Evidence for stunned myocardium in humans: a 2001 update

Predictors of diastolic deceleration time of coronary flow velocity of infarct related and reference coronary artery assessed by transthoracic Doppler echocardiography in the chronic phase of successfully reperfused anterior myocardial infarction: relation to infarct size

Introduction

High-frequency transthoracic Doppler echocardiography (TDE) enables the assessment of flow velocity and velocity pattern in different coronary arteries, including the assessment of diastolic deceleration time (DDT) of coronary flow velocity. Short DDT of infarct related artery (IRA) (<600 msec) in the acute phase of anterior myocardial infarction (MI) is the predictor of adverse left ventricular (LV) remodeling and prognosis. The significance of DDT of coronary flow velocity assessment in the chronic phase of anterior MI is not well established. Our study aimed to establish the predictors of DDT of the coronary flow velocity of infarct related (left anterior descendent-DDT of LAD) and reference coronary artery, evaluated by TDE, and to assess their relation to infarct size in the chronic phase of successfully reperfused first anterior MI.

Methods

Our study included 40 consecutive patients (34 men, mean age 52 ± 12 years) one month after the first anterior STEMI and single vessel disease successfully treated with primary PCI. All patients underwent SPECT MPI for the assessment of LV volumes, ejection fraction, and percentage of the myocardium with fixed perfusion abnormalities and echocardiographic examination including the evaluation of DDT of IRA and reference coronary artery TDE.

Results

DDT of LAD correlated significantly to the WMSI (r = -0.467, p = 0.002), LV end-systolic volume (r = -0.412, p = 0.008), LV ejection fraction (r = 0.427, p = 0.006), while the strongest correlation was observed between DDT of LAD and the extent of fixed perfusion abnormality (r = -0.627, p < 0.0001), Multivariate analysis revealed percentage of fixed perfusion abnormalities along with DDT of reference coronary artery as the independent predictors of DDT of IRA. DDT of IRA shorter than 886 msec predicts large fixed perfusion abnormalities (>20%) with a sensitivity of 89% and specificity of 62% (AUC 0.842).

Conclusion

DDT of LAD assessed by TDE in the chronic phase of successfully reperfused first anterior MI is a usefull variable for the assessment of microcirculatory function that exclusively reflects the extent of microvascular damage and relates to infarct size.

Attentional influences on neural processing of biological motion in typically developing children and those on the autism spectrum

BACKGROUND

Biological motion imparts rich information related to the movement, actions, intentions and affective state of others, which can provide foundational support for various aspects of social cognition and behavior. Given that atypical social communication and cognition are hallmark symptoms of autism spectrum disorder (ASD), many have theorized that a potential source of this deficit may lie in dysfunctional neural mechanisms of biological motion processing. Synthesis of existing literature provides some support for biological motion processing deficits in autism spectrum disorder, although high study heterogeneity and inconsistent findings complicate interpretation. Here, we attempted to reconcile some of this residual controversy by investigating a possible modulating role for attention in biological motion processing in ASD.

METHODS

We employed high-density electroencephalographic recordings while participants observed point-light displays of upright, inverted and scrambled biological motion under two task conditions to explore spatiotemporal dynamics of intentional and unintentional biological motion processing in children and adolescents with ASD (n = 27), comparing them to a control cohort of neurotypical (NT) participants (n = 35).

RESULTS

Behaviorally, ASD participants were able to discriminate biological motion with similar accuracy to NT controls. However, electrophysiologic investigation revealed reduced automatic selective processing of upright biologic versus scrambled motion stimuli in ASD relative to NT individuals, which was ameliorated when task demands required explicit attention to biological motion. Additionally, we observed distinctive patterns of covariance between visual potentials evoked by biological motion and functional social ability, such that Vineland Adaptive Behavior Scale-Socialization domain scores were differentially associated with biological motion processing in the N1 period in the ASD but not the NT group.

LIMITATIONS

The cross-sectional design of this study does not allow us to definitively answer the question of whether developmental differences in attention to biological motion cause disruption in social communication, and the sample was limited to children with average or above cognitive ability.

