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CLINICAL STUDY: ELECTROPHYSIOLOGY

Sensitivity and specificity of concealed entrainment for the identification of a critical isthmus in the atrium: relationship to rate, anatomic location and antidromic penetration

^a Department of Cardiology, The Royal Melbourne Hospital and University of Melbourne, Melbourne, Australia

Manuscript received September 11, 2001; revised manuscript received December 3, 2001, accepted December 14, 2001.

^* Reprint requests and correspondence: Prof. Jonathan M. Kalman, Department of Cardiology, The Royal Melbourne Hospital, Grattan Street, Parkville 3050, Melbourne, Australia
jon.kalman{at}mh.org.au

OBJECTIVES

This study was designed to determine the sensitivity and specificity of concealed entrainment (CE) for the identification of a critical isthmus in the atrium.

BACKGROUND

Isthmus identification during entrainment mapping of macro-reentrant atrial tachycardia (MRAT) relies on the demonstration of CE.

METHODS

Using the model of typical atrial flutter, entrainment was performed in 10 patients at four rates (flutter cycle length [FCL] minus 10/20/30/40 ms) from seven sites: isthmus entrance/exit, low lateral/high lateral/high septal right atrium and proximal/distal coronary sinus. Surface 12-lead electrocardiogram fusion was evaluated by three observers blind to patient status. The extent of antidromic penetration (AP) was measured off the pacing catheter positioned around the tricuspid annulus.

RESULTS

The sensitivity for CE identifying any isthmus site was greatest at FCL–10 (100%), but the specificity was poor (54%). Conversely, specificity was greatest at FCL–40 (98%), but the sensitivity was poor (65%), with manifest entrainment (ME) observed from the isthmus entrance in 70% of episodes. At FCL–30, sensitivity (85%) and specificity (90%) were "balanced," but CE still resulted during entrainment from a non-isthmus site in five of 10 patients. Antidromic penetration increased with pacing CL shortening (p < 0.001) and correlated with the development of ME (p < 0.001). Antidromic penetration was significantly blunted from the isthmus exit compared to all other sites (p = 0.003).

CONCLUSIONS

The sensitivity and specificity of CE for identifying an isthmus in the atrium are critically dependent on the pacing rate and the precise anatomic pacing site within the isthmus. These findings may have implications for the use of entrainment in the mapping of unknown MRAT circuits.

Abbreviations and Acronyms   AFL = atrial flutter   AP = antidromic penetration   AV = atrioventricular   CE = concealed entrainment   CS = coronary sinus   DCS = distal coronary sinus   ECG = electrocardiogram   FCL = flutter cycle length   HLRA = high lateral right atrium   HSRA = high septal right atrium   LAO = left anterior oblique   LLRA = low lateral right atrium   ME = manifest entrainment   PCS = proximal coronary sinus   PPI = post-pacing interval   RA = right atrium   RFA = radiofrequency ablation   TA = tricuspid annulus   TCL = tachycardia cycle length

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