Coronary microembolization

How preclinical models help to improve outcome in cardiogenic shock

PURPOSE OF REVIEW

Preclinical experimentation of cardiogenic shock resuscitation on large animal models represents a powerful tool to decipher its complexity and improve its poor outcome, when small animal models are lacking external validation, and clinical investigation are limited due to technical and ethical constraints. This review illustrates the currently available preclinical models addressing reliably the physiopathology and hemodynamic phenotype of cardiogenic shock, highlighting on the opposite questionable translation based on low severity acute myocardial infarction (AMI) models.

RECENT FINDINGS

Three types of preclinical models replicate reliably AMI-related cardiogenic shock, either with coronary microembolization, coronary deoxygenated blood perfusion or double critical coronary sub-occlusion. These models overcame the pitfall of frequent periprocedural cardiac arrest and offer, to different extents, robust opportunities to investigate pharmacological and/or mechanical circulatory support therapeutic strategies, cardioprotective approaches improving heart recovery and mitigation of the systemic inflammatory reaction. They all came with their respective strengths and weaknesses, allowing the researcher to select the right preclinical model for the right clinical question.

SUMMARY

AMI-related cardiogenic shock preclinical models are now well established and should replace low severity AMI models. Technical and ethical constraints are not trivial, but this translational research is a key asset to build up meaningful future clinical investigations.

Diffuse non-obstructive coronary artery disease: two clinical faces of the same disease-a case report

Background

Coronary artery disease has a long preclinical phase before manifesting itself clinically due to diffuse non-obstructive disease, stenoses, or thrombosis.

Case summary

We present a case of a middle-aged male complaining of atypical chest pain, then severe retrosternal pain, and, eventually, effort angina. We performed non-invasive testing, coronary angiography, intravascular imaging, and flow reserve tests, each as appropriate. Cardiovascular risk control, optimization of drug therapy, and percutaneous coronary intervention were considered trying to comply with the best clinical practice.

Discussion

Diffuse non-obstructive coronary artery disease may present clinically in different ways. Exercise stress test might be sufficient to assess effort angina before a potential angiography. Flow reserve tests across the diseased vessel can distinguish between diffuse and focal pattern of the disease and assist in the adequate selection of therapy. Finally, intravascular imaging is invaluable for the assessment of the plaque risk features.

Angiography-Derived and Sensor-Wire Methods to Assess Coronary Microvascular Dysfunction in Patients With Acute Myocardial Infarction

ST-segment elevation myocardial infarction (STEMI) treatment with primary percutaneous coronary intervention has dramatically impacted prognosis. However, despite satisfactory angiographic result, occurrence or persistence of coronary microvascular dysfunction after revascularization still affects long-term outcomes. The diagnostic and therapeutic value of understanding the status of coronary microcirculation is gaining attention in the cardiology community. However, current methods to assess microvascular function (namely, cardiac magnetic resonance and invasive wire-based coronary physiology) remain, at least in part, limited by technical and logistic aspects. On the other hand, angiography-based indices of microcirculatory resistance are emerging as valid and user-friendly tools with potential impact on prognostic stratification of patients with STEMI. This review provides an overview about conventional and novel methods to assess coronary microvascular dysfunction in patients with STEMI. The authors also provide a proposed procedural algorithm to facilitate optimal use of wire-based and angiography-based indices in the acute setting of STEMI.

A fresh look at coronary microembolization

Mechanical stress from haemodynamic perturbations or interventional manipulation of epicardial coronary atherosclerotic plaques with inflammatory destabilization can release particulate debris, thrombotic material and soluble substances into the coronary circulation. The physical material obstructs the coronary microcirculation, whereas the soluble substances induce endothelial dysfunction and facilitate vasoconstriction. Coronary microvascular obstruction and dysfunction result in patchy microinfarcts accompanied by an inflammatory reaction, both of which contribute to progressive myocardial contractile dysfunction. In clinical studies, the benefit of protection devices to retrieve atherothrombotic debris during percutaneous coronary interventions has been modest, and the treatment of microembolization has mostly relied on antiplatelet and vasodilator agents. The past 25 years have witnessed a relative proportional increase in non-ST-segment elevation myocardial infarction in the presentation of acute coronary syndromes. An associated increase in the incidence of plaque erosion rather than rupture has also been recognized as a key mechanism in the past decade. We propose that coronary microembolization is a decisive link between plaque erosion at the culprit lesion and the manifestation of non-ST-segment elevation myocardial infarction. In this Review, we characterize the features and mechanisms of coronary microembolization and discuss the clinical trials of drugs and devices for prevention and treatment.

Role of cardiovascular magnetic resonance in the prognosis of patients with myocardial infarction with non-obstructive coronary arteries

BACKGROUND

It is estimated that 5% to 10% of patients with myocardial infarction (MI) present with no obstructive coronary artery lesions. Until now, most studies have focused on acute coronary syndrome, including different clinical entities with a similar presentation encompassed under the term MINOCA (MI with non-obstructive coronary arteries). The aim of this study is to assess the prognosis of patients diagnosed with true infarction, confirmed by cardiovascular magnetic resonance (CMR), in the absence of significant coronary lesions.

METHODS

Prospective multicenter registry study, including 120 consecutive patients with a CMR-confirmed MI without obstructive coronary artery lesions. The primary clinical outcome was major adverse cardiovascular events (MACE: death, non-fatal infarction, stroke, or cardiac readmission), assessed over three years.

RESULTS

Seventy-six patients (63.3%) were admitted with a diagnosis of acute coronary syndrome, and 44 (36.6%) for other causes (mainly heart failure); the definitive diagnosis was established by CMR. Most patients (64.2%) were men, and the mean age was 58.8 ± 13.5 years. Patients presented with small infarcts: 83 (69.1%) showed late gadolinium enhancement (LGE) in one or two myocardial segments, mainly transmural (in 77.5% of patients) and with a preserved left ventricular ejection fraction (median 54.8%, interquartile range 37-62). The most frequent infarct location was inferolateral (n = 38, 31.7%). During follow-up, 43 patients (35.8%) experienced a MACE, including 9 (7.5%) who died. In multivariable analysis, LGE in two versus one myocardial segment doubled the risk of adverse cardiac events (hazard ratio [HR] 2.32, 95% confidence interval [CI] 0.97-5.83, p = 0.058). Involvement of three or more myocardial segments almost tripled the risk (HR 2.71, 95% CI 1.04-7.04, p = 0.040 respectively).

CONCLUSIONS

Patients with true MI but without significant coronary artery lesions predominantly had small infarcts. Myocardial 3-segment LGE involvement is associated with a significantly higher risk of adverse cardiac events.

