Lin J L, Lai L P, Lin L J, Tseng Y Z, Lien W P, Huang S K
Department of Internal Medicine, National Taiwan University Hospital, 7 Chung-Shan South Road, Taipei 10018, Taiwan.
Heart. 1999 Jan;81(1):73-81. doi: 10.1136/hrt.81.1.73.
To investigate the electrophysiological determinant underlying the electrical induction of counterclockwise and clockwise isthmus dependent atrial flutter.
The isthmus bordered by the inferior vena caval orifice-tricuspid annulus-coronary sinus ostium (IVCO-TA-CSO) has been assumed to be the site of both slow conduction and unidirectional block critical to the initiation of atrial flutter. Trans-isthmus and the global atrial conduction were studied in 25 patients with isthmus dependent atrial flutter (group A) and in 21 patients without atrial flutter (group B), by pacing at the coronary sinus ostium and the low lateral right atrium (LLRA) and mapping with a 20 pole Halo catheter in the right atrium.
Mean (SD) fluoroscopic isthmus length between the coronary sinus ostium and LLRA sites was 28.1 (4.0) mm in group A and 28.0 (3.9) mm in group B (p = 0.95), but the trans-isthmus conduction velocity of both directions at various pacing cycle lengths was nearly halved in group A compared with group B (mean 0.39-0.46 m/s v 0.83-0.89 m/s, p < 0.0001). Pacing at coronary sinus ostium directly induced counterclockwise atrial flutter in 14 patients and pacing at LLRA induced clockwise atrial flutter in 11 patients, following abrupt unidirectional trans-isthmus block. Transient atrial tachyarrhythmias preceded the onset of atrial flutter in 10 counterclockwise and six clockwise cases of atrial flutter. None of the group B patients had inducible atrial flutter even in the presence of trans-isthmus block. The intra- and interatrial conduction times, as well as the conduction velocities at the right atrial free wall and the septum, were similar and largely within the normal range in both groups.
Critical slowing of the trans-IVCO-TA-CSO isthmus conduction, but not the unidirectional block or the global atrial performance, is the electrophysiological determinant of the induction of counterclockwise and clockwise isthmus dependent atrial flutter in man.
研究逆时针和顺时针峡部依赖性房扑电诱导的电生理决定因素。
下腔静脉口 - 三尖瓣环 - 冠状窦口（IVCO - TA - CSO）界定的峡部被认为是对房扑起始至关重要的缓慢传导和单向阻滞部位。通过在冠状窦口和右房低侧壁（LLRA）起搏，并使用20极Halo导管在右房进行标测，对25例峡部依赖性房扑患者（A组）和21例无房扑患者（B组）的峡部及全心房传导进行了研究。
A组冠状窦口与LLRA部位之间的透视峡部平均（标准差）长度为28.1（4.0）mm，B组为28.0（3.9）mm（p = 0.95），但与B组相比，A组在不同起搏周期长度下两个方向的峡部传导速度几乎减半（平均0.39 - 0.46 m/s对0.83 - 0.89 m/s，p < 0.0001）。在冠状窦口起搏直接诱发了14例患者的逆时针房扑，在LLRA起搏诱发了11例患者的顺时针房扑，随后出现突然的单向峡部阻滞。在10例逆时针和6例顺时针房扑病例中，房扑发作前出现了短暂房性快速心律失常。B组患者即使存在峡部阻滞也无诱发性房扑。两组的房内和房间传导时间，以及右房游离壁和间隔的传导速度相似，且大多在正常范围内。
经IVCO - TA - CSO峡部传导的显著减慢而非单向阻滞或全心房功能，是人类诱发逆时针和顺时针峡部依赖性房扑的电生理决定因素。
