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Notes: Three-Dimensional Reai-Time Position Management. Introduction: Precise localization of target sites for radiofrequency catheter ablation (RFCA) of arrhythmias is hampered by the relative inaccuracy of X-ray localization procedures. This study evaluated the efficacy of a three-dimensional (3D) real-time position management system in guiding RFCA procedures in patients.Methods and Results: Patients (n = 30, age 59 ± 20 years) referred for ablation of either atrial flutter (n = 10), ventricular tachycardia (n = 15), or accessory pathways (n = 5) were studied. The real-time position management system uses ultrasound ranging techniques to track the position of an ablation catheter relative to two multitransducer reference catheters, positioned in the right atrium or coronary sinus and the right ventricle. Each catheter contains three or four ultrasound transducers. The distance between the transducer(s) is determined hy calculating the time necessary for an ultrasound pulse to reach other transducers, assuming the speed of sound in blood is 1,550 m/sec. The proximal His bundle was marked at the beginning and the end of the procedure as an electrical landmark to verify reproducibility. After identification of target sites, the position of each lesion created with the ablation catheter was marked. Successful ahlation was achieved in 94% of the patients. The distance between the location of the proximal His hundle as marked at the beginning and at the end of the procedure was 2.0 ± 1.2 mm (range 1.5 to 3.5).Conclusion: The new 3D real-time position management system facilitated RFCA procedures as it allowed accurate and reproducible 3D tracking of the mapping and ablation catheter.

Notes: RF Catheter Ablation of VT. Introduction: Radiofrequency ablation (RFCA) of ventricular tachycardia (VT) is a potential curative treatment modality. We evaluated the results of RFCA in patients with VT. Methods and Results: One hundred fifty-one consecutive patients (122 men and 29 women; age 57 ± 16 years) with drug-refractory VT were treated. Underlying heart disease was ischemic heart disease in 89 (59%), arrhythmogenic right ventricular cardiomyopathy (ARVC) in 32 (21%), and idiopathic VT in 30 (20%; left ventricle in 9 [30%]; right ventricle in 21 [70%]). Ablation was performed using standard ablation techniques. Three hundred six different VTs were treated (cycle length 334 ± 87 msec, 2.0 ± 1.4 VTs per patient). Procedural success (noninducibility of VT after RFCA) was achieved in 126 (83%) patients (70 ischemic heart disease [79%]; 28 ARVC [88%]; 27 idiopathic VT [93%]). Procedure-related complications (〈 48 hours) occurred in 11 (7%) patients: death 3 (2.0%), cerebrovascular accident 2 (1.3%), complete heart block 4 (2.6%), and pericardial effusion 3 (2.0%). Thirty-three (22%) patients received an implantable cardioverter defibrillator (because of hemodynamic unstable VT, failure of the procedure, or aborted sudden death). During follow-up (34 ± 11 months), VT recurrences occurred in 38 (26%) patients (recurrence rate: 19% in successfully ablated patients and 64% in nonsuccessfully ablated patients; P 〈 0.001). During follow-up, 12 (8%) patients died (heart failure 8, unknown cause 1, noncardiac cause 3). Conclusion: RFCA of VT can be performed with a high degree of success (83%). The long-term outcome of successfully ablated patients is promising, with a 75% relative risk reduction compared with nonsuccessfully ablated patients. During follow-up, only one patient died suddenly, supporting a selective ICD placement approach in patients with hemodynamically stable VT.

Notes: DE GROOT, N.M.S., et al.: Three-Dimensional Distribution of Bipolar Atrial Electrogram Voltages in Pa-tients with Congenital Heart Disease. Voltage differences might be used to distinguish normal atrial tissue from abnormal atrial tissue. This study was aimed at identifying lowest voltage areas in patients with atrial tachycardia after surgical correction of congenital heart disease and to evaluate if identification of these areas in diseased hearts facilitates selection of critical conduction pathways in reentrant circuits as target sites for catheter ablation. Ten patients (four men, age 39 ± 15 years) with normal sized atria and atrioventricular reciprocating tachycardia (control group) and ten patients (5 men, 32 ± 7 years) with congenital heart disease and postoperative atrial tachycardia (CL 281 ± 79 ms) referred for radiofrequency catheter ablation were studied. Mapping and ablation was guided by a three-dimensional electroanatomic mapping system (CARTO) in all patients. In the control group, voltage maps were constructed during sinus rhythm and during tachycardia to evaluate the voltage distribution. The amplitude of bipolar signals was 1.90 ± 1.45 mV (0.11–8.12 mV, n = 660) during sinus rhythm and 1.45 ± 1.66 mV (0.12–5.83 mV, n = 440, P 〈 0.05) during atrioventricular reciprocating tachycardia. In the study group, the amplitude of 1,962 bipolar signals during tachycardia was 1.01 ± 1.19 mV (0.04–9.40 mV), which differed significantly from the control group during tachycardia (P 〈 0.0001). No significant difference in the tachycardia cycle length was found (P 〈 0.05) between the control and study groups. As the lowest voltage measured in normal hearts was 0.1 mV, this value was used as the upper limit of the lowest voltage areas in the patients with congenital heart disease. These areas were identified by detailed voltage mapping and represented by a gray color. Activation and propagation maps were then used to select critical conduction pathways as target sites for ablation. These sites were characterized by fragmented signals in all patients. Ablation resulted in termination of the tachycardia in eight (80%) of ten patients. Complications were not observed. Identification of the lowest voltage areas using a cut-off value of 0.1 mV in congenital heart disease patients with postoperative atrial reentrant tachycardia facilitated the selection of critical conduction pathways as target sites for ablation.