Summary
The time constant of left ventricular pressure fall (TB, P = P0 + A. e-t/TB) is a good indicator of myocardial relaxation, but the physiological nature of the asymptote (P0) is not yet clear. The effects of hypoxia and the combined effects of hypoxia and DPI 201-106 (DPI, 10-6 M and 3 × 10-6 M), a new cardiotonic agent which increases the sensitivity of contractile elements to Ca2+, on diastolic myocardial function in isolated isovolumic rabbit hearts were investigated. There were close correlations between the change in left ventricular end-diastolic pressure (⊿A LVEDP) and ⊿P0 (r = 0.98, P < 0.01) and between ⊿TB and ⊿LVEDP (r = 0.73, P < 0.01) following hypoxia. The combination of hypoxia and DPI induced further increments in LVEDP (25 ± 8 mmHg, P < 0.05 vs hypoxia) and P0 (15 ± 7 mmHg, P < 0.05), and still there was a close linear correlation between ⊿LVEDP and ⊿P0 (y = 1.08x + 1.5, r = 0.90, P < 0.05). However, TB(52 ± 12 ms) was not altered and no relationship was observed between ⊿TB and ⊿LVEDP.
P0 reflected LVEDP in isolated isovolumic heart. The discrepancy between the changes in TB and P0 induced by DPI suggest different mechanisms underlying the changes in left ventricular diastolic stiffness and relaxation.
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© 1989 Springer-Verlag Tokyo
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Serizawa, T., Kohmoto, O., Iizuka, M., Ohya, T., Momomura, Si., Sugimoto, T. (1989). Discrepancy Between Slow Relaxation and Increased Myocardial Stiffness. In: Hori, M., Suga, H., Baan, J., Yellin, E.L. (eds) Cardiac Mechanics and Function in the Normal and Diseased Heart. Springer, Tokyo. https://doi.org/10.1007/978-4-431-67957-8_13
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DOI: https://doi.org/10.1007/978-4-431-67957-8_13
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