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The local distribution of coronary collateral flow was mapped using 8 mu tracer microspheres following circumflex coronary occlusions in dogs. Overall flow to the ischaemic posterior papillary muscle and subjacent myocardium decreased to 21% of anterior free wall flow. Collateral flow was non-uniform, however, and was lower in the subendocardium (14%) than in the subepicardium (27%). Brief temporary occlusions with and without propranolol therapy showed that collateral flow was less and the inner/outer wall ratio was unaltered in treated animals. Although propranolol reduces infarct size after coronary occlusions, this effect appears not to be related to increases in collateral flow.
Kloner et al. (1976) studied this question.
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