Overexpression of lncRNA TUG1 Alleviates NLRP3 Inflammasome-Mediated Cardiomyocyte Pyroptosis Through Targeting the miR-186-5p/XIAP Axis in Coronary Microembolization-Induced Myocardial Damage

Coronary microembolization (CME) is a complicated problem that commonly arises in the context of coronary angioplasty. The lncRNA taurine-up regulated gene 1 (TUG1), significantly contributes to cardiovascular diseases; however, its contribution to CME-induced myocardial damage remains elusive. Herein, we establish the rat CME model and investigate the role of TUG1 in CME. The cell viability was evaluated via CCK-8 assay. Serum and cell culture supernatant samples were evaluated via ELISA. The dual luciferase reporter (DLR) assay, RIP, and RNA-pull down were conducted to validate the associations between TUG1 and miR-186-5p as well as miR-186-5p and XIAP. The expression of TUG1, miR-186-5p, and XIAP mRNA were determined by RT-qPCR, and proteins were evaluated via immuneblotting. As a result, TUG1 and XIAP were significantly down-regulated, and the miR-186-5p level was found to be remarkably up-regulated in CME myocardial tissues. Overexpression of TUG1 alleviated CME-induced myocardial injury and pyroptosis, whereas TUG1 knockdown showed the opposite effects. The DLR assay, RIP, and RNA-pull down results reveal that TUG1 directly targets miR-186-5p and miR-186-5p directly targets XIAP. In vitro rescue experiments show that TUG1 overexpression alleviates LPS-caused cardiomyocyte injury and pyroptosis via sponging miR-186-5p and regulating XIAP, and depression of miR-186-5p reduces LPS-induced cardiomyocyte injury and pyroptosis by targeting XIAP. Concludingly, the overexpression of TUG1 alleviates NLRP3 inflammasome-mediated cardiomyocyte pyroptosis through targeting the miR-186-5p/XIAP axis in CME-induced myocardial injury.

Cardiac troponin I measured with a very high sensitivity assay predicts subclinical carotid atherosclerosis: The Akershus Cardiac Examination 1950 Study

AIMS

Concentrations of cardiac troponin I (cTnI) are associated with incident ischemic stroke and predict the presence and severity of coronary atherosclerosis. Accordingly, we hypothesized that concentrations of cTnI measured with a very high sensitivity (hs-) assay would be associated with subclinical stages of carotid atherosclerosis in the general population.

METHODS

We measured hs-cTnI on the Singulex Clarity System in 1745 women and 1666 men participating in the prospective observational Akershus Cardiac Examination 1950 Study. All study participants were free from known coronary heart disease and underwent extensive cardiovascular phenotyping at baseline, including carotid ultrasound. We quantified carotid atherosclerosis by the carotid plaque score, carotid intima-media thickness (cIMT) and the presence of hypoechoic plaques.

RESULTS

Concentrations of hs-cTnI were measurable in 99.8% of study participants and were significantly associated with increased carotid plaque score (odds ratio for quartile 4 of hs-cTnI 1.59, 95% CI 1.22 to 2.07, p for trend < 0.001) and cIMT (odds ratio for quartile 4 of hs-cTnI 1.57, 95% CI 1.02 to 2.42, p for trend = 0.036), but not with the presence of hypoechoic plaques. hs-cTnI concentrations significantly improved reclassification and discrimination models in predicting carotid plaques when added to cardiovascular risk factors, no improvements were evident in predicting cIMT or hypoechoic plaques.

CONCLUSION

Concentrations of cTnI measured with a very high sensitivity assay are predictive of carotid atherosclerotic burden, a phenomenon likely attributable to common risk factors of subclinical myocardial injury, coronary and carotid atherosclerosis.

Cryptotanshinone ameliorates cardiac injury and cardiomyocyte apoptosis in rats with coronary microembolization

Coronary microembolization (CME) is a prevalent cardiovascular disease, especially nowadays when percutaneous coronary intervention is widely applied. However, neither cardio-protective agents nor devices for distal protection could effectively prevent the occurrence of CME. Therefore, we aimed to develop a new drug for CME. Rats were orally administrated with different doses of Cryptotanshinone (CTS, 5, 15, 45 mg/kg) daily for 2 weeks, respectively, following CME surgery. Then cardiac function and cardiac injury were evaluated in CME rats as well as measuring oxidative stress and apoptosis in cardiomyocytes. Compared to sham group, CME operation induced cardiac dysfunction, cardiac injury, the activation of platelet and endothelium, cardiomyocyte apoptosis and oxidative stress, all of which could be dose-dependently restored by CTS pretreatment. Moreover, NF-κB signaling pathway participated in the development of CME and also in the preventive process of CTS against CME. CTS might serve as a potential and promising candidate drug to prevent the occurrence of CME.

The prognostic significance of periprocedural infarction in the era of potent antithrombotic therapy. The PRAGUE-18 substudy

BACKGROUND

The prognostic significance of periprocedural myocardial infarction (MI) remains controversial.

METHODS AND RESULTS

The study aims to investigate the incidence of periprocedural MI in the era of high sensitivity diagnostic markers and intense antithrombotics, and its impact on early outcomes of patients with acute MI treated with primary angioplasty (pPCI). Data from the PRAGUE-18 (prasugrel versus ticagrelor in pPCI) study were analyzed. The primary net-clinical endpoint (EP) included death, spontaneous MI, stroke, severe bleeding, and revascularization at day 7. The key secondary efficacy EP included cardiovascular death, spontaneous MI, and stroke within 30 days. The incidence of peri-pPCI MI was 2.3% (N = 28) in 1230 study patients. The net-clinical EP occurred in 10.7% of patients with, and in 3.6% of patients without, peri-pPCI MI (HR 2.92; 95% CI 0.91-9.38; P = 0.059). The key efficacy EP was 10.7% and 3.2%, respectively (HR 3.44; 95% CI 1.06-11.13; P = 0.028). Patients with periprocedural MI were at a higher risk of spontaneous MI (HR 6.19; 95% CI 1.41-27.24; P = 0.006) and stent thrombosis (HR 10.77; 95% CI 2.29-50.70; P = 0.003) within 30 days. Age, hyperlipidemia, multi-vessel disease, post-procedural TIMI <3, pPCI on circumflex coronary artery, and periprocedural GP IIb/IIIa inhibitor were independent predictors of peri-pPCI MI.

CONCLUSIONS

In the era of intense antithrombotic therapy, the occurrence of peri-pPCI MI is despite highly sensitive diagnostic markers a rare complication, and is associated with an increased risk of early reinfarction and stent thrombosis.

Large Animal Models of Heart Failure: A Translational Bridge to Clinical Success

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Preclinical large animal models play a critical and expanding role in translating basic science findings to the development and clinical approval of novel cardiovascular therapeutics.

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This state-of-the-art review outlines existing methodologies and physiological phenotypes of several HF models developed in large animals. A comprehensive list of porcine, ovine, and canine models of disease are presented, and the translational importance of these studies to clinical success is highlighted through a brief overview of recent devices approved by the FDA alongside associated clinical trials and preclinical animal reports.

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Increasing the use of large animal models of HF holds significant potential for identifying new mechanisms underlying this disease and providing valuable information regarding the safety and efficacy of new therapies, thus, improving physiological and economical translation of animal research to the successful treatment of human HF.

Preclinical large animal models of heart failure (HF) play a critical and expanding role in translating basic science findings to the development and clinical approval of novel therapeutics and devices. The complex combination of cardiovascular events and risk factors leading to HF has proved challenging for the development of new treatments for these patients. This state-of-the-art review presents historical and recent studies in porcine, ovine, and canine models of HF and outlines existing methodologies and physiological phenotypes. The translational importance of large animal studies to clinical success is also highlighted with an overview of recent devices approved by the Food and Drug Administration, together with preclinical HF animal studies used to aid both development and safety and/or efficacy testing. Increasing the use of large animal models of HF holds significant potential for identifying the novel mechanisms underlying the clinical condition and to improving physiological and economical translation of animal research to successfully treat human HF.

