Clinical manifestations of myocardial stunning

The Cardiovascular Side Effects of Electroconvulsive Therapy and Their Management

ABSTRACT

Electroconvulsive therapy (ECT) remains stigmatized in the broader medical community because of misunderstandings about treatment procedures, mortality rates, and cardiovascular complications. Electroconvulsive therapy causes periprocedural hemodynamic variability because of the surges in parasympathetic and sympathetic nervous systems after the administration of the electrical charge. Patients experience an increase in cardiac workload, which is potentially dangerous for patients with preexisting heart disease. Several findings suggest that cardiac complications occur most frequently in patients with underlying cardiovascular disease. We describe the cardiovascular complications that may result from ECT treatment and offer insight on how to mitigate these concerns if they occur. PubMed was queried using terms "electroconvulsive therapy" and "cardiovascular adverse effects." A table is provided with the common cardiovascular side effects of ECT and the most recent evidence-based treatment strategies to manage them. Generally, ECT is a safe procedure in which complications are minor and manageable. Most major complications caused by ECT are related to the cardiovascular system; however, with an appropriate pre-ECT evaluation and a comprehensive multidisciplinary team approach, the cardiovascular complications can be well managed and minimized. Providing proper cardiac clearance can prevent cardiac complications and provide timely care to treatment-resistant populations who are at risk for excessive morbidity and suicide.

S-allylcysteine improves ischemia/reperfusion alteration on cardiac function, antioxidant, and mitochondrial permeability

S-Allylcysteine (SAC) is an extensively studied natural product which has been proven to confer cardioprotection. This potentiates SAC into many clinical relevance possibilities, hence, the use of it ought to be optimally elucidated. To further confirm this, an ischemia/reperfusion model has been used to determine SAC at 10 mM and 50 mM on cardiac function, cardiac marker, and mitochondrial permeability. Using Langendorff setup, 24 adult male Wistar rats' hearts were isolated to be perfused with Kreb-Henseleit buffer throughout the ischemia/reperfusion method. After 20 min of stabilization, global ischemia was induced by turning off the perfusion for 35 min followed by 60 min of reperfusion with either Kreb-Henseleit buffer or SAC with the dose of 10 mM or 50 mM. The cardiac function was assessed and coronary effluent was collected at different timepoints throughout the experiment for lactate dehydrogenase (LDH) measurement. The harvested hearts were then used to measure glutathione while isolated mitochondria for mPTP analysis. SAC-reperfused hearts were shown to prevent the aggravation of cardiac function after I/R induction. It also dose-dependently upregulated glutathione reductase and glutathione level and these were also accompanied by significant reduction of LDH leakage and preserved mitochondrial permeability. Altogether, SAC dose-dependently was able to recover the post-ischemic cardiac function deterioration alongside with improvement of glutathione metabolism and mitochondrial preservation. These findings highly suggest that SAC when sufficiently supplied to the heart would be able to prevent the deleterious complications after the ischemic insult.

Sustained nicorandil administration reduces the infarct size in ST-segment elevation myocardial infarction patients with primary percutaneous coronary intervention

Objective:

Currently, there is still no effective strategy to diminish the infarct size (IS) in patients with ST-segment elevation myocardial infarction (STEMI). According to a previous animal study, nicorandil treatment is a promising pharmaceutical treatment to limit the infarct area. In this study, we aim to investigate the effects of continual nicorandil administration on the IS and the clinical outcomes in patients with STEMI who underwent primary percutaneous coronary intervention (pPCI).

Methods:

One hundred seventeen patients with STEMI and undergoing pPCI were randomly divided into the sustained nicorandil group (5 mg, three times daily) or the control group (only single nicorandil before PCI). The primary endpoint was the IS, evaluated by single-photon emission computed tomography (SPECT) 3 months after pPCI.

