Combined revascularization strategy for acute myocardial infarction in patients with intracoronary thrombus: preceding intracoronary thrombolysis and subsequent mechanical angioplasty

Adjunctive Intracoronary Fibrinolytic Therapy During Primary Percutaneous Coronary Intervention

Despite routinely restoring epicardial coronary patency, with primary percutaneous coronary intervention (PCI), microvascular obstruction affects approximately half of patients and confers an adverse prognosis. There are no evidence-based treatments for microvascular obstruction. A key contributor to microvascular obstruction is distal embolisation and microvascular thrombi. Adjunctive intracoronary fibrinolytic therapy may reduce thrombotic burden, potentially reducing distal embolisation of atherothrombotic debris to the microcirculation. In this review, the evidence from published randomised trials on the effects of adjunctive intracoronary fibrinolytic therapy during primary PCI is critically appraised, the ongoing randomised trials are described, and conclusions are made from the available evidence. Clinical uncertainties, to be addressed by future research, are highlighted.

Role of Intracoronary Fibrinolytic Therapy in Contemporary PCI Practice

Plaque rupture or plaque erosion leads to intracoronary thrombus formation resulting in coronary artery occlusion and ST-segment elevation myocardial infarction. Early restoration of blood flow in occluded coronary artery is the mainstay of therapy and it can be achieved by either thrombolytic therapy or primary percutaneous coronary intervention (P-PCI) or a combination of these two in many different ways. It has been proved that primary PCI is better than thrombolytic therapy in establishing early and effective recanalization of infarct related artery, reducing major adverse cardiovascular events (MACE) and increasing survival. There have been tremendous advances in PCI techniques over the years with newer stents, thrombectomy devices, and adjunctive pharmacotherapy. However, intracoronary thrombus continues to be the bane of interventional cardiologists. Failure of recanalization, suboptimal results, distal embolization, no reflow and impaired myocardial perfusion are some of the unresolved difficulties, regularly seen during PCI of patients with large intracoronary thrombus burden indicating an unmet need. This review focuses on emerging evidence about the usefulness of intracoronary thrombolytic therapy as an adjunct to PCI in patients with large intracoronary thrombus burden.

Intracoronary tenecteplase in STEMI with massive thrombus

Primary percutaneous coronary intervention is the current standard of care in ST elevation myocardial infarction (STEMI). However, large thrombus is an independent predictor for stent thrombosis and major adverse cardiac events in patients undergoing primary angioplasty for STEMI. Here we report a series of STEMI patients with large thrombus burden treated successfully with low dose intracoronary thrombolysis. There was prompt and early ST resolution. There was improvement in thrombolysis in myocardial infarction (TIMI) flow and myocardial blush grade postlysis in all patients. Majority had recanalised infarct related coronary artery thus obviating the need for stenting. There was no inhospital or 1 month mortality or bleeding events. Hence intracoronary thrombolysis is an option in patients with large thrombus burden.

The pathogenesis and treatment of no-reflow occurring during percutaneous coronary intervention

No-reflow is one of the major causes of postinterventional rise of cardiac enzyme and myocardial infarction (MI). This complication is associated with substantial morbidity and mortality after percutaneous coronary intervention (PCI). During and after a no-reflow episode, the patient can suffer from severe chest pain, hypotension, bradycardia, hemodynamic collapse, MI, congestive heart failure, and death. Every effort should be taken to reduce the incidence of this complication. The distal embolic protection device has been shown to decrease this risk in saphenous vein graft (SVG) interventions but not in native coronaries. On the other hand, the use of glycoprotein IIb/IIIa receptor antagonists have been effective in reducing the occurrence of no-reflow during PCI of native coronaries but not during SVG interventions. The treatment of no-reflow is based on the intracoronary administrations of medications that induce maximal vasodilatation in small distal coronary vasculature. The most commonly used drugs in this setting are adenosine, nitroprusside, and verapamil. The goal of this study was to review the pathogenesis and treatment of no-reflow in patients undergoing PCI.

Serum B-type natriuretic peptide on admission can predict the 'no-reflow' phenomenon after primary drug-eluting stent implantation for ST-segment elevation myocardial infarction

BACKGROUND

The angiographic 'no-reflow' phenomenon after primary percutaneous coronary intervention (PPCI) is associated with a poor short-term and long-term clinical prognosis of ST-elevation myocardial infarction (STEMI). Although the increasing use of primary drug-eluting stent (DES) deployment for STEMI resulted in reduced adverse clinical outcomes, the prevalence of no-reflow has been unchanged. The purpose of our study was to evaluate the predictors for no-reflow for STEMI and identify such high-risk patients in the DES era.

