Mechanical activity of isolated canine coronary arteries after coronary occlusion.

Collateral vessels from dogs showed good mechanical responses, with well-developed inhibitory responses, for example to noradrenaline. Endogenous inhibitory processes, which resulted in a low spontaneous basal tone, were also well-developed in most tissues. However, signs of hyperactivity were observed in some cases - and this might be the most interesting result. This hyperactivity was characterized by a strong phasic spontaneous activity. This might be an abnormality associated with the rapid proliferation of smooth muscle cells in collateral vessels. It is quite possible that such states of hyperactivity may play a role in human pathology, Producing coronary spasm and leading to angina or infarction, perhaps even in hearts with well developed collaterals.