmogenic right ventricular cardiomyopathy. Over the past two decades, percutaneous catheter ablation has evolved dramatically and has become an effective tool for the control of ventricular arrhythmias. Single and multicenter observational studies as well as several prospective randomized trials have begun to investigate long-term outcomes after catheter ablation procedures. These studies encompass a wide range of mapping and ablation techniques, including conventional activation mapping/entrainment criteria, substrate modification guided by pacemapping, late potential and abnormal electrogram ablation, scar de-channeling, and core isolation. While large-scale, multicenter prospective randomized clinical trials are somewhat limited, the published data demonstrate favorable outcomes with respect to a reduction in overall ventricular tachycardia (VT) burden, reduction of implantable cardioverter defibrillator (ICD) shocks, and discontinuation of anti-arrhythmic medications across varying disease subtypes and convincingly support the use of catheter ablation as the standard of care for many patients with VT in the setting of structural heart disease.

Ablation of ventricular tachycardia.

Ablation is an important management tool for the treatment of ventricular arrhythmias. Even at experienced centers ventricular tachycardia ablation carries a minor but significant risk for potential complications, including vascular and thromboembolic complications, air embolism, volume overload and the precipitation of congestive heart failure, cardiac tamponade from catheter perforation or from steam pop with RF energy delivery, valve or subvalvular support structure disruption, conduction system disruption with development of heart block, coronary artery injury when ablating in the coronary cusps region or trying to gain access to the LV chamber, precipitation of cardiogenic shock from ablation of viable myocardium in patients with marginal reserve and failure to resuscitate or precipitation of cardiogenic shock from repeated VT induction, and with epicardial ablation the potential complications of epicardial access, coronary arteries and phrenic nerve damage. Recognition of these risks is paramount for their avoidance with careful pre-procedure planning and intraprocedural technique being essential to minimize the potential for complications.

Effects of linear, irrigated-tip radiofrequency ablation in porcine healed anterior infarction.

INTRODUCTION: Radiofrequency (RF) catheter ablation for ventricular tachycardia (VT) in healed infarction is modestly successful. More extensive, anatomically based procedures and irrigated RF delivery may improve outcome. However, limited data exist regarding the characteristics of irrigated RF lesions in infarcted myocardium. This study addresses this shortcoming. METHODS AND RESULTS: Linear lesions were created at the medial border of a healed anterior infarct in eight pigs using irrigated RF energy guided by sinus rhythm electroanatomic voltage mapping and intracardiac echocardiography (ICE). Lesion morphology and effects on ventricular function were assessed with ICE imaging and pathologic analysis (n = 5). The response to programmed stimulation also was determined before and after linear lesions (n = 6). A mean of 9.4 +/- 1.3 RF applications created linear lesions 37.0 +/- 10.6 mm long, 5 to 12 mm wide, and 4 to 8 mm deep. Thrombus formation was not observed. Lesion delivery resulted acutely in increased local wall thickness at the RF site (26.9% +/- 27.5%; P < 0.0001) and transient systolic dysfunction in adjacent normal myocardium (fractional shortening -38% +/- 34%; P < 0.01). Uniform sustained VT (cycle length 232 +/- 41 msec) was induced in 4 of 6 pigs before ablation, but sustained VT could not be induced afterward. CONCLUSION: Irrigated RF energy produced relatively large lesions in infarcted myocardium without thrombus formation. Changes in tissue thickness and echo density observed with ICE verify irrigated RF lesion delivery. Temporary left ventricular dysfunction is consistently observed in the normal myocardium adjacent to the linear lesion.

Changes in local wall thickness correlate with pathologic lesion size following radiofrequency catheter ablation: an intracardiac echocardiographic imaging study.