METHODS

The study prospectively enrolled 300 consecutive STEMI patients (80% men; 57+/-11 years) who underwent PPCI within 12 h of symptom onset. The no-reflow phenomenon was defined as an angiographic outcome of Thrombolysis In Myocardial Infarction (TIMI) grade <3 without accompanying mechanical factors.

RESULTS

Compared to normal reflow patients, no-reflow patients (n=15, 5% of the total study population) were older (64+/-13 vs. 57+/-11 years; P=0.019), transferred to hospital later (7.1+/-3.2 vs. 4.5+/-3.8 h; P=0.011), and had a higher TIMI risk score (5.5+/-2.0 vs. 3.8+/-2.2; P=0.004). B-type natriuretic peptide (BNP), high sensitivity C-reactive protein, and serum creatinine levels were higher in the no-reflow than the normal reflow group. Multivariate analysis (including clinical, angiographic and procedural variables with a P<0.2 in univariate analysis) showed that high BNP level on admission was the only independent predictor of no-reflow. The area under the receiver-operating characteristics curve analysis value for BNP was 0.786. BNP > or =90 pg/ml showed a sensitivity of 80% and a specificity of 70% for predicting no-reflow after primary DES implantation (OR 14.953, 95% CI 3.131-71.419, P=0.001).

CONCLUSIONS

Angiographic 'no-reflow' phenomenon after primary DES implantation for STEMI can be predicted by BNP levels on admission. BNP-guided approach may be useful in identifying patients at high risk of the no-reflow phenomenon after primary stenting.

Role of Sam68 as an adaptor protein in signal transduction

Sam68, the substrate of Src in mitosis, belongs to the family of RNA binding proteins. Sam68 contains consensus sequences to interact with other proteins via specific domains. Thus, Sam68 has various proline-rich sequences to interact with SH3 domain-containing proteins. Moreover, Sam68 also has a C-terminal domain rich in tyrosine residues that is a substrate for tyrosine kinases. Tyrosine phosphorylation of Sam68 promotes its interaction with SH2 containing proteins. The association of Sam68 with SH3 domain-containing proteins, and its tyrosine phosphorylation may negatively regulate its RNA binding activity. The presence of these consensus sequences to interact with different domains allows this protein to participate in signal transduction pathways triggered by tyrosine kinases. Thus, Sam68 participates in the signaling of T cell receptors, leptin and insulin receptors. In these systems Sam68 is tyrosine phosphorylated and recruited to specific signaling complexes. The participation of Sam68 in signaling suggests that it may function as an adaptor molecule, working as a dock to recruit other signaling molecules. Finally, the connection between this role of Sam68 in protein-protein interaction with RNA binding activity may connect signal transduction of tyrosine kinases with the regulation of RNA metabolism.

Incidence and Management of "No-Reflow" Following Percutaneous Coronary Interventions

No-reflow is a complex condition associated with inadequate myocardial perfusion of the coronary artery in the absence of epicardial obstruction. It can occur in several settings, including percutaneous coronary intervention, especially in complex thrombotic lesions of native arteries and vein grafts and in primary angioplasty. The causes of no-reflow are not completely understood, and current treatments consist of intracoronary vasodilators, antithrombotic therapies, and mechanical devices (including aspiration thrombectomy catheters and embolic protection devices).

Distal Shower Embolization During Directional Coronary Atherectomy and Stenting for Diffuse Stenosis of Right Coronary Artery-Current Limitations of Intravascular Ultrasonography for Evaluating Fragile Plaque-

A 74 year-old male with old anterior and inferior myocardial infarctions was treated with staged percutaneous coronary intervention. A chronic total occlusion of the middle segment of the left anterior descending branch was successfully stented during the first stage, and during the second stage, preprocedural intravascular ultrasonography (IVUS) revealed that the proximal segment of the right coronary artery was diffusely stenosed by mixed plaque. Directional coronary atherectomy under IVUS guidance was performed, but coronary slow flow appeared during the procedure. After successfully bailing out with intracoronary nicorandil, percutaneous thrombectomy and manual blood pumping, 2 coronary stents were implanted to fully cover the lesion. Quite contrary to expectation, the no-reflow phenomenon appeared just after post-dilatation and a repeat of the same maneuver could not completely recover coronary flow. Plaque fragility could not be predicted from the IVUS examination.