Diagnostic dilemma of perioperative myocardial infarction after coronary artery bypass grafting: A review

Coronary artery bypass grafting (CABG) is one of the most commonly performed cardiac procedures in the United States (US) and Europe. In the US, perioperative morbidity and mortality related to CABG are below 5%. One of the most significant complications following CABG, however, is perioperative myocardial infarction (PMI). Cardiac biomarkers, intra- and post-operative echocardiography, and electrocardiography are routinely used to monitor for evidence of PMI. In this review, we seek to summarize how each of these modalities is used in the clinical setting to differentiate PMI from expected procedure-related changes, and how these findings impact patients' outcomes. We conclude that while no perfect diagnostic test for the detection of clinically meaningful PMI exists, using a combination of existing modalities with knowledge of expected post-procedure changes allows for early and reliable detection. Future development is needed to create more sensitive and specific modalities for the detection of PMI in patients undergoing CABG.

Egr-1 is involved in coronary microembolization-induced myocardial injury via Bim/Beclin-1 pathway-mediated autophagy inhibition and apoptosis activation

Coronary microembolization (CME) substantially reduces the clinical benefits of myocardial reperfusion therapy. Autophagy and apoptosis participate in the pathophysiological processes of almost all cardiovascular diseases, including CME-induced myocardial injury, but the precise underlying mechanisms remain unclear. In the present study, we observed that Egr-1 expression was substantially increased after CME modeling. Inhibition of Egr-1 expression through the targeted delivery of rAAV9-Egr-1-shRNA improved cardiac function and reduced myocardial injury. The microinfarct size was also significantly smaller in the Egr-1 inhibitor group than in the CME group. These benefits were partially reversed by the autophagy inhibitor 3-MA. As shown in our previous study, autophagy in the myocardium was impaired after CME. Inhibition of Egr-1 expression in vivo restored the autophagy flux and reduced myocardial apoptosis, at least partially, by inhibiting the Egr-1/Bim/Beclin-1 pathway, as evidenced by the results of the western blot, RT-qPCR, and TUNEL staining. At the same time, TEM showed a dramatic increase in the number of typical autophagic vacuoles in the Egr-1 inhibitor group compared to the CME group. Based on these findings, the Egr-1/Bim/Beclin-1 pathway may be involved in CME-induced myocardial injury by regulating myocardial autophagy and apoptosis, and this pathway represents a potential therapeutic target in CME.

miR-30e-5p Mitigates Hypoxia-Induced Apoptosis in Human Stem Cell-Derived Cardiomyocytes by Suppressing Bim

Coronary microembolization can cause slow or no reflow, which is one of the crucial reasons for reverse of clinical advantage from cardiac reperfusion therapy. miRNAs and apoptosis are dramatically involved in the occurrence and process of cardiovascular diseases. Fortunately, human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have emerged as an appealing model for the evaluation of cardiovascular diseases. Therefore, our study was designed to explore the role of miR-30e-5p and apoptosis in a hypoxia-induced hiPSC-CM injury model. Our results showed that the expression levels of miR-30e-5p were overtly downregulated in a time-dependent manner under hypoxic conditions. Expression of miR-30e-5p was significantly downregulated after 24 hours of hypoxia, hypoxia treatment dramatically induced apoptosis. Calcium handling capability significantly decreased after 24 hours of hypoxia treatment. miR-30e-5p overexpression partially mitigated hypoxia-induced apoptosis and rescued hypoxia-induced calcium handling defects in hiPSC-CMs. The luciferase reporter assay showed that miR-30e-5p can directly target the 3'-UTR of Bim, which is an apoptosis activator and autophagy suppressor. The mRNA and protein of Bim remarkably increased after hypoxia treatment and reduced with miR-30e-5p overexpression. Moreover, downregulation of Bim mitigated hypoxia-induced apoptosis and activated autophagy. These results demonstrated that miR-30e-5p mitigated hypoxia-induced apoptosis in hiPSC-CMs at least in part via Bim suppression and subsequent autophagy activation. Our study suggested miR-30e-5p may act as a potential therapeutic target for coronary microembolization.

Proteomics Analysis of Myocardial Tissues in a Mouse Model of Coronary Microembolization

Coronary microembolization (CME) is an important clinical problem, and it is related to poor outcome. The specific molecular mechanisms of CME are not fully understood. In the present study, we established a mice model of CME. Isobaric tags for relative and absolute quantitation (iTRAQ) and liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) technologies identified 249 differentially expressed proteins in the myocardial tissues of CME mice as compared with sham-operated mice. Bioinformatics analysis demonstrated that these differentially expressed proteins were enriched in several energy metabolism or cytoskeleton organization related processes or pathways. Quantitative PCR and Western blotting validation experiments revealed that succinate dehydrogenase (SDHA and SDHB) were upregulated, Rho GDP dissociation inhibitor α (RhoGDIα) and Filamin-A (FLNA) were downregulated significantly in CME mice. These findings indicated that the alternations of the cytoskeleton and energy metabolism pathways play important roles in the pathogenesis of CME, future studies are warranted to verify if targeting these molecules might be useful to alleviate CME injury or not.

Liraglutide attenuates NLRP3 inflammasome-dependent pyroptosis via regulating SIRT1/NOX4/ROS pathway in H9c2 cells

The glucagon-like peptide-1 analog liraglutide has been proved to exert cardioprotective role via activating prosurvival pathways and suppressing inflammation. The activation of NLRP3 inflammasome plays an important role in ischemic injury. The effect of liraglutide on NLRP3 inflammasome-dependent pyroptosis remains unclear. In this study, we established a double stimulation model with TNF-α and hypoxia to mimic ischemic environment and to induce NLRP3 inflammasome activation in H9c2 cardiomyoblasts. Pretreatment with 100 nM liraglutide could efficiently inhibit TNF-α and hypoxia-induced inflammasome activation, as evidenced by the decreased expression of NLRP3, caspase-1 p20 and Gasdermin D N-terminal fragment. Meanwhile, the pyroptosis was also demonstrated to be suppressed, indicated by the increased cell viability and decreased lactate dehydrogenase release in the cells. Mechanistically, liraglutide reversed the level of SIRT1 and the selective SIRT1 inhibitor EX 527 significantly abolished the anti-pyroptosis role of liraglutide. Furthermore, liraglutide diminished the levels of ROS generation and NOX4 expression, which could also be blocked by EX 527. Our results uncovered the anti-pyroptosis role of liraglutide in TNF-α and hypoxia-stimulated H9c2 cells, which was associated with SIRT1/NOX4/ROS pathway.

Coronary microembolization and microvascular dysfunction

Plaque erosion, fissuring or rupture occurs spontaneously or during coronary interventions. At some residual blood flow, the atherothrombotic debris is washed into the coronary microcirculation, causing physical obstruction, vasoconstriction, inflammation and ultimately microinfarction. Coronary microembolization also contributes to microvascular obstruction in reperfused acute myocardial infarction. Patients with microvascular obstruction after reperfused myocardial infarction have worse prognosis. Cardioprotective strategies to avoid acute coronary microembolization and rescue myocardium from microvascular obstruction have not yet been established in clinical practice. Subclinical coronary microembolization together with release of thrombogenic, vasoconstrictor and inflammatory substances from a culprit lesion can sensitize the coronary microcirculation and contribute to angina in the absence of major epicardial coronary obstruction. Repetitive coronary microembolization can induce progressive loss of functional cardiomyocytes and induce heart failure in the absence of overt myocardial infarction.