Results:

Eighty-five patients completed the IS assessment via SPECT, and 99 participants were available for follow-up after 6 months. Finally, there was a statistical difference in the IS between the nicorandil and control groups {13% [interquartile range (IQR), 8–17] versus 16% [IQR, 12–20.3], p=0.027}. Additionally, we observed that maintained nicorandil administration significantly improved the left ventricular ejection fraction at 3 months and enhanced the activity tolerance (physical limitation and angina stability) at 6 months after PCI.

Conclusion:

Sustained nicorandil treatment reduced the IS and improved the clinical outcomes compared to the single nicorandil administration for patients with STEMI undergoing the pPCI procedure. Continuous cardioprotective therapy may be more beneficial for patients with STEMI.

Targeting phosphodiesterase 5 as a therapeutic option against myocardial ischaemia/reperfusion injury and for treating heart failure

Phosphodiesterase type 5 (PDE5) selectively hydrolyses the second messenger cGMP into 5'-GMP, thereby regulating its intracellular concentrations. Dysregulation of the cGMP-dependent pathway plays a significant role in various cardiovascular diseases. Therefore, its modulation by drugs, such as PDE5 inhibitors, may represent an effective therapeutic approach. There are currently four PDE5 inhibitors available for the treatment of erectile dysfunction: sildenafil, vardenafil, tadalafil and avanafil. Sildenafil and tadalafil have also received Food and Drug Administration approval for the treatment of pulmonary arterial hypertension. This review summarizes the pharmacological aspects and clinical potential of PDE5 inhibition for the treatment of myocardial ischaemia/reperfusion injury and heart failure.

LINKED ARTICLES

This article is part of a themed section on Inventing New Therapies Without Reinventing the Wheel: The Power of Drug Repurposing. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.2/issuetoc.

Hyperkalemic cardioplegia for adult and pediatric surgery: end of an era?

Despite surgical proficiency and innovation driving low mortality rates in cardiac surgery, the disease severity, comorbidity rate, and operative procedural difficulty have increased. Today's cardiac surgery patient is older, has a "sicker" heart and often presents with multiple comorbidities; a scenario that was relatively rare 20 years ago. The global challenge has been to find new ways to make surgery safer for the patient and more predictable for the surgeon. A confounding factor that may influence clinical outcome is high K(+) cardioplegia. For over 40 years, potassium depolarization has been linked to transmembrane ionic imbalances, arrhythmias and conduction disturbances, vasoconstriction, coronary spasm, contractile stunning, and low output syndrome. Other than inducing rapid electrochemical arrest, high K(+) cardioplegia offers little or no inherent protection to adult or pediatric patients. This review provides a brief history of high K(+) cardioplegia, five areas of increasing concern with prolonged membrane K(+) depolarization, and the basic science and clinical data underpinning a new normokalemic, "polarizing" cardioplegia comprising adenosine and lidocaine (AL) with magnesium (Mg(2+)) (ALM™). We argue that improved cardioprotection, better outcomes, faster recoveries and lower healthcare costs are achievable and, despite the early predictions from the stent industry and cardiology, the "cath lab" may not be the place where the new wave of high-risk morbid patients are best served.

Toll-like receptor and its roles in myocardial ischemic/reperfusion injury

The innate immune system, mediated via toll-like receptors (TLRs), represents the first line of defensive mechanisms that protects hosts from invading microbial pathogens. TLRs are a family of pattern recognition receptors (PRRs), and are pathologically activated by a set of pathogen-associated microbial patterns (PAMPs) and damage-associated molecular patterns (DAMPs). TLRs deliver signals via a specific intracellular signaling pathway involving distinctive adaptor proteins and protein kinases, and ultimately initiate transcriptional factors resulting in inflammatory responses. TLR4 is a paramount type of TLRs, located in the heart, and plays an important role in mediating myocardial ischemic reperfusion (I/R) injury. Loss-of-function experiments and animal models using genetic techniques have found that the MyD88-independent and the MyD88-dependent pathways together participate in the pathological process of myocardial I/R injury. Some other distinctive signaling pathways, such as the PI3K/AKt and AMPK/ERK pathways, interacting with the TLR4 signaling pathway, were also found to be causes of myocardial I/R injury. These different pathways activate a series of downstream transcriptional factors, produced a great quantity of inflammatory cytokines, such as IL, TNF, and initiate inflammatory response. This results in cardiac injury and dysfunction, such as myocardial stunning, no reflow phenomenon, reperfusion arrhythmias and lethal reperfusion injury, and other related complication such as ventricular remodeling. In the future, blockades aimed at blocking the signaling pathway could benefit developments in pharmacology.

