長時間運動後の左室機能—トライアスロン競技前後における変化

Left ventricular function after prolonged exercise

　過酷な耐久競技が心機能に及ぼす影響を検討する目的で，11例（平均30歳）についてトライアスロン競技（水泳3.2km，自転車161km，マラソン32km）終了直後（9分）の心エコー図を安静時ならびに短時間運動後のものと比較した。8例では回復期（終了15時間後）においても短時間運動前後に記録した。競技直後では競技前の短時間運動後と比較して左室拡張末期径，内径短縮率は低かった。前負荷の減少によると考えられたが，個々の例でみると短縮率の減少は拡張末期径とは関係なかった。収縮末期径とは相関した。またwall stressと最大内周短縮速度の関係も短時間運動後とは異なった。回復期においては競技前より拡張末期径は低値を示したが．左室ポンプ機能の指標は競技前に戻った。過酷な運動では短時間の運動では起こらない一過性のポンプ機能の低下がみられ，その一部は心収縮性自体の低下によると考えられた。

To determine whether depressed left ventricular (LV) contractile function can occur after exhaustive exercise, echocardiographic studies were performed in eleven athletes before, at the finish (9 minutes) and during recovery (15 hour) after the Biwa Lake Ironman Triathlon (3.2 km Swim, 161 km Bike, 32 km Run). Before racing and during recovery, the studies were performed both at rest and after brief exercise (10~15 minutes). Heart rates after brief exercise were comparable to those attained after racing. Digitized M mode echocardiographic data as to wall thickness, cavity dimension, fractionalshortening (FS) and peak circumferential shortening (maxVcf) were obtained. When we compared race finish to pre-race brief exercise, the LV end-diasto-lic dimension (EDD) was reduced (46±7 vs 47±6 mm, ＜0.05) and FS declined (33±5 vs 39±6%, p＜ 0.05). In spite of reduced wall stress, maxVcf decreased. Individual percent reductions in FS were not correlated with decrease in EDD, but correlated with increases in EDS. Although a persistent re-duction in cavity size was observed during recovery, FS and maxVcf returned toward the baseline. The results suggest that prolonged strenuous exercise may result in impaired LV function, in part because of a reversible depression in the contractile state.