<原著>冠血流のparadoxical fallに関する実験的考察

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It has been known that coronary vascular bed dilates maximally and augments coronary flow in response to an increase in myocardial oxygen consumption. However, there is a possibility that, if there is a stenosis of coronary artery and coronary flow is reduced, this normal coronary response is no longer present and coronary flow will paradoxically fall even when myocardial oxygen demand increases and aggravates myocardial ischemia. The present study was designed to confirm this paradoxical phenomenon. In the first experiment, the left anterior descending coronary artery (LAD) was perfused with arterial blood from the carotid artery at a constant rate using a peristaltic pump and heart rate was increased by pacing to increase myocardial oxygen consumption. When the perfusion rate was maintained, an increase of heart rate caused a significant decrease in coronary perfusion pressure and a decrease in calculated coronary vascular resistance, indicating that coronary vascular bed dilated significantly in response to the increase in myocardial oxygen consumption. However, when the perfusion rate was reduced, a similar increase in heart rate caused an elevation in perfusion pressure, demonstrating that coronary vascular response is paradoxical at a relatively low coronary flow compared with a higher flow. In the second experiment, LAD was perfused with blood from the carotid artery at a pressure of its own carotid artery and heart rate was also increased by pacing. When the perfusion rate was higher, an increase in heart rate augmented perfusion rate, indicating coronary vascular bed dilated significantly to meet the increased myocardial oxygen consumption. On the contrary, when the perfusion rate was reduced using an occluder applied on the bypath circuit from carotid artery to LAD, a similar increase in heart rate caused again an opposite change in coronary vascular resistance, characterized by a fall in perfusion rate. In the third experiment, LAD was perfused at a constant rate using the peristaltic pump with blood either from left atrium (arterial blood; pO_2 95.4±4.4mmHg) or right atrium (venous blood; pO_2 43.0±5.9mmHg). When the perfusion blood was transferred from arterial blood to venous blood at a relatively high perfusion rate, there was a marked decrease in perfusion pressure, indicating coronary vascular bed dilated considerably in order to ameliorate myocardial tissue hypoxia. However, this normal response was again disappeared at a relatively low flow. When the perfusion rate was low, coronary perfusion pressure was slightly elevated by venous blood perfusion. The results obtained from the separate three experiments were consistent in that ; if the coronary flow is reduced, the normal coronary vascular response preventing ischemia does not take place but the opposite response occurs characterized by a further decrease in coronary flow, leading to the deterioration of the myocardium. The increase in extravascular compression on the coronary vascular bed would be one of the possible reasons to elicite this paradoxical fall in coronary flow. This study suggested that, in patients with severe coronary artery stenosis, some physical stimuli to induce myocardial ischemia might cause paradoxical fall of the coronary flow in the underperfused area which aggravated ischemia and eventually might develop myocardial infarction.
近畿大学の論文
1984-12-30

<原著>冠血流のparadoxical fallに関する実験的考察

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