Detection of Coronary Microembolization by Doppler Ultrasound in Patients With Stable Angina Pectoris Undergoing Elective Percutaneous Coronary Interventions

Effects of Remote Ischaemic Conditioning in Stable and Unstable Angina Patients Undergoing Percutaneous Coronary Intervention: A Systematic Review and Meta-Analysis

AIM

Type 4a myocardial infarction (T4aMI), defined as myocardial injury associated with percutaneous coronary intervention (PCI), is associated with a poor prognosis and there is conflicting evidence regarding the effectiveness of remote ischaemic conditioning (RIC) in its prevention. This review aimed to determine the effect of RIC on stable and unstable angina patients.

METHOD

A systematic review was conducted in PubMed and Central database. Outcome measures were: changes in peak troponin, creatine kinase myocardial band (CKMB), C-reactive protein (CRP) level, incidence of T4aMI, and major adverse cardiovascular event (MACE). Data were meta-analysed and reported as standardised mean difference (SMD) and odds ratio (OR). Risk of bias was assessed with the Risk of Bias 2 (RoB2) tool.

RESULTS

Fifteen studies with no significant risk of bias were included. Peak troponin level was reduced in the RIC group, particularly after excluding a study with low statin use, while CKMB and CRP levels resulted in a non-significant SMD between the groups. The incidence of T4aMI was significantly lower in the intervention group (OR 0.714; p=0.026); this finding was also seen in subgroups of elective PCI, pre-conditioning, and high statin use. Incidence of MACE also only reached statistically significant protective effects with OR <1 in similar subgroups. No substantial heterogeneity was found and the funnel plot did not show publication bias.

CONCLUSION

Remote ischaemic conditioning in elective PCI patients has been proven to be potentially beneficial in reducing peak troponin levels and risk of T4aMI and MACE.

Resveratrol pretreatment alleviates NLRP3 inflammasome-mediated cardiomyocyte pyroptosis by targeting TLR4/MyD88/NF-κB signaling cascade in coronary microembolization-induced myocardial damage

Percutaneous coronary intervention and acute coronary syndrome are both closely tied to the frequently occurring complication of coronary microembolization (CME). Resveratrol (RES) has been shown to have a substantial cardioprotective influence in a variety of cardiac diseases, though its function and potential mechanistic involvement in CME are still unclear. The forty Sprague-Dawley rats were divided into four groups randomly: CME, CME + RES (25 mg/kg), CME + RES (50 mg/kg), and sham (10 rats per group). The CME model was developed. Echocardiography, levels of myocardial injury markers in the serum, and histopathology of the myocardium were used to assess the function of the cardiac muscle. For the detection of the signaling of TLR4/MyD88/NF-κB along with the expression of pyroptosis-related molecules, ELISA, qRT-PCR, immunofluorescence, and Western blotting were used, among other techniques. The findings revealed that myocardial injury and pyroptosis occurred in the myocardium following CME, with a decreased function of cardiac, increased levels of serum myocardial injury markers, increased area of microinfarct, as well as a rise in the expression levels of pyroptosis-related molecules. In addition to this, pretreatment with resveratrol reduced the severity of myocardial injury after CME by improving cardiac dysfunction, decreasing serum myocardial injury markers, decreasing microinfarct area, and decreasing cardiomyocyte pyroptosis, primarily by blocking the signaling of TLR4/MyD88/NF-κB and also reducing the NLRP3 inflammasome activation. Resveratrol may be able to alleviate CME-induced myocardial pyroptosis and cardiac dysfunction by impeding the activation of NLRP3 inflammasome and the signaling pathway of TLR4/MyD88/NF-κB.

Tanshinone IIA reduces pyroptosis in rats with coronary microembolization by inhibiting the TLR4/MyD88/NF-κB/NLRP3 pathway

Pyroptosis is an inflammatory form of programmed cell death that is linked with invading intracellular pathogens. Cardiac pyroptosis has a significant role in coronary microembolization (CME), thus causing myocardial injury. Tanshinone IIA (Tan IIA) has powerful cardioprotective effects. Hence, this study aimed to identify the effect of Tan IIA on CME and its underlying mechanism. Forty Sprague–Dawley (SD) rats were randomly grouped into sham, CME, CME + low-dose Tan IIA, and CME + high-dose Tan IIA groups. Except for the sham group, polyethylene microspheres (42 µm) were injected to establish the CME model. The Tan-L and Tan-H groups received intraperitoneal Tan IIA for 7 days before CME. After CME, cardiac function, myocardial histopathology, and serum myocardial injury markers were assessed. The expression of pyroptosis-associated molecules and TLR4/MyD88/NF-κB/NLRP3 cascade was evaluated by qRT-PCR, Western blotting, ELISA, and IHC. Relative to the sham group, CME group's cardiac functions were significantly reduced, with a high level of serum myocardial injury markers, and microinfarct area. Also, the levels of caspase-1 p20, GSDMD-N, IL-18, IL-1β, TLR4, MyD88, p-NF-κB p65, NLRP3, and ASC expression were increased. Relative to the CME group, the Tan-H and Tan-L groups had considerably improved cardiac functions, with a considerably low level of serum myocardial injury markers and microinfarct area. Tan IIA can reduce the levels of pyroptosis-associated mRNA and protein, which may be caused by inhibiting TLR4/MyD88/NF-κB/NLRP3 cascade. In conclusion, Tanshinone IIA can suppress cardiomyocyte pyroptosis probably through modulating the TLR4/MyD88/NF-κB/NLRP3 cascade, lowering cardiac dysfunction, and myocardial damage.

