Cheng J, Cabeen W R, Scheinman M M
Section of Cardiac Electrophysiology, University of California San Francisco, CA, USA.
Circulation. 1999 Apr 6;99(13):1700-5. doi: 10.1161/01.cir.99.13.1700.
The mechanisms of an atrial flutter (AFL) that is more rapid and at times more irregular than typical AFL are unknown.
Twenty-nine patients with AFL were studied. Atrial electrograms were recorded from a 20-pole catheter placed against the tricuspid annulus (TA), with its distal electrodes lateral to the isthmus between the TA and the eustachian ridge (ER), and from the His bundle and coronary sinus catheters. Atrial extrastimuli were delivered in the TA-ER isthmus during typical AFL. Episodes of a right atrial flutter rhythm that was different from typical AFL were induced in 3 patients and occurred spontaneously in 3 patients. This sustained AFL, designated as lower-loop reentry (LLR), involved the lower right atrium (RA), as manifested by early breakthrough in the lower RA, wave-front collision in the high lateral RA or septum, and conduction through the TA-ER isthmus. Linear ablation resulting in bidirectional conduction block in the TA-ER isthmus terminated spontaneous LLR in 3 patients and rendered LLR noninducible in all patients. The cycle length of LLR was shorter than that of typical AFL (217+/-32 versus 272+/-40 ms, P<0. 01). Alternating LLR and typical AFL in 1 patient resulted in cycle length oscillation.
LLR is a subtype of right atrial flutter and depends on conduction through the TA-ER isthmus.
比典型心房扑动（AFL）更快且有时更不规则的AFL机制尚不清楚。
对29例AFL患者进行了研究。使用置于三尖瓣环（TA）处的20极导管记录心房电图，其远端电极位于TA与欧氏嵴（ER）之间峡部的外侧，同时记录希氏束和冠状窦导管的电图。在典型AFL期间，在TA-ER峡部发放心房期外刺激。3例患者诱发出不同于典型AFL的右房扑动节律发作，3例患者为自发发作。这种持续性AFL被称为下环折返（LLR），累及右房下部（RA），表现为右房下部早期激动、右房高侧壁或间隔处的波前碰撞以及通过TA-ER峡部的传导。导致TA-ER峡部双向传导阻滞的线性消融终止了3例患者的自发LLR，并使所有患者的LLR均不能被诱发。LLR的周长比典型AFL短（217±32对272±40毫秒，P<0.01）。1例患者中LLR与典型AFL交替出现导致周长振荡。
LLR是右房扑动的一种亚型，依赖于通过TA-ER峡部的传导。
