Carvedilol Improves Myocardial Contractility Compared With Metoprolol in Patients With Chronic Hibernating Myocardium After Revascularization

Background: We tested the hypothesis of whether carvedilol delays morphologic degeneration and improves functional outcome compared with metoprolol tartrate in patients with hibernating myocardium undergoing surgical revascularization. We have previously shown that patients with chronic hibernating myocardium undergo progressive cellular degeneration and fibrosis.

Methods: Twenty patients with multivessel coronary artery disease revascularization and hibernating myocardium as assessed by technetium-99m perfusion scintigraphy and fluorine-18-fluorodeoxyglucose positron emission tomography were randomized to receive either carvedilol or metoprolol tartrate for at least 2 months before surgery, and this was continued for 7 months postoperatively. Left ventricular ejection fraction and regional wall motion abnormalities were assessed by left ventriculography at baseline and 7 months postoperatively. Intraoperative transmural needle biopsy samples were obtained for microscopic analysis.

Results: Postoperatively, the ejection fraction increased from 31% ± 5% to 44% ± 4% ( P < .005) in the carvedilol group (n = 10), and from 30% ± 6% to 40% ± 6% in the metoprolol tartrate group ( P < .05 vs preoperatively and vs carvedilol). Wall motion abnormalities in the carvedilol group improved from -2.1 ± 0.4 to -0.6 ± 0.5 ( P < .05) and from -2.3 ± 0.5 to -1.6 ± 0.6 in the metoprolol tartrate group ( P < .05 vs preoperatively and vs carvedilol). Microscopic analysis after 72 ± 18 days of either treatment showed mild cardiomyocyte degeneration and moderate-to-severe fibrosis (28% ± 7%) in the carvedilol group compared with moderate cardiomyocyte degeneration and moderate-to-severe fibrosis (33% ± 6%) in the metoprolol tartrate group. Apoptosis, as assessed by the terminal deoxynucleotidyl transferase nick end labeling method, was observed in only 1 patient in each group.

Conclusions: Carvedilol treatment of hibernating myocardium results in improved functional recovery after revascularization compared with metoprolol tartrate, and this might partially be related to reduced cardiomyocyte degeneration.

Acetaminophen and Myocardial Stunning after Transient Ischemia in Rabbit Hearts

Background: Myocardial stunning is a lingering contractile dysfunction that occurs after brief ischemia, even in the absence of necrosis. Recent studies have shown that acetaminophen may have some benefit on the return of left ventricular function after brief global ischemia in an in vitro model. This study was conducted to determine whether treatment with acetaminophen results in enhanced myocardial tolerance to transient ischemia-reperfusion by improving left ventricular function and decreasing stunning in an in vivo model.

Methods: Anesthetized, open-chest rabbits were randomized to receive acetaminophen (37 mg/kg, n = 13) or saline (n = 11) 15 minutes before a series of transient coronary artery occlusions followed by reperfusion (three 10-minute periods of ischemia with 5 minutes reperfusion between). Hemodynamics and maximal and minimal values of developed pressure velocity (dP/dt) were measured at baseline, during ischemia, and throughout 2 hours of reperfusion. To assess myocardial stunning, echocardiography was used to determine regional systolic wall thickening fractions and global indices of function such as LV cavity dimensions and ejection fraction.

Results: Hemodynamic variables, including left ventricular systolic pressure and positive and negative dP/dt, were similar in both groups throughout the study. Left ventricular enddiastolic pressure was significantly lower in the acetaminophen group during occlusion and early reperfusion. The repeated short periods of ischemia in the free wall of the heart caused myocardial stunning in both groups. During ischemia, contractile function in the free wall was severely reduced, and although it improved during reperfusion, dysfunction persisted in the postischemic free wall after 2 hours of reflow, recovering to less than 52% of preischemic values ( P < .01). The degree of dysfunction was similar in both groups. During ischemia, the end-diastolic left ventricular cavity area increased from 1.14 ± 0.05 cm2 at baseline to 1.33 ±0.08 cm2 ( P < .05) in controls, but had recovered after 2 hours of reflow. The end-diastolic area in acetaminophen-treated hearts increased from 1.13 ± 0.08 cm2at baseline to 1.35 ± 0.08 cm2 during ischemia and also recovered 2 hours later. No significant differences in LV cavity areas were noted between the groups. Acetaminophen had no effect on changes in ejection fraction, which decreased similarly in both groups during ischemia to approximately 75% of baseline values. Although ejection fraction improved, it remained depressed at the end of reflow in both groups.

Conclusion: Data from this study show that in a rabbit model of myocardial stunning, acetaminophen has a neutral effect on hemodynamics, recovery of fractional thickening, and on indices of global recovery such as left ventricular cavity dimensions or ejection fraction. Thus in the setting of experimental myocardial stunning, treatment with acetaminophen was safe but not cardioprotective.

New perspectives of nitric oxide donors in cardiac arrest and cardiopulmonary resuscitation treatment

Nitric oxide (NO) is often used to treat heart failure accompanied with pulmonary edema. According to present knowledge, however, NO donors are contraindicated when systolic blood pressure is less than 90 mmHg. Based on recent findings and our own clinical experience, we formulated a hypothesis about the new breakthrough complex lifesaving effects of NO donors in patients with cardiac arrest and cardiopulmonary resuscitation therapy. It includes a direct hemodynamic effect of NO donors mediated through vasodilation of coronary arteries in cooperation with improvement of cardiac function and cardiac output through reversible inhibition of mitochondrial complex I and mitochondrial NO synthase, followed by reduction in reactive oxygen species and correction of myocardial stunning. Simultaneously, an increase in vascular sensitivity to sympathetic stimulation could lead to an increase in diastolic blood pressure. Confirmation of this hypothesis in clinical practice would mean a milestone in the treatment for cardiac arrest and cardiopulmonary resuscitation.

Thyroid hormone and the stunned myocardium

Acute critically ill patients experience a rapid decline in plasma free thyroid hormone levels (free triiodothyronine (FT3) and free levothyroxine (FT4)), with a marked elevation of reverse T3, recognized as the euthyroid sick syndrome (ESS) or low-T3 syndrome. The ESS is also often associated with depressed myocardial function, sometimes referred to as the 'stunned myocardium'. Its clinical effects may vary from minimal hemodynamic impairment to cardiogenic shock. Medical management may range from aspirin alone to placement of a left ventricular assist device. With adequate supportive therapy, recovery usually occurs within days or weeks. The effect of T3/T4 therapy has been studied in three conditions in which the ESS and myocardial functional depression have been documented - i) transient regional myocardial ischemia and reperfusion, ii) transient global myocardial ischemia in patients undergoing cardiac surgery on cardiopulmonary bypass, and iii) transient inadequate global myocardial perfusion in brain-dead potential organ donors. Under all three conditions, myocardial ischemia leads to rapid loss of high-energy phosphates, accumulation of myocardial tissue lactate, and probably loss of homeostasis of cytosolic calcium, which may further increase cell injury. There is an inability to generate ATP through the Krebs cycle, which reduces the high-energy phosphate pool essential for all cell ATPases. Under all three conditions, following administration of T3/T4, the myocardial dysfunction was rapidly reversed. We, therefore, cautiously advocate the use of thyroid hormonal therapy to any patient with the ESS and/or a stunned myocardium.

