A constant postpacing interval in response to overdrive pacing with variable number of beats: An aid in the identification of entrainment for a particular pacing train during macroreentrant atrial tachycardias.

BACKGROUND: When pacing trains with a constant cycle length (CL) but increasing number of beats are introduced during a macroreentrant atrial tachycardia (MAT), the postpacing interval (PPI) is expected to increase if entrainment does not occur but could be stable if entrainment occurs. We tested the ability of PPI analysis to detect entrainment. METHODS: Synchronized pacing trains with increasing number of beats (1-20) were delivered from the coronary sinus (CS) and lateral right atrium (RA) at a CL 20 ms shorter than the MAT CL. Pacing trains were grouped in pairs differing by one-paced beat, and the ∆PPI measured. RESULTS: In an initial prospective cohort of 21 patients (48% had left atrial flutter) the mean ∆PPI was 21.3 ± 5.6 ms for pairs of pacing trains in which neither entrained the MAT and 2.8 ± 1.4 ms for those in which both entrained the MAT (P < .0001). Results were similar for common vs atypical flutter, PPI-TCL ≤30 ms vs PPI-TCL >30 ms, presence vs absence of antiarrhythmic drugs and faster vs slower MAT. When an index pacing train was compared to one with two-paced beats less, a PPI difference of <19 ms identified entrainment with 95% sensitivity and 98% specificity. In a validation cohort of 16 patients, this cut-off value resulted in sensitivity and specificity of 90% and 94%. CONCLUSIONS: A relatively constant ∆PPI in response to overdrive pacing with identical CL but different number of beats allows accurate discrimination between trains that entrained vs those which did not entrain a MAT.

A zero-fluoroscopy approach to cavotricuspid isthmus catheter ablation: comparative analysis of two electroanatomical mapping systems.

BACKGROUND: Electroanatomical mapping systems have reduced the amount of fluoroscopy required to ablate the cavotricuspid isthmus. The aims of this study are to evaluate the feasibility and safety of a zero-fluoroscopy approach to cavotricuspid isthmus catheter ablation using the Carto®3 system (Biosense Webster, Diamond Bar, CA, USA) and to compare the results of this approach with those of the zero-fluoroscopy approach using the Ensite-NavX™ system (St. Jude Medical, St. Paul, MN, USA). METHODS: Twenty consecutive procedures guided by the Carto®3 system (Group A) were compared with two case-control groups matched from 146 procedures guided with the Ensite-NavX™ system. Group B consisted of 20 matched procedures from the first 50 procedures performed in the electrophysiology unit, and Group C consisted of 20 matched procedures from the last 50 procedures. Acute success (bidirectional block), complications, and recurrences were analyzed. The procedure times were also compared. RESULTS: There were no differences in the rates of acute success (95%, 100%, and 100%, respectively), complications (0%, 5%, and 0%), and recurrences (5.2%, 0%, and 5%) in the three groups. A zero-fluoroscopy approach was attempted in all procedures, and electroanatomical mapping made it possible to successfully avoid fluoroscopy in 90% of the procedures in Group A, 85% in B, and 95% in C. The total procedure time was shorter in Group C. The fluoroscopy and radiofrequency times were not different. CONCLUSIONS: A zero-fluoroscopy approach to cavotricuspid isthmus catheter ablation using the Carto®3 system is feasible in most procedures. This approach has similar results to the zero-fluoroscopy approach using the Ensite-NavX™ system.

Lessons learned in attempting catheter-based interatrial electrical disconnection for nonpharmacologic rate control of atrial fibrillation or flutter.

PURPOSE: Ablation of atrioventricular (AV) conduction and pacemaker implantation is the therapy of last resort for symptomatic atrial tachyarrythmias when rhythm and rate control fail, but is far from ideal. To evaluate whether interatrial electrical disconnection as a result of catheter ablation is feasible and of potential clinical utility as a means of non-pharmacological heart rate control. METHODS: Eleven patients with medically refractory atrial fibrillation or left atrial flutter and symptomatic rapid ventricular response were included. The ablation strategy consisted primarily of right atrial ablation of the interatrial electrical connections, which were located by electroanatomical activation maps performed during coronary sinus stimulation. Successive activation maps were performed as each connection was blocked. If the procedure was considered unsuccessful AV nodal ablation was performed. RESULTS: The coronary sinus ostium was earliest in 10/11 and could be ablated in 5/10 patients. Interatrial conduction block was only achieved in one patient (9.1%). An unexpected AV nodal modulation with an increase in the Wenckebach cycle length (> 50 ms) occurred in 8/11 patients. These patients remained without pacemaker implantation and only 1/8 required AV nodal ablation during the 1-year follow-up. Quality of life questionnaires indicated significant improvement in patients with AV nodal modulation. CONCLUSION: Interatrial electrical disconnection by right atrial catheter ablation is a not feasible with present day technology. The extensive right atrial septal ablation performed resulted in significant AV nodal modulation in most patients, which persisted and resulted in improvement in quality of life.