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.

miR-200a-3p Attenuates Coronary Microembolization-Induced Myocardial Injury in Rats by Inhibiting TXNIP/NLRP3-Mediated Cardiomyocyte Pyroptosis

Coronary microembolization (CME) commonly develops as a complication after percutaneous coronary intervention (PCI), and associated inflammation is a leading driver of myocardial damage. Cardiomyocyte loss in the context of ischemic myocardial disease has been linked to inflammatory pyroptotic cell death. Additionally, miR-200a-3p dysregulation has been linked to myocardial ischemia-reperfusion and many other pathological conditions. However, how miR-200a-3p impacts cardiomyocyte pyroptosis in the context of CME remains to be assessed. Herein, a rat model of CME was established via the injection of microembolic spheres into the left ventricle. When myocardial tissue samples from these rats were analyzed, miR-200a-3p levels were markedly decreased, whereas thioredoxin-interacting protein (TXNIP) levels were increased. The ability of miR-200a-3p to directly target TXNIP and to control its expression was confirmed via dual-luciferase reporter assay. Adeno-associated virus serotype 9-pre-miR-200a-3p (AAV-miR-200a-3p) construct transfection was then employed as a means of upregulating this miRNA in CME model rats. Subsequent assays, including echocardiography, enzyme-linked immunosorbent assays (ELISAs), hematoxylin-eosin (H&E) staining, hematoxylin-basic fuchsin-picric acid (HBFP) staining, TdT-mediated dUTP nick-end labeling (TUNEL) staining, immunofluorescence staining, quantitative real-time polymerase chain reaction (qRT-PCR), and Western blotting revealed that miR-200a-3p overexpression inhibited cardiomyocyte pyroptosis and alleviated CME-induced myocardial injury by inhibiting the TXNIP/NOD-like receptor family pyrin domain-containing 3 (NLRP3) pathway. The ability of miR-200a-3p to protect against CME-induced myocardial injury thus highlights a novel approach to preventing or treating such myocardial damage in clinical settings.

Inflammation during Percutaneous Coronary Intervention-Prognostic Value, Mechanisms and Therapeutic Targets

Periprocedural myocardial injury and myocardial infarction (MI) are not infrequent complications of percutaneous coronary intervention (PCI) and are associated with greater short- and long-term mortality. There is an abundance of preclinical and observational data demonstrating that high levels of pre-, intra- and post-procedural inflammation are associated with a higher incidence of periprocedural myonecrosis as well as future ischaemic events, heart failure hospitalisations and cardiac-related mortality. Beyond inflammation associated with the underlying coronary pathology, PCI itself elicits an acute inflammatory response. PCI-induced inflammation is driven by a combination of direct endothelial damage, liberation of intra-plaque proinflammatory debris and reperfusion injury. Therefore, anti-inflammatory medications, such as colchicine, may provide a novel means of improving PCI outcomes in both the short- and long-term. This review summarises periprocedural MI epidemiology and pathophysiology, evaluates the prognostic value of pre-, intra- and post-procedural inflammation, dissects the mechanisms involved in the acute inflammatory response to PCI and discusses the potential for periprocedural anti-inflammatory treatment.

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.

Ischemic Heart Disease Pathophysiology Paradigms Overview: From Plaque Activation to Microvascular Dysfunction

Ischemic heart disease still represents a large burden on individuals and health care resources worldwide. By conventions, it is equated with atherosclerotic plaque due to flow-limiting obstruction in large-medium sized coronary arteries. However, clinical, angiographic and autoptic findings suggest a multifaceted pathophysiology for ischemic heart disease and just some cases are caused by severe or complicated atherosclerotic plaques. Currently there is no well-defined assessment of ischemic heart disease pathophysiology that satisfies all the observations and sometimes the underlying mechanism to everyday ischemic heart disease ward cases is misleading. In order to better examine this complicated disease and to provide future perspectives, it is important to know and analyze the pathophysiological mechanisms that underline it, because ischemic heart disease is not always determined by atherosclerotic plaque complication. Therefore, in order to have a more complete comprehension of ischemic heart disease we propose an overview of the available pathophysiological paradigms, from plaque activation to microvascular dysfunction.

A Contemporary Definition of Periprocedural Myocardial Injury After Percutaneous Coronary Intervention of Chronic Total Occlusions

OBJECTIVES

The aim of this study was to assess the prognostic impact of post-procedural troponin T increase and mortality in patients undergoing percutaneous coronary intervention (PCI) for chronic total occlusion (CTO) to define the threshold at which procedure-related myocardial injury drives mortality.

BACKGROUND

Coronary CTO recanalization represents the most technically challenging PCI. The complexity harbors a significant increased risk for complications with CTO PCI with compared with non-CTO PCI. However, there are evidenced biomarker cutoff levels that help identify those patients at risk for unfavorable clinical outcomes.

METHODS

A total of 3,712 consecutive patients undergoing PCI for at least 1 CTO lesion were enrolled, and comprehensive troponin T measurements were performed 6, 8, and 24 h after the procedure. All-cause mortality was defined as the primary study endpoint.