[Clinical research of safflower injection on hibernating myocardial revascularization]

Coronary artery disease (CAD) is one of the leading causes of death. Safflower attracts great attention owing to its anti-ischemia/reperfusion injury effect. Ninety-three patients with CAD were included and randomized into safflower treatment group, PCI group and control group. Low-dose dobutamine stress echocardiography (DSE) was performed to measure end-systolic volume (ESV), end-diastolic volume (EDV), left ventricular ejection fraction (LVEF) and wall motion score index (WMSI) to determine the recovery of hibernating myocardium and cardiac function in all patients before treatment and after 3-month follow-up. The study was to investigate the effects of safflower on hibernating myocardial revascularization and cardiac function. It was found that LVEF was significantly improved, while the ESV and WMSI were significantly reduced after 2-week treatment in safflower and PCI treatment groups. No significant differences were found between safflower and PCI treatment groups in ESV, EDV, WMSI and LVEF after treatment Safflower injection effectively improved hibernating myocardial function.

[Atypical primary symptom in the form of peripheral embolisation after painless myocardial infarction]

We report a case with peripheral embolisation as the primary symptom of a painless myocardial infarction with left ventricular mural thrombosis. The patient was suffering from severe pain in his leg due to arterial occlusion. Subsequent electrocardiography and echocardiography documented severe damage to the left ventricle and a big motile mural thrombosis. A coronary angiography showed subtotal occlusion of the left descending artery. Patients presenting with peripheral thromboembolic episodes should be examined for cardiac cause even in the absence of cardiac symptoms.

Complex I syndrome in myocardial stunning and the effect of adenosine

Isolated rabbit hearts were exposed to ischemia (I; 15 min) and reperfusion (R; 5-30 min) in a model of stunned myocardium. I/R decreased left-ventricle O(2) consumption (46%) and malate-glutamate-supported mitochondrial state 3 respiration (32%). Activity of complex I was 28% lower after I/R. The pattern observed for the decline in complex I activity was also observed for the reduction in mitochondrial nitric oxide synthase (mtNOS) biochemical (28%) and functional (50%) activities, in accordance with the reported physical and functional interactions between complex I and mtNOS. Malate-glutamate-supported state 4 H(2)O(2) production was increased by 78% after I/R. Rabbit heart Mn-SOD concentration in the mitochondrial matrix (7.4±0.7 μM) was not modified by I/R. Mitochondrial phospholipid oxidation products were increased by 42%, whereas protein oxidation was only slightly increased. I/R produced a marked (70%) enhancement in tyrosine nitration of the mitochondrial proteins. Adenosine attenuated postischemic ventricular dysfunction and protected the heart from the declines in O(2) consumption and in complex I and mtNOS activities and from the enhancement of mitochondrial phospholipid oxidation. Rabbit myocardial stunning is associated with a condition of dysfunctional mitochondria named "complex I syndrome." The beneficial effect of adenosine could be attributed to a better regulation of intracellular cardiomyocyte Ca(2+) concentration.

In vivochronic carvedilol treatment in rats attenuatesex vivoregional infarction of the heart

OBJECTIVE

Carvedilol is an alpha-and beta-blocking agent with antioxidant properties. We examined if treatment with carvedilol in vivo protected the heart against ischemic injury ex vivo.

METHODS

Isolated hearts from treated rats (80 mg/kg/day) were subjected to 30 min regional ischemia. Hearts from non-treated animals received either no drug, 10 min carvedilol (1 microM) acute or ischemic preconditioning (IP) by 5 min ischemia +5 min reperfusion prior to regional ischemia. In separate experiments isolated hearts were subjected to 15 min global ischemia and 30 min reperfusion.

RESULTS

Infarct size was significantly reduced by ischemic preconditioning or by chronic carvedilol treatment (9.0+/-0.9% and 7.2+/-1.9% of risk zone infarcted, respectively, vs. 33.8+/-6.4% in control hearts, mean+/-SEM, p < 0.05). Recovery of left ventricular developed pressure after global ischemia was not improved by carvedilol. Post-ischemic rise in left ventricular end diastolic pressure was, however, attenuated by chronic carvedilol treatment.

CONCLUSION

Chronic in vivo but not acute ex vivo pretreatment with carvedilol significantly limited infarct size in isolated rat hearts.

Administration of milrinone before ischemia, in the presence of beta-blockade, to treat metabolic impairment and myocardial stunning in pigs

BACKGROUND

We examined effects of phosphodiesterase type III inhibition on regional myocardial metabolism and global left ventricular function, during ischemia, in the presence of beta-blockade.

METHODS

Twenty-three pigs were randomized and studied to completion in four groups: C, did not receive drugs; M, received 50 microg/kg milrinone; E, received esmolol (150 microg/kg/min); E+M, received both. The left anterior descending artery (LADa) was then occluded for 15 min, followed by a 60-min reperfusion. Left ventricular (LV) function data obtained included LV pressures, cardiac output (CO), slope of end-systolic pressure-volume relationship (Emax), and dP/dT. Blood lactate concentrations were obtained from the aorta, LADa, and vein at baseline, end of occlusion, and during early (5 min) and late (1 h) reperfusion.

RESULTS

During ischemia, occlusion produced significant depression in LV dP/dT, Emax and concomitant elevation of LVEDP that persisted over early reperfusion in groups not treated with milrinone. After ischemia, measurements of CO were higher, with lower LVEDP and SVR; LV dP/dT and the Emax were higher, with lower LVEDP in the E+M group vs. the E group. Ischemic region lactate extraction during ischemia was better with E group vs. C group. Esmolol without or with milrinone was associated with nonsignificant lactate ischemic production during early reperfusion from baseline values.

CONCLUSION

We demonstrated that the pre-emptive administration of milrinone before ischemia was associated with less ischemic hemodynamic effects, without worsening the ischemic metabolic process. The combination E+M diminished ischemic metabolic impairment, and preserved left ventricular function and baseline hemodynamics.

Brain natriuretic peptide reverses the effects of myocardial stunning in rabbit myocardium

We tested the hypothesis that brain natriuretic peptide (BNP) would decrease the effects of myocardial stunning in rabbit hearts. We also examined the mechanisms responsible for these effects. In two groups of anesthetized open-chest rabbits, myocardial stunning was produced by 2 15-min occlusions of the left anterior descending artery separated by 15 min of reperfusion. The treatment group had BNP (10(-3) mol/l) topically applied to the stunned area. Hemodynamic and functional parameters were measured. Coronary flow and O2 extraction were used to determine myocardial O2 consumption. In separate animals, we measured the function of isolated control and simulated ischemia (95% N2/5% CO2, 15 min)-reperfusion ventricular myocytes with BNP or C-type natriuretic peptide (10(-8)-10(-7) mol/l) followed by KT5823 (10(-6) mol/l, cyclic GMP protein kinase inhibitor). In the in vivo control group, baseline delay to contraction was 47+/-4 ms and after stunning it increased to 71+/-10 ms. In the treatment group, baseline delay to contraction was 40+/-7 ms, and after stunning and BNP it did not significantly increase (43+/-6 ms). Neither stunning nor BNP administration affected regional O2 consumption. In control myocytes, BNP (10(-7) mol/l) decreased the percent shortening from 6.7+/-0.4 to 4.5+/-0.2%; after KT5823 administration, the percent shortening increased to 5.4+/-0.5%. In ischemia-reperfusion myocytes, BNP (10(-7) mol/l) decreased the percent shortening less from 5.0+/-0.5 to 3.8+/-0.2%; KT5823 administration did not increase the percent shortening (3.8+/-0.2%). BNP similarly and significantly increased cyclic GMP levels in control and stunned myocytes. The data illustrated that BNP administration reversed the effects of stunning and its mechanism may be independent of the cyclic GMP protein kinase.

