Outcome Comparison of 600- and 300-mg Loading Doses of Clopidogrel in Patients Undergoing Primary Percutaneous Coronary Intervention for ST-Segment Elevation Myocardial Infarction

Initial Despair and Current Hope of Identifying a Clinically Useful Treatment of Myocardial Reperfusion Injury: Insights Derived from Studies of Platelet P2Y12 Antagonists and Interference with Inflammation and NLRP3 Assembly

Myocardial necrosis following the successful reperfusion of a coronary artery occluded by thrombus in a patient presenting with ST-elevation myocardial infarction (STEMI) continues to be a serious problem, despite the multiple attempts to attenuate the necrosis with agents that have shown promise in pre-clinical investigations. Possible reasons include confounding clinical risk factors, the delayed application of protective agents, poorly designed pre-clinical investigations, the possible effects of routinely administered agents that might unknowingly already have protected the myocardium or that might have blocked protection, and the biological differences of the myocardium in humans and experimental animals. A better understanding of the pathobiology of myocardial infarction is needed to stem this reperfusion injury. P2Y12 receptor antagonists minimize platelet aggregation and are currently part of the standard treatment to prevent thrombus formation and propagation in STEMI protocols. Serendipitously, these P2Y12 antagonists also dramatically attenuate reperfusion injury in experimental animals and are presumed to provide a similar protection in STEMI patients. However, additional protective agents are needed to further diminish reperfusion injury. It is possible to achieve additive protection if the added intervention protects by a mechanism different from that of P2Y12 antagonists. Inflammation is now recognized to be a critical factor in the complex intracellular response to ischemia and reperfusion that leads to tissue necrosis. Interference with cardiomyocyte inflammasome assembly and activation has shown great promise in attenuating reperfusion injury in pre-clinical animal models. And the blockade of the executioner protease caspase-1, indeed, supplements the protection already seen after the administration of P2Y12 antagonists. Importantly, protective interventions must be applied in the first minutes of reperfusion, if protection is to be achieved. The promise of such a combination of protective strategies provides hope that the successful attenuation of reperfusion injury is attainable.

Platelets in Myocardial Ischemia/Reperfusion Injury

Coronary artery disease, including myocardial infarction (MI), remains a leading cause of global mortality. Rapid reperfusion therapy is key to the improvement of patient outcome but contributes substantially to the final cardiac damage. This phenomenon is called "ischemia/reperfusion injury (IRI)." The underlying mechanisms of IRI are complex and not fully understood. Contributing cellular and molecular mechanisms involve the formation of microthrombi, alterations in ion concentrations, pH shifts, dysregulation of osmolality, and, importantly, inflammation. Beyond their known action as drivers of the development of coronary plaques leading to MI, platelets have been identified as important mediators in myocardial IRI. Circulating platelets are activated by the IRI-provoked damages in the vascular endothelium. This leads to platelet adherence to the reperfused endothelium, aggregation, and the formation of microthrombi. Furthermore, activated platelets release vasoconstrictive substances, act via surface molecules, and enhance leukocyte infiltration into post-IR tissue, that is, via platelet-leukocyte complexes. A better understanding of platelet contributions to myocardial IRI, including their interaction with other lesion-associated cells, is necessary to develop effective treatment strategies to prevent IRI and further improve the condition of the reperfused myocardium. In this review, we briefly summarize platelet properties that modulate IRI. We also describe the beneficial impacts of antiplatelet agents as well as their mechanisms of action in IRI beyond classic effects.

Assessment of myocardial salvage in patients with STEMI undergoing thrombolysis: ticagrelor versus clopidogrel

Background

In the setting of ST-segment elevation myocardial infarction (STEMI), the faster and stronger antiplatelet action of ticagrelor compared to clopidogrel, as well as its pleiotropic effects, could result in a greater degree of cardioprotection and final infarct size (FIS) limitation. The aim of our study was to comparatively evaluate the effect of ticagrelor and clopidogrel on myocardial salvage index (MSI) in STEMI patients undergoing thrombolysis.

Methods

Forty-two STEMI patients treated with thrombolysis were randomized to receive clopidogrel (n = 21) or ticagrelor (n = 21), along with aspirin. Myocardial area at risk (AAR) was calculated according to the BARI and the APPROACH jeopardy scores. FIS was quantified by cardiac magnetic resonance imaging (CMR) performed 5–6 months post-randomization. MSI was calculated as (AAR-FIS)/AAR × 100%. Primary endpoint of our study was MSI. Secondary endpoints were FIS and CMR-derived left ventricular ejection fraction (LVEF) at 5 –6 months post-randomization.

Results

By using the BARI score for AAR calculation, mean MSI was 52.25 ± 30.5 for the clopidogrel group and 54.29 ± 31.08 for the ticagrelor group (p = 0.83), while mean MSI using the APPROACH score was calculated at 51.94 ± 30 and 53.09 ± 32.39 (p = 0.9), respectively. Median CMR-derived FIS—as a percentage of LV—was 10.7% ± 8.25 in the clopidogrel group and 12.09% ± 8.72 in the ticagrelor group (p = 0.6). Mean LVEF at 5–6 months post-randomization did not differ significantly between randomization groups.