RESULTS

Using spline curve analysis, a more than 18-fold increase of troponin above the upper reference limit was significantly associated with mortality. In a Cox regression analysis, the crude hazard ratio was 2.32 (95% confidence interval: 1.83 to 2.93; p < 0.001) for a ≥18-fold increase compared with patients with post-procedural troponin increase <18-fold of the upper reference limit. Results remained virtually unchanged after bootstrap- or clinical confounder-based adjustment.

CONCLUSIONS

This large-scale outcome study demonstrates for the first time the prognostic value of post-procedural troponin T elevation after PCI in patients with CTOs. A threshold was defined for procedure-related myocardial injury in patients with CTOs to differentiate them from those without CTOs that may help guide post-procedural clinical care in this high-risk patient population.

Periprocedural Myocardial Injury: Pathophysiology, Prognosis, and Prevention

The definition and clinical implications of myocardial infarction occurring in the setting of percutaneous coronary intervention have been the subject of unresolved controversy. The definitions of periprocedural myocardial infarction (PMI) are many and have evolved over recent years. Additionally, the recent advancement of different imaging modalities has provided useful information on a patients' pre-procedural risk of myocardial infarction. Nonetheless, questions on the benefit of different approaches to prevent PMI and their practical implementation remain open. This review aims to address these questions and to provide a current and contemporary perspective.

Hypoxia-inducible factor-1α attenuates myocardial inflammatory injury in rats induced by coronary microembolization

To investigated the role of HIF-1α in myocardial inflammatory injury in rats induced by CME and its possible mechanism. Forty SD rats were separated randomly and equally into four groups, i.e. CME+HIF-1α stabilizer dimethyloxalyl glycine (CME+DMOG) group, CME+HIF-1α inhibitor YC-1 (CME+YC-1) group, CME group, and Sham group. HBFP staining, myocardial enzyme assessment, and cardiac ultrasound were used to measure microinfarct, serum c-troponin I (cTnI) level, and Cardiac function. ELISA and western blot were applied for detecting NLRP3 inflammasome pathway and TLR4/MyD88/NF-κB signaling level.Pro-inflammatory factors of IL-18, IL-1β and TNF-α increased their expression levels after CME, which indicated inflammatory responses in the myocardium. Additionally, in the inflammatory process, NLRP3 inflammasome and TLR4/MyD88/NF-κB signaling were involved. DMOG reverses these effects of CME, whereas YC-1 aggravates these effects. HIF-1α may attenuate myocardial inflammatory injury induced by CME and improve cardiac function, which can perhaps be explained by the fact that TLR4/MyD88/NF-κB signaling pathway activation is inhibited.

Changes in Index of Microcirculatory Resistance during PCI in the Left Anterior Descending Coronary Artery in Relation to Total Length of Implanted Stents

Aim

To investigate the relationship between stent length and changes in microvascular resistance during PCI in stable coronary artery disease (CAD).

Methods and Results

We measured fractional flow reserve (FFR), index of microcirculatory resistance (IMR), and coronary flow reserve (CFR) before and after stenting in 42 consecutive subjects with stable coronary artery undergoing PCI with stent in the LAD. Patients that had very long stent length (38–78 mm) had lower FFR before stenting than patients that had long (23–37 mm) and moderate (12–22 mm) stent length (0.59 (±0.16), 0.70 (±0.12), and 0.75 (±0.07); p=0.002). FFR improved after stenting and more so in subjects with very long stent length compared to long and moderate stent length (0.27 (s.d ± 16), 0.15 (s.d ± 0.12), and 0.12 (s.d ± 0.07); p for interaction = 0.013). Corrected IMR (IMR_corr) increased after stenting in subjects who had very long stent length, whereas IMR_corr was lower after stenting in subjects who had long or moderate stent length (4.6 (s.d. ± 10.7), −1.4 (s.d. ± 9,9), and −4.2 (s.d. ± 7.8); p for interaction = 0.009).

Conclusions

Changes in IMR during PCI in the LAD in stable CAD seem to be related to total length of stents implanted, possibly influencing post-PCI FFR. Larger studies are needed to confirm the relationship.

Clinical implications of periprocedural myocardial injury in patients undergoing percutaneous coronary intervention for chronic total occlusion: role of antegrade and retrograde crossing techniques

AIMS

Periprocedural myocardial injury (PMI) is frequently observed after percutaneous coronary interventions (PCI) for chronic total occlusion (CTO). We aimed to investigate the prognostic impact of PMI with the antegrade as compared to the retrograde crossing technique.

METHODS AND RESULTS

A total of 1,909 patients undergoing CTO PCI were stratified according to the presence/absence of PMI (elevation of cardiac troponin T [cTnT] >5x99th percentile of normal), and divided according to tertiles of the difference between peak and baseline cTnT within 24 hours (∆cTnT). The primary endpoint was all-cause mortality at a median follow-up of 3.1 (interquartile range 3.0-4.4) years. PMI occurred in 19.4% and 25.4% after antegrade (n=1,447) and retrograde (n=462) procedures (p<0.001). PMI was significantly associated with mortality after antegrade (adjusted HR 1.39, 95% CI: 1.02-1.88, p=0.04), but not retrograde CTO PCI (adjusted HR 0.93, 95% CI: 0.53-1.63, p=0.80, pint=0.02). With the antegrade, but not with the retrograde approach, mortality also increased with tertiles of ∆cTnT (T1: 11.0%, T2: 18.6%, T3: 21.6%, log-rank p<0.001).