CONCLUSIONS

Together, these data suggest that individuals with ASD are able to discriminate, with explicit attention, biological from non-biological motion but demonstrate diminished automatic neural specificity for biological motion processing, which may have cascading implications for the development of higher-order social cognition.

No evidence of cardiac stunning or decoupling immediately after cardiopulmonary bypass for elective coronary surgery

BACKGROUND

There is significant uncertainty regarding the timing of onset of cardiovascular stunning after cardiac surgery. Cardiovascular stunning is affecting both contractility (Ees) and arterial load. Arterial load may be represented by arterial elastance (Ea) and participates in ventriculo-arterial coupling through the Ea/Ees ratio, giving information on efficiency and performance. An alternative approach to ventriculo-arterial interaction is oscillatory power fraction (OPF). The aim of this study was to investigate the immediate beat-to-beat effects of on-pump coronary artery bypass graft (CABG) surgery on contractility, cardiac power parameters, arterial load and ventriculo-arterial coupling as well as classical haemodynamic parameters.

METHODS

We included 41 patients scheduled for fast-track CABG surgery. Measurements were taken before and after cardiopulmonary bypass. A flow and pressure curve were recorded from transoesophageal pulsed wave Doppler and a radial artery catheter, respectively. This enabled the calculation of stroke work, total cardiac energy delivery, OPF and Ea/Ees ratio. Routine haemodynamic monitoring provided the classical haemodynamic parameters.

RESULTS

Immediately after cardiopulmonary bypass there was no firm evidence for alterations in contractility, stroke work, stroke volume or arterial elastance. Ea/Ees ratio and OPF remained unchanged.

CONCLUSIONS

There was no evidence for clinically relevant cardiac stunning or altered arterial load immediately after cardiopulmonary bypass for CABG surgery. The unchanged Ea/Ees ratio and OPF are indicating unchanged cardiac efficiency before and after cardiopulmonary bypass. This indicates that in elective CABG patients cardiovascular stunning is perhaps a phenomenon of inflammation and not immediate ischaemia-reperfusion injury or mechanical handling.

Preconditioning in cardiac anesthesia…… where are we?

Preconditioning, a milestone concept in the cardiovascular sciences introduced 32 years back by Murry. This concept opened a new era in the field of organ protection. To start with extensive studies done on ischemic preconditioning for myocardial protection, ischemic preconditioning is an endogenous science of cellular kinetics. Several components in signal transduction cascade have been identified but still some mechanisms not yet revealed. Anesthetic preconditioning also contributed a lot for myocardial protection and concreted the concept of preconditioning. We, with an inquisitive brain meticulously persuing newer methods of cardioprotection. Remote ischemic preconditioning (RIPC) is a brilliant example of it. RIPC can be future of cardioprotection, clinical trials and studies proved the benefits but yet to conclude the superiority of RIPC over myocardial ischemic cardioprotection. This review is an attempt to reveal this extraordinary concept with its basic cellular kinetics, methods, and recent trends.

Myocardial Stunning After Electrocution With Complete Reversibility Within 24 Hours: Role of Repeat Transthoracic Echocardiograms in Potential Cardiac Transplant Donors

Despite the development of ventricular assist devices, cardiac transplantation remains an important procedure for patients with advanced heart failure. The number of transplants done annually has remained stable because of lack of of donors. Left ventricular systolic dysfunction remains one of the most important reasons for seeking a donor heart. Myocardial stunning is an important cause of reversible systolic dysfunction. Electrical injury is a recognized cause of myocardial stunning with variable duration ranging from days to weeks. Repeating the transthoracic echocardiogram to look for reversibility of left ventricular dysfunction can be a cost-effective method to improve the selection of heart donors. This can significantly help to decrease critical organ shortage. We present a case of myocardial stunning after electrocution which was completely reversible within a few hours, thus meeting cardiac transplant donor criteria.