Is hyperglycemia bad for the heart during acute ischemia?

OBJECTIVE

This study investigates the impact of diabetes on myocardium in the setting of acute ischemia-reperfusion in a porcine model.

METHODS

In normoglycemic (ND group) and alloxan-induced diabetic (DM group) male Yucatan pigs, the left anterior descending coronary artery territory was made ischemic and then reperfused. Hemodynamic values and myocardial function were measured. Monastryl blue and triphenyl tetrazolium chloride staining were used to assess size of the areas at risk and infarction. Glycogen content was assessed using periodic acid-Schiff staining. Cell death and survival signaling pathways were assessed by immunoblotting.

RESULTS

Mean arterial pressure and developed left ventricular pressure were lower in the DM group (P < .05). Whereas global left ventricular function was worse in the DM group (P < .05), regional function in the area at risk was improved on the horizontal axis (P < .05). Mean infarct size was smaller in the DM versus the ND group (19% vs 43%; P < .05), whereas the area at risk was similar in both groups (34% vs 36%; P = .7). Ischemic myocardium in the DM group displayed more prominent staining for glycogen compared with the ND group. In the area at risk, expression of cell survival proteins including phosphorylated endothelial nitric oxide synthase (0.17 ± 0.04 vs 0.04 ± 0.01; P < .05), heat shock protein 27 (0.7 ± 0.2 vs 0.3 ± 0.1; P < .05), nuclear factor-κB (0.14 ± 0.02 vs 0.03 ± 0.01; P < .05), and mammalian target of rapamycin (0.35 ± 0.05 vs 0.15 ± 0.02; P < .05) were higher in DM animals, whereas in nonischemic tissue, expression of these proteins was similar or lower in the DM group.

CONCLUSIONS

Although type I diabetes worsens global left ventricular function, it is protective in the ischemic area, leading to increased expression of cell survival proteins and decreased infarct size.

Hibernating myocardium: pathophysiology, diagnosis, and treatment

Comprehensive management of patients with chronic ischemic disease is a critically important component of clinical practice. Cardiac myocytes have the potential to adapt to limited flow conditions by adjusting contractile function, reducing metabolism, conserving resources, and preserving myocardial integrity to cope with an oxygen and (or) nutrition shortage. A prime metabolic feature of cardiac myocytes affected by chronic ischemia is the return to a fetal gene pattern with predominance of carbohydrates as the substrate for energy. Structural adaptation with multiple intracellular changes is part of the remodeling process in hibernating myocardium. Transmural heterogeneity, which defines the pattern of injury in ventricular cardiomyocytes and the response to chronic ischemia, is a multifactorial process originating from functional, metabolic, and flow differences in subendocardial and subepicardial regions. Autophagy is typically activated in hibernating myocardium and has been identified as a prosurvival mechanism. Chronic ischemia is associated with changes in the number, size, and distribution of gap junctions and may give rise to conduction disturbances and arrhythmogenesis. Differentiation between viable and nonviable myocardium by assessing sensitivity of inotropic reserve is a crucial diagnostic tool that is correlated with the prognosis and outcome for improved contractility after restoration of blood perfusion in afflicted myocardium.Reliable and accurate diagnosis of ischemic, scar, and viable tissues is critical for recover strategies. Although early surgical reinstitution of blood flow is most effective in restoring physiologic function of the hibernating myocardium, several new approaches offer promising alternatives. Among others, vascular endothelial growth factor and fibroblast growth factor-2 (FGF-2), especially its lo-FGF-2 isoform, have been shown to be effective in rapid neovascularization. Substances such as statins, resveratrol, some hormones, and omega-3 fatty acids can improve recovery effect in chronically underperfused hearts. For patients with drug-refractory ischemia, intramyocardial transplantation of stem cells into predefined areas of the heart can enhance vascularization and have beneficial effects on cardiac function. This review of ischemic injury, its heterogeneity, accurate diagnosis, and newer methods of treatment, shows there is much information and tremendous hope for better management of patients with coronary heart disease.