Efficacy and safety of intracoronary verapamil versus sodium nitroprusside for the prevention of microvascular obstruction during primary percutaneous coronary intervention for ST-segment elevation myocardial infarction

OBJECTIVE

The aim of this study was to compare the role of intracoronary (IC) verapamil versus sodium nitroprusside (SNP) in the prevention of microvascular obstruction (MVO) during a primary percutaneous coronary intervention (pPCI).

BACKGROUND

A head-to-head comparison between verapamil and SNP in the prevention of MVO lacks evidence.

PATIENTS AND METHODS

Sixty patients with ST-segment elevation myocardial infarction were randomized to receive IC verapamil (n=30) versus SNP (n=30) during pPCI. The primary outcome was the incidence of angiographic MVO as defined by Thrombolysis In Myocardial Infarction flow less than 3 or Thrombolysis In Myocardial Infarction flow 3 with myocardial blush grade less than 2. The secondary outcomes were the percentage of ST-segment resolution on 12-lead ECG, left ventricular ejection fraction and wall motion score index by two-dimensional echocardiography at 3-5 days after pPCI, as well as major adverse cardiovascular events at 30 days. Safety outcomes were the incidence of hypotension and/or bradycardia during pPCI.

RESULTS

Verapamil was associated with lower incidence of angiographic MVO compared with SNP (13.3 vs. 40%, respectively; P=0.02), as well as superior ST-segment resolution greater than or equal to 70% (33.3 vs. 6.7%, respectively; P=0.01). There was a trend towards improved left ventricular ejection fraction with verapamil (42.6±4.9 vs. 40.4±4.7%, respectively; P=0.09), but with similar wall motion score index (1.43±0.1 vs. 1.45±0.2, respectively; P=0.14). Both groups had similar 30-day major adverse cardiovascular events (3.3 vs. 6.7%, respectively; P=0.55). Verapamil was associated with lower incidence of hypotension compared with SNP (3.3 vs. 20%, respectively; P=0.04).

CONCLUSION

In pPCI, IC verapamil results in significant improvements in MVO with a better safety profile compared with SNP. Larger trials should be conducted to confirm these results.

Pretreatment with a combination of ligustrazine and berberine improves cardiac function in rats with coronary microembolization

AIM

We have shown that a combination of ligustrazine and berberine produces more effective inhibition on platelet activation and inflammatory reactions in rat acute myocardial infarction compared with either agent alone. In this study we evaluated the beneficial effects of a combination of ligustrazine and berberine in a rat model of coronary microembolization (CME).

METHODS

SD rats were treated with ligustrazine, berberine, ligustrazine+berberine, or clopidogrel for 2 weeks. When the treatment completed, CME was induced by injection of sodium laurate into the left ventricular, while obstructing the ascending aorta. All rats were intubated for hemodynamic measurements. Blood samples were collected for biochemical analyses, flow cytometry, and ELISAs. Heart tissues were isolated for histopathology and subsequent protein analyses.

RESULTS

Pretreatment with the combination of ligustrazine (27 mg·kg(-1)·d(-1)) and berberine (90 mg·kg(-1)·d(-1)) significantly improved cardiac function, and decreased myocardial necrosis, inflammatory cell infiltration, microthrombosis and serum CK-MB levels in CME rats. In addition, this combination significantly decreased plasma ET-1 levels and von Willebrand factor, inhibited ADP-induced platelet activation, and reduced TNFα, IL-1β, ICAM-1 and RANTES levels in serum and heart tissues. The protective effects of this combination were more prominent than those of ligustrazine or berberine alone, but comparable to those of a positive control clopidogrel (6.75 mg·kg(-1)·d(-1)).

CONCLUSION

The combination of ligustrazine and berberine significantly improved cardiac function in rat CME model via a mechanism involving antiplatelet and anti-inflammatory effects.

The effects of nicorandil on microvascular function in patients with ST segment elevation myocardial infarction undergoing primary PCI

Background

Nicorandil, as a selective potassium channel opener, has dual action including coronary and peripheral vasodilatation and cardioprotective effect through ischemic preconditioning. Considering those characteristics, nicorandil was suggested to reduce the degree of microvascular dysfunction.

Methods

Thirty-two patients with ST-elevation myocardial infarction undergoing primary percutaneous coronary intervention (pPCI) were included in the study. Index of microvascular resistance (IMR) was measured in all patients immediatelly after pPCI before the after administration of Nicorandil. ST segment resolution was monitored before intervention and 60 min after terminating the procedure. Echocardiographic evaluation of myocardial function and transthoracic Doppler derived Coronary flow reserve (CFR) of infarct related artery (IRA) was performed during hospitalization and 3 months later.

Results

IMR was significantly lower after administration of Nicorandil (9.9 ± 3.7 vs. 14.1 ± 5.1, p < 0.001). There was significant difference in ST segment elevation before and after primary PCI with administration of Nicorandil (6.9 ± 3.7 mm vs. 1.6 ± 1.6 mm, p < 0.001). Transthoracic Doppler CFR measurement improved after 3 months (2.69 ± 0.38 vs. 2.92 ± 0.54, p = 0.021), as well as WMSI (1.14 ± 0.17 vs. 1.07 ± 0.09, p = 0.004).

Conclusion

Intracoronary Nicorandil administration after primary PCI significantly decreases IMR, resulting in improved CFR and ventricular function in patients with STEMI undergoing primary PCI.

Trimetazidine pretreatment inhibits myocardial apoptosis and improves cardiac function in a Swine model of coronary microembolization

OBJECTIVE

Trimetazidine (TMZ) is a well-known anti-ischemic agent; however, its efficacy and mechanism of cardioprotection on coronary microembolization (CME) are largely unknown. The present study was undertaken to determine whether TMZ pretreatment could attenuate myocardial apoptosis and improve cardiac function in a swine model of CME.

METHODS

Fifteen swine were randomly and equally divided into a sham-operated (control) group, CME group and CME plus TMZ (TMZ) group. CME was induced by injecting inert plastic microspheres (42 μm in diameter) into the left anterior descending artery. For the control group, the same dose of normal saline was substituted for the microspheres, and the TMZ group was pretreated with TMZ 30 min before microsphere injection. Cardiac function was assessed by echocardiography, myocardial apoptosis was detected by TUNEL staining, and the expression levels of cleaved caspase-9/3 were measured by Western blot 12 h after operation.

RESULTS

Compared to the control group, cardiac function in the CME group was significantly decreased (p < 0.05); however, TMZ pretreatment showed significantly improved cardiac function as compared to the CME group (p < 0.05). The myocardial apoptotic rate and the expression levels of cleaved caspase-9/3 increased remarkably in CME group as compared with the control group (p < 0.001). Again, TMZ pretreatment significantly reduced the apoptotic rate and also the expression levels of cleaved caspase-9/3 (p < 0.001).

CONCLUSION

The present study demonstrated that TMZ pretreatment could significantly inhibit CME-induced myocardial apoptosis and improve cardiac function, and that the cardioprotective effect appeared to be mediated by the blockade of the mitochondrial apoptotic pathway. These results emphasize the importance of TMZ pretreatment in the therapy of CME-induced myocardial injury.

Nicorandil prevents microvascular dysfunction resulting from PCI in patients with stable angina pectoris: a randomised study

AIMS

Nicorandil, an ATP sensitive potassium channel opener, may reduce the incidence of microvascular dysfunction after percutaneous coronary intervention (PCI) by dilating coronary resistance vessels. The aim of the study was evaluation of the impact of the administration of intravenous nicorandil on measuring the index of microcirculatory resistance (IMR) in PCI to patients with stable angina pectoris (SAP).

