Previous angina alters in-hospital outcome in TIMI 4. A clinical correlate to preconditioning?

Drugs mediating myocardial protection

The occurrence of myocardial ischaemia will result in either reversible or irreversible myocardial dysfunction. Even when revascularization is successful, some reperfusion injury may occur that transiently impairs myocardial function. Therefore, treatment should not only be directed towards prompt restoration of myocardial blood flow but measures should also be taken to prevent or alleviate the consequences of myocardial reperfusion injury. Over the years, various strategies have been developed. The present contribution reviews a number of these strategies focusing on pharmacological treatments that have been developed to address myocardial reperfusion injury.

Remote ischemic preconditioning for renal and cardiac protection during endovascular aneurysm repair: a randomized controlled trial

PURPOSE

To report a randomized clinical trial designed to determine if remote ischemic preconditioning (IP) has the ability to reduce renal and cardiac damage following endovascular aneurysm repair (EVAR).

METHODS

Forty patients (all men; mean age 76+/-7 years) with abdominal aortic aneurysms averaging 6.3+/-0.8 cm in diameter were enrolled in the trial from November 2006 to January 2008. Eighteen patients (mean age 74 years, range 72-81) were randomized to preconditioning and completed the full remote IP protocol; there were no withdrawals. Twenty-two patients (mean age 76 years, range 66-80) were assigned to the control group. Remote IP was induced using sequential lower limb ischemia. Serum and urinary markers of renal and cardiac injury were compared between the groups.

RESULTS

Urinary retinol binding protein (RBP) levels increased 10-fold from a median of 235 micromol/L to 2356 micromol/L at 24 hours (p = 0.0001). There was a lower increase in the preconditioned group, from 167 micromol/L to 413 micromol/L at 24 hours (p = 0.04). The median urinary albumin:creatinine ratio was significantly lower in the preconditioned group at 24 hours (5 versus 8.8, p = 0.06). There were no differences in the rates of renal impairment or major adverse cardiac events.

CONCLUSION

Remote preconditioning reduces urinary biomarkers of renal injury in patients undergoing elective EVAR. This small pilot trial was unable to detect an effect on clinical endpoints; further trials are warranted.

Stress test with dual isotope studies for the documentation of classical ischemic preconditioning

OBJECTIVES

We investigated whether myocardial perfusion imaging (MPI) can demonstrate the effect of classical preconditioning.

METHODS

21 patients with documented coronary artery disease (stenosis>or=70%) underwent two exercise stress tests (EST) with concomitant MPI, using TL-201 for the first and tetrofosmin-Tc-99m for the second. A third MPI was performed at rest, using Tc-99m. Total defect score was derived by summing tracer uptake in a 17 segments left ventricle model, graded on a 5-point scale. Tomographic images were also analyzed quantitatively, to derive the total defect size.

RESULTS

Maximum ST depression did not differ significantly between the two EST (2.2+/-1 vs 2.2+/-1 mm, p=NS), however in the second EST longer times for onset of ischemic changes (228+/-94 vs 265+/-103 s, p=0.01) and appearance of angina (282+/-153 vs 328+/-177 s, p=0.04) were observed. Exercise perfusion abnormalities were significantly lower in the second MPI, in terms of both total defect score (19.2+/-11.5 vs 10+/-10.4, p<0.0001) and total defect size (28.3+/-16.9 vs 13.8+/-15.8, p<0.0001).

CONCLUSION

Significant improvement in perfusion pattern was demonstrated in the second MPI, accompanied by delayed appearance of ischemic manifestations. The improvement in myocardial perfusion extends far beyond the changes that can be attributed to differences in myocardial uptake between tracers, reflecting the effect of classical preconditioning.

High incidence of TIMI flow 0 to I in patients with ST-elevation myocardial infarction without electrocardiographic lytic criteria

BACKGROUND

Most patients with ST-elevation myocardial infarction fulfilling ST-segment elevation (STE) lytic criteria present an occluded culprit artery but the occlusion rate in those with minimal STE (minSTE) not fulfilling lytic criteria is unknown.

METHODS

In 63 patients with minSTE (mean STE:1.2 +/- 0.6 mm) and 149 with lytic STE criteria (lyticSTE, 4.8 +/- 3.1 mm), an emergency coronary angiography was performed, serial creatine kinase-MB was determined, and ejection fraction was measured by 2-dimensional echocardiography.

RESULTS

The 2 groups showed similar time from pain onset to electrocardiogram (minSTE 196 +/- 199 vs lyticSTE, 176 +/- 172 min, P = .444), and although time to catheterization was longer in patients with minSTE (426 +/- 314 vs 253 +/- 239 min, P < .001), the rate of TIMI flow 0 to I (88% vs 81%, P = .21) was similar and percutaneous coronary intervention was performed in >80% of patients from the 2 groups. Moreover, patients with minSTE had higher rate of collateral circulation (27% vs 13%, P = .013), lower rate of Q waves (44% vs 60%, P = .041), lower creatine kinase-MB (202 +/- 150 vs 335 +/- 280, microg/L, P < .001), higher ejection fraction (54% +/- 9% vs 49% +/- 12%, P = .004), and lower mortality (0% vs 7.4%, P = .036).

CONCLUSIONS

ST-elevation myocardial infarction patients with minSTE present a high prevalence of TIMI flow 0 to I similar to those meeting lyticSTE suggesting an identical underlying mechanism and the potential to benefit from primary angioplasty.

Chronic nitrate therapy is associated with different presentation and evolution of acute coronary syndromes: insights from 52,693 patients in the Global Registry of Acute Coronary Events

AIMS

Brief episode(s) of ischaemia may increase cardiac tolerance to a subsequent major ischaemic insult ('preconditioning'). Nitrates can pharmacologically mimic ischaemic preconditioning in animals. In this study, we investigated whether antecedent nitrate therapy affords protection toward acute ischaemic events using data from the Global Registry of Acute Coronary Events.

METHODS AND RESULTS

The dataset comprised 52,693 patients from 123 centres in 14 countries: 42,138 (80%) were nitrate-naïve and 10,555 (20%) were on chronic nitrates at admission. In nitrate-naïve patients, admission diagnosis was ST-segment elevation myocardial infarction (STEMI) in 41%, whereas 59% presented with non-ST-segment elevation acute coronary syndrome (NSTE-ACS). In contrast, only 18% nitrate users showed STEMI, whereas 82% presented with NSTE-ACS. Thus, among nitrate users clinical presentation was tilted toward NSTE-ACS by more than four-fold, STEMI occurring in less than one of five patients (P < 0.0001). After adjustment (age, sex, medical history, prior therapy, revascularization, previous angina), chronic nitrate use remained independent predictor of NSTE-ACS (OR 1.36; 95% CI 1.26-1.46; P < 0.0001). Furthermore, regardless of presentation, within both STEMI and NSTEMI populations, antecedent nitrate use was associated with significantly lower levels of CK-MB and troponin (P < 0.0001 for all).

CONCLUSION

In this large multinational registry, chronic nitrate use was associated with a shift away from STEMI in favour of NSTE-ACS and with less release of markers of cardiac necrosis. These findings suggest that in nitrate users acute coronary events may develop to a smaller extent. Randomized, placebo-controlled trials are warranted to establish whether nitrate therapy may pharmacologically precondition the heart toward ischaemic episodes.