INTRODUCTION: High-resolution intracardiac echocardiographic (ICE) imaging can accurately assess wall thickness during radiofrequency (RF) catheter ablation procedures. This study investigated the correlation of changes in wall thickness at the ablation site with pathologic lesion size. METHODS AND RESULTS: ICE image-guided 31 RF applications (30-50 W, up to 120 sec) were performed in five anesthetized closed chest swine (n = 5, body weight 35-60 kg). Twenty-four lesions were delivered in the right and left atria with standard RF; seven lesions were delivered in the left ventricle (LV) with irrigated (30-40 ml/min) RF. Wall thickness and tissue echo density measured by ICE imaging (pre- and 1-minute post-RF delivery) with increased focal echo density following RF deployment in the atria (4.5 +/- 1.5 vs 2.3 +/- 1.0 mm pre-RF) and the LV (9.8 +/- 2.3 vs 6.8 +/- 2.2 mm pre-RF; P < 0.01). The observed changes in wall thickness (DeltaWT) following ablation in the LV were greater than in the atria (3.0 +/- 1.4 vs 2.2 +/- 1.2 mm; P < 0.05). A significant correlation between DeltaWT and lesion depth (ventricular: r = 0.85, P < 0.05; atrial: r = 0.82, P < 0.01) was demonstrated at all ablation sites. Local wall thickness measured post-RF also significantly correlated with lesion depth (r = 0.89, P < 0.01), especially with that of transmural lesions (r = 0.95, n = 23, P < 0.001) at atrial and LV sites. CONCLUSION: Therapeutic RF ablation results in mural swelling and increased echo density. These changes can be detected by ICE imaging and correlate with pathologic lesion size. ICE imaging may be useful in online quantification of lesion size, especially for transmural lesions during clinical catheter ablation procedures.

Echocardiographic lesion characteristics associated with successful ablation of inappropriate sinus tachycardia.

INTRODUCTION: Catheter ablation of inappropriate sinus tachycardia has proven difficult. Despite the use of intracardiac echocardiography to help direct radiofrequency (RF) application to the anatomic target of the superolateral crista terminalis (CT), multiple RF lesions often are required. Furthermore, the characteristic echo-anatomic changes with RF application associated with a reduction in heart rate have not been defined. A characteristic echo signature, if present, may facilitate the ablation process. The purpose of this retrospective study was to define the echocardiographic characteristic changes associated with effective RF ablation for inappropriate sinus tachycardia. METHODS AND RESULTS: Detailed intracardiac echocardiographic imaging characterization of the superolateral CT was performed before and at the time of successful heart rate reduction. Using on-line videotape intracardiac echocardiography (9 MHz, 9 French), changes in wall thickness and echodensity at the CT lesion site were assessed at baseline, after each RF lesion, and with the lesion that produced heart rate reduction in 17 patients (age 32 +/- 9 years; 15 women) with inappropriate sinus tachycardia. In all patients, RF ablation was anatomically based and targeted only the superolateral CT. RF lesions were created using 20 to 50 W for up to 2 minutes using an 8-mm tip electrode. Successful heart rate reduction (> or = 20 beats/min) was achieved in 15 of 17 patients and required 41 +/- 31 RF applications (range 5 to 110, median 40). Effective RF (reduced heart rate) was observed starting with the 34th +/- 24th lesion (range 3rd to 86th, median 25th). After effective RF, CT wall thickness was increased (11.4 +/- 3.1 mm vs 7.7 +/- 2.4 mm at baseline) and wall swelling expanded to adjacent superior vena cava, but the degree of thickening was not specific for effective RF associated with heart rate reduction. Importantly, we noted echodensity changes reaching directly to the epicardium with the development of a linear low echodensity or echo-free space at the time of effective RF resulting in heart rate reduction. In two patients without effective heart rate reduction, echodensity changes never reached the epicardium. No complications (superior vena cava-right atrial junction orifice narrowing >50% or pericardial effusion) of RF were identified. CONCLUSION: An echocardiographically guided anatomic approach to RF ablation of inappropriate sinus tachycardia is safe and effective. A characteristic echocardiographic signature suggesting transmural/epicardium damage appears to be present at the time of successful heart rate reduction and may serve as an appropriate guide for directing additional RF when using this anatomic echocardiographically based approach.

Clinical characteristics and catheter ablation of left ventricular outflow tract tachycardia.

Left ventricular outflow tract (LVOT) tachycardia is an uncommon form of idiopathic ventricular tachycardia (IVT). The underlying mechanism of this arrhythmia appears to be cyclic AMP-medicated triggered activity. The tachycardia occurs in the absence of structural heart disease and is generally benign, presenting commonly as palpitations and presyncope. It can manifest either a right or left bundle branch block morphology with an inferior axis. Subtle variations in the QRS morphology in leads I, V1, and V2 can help in localizing the anatomic site of origin (SOO). The arrhythmia is typically responsive to a variety of pharmacologic agents (beta-blockers, calcium channel blockers, Class I and II agents). Radiofrequency catheter ablation of LVOT tachycardia SOO as determined by pace mapping is quite efficacious (success rates of 90%). Magnetic electroanatomic mapping augments this by permitting three-dimensional catheter mapping and reproducible localization of the SOO. Catheter ablation should be considered relatively early in patients who experience severe symptoms with their arrhythmia and have failed, or are reluctant to take medications for the disorder.

