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Ann Thorac Surg 1999;68:1913-1919
© 1999 The Society of Thoracic Surgeons

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I. Pathophysiology of Ischemic Reperfusion Injury

Prime causes of rapid cardiomyocyte death during reperfusion

^a Physiologisches Institut, Klinikum der Justus-Liebig-Universität, Giessen, Germany
^b Servicio de Cardiología, Hospital General Vall d’Hebron, Barcelona, Spain

Address reprint requests to Dr Piper, Physiologisches Institut, Klinikum der Justus-Liebig-Universität, Aulweg 129, D-35392 Giessen, Germany
e-mail: michael.piper{at}physiologic.med.uni-giessen.de

Presented at the International Symposium on Myocardial Protection From Surgical Ischemic-Reperfusion Injury, Asheville, NC, Sep 21–24, 1997.

Abstract

In ischemic-reperfused myocardium, necrosis of cardiomyocytes may develop not only due to the ischemic conditions but also the specific circumstances of reperfusion. The existence of reperfusion injury becomes apparent when modifications of the conditions of reperfusion can prevent cell death otherwise occurring. Three prime causes of rapidly developing reperfusion injury are here discussed, ie, reenergization of cells at increased cytosolic Ca²⁺ contents, rapid normalization of tissue pH, and rapid normalization of tissue osmolality. All three causes lead to severe mechanical stress of cardiomyocytes which can cause their rapid deterioration. Propagation of cell injury among adjacent cells can cause a spreading of necrosis throughout myocardial tissue. The understanding of these initial causes of rapidly developing lethal reperfusion injury leads to new concepts for specific protection of reperfused myocardium.

In cardiac surgery, the myocardium may suffer from ischemia. As a result of a successful revascularization or the end of the surgical procedures demanding interruption of blood flow, the ischemic myocardium may be reperfused. Ischemic or postischemic loss of viable myocardium is one of the major foes impairing an improvement of cardiac function after cardiac surgery. Many procedures have been designed to protect the myocardium against ischemic injury. In the past, the possibility—and need—to protect the myocardium during the first minutes to hours of reperfusion against "reperfusion injury" has been largely neglected. This may seem surprising as the cardiac surgeon can control precisely the conditions of reperfusion. This article is focused on the possibilities of protecting myocardial cells from death by modifying specifically the early conditions of reperfusion, ie, to protect against the early causes of lethal reperfusion injury. It describes novel strategies developed during the past decade in experimental research. The article does not deal with two other closely related topics which have been discussed extensively in several recent reviews. These are: reversible postischemic dysfunction, so-called stunning, and delayed causes of lethal reperfusion injury, eg, by activation of blood-borne noxes.

What is lethal reperfusion injury?

Lethal reperfusion injury is defined as injury caused by restoration of blood flow after an ischemic episode leading to death of cells that were only reversibly injured during that preceding ischemic episode. For lethal reperfusion injury to occur, ischemia has to set the stage without already producing irreversible injury itself. The definition thus comes with the corollary that ischemic alterations of cellular conditions are necessary prerequisites for lethal reperfusion injury, but not in themselves sufficient causes for cell death. When after extended ischemia, the myocardium is reperfused by simple restoration of coronary blood flow, analysis of the developing necrosis does not distinguish between cell death caused by the ischemic history or by reperfusion. The only valid criterion for the existence of reperfusion injury is whether modification of the conditions of reperfusion can prevent cell death, otherwise occurring in ischemic-reperfused myocardium. This criterion appears simpler than it is to apply, since many modifications of reperfusion conditions are possible, and failure to find one that reduces cell death in reperfused myocardium does not disprove the existence of reperfusion injury. As we argue below, causes of certain forms of lethal reperfusion injury have now been identified and, thus, some modifications of the conditions of reperfusion are indeed known to provide protection. We will here primarily discuss whether lethal reperfusion injury of cardiomyocytes (as opposed to other cells in the myocardium) can occur during the first minutes after reflow in the setting of ischemia-reperfusion, ie, we will concentrate on immediate lethal (necrotic) reperfusion injury. This can be distinguished from delayed lethal (necrotic) reperfusion injury which, eg, may be delivered to the cardiomyocytes by activated polymorphic neutrophils, and also from induction of apoptosis of cardiomyocytes in reperfused myocardium.

