Chronic stunning: The new switch in thought

Abstract

One picture may be worth a thousand words, as they say, but I was asked to write the thousand words and not to provide the picture. My major point can in fact be made in even fewer words. Despite the unanimous acceptance of the standard definition of stunning (1), it appears that this includes vastly different experimental and clinical conditions. Regarding the definition-according to Bolli (1), it is a state in which myocardial blood flow is fully restored following prior ischemia and during which time myocardial mechanical function is depressed. A further feature is that there is no evidence of myocardial necrosis.

The range of experimental conditions covered by this definition is demonstrated by Lavellee et al. (7) who showed progressive recovery following 1 h of coronary artery occlusion in a dog, and a state of stunning lasting at least 2 weeks. As expected with such prolonged periods of ischemia, where there must be some necrosis, mechanical recovery was incomplete. Presumably, however, there was no necrosis in the segments that did recover. In contrast, Du Toit and Opie (4) used an isolated rat heart model with 20 min of global ischemia in which stunning lasted for only about 1 h. Other workers using dog models (11) have described intermediate durations of stunning of some hours, even following a short period of coronary occlusion such as 15 min.

Likewise, clinical stunning may last for only short periods, such as following the severe ischemia caused by balloon inflation during angioplasty which causes transient diastolic dysfunction (8). It is likely that the transient dys function observed after an attack of angina pectoris also falls into the short-term category of stunning. At the other extreme is prolonged ischemia over hours, days and possibly weeks following thrombolytic therapy or cardioplegic bypass (3, 8).

In principle it seems unlikely that the same processes would be at work in a short-term, self-correcting phenomenon as in a more complex, long-term, and only partially self-remedying phenomenon. It therefore seems appropriate to distinguish between acute short-term and chronic long-term stunning.