Conclusions

Our results suggest that the administration of ticagrelor in STEMI patients undergoing thrombolysis offer a similar degree of myocardial salvage, compared to clopidogrel.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02735-1.

Efficacy and Safety of Abbreviated Eptifibatide Treatment in Patients With ST-Segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention

The glycoprotein IIb/IIIa inhibitor eptifibatide, administered as bolus followed by infusion, is an adjunctive antithrombotic treatment during primary percutaneous coronary intervention (PCI) in selected patients with ST-segment elevation myocardial infarction (STEMI). Whether both bolus and infusion are necessary to improve outcomes is unknown. We hypothesized that primary PCI with eptifibatide bolus only is non-inferior to the conventional treatment (bolus and infusion) with regard to infarct size, while reducing bleeding complications. We analyzed 720 consecutive STEMI patients receiving eptifibatide bolus only or conventional treatment in an observational case-control study utilizing propensity score matching of clinical and intervention-specific confounders. Infarct size was estimated based on myocardial bound creatine kinase, creatine kinase (CK), and CK area under the curve values, with a prespecified non-inferiority margin of 20%. Major bleeding was defined as type 2, 3, or 5 on the Bleeding Academic Research Consortium classification. Eptifibatide bolus only was administered to 147 patients (20%), which were matched 1:1 to patients receiving conventional treatment. Based on peak myocardial bound creatine kinase, CK and CK area under the curve values, infarct size was -8.4% (95% CI [-31.2%, 14.4%]), -11.6% (95% CI [-33.5%, 10.3%]), and -13.9% (95% CI [-34.1%, 6.2%]) after eptifibatide bolus, respectively, reaching prespecified noninferiority compared with conventional treatment. Bolus treatment significantly reduced major bleeding complications (OR 0.48, 95% CI [0.30, 0.79]). In conclusion, eptifibatide given as abbreviated bolus only to selected STEMI patients who underwent primary PCI was noninferior regarding infarct size and resulted in less bleeding complications compared with conventional bolus and infusion treatment.

Meta-analysis Comparing Outcomes of Type 2 Myocardial Infarction and Type 1 Myocardial Infarction With a Focus on Dual Antiplatelet Therapy

BACKGROUND

There are important knowledge gaps in type 2 myocardial infarction (T2MI). Our primary objective was to compare the outcomes of patients with T2MI with those of patients with type 1 myocardial infarction (T1MI). Our secondary objective was to determine whether randomized controlled trials (RCTs) evaluating dual antiplatelets (DAPTs) have explicitly included patients with T2MI.

METHODS

We performed a meta-analysis comparing outcomes of patients with T2MI with patients with T1MI and a separate systematic review to evaluate the inclusion of T2MI in RCTs evaluating DAPT. There were 19 cohorts enrolling 48,829 patients (40,604 with T1MI and 5361 with T2MI) and 51 RCTs enrolling 188,132 patients with acute coronary syndrome.

RESULTS

Patients with T2MI had approximately 2-fold increases in unadjusted odds of long-term mortality compared with patients with T1MI (odds ratio, 2.47; 95% confidence interval, 2.06-2.96; P < 0.0001) and a 45% increase in adjusted odds of long-term mortality (odds ratio, 1.45; 95% confidence interval, 1.25-1.69; P < 0.0001, respectively). There was no published evaluation of efficacy, effectiveness, and safety of DAPT in patients with T2MI.

CONCLUSION

Patients with T2MI are at increased risk of adjusted all-cause long-term mortality compared with patients with T1MI. The role of DAPT remains unclear in T2MI.

Health-related risk behaviors among myocardial infarction survivors in the United States: A propensity score matched study

BACKGROUND

According to the American College of Cardiology/the American Heart Association (ACC/AHA) recommendations, health-related risk behaviors for secondary prevention of myocardial infarction (MI) are critical to determine.

OBJECTIVE

This study aimed to compare health-related risk behaviors between MI survivors and propensity-score-matched non-MI controls using nationally representative data.

METHODS

This cross-sectional, matched case-control study used publicly available Behavioral Risk Factor Surveillance System (BRFSS) 2017 data. Older adults with MI were propensity-score-matched to their non-MI controls. The 10 dependent variables included body mass index (BMI), smoking status, heavy alcohol consumption, influenza vaccine, length of time since last routine and cholesterol checkup, alcohol consumption, fruit and vegetable consumption, and physical activity. Chi-square tests and binomial logistic regression were used to examine the health-related risk behaviors differences between MI survivors and propensity-score-matched non-MI controls.

RESULTS

The final study sample consisted of 18,021 MI survivors and 54,063 non-MI controls after propensity score matching. Multivariable logistic regression analysis showed significant differences between MI survivors and matched non-MI controls in terms of cholesterol checkup, smoking status, and alcohol consumption. For example, multivariate analysis of health-related risk behaviors showed MI survivors were more likely to be smokers (AOR = 1.46, 95% CI: 1.28-1.68).