Ischemic preconditioning and heat shock activate Akt via a focal adhesion kinase-mediated pathway in Langendorff-perfused adult rat hearts

Heat stress (HS)-induced cardioprotection is associated with the activation of focal adhesion kinase (FAK) and protein kinase B (Akt) in neonatal rat ventricular myocytes (NRVMs), suggesting that stress-induced activation of survival pathways may be important in protecting intact hearts from irreversible injury. The purposes of this study were 1) to examine the subcellular signaling pathways activated by HS and ischemic preconditioning (IP) in intact hearts, 2) to determine whether HS and IP activate an integrated survival pathway similar to that activated by HS in cultured NRVMs, and 3) to determine whether HS and IP reduce lethal cell injury in perfused intact hearts. Adult rat hearts perfused in the Langendorff mode were subjected to 25 min of global ischemia and 30 min of reperfusion (I/R) either 24 h after whole animal HS or following a standard IP protocol. Myocardial signaling was analyzed using Western blot analysis, whereas cell death was assayed by measuring lactate dehydrogenase release into the perfusate and confirmed by light microscopy. Similar to NRVMs, HS performed in the whole animal 24 h before I/R increased phosphorylation of FAK at tyrosine-397 and protein kinase B (Akt) and resulted in protection from cell death. Using IP as a myocardial stress also resulted in an increased phosphorylation/activation of both FAK and Akt and resulted in reduced cell death in adult perfused rat hearts subjected to I/R. In conclusion, 1) myocardial stress caused by whole animal HS activates cytoskeletal-based survival signaling pathways in whole heart tissue and reduces lethal I/R injury and 2) IP activates the same stress-induced survival pathway and the activation correlates with the well-known cardioprotective effect of IP on lethal I/R injury.

Clinical application of ischemic preconditioning in the elderly

A mild stress such as brief ischemic episodes may protect the heart from a successive and more prolonged myocardial ischemia (ischemic preconditioning). This phenomenon is considered a typical "hormetic mechanism" by which the heart is immunized from pathological insults such as myocardial ischemia. This mechanism is reduced with aging and it may be restored and/or preserved by drugs such as adenosine or nicorandil, a mitochondrial K(ATP) channels, and lifestyle interventions such as physical activity and/or hypocaloric diet. Moreover, since the mechanisms involved in cardiac ischemic preconditioning have been established basic and clinical investigators are encouraged to test several drug in well-controlled animal and human studies in order to prevent and/or restore the age-related reduction of ischemic preconditioning.

Prenatal cocaine exposure abolished ischemic preconditioning-induced protection in adult male rat hearts: role of PKCepsilon

Prenatal cocaine exposure in rats resulted in decreased PKCepsilon protein expression in the heart of adult male but not female offspring. The present study determined its functional consequence of inhibiting cardioprotection mediated by ischemic preconditioning. Pregnant Sprague-Dawley rats were administered intraperitoneally saline or cocaine (30 mg.kg(-1).day(-1)) from day 15 to day 21 of gestational age. Hearts were isolated from 3-mo-old offspring and were subjected to ischemia and reperfusion injury in a Langendorff preparation, with or without prior ischemic preconditioning. Preischemic values of left ventricular function were the same between the saline control and cocaine-treated animals. Ischemic preconditioning of two episodes of 5-min ischemia significantly decreased infarct size and enhanced postischemic functional recovery of the left ventricle in the saline control animals. This ischemic preconditioning was associated with increased phospho-PKCepsilon, but not phospho-PKCdelta, levels and was blocked by a PKCepsilon translocation inhibitor peptide. Prenatal cocaine treatment abolished the ischemic preconditioning-mediated increase in phospho-PKCepsilon and cardioprotection in the heart of male offspring. In contrast, the cardioprotective effect was fully maintained in female offspring that were exposed to cocaine before birth. The results suggest that prenatal cocaine exposure causes a sex-specific loss of cardioprotection by ischemic preconditioning in adult offspring, which is most likely due to fetal programming of PKCepsilon gene repression, resulting in a downregulation of PKCepsilon function in the heart of adult male offspring.

Ischemic preconditioning: clinical relevance and investigative studies

Experimental animal studies have shown that repetitive brief coronary occlusions render the heart resistant to myocardial infarction from subsequent, more prolonged, coronary occlusions. This phenomenon in animal models has been called ischemic preconditioning. In a number of clinical scenarios, the second in a series of ischemic episodes appears to be less severe than the first, suggesting that ischemic preconditioning also occurs in humans. If the mediator of preconditioning could be identified, it is conceivable that this agent could be administered to patients with coronary artery disease as a myocardial protectant. However, the definite clinical relevance of this interesting experimental finding remains unknown. Unlike the case in animal models subjected to an abrupt occlusion, preconditioning is difficult to study in the clinical setting. This article reviews the findings and limitations of the relevant clinical studies looking for ischemic preconditioning in humans.

Preinfarction angina prevents left ventricular remodeling in patients treated with thrombolysis for myocardial infarction

BACKGROUND

It has been shown that preinfarction angina may have beneficial effects on infarct size and mortality. However, there are no studies that have serially assessed the impact of preinfarction angina on left ventricular (LV) function in a large series of patients.

HYPOTHESIS

The study was undertaken to determine whether preinfarction angina (within 7 days before infarction) influences LV remodeling.

METHODS

In all, 119 consecutive patients with acute myocardial infarction were serially evaluated by 2-dimensional echocardiography (on Days 1, 2, 3, and 7; at 3 and 6 weeks; and at 3, 6, and 12 months following infarction). Left ventricular volumes were determined using Simpson's biplane formula and normalized for body surface area. Wall motion score index and sphericity index were calculated for each study. Coronary angiography was performed before discharge.

RESULTS

Preinfarction angina was detected in 39 of 119 patients. Initial echocardiographic and clinical data as well as the incidence of patent infarct-related artery and collaterals were similar for patients with and without preinfarction angina. In the subset of thrombolysed patients, patients with preinfarction angina showed decrease of LV end-diastolic and end-systolic volumes during the follow-up period (p = 0.033 and p = 0.001, respectively), and improvement of wall motion score index (p < 0.001) and ejection fraction occurred (p = 0.001), without changing of LV shape (p > 0.05); in addition, patients with preinfarction angina had smaller LV volumes and higher ejection fraction than did those without angina, from 3 weeks onward. These favorable effects were not detected in patients not treated with thrombolysis.

CONCLUSIONS

These data indicate that preinfarction angina has an inhibiting effect on long-term LV remodeling in patients who underwent thrombolysis for first acute myocardial infarction. It appears that preinfarction angina has no impact on infarct size and early postinfarction LV function.

Loss of cardioprotection with ageing

Not only the prevalence, but also the mortality due to ischaemic cardiovascular disease is higher in older than in young humans, and the demographic shift towards an ageing population will further increase the prevalence of age-related cardiovascular disease. In order to develop strategies aimed to limit reversible and irreversible myocardial damage in older patients, there is a need to better understand age-induced alterations in protein expression and cell signalling. Cardioprotective phenomena such as ischaemic and pharmacological pre and postconditioning attenuate ischaemia/reperfusion injury in young hearts. Whether or not pre and postconditioning are still effective in aged organs, animals, or patients, i.e. under conditions where such cardioprotection is most relevant, is still a matter of debate; most studies suggest a loss of protection in aged hearts. The present review discusses changes in protein expression and cell signalling important to ischaemia/reperfusion injury with myocardial ageing. The efficacy of cardioprotective manoeuvres, e.g. ischaemic pre and postconditioning in aged organs and animals will be discussed, and the development of strategies aimed to antagonize the age-induced loss of protection will be addressed.