Hydrogen sulfide therapy attenuates the inflammatory response in a porcine model of myocardial ischemia/reperfusion injury

INTRODUCTION

Hydrogen sulfide is produced endogenously in response to myocardial ischemia and thought to be cardioprotective. The mechanism underlying this protection has yet to be fully elucidated, but it may be related to sulfide's ability to limit inflammation. This study investigates the cardioprotection provided by exogenous hydrogen sulfide and its potential anti-inflammatory mechanism of action.

METHODS

The mid left anterior descending coronary artery in 14 Yorkshire swine was acutely occluded for 60 minutes, followed by reperfusion for 120 minutes. Controls (n = 7) received placebo, and treatment animals (n = 7) received sulfide 10 minutes before and throughout reperfusion. Hemodynamic and functional measurements were obtained. Evans blue and triphenyl tetrazolium chloride staining identified the area at risk and infarction. Coronary microvascular reactivity was assessed. Tissue was assayed for myeloperoxidase activity and proinflammatory cytokines.

RESULTS

Pre-ischemia/reperfusion hemodynamics were similar between groups, whereas post-ischemia/reperfusion mean arterial pressure was reduced by 28.7 +/- 5.0 mm Hg in controls versus 6.7 +/- 6.2 mm Hg in treatment animals (P = .03). Positive first derivative of left ventricular pressure over time was reduced by 1325 +/- 455 mm Hg/s in controls versys 416 +/- 207 mm Hg/s in treatment animals (P = .002). Segmental shortening in the area at risk was better in treatment animals. Infarct size (percent of area at risk) in controls was 41.0% +/- 7.8% versus 21.2% +/- 2.5% in the treated group (P = .036). Tissue levels of interleukin 6, interleukin 8, tumor necrosis factor-alpha, and myeloperoxidase activity decreased in the treatment group. Treated animals demonstrated improved microvascular reactivity.

CONCLUSIONS

Therapeutic sulfide provides protection in response to ischemia/reperfusion injury, improving myocardial function, reducing infarct size, and improving coronary microvascular reactivity, potentially through its anti-inflammatory properties. Exogenous sulfide may have therapeutic utility in clinical settings in which ischemia/reperfusion injury is encountered.

Myocardial stunning after electroconvulsive therapy in patients with an apparently normal heart

Myocardial stunning refers to contractile dysfunction that persists after an ischemic episode and restoration of coronary blood flow. In this article, 2 cases of myocardial stunning after electroconvulsive therapy in patients with an apparently normal heart are presented. The incidence of this condition is unknown. It is observed that this condition seems to occur in females and in the obese and is generally associated with rapid recovery. This occurrence seems to be brought about by autonomic changes that occur during electroconvulsive therapy. Several drugs have been used to ameliorate the condition, although studies were limited to establish efficacy of regimens.

