Limited data are available concerning the effects of mild-to-moderate, sustained reductions of coronary blood flow on myocardial aerobic metabolism. This study tested the hypothesis that a sustained flow reduction distal to a severe
coronary artery stenosis may be well tolerated (after the initial insult is passed) because of gradual improvement in the balance between myocardial
oxygen supply and demand. Studies were performed in eight sedated, closed-chest domestic swine that were instrumented with an artificial coronary arterial
stenosis (80% diameter reduction). Hemodynamics, regional myocardial blood flow and
oxygen,
lactate,
acid, and base metabolism were measured before
stenosis and at 5, 20, 60, 120, and 180 minutes after
stenosis insertion. Regional myocardial function (ultrasonic length sensors) was measured serially during 2 hours in three additional swine. After
stenosis placement, endocardial and transmural flows declined (p less than 0.05) compared with flows before
stenosis (from 1.54 +/- 0.37 to 0.73 +/- 0.24 ml/min/g [mean +/- SD] and from 1.44 +/- 0.31 to 1.19 +/- 0.25 ml/min/g, respectively). Thereafter, flows remained unchanged for the duration of the study. Similarly, prestenosis heart rate (135 +/- 7 beats/min), aortic mean pressure (113 +/- 17 mm Hg), and tension time index (27.1 +/- 3.6 mm Hg.sec) remained constant for the duration of the study. In contrast, regional coronary venous pH declined (p less than 0.05) compared with prestenosis levels (7.35 +/- 0.02) 5 minutes after
stenosis (7.28 +/- 0.04), but it returned to prestenosis levels during the next hour. Regional coronary venous PCO2 exhibited a similar pattern (i.e., acute increase during poststenosis with gradual return to prestenosis levels).(ABSTRACT TRUNCATED AT 250 WORDS)