CONCLUSIONS

Periprocedural myocardial injury was significantly associated with all-cause mortality following antegrade, but not retrograde CTO PCI. Hence, the higher risk of PMI following retrograde procedures did not translate into worse survival.

Protective effects and mechanism of curcumin on myocardial injury induced by coronary microembolization

OBJECTIVE

Coronary microembolization (CME) is a common complication during the percutaneous coronary intervention (PCI). CME-induced local myocardial inflammation and myocardial apoptosis are the primary causes of progressive cardiac dysfunction. Curcumin exerts a protective role in various cardiovascular diseases; however, its effects in CME are yet to be clarified. Therefore, the current study investigated the effects of curcumin on myocardial inflammatory responses, myocardial apoptosis, and cardiac dysfunctions induced by CME in rats.

METHODS

A total of 40 Sprague-Dawley rats were randomly divided into the following groups: Sham operation (sham group), CME group, curcumin, and control with 10 rats in each group. The ascending aortas were clamped, and the CME-model group was established by injecting microspheres into the apex of the left ventricle. An equivalent amount of normal saline was injected to establish the sham group. The cardiac functions, serum c-troponin I level, and apoptotic index was examined. Also, the levels of Toll-like receptor 4 (TLR4), myeloid differentiation primary response 88 (MYD88), nuclear factor κB (NF-κB) p65, BCL2-associated X protein (Bax), B-cell lymphoma 2 (Bcl-2), cleaved caspase-3, tumor necrosis factor α (TNF-α), and interleukin-1β (IL-1β) were detected.

RESULTS

Myocardial dysfunction enhanced serum c-troponin I, and apoptotic index were induced following CME. Moreover, CME elevated the expression of TLR4, MyD88, NF-κB p65, cleaved caspase-3, TNF-α, and IL-1β, while the Bcl-2/Bax ratio decreased. Curcumin reversed these effects by CME, while the gastric lavage control did not exert any effect.

CONCLUSION

Curcumin was responsible for the anti-CME-induced myocardial injury. The effector mechanism might be related to the reduction of cardiomyocyte apoptosis and inhibition of myocardial inflammatory responses mediated by TLR4/MyD88/NF-κB signaling pathway.

Role of TLR4/MyD88/NF-κB signaling pathway in coronary microembolization-induced myocardial injury prevented and treated with nicorandil

Coronary microembolization (CME) is a common complication during the treatment of acute coronary syndrome (ACS) and percutaneous coronary intervention (PCI). Nicorandil can be used to prevent myocardial injury after PCI to reduce the incidence of coronary no-reflow and slow flow, and play a role in myocardial protection, suggesting that its mechanism may be related to the inhibition of CME-induced inflammation of cardiomyocytes. However, the specific mechanism remains unclear. This study investigated the myocardial protective effects of nicorandil pretreatment on CME-induced myocardial injury and the specific mechanism of its inhibition of myocardial inflammation. An CME rat model exhibited CME-induced myocardial inflammation and the elevation of serum tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-1β based on echocardiography, myocardial enzyme detection, hematoxylin and eosin (HE) and hematoxylin-basic fuchsin-picric acid (HBFP) stainings, ELISA, quantitative real-time PCR, and western blotting. Nicorandil treatment seven days before CME induction effectively inhibited myocardial inflammation, ameliorated myocardial injury, and improved cardiac function, mainly by inhibiting Toll-like receptor 4 (TLR4)-mediated myeloid differentiation primary response protein 88 (MyD88)-dependent nuclear factor-kappa B (NF-κB) signaling. Rat neonatal cardiomyocyte experiments further confirmed that nicorandil ameliorated lipopolysaccharide (LPS)-induced myocardial inflammation and improved cardiomyocyte survival. The specific mechanisms mainly involved the inhibition of TLR4/MyD88/NF-κB signaling and the reduction of the inflammatory cytokines TNF-α and IL-1β released from cardiomyocytes. In summary, nicorandil significantly protected cardiomyocytes from CME-induced myocardial injury mainly by inhibiting TLR4/MyD88/NF-κB signaling, thereby reducing the onset of CME-induced myocardial inflammation. This could be one of the important mechanisms for reducing postoperative myocardial injury via PCI-preoperative prophylactic treatment with nicorandil.

Role of high mobility group A1/nuclear factor-kappa B signaling in coronary microembolization-induced myocardial injury

OBJECTIVE

Coronary microembolization (CME) is a common complication in percutaneous coronary intervention (PCI). Local myocardial inflammation caused by CME is the major cause of progressive cardiac dysfunction. High mobility group A1 (HMGA1)/nuclear factor-kappa B (NF-κB) signaling plays an important role in the development and progression of inflammation, but its role in CME remains unclear. This study evaluated the effect of HMGA1/NF-κB signaling on CME-induced myocardial inflammation and cardiac dysfunction.

