Tohoku J. Exp. Med., 2002, 198 (2)

Post-Endsystolic Active Shortening in the Non-Ischemic Region Impairs
Left Ventricular Pressure Fall in Acute Ischemic Heart

HIDENARI HOZAWA, MASAHITO SAKUMA, MAKOTO NAKAGAWA, HIDEHIKO ISHIGAKI, KOHTAROH KOMAKI,
YOSHITO YAMAMOTO, JUN IKEDA, YUTAKA KAGAYA, JUN WATANABE and KUNIO SHIRATO

Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai 980-8574

To investigate the relation between the impairment of isovolumic relaxation and the regional wall motion in acute ischemia, the left ventricular pressure fall and regional myocardial motion were examined in the relaxation phase in dogs during both acute coronary artery occlusion (n=12) and a regional coronary flow reduction (n=6). Fifteen to 40 seconds after complete coronary artery occlusion or in the stable state after a regional coronary flow reduction by 70 to 90% of the control state, a shortening of the non-ischemic region at the early isovolumic relaxation phase (the post-endsystolic shortening) appeared, combined with lengthening of the ischemic region. In these situations, the logarithmic plots of the left ventricular pressure fall was composed of two components (time constant of early part [Ta] and at latter part [Tb]). Ta was greater than Tb (64.3±13.8 milliseconds vs. 36.6±10.4 milliseconds at 15 seconds after coronary occlusion, p<0.01; 67.6±22.9 milliseconds vs. 45.1±17.5 milliseconds at flow reduction, p<0.01) and the time constant at control (p<0.01). These findings suggested that post-endsystolic shortening in the non-ischemic region played a role in a the non-uniformity of the left ventricular contraction and contributed to the impairment of the left ventricular pressure fall in acute regional ischemia, especially in early isovolumic relaxation.

Keywords —— relaxation; time constant; ischemic heart

© 2002 Tohoku University Medical Press

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Tohoku J. Exp. Med., 2002, 198, 107-118

Address for reprints: Kunio Shirato, Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, 1-1 Seiryomachi, Aoba-ku, Sendai 980-8574, Japan.

e-mail: shirato@int1.med.tohoku.ac.jp