The impact of preinfarction angina on electrocardiographic ischemia grades in patients with acute myocardial infarction treated with primary percutaneous coronary intervention

OBJECTIVE

Grade 3 ischemia (G3I) is defined as ST elevation with distortion of the terminal portion of the QRS (emergence of the J point > 50% of the R wave in leads with qR configuration, or disappearance of the S wave in leads with an Rs configuration). Patients with G3I on the presenting electrocardiogram (ECG) had worse prognosis than the patients with lesser (grade 2-G2I) ischemia. The aim of this study is to examine the effects of preinfarct angina (PIA) on electrocardiographic ischemia grades.

METHODS

One hundred forty-eight consecutive patients with ST-segment myocardial infarction (STEMI) were included in this study. All patients underwent primary percutaneous coronary intervention. The admission ECGs was analyzed retrospectively for electrocardiographic ischemia grades and compared with the presence of PIA.

RESULTS

Study population consisted of 110 patients with G2I (88 men, mean age = 63 +/- 6 years) and 38 patients with G3I (32 men, mean age = 61 +/- 8 years). Baseline characteristics of the groups were the same except for patients with G3I had significantly longer pain to balloon time and higher admission creatine kinase MB isoenzyme (CK-MB) levels. Tissue myocardial perfusion grade (TMPG) was better in patients with G2I. While 18 patients (47%) with G3I had PIA, 81 patients (70%) with G2I had PIA (P = 0.005). Although pain to balloon time and admission CK-MB were independent predictor of worse electrocardiographic ischemia grade (OR 1.69, 95% CI 1.09-2.62; P = 0.01; OR 1.01, 1.00-1.02, P = 0.04), PIA and left ventricular ejection time (LVEF) were independent predictors of better electrocardiographic ischemia grade (OR 0.4, 95% CI 0.17-0.90; P = 0.02, OR 0.92, 95% CI 0.85-0.99; P = 0.03, respectively) in multivariate logistic regression analysis.

CONCLUSION

PIA is one of the most important clinical predictors of better ischemia grades especially when combined with the pain to balloon time, LVEF, and admission CK-MB levels in patients with STEMI. This study provided another evidence for the protective effects of PIA.

Extent of myocardial ischemia during coronary occlusion in single vessel disease. A comparison between patients with exercise-induced angina and patients with recurrent angina at rest

Patients with exercise angina >2 months (n:13) showed significantly lower SigmaST elevation during 120 s balloon coronary occlusion than those with =<2 months (n:7), or those with angina at rest <=2 days (n:8) but similar to patients with angina at rest >2 days (n:7). These results underscore the importance of the kind and duration of angina in limiting the extent of ischemia during coronary occlusion.

Heat stress activates AKT via focal adhesion kinase-mediated pathway in neonatal rat ventricular myocytes

Heat stress (HS)-induced cardioprotection is associated with increased paxillin localization to the membrane fraction of neonatal rat ventricular myocytes (NRVM). The purpose of this study was 1) to examine the subcellular signaling pathways activated by HS; 2) to determine whether myocardial stress organizes and activates an integrated survival pathway; and 3) to investigate potential downstream cytoprotective proteins activated by HS. After HS, NRVM were subjected to chemical inhibitors (CI) designed to simulate ischemia by inhibiting both glycolysis and mitochondrial respiration. Protein kinase B (AKT) expression (wild type) was increased selectively with an adenoviral vector. Cell signaling was analyzed with Western blot analysis, while oncosis/apoptosis was assayed by measuring Trypan blue exclusion and/or terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) staining, respectively. HS increased phosphorylation of focal adhesion kinase (FAK) at tyrosine 397 but did not adversely affect the viability of NRVM before CI. HS increased association between FAK and phosphatidylinositol 3-kinase as well as causing a significant increase in AKT activity. Increased expression of wild-type AKT protected myocytes from both oncotic and apoptotic cell death. Increased expression of a FAK inhibitor, FRNK, reduced AKT phosphorylation in response to HS both at time 0 and after 10 min of CI compared with myocytes expressing empty virus. We conclude that myocardial stress activates cytoskeleton-based signaling pathways that are associated with protection from lethal cell injury.

Delayed inhibition of agonist-induced granulocyte-platelet aggregation after low-dose sevoflurane inhalation in humans

BACKGROUND

Sevoflurane can be used as sedative-analgesic drug with endothelial protective properties. We tested whether low-dose sevoflurane inhalation provides sustained inhibition of detrimental granulocyte-platelet aggregation in humans.

METHODS

Ten healthy male volunteers were enrolled in this crossover study. Each subject inhaled sevoflurane for 1 h at 0.5-1 vol % end-tidal concentration in oxygen (50 vol %). Inhaling oxygen (50 vol %) alone served as control. Venous blood samples were collected at baseline before inhalation, immediately after inhalation, and 24 h thereafter, and were used for flow cytometry to determine platelet surface marker (CD41, CD42b, CD62P/P-selectin, and PAC-1) on platelets and granulocytes and for kaolin-induced clot formation, as assessed by thromboelastography. In flow cytometry experiments, platelets were stimulated with arachidonic acid (AA, 30 microM), adenosine diphosphate (ADP, 1 microM), and thrombin receptor agonist peptide-6 (TRAP-6, 6 microM).

RESULTS

AA, ADP, and TRAP-6 markedly increased the expression of CD62P on platelets, whereas CD42b (shedding) and PAC-1 (heterotypic conjugates) expression decreased. The amount of granulocyte-platelet aggregates increased upon agonist stimulation. Low-dose sevoflurane inhalation reduced ADP-induced CD62P expression on platelets 24 h after inhalation, and inhibited the formation of granulocyte-platelet aggregates under stimulation with AA and ADP after 1 and 24 h, and with TRAP-6 after 24 h compared with control. Inhibition of granulocyte-platelet aggregates was accompanied by reduced clot firmness 24 h after sevoflurane inhalation compared with control.

CONCLUSIONS

We demonstrated for the first time that inhaling low-dose sevoflurane (<1 vol % end-tidal) inhibits agonist-induced granulocyte-platelet interactions 24 h after administration and thus counteracts thromboinflammatory processes.

Treadmill exercise test with dual isotope scintigraphy documents the second window of preconditioning in humans

BACKGROUND

In experimental studies, two windows of preconditioning have been identified, one lasting 1-2h and a second one (SWOP) starting 24h later and lasting 3-4 days. We sought to document SWOP in humans, using scintigraphy as an objective method of imaging.

METHODS

Nineteen male patients, aged 62+/-7 years with documented coronary artery disease underwent two treadmill exercise tests (at baseline and 30 h later) and three tomographic perfusion studies (during the first exercise test, during the redistribution phase 4 h later and during the second exercise test 30 h later) with two different isotopes. Thallium-201 (TL) was used for the assessment of the first exercise and the redistribution phase, whereas technetium 99m tetrofosmin (TET) was used 30 h later for the evaluation of SWOP. Both exercise tests terminated at the same time-point. The distribution of TL and TET uptake was analyzed qualitatively using a 5-point scale on a 17-segment myocardial model. Perfusion score was derived by summing the uptake of all segments, while total perfusion defect by subtracting the polar map of the first exercise test from that of the second exercise test.

RESULTS

Anginal symptoms were reported by 13 of 19 patients (68%) in the first test versus only 2 of 19 patients (11%) in the second one (p=0.001). The mean maximum ST segment depression was significantly reduced in the second test (from 1.58+/-0.73 to 0.82+/-1.07, p<0.01). Similarly, the perfusion score was reduced from 21.0+/-7.4 to 14.2+/-5.7 in the second test (p<0.01) and the total defect size from 24+/-16 to 12+/-14 (p<0.01).

CONCLUSION

The myocardial perfusion improvement during the second exercise study confirms objectively the existence of SWOP in humans.