CONCLUSION

Based on this national survey of adults, MI survivors were more likely to be smokers but less likely to consume alcohol compared to their propensity-score-matched controls. Moreover, MI survivors were more likely to have their cholesterol checkup within the past 2 years compared to matched non-MI controls. Although lower alcohol consumption and greater chances of cholesterol checkups are reassuring health-related behaviors, interventions are needed to minimize the chances of smoking in this population.

Comparison of the Effects of Ticagrelor and Clopidogrel on Microvascular Dysfunction in Patients With Acute Coronary Syndrome Using Invasive Physiologic Indices

Background:

Ticagrelor reduced the rate of myocardial infarction and death compared with clopidogrel in patients with acute coronary syndrome. However, little is understood about chronic treatment of ticagrelor on microvascular dysfunction. The objective of this study was to assess the impact of ticagrelor maintenance treatment on microvascular system and coronary flow in comparison with clopidogrel.

Methods:

This study was a nonblinded, open-label, parallel-group, prospective, randomized controlled trial that enrolled 120 patients with acute coronary syndrome requiring stent implantation. Patients were randomized into the ticagrelor (180 mg loading dose, 90 mg twice daily thereafter) or clopidogrel (300 to 600 mg loading dose, 75 mg daily thereafter) group. The primary end point was coronary microvascular dysfunction as measured by an index of microcirculatory resistance (IMR) at 6 months after treatment.

Results:

The baseline clinical characteristics and physiological parameters, such as fractional flow reserve, coronary flow reserve, and IMR, did not differ between the ticagrelor and clopidogrel groups. Six-month follow-up physiological data showed that the IMR value was significantly lower in the ticagrelor group than the clopidogrel group (15.57±5.65 versus 21.15±8.39, P <0.01), and coronary flow reserve was higher in the ticagrelor group than in the clopidogrel group (3.85±0.72 versus 3.37±0.76, P <0.01). However, there was no difference in fractional flow reserve (0.87±0.08 versus 0.87±0.09, P =0.94) between the 2 groups. The improvement in IMR after 6 months of treatment was higher in the ticagrelor group ( P <0.01). Analyses of 223 nonculprit vessels of registered patients based on physiological results showed no differences in baseline fractional flow reserve (0.93±0.13 versus 0.92±0.09, P =0.58), coronary flow reserve (3.62±1.27 versus 3.51±1.24, P =0.16), or IMR (21.37±12.37 versus 24.19±21.08, P =0.22) or in follow-up fractional flow reserve (0.91±0.09 versus 0.91±0.08, P =0.67), coronary flow reserve (3.91±1.22 versus 3.75±1.16, P =0.36), or IMR (19.43±10.32 versus 21.52±18.90, P =0.34) between the 2 groups.

Conclusions:

Compared with clopidogrel, 6 months of ticagrelor therapy significantly improved microvascular dysfunction in acute coronary syndrome patients with stent implantation.

Clinical Trial Registration:

URL: https://www.clinicaltrials.gov . Unique identifier: NCT02618733.

Outcomes Among Clopidogrel, Prasugrel, and Ticagrelor in ST-Elevation Myocardial Infarction Patients Who Underwent Primary Percutaneous Coronary Intervention From the TOTAL Trial

BACKGROUND

Robust comparisons between oral P2Y12 inhibitors (clopidogrel, prasugrel, ticagrelor) in ST-elevation myocardial infarction (STEMI) patients who undergo primary percutaneous coronary intervention are lacking. We sought to evaluate outcomes on the basis of P2Y12 inhibitor therapy in patients from the Thrombectomy With PCI Versus PCI Alone in Patients With STEMI Undergoing Primary PCI (TOTAL) trial.

METHODS

We grouped 9932 patients according to P2Y12 inhibitor at hospital discharge: clopidogrel (n = 6500; 65.5%), prasugrel (n = 1244; 12.5%), or ticagrelor (n = 2188; 22.0%). The primary composite end point of cardiovascular death, recurrent myocardial infarction, cardiogenic shock, or New York Heart Association class IV heart failure was examined at 1 year. Secondary efficacy and safety end points were also assessed. Cox proportional hazard ratios were determined and adjusted for confounders via propensity scoring.

RESULTS

Baseline characteristics differing between the 3 groups were mainly age 75 years or older, diabetes, and previous stroke. After adjustment, ticagrelor use was associated with a lower rate of the primary composite outcome compared with clopidogrel (adjusted hazard ratio [aHR], 0.72; 95% confidence interval [CI], 0.57-0.91; P < 0.02) and prasugrel (aHR, 0.65; 95% CI, 0.48-0.89; P = 0.02). Prasugrel use was not associated with a lower rate of the primary outcome compared with clopidogrel (aHR, 1.09; 95% CI, 0.86-1.39; P > 0.99). Neither prasugrel nor ticagrelor were associated with increased risk of stroke compared with clopidogrel. Compared with clopidogrel, ticagrelor was associated with significantly lower rates of major bleeding.

CONCLUSIONS

In this observational analysis of STEMI patients who underwent primary percutaneous coronary intervention, ticagrelor was associated with improved outcomes compared with clopidogrel and prasugrel. An appropriately powered randomized trial is needed to confirm these findings.

