Title: The ?stone heart?: A challenge to the biochemist
Abstract: Identification of ischemic contracture in the human heart (“stone heart”) by Cooley et al.’ in this issue highlights the growing importance of an understanding of muscle biochemistry in the analysis and therapy of cardiac disease. This syndrome, which accounted for over a quarter of their operative deaths due to acute myocardial failure, appears to represent a condition analogous to rigo?+ in skeletal muscle. The appearance of these hearts, “contracted . . . similar to the uterine contraction ring” with severely reduced ventricular chamber volume, and the spread of the contracture from the less well perfused subendocardial myocardium toward the epicardium, supports the interpretation that this condition represents rigor. If this view is correct, then the “stone heart” may be the result of a known biochemical mechanism, but one which apparently has not previously been described in the human heart. Biochemical mechanism : When myocardial ischemia is due to coronary artery occlusion, the response of the heart is quite different from that described by Cooley et al. Myocardial contractile force decreases within seconds after cessation of coronary flow so that after less than a minute the weakened ischemic myocardium bulges outward during systole.2 This phenomenon, so commonly seen by the cardiologist, probably results from an abnormality in excitation-contraction coupling, those processes by which a propagated action potential initiates the activity of the heart’s contractile proteins.3s4 In contrast, the “stone heart” represents an entirely different mechanism of ischemit myocardial failure, due not to failure of excitation-contraction coupling, but instead to a failure of the ischemic myocardium to relax. This state of rigor can be attributed to loss of myocardial energy stores, leading to adenosine triphosphate (ATP) depletion in the region of the cardiac cell occupied by the myofilaments. A dual action of ATP on the cardiac contractile proteins in vitro has long been recognized.“,” On the one hand, ATP promotes contraction by causing actin and myosin to interact, whereas under different experimental conditions (increasing ionic
Publication Year: 1972
Publication Date: 1972-04-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 140
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