Post cardiac surgery stunning reduces stroke work, but leaves cardiac power output unchanged in patients with normal ejection fraction

This study assesses positional changes in cardiac power output and stroke work compared with classic hemodynamic variables, measured before and after elective coronary artery bypass graft surgery. The hypothesis was that cardiac power output was altered in relation to cardiac stunning. The study is a retrospective analysis of data from two previous studies performed in a tertiary care university hospital. Thirty-six patients scheduled for elective coronary artery bypass graft surgery, with relatively preserved left ventricular function, were included. A pulmonary artery catheter and a radial artery catheter were placed preoperatively. Cardiac power output and stroke work were calculated through thermodilution both supine and standing prior to induction of anesthesia and again day one postoperatively. Virtually all systemic hemodynamic parameters changed significantly from pre- to postoperatively, and from supine to standing. Cardiac power output was maintained at 0.9-1.0 (±0.3) W both pre- and postoperatively and from supine to standing on both days. Stroke work fell from pre- to postoperatively from 1.1 to 0.8 J (P < 0.001), there was a significant fall in stroke work with positional change preoperatively from 1.1 to 0.9 J (P < 0.001). Postoperatively the stroke work remained at 0.8 J despite positional change. Cardiac power output was the only systemic hemodynamic variable which remained unaltered during all changes. Stroke work appears to be a more sensitive marker for temporary cardiovascular dysfunction than cardiac power output. Further studies should explore the relationship between stroke work and cardiac performance and whether cardiac power output is an autoregulated intrinsic physiological parameter.

Detection of small subendocardial infarction using speckle tracking echocardiography in a rat model

BACKGROUND

It is challenging to detect small nontransmural infarcts visually or automatically. As it is important to detect myocardial infarction (MI) at early stages, we tested the hypothesis that small nontransmural MI can be detected using speckle tracking echocardiography (STE) at the acute stage.

METHODS

Minimal nontransmural infarcts were induced in 18 rats by causing recurrent ischemia-reperfusion of the left anterior descending (LAD) coronary artery, followed by a 30-min ligation and by reperfusion. A week later, the scar size was measured by histological analysis. Each rat underwent three echocardiography measurements: at baseline, 1 day post-MI, and 1 week post-MI. To measure the peak circumferential strain (CS), peak systolic CS, radial strain (RS), and time-to-peak (TTP) of the CS, short-axis view of the apex was analyzed by a STE program. The TTP was normalized by the duration of the heart cycle to create percent change of heart cycle.

RESULTS

Histological analysis after 1 week showed scar size of 4±6% at the anterior wall. At 24 h post-MI, the peak CS, peak systolic CS, and RS were reduced compared to baseline at the anterior wall due to the MI, and at the adjacent segments-the anterior septum and lateral wall, due to stunning (P<.05). However, only the anterior wall, the genuine damaged segment, showed prolonged TTP vs baseline (baseline 36%, 24 h 48%, P<.05).

CONCLUSION

The TTP of the CS can distinguish between regions adjacent to MI (stunned or tethered) and MI, even in small nontransmural infarcts.

Strain Analysis in the Detection of Myocardial Infarction at the Acute and Chronic Stages

BACKGROUND

Myocardial ischemia causes contractile dysfunction in ischemic, stunned, and tethered regions with larger infarcted zones having a negative prognostic impact on patients' outcomes. To distinguish the infarcted myocardium from the other regions, we investigated the diagnostic potential of circumferential strain (CS) and radial strain (RS) during the acute and chronic stages of myocardial infarction.

METHODS

Ten pigs underwent 90-minute occlusion of the left anterior descending artery, followed by reperfusion. Echocardiography was performed at baseline, after 90-minute occlusion, and at 2 hours, 30, and 60 days postreperfusion. CS and RS were measured using speckle tracking echocardiography. Subsequently, the pigs were sacrificed, and histological analysis for infarct size was performed.