Rescue percutaneous thrombectomy system provides better angiographic coronary flow and does not increase the in-hospital cost in patients with acute myocardial infarction

In acute myocardial infarction (AMI), slow flow (<TIMI 3) after reperfusion remains a problem. Removing the thrombus from culprit lesions should reduce this phenomenon and improve clinical outcome, so to evaluate the advantages of the Rescue percutaneous thrombectomy system (Rescue PT), 65 cases of AMI in which Rescue PT (RT group) was carried out were compared with 66 cases of AMI that were treated before Rescue PT became available (non-RT group). The study compared angiographic results, in-hospital clinical outcomes and the cost estimation during hospitalization. In the RT group, direct stenting was chosen more frequently (57% vs 5%, p=0.002) and the number of balloon catheters used was less (0.7+/-0.8 vs 1.4+/-0.6, p<0.0001). The incidence of slow flow and the maximum serum creatine kinase value over 24 h were lower in the RT group (3.1% vs 19.7%, p=0.01 and 3444+/-2218 IU vs 4182+/-3010 IU, p<0.05 respectively); however, in-hospital clinical outcomes were identical. No major complication related to the Rescue PT procedure was found. The cost for the initial procedure and the total cost during hospitalization were similar between the groups. Thrombectomy with Rescue PT before mechanical dilatation of the culprit lesions is safe and feasible, even in the emergency clinical setting, and results in better angiographic coronary flow. This therapy facilitates direct stenting and does not increase the cost of treatment.

Thrombolytic potency of acid-stabilized plasmin: superiority over tissue-type plasminogen activator in an in vitro model of catheter-assisted thrombolysis

Plasmin, the direct fibrinolytic enzyme, was compared with tissue plasminogen activator (t-PA) in an in vitro thrombolysis model. Plasmin has been prepared in a highly pure form from human plasma and has been stabilized against auto-degradation by low-pH formulation. This acidified formulation of plasmin has been designed to have a low buffering capacity so that it can be directly infused into clots in a stable and latently active form. This low-pH formulation has been shown to be equivalent to a neutral-pH formulation of plasmin in its extent of clot lysis. An in vitro model of catheter-assisted thrombolysis has been devised in which large (12 x 0.6 cm), retracted clots are treated with an intrathrombus thrombolytic agent via a multi-sideport catheter. Plasmin dissolves these plasminogen-deficient clots in a dose-dependent manner and is clearly superior to t-PA. In this model system, t-PA exhibits efficacy only when retracted clots are replenished with plasminogen.

Low-dose tissue plasminogen activator followed by planned rescue angioplasty reduces time to reperfusion for acute myocardial infarction treated at community hospitals

The time from admission to reperfusion in patients with acute myocardial infarction (AMI) was compared according to the type of hospital and treatment strategy. A total of 164 patients with a first AMI within 12h of onset were enrolled at one tertiary emergency center (TEC) and 6 community hospitals (CHs). The subjects were randomly assigned to receive either primary percutaneous transluminal coronary angioplasty (PTCA) (TEC-primary PTCA and CHs-primary PTCA groups) or 800,000 units of intravenous monteplase, half the standard dose of a mutant tissue plasminogen activator (t-PA), followed by rescue PTCA if the Thrombolysis in Myocardial Infarction (TIMI) flow grade was 2 or less (TEC-monteplase and CHs-monteplase groups) on the first coronary angiogram. Sixty minutes after admission, TIMI flow grade 3 rates of the study groups were as follows, in descending order: TEC-monteplase group, CHs-monteplase group, TEC-primary PTCA group, and CHs-primary PTCA group (56%, 41%, 36%, and 8%, respectively; p<0.01). However, there was no significant difference in the final TIMI flow grade 3 rate among the 4 groups. In the CHs, the peak creatine kinase tended to be lower in the monteplase group than in the primary PTCA group. The results suggest that low-dose monteplase followed by rescue PTCA is an effective strategy for promoting early reperfusion in patients with AMI, especially those who are treated at CHs.

Signal averaged electrocardiography of Japanese

Although studies show that the ventricular tachycardia and sudden cardiac deaths caused by ischemic heart diseases affect Japanese less than Westerners, predictive accuracy of the signal averaged ECG for ventricular tachycardia and sudden cardiac deaths are almost the same as the results for Westerners. The recent prognosis of ischemic heart diseases is showing improvements along with the development of re-perfusion therapy, which is changing the significance of the signal averaged ECG. Therefore a clinical use for signal averaged ECG should be discussed in cases of cardiomyopathy which cause sudden cardiac deaths and other heart diseases. So it is necessary to redetermine normal values of the signal averaged ECG parameters. In this article, the following was reviewed on the basis of our studies regarding the clinical significance of the signal averaged ECG of Japanese and normal signal averaged ECG values. (1) System and gender specific differences on signal averaged ECG of Japanese, (2) His-Purkinje system, pre-P deflection and atrial late potential on signal averaged ECG, (3) Ventricular late potentials of Japanese.