A short note on the role of oxygen radicals

There is clear evidence that, in reperfused myocardium, oxygen radicals are generated at a higher rate than in normal myocardium. Several sources seem to contribute to that increased production of oxygen radicals, ie, blood-borne cells such as activated neutrophiles, as well as constitutive cells of the myocardium such as cardiomyocytes and endothelial cells. The impact of oxygen radicals on the myocardial cells after ischemia may be increased since their antioxidative defense is reduced. A large number of experimental studies have been performed in which ischemic-reperfused myocardium has been treated by means directed against oxygen radicals. Several reviews from the past 5 years have summarized these studies and came to the sobering conclusion that they have failed to prove the hypothesis that oxygen radicals are crucially involved in the genesis of lethal reperfusion injury [1–3]. This conclusion was drawn because there is about an equal number of studies demonstrating improvement or no improvement of infarct size when antioxidant strategies are applied during reperfusion. Unfortunately, many researchers who had tried hard to prove the importance of oxygen radicals have thereafter lost hope altogether that the myocardium could be protected at the time of reperfusion or, in other words, they lost confidence in the existence of lethal reperfusion injury.

Why can lethal reperfusion injury develop so rapidly?

We address the question whether causes for immediate lethal reperfusion injury of cardiomyocytes exist in mammalian hearts and how one can interfere with their mechanisms. Since specific strategies against immediate reperfusion injury have never been applied to the human myocardium in vivo except for antioxidative treatment, it must remain open now if reperfusion protection represents a useful strategy in human therapy. Three potential initial causes of immediate reperfusion injury, apart from oxygen radicals, have been experimentally investigated in considerable detail, and will be briefly discussed: (cause 1) reenergization; (cause 2) rapid normalization of tissue pH; and (cause 3) rapid normalization of tissue osmolality.

These potential initial causes are not entirely independent. As outlined below, mechanical disruption of the sarcolemma appears to be the endpoint of immediate lethal reperfusion injury. Hypercontracture of the myofibrils is probably one of the major final causes. Hypercontracture is made possible by reenergization of the ischemic cell (cause 1) in which destructive contractile forces are generated due to Ca²⁺ overload and increased cytoskeletal fragility. Ischemic acidosis can attenuate this contractile activation. Rapid normalization of tissue pH (cause 2) can act as a permissive factor for hypercontracture elicited by reenergization and can also contribute to further Ca²⁺ overload. Cell swelling is the other major final cause for immediate lethal reperfusion injury. It originates in the reperfusion situation from a too rapid normalization of extracellular osmolality (cause 3), leaving the intercellular fluid hyperosmolar.

Why is the reenergization of myocardial cells harmful after prolonged ischemia?

About two decades ago, Hearse and coworkers [4] demonstrated that, in the oxygen depleted and reoxygenated myocardium, severe myocardial injury, characterized by myofibrillar hypercontracture and sarcolemmal disruption, may develop with the onset of reoxygenation. It has been demonstrated by Ganote and coworkers [5] that this injury is due to the resumption of energy production upon reoxygenation. This phenomenon of severe cell injury immediately provoked by reenergization has been termed "oxygen paradox." It has remained an open question for a long time whether the oxygen paradox represents genuine "reoxygenation injury" or just a dramatic manifestation of injury that has already developed during the oxygen depletion period. The presence of contraction bands in infarcted myocardium is a histological indicator of oxygen paradox injury in ischemic-reperfused myocardium. Histologic analysis clearly demonstrates that when reperfusion is performed early enough to produce some myocardial salvage, infarcts are composed almost exclusively of contraction band necrosis reflecting hypercontracture of myocytes, and there is evidence indicating that this hypercontracture occurs during the first minutes of reflow. Although contraction bands can be observed in the absence of necrosis in specific circumstances (as an artifact in biopsies), in the setting of reperfusion, hypercontractured myocytes invariably present signs of necrosis, indicating that, as opposed to what happens in isolated cardiomyocytes, reperfusion-induced hypercontracture is associated to sarcolemmal disruption and cell death.

Details of the causal mechanism of the oxygen paradox have now been identified in experimental studies using isolated cardiomyocytes (see below). These studies have shown that the oxygen paradox is indeed injury (i) brought about by the process of reoxygenation and (ii) based on a mechanism within the myocardial cell. Reenergization causes lethal cell injury by provocation of hypercontracture. The mechanism is the following: After prolonged energy depletion, cytosolic Ca²⁺ concentration is dramatically increased. Upon reenergization of the myocardial cell, made possible by resupply of oxygen to mitochondria, two processes are simultaneously activated: 1) The energy supply to cation pumps initiates recovery of the cellular cation balance; 2) resupply of energy to the myofibrillar elements initiates contractile activation.