A review of levosimendan in the treatment of heart failure

Heart failure is a relatively important public health problem due to its increasing incidence, poor prognosis, and frequent need of re-hospitalization. Intravenous positive inotropic agents play an important role in treating acute decompensation of patients with heart failure due to left ventricular systolic dysfunction. Although frequently used, the inotropic agents β-adrenergic agonists and phosphodiesterase inhibitors seem effective for improving symptoms in the short term; it has been shown that they increase morbidity and mortality by elevating intracellular cyclic adenosine monophosphate (cAMP) and calcium levels. Levosimendan is a new positive inotropic agent having ATP-dependent potassium-channel-opening and calcium-sensitizing effects. In studies on its effects without increasing intracellular calcium concentrations and on its effects that depend on available intracellular calcium levels, it has been shown to have favorable characteristics different from those of current inotropic agents, which exert their effects by increasing calcium concentrations. This study aims to review other important studies about levosimendan by revealing the underlying mechanisms of its activity, efficiency, and safety.

Successful Use of Levosimendan in a Patient During Cardiopulmonary Bypass

Levosimendan (LS) is a novel calcium sensitizer drug that enhances cardiac contractility without increasing myocardial oxygen consumption, and induces vasodilatation. Positive inotropic support is routinely used for weaning from cardiopulmonary bypass circulation in patients with reduced left ventricular function. This case report represents the successful usage of LS for weaning from cardiopulmonary bypass circulation after coronary artery bypass surgery. Levosimendan infusion was started at the sixth hour of cardiopulmonary bypass circulation. There was a dramatic increase in cardiac output 20 minutes after LS infusion, and weaning from cardiopulmonary bypass circulation was achieved. We suggest that LS enhances cardiac performance during and after cardiopulmonary bypass, and can be useful for patients who are unable to be weaned from cardiopulmonary bypass.

Treating metabolic impairment and myocardial stunning with phosphodiesterase inhibitor type III, milrinone, administered prior to coronary artery occlusion in the presence of calcium channel blockade in pigs

This study examined milrinone effects on ischaemic myocardial metabolism and function with calcium blockade. We studied 15 pigs in 3 groups: group C received no drugs; group D received diltiazem 5 mg bolus followed by infusion; group D+M received diltiazem and milrinone (50microg/Kg). The left anterior descending (LAD) artery was then occluded for 15 minutes. Left ventricular (LV) function data obtained included rate, pressures, output, Emax, and dP/dT. Blood lactate was obtained from the LAD and circumflex vessels at baseline, end of occlusion, early (15 min) and late (1 hour) reperfusion. In group D+M, less depression of LV function occurred during ischaemia and early reperfusion. Lactate extraction in the LAD region was less negative in D+M group than in the group without milrinone during ischaemia and late reperfusion. We conclude the preemptive administration of milrinone prior to ischaemia added to calcium blockade improved myocardialfunction and ischaemic metabolic effects.

Use of levosimendan, a new inodilator, for postoperative myocardial stunning in a premature neonate

OBJECTIVE

To first report the successful use of the new inodilator levosimendan in a premature infant with congestive heart failure (CHF) following cardiac surgery. Although the calcium sensitizer levosimendan improves hemodynamics in adults with CHF, no data are available on the use of levosimendan in premature infants with CHF.

DESIGN

Single case report.

SETTING

Twenty-bed postoperative adult and pediatric cardiac intensive care unit.

PATIENT

A 32 wks gestational age, 1525-g premature male twin with transposition of the great arteries.

INTERVENTIONS

The patient underwent arterial switch operation.

MEASUREMENTS AND MAIN RESULTS

Immediately after operation, the patient developed signs of low cardiac output syndrome. Mixed venous saturation was 56%, serum lactate increased to 14.8 mmol/L, systolic arterial pressure was 40 mm Hg, left atrial pressure was 24 mm Hg, and echocardiography showed reduced left ventricular function with a fractional shortening of 10%. There were no signs of reduced coronary perfusion. Milrinone, dobutamine, and epinephrine did not improve hemodynamics. Levosimendan was initiated at a dose of 0.05 mug.kg.min, increased to 0.1 mug.kg.min, and continuously infused for 24 hrs. Within 6 hrs after starting the levosimendan infusion, left atrial pressure decreased to 7 mm Hg and systolic arterial pressure increased to 60 mm Hg; within 24 hrs after initiation serum lactate level normalized to 1.7 mmol/L and mixed venous saturation increased to 81%. Echocardiography revealed improvement of left ventricular function with a fractional shortening of 25%. No side effects were recognized during administration of levosimendan.

CONCLUSIONS

In this premature neonate with postoperative low cardiac output syndrome due to failing myocardial function, levosimendan was a potent inotropic agent.

Pharmacologic treatment of heart failure due to ventricular dysfunction by myocardial stunning: potential role of levosimendan

The treatment of heart failure continues to pose a real challenge for clinicians. This condition is sometimes reversible and therapy should therefore pursue this outcome. In the context of coronary ischemic syndromes, myocardial stunning can cause heart failure and even cardiogenic shock, with important prognostic repercussions. Myocardial stunning is mainly due to calcium overload in the cytosol of myocardial cells, the loss of myofilaments and their reduced sensitivity to calcium. Enhanced immune activation with inflammatory phenomena also plays an important role in the pathophysiology of cardiac dysfunction. Increasing evidence has shown that the myocardial ATP-dependent potassium channel (K(ATP)) plays an important role in many myocardial cell functions and that it is involved in ischemia-reperfusion injury and myocardial stunning. K(ATP) is thus considered a therapeutic target in this setting. Currently used inotropic drugs improve contractility by increasing intracellular concentrations of free calcium, but they increase myocardial consumption of energy and even produce arrhythmia; therefore, in this clinical context, they do not seem to be 'pathophysiologically correct' drugs. Levosimendan, a new calcium-sensitizing agent, increases contractility by enhancing the sensitivity of myofilaments to calcium by binding to the C cardiac troponin in cardiac muscle in a calcium-dependent way. Levosimendan also exerts a coronary and systemic vasodilatory effect through its K(ATP) channel-opening properties and may exert other cardioprotective actions through this mechanism. Levosimendan produces positive hemodynamic effects without increasing myocardial oxygen demand or causing arrhythmias. Intravenous levosimendan is generally well tolerated and has been approved by several European countries, and recently recommended in European Society of Cardiology guidelines, as inotropic therapy for the short-term treatment of acute severe decompensated heart failure in adults. Randomized, double-blind trials have shown that levosimendan is not only more clinically and hemodynamically effective but also that it significantly reduces morbidity and mortality when compared with dobutamine or placebo. Clinical trials addressing the use and efficacy of intravenous levosimendan in acute heart failure in patients with systolic dysfunction or cardiogenic shock due to myocardial stunning are scarce. Beneficial effects on myocardial contractility in patients with myocardial stunning have only been shown in small clinical trials. A positive experience with levosimendan in a small series of patients with cardiogenic shock complicating ST-elevation myocardial infarction suggests that the use of this drug in cardiogenic shock should be further evaluated.

??-Opioid Receptor Antagonism Improves Recovery from Myocardial Stunning in Chronically Instrumented Dogs

We tested the hypothesis that the selective kappa-opioid receptor antagonist nor-binaltorphimine (nor-BNI) improves recovery from myocardial stunning. Ten dogs were chronically instrumented for measurement of heart rate, left atrial, aortic and left ventricular pressure (LVP), and the maximum rate of LVP increase (LV dP/dt(max)) and decrease (LV dP/dt(max)), coronary blood flow velocity and myocardial wall-thickening fraction. Regional myocardial blood flow was determined with fluorescent microspheres. Catecholamine plasma levels were measured by high-performance liquid chromatography, and beta-endorphin and dynorphin plasma levels by radioimmunoassay. An occluder around the left anterior descending artery (LAD) allowed induction of a reversible LAD-ischemia. Animals underwent two experiments in a randomized crossover fashion on separate days: (a) 10 min LAD-occlusion (control experiment), (b) second ischemic episode 24 h after nor-BNI (2.5 mg/kg IV) (intervention). Dogs receiving nor-BNI showed an increase in wall-thickening fraction, LV dP/dt(max) and LV dP/dt(min) before ischemia and during the whole reperfusion (P < 0.05 versus control experiment). After nor-BNI pretreatment, dynorphin levels increased after induction of ischemia to a peak level of 15.1 +/- 3.6 pg/mL (P < 0.05 versus control experiment). The increase in plasma beta-endorphin during ischemia and early reperfusion was attenuated after nor-BNI. Compared with the control experiment, nor-BNI left global hemodynamics, regional myocardial blood flow, and catecholamine levels unchanged. In conclusion, nor-BNI improves recovery from myocardial stunning after regional myocardial ischemia in chronically instrumented dogs.