METHODS AND RESULTS

Intravascular ultrasound (IVUS), fractional flow reserve (FFR), IMR and blood examination (CK-MB), cardiac troponin I (cTnI) immediately post-PCI (and 24 hours later) were performed in 62 consecutive patients with SAP undergoing PCI. FFR and IMR were measured simultaneously with a single coronary pressure wire. IMR was defined as Pd/coronary flow (or Pd* mean transit time) at peak hyperaemia. Patients were randomised to the control (n=29), or nicorandil group (n=33). In the nicorandil group, nicorandil was intravenously administered as a 6 mg bolus injection just before PCI and as a constant infusion at 6 mg/hour for 24 hours thereafter. All volumetric IVUS parameters and FFR were similar between the two groups both pre- and post-PCI. However, IMR immediately post-PCI and cTnI 24 hours post-PCI were significantly higher in the control group compared to the nicorandil group (IMR: 25.4±12.1 vs. 17.9±9.1 units, and cTnI: 0.21±0.13 vs. 0.12±0.08 ng/mL, for control vs. nicorandil). The incidence for cTnI elevation more than fivefold the normal range (>0.20 ng/mL) was significantly larger in the control group than in the nicorandil group (41% vs. 12%, p<0.01). Additionally, the control group showed a closer correlation between plaque volume reduction during stenting as assessed by volumetric IVUS, and cTnI elevation than the nicorandil group (r=0.55 vs. 0.42, p<0.001 for control vs. nicorandil).

CONCLUSIONS

In patients undergoing successful coronary stenting for stable angina, administration of nicorandil is associated with reduced microvascular dysfunction induced by PCI.

Effects of intravenous diltiazem in a rat model of experimental coronary thrombotic microembolism

The aim of this study was to assess the feasibility of evaluating the therapeutic effects of intravenous diltiazem in a newly established rat model of coronary thrombotic micro-embolism (CME). CME was induced by injecting 0.199 ml saline containing 5 mg of automicrothrombotic particulates (∼10 μm) into the aorta of Sprague Dawley rats. The injection was carried out over 10 sec using a tuberculin syringe with a 28-gauge needle. The CME model rats were randomly divided into untreated (CME, n=38) and diltiazem-treated (CME+DIL, n=38) groups. Diltiazem (1 mg/ml, 50 μg/min/kg) was intravenously injected using an infusion pump through the tail vein for 175 min, 5 min following the injection of the automicrothrombotic particulates. Hemodynamic measurements, echocardiography and pathohistological examinations were performed at various time-points (3 h, 24 h and 7 and 28 days) postoperatively. Arteriolar thrombosis, multifocal myocardial necrosis, inflammatory cell infiltration with markedly increased myocardial tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) expression, reduced left ventricular (LV) systolic function and increased plasma von Willebrand factor (vWF), endothelin-1 (ET-1) and serum c-troponin I (c-TnI) levels (indicating vascular endothelial injury and myocardial necrosis) were observed in the CME model rats. These pathological responses in CME rats were partly attenuated by intravenous diltiazem treatment. The present CME model is suitable for evaluating the therapeutic effects of intravenous diltiazem; intravenous diltiazem treatment significantly improved cardiac function through alleviating inflammatory responses and microvascular thrombotic injury in this rat model of CME.

MRI quantification of left ventricular function in microinfarct versus large infarct in swine model

To quantify, using MRI, the acute impacts of defined volume and sizes of coronary microemboli on myocardial viability and left ventricular (LV) function and to use LAD occlusion/reperfusion, as a reference. A total of 28 farm pigs were used in this study. Eight animals were used as controls. Successful coronary interventions were performed under X-ray fluoroscopy in 16 pigs to induce microinfarct (delivery of 16 mm(3) of 40-120 μm) and large infarct (90 min LAD occlusion/reperfusion). On day 3, animals were imaged using contrast enhanced (in beating and non-beating hearts) and cine MRI for evaluating LV viability and function, respectively. Microscopy and cardiac injury enzymes were used to confirm the presence of necrosis. Myocardial damage was smaller after microembolization than occlusion/reperfusion (6.5 ± 0.6%LV mass vs. 12.6 ± 1.2%, P < 0.001). The increase in LV end-systolic volume and decreases in ejection fraction, cardiac output and regional systolic wall thickening, however, were comparable between groups, but significantly differed from controls. MRI also demonstrated microvascular obstruction after microembolization and occlusion/reperfusion as hyperenhanced and hypoenhanced regions, respectively. Microscopic examination revealed patchy necrosis, inflammatory cell infiltration, but no intramyocardial hemorrhage after microembolization and extensive intramyocardial hemorrhage and transmural damage in the occlusion/reperfusion group. Cardiac injury enzymes confirmed presence of myocardial damage in animals with interventions. Coronary microemboli have acute impact on LV function compared to control animals. Despite the difference in myocardial damage, global and regional LV dysfunction after microembolization was comparable to occlusion/reperfusion. This MR study suggests that the pattern of myocardial damage plays a role in LV dysfunction.

Detection of coronary microembolization by Doppler ultrasound in patients with stable angina pectoris during percutaneous coronary interventions under an adjunctive antithrombotic therapy with abciximab: design and rationale of the High Intensity Transient Signals ReoPro (HITS-RP) study

Background

Embolization of atherosclerotic debris from the rupture of a vulnerable atherosclerotic plaque occurs iatrogenically during percutaneous coronary interventions (PCI) and can induce myocardial necrosis. These microembolizations are detected as high intensity transient signals (HITS) using intracoronary Doppler technology.

Presentation of the hypothesis

In the presented study we will test if abciximab (ReoPro®) infusion reduces high intensity transient signals in patients with stable angina pectoris undergoing PCI in comparison to standard therapy alone.

Testing the hypothesis

The High Intensity Transient Signals ReoPro® (HITS-RP) study will enroll 60 patients. It is a prospective, single center, randomized, double-blinded, controlled trial. The study is designed to compare the efficacy of intravenous abciximab administration for reduction of microembolization during elective PCI. Patients will be randomized in a 1:1 fashion to abciximab or placebo infusion. The primary end point of the HITS-RP-Study is the number of HITS during PCI measured by intracoronary Doppler wire. Secondary endpoints are bleeding complications, elevation of cardiac biomarkers or ECG changes after percutaneous coronary interventions, changes in coronary flow velocity reserve, hs-CRP elevation, any major adverse cardio-vascular event during one month follow-up.

Implications of the hypothesis

The HITS-RP-Study addresses important questions regarding the efficacy of intravenous abciximab administration in reducing microembolization and periprocedural complications in stable angina pectoris patients undergoing PCI.

Trial registration

The trial is registered under http://www.drks-neu.uniklinik-freiburg.de/drks_web/:DRKS00000603.

Peri-interventional coronary vasomotion

A percutaneous coronary intervention (PCI) is a unique condition to study the effects of ischemia and reperfusion in patients with severe coronary atherosclerosis when coronary vasomotor function is compromised by loss of endothelial and autoregulatory vasodilation. We studied the effects of intracoronary non-selective α-, as well as selective α(1)- and α(2)-blockade in counteracting the observed vasoconstriction in patients with stable and unstable angina and in patients with acute myocardial infarction. Coronary vasoconstriction in our studies was a diffuse phenomenon and involved not only the culprit lesion but also vessels with angiographically not visible plaques. Post-PCI vasoconstriction was reflected by increased coronary vascular resistance and associated with decreased LV-function. α (1)-Blockade with urapidil dilated epicardial coronary arteries, improved coronary flow reserve and counteracted LV dysfunction. Non-selective α-blockade with phentolamine induced epicardial and microvascular dilation, while selective α(2)-blockade with yohimbine had only minor vasodilator and functional effects. Intracoronary α-blockade also attenuated the no-reflow phenomenon following primary PCI. This article is part of a Special Issue entitled "Coronary Blood Flow".