METHODS

Forty Sprague-Dawley rats were randomly divided into four groups: sham, CME, CME + HMGA1 small interfering RNA (HMGA1 siRNA), and CME + scrambled siRNA (control siRNA) groups, with 10 animals each. The CME model group was established by clamping the ascending aorta and injecting microspheres through the left ventricular apex for embolization, and the sham group was established by injecting the same amount of normal saline. The HMGA1 siRNA group was injected with HMGA1 siRNA transfection complexes into the tail vein 72 h before CME modeling, and the control siRNA group was caudally injected with the same amount of scrambled siRNA 72 h before CME modeling. Twelve hours after the operation, cardiac function, serum c-troponin I level, and microinfarct size were examined. The levels of HMGA1, NF-κB p65, TNF-α, and IL-1β were detected.

RESULTS

Myocardial dysfunction, enhanced serum c-troponin I, and microinfarct were induced following CME. Moreover, CME induced an increased expression of HMGA1, NF-κB p65, TNF-α, and IL-1β. The HMGA1 siRNA reversed these effects by CME, while the scrambled siRNA had no effect.

CONCLUSIONS

HMGA1/NF-κB signaling is involved in CME-induced myocardial inflammation. Inhibition of HMGA1/NF-κB signaling attenuated the CME-induced myocardial injury and improved cardiac function, suggesting a new potential target for the prevention and treatment of CME-induced myocardial injury.

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.

Development of a real-time and quantitative thrombus sensor for an extracorporeal centrifugal blood pump by near-infrared light

We developed an optical thrombus sensor for a monopivot extracorporeal centrifugal blood pump. In this study, we investigated its quantitative performance for thrombus detection in acute animal experiments of left ventricular assist using the pump on pathogen-free pigs. Optical fibers were set in the driver unit of the pump. The incident light at the near-infrared wavelength of 810 nm was aimed at the pivot bearing, and the resulting scattered light was guided to the optical fibers. The detected signal was analyzed to obtain the thrombus formation level. As a result, real-time and quantitative monitoring of the thrombus surface area on the pivot bearing was achieved with an accuracy of 3.6 ± 2.3 mm². In addition, the sensing method using the near-infrared light was not influenced by changes in the oxygen saturation and the hematocrit. It is expected that the developed sensor will be useful for optimal anticoagulation management for long-term extracorporeal circulation therapies.

Intraluminal Intensity of Blood Speckle on Intravascular Ultrasound, a Novel Predictor of Periprocedural Myocardial Injury After Coronary Stenting

The difference in the intraluminal intensity of blood speckle (IBS) on integrated backscatter-intravascular ultrasound (IB-IVUS) across a coronary artery stenosis (i.e., ΔIBS) has previously shown a negative correlation with fractional flow reserve, reflecting an impaired coronary blood flow. Periprocedural myocardial injury (PMI) after coronary stenting has also been associated with coronary circulatory dysfunction. The aim of this study was to investigate the relation between ΔIBS after coronary stenting and PMI. A total of 180 patients who underwent elective coronary stenting under IVUS guidance for a single lesion were included. Intraluminal IBS was measured using IB-IVUS in cross sections at the ostium of the target vessel and at the distal reference of the stent. ΔIBS was calculated as (distal IBS value) - (ostium IBS value). PMI was defined as an elevation of troponin I >5 times the 99th percentile upper reference limit (>0.45 ng/ml) within 24 hours after the procedure. The mean ΔIBS after coronary stenting was 6.52 ± 5.71. There was a significantly greater use of the rotational atherectomy, the number of stents, the total stent length, and ΔIBS in patients with PMI than those without. In the receiver operating characteristic curve analysis, ΔIBS significantly predicted PMI (area under the curve 0.64, best cut-off value 7.88, p = 0.001). Multiple logistic regression analysis determined that the total stent length, the use of rotational atherectomy, and ΔIBS were independent predictors of PMI. In conclusion, greater ΔIBS assessed by IB-IVUS was significantly associated with PMI after coronary stenting in patients with a stable coronary artery disease.

Remote ischemic postconditioning during percutaneous coronary interventions: remote ischemic postconditioning-percutaneous coronary intervention randomized trial

BACKGROUND

Remote ischemic preconditioning may result in reduction in infarct size during percutaneous coronary intervention (PCI). It is unclear whether remote ischemic postconditioning (RIPost) will reduce the incidence of myocardial injury after PCI, and whether ischemic conditioning of a larger remote organ (thigh versus arm) would provide further myocardial protection.

METHODS AND RESULTS

We randomized 360 patients presenting with stable or unstable angina (28% of patients) and negative Troponin T at baseline to 3 groups: 2 groups received RIPost (induced by ischemia to upper or lower limb), and a third was the control group. RIPost was applied during PCI immediately after stent deployment, by three 5-minute cycles of blood pressure cuff inflation to >200 mm Hg in the arm or thigh (20 mm Hg in the control) with 5-minute breaks between each cycle. The primary end-point was the proportion of patients with Troponin T levels >3×ULN postprocedure (at 6 or 18-24 hours), where ULN stands for upper limit of normal. A total of 120 patients were randomized to each group. There were no differences in baseline characteristics between the 3 groups. The primary outcome occurred in 30%, 35%, and 35% of the arm, thigh, and control groups, respectively (P=0.64). There were no differences in creatine kinase or high sensitivity C-reactive protein levels after PCI or in the incidence of acute kidney injury between the groups.