(1) Under conditions of energy depletion, ie, in ischemic or hypoxic myocardium, the cytosol of the myocardial cells becomes loaded with Na⁺ and Ca²⁺. Recovery of energy production upon the resupply with oxygen and metabolic substrates rapidly reactivates two major cation pumps (Fig 1), namely, the Ca²⁺ pump (Ca²⁺-[adenosine triphosphate]ATPase) of the sarcoplasmic reticulum (SR) and the Na⁺ pump (Na⁺-K⁺-ATPase) of the sarcolemma, unless these pumps are themselves injured by the preceding ischemic conditions. Activation of the Ca²⁺ pump of the SR leads to a temporary sequestration of excess Ca²⁺ within this intracellular storage organelle [6, 7]. If the capacity of this organelle is too small for the amount of Ca²⁺ accumulated in the cytosol, a cycle of continuous release and reuptake of Ca²⁺ from and into the SR is initiated. These spontaneous oscillations come to an end only if the major mechanism for Ca²⁺ extrusion from the cytosol is sufficiently activated, ie, the Na⁺/Ca²⁺ exchanger of the sarcolemma [7]. The ability of this exchanger to remove Ca²⁺ from the cytosol depends on the magnitude of the transsarcolemmal Na⁺ gradient. Restoration of a sufficiently large Na⁺ gradient across the sarcolemma is therefore the prerequisite for extrusion of Ca²⁺ from reoxygenated myocardial cells. It is essential that the Na⁺ pump of the sarcolemma is rapidly activated to remove access Na⁺ from the interior of the cell. It was shown on the cellular level that the reenergized cardiomyocyte can retain sufficient metabolic competence to rapidly reactivate the SR Ca²⁺ pump and the sarcolemmal Na⁺ pump during the early phase of reoxygenation, even if the cell had been extensively depleted of its energy stores and suffered from severe Ca²⁺ and Na⁺ overload before reenergization [6–9]. It seems that cells in which these pumps have been crucially damaged during the ischemic period are, in principle, unable to recover and cannot be, therefore, subject to reperfusion injury in the sense of the definition given above. The intracellular accumulation of Ca²⁺ is likely to continue in such cells as a diminished Na⁺ gradient favors Ca²⁺ entry through a Na⁺/Ca²⁺ exchanger operating in "reverse mode."

View larger version (23K): [in this window] [in a new window]   Fig 1. Scheme of cation control and initiation of hypercontracture in the reoxygenated cardiomyocyte. On reactivation of oxidative phosphorylation in mitochondria (Mito), the Na+ pump (1) is reactivated generating a transsarcolemmal Na+ gradient which provides driving force for the Na+/Ca2+ exchanger (2) in its "forward mode." Reenergization of the Ca2+ pump (3) of the sarcoplasmic reticulum (SR) causes sequestration of excessive cytosolic Ca2+ into this organelle. Overload of the SR leads to Ca2+ release (4). Repetitive Ca2+ uptake and release by the SR results in Ca2+ cycling between SR and cytosol. Reactivation of oxidative phosphorylation in mitochondria provides energy also to the contractile machinery. Energy supply in presence of high cytosolic Ca2+ concentration causes uncontrolled contractile activation and consecutively mechanical injury of cell structures.