Dobutamine versus milrinone after subarachnoid hemorrhage

OBJECTIVE

Neurogenic stunned myocardium is a well-recognized complication of subarachnoid hemorrhage. Dobutamine and milrinone are both used for neurogenic stunned myocardium, but there are few data comparing them after subarachnoid hemorrhage.

METHODS

We compared the physiological dose response of dobutamine and milrinone in patients with subarachnoid hemorrhage requiring a pulmonary artery catheter. We located 11 patients who received either inotrope. Physiological data were fitted to a mixed model accounting for drug, dose, and between-patient variation.

RESULTS

There were 11 patients who had 152 pulmonary artery catheter measurements. Two received both inotropes (but not within 4 h of each other), 2 only milrinone, and 7 only dobutamine. The groups had similar clinical and physiological characteristics. After adjustment for vasopressin, milrinone was significantly more potent in increasing cardiac output (P <0.0001) and stroke volume (P=0.03), while decreasing vascular resistance (P <0.0001) and systolic blood pressure (P=0.008), than dobutamine.

CONCLUSION

These data suggest that milrinone and dobutamine should be used in different clinical situations. Milrinone may be more effective in patients with severely depressed systolic function but who have at least normal vascular resistance and blood pressure and in whom raising cardiac output is the primary goal. Dobutamine may be superior when vascular resistance or blood pressure is low.

Effect of Curcuma longa and Ocimum sanctum on myocardial apoptosis in experimentally induced myocardial ischemic-reperfusion injury

Background

In the present investigation, the effect of Curcuma longa (Cl) and Ocimum sanctum (Os) on myocardial apoptosis and cardiac function was studied in an ischemia and reperfusion (I-R) model of myocardial injury.

Methods

Wistar albino rats were divided into four groups and orally fed saline once daily (sham, control IR) or Cl (100 mg/kg; Cl-IR) or Os (75 mg/kg; Os-IR) respectively for 1 month. On the 31^st day, in the rats of the control IR, Cl-IR and Os-IR groups LAD occlusion was undertaken for 45 min, and reperfusion was allowed for 1 h. The hemodynamic parameters{mean arterial pressure (MAP), heart rate (HR), left ventricular end-diastolic pressure (LVEDP), left ventricular peak positive (+) LVdP/dt (rate of pressure development) and negative (-) LVdP/dt (rate of pressure decline)} were monitored at pre-set points throughout the experimental duration and subsequently, the animals were sacrificed for immunohistopathological (Bax, Bcl-2 protein expression & TUNEL positivity) and histopathological studies.

Results

Chronic treatment with Cl significantly reduced TUNEL positivity (p < 0.05), Bax protein (p < 0.001) and upregulated Bcl-2 (p < 0.001) expression in comparison to control IR group. In addition, Cl demonstrated mitigating effects on several myocardial injury induced hemodynamic {(+)LVdP/dt, (-) LVdP/dt & LVEDP} and histopathological perturbations. Chronic Os treatment resulted in modest modulation of the hemodynamic alterations (MAP, LVEDP) but failed to demonstrate any significant antiapoptotic effects and prevent the histopathological alterations as compared to control IR group.

Conclusion

In the present study, significant cardioprotection and functional recovery demonstrated by Cl may be attributed to its anti-apoptotic property. In contrast to Os, Cl may attenuate cell death due to apoptosis and prevent the impairment of cardiac performance.

Levosimendan: a promising treatment for myocardial stunning?

We report a case of a 55-year-old male undergoing major orofacial cancer surgery. A stent to the left anterior descending artery had been implanted for ischaemic heart disease 3 years previously. Twenty-four hours after uneventful anaesthesia and surgery, the patient developed myocardial infarction and cardiogenic shock. Immediate percutaneous transluminal coronary angioplasty, intra aortic balloon counterpulsation, and catecholamine therapy failed to stabilise haemodynamics. In light of successful reperfusion therapy and an only moderate elevation of troponin I, myocardial stunning rather than myonecrosis was considered to be the major contributor to life-threatening left ventricular failure. Therefore, the calcium-sensitising drug levosimendan, which exerts positive inotropic activity without increasing myocardial oxygen demand, was administered as a rescue medication. Within 24 h, levosimendan resulted in decreased filling pressures, reduced left ventricular end-diastolic volume, and augmented systemic pressures. Seven days following surgery, the patient was discharged from the intensive care unit in good clinical condition.

Atrial natriuretic peptide reverses the negative functional effects of stunning in rabbit myocardium

We tested the hypothesis that atrial natriuretic peptide (ANP) would decrease both the effects of myocardial stunning and oxygen consumption in rabbit hearts. In two groups of anesthetized open-chest rabbits, myocardial stunning was produced by two 15 min occlusions of the left anterior descending (LAD) artery separated by 15 min of reperfusion. Either ANP (0.2 mg) or vehicle (lactated Ringers) was then injected into the affected area of the left ventricle. In a third group, ANP was injected into the LAD region of non-stunned rabbits. Hemodynamic (heart rate, aortic and left ventricular pressures) and functional (wall thickening (WT), delay of onset of WT, and rate of WT) parameters were measured. Coronary blood flow (microspheres) and O2 extraction (microspectrophotometry) were used to determine myocardial O2 consumption. Stunning was demonstrated by an increase in the time delay to contraction and depressed WT. In the control group, baseline delay to contraction was 25+/-7 ms, and this increased to 84+/-16 following stunning and vehicle administration. In the ANP group, baseline delay was 20+/-6 at baseline and after stunning and ANP administration it was 30+/-7. Wall thickening decreased by approximately 30% with stunning and vehicle but only 8% in the ANP treated hearts. Stunning did not affect regional O2 consumption (6.0+/-1.1 stunned vs. 7.4+/-1.2 mlO2/min/100g non-stunned). ANP administration did not affect O2 consumption (7.3+/-1.7 stunned vs. 6.4+/-1.0 non-stunned). We therefore concluded that ANP administration reversed the effects of stunning without alteration in local O2 consumption in stunned myocardium.

Effects of inotropic drugs on mechanical function and oxygen balance in postischemic canine myocardium: comparison of dobutamine, epinephrine, amrinone, and calcium chloride

Brief ischemic episodes that induce myocardial and coronary endothelial dysfunction may alter the responses to inotropic drugs. To determine the effects of inotropic drugs in stunned myocardium, the coronary blood flow (CBF), myocardial oxygen consumption (MVO2), and regional mechanical function in response to intracoronary dobutamine, epinephrine, amrinone, and calcium chloride (CaCl2) were measured before (normal) and 30 min after a 15-min-period occlusion of the left anterior descending artery (stunned) in an open-chest canine model. Percent segment shortening (%SS) and post-systolic shortening (%PSS) were determined. Myocardial extraction of oxygen (EO2) and lactate (E(lac)) was calculated. The inotropic drugs increased %SS, CBF, and MVO2 in normal myocardium. Epinephrine and amrinone decreased, while dobutamine and CaCl2 did not affect EO2. The ischemia and reperfusion itself significantly reduced %SS and E(lac), and increased %PSS. In stunned myocardium, the responses to inotropic drugs were not significantly altered, except that they progressively reduced %PSS and epinephrine did not affect EO2. These findings indicate that a brief episode of ischemia does not affect the mechanical and metabolic coronary flow responses to inotropic drugs, although it abolishes direct vasodilator responses to epinephrine.

