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.

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.

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.

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.

Concomitant device and drug therapy: current trends, potential benefits, and adverse interactions.

Antiarrhythmic drug therapy in patients with implantable cardioverter defibrillators (ICDs) has decreased over the last 10 years. This trend, primarily seen with class I agents, has occurred mainly in patients with a cardiac arrest. However, despite this overall decrease, antiarrhythmic drug therapy remains an important adjuvant to ICD therapy. In addition to primary prevention of ventricular tachycardia and supraventricular tachycardia, antiarrhythmic drug therapy may potentiate tachycardia rate slowing and make ventricular tachycardia more tolerated hemodynamically and possibly more amendable to pacing therapy. Some of the class III antiarrhythmic drugs may actually lower defibrillation threshold. Unfortunately, these drugs may have adverse interactions with ICDs. An increase in defibrillation threshold or rate-dependent increase in pacing threshold may interfere with the effectiveness of device therapy. Proarrhythmic effects of antiarrhythmic drugs may enhance the frequency of device use. The bradycardic effects of antiarrhythmic drug therapy may similarly enhance the requirements for persistent bradycardia pacing and lead to early battery depletion and other adverse consequences. An awareness of potential benefits and adverse effects of antiarrhythmic drug therapy along with careful electrophysiologic assessment are necessary for optimum combination drug and device therapy.

Efficacy of radiofrequency catheter ablation for ventricular tachycardia in healed myocardial infarction.

Radiofrequency catheter ablation has been useful in the treatment of ventricular tachycardia (VT) in selected patients with healed myocardial infarction. Previous studies have demonstrated success rates of 60% to 96% for targeted VT morphologies; however, these studies included patients only after they have had successful mapping procedures and have received radiofrequency lesions. All patients referred for VT ablation from July 1992 to November 1996 were included in this analysis on an intention-to-treat basis. Ninety-five procedures were performed in 66 patients for 77 distinct presentations with tolerated, sustained VT. Fifty-five procedures were successful (58%) and 40 procedures failed. Reasons for procedural failure included failed radiofrequency application despite adequate VT mapping (21 procedures), no tolerated VT induced (12), and aborted procedures due to complications or technical difficulties (7). Fifty-five patients (71%) eventually had a successful VT ablation, although 10 required > 1 procedure. This analysis revealed factors that contribute to failure of VT ablation procedures in addition to inadequate mapping and lesion formation. Procedural difficulties, particularly the inability to induce tolerated VT, frequently prevent successful catheter ablation in patients who present with tolerated, sustained VT.

Idiopathic right ventricular outflow tract tachycardia: narrowing the anatomic location for successful ablation.

Pace mapping used to locate the site for ablation of idiopathic right ventricular outflow tract (RVOT) ventricular tachycardia remains difficult and time-consuming. A method to facilitate pace mapping and the most common site of ablation of this tachycardia are reported. In 18 consecutive patients with RVOT ventricular tachycardia, electrocardiographic criteria based on the QRS orientation in lead 1 and the R wave progression in the precordial leads were used to find pace maps matching the arrhythmia. Identical pace maps were obtained on the septum of the RVOT in 16 patients and resulted in successful ablations. These sites were concentrated in the anterior superior aspect of the RVOT determined by fluoroscopic imaging. In the remaining two cases identical pace maps could not be found in this area. The results of this study narrow the anatomic location for radiofrequency ablation of idiopathic RVOT ventricular tachycardia. This is the first description of an electrocardiography-guided approach to finding an identical pace map in the RVOT.