Detailed analysis of tachycardia cycle length aids diagnosis of the mechanism and location of atrial tachycardias

Although the mechanism of an atrial tachycardia (AT) can usually be elucidated using modern high-resolution mapping systems, it would be helpful if the AT mechanism and circuit could be predicted before initiating mapping.

We examined if the information gathered from the cycle length (CL) of the tachycardia can help predict the AT-mechanism and its localization.

One hundred and thirty-eight activation maps of ATs including eight focal-ATs, 94 macroreentrant-ATs, and 36 localized-ATs in 95 patients were retrospectively reviewed. Maximal CL (MCL) and minimal CL (mCL) over a minute period were measured via a decapolar catheter in the coronary sinus. CL-variation and beat-by-beat CL-alternation were examined. Additionally, the CL-respiration correlation was analysed by the Rhythmia^TM system. : Both MCL and mCL were significantly shorter in macroreentrant-ATs [MCL = 288 (253–348) ms, P = 0.0001; mCL = 283 (243–341) ms, P = 0.0012], and also shorter in localized-ATs [MCL = 314 (261–349) ms, P = 0.0016; mCL = 295 (248–340) ms, P = 0.0047] compared to focal-ATs [MCL = 506 (421–555) ms, mCL = 427 (347–508) ms]. An absolute CL-variation (MCL-mCL) < 24 ms significantly differentiated re-entrant ATs from focal-ATs with a sensitivity = 96.9%, specificity = 100%, positive predictive value (PPV) = 100%, and negative predictive value (NPV) = 66.7%. The beat-by-beat CL-alternation was observed in 10/138 (7.2%), all of which showed the re-entrant mechanism, meaning that beat-by-beat CL-alternation was the strong sign of re-entrant mechanism (PPV = 100%). Although the CL-respiration correlation was observed in 28/138 (20.3%) of ATs, this was predominantly in right-atrium (RA)-ATs (24/41, 85.7%), rather than left atrium (LA)-ATs (4/97, 4.1%). A positive CL-respiration correlation highly predicted RA-ATs (PPV = 85.7%), and negative CL-respiration correlation probably suggested LA-ATs (NPV = 84.5%).

Detailed analysis of the tachycardia CL helps predict the AT-mechanism and the active AT chamber before an initial mapping.