Possible mechanism of rottlerin induced modulation of ischemia reperfusion injury in isolated rat hearts

The present study was designed to investigate the modulatory effects of rottlerin on ischemia reperfusion induced myocardial injury. Isolated rat hearts were exposed to 30 min of global ischemia followed by 120 min of reperfusion using Langendorff apparatus. Myocardial injury was assessed in the terms of infarct size, release of lactate dehydrogenase (LDH), creatine kinase (CK) enzymes. Rottlerin, a selective PKCdelta inhibitor, did not modulate ischemia-reperfusion (I/R) induced myocardial injury at low dose (3 microM). However, at moderate dose (6 microM) it significantly produced cardioprotective effects. On the contrary, rottlerin at high dose (12 microM) significantly enhanced I/R induced myocardial injury. However, administration of FR-167653 (1.1 microM, 2.2 microM), a selective p-38 mitogen activated protein kinase (p-38 MAPK) inhibitor, attenuated rottlerin (12 microM) mediated enhancement in I/R induced myocardial injury in a dose dependent manner. Per se administration of FR-167653 (1.1 microM, 2.2 microM) also attenuated I/R induced myocardial injury in a dose dependent manner. Pretreatment with rottlerin (6 microM) did not enhance the cardioprotective effects of FR-167653 (2.2 microM). It may be concluded that rottlerin mediated cardioprotective effects at moderate dose, possible due to inhibition of PKCdelta; while at high dose it enhanced I/R induced myocardial injury which may be attributed to activation of p-38 MAPK.

Cardioprotection in stunned and hibernating myocardium

Although myocardial ischemia was once thought to result in irreversible cellular damage, it is now demonstrated that in cardiac tissue, submitted to the stress of oxygen and substrate deprivation, endogenous mechanisms of cell survival may be activated. These molecular mechanisms result in physiological conditions of adaptation to ischemia, known as myocardial stunning and hibernation. These conditions result from a switch in gene and protein expression, which sustains cardiac cell survival in a context of oxygen deprivation and during the stress of reperfusion. The pattern of cell survival elicited by ischemia in myocardial stunning or hibernation results in the activation of cytoprotective mechanisms that will protect the heart against further ischemic damage, a condition referred to as ischemic preconditioning. The basic mechanisms underlying stunning and hibernation are still a matter of intense research, which includes the discovery and characterization of novel survival genes not described in the heart before, or the unraveling of new cellular processes, such as autophagy. Understanding how the molecular adaptation of the cardiac myocyte during stress sustains its survival in these conditions therefore might help defining novel mechanisms of endogenous myocardial salvage, in order to expand the conditions of maintained cellular viability and functional salvage of the ischemic myocardium.

Ischemia in women with angina and normal coronary angiograms

BACKGROUND

Coronary artery disease is frequent in postmenopausal women. Myocardial ischemia has been induced with stress testing, and a relationship between endothelial dysfunction and perfusion defects has been reported.

OBJECTIVE

To evaluate whether myocardial ischemia can be evidenced both by perfusion and function abnormalities using gated single-photon emission computed-tomography myocardial scintigraphy with technetium-labeled compounds in women with typical angina, normal coronary angiography, and endothelial dysfunction.

METHODS AND RESULTS

Fifty-nine postmenopausal patients were studied. Each underwent technetium-99m methoxy-isobutyl-isonitrile myocardial scintigraphy (protocol: exercise stress-rest), brachial artery endothelial function measured by ultrasonography, lipidogram, and 24-h ambulatory ECG recording (Holter). Twenty-one patients (group I) showed perfusion defects in myocardial scintigraphy, whereas the other 38 patients (group II) did not. Group I patients exhibited endothelial dysfunction more frequently (57 vs. 29%) than those of group II. Among group I patients, 12 showed a reversible perfusion defect that, in 75% of the cases, was associated with poststress left ventricular ejection fraction reduction greater than 5% and a regional hypokinesis. Nine patients had fixed defects, which in 56% of the cases were associated with poststress left ventricular ejection fraction reduction greater than 5%. Left ventricular ejection fraction poststress minus left ventricular ejection fraction at rest was -5.2% in group I patients versus -1.8% in group II (P<0.001). Three patients in group I showed evidence of ischemia by Holter compared with four in group II.