RESULTS

After 90-minute occlusion, reduced strains were detected for all segments (infarcted anterior wall - baseline: CS: -17.6 ± 5.7%, RS: 54.4 ± 16.9%; 90 min: CS: -10.3 ± 3.0%, RS: 23.3 ± 7.0%; tethered posterior wall - baseline: CS: -18.4 ± 3.5%, RS: 68.7 ± 21.1%; 90 min: CS: -10.7 ± 6.4%, RS: 34.5 ± 14.7%, P < 0.001). However, postsystolic shortening was detected only in the infarcted segments, and the time-to-peak CS was 25% longer (P < 0.05). At 30 and 60 days postreperfusion, time-to-peak CS could only detect large scars in the anterior and anterior-septum walls (P < 0.05), while peak CS also detected smaller scars in the lateral wall (P < 0.05). RS failed to distinguish between normal, stunned/tethered, and infarcted myocardium.

CONCLUSIONS

During occlusion and 2 hours postreperfusion, time-to-peak CS could distinguish between infarcted and stunned/tethered myocardial segments, while at 30 and 60 days postreperfusion, peak CS was the best detector of infarction.

Effect of intravenous administration of antioxidants alone and in combination on myocardial reperfusion injury in an experimental pig model

BACKGROUND

Several antioxidants have been found to have conflicting results in attenuating myocardial reperfusion injury. These studies were done primarily in experimental protocols that did not approximate clinical situations.

OBJECTIVE

The aim of this study was to test the efficacy of 3 different antioxidants (ascorbic acid [AA], desferrioxamine, and N-acetylcysteine [NAC]) administered IV alone and in combination in a closed-chest pig model.

METHODS

Farm-raised domestic male pigs (aged 3-5 months, weight of 30-35 kg) were assigned to 1 of 5 groups to receive treatment as follows: group A, AA 100 mg/kg; group B, desferrioxamine 60 mg/kg; group C, a loading dose of NAC 100 mg/kg for 20 minutes and a 20-mg/kg maintenance dose; group D, all 3 drugs in combination; and group E, normal saline (control group). The infusion of all drugs was started 15 minutes before and completed 5 minutes after reperfusion, except for the administration of NAC, which was terminated 60 minutes postreperfusion. Myocardial ischemia (45 minutes) and reperfusion (210 minutes) were achieved percutaneously by circumflex artery balloon occlusion. Ejection fraction, left ventricular end-diastolic pressure (LVEDP), flow in the infarcted artery, and all ventricular arrhythmias were recorded. Oxidative stress was estimated by serial measurements of thiobarbituric acid reactive substance (TBARS) concentration in coronary sinus blood. Infarct size was assessed as a percentage of the area at risk (I/R ratio) using the tetrazolium red staining method.

RESULTS

The 25 pigs were divided into 5 groups of 5 pigs each. No significant between-group differences were found in I/R ratio or in oxidative stress (as measured by TBARS concentration). Group C developed significantly more ventricular atrhythmias than the control group (80% vs 0%, P = 0.02). No other differences among groups were found. LVEDP was significantly elevated in all treatment groups (mean LVEDP difference [SD] for group A, 6.0 [1.6] mm Hg; group B, 17.6 [1.9] mm Hg; group C, 3.6 [1.7] mm Hg; group D, 6.8 [3.2] and group E, 5.4 [3.4] mm Hg). LVEDP elevation was found to be significantly higher in group B compared with all the other groups (all, P < 0.001). No significant between-group differences were found in the other parameters measured.

CONCLUSION

In this experimental pig model, the antioxidants AA, desferrioxamine, and NAC administered alone or in combination did not reduce the deleterious effects of reperfusion injury and specifically the extent of myocardial necrosis.

Estimation of infarct size using transthoracic Doppler echocardiographic measurement of coronary flow reserve in infarct related and reference coronary artery

BACKGROUND

Patients in chronic phase of myocardial infarction (MI) have decreased coronary flow reserve (CFR) in infarct related artery (IRA) that is proportional to the extent of microvascular/myocardial damage. We proposed a novel model for the assessment of microvascular damage and infarct size using Doppler echocardiography evaluation of CFRs of the IRA (LAD) and reference artery (RCA).