Interaction of cardiovascular risk factors with myocardial ischemia/reperfusion injury, preconditioning, and postconditioning

Therapeutic strategies to protect the ischemic myocardium have been studied extensively. Reperfusion is the definitive treatment for acute coronary syndromes, especially acute myocardial infarction; however, reperfusion has the potential to exacerbate lethal tissue injury, a process termed "reperfusion injury." Ischemia/reperfusion injury may lead to myocardial infarction, cardiac arrhythmias, and contractile dysfunction. Ischemic preconditioning of myocardium is a well described adaptive response in which brief exposure to ischemia/reperfusion before sustained ischemia markedly enhances the ability of the heart to withstand a subsequent ischemic insult. Additionally, the application of brief repetitive episodes of ischemia/reperfusion at the immediate onset of reperfusion, which has been termed "postconditioning," reduces the extent of reperfusion injury. Ischemic pre- and postconditioning share some but not all parts of the proposed signal transduction cascade, including the activation of survival protein kinase pathways. Most experimental studies on cardioprotection have been undertaken in animal models, in which ischemia/reperfusion is imposed in the absence of other disease processes. However, ischemic heart disease in humans is a complex disorder caused by or associated with known cardiovascular risk factors including hypertension, hyperlipidemia, diabetes, insulin resistance, atherosclerosis, and heart failure; additionally, aging is an important modifying condition. In these diseases and aging, the pathological processes are associated with fundamental molecular alterations that can potentially affect the development of ischemia/reperfusion injury per se and responses to cardioprotective interventions. Among many other possible mechanisms, for example, in hyperlipidemia and diabetes, the pathological increase in reactive oxygen and nitrogen species and the use of the ATP-sensitive potassium channel inhibitor insulin secretagogue antidiabetic drugs and, in aging, the reduced expression of connexin-43 and signal transducer and activator of transcription 3 may disrupt major cytoprotective signaling pathways thereby significantly interfering with the cardioprotective effect of pre- and postconditioning. The aim of this review is to show the potential for developing cardioprotective drugs on the basis of endogenous cardioprotection by pre- and postconditioning (i.e., drug applied as trigger or to activate signaling pathways associated with endogenous cardioprotection) and to review the evidence that comorbidities and aging accompanying coronary disease modify responses to ischemia/reperfusion and the cardioprotection conferred by preconditioning and postconditioning. We emphasize the critical need for more detailed and mechanistic preclinical studies that examine car-dioprotection specifically in relation to complicating disease states. These are now essential to maximize the likelihood of successful development of rational approaches to therapeutic protection for the majority of patients with ischemic heart disease who are aged and/or have modifying comorbid conditions.

Preconditioning in humans

Brief ischemia to the myocardium initiates a cascade of biochemical events in cardiac myocytes that protects the heart muscle during subsequent ischemic insults. This phenomenon is called ischemic preconditioning. If an acute myocardial infarction is preceded by preinfarction angina, it results in smaller infarction size, fewer cardiac arrhythmias, and better-left ventricular function. During coronary intervention, brief balloon inflation protects the heart during subsequent inflations. Patients vary in the degree of preconditioning and those patients who have the ability to demonstrate a significant preconditioning effect will have lesser incidence of subsequent cardiac events. Preconditioning protects the myocardium during coronary artery bypass surgery, particularly in the off-pump procedure, yet the thoracic surgery community has not universally adopted this technique.

Ischemia reperfusion injury, preconditioning and critical illness

The purpose of this review is to describe in more detail ischemia reperfusion injury and preconditioning, and to speculate on the potential role of preconditioning in the care of critically ill patients. Current hemodynamic treatment of hypotension and hypoperfusion in critically ill patients is directed at ensuring essential organ perfusion by maintaining intravascular volume and cardiac output, and ensuring adequate oxygen delivery by maintaining arterial oxygen partial pressure and hemoglobin levels. However, morbidity and mortality remain high and new approaches to critically ill patients are required. Treatments are needed that can protect against organ ischemia during periods of low blood flow. In recent years, there has been a growing appreciation of the importance of ischemia reperfusion injury. Ischemia associated with reperfusion may result in greater injury than ischemia alone. Ischemic preconditioning is used to describe the protective effect of short periods of ischemia to an organ or tissue against longer periods of ischemia. Although first described in the myocardium, there is now evidence that this phenomenon occurs in a wide variety of organs and tissues, including the brain and other nervous tissue such as the retina and spinal cord, liver, stomach, intestines, kidney, and the lungs. Preconditioning therapy may offer a new avenue of treatment in critically ill patients. Both traditional preconditioning methods and pharmacologic agents that mimic or induce such preconditioning may be used in the future. Clinical trials of pharmacologic agents are underway in patients with coronary artery disease. Further trials of such methods and agents are needed in critically ill patients suffering from sepsis or multiorgan system failure.

Ischemic Preconditioning: Implications for the Geriatric Heart

Ischemic preconditioning is among the most consistent and powerful modes of reducing myocardial infarct size. Although several clinical studies have suggested that the human heart can be preconditioned, controversy exists in both the experimental and clinical literature as to whether the senescent heart can be preconditioned. The authors recently reported that older patients (> or = 60 years of age) in the Thrombolysis in Myocardial Infarction-4 study appeared to benefit from a history of angina prior to acute myocardial infarction. This observation may lead to a clinical counterpart to successful preconditioning in the older heart.

Effect of a hypoglycemic agent on ischemic preconditioning in patients with type 2 diabetes and stable angina pectoris

OBJECTIVE

Ischemic preconditioning is an increased tolerance to myocardial ischemia during the second of two consecutive exercise tests. ATP-sensitive K(+) channel blockers, such as glinides and sulfonylurea drugs, can induce loss of ischemic preconditioning. This study aimed to investigate the effects of repaglinide, a hypoglycemic agent with an affinity for myocardial ATP-sensitive K (+)channels, on the results of consecutive exercise tests in patients with diabetes and multivessel coronary artery disease.

METHODS

Forty-two patients with type 2 diabetes and chronic stable angina pectoris, and two-vessel or three-vessel disease participated in this study. The patients underwent two consecutive treadmill exercise tests (phase 1). On the day after these exercise tests, 2 mg of oral repaglinide was given to the patients. One week later, two exercise tests were repeated consecutively (phase 2).

RESULTS

All patients achieved 1.0-mm ST-segment depression during the four exercise tests (T1, T2, T3, and T4). In phase 2, seven patients improved in time to onset of 1.0-mm ST-segment depression. The worsening of the time to onset of 1.0-mm ST-segment depression in phase 2 demonstrated ischemic preconditioning block in 83.3% of patients (P=0.0001). Even the postexercise electrocardiographic parameters (ST-segment depression morphology and magnitude and arrhythmias) were significantly different between the groups with and without pharmacologic ischemic preconditioning block (P=0.031).

CONCLUSIONS

Repaglinide, an oral hypoglycemic agent with ATP-sensitive K(+) channel-blocker activity, eliminated the myocardial ischemic preconditioning in patients with coronary disease and diabetes.