CONCLUSIONS

RIPost during PCI did not reduce the incidence of periprocedural myocardial injury. Similar effect was obtained when remote ischemia was induced to the upper or lower limb.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT00970827.

Imaging the myocardial microcirculation post-myocardial infarction

The myocardial microcirculation provides the vital pressure control and metabolic homeostasis for normal muscle function. Microvascular dysfunction is implicated in chronic cardiac disease and can signify higher risk, but its effect in acute myocardial infarction (AMI) can be profound. Modern management of AMI is focussed entirely on timely epicardial coronary patency, but as a result can leave microcirculatory devastation in its wake. The 'no-reflow' phenomenon occurs in up to 40 % of those successfully reperfused following an ST-elevation AMI (STEMI), and reflects significant microvessel injury that at its most severe involves both microvascular obstruction (MVO) and intramyocardial haemorrhage. Myocardial contrast echocardiography and cardiac magnetic resonance imaging have both led the field in establishing MVO as the prime determinant of adverse left ventricular (LV) remodeling, LV dysfunction, heart failure and increased mortality. These imaging techniques will be essential to support future research endeavours and shift focus to the maintenance of microvascular flow in AMI.

Remote ischemic conditioning: the cardiologist's perspective

Early and successful restoration of myocardial reperfusion following an ischemic event is the most effective strategy to reduce final infarct size and improve clinical outcome. However, revascularization per se may induce further myocardial damage by myocardial ischemia-reperfusion injury and worsen clinical outcome. Therefore, new therapeutic strategies are required to protect the myocardium against ischemia-reperfusion injury in patients with coronary artery disease. Remote ischemic conditioning (RIC) by brief nonlethal episodes of ischemia and reperfusion to an organ or tissue remote from the heart activates innate cardioprotective mechanisms. The discovery that RIC can be performed noninvasively using a blood pressure cuff on the upper arm to induce brief episodes of limb ischemia and reperfusion has facilitated the translation of RIC into the clinical arena. Whereas some trials have shown contradictory results, recently published proof-of-concept clinical studies have reported encouraging results with RIC. Large-scale multicenter clinical trials are needed to establish the role of RIC in the current clinical practice. At present, the use of RIC in acute coronary syndromes seems particularly attractive due to its potential in-ambulance application and apparent dramatic reduction in infarct size in the patients with the largest infarcts. Cardiac arrest and stroke represent ischemia-reperfusion disorders where RIC has further potential to improve outcome beyond rapid revascularization alone.

PERIPROCEDURAL MYOCARDIAL DAMAGE

Percutaneous coronary intervention (PCI), as a method of myocardial revascularisation, is widely and effectively used for the treatment of coronary heart disease (CHD), with immediate success rates of >90%. Depending on the diagnostic criteria, 5–30% of these patients could develop the signs of periprocedural myocardial damage (PMD) or periprocedural myocardial infarction (PMI). PMD predictors, mechanisms of PMD development, and its specific clinical features play an important role in the PMI prevention. At present, there is no universal agreement on the definition and diagnostics of periprocedural myocardial necrosis and PMI, or on their impact on the clinical outcomes. According to the results of the recent studies, which are presented in this review, the current criteria of PMI might need to be modified, due to the increasingly high sensitivity of the modern threshold levels of troponin. 

Risk analysis and detection of thrombosis by measurement of electrical resistivity of blood

Monitoring of thrombogenic process is very important in ventricular assistance devices (VADs) used as temporary or permanent measures in patients with advanced heart failure. Currently, there is a lack of a system which can perform a real-time monitoring of thrombogenic activity. Electrical signals vary according to the change in concentration of coagulation factors as well as the distribution of blood cells, and thus have potential to detect the thrombogenic process in an early stage. In the present work, we have made an assessment of an instrumentation system exploiting the electrical properties of blood. The experiments were conducted using bovine blood. Electrical resistance tomography with eight-electrode sensor was used to monitor the spatio-temporal change in electrical resistivity of blood in thrombogenic and non-thrombogenic condition. Under non-thrombogenic condition, the resistivity was uniform across the cross-section and average resistivity monotonically decreased with time before remaining almost flat. In contrary, under thrombogenic condition, there was non-uniform distribution across the cross-section, and average resistivity fluctuated with time.

Saphenous vein aorto-coronary graft atherosclerosis in patients with chronic kidney disease: more plaque calcification and necrosis, but less vasoconstrictor potential

Atherosclerotic coronary arteries are more calcified in patients with than without chronic kidney disease (CKD). We addressed the potential for coronary microvascular obstruction in patients with and without CKD during stenting for saphenous vein aorto-coronary graft (SVG) stenosis under protection with a distal occlusion/aspiration device. In patients with and without CKD (n = 20/20), SVG plaque composition was analyzed from virtual histology using intravascular ultrasound analysis before stent implantation. There was more dense calcium and more necrotic core in patients with than without CKD (14 ± 3 vs. 3 ± 1 % and 21 ± 3 vs. 12 ± 2 % of plaque volume, respectively). Coronary aspirate was retrieved during stent implantation and divided into particulate debris and plasma. Patients with CKD had more particulate debris and calcium release than patients without CKD. In contrast, the release of serotonin was less in patients with than without CKD (0.4 ± 0.1 vs. 1.2 ± 0.3 μmol/L), whereas that of catecholamines, endothelin, tissue factor, thromboxane, tumor necrosis factor α, and C reactive protein was not significantly different. Confirming the biochemical results, aspirate plasma from patients with CKD induced less vasoconstriction of rat mesenteric arteries than that from patients without CKD (with endothelium (+E), 26 ± 7 %; without endothelium (-E): 28 ± 7 % vs. +E, 68 ± 12 %; -E: 95 ± 16 % of maximum KCl-induced vasoconstriction). Graft atherosclerosis of patients with CKD is more degenerated and releases more particulate debris and calcium, but the aspirate has surprisingly less serotonin and vasoconstrictor potential.