Is ticagrelor worth its high cost and side-effects?

Ticagrelor is a reversible P2Y₁₂ receptor antagonist that is more potent than clopidogrel. When used in combination with aspirin, it reduces cardiovascular events in patients with acute coronary syndrome. However, unbiased review of 5 randomised controlled trials indicates that although statistically significant, the clinical superiority of ticagrelor over clopidogrel is modest. Thus, identification of patients who benefit the most from ticagrelor is a priority. Besides bleeding issues, ticagrelor can frequently cause bouts of dyspnoea, which requires ticagrelor replacement by another P2Y₁₂ receptor antagonist, with a loading dose.

Modern Management of ST-Segment Elevation Myocardial Infarction

Disruption of intracoronary plaque with thrombus formation resulting in severe or total occlusion of the culprit coronary artery provides the pathophysiologic foundation for ST-segment elevation myocardial infarction (STEMI). Management of STEMI focuses on timely restoration of coronary blood flow along with antithrombotic therapies and secondary prevention strategies. The purpose of this review is to discuss the epidemiology, pathophysiology, and diagnosis of STEMI. In addition, the review will focus on guideline-directed therapy for these patients and review potential associated complications.

In-Hospital Outcomes of Dual Loading Antiplatelet Therapy in Patients 75 Years and Older With Acute Coronary Syndrome Undergoing Percutaneous Coronary Intervention: Findings From the CCC-ACS (Improving Care for Cardiovascular Disease in China-Acute Coronary Syndrome) Project

BACKGROUND

Elderly patients with acute coronary syndrome (ACS) are at high risk for ischemic and bleeding events. This study aimed to evaluate the clinical effectiveness and safety of dual loading antiplatelet therapy for patients 75 years and older undergoing percutaneous coronary intervention for ACS.

METHODS AND RESULTS

The Improving Care for Cardiovascular Disease in China-ACS project was a collaborative study of the American Heart Association and Chinese Society of Cardiology. A total of 5887 patients 75 years and older with ACS who had percutaneous coronary intervention and received dual antiplatelet therapy with aspirin and P2Y12 inhibitors (clopidogrel or ticagrelor) between November 2014 and June 2017 were enrolled. The primary effectiveness and safety outcomes were in-hospital major adverse cardiovascular events and major bleeding. Hazard ratios (HRs) of in-hospital outcomes with different loading statuses of antiplatelet therapy were estimated using Cox proportional hazard models with multivariate adjustment. A propensity score-matched analysis was also conducted. Compared with patients receiving a dual nonloading dose, patients taking a dual loading dose had increased risks of both major adverse cardiovascular events (HR, 1.66, 95% confidence interval, 1.13-2.44; [P=0.010]) and major bleeding (HR, 2.34, 95% confidence interval, 1.75-3.13; [P<0.001]). Among 3284 propensity score-matched patients, a dual loading dose was associated with a 1.36-fold risk of major adverse cardiovascular events (HR, 1.36; 95% confidence interval, 0.88-2.11 [P=0.168]) and a 2.08-fold risk of major bleeding (HR, 2.08; 95% confidence interval, 1.47-2.93 [P<0.001]).

CONCLUSIONS

A dual loading dose of antiplatelet therapy was associated with increased major bleeding risk but not with decreased major adverse cardiovascular events risk among patients 75 years and older undergoing percutaneous coronary intervention for ACS in China.

CLINICAL TRIAL REGISTRATION

URL: http://www.ClinicalTrials.gov. Unique identifier: NCT02306616.

The extent of P2Y12 inhibition by clopidogrel in diabetes mellitus patients with acute coronary syndrome is not related to glycaemic control: Roles of white blood cell count and body weight

It was the study objective to determine whether glycaemic control affects the extent of platelet inhibition by thienopyridines as assessed by vasodilator-stimulated phosphoprotein flow cytometry (VASP-FCT) in patients with diabetes mellitus (DM) undergoing percutaneous coronary intervention (PCI) during acute coronary syndrome (ACS). Although the proportion of high on-treatment residual platelet reactivity is higher in DM, the contributions of glycaemic control and other factors associated with DM, such as excess body weight and inflammation, to this impaired platelet inhibition by thienopyridines have not yet been fully characterised. In this study, the extent of P2Y12 ADP receptor pathway inhibition was evaluated by the VASP-FCT. Platelet activation was expressed as the platelet reactivity index (PRI). Low response to clopidogrel (LR) was defined as a PRI of >61%. Four hundred forty-five consecutive ACS patients (DM = 160, NDM = 285) were enrolled. The proportion of LR was higher in DM patients (50 vs. 37.5%). In DM, PRI was not correlated with glycosylated haemoglobin (HbA1c) or glycaemia. In a univariate analysis, LR was associated with age, male sex, overweight, and white blood cell count (WBC). In a multivariate analysis, WBC >10,000 and body weight >80 kg were the sole independent predictors of LR to clopidogrel (hazard ratio (HR) 3.02 [1.36–6.68], p=0.006 and HR 2.47 [1.14–5.35], p = 0.021, respectively). Conversely, in non-DM patients, ST-elevation myocardial infarction was the sole independent predictor of LR. In conclusion, in ACS DM patients undergoing PCI, the extent of P2Y12 inhibition by clopidogrel is not related to glycaemic control but is related to body weight and inflammatory status as assessed by the WBC.