METHODS

Our study included 34 consecutive patients (28 men, mean age 50 ± 11 years) with first anterior STEMI and single vessel disease successfully treated with primary PCI. All patients underwent SPECT MPI for the assessment of infarct size (expressed as a percentage of myocardium with fixed perfusion abnormalities) and CFR evaluation of LAD and RCA. CFR derived percentage of microvascular damage (CFR PMD) was calculated as: CFR PMD=(CFR RCA-CFR LAD)/(CFR RCA-1)×100 (%).

RESULTS

CFR PMD correlated significantly with all parameters evaluating the severity of myocardial damage including: peak CK activity (r=0.632, p<0.001), WMSI (r=0.857, p<0.001), ejection fraction (r=-0.820, p<0.001), left ventricular end diastolic (r=0.757, p<0.001) and end systolic volume (r=0.794, p<0.001). Most importantly, CFR PMD (22 ± 17%) correlated significantly with infarct size by SPECT MPI (21 ± 17%) (r=0.874, p<0.001).

CONCLUSIONS

CFR PMD derived from the proposed model was significantly related to echocardiographic and enzymatic parameters of infarct size, as well as to myocardial damage assessed by SPECT MPI in patients with successfully reperfused first anterior STEMI.

Determination of oxidative stress and cardiac dysfunction after ischemia/reperfusion injury in isolated rat hearts

BACKGROUND

Oxidative stress due to reactive oxygen species (ROS) is thought to play a considerable role in ischemia/reperfusion (I/R) injury that impairs cardiac function. The present study examined oxidative damage in I/R injury and investigated the correlation between oxidative stress and impaired cardiac function after I/R injury of the isolated rat heart.

METHODS

Hearts isolated from male Sprague-Dawley rats were mounted on a Langendorff apparatus. Hearts arrested using St. Thomas cardioplegic solution and then they were reperfused. The hearts were divided into three groups depending on the frequency (0-2) of I/R. After I/R, left ventricular developed pressure (LVDP), left ventricular end-diastolic pressure (LVEDP), positive maximum left ventricular developing pressure (max LV dP/dt) and coronary flow (CF) were measured. Creatine kinase (CK) was measured in the coronary effluent and 8-hydroxy-2'deoxyguanosine (8OHdG), a marker of oxidative DNA damage, was measured. Adenosine triphosphate (ATP) was measured from frozen myocardial tissue after experiment.

RESULTS

We immunohistochemically demonstrated and quantified levels of 8-OHdG after I/R injury of the heart. The frequency of I/R injury and cardiac dysfunction significantly and negatively correlated. The ATP products were similar among the three groups. The incidence of ventricular arrhythmias was not by affected oxidative stress.

CONCLUSION

The frequency of I/R injury had more of an effect on 8-OHdG products and on impaired cardiac function with less myocyte damage than ischemic duration within 30 minutes of ischemia.

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

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

Effect of thrombin fragment (TP508) on myocardial ischemia-reperfusion injury in hypercholesterolemic pigs

Myocardial ischemia-reperfusion (IR) injury occurs frequently in the setting of hypercholesterolemia. We investigated the potential efficacy of a novel thrombin fragment (TP508) on IR injury in a hypercholesterolemic porcine model. Twenty-one hypercholesterolemic male Yucatan pigs underwent 60 min of mid-left anterior descending coronary artery occlusion followed by 120 min of reperfusion. Pigs received either placebo (control, n = 7) or TP508 in two doses (TP508 low dose, n = 7, as bolus of 0.5 mg/kg 50 min into ischemia and an infusion of 1.25 mg.kg(-1).h(-1) during reperfusion period or TP508 high dose, n = 7, a double dose of TP508 low-dose group). Myocardial function was monitored throughout the experiment. The area at risk and myocardial necrosis were determined by Monastryl blue/triphenyl tetrazolium chloride staining. Apoptosis in the ischemic territory was assessed. Coronary microvascular reactivity to endothelium-dependent and -independent factors was measured. Myocardial necrosis was lower in both TP508-treated groups vs. control (P < 0.05). Regional left ventricular function was improved only in the TP508 high-dose group (P < 0.05). Endothelium-dependent coronary microvascular reactivity was greater in both TP508-treated groups (P < 0.05) vs. control. The expression of proteins favoring cell survival, 90-kDa heat shock protein and phospho-Bad (Ser112) was higher in the TP508 high-dose group (P < 0.05). The expression of the cell death signaling proteins, cleaved caspase-3 (P < 0.05), apoptosis-inducing factor (P < 0.05), and poly-ADP ribose polymerase (P = 0.07) was lower in the TP508 low-dose group vs. TP508 high-dose and control. The terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling positive cell count was lower in both TP508 groups compared with the control (P < 0.05). This study demonstrates that, in hypercholesterolemic pigs, TP508 decreases myocardial necrosis and apoptosis after IR. Thus TP508 may offer a novel approach in protecting the myocardium from IR injury.

