Focal atrial tachycardias originating from the aorta-mitral continuty: Anatomic and electrophysiological characteristics.

BACKGROUND: The aorta-mitral annulus conjunction (AMC) is uncommon site of origin of focal atrial tachycardias (AT). Hence, the electrophysiological and ablation target characteristics are poorly described.

OBJECTIVE: To describe the characteristics of AMC AT in detail.

METHODS: The study enrolled 650 patients with AT, 21 (3.2%) of whom had AT originating from AMC. A comprehensive evaluation, including electrocardiography, electrophysiologic study, CT scan, and intracardiac echocardiography (ICE) was performed.

RESULTS: The majority (90.5%) of ATs occurred spontaneously. The average age of this group was 48.9±21.6 years, with 12 females (57.1%). Seventeen patients had a typical biphasic P wave with a prominent positive component. The earliest activation site in the right atrium was near the His bundle with average activation -10.3±6.0 ms preceding the P wave. The successful ablation targets were distributed as follows: 1 case at 9 o'clock, 6 cases at 10 o'clock, 7 cases at 11 o'clock, 6 cases at 12 o'clock, and 1 case in the left coronary cusp (LCC). The local AMC potential differed from the commonly perceived annular potential, and was characterized by a large A and a small V (A/V ratio >1). The angle of encroachment on the LA anterior wall, compressed by the LCC, was significantly smaller in the AMC-AT group compared to the control group, which may have contributed to the arrhythmia substrate (141.7°±11.5° vs. 155.2°±13.9°, p = 0.026).

CONCLUSION: A new strategy for mapping AMC ATs has been introduced. The ablation target should have an A/V ratio greater than 1.