Preoperative unstable angina causes venous adaptation to surgical graft injury

Ischemic preconditioning may provide a systemic organ protection, evident as the phenomenon known as remote preconditioning. Unstable angina may be a clinical analogue to ischemic preconditioning. Vein graft harvesting induces inflammation of the graft wall. We hypothesized that preoperative unstable angina preconditions vein grafts and reduces the inflammatory response to graft harvesting. Consecutive patients with stable or unstable angina undergoing open heart surgery (n = 12 in each group) were studied. Saphenous vein biopsies were collected at the start of graft harvesting, and when the last proximal anastomosis to the aorta was finished (average 112 minutes later). Gene expression of inflammatory mediators (tumor necrosis factor alpha, interleukin-1beta (IL-1beta), E-selectin (CD62E), intercellular leukocyte adhesion molecule 1, inducible nitric oxide synthase, endothelin-1) increased after surgical handling (semiquantitative RT-PCR). In vein grafts from unstable patients the increase was attenuated for Il-1beta (p < 0.004) and CD62E (p < 0.001). In stable patients the protein expression of IkappaBalpha and heat shock protein72 was reduced by surgical handling (p < 0.04), but was not influenced in unstable patients (immunoblotting). In vitro relaxation to acetylcholine was enhanced, and contractions to phenylephrine and endothelin-1 were attenuated in veins rings from unstable patients (p < 0.003). In conclusion, surgical handling of vein grafts induces inflammation of the vessel wall. This response was reduced in grafts from patients with unstable angina, indicating a possible systemic preconditioning-like effect of acute coronary syndromes.

Chronic Angiotensin II Receptor Blockade Induces Cardioprotection During Ischemia by Increased PKC-ε Expression in the Mouse Heart

INTRODUCTION

This study was performed to investigate the role of chronic pretreatment with angiotensin II type 1 receptor antagonists (ARB) and angiotensin converting enzyme inhibitors (ACE-I) in myocardial infarction (MI) and ischemic preconditioning (iPC). Little is known about molecular mechanisms of MI and iPC, especially about protein kinase C (PKC) isozyme levels induced by chronic pharmacologic pretreatment with ARB and ACE-I. To address one of the most important signal molecules in iPC, the PKC system was investigated in an ischemia/reperfusion model using isolated mouse hearts.

METHODS

C57/BL6 mice were treated orally with candesartan cilexetil or ramipril for 2 weeks. Isolated perfused hearts were subjected to 60 minutes of left anterior descending occlusion and 30 minutes of reperfusion. IPC was performed by 3 cycles of 5 minutes of ischemia prior to the infarct ischemia. Infarct size was measured using the propidium iodide method, and PKC isoenzymes were detected by immunoblotting in the membrane and cytosolic fraction.

RESULTS

In the control group, iPC reduced infarct size from 59.8 +/- 4.2% to 24.5 +/- 1.7%. ARB pretreatment itself reduced the infarct size significantly (38.1 +/- 3.0%) in hearts without iPC. This protection could neither be enhanced by additional iPC (40.3 +/- 3.4%) nor blocked by the AT2-receptor antagonist PD123.319 (40.7 +/- 3.7%). The ARB-induced cardio protection, however, was abolished by chelerythrine (5 micromol/L) (71.7 +/- 6.6%, n = 11, P < 0.001). Furthermore, PKC-epsilon (PKC-epsilon) was significantly increased in the particulate fraction of ARB-pretreated mice. On the contrary, chronic treatment with ACE-I completely blocked iPC (57.7 +/- 3.9%, n = 12, P < 0.001) without any effect on infarct size itself (51.5 +/- 3.0%, n = 12). PKC-epsilon expression was significantly reduced.

CONCLUSION

Chronic AT1-receptor antagonism is capable of protecting the heart against myocardial infarction in a PKC-epsilon-dependent way. Furthermore, chronic treatment with ACE-I is suggested to have suppressing effects on iPC, possibly caused by reduced PKC-epsilon expression.

Initial Q waves accompanying ST-segment elevation at presentation of acute myocardial infarction and 30-day mortality in patients given streptokinase therapy: an analysis from HERO-2

BACKGROUND

The presence of pathological Q waves in the infarct leads on the surface electrocardiogram in an ST-elevation acute myocardial infarction indicates myocardial necrosis. Clinically it might be difficult to ascertain the onset of acute myocardial infarction. Our aim was to assess whether the presence or absence of Q waves at presentation could be used as an indicator of the duration of acute myocardial infarction and predict mortality.

METHODS

15,222 patients with ST-elevation acute myocardial infarction and normal intraventricular conduction were randomly assigned streptokinase and aspirin plus bivalirudin or unfractionated heparin in the HERO-2 trial; randomisation did not alter 30-day mortality. 10,244 patients (67%) had Q waves in the infarct territory at the time of randomisation, and 4978 (33%) did not. The primary endpoint was 30-day mortality.

FINDINGS

There were more deaths at 30 days in patients with initial Q waves than in those without (1044 [10%] vs 344 [7%], p<0.0001). These findings were similar in patients with a first acute myocardial infarction and when stratified by time to randomisation (0-2, >2-4, >4 h) and by acute myocardial infarction location (anterior or inferior). Both the presence of initial Q waves and time to randomisation were positive univariate predictors, but only the presence of initial Q waves independently predicted 30-day mortality on multivariate analysis (adjusted OR 1.44, 95% CI 1.25-1.65 with clinical indices, and 1.31, 1.12-1.54 with clinical plus ST indices included as predictors).

INTERPRETATION

The presence of Q waves in the infarct leads at presentation of ST-elevation acute myocardial infarction independently predicts higher 30-day mortality in patients treated with fibrinolytic therapy. Therefore, a more aggressive approach to reperfusion might be warranted in these patients.

Ventricular fibrillation in acute myocardial infarction before and during primary PCI

BACKGROUND

There are scarce and sometimes contradictory data about ventricular fibrillation (VF) during the acute phase of MI. In-hospital VF most often occurs with inferior MI, when treated with fibrinolytics. Out-of-hospital VF seems to be associated with anterior MI. We studied characteristics of patients with VF during reperfusion therapy by primary angioplasty (PCI) versus patients with VF before PCI.

METHODS

From January 1995 until December 2001, we treated 2826 patients for acute MI and reviewed clinical records of all patients who developed VF and classified the patients according to the first episode of VF: either before or during the angioplasty procedure.

RESULTS

VF developed in 219 (8%) patients. Patients with VF during reperfusion therapy (n=74, 3%) were older (p=0.03), more frequently female (0.04), less often had heart failure (p=0.04), when compared with patient with VF before PCI (n=145, 5%). Patients with VF during PCI experienced more often preinfarction angina (p=0.009) and suffered more often from inferior MI (p=0.001), when compared with patients with VF before PCI.

CONCLUSIONS

Patients with early VF before reperfusion have different characteristics when compared with patients with VF during reperfusion. Infarct location is a major determinant of timing of VF, when both groups are compared (p<0.001).

Myocardial preconditioning and cardioprotection by volatile anaesthetics

The biological bases and the clinical applications of ischaemic and anaesthetic preconditioning are reviewed. Ischaemic preconditioning is an endogenous defensive phenomenon of the myocardium in which brief periods of ischaemia followed by reperfusion reduce the infarct size induced by longer ischaemic stimuli; both an early and a late phase may be distinguished. In the early phase, the mediators released activate ATP-dependent potassium channels and kinase cascade; these enzymes migrating at the level of various subcellular structures phosphorylate some end-effectors responsible for cardioprotection. Several molecules that are involved in the regulation of cell death during ischaemia-reperfusion injury have been proposed for such a role, including mitochondrial ATP-dependent potassium channels, connexins and cytoskeletal and mitochondrial proteins. In the late phase, the triggers and mediators themselves, plus nitric oxide, are responsible for the genetic reprogramming providing a protective effect via ex-novo synthesis of proteins. Volatile halogenated anaesthetics may induce a particular sort of pharmacological preconditioning, anaesthetic preconditioning, which presents some differences in the biochemical signalling mechanism but is able to give protection comparable to the ischaemic form. Anaesthetic preconditioning presents obvious advantages compared to ischaemic preconditioning, and researchers have tried to take advantage of this in the clinical setting, in cardiac surgical patients, in neuroprotection and to prolong the survival of organs destined for transplantation.