Thrombin fragment (TP508) decreases myocardial infarction and apoptosis after ischemia reperfusion injury

BACKGROUND

Myocardial ischemia-reperfusion injury may lead to cardiac dysfunction or death. This study investigates the potential efficacy of a novel thrombin fragment (TP508) on myocardial ischemia-reperfusion injury.

METHODS

Fourteen male Yucatan pigs underwent 60 minutes of mid-left anterior descending coronary artery occlusion followed by 120 minutes of reperfusion. Pigs received either saline vehicle (control, n = 7) or thrombin fragment TP508 (n = 7) as a bolus (0.5 mg/kg) 50 minutes into the ischemic period, followed by continuous intravenous infusion (1.25 mg x kg(-1) x h(-1)) during reperfusion. Myocardial function was monitored throughout the experiments. Monastryl blue/triphenyl tetrazolium chloride staining was utilized to measure the area at risk and infarcted tissue. Apoptosis was assessed by Western blotting and dUTP nick-end labeling (TUNEL) staining. Coronary microvascular reactivity to endothelium-dependent factors (adenosine diphosphate, substance P, A23187) and endothelium-independent factor (sodium nitroprusside) was examined.

RESULTS

Global and regional left ventricular function was not significantly different between groups. Endothelium-dependent coronary microvascular relaxation was greater in the TP508 group and associated with higher endothelial nitric oxide synthase phosphorylation. Both infarct size and TUNEL staining was significantly decreased in the TP508 group compared with the control group (p < 0.05). Expression of the cell survival proteins B-cell lymphoma 2 (2.2-fold, p < 0.05) and heat shock protein-73 (1.6-fold, p < 0.05) was higher in the TP508 group. Expression of the cell-death-signaling proteins poly adenosine diphosphate-ribose polymerase (1.6-fold, p < 0.05), cleaved poly adenosine diphosphate-ribose polymerase (6.4-fold, p < 0.05), and B-cell lymphoma 2/adenovirus E1B 19 kDa-interacting protein 3 (3.8-fold, p < 0.05) was significantly higher in the TP508 group in the ischemic territory.

CONCLUSIONS

This study demonstrates that TP508 decreases infarct size, improves endothelial microvascular function, and induces cell-survival signaling in the setting of ischemia-reperfusion injury. Thus, TP508 may be a useful agent to attenuate myocardial reperfusion injury.

Does the pre-ischaemic administration of sevoflurane reduce myocardial stunning? A porcine experimental model

BACKGROUND

In a porcine model, the cardioprotective effect of sevoflurane was studied with regard to the preservation of myocardial contractility (myocardial stunning) after a myocardial ischaemic insult.

METHODS

Twenty-seven pigs were randomized to receive either a dual 4% sevoflurane inhalation period as a supplement to pentobarbital anaesthesia or pentobarbital anaesthesia only before a 15-min ischaemic insult on the left anterior descending coronary artery. The ischaemic period was followed by 180 min of reperfusion. Myocardial contractility was assessed by myocardial sonomicrometry.