It has recently been demonstrated that hypercontraction may also be elicited by a closely related mechanism [14]. In cells capable of reestablishing normal cation control, the initial phase of Ca²⁺ recovery in the reoxygenated cell may be divided into two stages (i): an early stage during which the cytosolic Ca²⁺ level falls due to uptake of Ca²⁺ into the SR, and (ii) a second stage during which Ca²⁺ is shifted in oscillatory manner between cytosol and SR until a sufficient proportion of the Ca²⁺ level is extruded across the sarcolemma [10]. The Ca²⁺ oscillations of stage (ii) can also cause hypercontraction. This is not solely explained, however, by the magnitude of the Ca²⁺ peak concentrations occurring during oscillations. It has been shown that the susceptibility of reoxygenated cardiomyocytes to develop hypercontracture, at a given elevation of cytosolic Ca²⁺, is increased after a prolonged period of hypoxic energy depletion [15]. This means that hypercontraction in energy depleted and repleted myocardial cells may be elicited by Ca²⁺ concentrations in the cytosol which would not cause harm to a normal cell. The cause for this increased susceptibility seems to reside in an increased fragility of cytoskeletal elements which can no longer resist large contraction forces. An alternative explanation would be that the myofibrillar sensitivity to Ca²⁺ is increased in reoxygenated cardiomyocytes. This has not yet been studied directly. It seems unlikely, however, since studies on reperfused myocardium after short-lived ischemia, exhibiting stunning, have shown rather a reduction of myofibrillar Ca²⁺ sensitivity. In vitro, it is possible to protect the reoxygenated myocardial cell from hypercontracture by damping the oscillatory movements between Ca²⁺ and cytosol, thus reducing the high peak concentrations of cytosolic Ca²⁺ [14]. This can be achieved by specific blockade of Ca²⁺ uptake into or release from the SR, as with cyclopiazonic acid or ryanodine, respectively. Interestingly, the volatile anesthetic halothane can also be used to inhibit SR function and thereby provide protection. Halothane applied upon reoxygenation has been shown to protect isolated cardiomyocytes [14], hypoxia-reoxygenated hearts [16], and ischemic-reperfused in vivo [17] myocardium against hypercontracture and lethal reperfusion injury.

Why is a rapid normalization of extracellular pH harmful in reperfused myocardium?

The cytosolic pH in cardiomyocytes in reperfused myocardium has a pronounced influence on the development of hypercontracture. After prolonged ischemia, the cytosolic pH is markedly lowered because anaerobic metabolism and the breakdown of ATP produce an excess of H⁺. This leads to an acidification of both, the intracellular and the interstitial space. Upon reperfusion, the pH in the interstitial space is rapidly renormalized and a gradient is thus generated between the cytosol, containing still-high H⁺ concentrations, and the interstitium, where the H⁺ concentrations are already renormalized. This causes an activation of the H⁺ extruding mechanisms of the cardiomyocytes, ie, the Na⁺/H⁺ exchanger and the Na⁺/HCO₃^- symporter [18]. This process has two consequences:

(1) Intracellular acidosis is rapidly reduced. Intracellular acidosis inhibits, however, the myofibrillar machinery, ie, it exerts an effect similar to the presence of BDM during the early phase of reperfusion [19]. Rapid extrusion of excess H⁺ from the reoxygenated cell thus removes a potentially protective agent.

(2) Activation of the Na⁺/H⁺ exchanger causes a net influx of Na⁺ into the cytosol. Depending on the ability of the Na⁺ pump to remove this excess load of Na⁺, it may come to a secondary activation of the Na⁺/Ca²⁺ exchange mechanism, transporting Na⁺ in the outward direction and Ca²⁺ in the inward direction. This coupled mechanism may enhance the preexisting Ca²⁺ overload of the cells.

Rapid H⁺ removal and secondary Ca²⁺ uptake thus both favor the development of hypercontracture if ischemic-reperfused myocardial cells are allowed to restore a normal intracellular acid-base balance. It has been demonstrated in vitro that continuation of extracellular acidosis, and thereby intracellular acidosis, during the early phase of reoxygenation protects myocardial cells against the development of hypercontracture during this phase. For reperfusion of myocardium in vivo, the situation is less clear. Inhibitors of the Na⁺/H⁺ exchanger were found to protect against the development of hypercontracture and necrosis during reperfusion only when present during the previous ischemic period. The most likely explanation for the discrepancy between the in vitro and the in vivo studies is, at present, that in blood perfused hearts, intracellular acidosis cannot be maintained for a sufficiently long time after initiation of reperfusion if only the Na⁺/H⁺ exchanger is inhibited. This is because the myocardial cell possesses also another route for the transsarcolemmal extrusion of acid equivalents, ie, the Na⁺/HCO₃^- symporter which works in parallel to the Na⁺/H⁺ exchanger and is active in normal bicarbonate-containing fluids. Unfortunately, specific inhibitors for this mechanism are not yet available for research or therapy.

Why is a rapid normalization of extracellular osmolality harmful in reperfused myocardium?