Ischemic preconditioning and preinfarction angina in the clinical arena

In animals, brief episodes of ischemia before a total coronary occlusion protect the heart and result in a smaller myocardial infarct size. In humans, episodes of angina before acute myocardial infarction might also confer a preconditioning or protective effect; numerous studies show that preinfarction angina is associated with smaller infarcts. Preinfarction angina is also associated with reductions in ventricular dysfunction, arrhythmias and incidence of no-reflow phenomena, and, in some cases, improved survival. The protective effect of preconditioning in humans is characterized by marked individual variations and seems to be attenuated in women, people with diabetes and the elderly. Exercise seems to be an important way to induce preconditioning in humans and preserves it in the elderly.

Pro-inflammatory cytokines may induce late preconditioning in unstable angina patients

Late preconditioning can be induced by a wide variety of stimulus, including non-pharmacological and pharmacological. Thus, late preconditioning is a universal response of the heart to stress and it requires the simultaneous activation of multiple stress-responsive genes. Recently, compelling evidence has evolved that the up-regulation of pro-inflammatory cytokines plays an important role in induction of the late phase of ischemic preconditioning in rodent models. However, the role of cytokines in induction of late preconditioning in humans has not been explored. Patients with unstable coronary syndromes have a systemic inflammatory responses with increase of the pro-inflammatory cytokines, such as TNFalpha, IL-6. And some researchers find the patients undergoing CABG with unstable angina have a better cardioprotective effect caused by late preconditioning characterized by the activated NF-kappaB and synthesized effector proteins (HSP72 and eNOS). Therefore, we hypothesize that pro-inflammatory cytokines may induce late preconditioning in unstable angina patients directly or through remote preconditioning. It is difficult to test our hypotheses in vivo, but in vitro, human tissue culture with isolated atrial myocardium could be tested. If the hypotheses is true, the biological complication is immense. A new physiological function of pro-inflammatory cytokines is found, that is, inducing endogenous cytoprotection. From the clinical point of view, administering the appropriate pro-inflammatory cytokines will be beneficial to patients before cardiac surgery.

[Myocardial preconditioning with volatile anesthetics. General anesthesia as protective intervention?]

Reduction of the perioperative cardiovascular risk with pharmacological interventions plays a prominent role in routine anesthesia practice. For example, perioperative beta-blockade is well established in anesthesiological treatment of patients. There is a growing body of evidence supporting the cardioprotective effects of volatile anesthetics known as anesthetic-induced preconditioning. There are numerous and complex data from animal studies. The mechanisms of anesthetic-induced preconditioning have been extensively studied but have still not been clearly identified. Initial clinical data show the cardioprotective effects of volatile agents by looking at parameters of myocardial function and laboratory values and therefore, the question of the relevance of these data for routine clinical practice has been raised. This review gives a summary of the currently available data focusing on the mechanisms of anesthesiological preconditioning and clinical studies.

Brief repetitive balloon occlusions enhance reperfusion during percutaneous coronary intervention for acute myocardial infarction: a pilot study

The objective of this study was to determine whether acutely ischemic myocardium may be conditioned during percutaneous coronary intervention for acute myocardial infarction. Ischemic preconditioning is a powerful cardioprotective mechanism that limits infarct size in animal investigations and ischemic sequelae during percutaneous coronary intervention in man. However, the conditioning stimulus in all these studies has been applied prior to the defining episode of ischemia. Seventeen patients undergoing percutaneous coronary intervention for acute myocardial infarction were randomly assigned to a standard ischemic preconditioning protocol (n = 10) or a usual-care control group (n =7). ST segment shift response and Doppler-derived distal coronary velocity data were compared. Despite similar degrees of baseline ST segment elevation, the magnitude of final ST segment elevation in the conditioning group was less than that in controls at the protocol conclusion (conditioning, 1.60 +/- 0.8 mV; control, 4.0 +/- 0.5 mV; P < 0.001). The rate of ST segment resolution was greater in the conditioning group (conditioning, 0.28 +/- 0.1 mV/min; control, 0.12 +/- 0.1 mV/min; P = 0.02). Distal coronary velocimetry indicated significant improvement in coronary flow velocity reserve in the conditioning group at the protocol conclusion (conditioning, 1.8 +/- 0.2; control, 1.4 +/- 0.1; P < 0.008). Brief periods of occlusion and reperfusion during percutaneous intervention for acute myocardial infarction mitigate the extent of ischemic injury and improve distal myocardial perfusion. Such ischemic conditioning represents a potentially useful adjunct to strategies for enhancing reperfusion during acute myocardial infarction.

Morphine Induces Late Cardioprotection in Rat Hearts In Vivo: The Involvement of Opioid Receptors and Nuclear Transcription Factor ??B

Delta1-opioid receptor agonists can induce cardioprotection by early and late preconditioning (LPC). Morphine (MO) is commonly used for pain treatment during acute coronary syndromes. We investigated whether MO can induce myocardial protection by LPC and whether a nuclear transcription factor kappaB (NF-kappaB)-dependent intracellular signaling pathway is involved. Rats were subjected to 25 min of regional ischemia and 2 h of reperfusion 24 h after treatment with saline (NaCl; 0.9% 5 mL), lipopolysaccharide of Escherichia coli (LPS; 1 mg/kg), or MO (3 mg/kg). LPS is a trigger of LPC and served as positive control. Naloxone (NAL) was used to investigate the role of opioid receptors in LPC and was given before NaCl, LPS, or MO application (trigger phase) or before ischemia-reperfusion (mediator phase). Infarct size (percentage area at risk) was 59% +/- 9%, 51% +/- 6%, or 53% +/- 10% in the NaCl, NAL-NaCl, and NaCl-NAL groups, respectively. Pretreatment with MO reduced infarct size to 20% +/- 6% after 24 h (MO-24h), and this effect was abolished by NAL in the trigger (NAL-MO, 53% +/- 14%) and in the mediator (MO-NAL, 60% +/- 8%) phases. Pretreatment with LPS reduced infarct size to 23% +/- 8%. NAL administration in the trigger phase had no effect on infarct size (NAL-LPS 30% +/- 16%), whereas NAL during the mediator phase of LPC abolished the LPS-induced cardioprotection (LPS-NAL 54% +/- 8%). The role of NF-kappaB in morphine-induced LPC was investigated by Western blot and electrophoretic mobility shift assay. Morphine and LPS treatment increased phosphorylation of the inhibitory protein kappaB, leading to an increased activity of NF-kappaB. Thus, MO induces LPC similarly to LPS and it is likely that this cardioprotection is mediated at least in part by activation of NF-kappaB. Opioid receptors are involved as mediators in both MO- and LPS-induced LPC but as triggers only in MO-induced LPC.

IMPLICATIONS

Like lipopolysaccharide, morphine induces late preconditioning and activation of nuclear transcription factor-kappaB. Opioid receptors are involved as mediators in both morphine- and lipopolysaccharide-induced late preconditioning but as triggers only in morphine-induced late preconditioning.

