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(Circulation. 2005;111:969-974.)
© 2005 American Heart Association, Inc.

Arrhythmia/Electrophysiology

T-Vector Direction Differentiates Postpacing From Ischemic T-Wave Inversion in Precordial Leads

From the Beth Israel Deaconess Medical Center (A.S., K.K.L.H., M.E.J.), Boston, Mass, and the Center for Molecular Therapeutics (M.R.R.), Columbia University, New York, NY.

Correspondence to Mark E. Josephson, Baker4/Cardiology, Beth Israel Deaconess Medical Center, 185 Pilgrim Rd, Boston, MA 02215. E-mail mjoseph2{at}bidmc.harvard.edu

Received May 30, 2004; revision received November 17, 2004; accepted November 23, 2004.

Background— Postpacing precordial T-wave inversion (TWI), known as cardiac memory (CM), mimics ischemic precordial TWI, and there are no established ECG criteria that adequately distinguish between the two. On the basis of CM properties (postpacing sinus rhythm T vector approaching the direction of the paced QRS vector), we hypothesized that CM induced by right ventricular pacing would manifest a TWI pattern different from that of precordial ischemic TWI, thereby discriminating between the two.

Methods and Results— T-wave axis, polarity, and amplitude on a 12-lead ECG during sinus rhythm were compared between CM and ischemic patients. The CM group incorporated 13 patients who were paced in DDD mode with short atrioventricular delay for 1 week after elective pacemaker implantation. The ischemic group consisted of 47 patients with precordial TWI identified among 228 consecutive patients undergoing percutaneous coronary intervention for an acute coronary syndrome. The combination of (1) positive T_aVL, (2) positive or isoelectric T_I, and (3) maximal precordial TWI>TWI_III was 92% sensitive and 100% specific for CM, discriminating it from ischemic precordial TWI.

Conclusions— CM induced by right ventricular pacing results in a distinctive T-vector pattern that allows discrimination from ischemic precordial T-wave inversions regardless of the coronary artery involved.

Key Words: electrocardiography • pacing • ischemia

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