Intracardiac echocardiographic evaluation of ventricular mural swelling from radiofrequency ablation in chronic myocardial infarction: irrigated-tip versus standard catheter.

INTRODUCTION: The production of larger, particularly deeper lesions may improve the success rate for radiofrequency (RF) ablation of post infarction ventricular tachycardia (VT). Therapeutic RF ablation causes left ventricular (LV) mural swelling. This swelling can be detected as increased wall thickness at the ablation site by intracardiac echocardiography (ICE) and correlates with pathologic lesion size. This study compared the extent of mural swelling caused by linear ablation lesions created with irrigated tip and standard RF ablation in a porcine model of healed anterior infarction. METHODS AND RESULTS: In anesthetized closed-chest swine ICE guided multiple RF applications to construct linear lesions at the border zone of the infarct region using an irrigated RF (n=6 swine) and a standard RF (n=6 swine) ablation catheter. 47 individual lesions were created with irrigated RF ablation; 57 lesions created with standard RF ablation. At all sites, wall thickness (measured at end-diastole Pre- and 1 min Post-RF delivery) increased following either irrigated (p<0.0001) or standard (p<0.004) RF deployment. Irrigated RF ablation produced more mural swelling at border zone sites than standard RF ablation (wall thickness increase of 21.2 versus 15.1 %, p<0.003). This difference was more pronounced at RF sites within the infarct (40.7 versus 12.0 %, p<0.0007). Thrombus formation or intramural explosion were not observed; surface crater formation was not more frequent with irrigated compared to standard RF ablation (14/47 versus 12/57 lesions, p=NS). CONCLUSION: Irrigated RF ablation may produce larger lesions than standard RF ablation, particularly for ablation targets within infarcted tissue. ICE imaging provides on line data about the characteristics of the developing lesion which may prove useful in dosing irrigated-tip RF energy application.

Use of multisite electroanatomic mapping to facilitate ablation of intra-atrial reentry following the Mustard procedure.

Ablation of intra-atrial reentrant tachycardia following Mustard or Senning procedures has low success rates. The Biosense Carto system was used to map intra-atrial reentry in a 22-year-old woman who had undergone a Mustard procedure. A line of block was created connecting a Mustard baffle suture line to the tricuspid valve annulus, which terminated the arrhythmia and prevented its reinitiation. Multisite electroanatomic mapping was invaluable in defining atrial anatomy and the intra-atrial reentrant pathway, and in creating a contiguous line of block. This mapping may improve ablation success rates in patients following the Mustard or Senning repair.

Accuracy of fluoroscopic localization of the Crista terminalis documented by intracardiac echocardiography.

The crista terminalis is an important anatomic target for ablation of atrial arrhythmias. We determined the accuracy of catheter placement guided by fluoroscopy alone when directed to 24 sites along the crista terminalis in 6 patients. The sites selected included the most medial superior, most lateral superior, mid lateral, and most inferolateral sites along the crista terminalis in each patient. These sites were selected because of their recognized importance in sinus node and/or atrial tachycardia ablation and the importance of avoiding caval structures when targeting the most superior and/or inferior right atrium. The position of the catheter tip was documented using a catheter based ultrasound transducer in the right atrium or vena cava. The operator was blinded to the intracardiac echocardiographic (ICE) results until reviewing the images after the procedure in each patient. The catheter tip, guided by fluoroscopy alone, was identified by ICE to be within the right atrium and within 1cm of the crista terminalis at only 10 of the 24 sites (42%). Importantly, when targeting the most superior and inferior sites along the crista terminalis, the catheter tip, guided by fluoroscopy, was noted to be adjacent to the venous junction with the right atrium but actually located in the superior or inferior vena cava at 5 of the 18 such sites. The catheter was positioned appropriately (within 1 cm of the crista and within the right atrium) guided by fluoroscopy alone when targeting 1 of the 12 sites in the first 3 patients versus 9 of 12 sites in the last 3 patients, p<0.05. In conclusion, it appears that using fluoroscopic guidance alone: 1) localization of the crista terminalis is frequently inaccurate and 2) catheter positioning in the superior/inferior vena cava is commonly noted when targeting very superior and inferior sites along the crista terminalis. A learning curve, assisted by review of ICE recordings after each procedure, appears to improve the accuracy of catheter placement by fluoroscopy alone but still does not result in uniform success. ICE appears to facilitate and ensure accurate targeting of specific anatomic sites along the crista terminalis and thus may serve as an important adjunctive imaging technique in electrophysiology.

Hybrid therapy for ventricular arrhythmia management.