Cardioprotective-Mimetics Reduce Myocardial Infarct Size in Animals Resistant to Ischemic Preconditioning

BACKGROUND

Ischemic preconditioning (IPC) elicits two distinct windows of cardioprotection, an early phase that lasts for 1-2 h and a delayed phase that lasts for 24-72 h. However, there is conflicting data as to how long the heart is resistant to IPC-induced cardioprotection after the initial protection wanes, leading to the demonstration of IPC-resistance. This resistance to IPC appears to be dependent on the timing of the next IPC stimulus, the species of animals used and the model studied. Furthermore, the mechanisms responsible IPC-resistance are unknown. It is also important to demonstrate therapeutic interventions that will produce cardioprotection during this period of IPC-resistance.

METHODS AND RESULTS

To examine potential mechanisms responsible for acute IPC-induced resistance, the NHE-1 inhibitor EMD 85131 (2-methyl-5-methylsulfonyl-1-(1-pyrrollyl)-benzoylguanidine), which exerts its effects via mechanisms distinct from IPC, and the K(ATP) channel opener bimakalim, which bypasses the signaling mechanisms of IPC to directly open K(ATP) channels, were examined in a canine model of IPC-resistance. One 10 min. IPC stimulus followed by 10 min. of reperfusion produced a significant reduction in IS/AAR compared to Control (7.1 +/- 2.6% versus 26.0 +/- 6.2%; P < 0.05). However, IPC did not significantly protect the myocardium if a 2 h reperfusion period occurred between the initial IPC stimulus and the subsequent prolonged (60 min) ischemic challenge (IS/AAR: 22.5 +/- 4.8%: P > 0.05). Furthermore, hearts treated with IPC followed by 2 h of reperfusion were resistant to an additional IPC stimulus administered just prior to the subsequent 60 min. occlusion period (IS/AAR: 22.9 +/- 3.2%: P > 0.05). In contrast, administration of the NHE-1 inhibitor EMD 85131 (IS/AAR: 7.4 +/- 2.5%: P < 0.05) or the K(ATP) channel opener bimakalim (IS/AAR: 11.8 +/- 2.4%: P < 0.05) both afforded significant cardioprotection when administered at 2 h of reperfusion in previously preconditioned canine hearts resistant to IPC.

CONCLUSIONS

IPC resistance occurs in this canine model of ischemia-reperfusion injury. However, in spite of IPC resistance, hearts can still be pharmacologically protected by direct application of the K(ATP) channel opener bimakalim or the NHE inhibitor EMD 85131.

Beneficial effect of preinfarction angina on in-hospital outcome is preserved in elderly patients undergoing coronary intervention for anterior acute myocardial infarction

BACKGROUND

Preinfarction angina improves survival after acute myocardial infarction (AMI) in nonelderly but not elderly patients in the thrombolytic era. However, it remains unclear whether preinfarction angina has a beneficial effect on clinical outcome in elderly patients undergoing percutaneous coronary intervention (PCI).

METHODS AND RESULTS

The study group comprised 484 anterior AMI patients who were admitted within 24 h of onset and underwent emergency PCI. Patients were divided into 2 groups: those aged < 70 years (nonelderly patients, n = 290) and those aged > or = 70 years (elderly patients, n = 194). Angina within 24 h before AMI was present in 42% of nonelderly patients and in 37% of elderly patients. In nonelderly patients, preinfarction angina was associated with a lower in-hospital mortality rate (1% vs 7%, p = 0.02). Similarly, in elderly patients, preinfarction angina was associated with a lower in-hospital mortality rate (6% vs 16%, p = 0.03). Multivariate analysis showed that the absence of preinfarction angina was an independent predictor of in-hospital mortality in both nonelderly (odds ratio 4.20; 95% confidence interval (CI) 1.20-10.6; p = 0.04) and elderly patients (odds ratio 3.04; 95%CI 1.06-18.1; p = 0.04).

CONCLUSIONS

Angina within the 24 h before AMI is associated with better in-hospital outcomes in elderly and nonelderly patients.

Effect of Acetylsalicylic Acid on Nuclear Factor-κB Activation and on Late Preconditioning Against Infarction in the Myocardium

Nuclear factor-kappaB (NF-kappaB) plays an essential role in the intracellular signal transduction of the second window of protection (SWOP). Acetylsalicylic acid (ASA) blocks NF-kappaB-dependent gene activation in leukocytes and endothelial cells through preventing phosphorylation and subsequent degradation of the inhibitor IkappaB-alpha. This study investigated the effect of ASA on the late phase of ischemic preconditioning (PC) against myocardial infarction and on the activation of NF-kappaB in the preconditioned myocardium. Conscious rabbits were subjected to 4 cycles of 5 minutes of coronary occlusion and 5 minutes of reperfusion together with 3 different doses of ASA (5 mg/kg; 25 mg/kg; 130 mg/kg). After 30 minutes of reperfusion we determined the activation of NF-kappaB with an electrophoretic mobility shift assay (EMSA). Twenty-four hours later, after 30 minutes of test ischemia, we performed infarct size analysis using triphenyltetrazolium-chloride (TTC) staining. Neither 5 mg/kg (antithrombotic dose) nor 25 mg/kg (analgesic/antipyretic dose) of ASA interfered with the NF-kappaB activation and the protective effect of late preconditioning against myocardial infarction. In contrast, NF-kB activation and late PC effect were completely abrogated by 130 mg/kg of ASA. Our results suggest that nonselective doses of NSAIDs should be used with caution in patients with atherosclerotic cardiovascular disease because they may deprive the heart of its innate defensive response.

Grade 3 ischemia on the admission electrocardiogram predicts rapid progression of necrosis over time and less myocardial salvage by primary angioplasty

BACKGROUND

Among patients with ST-elevation acute myocardial infarction, those with terminal QRS distortion (grade 3 ischemia) have higher mortality and larger infarct size (IS) than patients without QRS distortion (grade 2 ischemia).

METHODS

We assessed the relation of baseline electrocardiographic ischemia grades to area at risk (AR) and myocardial salvage [100 (AR-IS)/AR] in 79 patients who underwent primary angioplasty for first ST-elevation acute myocardial infarction and had technetium Tc 99m sestamibi single-photon emission computed tomography before angioplasty (AR) and at predischarge (IS). Patients were classified as having grade 2 ischemia (ST elevation without terminal QRS distortion in any of the leads, n = 48), grade 2.5 ischemia (ST elevation with terminal QRS distortion in 1 lead, n = 16), or grade 3 ischemia (ST elevation with terminal QRS distortion in >2 adjacent leads, n = 15).

RESULTS

Time to treatment was comparable among groups. AR was comparable among groups (38% +/- 20%, 33% +/- 23%, and 34% +/- 23%, respectively; P = .70). There were no differences among groups in residual myocardial perfusion (severity index 0.28 +/- 0.12, 0.29 +/- 0.16, and 0.30 +/- 0.15 in grades 2, 2.5, and 3 ischemia, respectively; P = .97). In contrast, there was a trend toward lower myocardial salvage (45% +/- 32%) in the grade 3 group than in the grade 2 (65% +/- 33%) and grade 2.5 (65% +/- 40%) groups ( P = .16). Salvage was dependent on time only in the grade 3 group. Spearman rank correlation coefficients between time to treatment and percentage salvage were 0.003 ( P = .99), -0.24 ( P = .38), and -0.63 ( P = .022) for grades 2, 2.5, and 3, respectively.

CONCLUSIONS

Patients with grade 3 ischemia have rapid progression of necrosis over time and less myocardial salvage. This admission pattern is a predictor of myocardial salvage by primary angioplasty.