The p38 MAPK inhibitor SB203580 blocks adenosine A(1) receptor-induced attenuation of in vivo myocardial stunning

There is considerable evidence implicating a key role for p38 mitogen-activated protein kinase (MAPK) in ischemic and pharmacological preconditioning against myocardial infarction. However, there have been few, if any, studies examining the role of p38 MAPK in the protection of stunned myocardium. The purpose of this study was to determine whether p38 MAPK plays a role in the adenosine A(1) receptor anti-stunning effect in in vivo porcine myocardium. Regional myocardial stunning in anesthetized, open-chest pigs was induced by 15 min of left anterior descending coronary artery (LAD) occlusion and 3 h of reperfusion (RP). Animals were treated with either vehicle (n = 5), AMP579 (70 microg/kg i.v.; 25 microg/kg bolus + 1.5 microg/kg/min for 30 min prior to ischemia, n = 5), the p38 MAPK inhibitor SB203580 (0.25 mg/kg i.v. bolus, n = 4) or a combination of SB203580 plus AMP579 (n = 5). Regional ventricular function was monitored by measurements of segment shortening and load insensitive parameters including preload recruitable stroke work (PRSW) and PRSW area (PRSWA). The ischemic area at risk was similar in all groups and there was no necrosis in any heart. Treatment with AMP579 significantly improved reperfusion regional PRSW and PRSWA compared to vehicle controls. The p38 inhibitor SB203580 alone did not alter the extent of myocardial stunning, but it abolished the beneficial effect of AMP579 pretreatment. These results provide the first evidence that p38 MAPK activation may play an important role in the mechanism by which adenosine agonists attenuate myocardial stunning.

Cardioprotective effects of KB-R7943, a novel inhibitor of Na+/Ca2+ exchanger, on stunned myocardium in anesthetized dogs

PURPOSE

The present study was carried out to determine the cardioprotective effects of KB-R7943 (KBR), a selective inhibitor of the reverse mode of Na+/Ca2+ exchanger (NCX), on stunned myocardium in anesthetized dogs.

METHODS

The dogs were allocated to one of three groups (n = 7 for each group), and received drug vehicle (group C), low-dose KBR (5 mg x kg(-1) i.v.) (group L) or high-dose KBR (10 mg x kg(-1) i.v.) (group H) at 15 min before left anterior descending coronary artery (LAD) occlusion. Stunned myocardium was produced by 15-min occlusion of LAD and 90-min reperfusion in all dogs. Regional myocardial contractility was evaluated with segment shortening (%SS).

RESULTS

Recovery of %SS at 90 min after reperfusion was significantly improved in group H (70.8% +/- 3.9% of baseline), whereas the recovery was poor in groups C and L (34.3% +/- 2.8% and 36.4% +/- 5.4% of baseline, respectively). Regional myocardial blood flow showed no significant difference among groups. KBR had no effect on coronary or systemic hemodynamics.

CONCLUSION

The results show that preischemic administration of high-dose KBR markedly improves myocardial contractile dysfunction after ischemia-reperfusion in anesthetized dogs, indicating that KBR protects myocardium against the ischemia-reperfusion injury in vivo.

Cardioprotective effects of Ilex paraguariensis extract: evidence for a nitric oxide-dependent mechanism

AIM

To examine the effects of an Ilex paraguariensis (Ip) extract on postischemic alterations derived from 20 min of global ischemia and 30 min of reperfusion.

METHODS

Isolated rat hearts were treated 10 min before ischemia and the first 10 min of reperfusion with Ip 30 microg/ml. In other hearts, chelerythrine (1 microM), a protein kinase C blocker, or l(G)-nitro l-arginine methyl ester (l-NAME), a nitric oxide synthase inhibitor, were administered prior to Ip infusion. Left ventricular developed pressure (LVDP), +dP/dt(max), -dP/dt(max), and left ventricular end diastolic pressure (LVEDP) were used to assess myocardial function. Thiobarbituric acid reactive substances (TBARS) were measured.

RESULTS

Ip treatment produced an improvement of postichemic recovery (LVDP=96+/-8%; +dP/dt(max)=95+/-10%; -dP/dt(max)=90+/-12% vs. 57+/-6%, 53+/-6% and 57+/-8%, respectively, in untreated hearts) and an attenuation of the increase of LVEDP and TBARS content. Chelerythrine did not modify and l-NAME abolished the protection induced by Ip.

CONCLUSIONS

These data are the first demonstration that Ip extract attenuates the myocardial dysfunction provoked by ischemia and reperfusion and that this cardioprotection involves a diminution of oxidative damage through a nitric oxide-dependent mechanism.

Effect of levosimendan on balance between ATP production and consumption in isolated perfused guinea-pig heart before ischemia or after reperfusion

Levosimendan is a novel drug developed for treatment of decompensated heart failure. Levosimendan is a calcium sensitizer that increases contractile force of the myocardium by enhancing the sensitivity of myofilaments to calcium without increasing intracellular calcium concentration. The present study was carried out to investigate whether levosimendan induces any changes in the phosphorylation potential (ie, the balance between ATP production and consumption) in the normal heart and in the post-ischemic heart while exerting its positive inotropic effect. We show that 0.1 microM levosimendan increased the left ventricle developed pressure in the pre-ischemic and in the post ischemic hearts by 16 and 18% respectively, and the +dP/dt by 16 and 19%, respectively. At that concentration levosimendan did not cause any effect on the phosphorylation potential (1 x 10(5) M(-1) and 0.2 x 10(5) M(-1) in the pre-ischemic and post-ischemic heart, respectively) as assessed by P-NMR, although an increased beating rate (13%) and oxygen consumption (10%) was observed when adding the drug post-ischemically. Our findings are consistent with the results of a recent clinical trial (RUSSLAN), which showed that levosimendan does not induce ischemia and reduces the risk of worsening heart failure and death, in patients with left ventricular failure complicating acute myocardial infarction.

[Usefulness of trimetazidine in ischemia-reperfusion lesion. Experimental study in myocardial stunning model]

OBJECTIVE

The aim of this study is to evaluate the effect of trimetazidine (TMZ) on myocardial systolic dysfunction resulting from an isolated episode of induced coronary ischemia.

METHODS

In a double-blinded randomized design we studied 13 mongrel anesthetized dogs of either sex (6 of them treated with oral TMZ previously). The anterior descending coronary artery was totally occluded during 15 minutes followed by 60 minutes of reperfusion. Global and regional cardiac variables were recorded in control and ischemic areas.

RESULTS

There were no significant differences between TMZ and placebo series with respect to global cardiac function variables. Both series showed no significant variations in global variables during the ischemia-reperfusion process. The shortening fraction in the ischemic area fell significantly during the ischemic period in both TMZ and placebo series reaching dyskinetic values. Myocardial contractility dysfunction persisted after 60 minutes of reperfusion in both series with no significant differences (41% vs 50% placebo).

CONCLUSIONS

Contrary to shorter and repeated occlusion periods, myocardial contractility recovery after a complete episode of ischemia did not show significant differences between TMZ-treated and placebo series.

