Effects of Procainamide on the Excitable Gap Composition in Common Human Atrial Flutter

The composition of the excitable gap (EG) in common atrial flutter (AFI) was determined before and during infusion of procainamide (PA) in 9 patients (6 men and 3 women; age 70 ± 7 years). The EG was determined by introducing a premature stimulus after every 20th AFI complex detected using a quadripolar electrode catheter placed just above the tricuspid valve. Diastole was scanned in 2- to 4-ms decrements to the atrial effective refractory period (ERP). The relationship between the coupling interval and the return cycle length (CL) determined a reset-response curve (RRC), which described the EG. PA (15 mg/kg) was administered during AFl over 30 minutes and RRC was repeated at maximum AFI CL. PA prolonged AF1 CL from 227 ± 29 to 296 ± 62 ms (P < 0.01) but did not terminate AFI. ERP during AFl prolonged from 169 ± 24 to 219 ± 41 ms (P < 0.01). Control EG was 57 ± 16 ms or 25%± 6% of AFl CL and on PA EG was 77 ± 30 ms (P = 0.01), which was still 26%± 7% of the CL. Without drug, RRC was mixed in eight cases demonstrating an EG composed of fully excitable tissue (10 ± 4 ms or 19%± 10% of the EG) and partially refractory tissue (48 ± 18 ms), PA did not change the duration of the fully excitable region (13 ± 10 ms or 19%± 15% of EG). Peak PA plasma concentration was 47 ± 20 μmol/L. PA prolonged AFI CL, ERP, and EG duration but did not change the proportion of AFI CL occupied by the EG. The persistence of fully excitable tissue at the head of the wavefront in the presence of PA may largely explain its inefficacy in the acute termination of common AFl.     

Successful Catheter Ablation of Atrial Fibrillation

Catheter Ablation of AF. Introduction: Catheter ablation of a case of incessant atrial fibrillation was attempted using linear right atrial lesions created by sequential applications of radiofrequency energy.
Methods and Results: A 46-year-old patient had incessant episodes of atrial fibrillation. He had previously undergone successful radiofrequency catheter ablation of a common atrial flutter. Antiarrhythmic drugs including amiodarone and various drug combinations were ineffective. A 7-French specially designed 14-polar catheter with interelectrode distance of 3 mm was used to create linear lesions in the right atrium. Each electrode was 4 mm in length and able to transmit radiofrequency energy. Three linear lesions, two longitudinal and one transverse that connected the two longitudinal lesions, were created using 30 radiofrequency applications of 10 to 40 W. The final application interrupted an atrial fibrillation that had been persistent for 55 minutes. No sustained atrial fibrillation was inducible despite repeated pacing maneuvers. There was no complication. In short-term follow-up of 3 months, the patient has been free of arrhythmias without antiarrhythmic medication.
Conclusion: Successful catheter ablation of human atrial fibrillation is feasible using linear atrial lesions created by radiofrequency energy delivery. Further studies are mandatory to ascertain the efficacy and safety of this procedure, as well as to assess different catheter techniques.