One of the major causes for water influx into the ischemic-reperfused myocardial cell seems to be cytosolic Na⁺ overload. The Na⁺/H⁺ exchanger plays a major role in cell volume regulation [20]. In ischemic myocardium, the end products of anaerobic metabolism also accumulate, thus increasing the osmotic load in the intracellular and the interstitial space. If, during reperfusion, the extracellular excess of osmotically active molecules is rapidly washed out, an osmotic gradient between the intracellular and the extracellular space is generated. Cellular uptake of water and, through the consecutive increase in intracellular pressure, mechanical stretch of the sarcolemma meets a myocardial cell whose mechanical fragility is increased during the preceding energy depletion. As is the case for hypercontracture, swelling per se is normally not able to disrupt the sarcolemma, as demonstrated by the maintenance of sarcolemmal integrity in isolated cardiomyocytes subjected to osmotic stress in normoxic conditions. However, the mechanical stress caused by swelling may add up with other sources of stress and then result in cell deterioration (Fig 2). In isolated cardiomyocytes, osmotic stress results in sarcolemmal disruption only if the cell develops hypercontracture and has previously been submitted to prolonged energy deprivation [21]. The combination of these factors seems to increase sarcolemmal fragility and render the cell thus more susceptible to damage by osmotic stress. The results of studies with highly hyperosmotic reperfusion indicate that attenuation of the additional mechanical stress imposed by swelling can limit myocardial necrosis during reperfusion [22].

View larger version (21K): [in this window] [in a new window]   Fig 2. Scheme of osmotic injury of the reoxygenated cardiomyocyte. Upon reperfusion, a transsarcolemmal osmotic gradient is created. This leads to water influx and cell swelling. Cytoskeletal fragility increases during ischemia. Circumstances of ischemia and reperfusion augment independently sarcolemmal fragility. Increased cytoskeletal and sarcolemmal fragility and cell swelling together favor rupture of the sarcolemma.

Why can necrosis spread throughout reperfused myocardium?

Several lines of evidence indicate that reoxygenation-induced hypercontracture and sarcolemmal disruption are markedly influenced by cell-to-cell interactions. Histologic observations have shown that the areas of contraction-band necrosis induced by transient coronary occlusion, followed by reperfusion, are composed of hypercontracted myocytes connected to each other to form a continuum, of which the often complex geometry cannot be explained by gradients of flow or microvascular distribution [24]. Computer simulation studies indicate that some kind of cell-to-cell interaction (Fig 3) must be taken into account to explain these histological features, and that in the absence of such interaction, hypercontracted myocytes should be scattered across the area of risk instead of forming continuous zones of necrosis. It has been suggested that this cell-to-cell interaction could be mechanical, the exchange of forces imposed by tight intercellular junctions tearing apart the sarcolemma of myocytes hypercontracting during in situ reperfusion, and damaging the sarcolemma of adjacent cells. But the interaction between adjacent myocytes leading to cell-to-cell progression of hypercontracture could be also chemical. Ca²⁺ and other second messengers may diffuse freely through gap junctions and thereby transmit the trigger for hypercontracture. Recent studies in pairs of isolated cardiomyocytes have demonstrated that hypercontracture of one cell induced by sarcolemmal disruption or microinjection of Ca²⁺ can induce hypercontracture of adjacent cells, that this transmission is associated to passage of gap junction permanent dye to the adjacent cell, and that the gap junction uncoupler heptanol prevent both dye passage and transmission of hypercontracture. The intracoronary administration of heptanol during the first minutes of reperfusion significantly reduces infarct size in the in situ pig heart submitted to transient coronary occlusion [25]. These results are consistent with the hypothesis that cell-to-cell transmission of hypercontracture may contribute to reperfusion injury.

View larger version (22K): [in this window] [in a new window]   Fig 3. Scheme of spreading of necrosis. Once a first cell has developed Ca2+ overload, this can be communicated in a gap junction-dependent way to adjacent cells creating hypercontracture also in these cells, favored by their increased susceptibility to hypercontracture. Exchange of large mechanical force between a hypercontracting cell and its neighbors through the intercalated (interc.) discs can cause their mechanical disruption. Thus, both chemical and physical cell–cell interactions can contribute to spreading of necrosis.

