© 2000 by European Society of Cardiology
A jump in cycle length of orthodromic common atrial flutter during catheter ablation at the isthmus between the inferior vena cava and tricuspid annulus
Evidence of dual isthmus conduction directed to dual septal exits
Cardiovascular Center, Tsuchiura Kyodo Hospital Ibaraki-ken, Japan; 1Second Department of Internal Medicine, School of Medicine, Tokyo Medical and Dental University Tokyo, Japan; 2Department of Cardiovascular Disease, Medical Research Institute, Tokyo Medical and Dental University Tokyo, Japan
INTRODUCTION: In orthodromic common atrial flutter (AFL), details of intraseptal propagation of the flutter (FL) wave exiting from the isthmus between the inferior vena cava and tricuspid annulus (IVC-TA isthmus) remain unknown. We hypothesized the existence of dual septal exits of the FL wave from the IVC-TA isthmus to both the anterior, coronary sinus ostium (CSO-TA) isthmus, and the posterior septal (IVC-CSO) isthmus, and that the IVC-TA isthmus might consist of dual muscle bundles directed to both septal isthmuses over the eustachian ridge; therefore, segmental ablation of the IVC-TA isthmus could change intraseptal FL wave propagation.
METHODS AND RESULTS: To test the hypothesis, we investigated the influence of segmental ablation of the IVC-TA isthmus on intraseptal FL wave propagation. In seven of 40 (18%) consecutive patients, segmental ablation of the ventricular side of the IVC-TA isthmus during orthodromic common AFL led to sudden prolongation of the flutter cycle length (FCL) (from 266±33 ms to 291±45 ms) associated with changes in intraseptal activation sequences. They consisted of prolongation of the interval between the IVC-TA isthmus and the CSO (from 38±13 ms to 86±25 ms), shortening of the interval between the CSO and His (from 31±15 ms to 9±15 ms), and atrial electrogram polarity change at the His-bundle recording site. Morphological change in the FL wave was also seen on the 12-lead ECG.
CONCLUSIONS: In some patients, segmental ablation of the IVC-TA isthmus can lead to a jump in FCL and changes in intraseptal activation sequences of FL waves due to anterior-to-posterior shifting of the septal exit. This indicates that the IVC-TA isthmus may contain dual circumferential muscle bundles as conduction pathways directed to dual septal exits both anterior and posterior to the CSO.
Key Words: Orthodromic common atrial flutter, intraseptal flutter wave propagation, flutter cycle length jump, septal isthmuses dual exits, IVC-TA isthmus dual muscle bundles
Correspondence: Yoshito Iesaka, MD, Cardiovascular Center, Tsuchiura Kyodo Hospital, 11–7, Manabeshin-machi, Tsuchiura-shi, Ibaraki-ken, 300–0053, Japan.