24. Entrainment of wide complex tachycardia by atrial stimulation is highly accurate and can rapidly elucidate the tachycardia mechanism through analysis of entrainment response

Abstract

Although the diagnosis of wide-complex tachycardia (WCT) in the Electrophysiology Laboratory is usually straightforward, occasionally a WCT with 1:1 AV relationship can pose a diagnostic challenge. Furthermore, different responses to entrainment have been reported in relation to the pacing site of a variety of tachycardias, however, transient atrial entrainment of WCT has not been investigated sufficiently and systematically .We studied the response to atrial overdrive pacing to clarify the tachycardia mechanism. Out of 43 consecutive patients who underwent catheter ablation for WCT, we prospectively studied 28 patients (65%, mean age 33 ± 11 years) with WCT and 1:1 AV relationship in whom response to atrial overdrive pacing could be evaluated. During the tachycardia, atrial overdrive pacing was performed. The following responses were observed: A change of the QRS morphology during atrial pacing. The first return electrogram of the tachycardia, whether occurring in the atrium (AVA response) or in the ventricle (AVVA response). Atrial post-pacing interval (PPI) measured to the return A at the pacing site. The difference between PPI and tachycardia cycle length (PPI-TCL). Atrial overdrive pacing was successfully performed in 28 patients. It was associated with either a change or narrowing of the QRS in all ventricular tachycardia (VT, n = 7) patients but not in supraventricular tachycardia (SVT, n = 21) patients. All VT patients had an AVVA response upon cessation of atrial overdrive pacing as opposed to AVA response in SVT patients, p < 0.001. PPI and PPI-TCL were significantly longer in VT patients (640;± 92 ms vs. 378;± 49 ms, p < 0.001 and 294;± 75 ms vs. 70;± 40 ms, p < 0.001 respectively). Receiver operator characteristics curve identified PPI-TCL >160 ms as 100% sensitive and specific for diagnosing VT (p < 0.001). Response to atrial entrainment can be helpful in the majority of WCT patients, particularly those with 1:1 AV relationship to diagnose or rule out VT as a mechanism of tachycardia with high accuracy.