Xenon Improves Recovery from Myocardial Stunning in Chronically Instrumented Dogs

In this study we tested the hypothesis that inhalational administration of xenon improves recovery from myocardial stunning. Ten dogs were chronically instrumented for measurement of heart rate; left atrial, aortic, and left ventricular pressure; coronary blood-flow velocity; and myocardial wall-thickening fraction. Regional myocardial blood flow was determined with fluorescent microspheres. Catecholamine plasma levels were measured by high-performance liquid chromatography. An occluder around the left anterior descending artery (LAD) allowed the induction of a reversible LAD ischemia. Animals underwent 2 experimental conditions in a randomized crossover fashion on separate days: (a) 10 min of LAD occlusion under fentanyl (25 microg. kg(-1). h(-1)) and midazolam (0.6 mg. kg(-1). h(-1)) (control) and (b) a second ischemic episode under the same basal anesthesia with concomitant inhalational administration of 75 +/- 1 vol% xenon (intervention). Anesthesia was induced 35 min before LAD occlusion and was discontinued after 20 min of reperfusion. Dogs receiving xenon showed a significantly better recovery of wall-thickening fraction up to 12 h after ischemia. The increase in plasma epinephrine during emergence from anesthesia and in the early reperfusion period was significantly attenuated in the xenon group. There were no differences between groups concerning global hemodynamics, blood-flow velocity, or regional myocardial blood flow. In conclusion, inhalational administration of 75 vol% xenon improves recovery from myocardial stunning in chronically instrumented dogs under fentanyl/midazolam anesthesia.

Adenosine A1/A2a receptor agonist AMP-579 induces acute and delayed preconditioning against in vivo myocardial stunning

The purpose of this study was to determine whether the adenosine A1/A2a receptor agonist AMP-579 induces acute and delayed preconditioning against in vivo myocardial stunning. Regional stunning was produced by 15 min of coronary artery occlusion and 3 h of reperfusion (RP) in anesthetized open-chest pigs. In acute protection studies, animals were pretreated with saline, low-dose AMP-579 (15 microg/kg iv bolus 10 min before ischemia), or high-dose AMP-579 (50 microg/kg iv at 14 microg/kg bolus + 1.2 microg.kg(-1).min(-1) for 30 min before coronary occlusion). The delayed preconditioning effects of AMP-579 were evaluated 24 h after administration of saline vehicle or high-dose AMP-579 (50 microg/kg iv). Load-insensitive contractility was assessed by measuring regional preload recruitable stroke work (PRSW) and PRSW area. Acute preconditioning with AMP-579 dose dependently improved regional PRSW: 129 +/- 5 and 100 +/- 2% in high- and low-dose AMP-579 groups, respectively, and 78 +/- 5% in the control group at 3 h of RP. Administration of the adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (0.7 mg/kg) blocked the acute protective effect of high-dose AMP-579, indicating that these effects are mediated through A1 receptor activation. Delayed preconditioning with AMP-579 significantly increased recovery of PRSW area: 64 +/- 5 vs. 33 +/- 5% in control at 3 h of RP. In isolated perfused rat heart studies, kinetics of the onset and washout of AMP-579 A1 and A2a receptor-mediated effects were distinct compared with those of other adenosine receptor agonists. The unique nature of the adenosine agonist AMP-579 may play a role in its ability to induce delayed preconditioning against in vivo myocardial stunning.

Levosimendan in Kardiologie und Intensivmedizin

Levosimendan (LS) is a new calcium sensitizer that exerts positive inotropic effects without increasing intracellular cAMP or Ca2+ at therapeutic doses and therefore may avoid major limitations of beta-adrenergic agents. LS also causes arteriolar and venous dilation by opening potassium channels on vascular smooth muscle cells. In addition, LS does not increase myocardial oxygen demand and may exert anti-stunning effects. LS itself has a short elimination half life but has shown to have active metabolites with elimination half lives up to 80 hours. Three hemodynamic studies show that at recommended doses LS increases cardiac output by 8-30% and reduces pulmonary capillary wedge pressure by 11-28% in heart failure patients. Systemic vascular resistance falls significantly and blood pressure tends to decline. The hemodynamic effects are not attenuated by concomitant beta-blocker medication. Two large randomized studies on patients with chronic and acute congestive heart failure found a decrease in mortality with LS. In the LIDO trial there was a 52.9% survival benefit at day 31 when compared with patients receiving dobutamine. In the RUSSLAN trial, the survival benefit approached 40% at day 14 after start of treatment compared to placebo. Experience in the ICU setting is limited but LS therapy in postoperative low output failure and cardiogenic shock seems to be feasible and LS is a promising agent in the inotropic armamentarium. LS has a favourable side effect profile and is approved for 24-hour use in congestive heart failure. It may cause hypotension due to vasodilation, and this effect may be aggravated by inadequate preload conditions. Further morbidity and mortality studies are required to confirm the encouraging data from the LIDO and RUSSLAN trial but already the existing data support LS as the inotropic agent of choice in patients with worsening heart failure and a systolic arterial blood pressure beyond 90 mmHg.

Protection from myocardial stunning by ischaemia and hypoxia with the adenosine A3 receptor agonist, IB-MECA

Guinea pig isolated working hearts were exposed to 30-min ischaemia by reducing coronary flow to 10%, followed by reperfusion. Aortic output fell to 4.5+/-4.5% of the pre-ischaemic value at reperfusion, recovering to 48.2+/-14.6% at 20-min post-reperfusion; the index of myocardial stunning. IB-MECA (N(6)-(3-iodobenzyl)adenosine-5'-N-methyluronamide, 3 x 10(-7) M), infused from 10 min into ischaemia, did not affect recovery of aortic output 20 min after reperfusion (41.9+/-1.9%). IB-MECA infused at reperfusion, however, significantly protected against stunning, aortic output recovering to 79.6+/-3.9% at 20-min post-reperfusion. Hypoxic gassing (5% CO(2) in nitrogen, 30 min) of guinea pig isolated paced left atria and papillary muscles reduced the developed tension, recovering to 75% 5 min after re-oxygenation. This myocardial stunning was unaffected by IB-MECA (3 x 10(-7) M) added 10 min into hypoxia. IB-MECA added at reoxygenation significantly improved recovery, which was prevented by the adenosine A(3) receptor antagonist, 1-propyl-3-(3-iodo-4-aminobenzyl)-8-(4-oxyacetate)phenylxanthine (I-ABOPX, 1 x 10(-5) M). Thus, stimulation of adenosine A(3) receptors at reperfusion/reoxygenation in guinea pig cardiac preparations protects against myocardial stunning.

Effect of aspirin on late preconditioning against myocardial stunning in conscious rabbits

OBJECTIVES

The goal of this study was to investigate the effect of three different doses of acetylsalicylic acid (aspirin) (ASA) on the late phase of ischemic preconditioning (PC) against myocardial stunning.

BACKGROUND

Although recent evidence indicates that the late phase of ischemic PC is mediated by cyclooxygenase-2 (COX-2), the effect of nonsteroidal anti-inflammatory drugs (NSAIDs) that inhibit COX-2 activity on late PC has not been evaluated; ASA is the most widely used NSAID. Therefore, we determined whether ASA impedes the development of late PC.

METHODS

Conscious rabbits underwent a protocol consisting of three days of six 4-min coronary occlusion/4-min reperfusion cycles.

RESULTS

Neither 5 mg/kg nor 10 mg/kg x 3 of ASA interfered with the protective effects of late PC against stunning. In contrast, the late PC effect was completely abrogated by 25 mg/kg of ASA. Low-dose (5 mg/kg) ASA effectively inhibited platelet aggregation but did not prevent the increase in COX-2 activity, whereas the highest dose (25 mg/kg) completely blocked COX-2 activity.

CONCLUSIONS

The administration of ASA either at antithrombotic doses (5 mg/kg), which are widely used to prevent cardiovascular events in patients, or at analgesic/antipyretic doses (10 mg/kg) does not interfere with the cardioprotective effects of late PC against myocardial stunning. In contrast, high doses of ASA (25 mg/kg), which are used as antirheumatic therapy, abrogate both COX-2 activity and late PC, suggesting 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.