Some interventions applied at the time of reperfusion can apparently reduce the extent of necrotic tissue injury when this is investigated early but, in fact, may only delay the manifestation of necrosis. If this is the case, such an intervention does not provide true reperfusion protection. It is yet another question whether reperfused myocardium may also become subject to apoptosis, ie, programmed cell death, even if effectively protected against immediate necrotic injury. Apoptosis is a transcriptionally controlled cellular response to moderate cell injury or to the influence of various cytokines. In contrast, necrotic cell death is the consequence of severe structural cell damage and is not transcriptionally regulated. Cells which have entered the apoptotic process retain physical integrity of the plasmalemma initially even though its physico-chemical structure may change. The point where the process becomes irreversible seems to be the activation of endonucleosis, severing genomic DNA at internucleosomal sites, that is then taken as a characteristic feature of cell death by apoptosis. In a number of recent articles, evidence for apoptotic cell injury in ischemic-reperfused myocardium and in border zones of ischemic myocardium has been demonstrated. The contribution of apoptosis to cardiomyocyte death during reperfusion has not yet been established in quantitative terms.

In conclusion, after prolonged periods of energy depletion, the ischemic myocardial cell can be jeopardized by specific causes within the reperfusion period (Fig 4). These causes can be viewed as unwanted aspects of the recovery process itself, limiting its efficiency. Understanding of the basic causes has opened novel perspectives for specific interference with these serious pathomechanisms. The experimental results encourage the development of therapeutic approaches to reduce infarct size by specific measures applied during the early phase of reperfusion. The principles of the protective interventions during the early stage of reperfusion are: (1) inhibition of contractile activation; (2) prevention of intracellular Ca²⁺ oscillations; (3) preservation of intracellular acidosis; (4) suppression of causes favoring sarcolemmal fragility; (5) reduction of cell swelling; and (6) prevention of spreading of necrosis. This does not exclude the idea that measures aimed at limiting necrosis or apoptosis occurring later during reperfusion are of additional value.

View larger version (21K): [in this window] [in a new window]   Fig 4. Scheme of factors contributing to immediate lethal (necrotic) reperfusion injury of the cardiomyocyte.

Acknowledgments

This study was supported by the BIOMED II Programme of the European Union, grants PL 95-1254 and PL 95-0838.