Lessons from human coronary aspirate

The interventional implantation of a stent into an atherosclerotic coronary artery is a unique and paradigmatic scenario of plaque rupture in humans. The use of protection devices not only prevents the released plaque particles and the superimposed thrombotic material from being washed and embolized into the coronary microcirculation of the individual patient, but permits also the retrieval and ex vivo analysis of particulate plaque debris and soluble substances. The particulate debris comprises typical cholesterol crystals, foam cells, hyalin material and calcium deposits from the atheroma as well as platelets and coagulation material; soluble substances include vasoconstrictors, such as serotonin and thromboxane, as well as inflammatory mediators, such as TNFα which amplifies vasoconstriction by inducing endothelial dysfunction. The vasoconstriction observed in a bioassay ex vivo correlates to clinical symptoms, angiographic stenosis and plaque burden, as assessed by intravascular ultrasound. The release of TNFα into the aspirate correlates to restenosis. Detailed analysis of the human coronary aspirate may promote a better understanding of the pathophysiology of the vulnerable atherosclerotic plaque and help to better antagonize the microvascular consequences of coronary microembolization, including the no reflow phenomenon. This article is part of a Special Issue entitled "Coronary Blood Flow."

A rabbit model of thrombosis on atherosclerotic lesions

Thrombus formation on a disrupted atherosclerotic plaque is a key event that leads to atherothrombosis. Because thrombus is induced by chemical or physical injury of normal arteries in most animal models of thrombosis, the mechanisms of thrombogenesis and thrombus growth in atherosclerotic vessels should be investigated in diseased arteries of appropriate models. Pathological findings of human atherothrombosis suggest that tissue factor, an initiator of the coagulation cascade, significantly affects enhanced platelet aggregation and fibrin formation after plaque disruption. We established a rabbit model of atherothrombosis based on human pathology in which differences in thrombus formation between normal and atherosclerotic arteries, factors contributing to thrombus growth, and mechanisms of plaque erosion can be investigated. Emerging transgenic and stem cell technologies should also provide an invaluable rabbit experimental model in the near future.

Stents and statins: history, clinical outcomes and mechanisms

The 1980s witnessed the inception of both stents and 3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitors (statins). While they evolved separately, it was soon realized that they each offered a unique and powerful mechanism for targeting the major offender in cardiovascular disease, namely atherosclerosis. Coincidentally, the first statin was approved by the US FDA in 1987, the same year that the coronary stent was conceived. Since that time, stents and statins have revolutionized the field of cardiovascular medicine and their paths have been intertwined. Several pivotal randomized clinical trials have established statins as an effective therapy for improving clinical outcomes after percutaneous coronary intervention (PCI) among patients presenting with stable coronary artery disease and acute coronary syndromes. In addition, chronic statin therapy and acute loading of statins prior to PCI has consistently been shown to limit periprocedural myocardial necrosis. The mechanism for improved clinical outcomes with statins has clearly been associated with statin-induced reductions in LDL. In addition, statins may also exert 'pleiotropic' effects, independent of LDL lowering, that might counteract the inflammatory and prothrombotic mileu created with PCI. This article provides a brief historical perspective of the evolution of the use of statins and stents in patients with coronary artery disease, an evaluation of the available clinical data supporting the use of statins in patients undergoing PCI across a wide spectrum of clinical scenarios, and a discussion of the potential mechanisms of the benefit of statins in these patients.

High-risk PCI in acute coronary syndromes with Impella LP 2.5 device support

OBJECTIVES

To evaluate feasibility, safety, efficacy as well as acute and short-term outcome of hemodynamically supported percutaneous coronary intervention (PCI) by a percutaneous, catheter-based left ventricular assist device (LVAD) (Impella LP 2.5, Abiomed Europe GmbH, Aachen, Germany) in a high-risk patient population with acute coronary syndrome.

BACKGROUND

Although hemodynamic support by intraaortic balloon pump favorably affects myocardial oxygen supply and demand, it has modest effects on cardiac output, providing passive support only. In contrast, the Impella LP 2.5 microaxial pump, which is placed within the left ventricular outflow tract and actively ejects blood into the ascending aorta, might offer additional hemodynamic support and thereby procedural safety during PCI.

METHODS

Thirty-eight consecutive high-risk patients (mean age, 69.7 ± 10.3 years, logistic EuroSCORE, 22.4 ± 14.9%) with unstable angina pectoris or non-ST-segment elevation myocardial infarction and severe three-vessel-disease were included in the study. Clinical and laboratory examinations were performed at baseline as well as at 6, 24 and 48 h after the procedure and 30 days after discharge.

RESULTS

Device insertion and explantation was feasible in all patients without vascular complications and continuous hemodynamic stability was obtained during PCI. PCI was uneventfully performed in all but one patient for technical reasons. One non procedure-related death occurred 7 days after the intervention, accounting for a total 30-day mortality of 2.86%. Other major cardiac or cerebrovascular events did not occur.

CONCLUSIONS

LVAD support using a percutaneous microaxial flow pump is a promising and safe approach for high-risk PCI providing good short-term results.

Thrombus aspiration in a series of patients with stable or unstable angina pectoris and lesion-site thrombus formation

Background. In acute myocardial infarction, thrombus aspiration prior to percutaneous coronary interventions (PCI) is often beneficial, but this approach has never been studied in patients without acute myocardial infarction. The aim of this retrospective study is to shed light on that topic based on our initial experience with manual thrombus aspiration in patients with stable or unstable angina pectoris and angiographic evidence of lesion-site thrombus. Methods. We assessed the feasibility (thrombus aspiration without predilatation) of this approach; in addition, we determined angiographic coronary flow and myocardial blush grade. Results. During 33 months in which a total of 4725 PCI were performed in our centre, manual thrombus aspiration was attempted in 14 patients with stable or unstable angina pectoris with angiographic evidence of thrombus. In nine of these 14 patients, the aspiration catheter could be advanced into the lesion without predilatation; in eight patients visible thrombus was obtained. The corrected TIMI frame count improved during the entire interventional procedure (21.1±11.2 vs. 12.8±5.9 frames; p=0.015). Myocardial blush grade, which overall improved during PCI (p<0.001), tended to show greater improvement in patients in whom thrombus aspiration could be achieved (1.6±0.9 vs. 0.7±0.5; p=0.06). Conclusions. Preliminary evidence suggests that manual thrombus aspiration may occasionally be considered in selected patients without acute myocardial infarction but with angiographic evidence of lesion-site thrombus. Nevertheless, prospective studies are required to clearly define the role of this approach in clinical practice. (Neth Heart J 2010;18:423-9.).

Impact of thrombus aspiration use and direct stenting on final myocardial blush score in patients presenting with ST-elevation myocardial infarction

BACKGROUND

Many studies have reported that low final thrombolysis in myocardial infarction (TIMI) flow and/or myocardial blush grade (MBG) are independent predictors of mortality in patients with ST-elevation myocardial infarction (STEMI). In addition, distal coronary embolization is a major pitfall of conventional percutaneous coronary intervention (PCI) in such a context.