Optimum arrhythmia management has evolved to couple ICD therapy with catheter ablative and drug therapy to attempt to eliminate or reduce arrhythmia risk. No longer should the clinician approach such therapy as a choice among single alternative strategies only. Optimum patient management includes not only recognition of the indications and benefits of such hybrid therapy but also a complete understanding of potential pitfalls of such therapy.

Sex-specific triggers for right ventricular outflow tract tachycardia.

BACKGROUND: Right ventricular outflow tract tachycardia (RVOT-VT) is a common arrhythmia in young patients without heart disease. The arrhythmia is characterized by repetitive bursts and premature ventricular contractions with a left bundle branch block, inferior-axis QRS morphology, and symptoms of palpitations. Although more frequent in women, sex-specific triggers for symptomatic RVOT-VT have not been identified. METHODS AND RESULTS: We interviewed 34 women and 13 men referred for ablation of RVOT-VT to determine if predictable but sex-specific exacerbations in symptomatic RVOT-VT exist. After a general query asking if there was predictability to what triggered palpitations, we then specifically queried all patients about symptomatic RVOT-VT initiation with exercise, stress, caffeine, fatigue, and, in women only, periods of recognized hormonal flux. The times identified as states of hormonal flux included premenstrual, gestational, perimenopausal, and coincident with the administration of birth control pills. In response to the completed interview, the most common recorded trigger for RVOT-VT in women was recognized states of hormonal flux with 20 (59%) of 34 women responding positively and 14 (41%) of the 34 indicating that states of hormonal flux were the only recognizable triggers. Men were more likely than women to report that their RVOT-VT was predictably triggered by exercise, stress, or caffeine: 12 (92%) of 13 men versus 14 (41%) of 34 women (P <.01). CONCLUSIONS: Triggers for RVOT-VT initiation are sex specific. Women have RVOT-VT initiation with recognized states of hormonal flux. Men more commonly have RVOT-VT initiated by exercise or stress. These data have important implications related to patient education and counseling in the setting of RVOT-VT and may influence the timing of drug treatment and electrophysiologic evaluation in selected patients.

Using intracardiac catheter recordings from the His and proximal coronary sinus to distinguish isthmus conduction block during catheter ablation of type I atrial flutter.

Isthmus conduction block, demonstrated with the use of multipolar catheter recordings, is considered the preferred endpoint for ablation of type I atrial flutter. This study investigated the feasibility of using recordings from the His and coronary sinus (CS) to document isthmus conduction block. Isthmus conduction block was produced with linear radiofrequency (RF) ablation in 27 patients with type I atrial flutter. In 13 patients (group I), RF was delivered until bidirectional isthmus conduction block was demonstrated with multipolar Halo catheter recordings. In 14 patients (group II), RF was delivered during pacing from the lateral isthmus at 600 ms until a reversal in activation of the proximal CS and His occurred. At this point, data from the Halo recordings were reviewed to see if reversal correlated with conduction block; if not, further ablation was performed until block was demonstrated. The initial reversal in His and CS activation during RF energy delivery correlated with isthmus block in only 4 (28.6%) of 14 patients in group II. Additional RF delivery produced isthmus block in the other ten patients resulting in a further increase in the St-CS interval of 35 +/- 20 ms. A His-CS interval of at least -40 ms signified isthmus block with a sensitivity and specificity of 48% and 100%, respectively. Reversal in His-CS activation during pacing from the lateral margin of the isthmus is not specific for the creation of isthmus block. While activation of the proximal CS bipole > 40 ms after activation of the His appears specific for isthmus block, the low sensitivity of this finding limits its clinical use.

Linear ablation lesions for control of unmappable ventricular tachycardia in patients with ischemic and nonischemic cardiomyopathy.

BACKGROUND: Conventional activation mapping is difficult without inducible, stable ventricular tachycardia (VT). METHODS AND RESULTS: We evaluated 16 patients with drug refractory, unimorphic, unmappable VT. Nine patients had ischemic and 7 had nonischemic cardiomyopathy. All patients had implantable defibrillators and had experienced 6 to 55 VT episodes during the month before treatment. Patients underwent bipolar catheter mapping during baseline rhythm. The amount of endocardium with an abnormal electrogram amplitude was estimated using fluoroscopy in 3 patients and a magnetic mapping system (CARTO) in 13 patients. For the magnetic mapping, normal endocardium was defined by an amplitude >1.5 mV; this measurement was based on sinus rhythm maps in 6 patients who did not have structural heart disease. Radiofrequency point lesions extended linearly from the "dense scar," which had a voltage amplitude <0.5 mV, to anatomic boundaries or normal endocardium. To limit radiofrequency applications, 12-lead ECG during VT and pacemapping guided placement of linear lesions. No new antiarrhythmic drug therapy was added. The amount of endocardium demonstrating an abnormal electrogram amplitude ranged from 25 to 127 cm(2). A total of 8 to 87 radiofrequency lesions (mean, 55) produced a median of 4 linear lesions that had an average length of 3.9 cm (range, 1.4 to 9. 4 cm). Twelve patients (75%) have been free of VT during 3 to 36 months of follow-up (median, 8 months); 4 patients had VT episodes at 1, 3, 9, and 13 months, respectively. Only one of these patient had frequent VT. CONCLUSIONS: Radiofrequency linear endocardial lesions extending from the dense scar to the normal myocardium or anatomic boundary seem effective in controlling unmappable VT.