References

1. Przyklenk K, ed. Lethal myocardial reperfusion injury [Special issue]. J Thromb Thrombolysis 1997;4(1).
2. Ferrari R., Hearse D.J. Reperfusion injury. J Thromb Thrombolysis 1997;4:25-34.[Medline]
3. Downey J.M., Yellon D.M. Do free radicals contribute to myocardial cell death during ischemia-reperfusion?. In: Yellon C.M., Jennings R.B., eds. Myocardial protection. New York: Raven, 1992:35-57.
4. Hearse D.J., Humphrey S.M., Chain E.B. Abrupt reoxygenation of the anoxic potassium-arrested perfused rat heart. J Mol Cell Cardiol 1973;5:395-407.[Medline]
5. Ganote C.E., Vander Heide R.S. Importance of mechanical factors in ischemic and reperfusion injury. In: Piper H.M., ed. Pathophysiology of severe ischemic myocardial injury. Dordrecht: Kluwer, 1990:337-355.
6. Siegmund B., Zude R., Piper H.M. Recovery of anoxic-reoxygenated cardiomyocytes from severe Ca²⁺ overload. Am J Physiol 1992;263:H1262-H1269.[Abstract/Free Full Text]
7. Siegmund B., Ladilov Y.V., Piper H.M. Importance of Na⁺ for the recovery of Ca²⁺ control in reoxygenated cardiomyocytes. Am J Physiol 1994;267:H506-H513.[Abstract/Free Full Text]
8. Siegmund B., Koop A., Klietz T., et al. Sarcolemmal integrity and metabolic competence of cardiomyocytes under anoxia-reoxygenation. Am J Physiol 1990;258:H285-H291.[Abstract/Free Full Text]
9. Siegmund B., Klietz T., Schwartz P., et al. Temporary contractile blockade prevents hypercontracture in anoxic-reoxygenated cardiomyocytes. Am J Physiol 1991;260:H426-H435.[Abstract/Free Full Text]
10. Schlüter K.D., Schwartz P., Siegmund B., et al. Prevention of the oxygen paradox in hypoxic-reoxygenated hearts. Am J Physiol 1991;261:H416-H432.[Abstract/Free Full Text]
11. García-Dorado D., Théroux P., Duran J.M., et al. Selective inhibition of the contractile apparatus. Circulation 1992;85:1160-1174.[Abstract/Free Full Text]
12. Schlack W., Uebing A., Schäfer M., et al. Regional contractile blockade at the onset of reperfusion reduces infarct size in the dog heart. Pflügers Arch 1994;428:134-141.[Medline]
13. Habazettl H., Palmisano B.W., Bosnjak Z.J., et al. Initial reperfusion with 2,3 butanedione monoxime is better than hyperkalemic reperfusion after cardioplegic arrest in isolated guinea pig hearts. Eur J Cardiothorac Surg 1996;10:897-904.[Abstract]
14. Siegmund B., Schlack W., Piper H.M. Halothane protects cardiomyocytes against reoxygenation-induced hypercontracture. Circulation 1997;96:4372-4379.[Abstract/Free Full Text]
15. Ladilov Y.V., Siegmund B., Piper H.M. Simulated ischemia increases the susceptibility of rat cardiomyocytes to hypercontracture. Circ Res 1997;80:69-75.[Abstract/Free Full Text]
16. Schlack W., Hollmann M., Stunneck J., et al. Effect of halothane on myocardial reoxygenation injury in the isolated rat heart. Br J Anaesth 1996;76:860-867.[Abstract/Free Full Text]
17. Preckel B., Schlack W., Comfère T., et al. Effects of inhalational anaesthetics on myocardial reperfusion injury in vivo. Pflügers Arch 1997;433(Suppl 6):R15.
18. Piper H.M., Balser C., Ladilov Y.V., et al. The role of Na⁺/H⁺ exchange in ischemia-reperfusion. Basic Res Cardiol 1996;91:191-202.[Medline]
19. Ladilov Y.V., Siegmund B., Piper H.M. Protection of the reoxygenated cardiomyocyte against hypercontracture by inhibition of Na⁺/H⁺ exchange. Am J Physiol 1995;268:H1531-H1539.[Abstract/Free Full Text]
20. Inserte J., García-Dorado D., Ruiz-Meana M., et al. The Na⁺-H⁺ exchange occurring during hypoxia in the genesis of reoxygenation-induced myocardial oedema. J Mol Cell Cardiol 1997;29:1167-1175.[Medline]
21. Ruiz-Meana M., García-Dorado D., González M.A., et al. Effect of osmotic stress on sarcolemmal integrity of isolated cardiomyocytes following transient metabolic inhibition. Cardiovasc Res 1995;30:64-69.[Medline]
22. García-Dorado D., Théroux P., Muñoz R., et al. Favorable effects of hyperosmotic reperfusion on myocardial edema and infarct size. Am J Physiol 1992;262:H17-H22.[Abstract/Free Full Text]
23. Schlüter K.D., Jakob G., Ruiz-Meana M., et al. Protection of reoxygenated cardiomyocytes against osmotic fragility by NO donors. Am J Physiol 1996;271:H428-H434.[Abstract/Free Full Text]
24. Solares J., García-Dorado D., Oliveras J., et al. Contraction band necrosis at the lateral borders of the area at risk in reperfused infarcts. Observations in a pig model of in situ coronary occlusion. Virchows Arch 1995;426:393-399.[Medline]
25. García-Dorado D., Inserte J., Ruiz-Meana M., et al. Gap junction uncoupler heptanol prevents cell-to-cell progression of hypercontracture and limits necrosis during myocardial reperfusion. Circulation 1997;96:3579-3586.[Abstract/Free Full Text]

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				M. Castella, G. D. Buckberg, and Z. Tan Blood cardioplegic protection in profoundly damaged hearts: role of Na+-H+ exchange inhibition during pretreatment or during controlled reperfusion supplementation Ann. Thorac. Surg., April 1, 2003; 75(4): 1238 - 1245. [Abstract] [Full Text] [PDF]

				R. M. Mentzer Jr., M. S. Jahania, and R. D. Lasley Myocardial Protection Card. Surg. Adult, January 1, 2003; 2(2003): 413 - 438. [Full Text]

				K. A. Detillieux, F. Sheikh, E. Kardami, and P. A. Cattini Biological activities of fibroblast growth factor-2 in the adult myocardium Cardiovasc Res, January 1, 2003; 57(1): 8 - 19. [Abstract] [Full Text] [PDF]

				P. E. LIGHT, H. D. KANJI, J. E. M. FOX, and R. J. FRENCH Distinct myoprotective roles of cardiac sarcolemmal and mitochondrial KATP channels during metabolic inhibition and recovery FASEB J, December 1, 2001; 15(14): 2586 - 2594. [Abstract] [Full Text] [PDF]

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