Impact of Double Loading Regimen of Clopidogrel on Final Angiographic Results, Incidence of Upper Gastrointestinal Bleeding and Clinical Outcomes in Patients with STEMI Undergoing Primary Coronary Intervention

This study tested the therapeutic impact of double-loading dose (i.e., 600 mg) versus standard-loading dose (i.e., 300 mg) of clopidogrel on ST-segment-elevation-myocardial-infarction (STEMI) patients undergoing primary-coronary-intervention (PCI).Between January 2005 and December 2013, a total of 1461 STEMI patients undergoing PCI were consecutively enrolled into the study and categorized into group 1 (600 mg/clopidogrel; n = 508) and group 2 (300 mg/clopidogrel; n = 953). We assessed angiographic thrombolysis-in-myocardial-infarction (TIMI) flow in the infarct-related-artery, 30-day mortality and upper-gastrointestinal-bleeding (UGIB) within 30 days as primary-endpoints and later incidents of UGIB as secondary-endpoints.The results showed that the incidences of advanced Killip score (defined as ≥ score 3) upon presentation (23.8% versus 24.6%) and advanced heart failure (defined as ≥ NYHAFc-3) (10.2% versus 10.4%) did not differ between groups 1 and 2 (all P > 0.4). Primary-endpoints, which were final TIM-3 flow (91.3% versus 91.7%) in the infarct-related-artery, incidences of 30-day mortality (5.8% vs. 7.1%), and UGIB ≤ 30 day (7.8% versus 8.9%) did not differ between group 1 and group 2 (all P > 0.33). The secondary-endpoints which were incidences of ≥ 30-day < one-year (5.2% versus 4.7) and > one-year (8.9% versus 10.1%) UGIB did not differ between groups 1 and 2 (all P > 0.45). One-year mortality did not differ between two groups (10.74% versus 12.9%) (P > 0.25). Multiple-stepwise-logistic-regression analysis showed that age and advanced-Killip score were independently predictive of 30-day mortality (all P < 0.001).Double-loading dose of clopidogrel did not confer an additional benefit to the final angiograph results, 30-day/one-year clinical outcomes; and age and advanced Killip-score were powerful predictors of 30-day mortality.

Antiplatelet Therapy and Clinical Outcomes Following Myocardial Infarction Among Patients in a U.S. Employer-Based Insurance Database

BACKGROUND

Estimates of residual cardiovascular risks among patients who have experienced a recent acute myocardial infarction (MI) are predominantly derived from secondary prevention trial populations, patient registries, and population-based cohorts.

OBJECTIVE

To generate real-world evidence of antiplatelet treatment and recurrent events following MI in patients on antiplatelet treatment among commercial, employer-based insured patients in a large administrative database.

METHODS

This was a retrospective cohort claims database study using the Truven Health MarketScan Commercial Claims and Encounters and Medicare Supplemental databases between 2007-2011. Patients with an acute MI hospitalization with a discharge date between 2008 and 2010 were included. Excluded were those patients with documentation of stroke, transient ischemic attack (TIA), or severe bleeding at or before index hospitalization and with concomitant use of anticoagulant therapy following index hospitalization. Patients treated with clopidogrel following the index MI hospitalization were followed up to 1 year for repeat MI, stroke, and coronary revascularization.

RESULTS

Among 33,943 post-MI continuous clopidogrel users without history of stroke, TIA, or bleeding, 22% had diabetes, whereas angina and renal impairment were less prevalent (5% and 7%, respectively). Over the 1-year follow-up, 2.4% experienced a repeat MI or stroke, and 8.2% underwent coronary revascularization. Angina, diabetes, and renal impairment were associated with elevated 1-year risk of repeat MI or stroke.

CONCLUSIONS

This study suggests that there is residual cardiovascular risk, although relatively low, in an insured, secondary prevention population on antiplatelet treatment following an MI. In patients with MI, identifying angina, diabetes, and renal impairment may aid risk stratification and guide the effective management of these higher-risk patients.

DISCLOSURES

Funding for this research was provided by Merck & Co. Although Merck & Co. formally reviewed a penultimate draft, the opinions expressed are those of the authorship and may not necessarily reflect those of the company. Reed Chase, Wu, Mavros, Heithoff, and Hanson are employees of Merck Sharp & Dohme, a subsidiary of Merck & Co., and may own stock and/or hold stock options in the company. Patel was an employee of Merck & Co. during the conduct of this study and preparation of the manuscript. Simpson is a paid consultant for Merck, Pfizer, and Amgen and has received speaker's fees from Merck and Pfizer. Study concept and design were contributed by all authors except Hanson. Heifhoff and Patel collected the data, and data interpretation was performed by Simpson, Mavros, Patel, Wu, and Hanson. The manuscript was written by Hanson, Mavros, and Patel and revised by Heithoff, Wu, Simpson, and Reed Chase.

