Key result
In diseased human atrial muscle preparations, electrical pacing induced triggered activity in 47% of quiescent samples and postoverdrive acceleration in spontaneously active samples.
Pacing of diseased human atrial muscle induces triggered activity and postoverdrive acceleration, driven by a balance between intracellular calcium-mediated transient inward currents and extracellular potassium accumulation.
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Should not yet change clinical practice; hypothesis-generating for triggered activity in diseased human atria.
病的ヒト心房筋標本の中には, 正常Tyrode液下で自動放電を示すものが45.5%あり, 残りの自動性を示さない標本においてもpacingすると47%にtriggered activity (TA) が誘発された.すなわち当標本の71%に異常自動能発生の可能性が潜んでいる.自動放電の周期が2秒以上の比較的遅い自動能をpacingするとpostoverdrive acceleration (POA) が生じ, 一過性に周期が2秒以下の速い自動能へと移行する.ここにみられたPOAはryanodine存在下でほぼ完全に消失し, この自動性の加速は細胞内Ca2+増加に伴う筋小胞体機能が関与した機序に基づくことが判明した.一方静止標本をpacingすると細胞内にはCa2+増加が, 細胞直外にはK+の蓄積が起こり, 前者は一過性内向き電流を惹起しTA発生を促進するが, 後者は膜のK+透過性を増加しTA発生に対して抑制的に作用する.病的ヒト心房筋に見られるTAの電気生理学的特性は, 相反する両者の電流系のバランスによって規定されていると考えられる.
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SANAO IMANISHI (1988) studied Diseased human atrial muscle (patients undergoing open heart surgery) (n=79). Electrical pacing vs. Baseline (unpaced) was evaluated on Induction of triggered activity in quiescent preparations. In diseased human atrial muscle preparations, electrical pacing induced triggered activity in 47% of quiescent samples and postoverdrive acceleration in spontaneously active samples.
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