Acetoacetate augments beta-adrenergic inotropism of stunned myocardium by an antioxidant mechanism

Blunted beta-adrenergic inotropism in stunned myocardium is restored by pharmacological (N-acetylcysteine) and metabolic (pyruvate) antioxidants. The ketone body acetoacetate is a natural myocardial fuel and antioxidant that improves contractile function of prooxidant-injured myocardium. The impact of acetoacetate on postischemic cardiac function and beta-adrenergic signaling has never been reported. To test the hypothesis that acetoacetate restores contractile performance and beta-adrenergic inotropism of stunned myocardium, postischemic Krebs-Henseleit-perfused guinea pig hearts were treated with 5 mM acetoacetate and/or 2 nM isoproterenol at 15-45 and 30-45 min of reperfusion, respectively, while cardiac power was monitored. The myocardium was snap frozen, and its energy state was assessed from phosphocreatine phosphorylation potential. Antioxidant defenses were assessed from GSH/GSSG and NADPH/NADP(+) redox potentials. Stunning lowered cardiac power and GSH redox potential by 90 and 70%, respectively. Given separately, acetoacetate and isoproterenol each increased power and GSH redox potential three- to fivefold. Phosphocreatine potential was 70% higher in acetoacetate- vs. isoproterenol-treated hearts (P < 0.01). In combination, acetoacetate and isoproterenol synergistically increased power and GSH redox potential 16- and 7-fold, respectively, doubled NADPH redox potential, and increased cAMP content 30%. The combination increased cardiac power four- to sixfold vs. the individual treatments without a coincident increase in phosphorylation potential. Potentiation of isoproterenol's inotropic actions endured even after acetoacetate was discontinued and GSH potential waned, indicating that temporary enhancement of redox potential persistently restored beta-adrenergic mechanisms. Thus acetoacetate increased contractile performance and potentiated beta-adrenergic inotropism in stunned myocardium without increasing energy reserves, suggesting its antioxidant character is central to its beneficial actions.

Hibernation and congestive heart failure

The most common cause of heart failure is coronary artery disease, and whilst intensive treatment of acute coronary syndromes and myocardial infarction continue to reduce the mortality associated with these conditions, many survivors develop heart failure. In general, heart failure secondary to ischaemic heart disease results from: (i) irreversible myocyte loss due to infarction with scar formation; (ii) chronic left ventricular dysfunction which may recover after revascularisation (hibernating myocardium); (iii) changes in remote myocardium (adverse remodelling). A number of studies suggest that patients with post-ischaemic heart failure may derive symptomatic and prognostic benefit from coronary revascularisation and most of this benefit is thought to derive from functional improvement of hibernating myocardium. Although the mechanisms of hibernation remain poorly understood, studies with positron emission tomography have shown that blood flow to hibernating myocardium is usually within or only slightly below the normal range whilst the coronary vasodilator reserve is always severely reduced and the concept that stunning and hibernation may be causally related has gained support in recent years. There is increasing consensus amongst clinicians regarding the importance of identifying and treating hibernating myocardium in patients with coronary artery disease and heart failure, and a randomised study comparing optimum medical treatment to optimum medical treatment with complete revascularisation has just commenced in the United Kingdom (HEART-UK) and will provide guidance regarding diagnosis and treatment of these patients.

Increases in myocardial cyclic GMP attenuate contractile delay in myocardial stunning

We tested the hypothesis that the effects of myocardial stunning would be reduced by cyclic GMP in rabbit hearts. In three groups of anesthetized open-chest New Zealand white rabbits, myocardial stunning was produced by 15 min of occlusion of the left anterior descending coronary artery followed by 15 min of reperfusion repeated twice. Either control vehicle (saline plus 1% dimethyl sulfoxide) or 8-bromo-cyclic GMP (8-Br-cGMP (10(-4) and 10(-3) M)) was topically applied to the left ventricular surface. Hemodynamic (left ventricular and aortic pressures) and functional parameters (wall thickening, delay in onset of wall thickening, and rate of wall thickening) were determined. Coronary blood flow (microspheres) and O2 extraction (microspectrophotometry) were used to determine myocardial O2 consumption (VO2). Myocardial stunning was observed in the control group through an increased delay in onset of myocardial wall thickening (29 +/- 7 versus 55 +/- 16 ms) and decreased maximal rate of wall thickening (20 +/- 8 versus 11 +/- 3 mm x s(-1)). After treatment with 8-Br-cGMP 10(-4) and 10(-3) M, stunning did not increase the delay (37 +/- 5 versus 39 +/- 7 and 39 +/- 7 versus 28 +/- 8 ms). Myocardial stunning did not significantly alter VO2. 8-Br-cGMP 10(-3) M significantly decreased subepicardial VO2 (6.2 +/- 0.8 versus 3.7 +/- 0.6 mL O2 x min(-1) 100 g(-1)) and insignificantly decreased subendocardial VO2 (8.6 +/- 0.9 versus 6.3 +/- 1.2 mL O2 x min(-1) x 100 g(-1)) when compared with the vehicle-treated rabbits. We conclude that increasing cyclic GMP reduced the effects of myocardial stunning in the rabbit heart by ameliorating the delay in onset of wall thickening and decreasing the local O2 costs in the stunned region.

Cardioprotective effect of diazoxide is mediated by activation of sarcolemmal but not mitochondrial ATP-sensitive potassium channels in mice

BACKGROUND

We recently demonstrated that the sarcolemmal ATP-sensitive potassium (sarcK(ATP)) channel plays a key role in cardioprotection against ischemia/reperfusion injuries in Kir6.2-knockout (KO) mice. In the present study, we evaluated the effects of diazoxide, a mitochondrial ATP-sensitive potassium (mitoK(ATP)) channel opener, on ischemia-induced myocardial stunning in sarcK(ATP) channel-deficient mice.

METHODS AND RESULTS

Langendorff-perfused hearts of wild-type (WT) and KO mice were subjected to global ischemia/reperfusion. Diazoxide improved the recovery of contractile function in WT hearts but not in KO hearts. Treatment with HMR1098 (a sarcK(ATP) channel blocker) but not 5-hydroxydecanoate (a mitoK(ATP) channel blocker) abolished the cardioprotective effect of diazoxide in WT hearts. In coronary-perfused WT ventricular muscle preparations, action potential shortening during ischemia was accelerated in the presence of diazoxide.

CONCLUSIONS

Diazoxide enhances action potential shortening during ischemia by activating sarcK(ATP) channels and provides cardioprotection in mouse hearts.

Ginkgo biloba extract EGb 761 attenuates myocardial stunning in the pig heart

Myocardial stunning, a transient contractile dysfunction that appears following a brief period of ischemia, is at least partly due to the production of oxygen-derived free radicals. The objective of the present study was to determine whether the Ginkgo biloba extract EGb761, which has antioxidant properties in vitro, can attenuate myocardial stunning in vivo. Forty-seven anesthetized open-chest farm pigs underwent 10 min of occlusion of the left anterior descending coronary artery (LAD), followed by 3 hours of reperfusion. They were pretreated with either physiological saline, 100 mg or 300 mg of EGb 761 (Protocol I) or 3 mg or 9 mg of ginkgolide B (GkB) (Protocol II). Contractile function was assessed by sonomicrometry. Both doses of EGb 761 significantly improved recovery of contractile function in the reperfused myocardium with segment shortening averaging 23 +/- 5 % of baseline values at 3 hours post-reflow in controls versus 81 +/- 10 % and 57 +/- 12 % in the EGb100 and EGb300 groups, respectively (p < 0.05 vs control in both cases). In contrast, neither dose of GkB improved functional recovery during reperfusion. ESR experiments revealed that EGb761 resulted in a 59 % decrease in myocardial spin-adduct release during reperfusion (p < 0.05 versus control and GkB groups). A significant 28 % decrease (p < 0.05 vs control group) was also obtained in GkB-treated animals. These results indicate that EGb 761 can attenuate myocardial stunning following a brief ischemic insult in the in situ pig heart by an effect that involves a decrease in the formation of free radicals. As the effect of EGb 761 on functional recovery cannot be explained by the presence of GkB, the beneficial action of the extract on myocardial stunning likely involves complementary effects of both its non-ginkgolide and ginkgolide constituents.