Clinical pathways and management of antithrombotic therapy in patients with acute coronary syndrome (ACS): a Consensus Document from the Italian Association of Hospital Cardiologists (ANMCO), Italian Society of Cardiology (SIC), Italian Society of Emergency Medicine (SIMEU) and Italian Society of Interventional Cardiology (SICI-GISE)

Antiplatelet therapy is the cornerstone of the pharmacologic management of patients with acute coronary syndrome (ACS). Over the last years, several studies have evaluated old and new oral or intravenous antiplatelet agents in ACS patients. In particular, research was focused on assessing superiority of two novel platelet ADP P2Y12 receptor antagonists (i.e., prasugrel and ticagrelor) over clopidogrel. Several large randomized controlled trials have been undertaken in this setting and a wide variety of prespecified and post-hoc analyses are available that evaluated the potential benefits of novel antiplatelet therapies in different subsets of patients with ACS. The aim of this document is to review recent data on the use of current antiplatelet agents for in-hospital treatment of ACS patients. In addition, in order to overcome increasing clinical challenges and implement effective therapeutic interventions, this document identifies all potential specific care pathway for ACS patients and accordingly proposes individualized therapeutic options.

The risk of bleeding with the use of antiplatelet agents for the treatment of cardiovascular disease

INTRODUCTION

In the presence of injured coronary vascular endothelium, platelets become activated to form hemostatic plugs. While this represents a normal healing response to disrupted vascular endothelium, occlusive cardiovascular disease, as a result of maladaptive thrombus formation, is a major cause of morbidity and mortality. Due to the platelet predominance of arterial thrombi, antiplatelet agents are the mainstay of therapy for arterial cardiovascular disease, though come with a significantly increased risk of bleeding. Areas covered: This review will provide a comprehensive overview of available antiplatelet agents used to treat coronary artery cardiovascular disease. The risks of bleeding with each agent will be considered. Expert opinion: Available antiplatelet therapies are effective in treating acute thrombotic events and preventing recurrent events, however, they also carry significant bleeding risks. The decision to use or continue antiplatelet agents remains challenging for physicians and necessitates a thorough understanding of the future risk of thrombotic risks of thrombotic or bleeding events in a patient. Clinical prediction rules and risk scores may be useful to support physician decision-making.

In vivo MRI and ex vivo histological assessment of the cardioprotection induced by ischemic preconditioning, postconditioning and remote conditioning in a closed-chest porcine model of reperfused acute myocardial infarction: importance of microvasculature

BACKGROUND

Cardioprotective value of ischemic post- (IPostC), remote (RIC) conditioning in acute myocardial infarction (AMI) is unclear in clinical trials. To evaluate cardioprotection, most translational animal studies and clinical trials utilize necrotic tissue referred to the area at risk (AAR) by magnetic resonance imaging (MRI). However, determination of AAR by MRI' may not be accurate, since MRI-indices of microvascular damage, i.e., myocardial edema and microvascular obstruction (MVO), may be affected by cardioprotection independently from myocardial necrosis. Therefore, we assessed the effect of IPostC, RIC conditioning and ischemic preconditioning (IPreC; positive control) on myocardial necrosis, edema and MVO in a clinically relevant, closed-chest pig model of AMI.

METHODS AND RESULTS

Acute myocardial infarction was induced by a 90-min balloon occlusion of the left anterior descending coronary artery (LAD) in domestic juvenile female pigs. IPostC (6 × 30 s ischemia/reperfusion after 90-min occlusion) and RIC (4 × 5 min hind limb ischemia/reperfusion during 90-min LAD occlusion) did not reduce myocardial necrosis as assessed by late gadolinium enhancement 3 days after reperfusion and by ex vivo triphenyltetrazolium chloride staining 3 h after reperfusion, however, the positive control, IPreC (3 × 5 min ischemia/reperfusion before 90-min LAD occlusion) did. IPostC and RIC attenuated myocardial edema as measured by cardiac T2-weighted MRI 3 days after reperfusion, however, AAR measured by Evans blue staining was not different among groups, which confirms that myocardial edema is not a measure of AAR, IPostC and IPreC but not RIC decreased MVO.

CONCLUSION

We conclude that IPostC and RIC interventions may protect the coronary microvasculature even without reducing myocardial necrosis.

Prognostic Factors in Patients With Stemi Undergoing Primary PCI in the Clopidogrel Era: Role of Dual Antiplatelet Therapy at Admission and the Smoking Paradox on Long-Term Outcome

BACKGROUND

Several clinical and laboratory variables have an impact on the prognosis of STEMI patients undergoing PPCI; however, little is known about the role of ongoing DAPT at the time of the event and the smoking status as prognostic factors affecting the outcome of these patients.