Basket catheter localization of the origin of atrial tachycardia with atypical morphology after atrial flutter ablation.

Atrial activation from a site in the low lateral right atrium will typically proceed in a superior direction. We present a case of a low lateral right atrial tachycardia with a surface electrocardiographic P wave morphology that appeared to have an inferiorly directed axis. The tachycardia occurred 2 years after successful atrial flutter ablation. The use of a multipolar basket catheter allowed confirmation of the focal origin of the tachycardia, permitted its rapid localization, facilitated catheter ablation, and provided clues to atrial activation that helped describe the appearance of the P wave.

Efficacy and safety of catheter ablation in octogenarians.

OBJECTIVES: To determine whether catheter ablation is safe and effective in patients over the age of 80. BACKGROUND: There is a tendency to withhold invasive therapy in the elderly until it has been proven safe and effective. METHODS: Over a two-year period from February 1, 1996 to February 1, 1998, 695 consecutive patients underwent 744 catheter ablation procedures of supraventricular and ventricular arrhythmias. These patients were divided into three groups based on age: > or =80 years, 60 to 79 years and <60 years. Acute ablation success, using standard criteria and complication rates for these three groups were determined. RESULTS: There were 37 patients > or =80 years, 275 patients 60 to 79 years and 383 patients <60 years old. The overall acute ablation success rate for the entire group was 95% with no difference in rates among the three groups (97%, > or =80 years; 94%, 60-79 years; 95%, <60 years). The percentage of patients undergoing His bundle ablation was greatest in the > or =80-year-old group (43% vs. 19% vs. 2%, p < 0.01), and the percentage of patients undergoing accessory pathway ablation was greatest in the <60-year-old patients (0% vs. 4% vs. 25%, p < 0.01). The overall complication rate for the entire group was 2.6%, and there was only one major/life-threatening complication. There was no difference in complication rates among the groups (0%, > or =80 years; 2.2%, 60 to 79 years; 3.1%, <60 years). Based on the sample size, the 95% confidence interval is 0% to 7.8% for an adverse event in the octogenarian. CONCLUSIONS: Catheter ablative therapy for the arrhythmias attempted in the very elderly appears to be effective with low risk. Ablation results appear to be comparable with those noted in younger patients.

Electroanatomic magnetic mapping during ablation of isthmus-dependent atrial flutter.

INTRODUCTION: Although recent studies have demonstrated that the endpoint of isthmus conduction block is superior to that of termination and subsequent inability to induce atrial flutter (AFl), the optimal method for determining isthmus conduction block has not been determined. Electroanatomic magnetic mapping during coronary sinus (CS) pacing may provide a reliable endpoint for AFl ablation. METHODS AND RESULTS: Catheter mapping and ablation was performed in 42 patients with isthmus-dependent AFl. The patients were divided into two groups, based on procedural endpoint: Group I (28 patients) - isthmus conduction block was determined based on multipolar catheter recordings and electroanatomic mapping, and Group II (14 patients) - isthmus conduction block was determined by electroanatomic mapping during CS pacing alone. In Group I, ablation procedures were acutely successful in 25 of 28 patients (89 %). A 100 % concordance between the data presented by multipolar catheter recordings and electroanatomic mapping was noted in determining the presence or absence of isthmus conduction block. In Group II, ablation procedures were acutely successful in 13 of 14 patients, 13 (93 %). After a mean of 16.3+/-3.7 months follow up, there was 1 atrial flutter recurrence in the 38 patients (2.6 %) with demonstrated isthmus block at the end of the procedure. CONCLUSIONS: Electroanatomic magnetic mapping during CS pacing is comparable to the multipolar catheter mapping technique for assessing isthmus conduction block as an endpoint for AFl ablation procedures.