Stunning of the heart muscle is a postischaemic dysfunction observed after reperfusion. The stunned heart muscle is functional, the restoration of contractility is slow. The stunning of the heart muscle is probably due to a partial disorder of the electromechanical mechanisms caused by impaired calcium homeostasis. Substances which protect against the development of stunning are substances which eliminate oxygen radicals and calcium channel blockers which adjust the calcium homeostasis in cells. The "hibernating myocardium" is a state of contractile dysfunction during chronic hypoperfusion of the heart muscle. When the blood flow is restored, the contractility improves gradually. The second generation of calcium antagonists is effective in hibernated heart muscles due to their selective coronary artery dilating effect.