AIM

This study aimed to assess the impact of thrombus aspiration (TA) use before primary PCI on final myocardial reperfusion in patients presenting with STEMI.

METHODS

From January to December 2006, 100 patients presenting with STEMI in our catheterization laboratory were considered for the present study. During this time period, 50 patients underwent TA before primary PCI for treatment of STEMI and were then matched 1:1 to 50 controls who underwent conventional primary PCI for treatment of STEMI without TA. Patients of the control group were chosen after matching on age+/-3 years, sex, history of diabetes, and distribution of the infarct related coronary artery during the same period.

RESULTS

Baseline clinical characteristics, initial TIMI flow and initial MBG of both groups were similar. There was a trend for a better final TIMI flow in the group with TA and the final MBG was significantly improved in the group with TA compared to the group without TA: final MBG of two or three in 70% versus 30% of the cases (P=.001). In addition, direct stenting was significantly more often used in the TA group (92% versus 64%, P=.001). There were four patients with evident distal embolizations in the group without TA and none in the group with TA.

CONCLUSION

TA use before primary PCI for STEMI treatment resulted in improved final myocardial reperfusion. Of importance, TA use may have led to a better choice of the stent size and more frequent direct stenting. This benefit may directly improve patient outcomes.

Microvascular obstruction: underlying pathophysiology and clinical diagnosis

Successful restoration of epicardial coronary artery patency after prolonged occlusion might result in microvascular obstruction (MVO) and is observed both experimentally as well as clinically. In reperfused myocardium, myocytes appear edematous and swollen from osmotic overload. Endothelial cell changes usually accompany the alterations seen in myocytes but lag behind myocardial cell injury. Endothelial cells become voluminous, with large intraluminal endothelial protrusions into the vascular lumen, and together with swollen surrounding myocytes occlude capillaries. The infiltration and activation of neutrophils and platelets and the deposition of fibrin also play an important role in reperfusion-induced microvascular damage and obstruction. In addition to these ischemia-reperfusion-related events, coronary microembolization of atherosclerotic debris after percutaneous coronary intervention is responsible for a substantial part of clinically observed MVO. Microvascular flow after reperfusion is spatially and temporally complex. Regions of hyperemia, impaired vasodilatory flow reserve and very low flow coexist and these perfusion patterns vary over time as a result of reperfusion injury. The MVO first appears centrally in the infarct core extending toward the epicardium over time. Accurate detection of MVO is crucial, because it is independently associated with adverse ventricular remodeling and patient prognosis. Several techniques (coronary angiography, myocardial contrast echocardiography, cardiovascular magnetic resonance imaging, electrocardiography) measuring slightly different biological and functional parameters are used clinically and experimentally. Currently there is no consensus as to how and when MVO should be evaluated after acute myocardial infarction.

Non-ST-elevation acute myocardial infarction with normal coronary arteries: predictors and prognosis

INTRODUCTION AND OBJECTIVES

Occasionally, coronary arteries without significant stenosis are observed during invasive treatment of acute non-ST-elevation myocardial infarction (NSTEMI). The aim was to investigate predictive factors and prognosis in these patients.

METHODS

The study involved 504 patients admitted for NSTEMI who underwent cardiac catheterization. The primary end-point was the observation of coronary arteries without significant stenosis, and the secondary end-point was death or myocardial infarction within a median of 3 years. In evaluating the secondary end-point, a control group of 160 patients with a normal troponin level and no significant coronary artery stenosis who were admitted for chest pain during the same period was included.

RESULTS

Overall, 64 patients (13%) had coronary arteries without significant lesions. The predictors were: female sex (odds ratio [OR]=6.6; P=.0001), age <55 years (OR=3.0; P=.001), and the absence of diabetes (OR=2.4, P=.02), previous antiplatelet treatment (OR=3.9, P=.007) or ST-segment depression (OR=2.4, P=.008). The composite variable of female sex plus at least two additional predictive factors had a specificity of 85% and a sensitivity of 53% for coronary angiography showing no significant stenosis. The absence of coronary artery stenosis decreased the probability of death or myocardial infarction during follow-up (hazard ratio=0.3, 95% confidence interval, 0.2-0.9; P=.03). Among all patients without significant stenosis (n=224), there was no difference in the event rate between those with elevated and normal troponin levels.

CONCLUSIONS

In NSTEMI, female sex, age <55 years and the absence of diabetes, previous antiplatelet treatment or ST-segment depression were all associated with coronary angiography showing no significant stenosis. The long-term prognosis in these patients was good.

Non-ST-elevation acute myocardial infarction with normal coronary arteries: predictors and prognosis

INTRODUCTION AND OBJECTIVES

Occasionally, coronary arteries without significant stenosis are observed during invasive treatment of acute non-ST-elevation myocardial infarction (NSTEMI). The aim was to investigate predictive factors and prognosis in these patients.

METHODS

The study involved 504 patients admitted for NSTEMI who underwent cardiac catheterization. The primary end-point was the observation of coronary arteries without significant stenosis, and the secondary end-point was death or myocardial infarction within a median of 3 years. In evaluating the secondary end-point, a control group of 160 patients with a normal troponin level and no significant coronary artery stenosis who were admitted for chest pain during the same period was included.

RESULTS

Overall, 64 patients (13%) had coronary arteries without significant lesions. The predictors were: female sex (odds ratio [OR]=6.6; P=.0001), age <55 years (OR=3.0; P=.001), and the absence of diabetes (OR=2.4, P=.02), previous antiplatelet treatment (OR=3.9, P=.007) or ST-segment depression (OR=2.4, P=.008). The composite variable of female sex plus at least two additional predictive factors had a specificity of 85% and a sensitivity of 53% for coronary angiography showing no significant stenosis. The absence of coronary artery stenosis decreased the probability of death or myocardial infarction during follow-up (hazard ratio=0.3, 95% confidence interval, 0.2-0.9; P=.03). Among all patients without significant stenosis (n=224), there was no difference in the event rate between those with elevated and normal troponin levels.

CONCLUSIONS

In NSTEMI, female sex, age <55 years and the absence of diabetes, previous antiplatelet treatment or ST-segment depression were all associated with coronary angiography showing no significant stenosis. The long-term prognosis in these patients was good.

Tranilast stabilizes the accumulation and degranulation of resident mast cells while reducing cardiomyocyte apoptosis in a swine model of coronary microembolisation

1. Coronary microembolisation (CME) is associated with progressive myocardial dysfunction, and mast cells (MC) might have an important role in myocardial apoptosis after CME. We investigated whether the MC stabilizer tranilast suppresses the accumulation and degranulation of MC while reducing cardiomyocyte apoptosis after CME. 2. We induced CME in miniswine by selective infusion of 15 x 10(4) microspheres (diameter 45 microm) into the left anterior descending artery. Some CME-induced miniswine were treated with the MC stabilizer tranilast (50 mg/kg, p.o., b.d.) beginning 2 weeks before CME, and thereafter throughout the experimental period; others received tranilast without CME; and sham-operated animals without CME served as controls. After 30 days, we assessed cardiomyocyte apoptosis by TUNEL assay and by the total number of MC and the number of degranulating MC using histology and transmission electron microscopy. The wall motion score index and left ventricular ejection fraction were studied by dobutamine stress echocardiography. 3. Coronary microembolisation was associated with increases in the total number of MC, the number of degranulating MC, and myocyte apoptosis. The number of total MC and degranulating MC and apoptotic cardiomyocytes over the anterior embolized myocardium after CME were significantly higher than those over the posterior control myocardium and anterior segments per animal without CME (P < 0.01). Tranilast administration to CME miniswine suppressed cardiomyocyte apoptosis while maintaining regional and global function, which was associated with reductions in the accumulation and degranulation of MC. 4. These findings suggest that tranilast suppresses the accumulation and degranulation of MC while reducing cardiomyocyte apoptosis after CME.

