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  • Title: Coupling between regional myocardial oxygen consumption and contraction under altered preload and afterload.
    Author: Goto Y, Futaki S, Kawaguchi O, Hata K, Takasago T, Saeki A, Nishioka T, Taylor TW, Suga H.
    Journal: J Am Coll Cardiol; 1993 May; 21(6):1522-31. PubMed ID: 8473665.
    Abstract:
    OBJECTIVES: This study was designed to assess the relation between left ventricular regional myocardial oxygen consumption (VO2) and variables of regional myocardial contractile function under various loading conditions. BACKGROUND: Although the relation between global VO2 and global ventricular function has been extensively studied, the relation between regional VO2 and regional myocardial contraction is not fully understood. METHODS: Myocardial shortening (regional area shrinkage), regional work, regional total mechanical energy index and regional VO2 were measured under variously altered loading conditions in the isolated, blood-perfused dog left ventricle. Regional total mechanical energy per beat was quantified by wall tension-regional area area (TAA) by the analogy of left ventricular pressure-volume area. Left ventricular loading conditions were altered by changing end-diastolic volume and stroke volume with a servo pump as follows: 1) increased preload (increased end-diastolic volume and stroke volume at a constant ejection fraction), 2) decreased afterload (increased stroke volume at a constant end-diastolic volume), 3) increased preload and afterload (increased end-diastolic volume at a constant stroke volume), and 4) altered mode of contraction (ejecting vs. isovolumetric contractions). RESULTS: During increased preload, all three variables correlated positively with regional VO2 (r = 0.78 to 1.00). During decreased afterload, the correlation was negative for area shrinkage (r = -0.65 to -0.91) and variable for regional work (r = -0.55 to 0.98) but positive and highly linear for TAA (r = 0.80 to 0.99). During increased preload and afterload, the correlation was again negative for area shrinkage (r = -0.77 to -0.97) but positive for regional work (r = 0.83 to 0.93) and TAA (r = 0.95 to 0.99). During altered mode of contraction, the correlation was insignificant for area shrinkage (r = 0.24 to 0.57) and moderate for regional work (r = 0.50 to 0.79), whereas again highly linear for TAA (r = 0.95 to 0.98). Thus, only TAA correlated closely with regional VO2 under any loading conditions. Furthermore, the slope and regional VO2 intercept of the regional VO2-TAA relation was remarkably consistent among the different hearts and loading conditions. CONCLUSIONS: We conclude that there is a tight coupling between regional VO2 and regional total mechanical energy represented by TAA regardless of left ventricular afterload and preload conditions.
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