Delta-opioid receptor-induced late preconditioning is mediated by cyclooxygenase-2 in conscious rabbits

Although activation of delta-opioid receptors is known to induce both early and late preconditioning (PC) against myocardial infarction, the mechanisms for this salubrious effect are unclear. Furthermore, it is unknown whether delta-opioid receptors can also induce late PC against myocardial stunning. By using conscious rabbits (n = 120) in this study, we found that the delta-opioid receptor agonist (+/-)-4-[(alpha-R*)-alpha-[(2S*,5R*)-4-allyl-2,5-dimethyl-1-piperazinyl]-3-hydroxybenzyl]-N,N-diethylbenzamide (BW-373U86) induced late PC against myocardial stunning 24 h after treatment and that this effect was abolished by the selective cyclooxygenase-2 (COX-2) inhibitors N-[2-(cyclohexyloxy)4-nitrophenyl]methanesulfonamide (NS-398) and celecoxib. This protective effect was also abrogated by the selective delta(1)-opioid receptor antagonist 7-benzylidenenaltrexone, indicating that the delta(1)-opioid receptor is necessary for BW-373U86-induced late PC. BW-373U86 did not induce early PC against stunning. In addition, BW-373U86 induced late PC against infarction, which was blocked by NS-398. At 24 h after BW-373U86 administration, myocardial COX-2 protein expression and PGE(2) and 6-keto-PGF(1alpha) levels were significantly increased. These results demonstrate that activation of delta-opioid receptors induces late PC against both stunning and infarction via a COX-2-dependent mechanism.

Reversal of atrial mechanical stunning after cardioversion of atrial arrhythmias: implications for the mechanisms of tachycardia-mediated atrial cardiomyopathy

BACKGROUND

Atrial mechanical stunning develops on termination of chronic atrial arrhythmias and is implicated in the genesis of thromboembolic complications after cardioversion. The mechanisms responsible for atrial mechanical stunning are unknown. The effects of atrial rate, isoproterenol, and calcium on atrial mechanical function in patients with atrial stunning have not been evaluated, and it is not known if atrial stunning can be reversed.

METHODS AND RESULTS

Thirty-five patients with chronic atrial flutter (AFL) undergoing radiofrequency ablation were studied. Fifteen patients in sinus rhythm undergoing ablation for paroxysmal AFL were studied as control for effects of the procedure. Left atrial appendage emptying velocities (LAAEVs) and spontaneous echocardiographic contrast (LASEC) were assessed by transesophageal echocardiography during AFL, after reversion to sinus rhythm, during atrial pacing at cycle lengths of 750 to 250 ms, after a postpacing pause, and with isoproterenol or calcium. With termination of AFL, LAAEV decreased from 59.0+/-3.7 cm/s to 18.8+/-1.4 cm/s (P<0.0001) and LASEC grade increased from 0.9+/-0.1 to 2.2+/-0.2 (P<0.0001). Pacing increased LAAEV to a maximum of 38.4+/-3.2 cm/s (P<0.0001) and reduced LASEC grade to 1.9+/-0.2 (P=0.005). Isoproterenol and calcium reversed atrial mechanical stunning with LAAEV increasing to 89.3+/-12.6 cm/s (P=0.0007) and 50.2+/-10.5 cm/s (P=0.005), respectively, and LASEC grade decreasing to 0.2+/-0.1 (P=0.001) and 1.4+/-0.2 (P=0.01), respectively. The postpacing pause increased LAAEV to 69.3+/-3.7 cm/s (P<0.0001). No change in LAAEV was observed in the paroxysmal AFL group.

CONCLUSION

Atrial mechanical stunning can be reversed by pacing at increased rates and through the administration of isoproterenol or calcium. These findings suggest a functional contractile apparatus in the mechanically remodeled atrium as a result of chronic atrial flutter.

Transient atrial mechanical dysfunction (stunning) after cardioversion of atrial fibrillation and flutter

BACKGROUND

Conversion of atrial fibrillation (AFib) and flutter (AFlt) to sinus rhythm results in a transient mechanical dysfunction of atria (atrial stunning). Methods used as a means of assessing atrial stunning, atrial stunning after conversion of atrial fibrillation/flutter, and the cause, mechanisms, determinants of the extent, and drugs affecting atrial stunning were examined.

METHODS

Studies on the subject, identified through a comprehensive literature search, were thoroughly evaluated.

RESULTS AND CONCLUSIONS

Left atrial (LA) stunning has been reported with all modes of conversion of AFib/AFlt to sinus rhythm. The incidence of LA stunning is 38% to 80%. Spontaneous echocardiographic contrast, LA appendage (LAA) flow velocities and emptying fraction, transmitral inflow velocity of atrial wave (A-wave), time-velocity integral of A-wave, and atrial filling fraction have been used as means of assessing LA stunning. The data on right atrial (RA) stunning are limited, but parallel findings have been reported in the right atrium. Atrial stunning does not develop after the unsuccessful attempts of cardioversion or on delivery of electric current to the heart without AFib/AFlt, and it is a function of the underlying AFib/AFlt manifesting at the restoration of sinus rhythm. Tachycardia-induced atrial myopathy and chronic atrial hibernation are suggested mechanisms. Duration of preceding AFib/AFlt, atrial size, and underlying heart disease are determinants of the extent of atrial stunning. Verapamil, dofetilide, and acetylstrophenathidine have been shown to attenuate or protect from atrial stunning in animal or small human studies. A comprehensive knowledge of atrial stunning would be helpful in selecting the patients for, and the duration of, anticoagulation therapy after cardioversion.

[Viable myocardium: comparative evaluation of surgical and pharmacological treatment of patients with ischemic heart disease, post-infarct cardiosclerosis and chronic cardiac failure]

AIM

To compare surgical and drug therapies of viable myocardium in IHD patients with left ventricular dysfunction (LVD), to show how to choose between them basing on the presence or absence of viable myocardium in the dyssenergy zones in such patients.

MATERIAL AND METHODS

The study enrolled 55 IHD patients with postinfarction cardiosclerosis, left ventricular ejection fraction under 35%, circulatory disorder class I-III (NYHA classification). Coronary artery bypass operation (CABO) was made in 24 patients, 31 patients received drugs. The examination included dobutamin echo-CG, perfusion myocardial scintigraphy. Viability of the myocardium was assessed before and 6 months after the treatment.

RESULTS

The patients were divided by the treatment and number of segments of viable myocardium: group 1--patients with viable myocardium subjected to CABO, group 2--patients with non-viable myocardium subjected to CABO, group 3--patients with viable myocardium treated with drugs, group 4--patients with non-viable myocardium treated with drugs. The greatest rise in LV EF, reduction of the end diastolic volume, end systolic volume of the left ventricle and functional class was observed in group 1. In group 2 these parameters changed less than in group 3. Patients of groups 2 and 4 were similar by parameters of LV global contractility.

CONCLUSION

Improvement of central hemodynamics and functional class was the greatest in IHD patients after CABO having viable myocardium. If myocardium is not viable surgical treatment has no advantage over conservative in improvement of the pump cardiac function and is inferior to pharmacological treatment in effect on myocardium function in patients with viable myocardium in dyssynergia zones.