RESULTS

A significant difference was found between the sevoflurane group and the control group at 5 min of reperfusion. However, subsequently, there was no overall difference between the two groups.

CONCLUSION

Sevoflurane administered as a pre-ischaemic bolus does not provide long-term improvement of the myocardial contractility. However, it can be speculated that sevoflurane may induce an early improvement in contractility.

Severe stunned myocardium after lightning strike

OBJECTIVE

To report the development of myocardial stunning and severe heart failure after lightning strike with total recovery of function.

DESIGN

Case report.

SETTING

Coronary care unit at Medica Sur Clinic, Mexico.

PATIENT

A 42-yr-old woman who was hit by lightning developed rapid and progressive hemodynamic deterioration manifested by cardiogenic shock that required invasive monitoring. Twenty-four hours after the strike, intravenous levosimendan and intra-aortic balloon pump were initiated because the patient demonstrated no significant response to management with conventional inotropic agents. Two days later, echocardiographic signs of systolic and diastolic dysfunction improved markedly. Dual-isotope-imaging myocardial perfusion testing with technetium-99m-sestamibi and thallium-201, performed 9 days after admission, showed normal perfusion and normal left ventricular systolic function. The patient exhibited complete recovery of function. The exact mechanism of abnormal contractility in the absence of direct electrofulguration is unknown but may be explained by release of oxygen free radicals, proteolysis of the contractile apparatus, and cytosolic overload of intracellular calcium, followed by reduced myofilament sensitivity to calcium. These abnormalities are consistent with stunned myocardium.

CONCLUSIONS

Lightning strike may cause serious contractile dysfunction in the absence of irreversible myocardial injury, but the exact mechanism of this phenomenon remains unknown. We propose that lighting strike can cause myocardial stunning resulting in severe but reversible left ventricular dysfunction. The patient's recovery was facilitated by support treatment including administration of levosimendan, which increases the intracellular sensitivity to calcium, a mechanism disturbed in patients with myocardial stunning.

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

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

Left ventricular apical thrombus after systemic thrombolysis with recombinant tissue plasminogen activator in a patient with acute ischemic stroke

BACKGROUND

Thrombolysis with recombinant tissue plasminogen activator (rtPA) is an established treatment in acute stroke. To prevent rethrombosis after rtPA therapy, secondary anticoagulation with heparin is commonly performed. However, the recommended time-point and extent of heparin treatment vary and are not well investigated.

CASE PRESENTATION

We report a 61-year-old man who developed an acute global aphasia and right-sided hemiparesis. Cranial CT was normal and systemic thrombolytic therapy with tPA was started 120 minutes after symptom onset. Low-dose subcutaneous heparin treatment was initiated 24 hours later. Transthoracic echocardiography (TTE) 12 hours after admission showed slightly reduced left ventricular ejection fraction (LVEF) but was otherwise normal. 48 hours later the patient suddenly deteriorated with clinical signs of dyspnea and tachycardia. TTE revelead a large left ventricular apical thrombus as well as a reduction of LVEF to 20 %. Serial further TTE investigations demonstrated a complete resolution of the thrombus and normalisation of LVEF within two days.

CONCLUSION

Our case demonstrates an intracardiac thrombus formation following rtPA treatment of acute stroke, probably caused by secondary hypercoagulability. Rethrombosis or new thrombus formation might be an underestimated complication of rtPA therapy and potentially explain cases of secondary stroke progression.

Usefulness of low-dose dobutamine stress echocardiography for the evaluation of spontaneous recovery of stunned myocardium in patients with acute right ventricular infarction

Right ventricular (RV) infarction (RVI) is usually associated with severe RV global dysfunction representing predominantly stunned myocardium that may respond favorably to reperfusion. We assessed the efficacy of low-dose dobutamine stress echocardiography (DSE), performed early in the course of a reperfused RVI, to predict the recovery of RV systolic and diastolic function in 3 months, documenting the recovery of stunned myocardium. In all, 27 patients with acute, successfully thrombolyzed RVI comprised the study population. All patients underwent standard echocardiography at baseline and 3 months later for evaluation of RV systolic and diastolic function. At day 5 DSE was performed for evaluation of RV contractile reserve. Of the total number of segments analyzed, 69% were detected as stunned. At baseline, RV systolic and diastolic indices were seriously impaired showing significant improvement at follow-up. RV wall-motion score index during DSE was positively correlated with the same index at follow-up. DSE is a safe and precise modality to predict recovery of stunned myocardium in the setting of RVI.

