Effect of Charge Delivery on Thromboembolism During Radiofrequency Ablation in Canines.

OBJECTIVES: This study investigated whether delivering negative charge to catheter tips reduces thromboembolism during catheter ablation. BACKGROUND: Radiofrequency (RF) ablation prevents atrial fibrillation that can cause stroke or death. However, ablation itself can cause stroke (2%) or silent ischemia (2% to 41%), possibly via particulate debris that embolizes after coagulum adherence to catheter surfaces. Coagulum formation on RF catheters can be prevented by applying negative charge, but it is unknown if charge reduces peripheral thromboembolism. METHODS: Paired (Charge ON vs. OFF) endocardial RF ablations were performed in 9 canines using nonirrigated RF catheters. Continuous negative charge was delivered via -100 µA of DC current applied to ablation catheter electrodes. Intracardiac echocardiography was used to navigate the catheter and to monitor coagulum formation. In a subset of 5 canines, microemboli flowing through polyester tubing between the femoral artery and vein (extracorporeal loop) were monitored with bubble counters and inline filter fabric. After each ablation, catheter-tip coagulum and blood particles deposited on the filters were quantified using photography and imaging software (ImageJ, U.S. National Institutes of Health, Bethesda, Maryland). RESULTS: Negative charge significantly decreased the extracorporeal loop median filter area covered by particles (n = 19 pairs) by 10.2 mm2 (p = 0.03), and decreased median filter particles by 349 (p = 0.03). Negative charge also decreased the percentage of the catheter tip surface area covered by coagulum (n = 39 pairs) by 7.2% (p = 0.03). CONCLUSIONS: Negative charge delivery to ablation catheter tips during RF ablation can reduce particulate embolization material in an extracorporeal loop, and potentially reduce thromboembolic risk associated with RF ablation.

Effect of atrial pacing on ventricular rate during atrial fibrillation. A human study.

OBJECTIVE: This research study tests the hypothesis that atrial pacing near the atrioventricular node during atrial fibrillation can affect ventricular rate. METHODS: In 13 patients, two monophasic action potential catheters were advanced into the low anterior septum (ANT) and the low posterior septum (POST) near the atrioventricular node. After induction of atrial fibrillation, measurement of the excitable gap was attempted at the ANT and POST regions. During atrial pacing, ventricular cycle length (CL) at the longest excitable gap was compared to ventricular CL at the shortest excitable gap by pairwise analysis. RESULTS: Transient capture of ANT tissue during ANT pacing was observed in six patients, whereas transient capture of POST tissue during POST pacing was observed in four patients. The ventricular response to ANT and POST pacing at multiple rates was recorded in six and seven patients, respectively. An increase in POST pacing CL by 40 +/- 24 ms prolonged (P < 0.05) ventricular CL by 45 +/- 56 ms. Conversely, an increase in ANT pacing CL by 48 +/- 42 ms shortened (P < 0.05) ventricular CL by 45 +/- 40 ms. CONCLUSIONS: ANT and POST pacing CL affected ventricular CL during atrial fibrillation, even though capture was transient. The opposite direction of the effects of ANT and POST pacing CL on ventricular CL may indicate that the atrial impulses from the POST region are more likely to conduct to the ventricle than impulses from the ANT region as the CL of activation is decreased.

Trans-telephonic monitoring of continuous haemodynamic measurements in heart failure patients.

The development of an implantable haemodynamic monitor (IHM) has made possible the home monitoring of a patient's central haemodynamic trends during daily living. We have evaluated the usability and transmission success of such a system over a 3.2-year period. Patients with an IHM were able to transmit the stored data every week to a Web server, where trend plots and tables of haemodynamic variables could be viewed by the health-care staff concerned. Data transfer was examined from August 2000 to November 2003. During this period, 148 patients had an IHM implanted. Over the study period, 7791 data transmissions were performed and an average of 286 downloads per month were sent to the Web server. In all, 86% of data transmissions were successful, although 10% required more than one attempt. The study demonstrated that telemonitoring of haemodynamic data from an IHM was feasible. A patient survey showed that the technology was user-friendly and that the training material provided sufficient information for patients and their families to install and use the transmission equipment at home. It also suggested that transmission success was independent of patient age or gender.