Discrepancy Between Slow Relaxation and Increased Myocardial Stiffness
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.
KeywordsMyocardial Stiffness Peak Systolic Pressure Diastolic Stiffness Cardiotonic Agent Ventricular Diastolic Pressure
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Glantz SA, Parmley WW (1978) Factors which affect the diastolic pressure-volume curve. Circ Res 42: 171–180PubMedGoogle Scholar
Grossman W, Barry WH (1980) Diastolic pressure-volume relations in the diseased heart. Fed Proc 39: 148–155PubMedGoogle Scholar
Grossman W (1985) Why is left ventricular diastolic pressure increased during angina pectoris? J Am Coll Cardiol 5: 607–608CrossRefGoogle Scholar
Ross J Jr (1979) Acute displacement of the diastolic pressure-volume curve of the left ventricle: role of the pericardium and the right ventricle. Circulation 59: 32–37PubMedGoogle Scholar
Serizawa T, Carabello BA, Grossman W (1980) Effects of pacing-induced ischemia on left ventricular diastolic pressure-volume relations in dogs with coronary stenoses. Circ Res 46: 430–439PubMedGoogle Scholar
Paulus WJ, Serizawa T, Grossman W (1982) Altered left ventricular diastolic properties during pacing-induced ischemia in dogs with coronary stenoses: potentiation by caffeine. Circ Res 50: 218–227PubMedGoogle Scholar
Bourdillon PD, Lorell BH, Mirsky I, Paulus WJ, Wynne J, Grossman W (1983) Increased regional myocardial stiffness of the left ventricle during pacing-induced angina in man. Circulation 67: 316–323PubMedCrossRefGoogle Scholar
Sasayama S, Nonogi H, Miyazaki S, Sakurai T, Kawai C, Eiho S, Kuwahara M (1985) Changes in diastolic properties of the regional myocardium during pacing-induced ischemia in human subjects. J Am Coll Cardiol 5: 599–606PubMedCrossRefGoogle Scholar
Lorell BH, Wexler LF, Momomura S, Weinberg E, Apstein CS (1986) The influence of pressure overload left ventricular hypertrophy on diastolic properties during hypoxia in isovolumically contracting rat hearts. Circ Res 58: 653–663PubMedGoogle Scholar
Serizawa T, Vogel WM, Apstein CS, Grossman W (1981) Comparison of acute alterations in left ventricular relaxation and diastolic chamber stiffness induced by hypoxia and ischemia: role of myocardial oxygen supply-demand imbalance. J Clin Invest 64: 91–102CrossRefGoogle Scholar
Weisfeldt ML, Frederiksen JW, Yin FCP, Weiss JL (1978) Evidence of incomplete left ventricular relaxation in the dog. J Clin Invest 62: 1296–1302PubMedCrossRefGoogle Scholar
Scholtysik G, Salzmann R, Berthold R, Herzig JW, Quast U, Markstein R (1985) DPI 201-106, a novel cardioactive agent. Combination of cAMP-independent positive inotropic, negative chronotropic, action potential prolonging and coronary dilatory properties. Arch Pharm 329: 316–325CrossRefGoogle Scholar
Parmley WW, Sonnenblick EH (1969) Relation between mechanics of contraction and relaxation in mammalian cardiac muscle. Am J Physiol 216: 1084–1091PubMedGoogle Scholar
Weiss JL, Frederiksen JW, Weisfeldt ML (1976) Hemodynamic determinats of the time course of fall in canine ventricular pressure. J Clin Invest 58: 751–776PubMedCrossRefGoogle Scholar
Thomspon DS, Waldron CB, Juul SM, Naqvi N, Swanton RH, Coltart DJ, Jenkins BS, Webb-Peploe MM (1982) Analysis of left ventricular pressure during isovolumic relaxation in coronary artery disease. Circulation 65: 690–697CrossRefGoogle Scholar
Carroll JD, Hess OM, Hirzel HO, Krayenbuehl HP (1983) Exercise-induced ischemia: The influence of altered relaxation on early diastolic pressures. Circulation 67: 521–527PubMedCrossRefGoogle Scholar
Raff GL, Glantz SA (1981) Volume loading slows left ventricular isovolumic relaxation rate: evidence of load-dependent relaxation in the intact dog heart. Circ Res 48: 813–824PubMedGoogle Scholar
Serizawa T, Momomura S, Kohmoto O, Ohya T, Sato H, Takahashi T, Mochizuki T, Iizuka M, Sugimoto T (1987) Mechanisms of abnormal relaxation induced by ischemia: comparison of low flow ischemia and hypoxia in isolated rabbit heart. Jpn Circulation J 51: 90–97CrossRefGoogle Scholar
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