Coronary microvascular dysfunction in the clinical setting: from mystery to reality

Far more extensive than the epicardial coronary vasculature that can be visualized angiographically is the coronary microcirculation, which foregoes routine imaging. Probably due to the lack of techniques able to provide tangible evidence of its crucial role, the clinical importance of coronary microvascular dysfunction is not fully appreciated. However, evidence gathered over the last several decades indicates that both functional and structural abnormalities of the coronary microvasculature can lead to myocardial ischaemia, often comparable with that caused by obstructive coronary artery disease. Indeed, a marked increase in coronary microvascular resistance can impair coronary blood flow and trigger angina pectoris, ischaemic ECG shifts, and myocardial perfusion defects, and lead to left ventricular dysfunction in patients who otherwise have patent epicardial coronary arteries. This condition--often referred to as 'chest pain with normal coronary arteries' or 'cardiac syndrome X'--encompasses several pathogenic mechanisms involving the coronary microcirculation. Of importance, coronary microvascular dysfunction can occur in conjunction with several other cardiac disease processes. In this article, we review the pathogenic mechanisms leading to coronary microvascular dysfunction and its diagnostic assessment, as well as the different clinical presentations and prognostic implications of microvascular angina. As such, this review aims to remove at least some of the mystery surrounding the notion of coronary microvascular dysfunction and to show why it represents a true clinical entity.

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.

Effect of embolic particles during coronary interventional procedures on regional wall motion in patients with stable angina pectoris

Microembolization during percutaneous coronary intervention (PCI) causes minor myocardial injury, and a Doppler guidewire can detect embolic particles as high-intensity transient signals (HITS). The present study investigated the effect of microembolization during PCI on regional wall motion using a Doppler guidewire and myocardial strain analysis. We performed PCI to the left anterior descending coronary artery in 25 patients (18 men and 7 women, 68 ± 8 years old) with stable angina pectoris. Coronary flow spectrums were obtained with a Doppler guidewire to count the total number of HITS throughout the PCI procedures. On the days before and after PCI, we recorded echocardiography and measured the longitudinal peak systolic strain, peak strain rate, and early diastolic strain rate in the left anterior descending territory using a 2-dimensional speckle tracking method. PCI was successfully performed, and 10 ± 6 HITS (range 0 to 22, median 9) were recognized during PCI. The echocardiographic study showed no visible wall motion abnormalities in the left anterior descending territory either after or before PCI. In cases in which the total number of HITS was ≥10, the peak systolic strain, peak strain rate, and early diastolic strain rate worsened on the day after PCI compared with those on the day before PCI (p <0.01). The rates of change in peak systolic strain and early diastolic strain rate, defined as the ratios of those parameters after PCI to those before PCI, had modest to strong inverse correlations with the total number of HITS (R(2) = 0.35 and R(2) = 0.46, respectively). In conclusion, periprocedural microembolization during PCI reduces subclinical cardiac function in patients with stable angina pectoris.

Changes in left ventricular ejection fraction and coronary flow reserve after coronary microembolization

INTRODUCTION

Although coronary microembolization (CME) is a frequent phenomenon in patients undergoing percutaneous coronary intervention, few data are available on the changes in left ventricular ejection fraction (LVEF) and coronary flow reserve (CFR) after CME.

MATERIAL AND METHODS

In this study, six miniature swine of either sex (body weight 21-25 kg) were used to prepare a CME model. After coronary angiography, 1.2 × 10(5) microspheres (42 µm) were selectively infused into the left anterior descending artery via an infusion catheter. Left ventricular ejection fraction was evaluated using transthoracic echocardiography; myocardial blood flow was measured using coloured microspheres; and CFR and coronary pressure were measured using Doppler and a pressure wire.

RESULTS

Left ventricular ejection fraction was 0.77 ±0.08 at baseline, 0.69 ±0.08 at 2 h, 0.68 ±0.08 at 6 h, and 0.76 ±0.06 at 1 week (2 h vs. baseline p < 0.05; 6 h vs. baseline p < 0.01). After CME, left ventricular end systolic volume (LVESV) and end diastolic volume (LVEDV) were significant larger 1 week later (p < 0.01 for both), while CFR was significantly reduced at 6 h (1.24 ±0.10 at 6 h vs. 1.77 ±0.30 at baseline, p < 0.01) and myocardial blood flow remained unchanged. Serum ET-1 level was significantly higher only at 6 h after CME (6 h vs. baseline p < 0.05).

CONCLUSIONS

Reduction of CFR and LVEF is significant at 6 h after CME and recovers 1 week later with left ventricular dilation.