Cardioprotection with volatile anesthetics: mechanisms and clinical implications

Cardiac surgery and some noncardiac procedures are associated with a significant risk of perioperative cardiac morbid events. Experimental data indicate that clinical concentrations of volatile general anesthetics protect the myocardium from ischemia and reperfusion injury, as shown by decreased infarct size and a more rapid recovery of contractile function on reperfusion. These anesthetics may also mediate protective effects in other organs, such as the brain and kidney. Recently, a number of reports have indicated that these experimentally observed protective effects may also have clinical implications in cardiac surgery. However, the impact of the use of volatile anesthetics on outcome measures, such as postoperative mortality and recovery in cardiac and noncardiac surgery, is yet to be determined.

High Serum Erythropoietin Level Is Associated With Smaller Infarct Size in Patients With Acute Myocardial Infarction Who Undergo Successful Primary Percutaneous Coronary Intervention

OBJECTIVES

We investigated whether a higher serum erythropoietin (EPO) level in patients with acute myocardial infarction (MI) subjected to successful primary percutaneous coronary intervention (PCI) can predict a smaller infarct size determined by creatine kinase (CK) release.

BACKGROUND

Erythropoietin has been shown to protect cardiomyocytes from ischemia-reperfusion injury in rodents.

METHODS

We prospectively studied 101 patients with first MI who received successful primary PCI within 12 h from the onset of MI. Blood samples were collected to examine the serum EPO level after the primary PCI and within 24 h from the onset of MI.

RESULTS

The peak CK level and cumulative CK release were significantly lower in the above-median EPO group than in the below-median EPO group. Thrombolysis In Myocardial Infarction (TIMI) grades and collateral grades before PCI, infarct-related coronary arteries, time to the successful reperfusion from the onset of MI, and serum creatinine levels were similar in the two EPO groups. A stepwise multiple regression analysis revealed that the absolute serum EPO level (mU/ml) as well as TIMI grades after PCI and preinfarction angina was an independent predictor for the cumulative CK release.

CONCLUSIONS

These data suggest that a high endogenous EPO level can predict a smaller infarct size in patients with acute MI subjected to successful primary PCI. This might be attributed to the potentially protective effect of endogenous EPO against ischemia-reperfusion injury in humans.

Pre? and postconditioning during cardiac surgery

In spite of improved myocardial protection, postoperative arrhythmias and cardiac failure are still important problems causing morbidity and mortality in cardiac surgery. Ischemic preconditioning has been widely investigated experimentally with the purpose of identifying new therapeutic agents, but we have not unraveled the underlying mechanisms and we are not able yet to exploit them pharmacologically in clinical practice. Studies of preconditioning in cardiac surgery provide conflicting results, but the majority of studies show that ischemic preconditioning is an effective adjunct to myocardial protection in cardiac surgery. Interventions aimed at modifying reperfusion, or postconditioning, have the advantage that they also can be used after the ischemic insult has occurred, i.e. also in situations with "non-scheduled" ischemia. Postconditioning, as preconditioning, needs pharmacological mimics to be used routinely in settings of cardiac surgery or other human interventions. Possible common signaling pathways of the two phenomena are discussed, and suggested directions for clinical studies are outlined.

In Vitro Platelet Responsiveness to Adenosine-Mediated ‘Preconditioning’ is Age-Dependent

BACKGROUND

Brief preconditioning (PC) ischemia, in addition to its well-described cardioprotective effects, has been shown in some studies to act on circulating platelets and attenuate platelet adhesion and aggregation in models of unstable angina and acute myocardial infarction. This "anti-platelet" effect of PC may be triggered by release of adenosine from ischemic/reperfused myocardium and activation of adenosine A(2) receptors on the platelets' surface. However: (1) all current data on the platelet inhibitory effects of PC ischemia and A(2) receptor stimulation have been obtained in adult populations; and (2) there is evidence of age-associated alterations in myocardial adenosine release, receptor responsiveness and post-receptor signaling.

OBJECTIVE

Our aim was to evaluate, using an established in vitro model of platelet aggregation and exogenous administration of an adenosine A(2) agonist, whether the favorable effects of adenosine A(2) receptor stimulation on platelet responsiveness are compromised in aging populations.

METHODS

Arterial blood samples were obtained from young adult versus old rabbits (6 months versus 4 years of age) and young adult versus senescent rats (4 months versus 2 years of age). Matched aliquots from each animal were randomly assigned to receive exogenous treatment with either the A(2) agonist CGS 21680 or vehicle. Maximum platelet aggregation was quantified by whole blood impedance aggregometry, using collagen as the aggregatory stimulus.

RESULTS

In young adult rabbits, maximum platelet aggregation was, as expected, reduced by 30 +/- 4% in CGS-treated aliquots versus vehicle-controls. In contrast, blood samples from 4 year old rabbits were refractory to A(2) receptor stimulation: in the old cohort, treatment with CGS evoked no change in platelet aggregation (decrease of 2 +/- 3% versus age-matched vehicle controls; p < .01 versus the decrease of 30% seen in young adults). Data obtained in the rat model were analogous to those seen in the rabbit: maximum platelet aggregation decreased by 18 +/- 5% versus 1 +/- 7% with CGS treatment in young adult versus senescent animals.

CONCLUSION

Our results provide novel in vitro evidence of an age-associated loss in platelet responsiveness to adenosine-mediated "preconditioning".

Preconditioning with sevoflurane decreases PECAM-1 expression and improves one-year cardiovascular outcome in coronary artery bypass graft surgery

BACKGROUND

Cardiac preconditioning is thought to be involved in the observed decreased coronary artery reocclusion rate in patients with angina preceding myocardial infarction. We prospectively examined whether preconditioning by sevoflurane would decrease late cardiac events in patients undergoing coronary artery bypass graft (CABG) surgery.

METHODS

Seventy-two patients scheduled for elective CABG surgery were randomized to preconditioning by sevoflurane (10 min at 4 vol%) or placebo. For all patients, follow-up of adverse cardiac events was obtained 6 and 12 months after surgery. Transcript levels for platelet-endothelial cell adhesion molecule-1 (PECAM-1/CD31), catalase and heat shock protein 70 (Hsp70) were determined in atrial biopsies after sevoflurane preconditioning.

RESULTS

Pharmacological preconditioning by sevoflurane reduced the incidence of late cardiac events during the first year after CABG surgery (sevoflurane 3% vs 17% in the placebo group, log-rank test, P=0.038). One patient in the sevoflurane group and three patients in the placebo group experienced new episodes of congestive heart failure and three additional patients had coronary artery reocclusion. Perioperative peak concentrations for myocardial injury markers were higher in patients with subsequent late cardiac events [NTproBNP, 9031 (4125) vs 3049 (1906) ng litre(-1), P<0.001; cTnT, 1.31 (0.88) vs 0.46 (0.29) microg litre(-1), P<0.001]. Transcript levels were reduced for PECAM-1 and increased for catalase but unchanged for Hsp70 in atrial biopsies after sevoflurane preconditioning.

CONCLUSIONS

This prospective randomized clinical study provides evidence of a protective role for pharmacological preconditioning by sevoflurane in late cardiac events in CABG patients, which may be related to favourable transcriptional changes in pro- and antiprotective proteins.

Protein Kinase C in Cardiac Disease and as a Potential Therapeutic Target

Protein kinase C (PKC) is a member of a large family of serine/threonine kinases that plays an integral role in many of the signaling cascades that govern cellular behavior. As such, it is intricately involved in the processes that mediate disease pathogenesis. Strategies that serve to alter PKC function may prove to be useful in the treatment of numerous disease states. This article reviews the various roles PKC may play in cardiovascular disease, specifically with regard to ischemic heart disease, cardiac hypertrophy, heart failure, hypertension, and atherosclerosis, and suggests the potential for developing therapeutic approaches that can target PKC activity.