Microemboli and microvascular obstruction in acute coronary thrombosis and sudden coronary death: relation to epicardial plaque histopathology

OBJECTIVES

This study examined myocardial microvascular emboli and obstruction, and related these to plaque in the epicardial coronary arteries supplying the affected microvessels.

BACKGROUND

Epicardial coronary thrombosis often causes microemboli and microvascular obstruction. The consequences of myocardial microvessel obstruction and myocyte necrosis are substantial, yet histopathologic characterization of epicardial coronary artery plaque has been incompletely characterized. This study examined myocardial microvascular emboli, and related these to plaque in the coronary arteries supplying the microvessels.

METHODS

Hearts from sudden coronary death patients underwent examination for coronary artery plaque type and cardiac microemboli.

RESULTS

Forty-four hearts were available for evaluation. Mean age at death was 51 +/- 15 years. Coronary artery analysis found 26 plaque ruptures and 21 erosions, and a mean of 4.5 microemboli per heart. Microemboli and microvascular obstruction occurred most often from eroded plaques. Microemboli and occluded intramyocardial vessels were most common in the left anterior descending coronary artery, and all vessels contained fibrin and platelets. Mean stenoses of the culprit lesion was 74% in those with emboli and 75% in those without (p = NS). Intramyocardial microemboli were more common in plaque erosion than in rupture. Microvessels <200 mum were most often those that were occluded.

CONCLUSIONS

Microemboli and microvascular obstruction are common in patients dying of acute coronary thrombosis. Plaque erosion is more likely to cause emboli in vessels <200 mum. These emboli and microvessel obstruction have a prominent clinical role since myonecrosis is often associated with these findings.

Coronary microembolization: from bedside to bench and back to bedside

Coronary microembolization from the erosion or rupture of a vulnerable atherosclerotic plaque occurs spontaneously in acute coronary syndromes and iatrogenically during percutaneous coronary interventions. Typical consequences of coronary microembolization are microinfarcts with an inflammatory response, contractile dysfunction, and reduced coronary reserve. Apart from transient elevations of creatine kinase and troponin, microemboli can be visualized by intracoronary Doppler and the resulting microinfarcts by late-enhancement nuclear magnetic resonance. Statins, antiplatelet agents, and coronary vasodilators protect against microembolization and microinfarction when started before percutaneous coronary interventions. Distal protection devices can retrieve atherothrombotic debris and prevent its embolization into the microcirculation, but their effect on clinical outcome has been disappointing so far, except for saphenous vein bypass grafts. Devices for aspiration of thrombi and thrombus-derived vasoconstrictor, thrombogenic, and inflammatory substances, however, reduce thrombus burden, improve perfusion, and provide protection in patients with acute myocardial infarction.

Noncalcified atherosclerotic plaque burden at coronary CT angiography: a better predictor of ischemia at stress myocardial perfusion imaging than calcium score and stenosis severity

OBJECTIVE

The purpose of this study was to examine the relation between the coronary CT angiographic findings of calcified and noncalcified plaque burden and stenosis severity and the myocardial perfusion imaging finding of ischemia.

MATERIALS AND METHODS

Seventy-two patients (41 men, 31 women; mean age, 56 years) underwent coronary CT angiography and stress-rest SPECT myocardial perfusion imaging. Calcium scoring was performed. Coronary CT angiograms were analyzed for stenosis and noncalcified or mixed plaque. A plaque analysis tool was used to calculate the volume of noncalcified plaque components. SPECT images were analyzed for perfusion defects. Data were analyzed per patient and per vessel.

RESULTS

A total of 53 purely noncalcified, 50 mixed, and 201 purely calcified plaques were detected. Forty-five stenoses were rated > or = 50%, 19 of those being > or = 70%. Myocardial perfusion imaging depicted perfusion defects in 37 vessels (13%) in 24 patients (18 reversible, 19 fixed defects). Vessels with > or = 50% stenosis had significantly (p = 0.0009) more perfusion defects in their supplied territories (11 with, 22 without perfusion defects) than did vessels without significant lesions (26 with, 229 without perfusion defects). In vessel-based analysis, the sensitivity of coronary CT angiography in prediction of any perfusion defect on myocardial perfusion images was 30% with 91% specificity, 33% positive predictive value, and 90% negative predictive value. Between vessels with and those without perfusion defects, there was no significant difference in Agatston or calcium volume score (p = 0.25), but there was a significant difference in noncalcified plaque volume (44 +/- 77 vs 19 +/- 58 mm(3); p = 0.03). Multiple stepwise regression analysis showed noncalcified plaque volume was the only significant predictor of ischemia (p = 0.01).

CONCLUSION

At coronary CT angiography, noncalcified plaque burden is a better predictor of the finding of myocardial ischemia at stress myocardial perfusion imaging than are calcium score and degree of stenosis.

Systematic analysis of functional and structural changes after coronary microembolization: a cardiac magnetic resonance imaging study

OBJECTIVES

Our study aimed to detect the morphological und functional effects of coronary microembolization (ME) in vivo by cardiac magnetic resonance (CMR) imaging in an established experimental animal model.

BACKGROUND

Post-mortem morphological alterations of coronary ME include perifocal inflammatory edema and focal microinfarcts. Clinically, the detection of ME after successful coronary interventions identifies a population with a worse long-term prognosis.

METHODS

In 18 minipigs, ME was performed by intracoronary infusion of microspheres followed by repetitive in vivo imaging on a 1.5-T MR system from 30 min to 8 h after ME. Additionally, corresponding ex vivo CMR imaging and histomorphology were performed.

RESULTS

Cine CMR imaging demonstrated a time-dependent increase of wall motion abnormalities from 9 of 18 animals after 30 min to all animals after 8 h (0.5 h, 50%; 2 h, 78%; 4 h, 75%; 8 h, 100%). Whereas T2 images were negative 30 min after ME, 4 of 18 animals showed myocardial edema at follow-up (0.5 h, 0%; 2 h, 6%; 4 h, 25%; 8 h, 17%). In vivo late gadolinium enhancement (LGE) was observed in none of the animals after 30 min, but in 33%, 50%, and 83% of animals at 2 h, 4 h, and 8 h, respectively, after ME. Ex vivo CMR imaging showed patchy areas of LGE in all but 1 animal (2 h, 83%; 4 h, 100%; 8 h, 100%). A significant correlation was seen between the maximum troponin I level and LGE in vivo (r = 0.63) and the spatial extent of ex vivo LGE (r = 0.76).

CONCLUSIONS

Our results show that in vivo contrast-enhanced CMR imaging allows us to detect functional and structural myocardial changes after ME with a high sensitivity. Ex vivo, the pattern of LGE of high-resolution, contrast-enhanced CMR imaging is different from the well-known pattern of LGE in compact myocardial damage. Thus, improvements in spatial resolution are thought to be necessary to improve its ability to visualize ME-induced structural alterations even in vivo.