WPW症候群における心房細動の発生機序に関する検討

The Mechanisms of the Onset of Atrial Fibrillation in the Wolff-Parkinson-White Syndrome

　頻拍発作を有するWPW症候群100例および房室結節リエントリー性頻拍症（AVNRT）30例を対象に心房細動（af）の生じる頻度および心房受攻性の指標などについて検討した．afの出現頻度はAVNRT群の3例（10％）に比しWPW症候群では49例（49％）と有意に大であり，副伝導路の存在がafの出現に関与していると考えられた．WPW症候群のaf（＋）群ではaf（—）群およびAVNRT群に比し，心房不応期は有意に短く，FRPA／PAで表せる心房インパルスの相対的最小波長は有意に小であった．心房受攻性の指標として高位右房早期刺激による高位右房波の持続時間の延長度の最大値max D₂／D₁，D₂／D₁が1.5以上を示すfragmented atrial activity zone，心房波の持続時間が20msec以下延長するconductiondelay zoneおよびrapid atrial firing（RAF）zoneを求めた．これら指標およびRAF（＋）例の頻度はaf（＋）群で有意に大であったことからWPW症候群におけるafの出現には副伝導路の存在に加え心房の特性も重要な役割を果たしていると考えられた．

We examined the frequency of atrial fibrillation (af) and atrial vulnerability in 100 WPW syndrome patients (42±16years) with a history of tachycardia (atrio-ventricular reciprocating tachycardia 97 patients, af 28 patients) and 30 patients (52±15years) with a history of atrioventricular nodal reentrant tachycardia (AVNRT). Af was induced in 49 patients (49%) in WPW syndrome (af (+) group) and 3 patients (10%) in AVNRT (p＜0.01). In the af (+) group, the atrial refractory periods and the potential minimal wave length of an atrial impulse (FRP_A/PA) were significantly shorter than in af (-) WPW syndrome group and AVNRT group. Fragmented atrial activity zone (an increase of 150% or more in the duration of the high right atrial electrogram), repetitive atrial firing zone (three or more successive atrial electrograms in-duced by a premature stimulation), and conduction delay zone (an increase of 20msec or more in the con-duction time in the high right atrial, the low right atrial and the distal coronary sinus electrograms) were significantly wider in af (+) group than in af (-) WPW syndrome group and AVNRT group. In conclusion, these data suggest that the presence of accessory path-ways and atrial properties affect af, and atrial vulnera-bility plays an important role in the onset of af in WPW syndrome.