CONCLUSION

Stress-induced ischemia is associated with poststress left ventricular ejection fraction reduction in postmenopausal women with typical angina, normal coronary angiography, and a trend toward abnormal endothelial-mediated vasodilation.

Mechanisms leading to reversible mechanical dysfunction in severe CAD: alternatives to myocardial stunning

Patients with severe chronic coronary artery disease (CAD) exhibit a highly altered myocardial pattern of perfusion, metabolism, and mechanical performance. In this context, the diagnosis of stunning remains elusive not only because of methodological and logistic considerations, but also because of the pathophysiological characteristics of the myocardium of these patients. In addition, a number of alternative pathophysiological mechanisms may act by mimicking the functional manifestations usually attributed to stunning. The present review describes three mechanisms that could theoretically lead to reversible mechanical dysfunction in these patients: myocardial wall stress, the tethering effect, and myocardial expression and release of auto- and paracrine agents. Attention is focused on the role of these mechanisms in scintigraphically “normal” regions (i.e., regions usually showing normal perfusion, glucose metabolism, and cellular integrity as assessed by nuclear imaging techniques), in which stunning is usually considered, but these mechanisms could also operate throughout the viable myocardium. We hypothesize that reversion of these three mechanisms could partially explain the unexpected functional benefit after reperfusion recently highlighted by high-spatial-resolution imaging techniques.

Myocardial ischemia/reperfusion-injury, a clinical view on a complex pathophysiological process

Myocardial infarction is the major cause of death in the world. Over the last two decades, coronary reperfusion therapy has become established for the management of acute myocardial infarction (AMI). However, restoration of blood flow to previously ischemic myocardium results in the so-called ischemia/reperfusion (IR)-injury. The different clinical manifestations of this injury include myocardial necrosis, arrhythmia, myocardial stunning and endothelial- and microvascular dysfunction including the no-reflow phenomenon. The pathogenesis of ischemia/reperfusion injury consists of many mechanisms. Recently, there's increasing evidence for an important role in IR-injury on hypercontracture induced by high levels of cytosolic calcium or by low concentrations of ATP. In the last years, many studies on experimental models were investigated, but the clinical trials confirming these effects remain spare. Recently, the beneficial effect of Na(+)/H(+)-exchange inhibitor cariporide and of the oxygen-derived free radical (ODFR) scavenger vitamin E on coronary bypass surgery-induced IR-injury were demonstrated. Also recently, the beneficial effect of allopurinol on the recovery of left ventricular function after rescue balloon-dilatation was demonstrated. The beneficial effect of magnesium and trimetazidine on IR-injury remains controversial. The beneficial effect of adenosine remains to be further confirmed. There's also increasing interest in agentia combining the property of upregulating NO-synthase (e.g. L-arginine) and restoring the balance between NO and free radicals (e.g. tetrahydrobiopterin). One of such agents could be folic acid. In this review article the authors give an overview of the recent insights concerning pathogenesis and therapeutic possibilities to prevent IR-induced injury.

Global ischemic duration and reperfusion function in the isolated perfused rat heart

Post-ischemic myocardial dysfunction has been observed in a variety of clinical situations including cardiac arrest. Potentially survivable cardiac arrest following short-term global myocardial ischemia may be of insufficient duration to cause irreversible myocyte injury, but still results in contractile and bioenergetic dysfunction. The purpose of this study was to characterize the ischemic transition from reversible to irreversible injury in the isolated perfused rat heart. Isolated, buffer perfused, male Sprague-Dawley rat hearts underwent normothermic ischemia of 15, 20, 25 or 30 min with or without 30 min of reperfusion and were freeze clamped in liquid nitrogen for bioenergetic analysis of LV tissue. Post-ischemic LV function and measurements of bioenergetic recovery were made between groups and with non-ischemic controls. Baseline LV function was similar in all groups. Post-ischemic contractile function was markedly depressed in the 25 and 30 min ischemia groups with persistent depression of high-energy phosphates, total adenine nucleotide pool, myocardial oxygen consumption, elevated CK release and evidence of significant mitochondrial edema in the 30 min group. In contrast with longer ischemic periods, the reduction in LV contractile function after 15 and 20 min of ischemia was mild, with more complete bioenergetic recovery, minimal CK release, and normal appearing mitochondrial. This data suggests a period of transition from reversible to irreversible injury occurring at approximately 20 min of normothermic global ischemia in the isolated perfused rat heart.