METHODS AND RESULTS

Seven-hundred and thirteen consecutive STEMI patients undergoing PPCI, admitted to the S. Anna and S. Sebastiano Hospital (Caserta, Italy) and to the OLV Clinic (Aalst, Belgium), between March 2009 and December 2011, were retrospectively enrolled. Rescue PCI was the only exclusion criterion. Primary end-point was the combination of death for all causes, re-infarction, stroke, and target lesion revascularization (TLR). Patients already on DAPT at admission (26.4%) showed a significant increase in the event rate at univariate analysis (HR 2.34, CI 1.62-3.75, P < 0.05), while current smokers (56.5%) had a lower event rate, as compared to non-smokers (HR 0.67, CI 0.46-0.96, P < 0.05). In smoking patients already on DAPT at admission, a lower event rate was observed than in non-smoking patients on DAPT. Although, patients already on DAPT had a higher-risk profile (renal impairment, ongoing statin treatment, ST resolution <50%, and Killip class >1 were more frequently present than in patients not on DAPT), Cox regression analysis confirmed that both DAPT (HR 1.74, 95%CI 1.20-2.53, P < 0.01) and smoking status (HR 0.69, 95%CI 0.48-1.00, P < 0.05) retained their statistical significance, as they and were significantly associated with a worse and a better outcome, respectively, underlying their role as independent prognostic factors.

CONCLUSIONS

Not being a current smoker and ongoing DAPT at admission, in patients with STEMI undergoing PPCI, represent independent negative prognostic value.

In-stent thrombosis when switching ticagrelor to clopidogrel after percutaneous coronary intervention

Dual antiplatelet therapy with aspirin and a P2Y12 receptor blocker has been proven to reduce subsequent cardiovascular events and in-stent thrombosis in patients undergoing percutaneous coronary intervention. Newer P2Y12 antagonists with faster onset and greater inhibition of platelet activity have improved cardiovascular outcomes but have created uncertainty with the appropriate dosing when switching between agents. Currently, there are no evidence-based guidelines to aid clinicians when switching between P2Y12 receptor blockers. Here we describe two patients that developed in-stent thrombosis when switching from ticagrelor to clopidogrel using a 300 mg clopidogrel loading dose. Both patients presented with ST elevation myocardial infarction and underwent stent placement but then developed in-stent thrombosis 48 hours after switching from ticagrelor to clopidogrel. These cases illustrate the severe consequences of suboptimal platelet inhibition and the need for prospective trials thoroughly powered to assess clinical outcomes in order to determine the most appropriate strategy when switching from ticagrelor to clopidogrel.

Randomised trial to compare a protective effect of Clopidogrel Versus TIcagrelor on coronary Microvascular injury in ST-segment Elevation myocardial infarction (CV-TIME trial)

AIMS

Ticagrelor has shown greater, more rapid and more consistent platelet inhibition than clopidogrel. However, the superiority of ticagrelor for preventing ischaemic damage in STEMI patients has not been proven. The aim of this trial was to assess whether ticagrelor is superior to clopidogrel in preventing microvascular injury in ST-elevation myocardial infarction (STEMI).

METHODS AND RESULTS

Patients with STEMI underwent prospective random assignment to receive a loading dose (LD) of clopidogrel 600 mg or ticagrelor 180 mg (1:1 ratio) before primary percutaneous coronary intervention (PCI). As the primary endpoint, the index of microcirculatory resistance (IMR) was measured immediately after primary PCI. The secondary endpoint was the infarct size estimated from the wall motion score index (WMSI). A total of 76 patients were enrolled (clopidogrel group=38, ticagrelor group=38). The IMR in the ticagrelor group was significantly lower than that in the clopidogrel group (22.2±18.0 vs. 34.4±18.8 U, p=0.005). Cardiac enzymes were less elevated in the ticagrelor group than in the clopidogrel group (CK peak; 2,651±1,710 vs. 3,139±2,698 ng/ml, p=0.06). Infarct size, estimated by WMSI, was not different between the ticagrelor and clopidogrel groups at baseline (1.55±0.30 vs. 1.61±0.29, p=0.41) or after three months (1.42±0.33 vs. 1.47±0.33, p=0.57).

CONCLUSIONS

In patients with STEMI treated by primary PCI, a 180 mg LD of ticagrelor might be more effective in reducing microvascular injury than a 600 mg LD of clopidogrel, as demonstrated by IMR immediately after primary PCI.

Splenic release of platelets contributes to increased circulating platelet size and inflammation after myocardial infarction

Acute myocardial infarction (AMI) is characterized by a rapid increase in circulating platelet size but the mechanism for this is unclear. Large platelets are hyperactive and associated with adverse clinical outcomes. We determined mean platelet volume (MPV) and platelet-monocyte conjugation (PMC) using blood samples from patients, and blood and the spleen from mice with AMI. We further measured changes in platelet size, PMC, cardiac and splenic contents of platelets and leucocyte infiltration into the mouse heart. In AMI patients, circulating MPV and PMC increased at 1-3 h post-MI and MPV returned to reference levels within 24 h after admission. In mice with MI, increases in platelet size and PMC became evident within 12 h and were sustained up to 72 h. Splenic platelets are bigger than circulating platelets in normal or infarct mice. At 24 h post-MI, splenic platelet storage was halved whereas cardiac platelets increased by 4-fold. Splenectomy attenuated all changes observed in the blood, reduced leucocyte and platelet accumulation in the infarct myocardium, limited infarct size and alleviated cardiac dilatation and dysfunction. AMI-induced elevated circulating levels of adenosine diphosphate and catecholamines in both human and the mouse, which may trigger splenic platelet release. Pharmacological inhibition of angiotensin-converting enzyme, β1-adrenergic receptor or platelet P2Y12 receptor reduced platelet abundance in the murine infarct myocardium albeit having diverse effects on platelet size and PMC. In conclusion, AMI evokes release of splenic platelets, which contributes to the increase in platelet size and PMC and facilitates myocardial accumulation of platelets and leucocytes, thereby promoting post-infarct inflammation.