Myocardial SPECT perfusion defect size compared to infarct size by delayed gadolinium-enhanced magnetic resonance imaging in patients with acute or chronic infarction

BACKGROUND

Single photon emission computed tomography (SPECT) perfusion imaging has been considered a reference method for non-invasive estimation of infarct size in man. Recently, delayed gadolinium-enhanced magnetic resonance imaging (DE-MRI) has evolved as an accurate tool to quantify infarct size. Therefore, the present study was designed to compare perfusion defect size by SPECT to hyperenhanced volume by DE-MRI.

METHODS

DE-MRI was performed in 30 patients. Fourteen were patients with revascularized first-time acute infarctions, eight revascularized chronic infarctions, and eight clinically referred non-revascularized patients. SPECT was performed in the same patients and analysed by a commercial package.

RESULTS

The hypoperfused volume by SPECT was larger than the hyperenhanced volume by DE-MRI by 8 +/- 8 ml (6% +/- 5 percentage points), 10 +/- 18 ml (6% +/- 11 percentage points), and 26 +/- 30 ml (12% +/- 10 percentage points) in the acute, chronic and clinical populations, respectively. Left ventricle wall volume was smaller by SPECT in all settings.

CONCLUSION

The SPECT perfusion defect size was comparable with but generally slightly larger than the hyperenhanced volume by DE-MRI in both absolute and relative terms in patients with acute and chronic infarction. The results may be related to systematic differences between modalities but could also be influenced by biological phenomena such as wall thinning or hypoperfused but viable myocardium.

Convalescent stage coronary flow reserve and late myocardial morphologic outcomes in patients with first anterior acute myocardial infarction

BACKGROUND

Microvascular damage immediately after reperfusion therapy is an independent predictor of left ventricular function in patients with acute myocardial infarction (AMI). However, its recovery may vary among individuals and the relationship between convalescent stage microvasculature and late myocardial morphologic change is unclear.

METHODS AND RESULTS

Patients treated with coronary angioplasty within 12 h of their first anterior AMI were enrolled in this study. Coronary flow reserve (CFR) was measured 3 weeks post AMI, in both branches of the left coronary artery: culprit (left anterior descending artery: LAD) and non-culprit (left circumflex artery: LCX). Left ventriculography was performed at 3 weeks and 6 months post AMI and compared. Seventeen patients showed abnormal CFR in the LAD (Group 1: CFR<2), whereas 20 patients showed normal CFR (Group 2: CFR >/=2). Percent changes of end-diastolic volume tended to be higher in Group 1 than in Group 2 (11.8+/-21.6% vs -1.3+/-14.4%, p=0.056), and %changes of end-systolic volume was significantly smaller in Group 2 (11.8+/-22.1% vs -8.7+/-25.1%, p<0.05). A statistically significant correlation was found between absolute and relative CFR in the LAD and %change of end-systolic volume (r=-0.58: p<0.001, and r=0.40: p<0.05, respectively).

CONCLUSIONS

Microvascular function in the convalescent stage may be related to these favorable changes.

Myocardial stunning during abdominal hysterectomy in a healthy woman

We report a case of myocardial stunning in a healthy patient. During gynecologic surgery, two brief episodes of asystole occurred. Following resuscitation there was a short period of severe hypertension and tachycardia. Electrocardiographic changes and elevations in troponin T and creatine-kinase-MB were observed. Angiography revealed normal coronary arteries and multiple areas of hypokinesis. Within 2 weeks, all abnormal values had returned to normal and the patient underwent an uneventful surgery.

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

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