Dobutamine responsiveness, PET mismatch, and lack of necrosis in low-flow ischemia: is this hibernation in the isolated rat heart?

The clinical hallmarks of hibernating myocardium include hypocontractility while retaining an inotropic reserve (using dobutamine echocardiography), having normal or increased [18F]fluoro-2-deoxyglucose-6-phosphate (18FDG6P) accumulation associated with decreased coronary flow [flow-metabolism mismatch by positron emission tomography (PET)], and recovering completely postrevascularization. In this study, we investigated an isolated rat heart model of hibernation using experimental equivalents of these clinical techniques. Rat hearts (n = 5 hearts/group) were perfused with Krebs-Henseleit buffer for 40 min at 100% flow and 3 h at 10% flow and reperfused at 100% flow for 30 min (paced at 300 beats/min throughout). Left ventricular developed pressure fell to 30 +/- 8% during 10% flow and recovered to 90 +/- 7% after reperfusion. In an additional group, this recovery of function was found to be preserved over 2 h of reperfusion. Electron microscopic examination of hearts fixed at the end of the hibernation period demonstrated a lack of ischemic injury and an accumulation of glycogen granules, a phenomenon observed clinically. In a further group, hearts were challenged with dobutamine during the low-flow period. Hearts demonstrated an inotropic reserve at the expense of increased lactate leakage, with no appreciable creatine kinase release. PET studies used the same basic protocol in both dual- and globally perfused hearts (with 250MBq 18FDG in Krebs buffer +/- 0.4 mmol/l oleate). PET data showed flow-metabolism "mismatch;" whether regional or global, 18FDG6P accumulation in ischemic tissue was the same as (glucose only) or significantly higher than (glucose + oleate) control tissue (0.023 +/- 0.002 vs. 0.011 +/- 0.002 normalized counts. s-1x g-1x min-1, P < 0.05) despite receiving 10% of the flow. This isolated rat heart model of acute hibernation exhibits many of the same characteristics demonstrated clinically in hibernating myocardium.

Hibernation, Stunning, and Preconditioning: Historical Perspective, Current Concepts, Clinical Applications, and Future Implications

Despite considerable advances, coronary artery disease is the leading cause of morbidity and mortality in the Western world. The development of effective therapeutic strategies for protecting the myocardium from ischemia would have major impact on patients with coronary artery disease. It is now accepted that patients with coronary artery disease can experience prolonged regional ischemic dysfunction that does not necessarily arise from irreversible tissue damage, and to some extent, can be reversed by restoration of blood flow. The initial stages of dysfunction are probably caused by chronic stunning that can be reversed after revascularization, resulting in rapid and complete functional recovery. On the other hand, the more advanced stages of dysfunction likely correspond to chronic hibernation. After revascularization, functional recovery will probably be quite delayed and mostly incomplete. Over the past decade, the possibility that an innate mechanism of myocardial protection might be inducible in the human heart has generated considerable excitement. In the last two decades, there was phenomenal growth in the understanding of the mechanism known as ischemic preconditioning that is responsible for the innate myocardial protection. Continued research and progress in this area may soon lead to the availability of preconditioning-mimetic treatments. The current concepts, mechanisms, and potential clinical applications of myocardial hibernation, stunning, and ischemic preconditioning are reviewed.