Deep echo attenuation without calcification increases the risk of periprocedural myonecrosis after elective percutaneous coronary intervention in patients with coronary artery disease

OBJECTIVE

To investigate the clinical factors, including intravascular ultrasound (IVUS) findings, associated with percutaneous coronary intervention (PCI)-related periprocedural myonecrosis (PM) in patients with stable coronary artery disease (CAD).

METHODS

The study included 46 patients (mean age 65±2 y, 37 men) with stable CAD who underwent elective PCI using IVUS and a Doppler flow guidewire. In addition to routine IVUS measurements, the presence of deep echo attenuation (DEA) without calcification was assessed. The sum of all high-intensity transient signals (HITS) after a balloon deflation procedure was calculated using a Doppler flow guidewire. PM was defined as an elevation in troponin T to >0.03 ng/mL 24-hour after PCI. Patients were divided into 2 groups on the basis of the presence or absence of PM.

RESULTS

PM was identified in 17 patients (37%). Estimated glomerular filtration ratio was lower in the PM group (p=0.021). Target vessel distribution was different between the groups (p=0.004). Positive remodeling and DEA, as observed on IVUS, were more common in the PM group (p=0.03 and p<0.0001, respectively). The total number of HITS was higher in the PM group (p=0.003). Logistic regression analysis demonstrated that the presence of DEA (p=0.003) was the sole factor associated with the occurrence of PM.

CONCLUSION

These results demonstrated that DEA is an important factor associated with PM in patients who underwent an elective PCI. Therefore, IVUS to determine the presence of DEA should be performed before PCI.

Role of inflammation in the regulation of coronary blood flow in ischemia and reperfusion: mechanisms and therapeutic implications

A multitude of factors, including increased coronary vascular resistance and dysregulated coronary microcirculatory function, contribute to the impairment of coronary blood flow (CBF) regulation and the pathogenesis of myocardial ischemia/reperfusion (I/R) injury. CBF is primarily determined by coronary vascular resistance, which is affected by the balance between various vasodilators and vasoconstrictors. Myocardial I/R causes reduced production of endogenous vasodilators, such as nitric oxide (NO), leaving unopposed vasoconstriction that is caused mainly by continued presence of endothelin-1 (ET-1) and serotonin (5-HT); this imbalance in turn enhances vascular tone, triggers inflammatory response, decreases CBF and exacerbates reperfusion injury. Various inflammatory cytokines participate in the regulation of coronary vasomotor function by affecting the balance between vasodilators and vasoconstrictors. In addition to the enhanced coronary vasoconstriction, coronary microembolization, inflammatory cell infiltration and post-ischemic hyperpermeability contribute to the impairment of coronary microcirculatory function and myocardial perfusion during I/R. Ongoing research examining the role of inflammation in the regulation of CBF and coronary microcirculatory function in myocardial I/R is expected to yield new insights that will lead to therapies for ameliorating the vascular inflammatory response in coronary artery diseases (CADs) in the clinical setting. This article is part of a Special Issue entitled "Coronary Blood Flow".

In vivo flow cytometry of circulating clots using negative photothermal and photoacoustic contrasts

Conventional photothermal (PT) and photoacousic (PA) imaging, spectroscopy, and cytometry are preferentially based on positive PT/PA effects, when signals are above background. Here, we introduce PT/PA technique based on detection of negative signals below background. Among various new applications, we propose label-free in vivo flow cytometry of circulating clots. No method has been developed for the early detection of clots of different compositions as a source of thromboembolism including ischemia at strokes and myocardial infarction. When a low-absorbing, platelet-rich clot passes a laser-irradiated vessel volume, a transient decrease in local absorption results in an ultrasharp negative PA hole in blood background. Using this phenomenon alone or in combination with positive contrasts, we demonstrated identification of white, red, and mixed clots on a mouse model of myocardial infarction and human blood. The concentration and size of clots were measured with threshold down to few clots in the entire circulation with size as low as 20 μm. This multiparameter diagnostic platform using portable personal high-speed flow cytometer with negative dynamic contrast mode has potential to real-time defining risk factors for cardiovascular diseases, and for prognosis and prevention of stroke or use clot count as a marker of therapy efficacy. Possibility for label-free detection of platelets, leukocytes, tumor cells or targeting themby negative PA probes (e.g., nonabsorbing beads or bubbles) is also highlighted.

Micro soft tissues visualization based on x-ray phase-contrast imaging

The current imaging methods have a limited ability to visualize microstructures of biological soft tissues. Small lesions cannot be detected at the early stage of the disease. Phase contrast imaging (PCI) is a novel non-invasive imaging technique that can provide high contrast images of soft tissues by the use of X-ray phase shift. It is a new choice in terms of non-invasively revealing soft tissue details. In this study, the lung and hepatic fibrosis models of mice and rats were used to investigate the ability of PCI in microstructures observation of soft tissues. Our results demonstrated that different liver fibrosis stages could be distinguished non-invasively by PCI. The three-dimensional morphology of a segment of blood vessel was constructed. Noteworthy, the blood clot inside the vessel was visualized in three dimensions which provided a precise description of vessel stenosis. Furthermore, the whole lung airways including the alveoli were obtained. We had specifically highlighted its use in the visualization and assessment of the alveoli. To our knowledge, this was the first time for non-invasive alveoli imaging using PCI. This finding may offer a new perspective on the diagnosis of respiratory disease. All the results confirmed that PCI will be a valuable tool in biological soft tissues imaging.

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."