Improving myocardial injury, infarct size, and myocardial salvage in the era of primary PCI for STEMI

ST-segment elevation myocardial infarction (STEMI) is a major cause of mortality and disability worldwide. Reperfusion therapy by thrombolysis or primary percutaneous coronary intervention (PPCI) improves survival and quality of life in patients with STEMI. Despite the proven efficacy of timely reperfusion, mortality from STEMI remains high, particularly among patients with suboptimal reperfusion. Reperfusion injury following opening of occluded coronary arteries mitigates the efficacy of PPCI by further accentuating ischemic damage and increasing infarct size (IS). On the basis of experimental studies, it is assumed that nearly 50% of the final IS is because of the reperfusion injury. IS is a marker of ischemic damage and adequacy of reperfusion that is strongly related to mortality in reperfused patients with STEMI. Many therapeutic strategies including pharmacological and conditioning agents have been proven effective in reducing reperfusion injury and IS in preclinical research. Mechanistically, these agents act either by inhibiting reperfusion injury cascades or by activating cellular prosurvival pathways. Although most of these agents/strategies are at the experimental stage, some of them have been tested clinically in patients with STEMI. This review provides an update on key pharmacological agents and postconditioning used in the setting of PPCI to reduce reperfusion injury and IS. Despite intensive research, no strategy or intervention has been shown to prevent reperfusion injury or enhance myocardial salvage in a consistent manner in a clinical setting. A number of novel therapeutic strategies to reduce reperfusion injury in the setting of PPCI in patients with STEMI are currently under investigation. They will lead to a better understanding of reperfusion injury and to more efficient strategies for its prevention.

Ticagrelor vs clopidogrel followed by ticagrelor re-loading in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention: A randomized, pharmacodynamic comparison

Among patients allocated to ticagrelor in the primary percutaneous coronary intervention (PCI) cohort of Platelet Inhibition and Patient Outcomes (PLATO) trial, 40.7% had received pre-randomization 600 mg of clopidogrel. This scenario is frequently employed in real-world practice. In a prospective, three-center, single-blind, parallel design study, 74 P2Y12 inhibitor-naive patients undergoing primary PCI were randomized (Hour 0) to ticagrelor 180 mg loading dose (LD) vs clopidogrel 600 mg LD followed after 2 h by ticagrelor 180 mg re-LD. Platelet reactivity (VerifyNow, in PRU) was assessed at Hour 0, 2, 4, 6, and 24. The primary comparison was non-inferiority of ticagrelor to clopidogrel followed by ticagrelor re-LD regarding platelet reactivity at 24 h using a prespecified margin of <35 PRU for the upper bound of the one-sided 97.5% confidence interval (CI). Ticagrelor was proven non-inferior to clopidogrel followed by ticagrelor re-LD with a difference between arms of 13.5 PRU (28.8 upper 97.5% CI), p = 0.001. At Hour 2, platelet reactivity was lower in ticagrelor only vs clopidogrel followed by ticagrelor re-LD groups with least square estimate mean difference (95% CI) -105.7 (-140.6 to -70.8), p < 0.001, without significant difference thereafter. In conclusion, in patients undergoing primary PCI, a strategy of ticagrelor LD only was proven non-inferior to clopidogrel LD followed by ticagrelor re-LD, in terms of antiplatelet efficacy at 24 h post-randomization and provided an earlier onset of platelet inhibition.

Ticagrelor Protects the Heart Against Reperfusion Injury and Improves Remodeling After Myocardial Infarction

Objective—

In addition to P2Y 12 receptor antagonism, ticagrelor inhibits adenosine cell uptake. Prior data show that 7-day pretreatment with ticagrelor limits infarct size. We explored the acute effects of ticagrelor and clopidogrel on infarct size and potential long-term effects on heart function.

Approach and Results—

Rats underwent 30-minute ischemia per 24-hour reperfusion. (1) Ticagrelor (10 or 30 mg/kg) or clopidogrel (12.5 mg/kg) was given via intraperitoneal injection 5 minutes before reperfusion. (2) Rats received ticagrelor acute (intraperitoneal; 30 mg/kg), chronic (oral; 300 mg/kg per day) for 4 weeks starting 1 day after reperfusion or the combination (acute+chronic). Another group received clopidogrel (intraperitoneal [12.5 mg/kg]+oral [62.5 mg/kg per day]) for 4 weeks. (1) Ticagrelor dose-dependently reduced infarct size, 10 mg/kg (31.5%±1.8%; P <0.001) and 30 mg/kg (21.4%±2.6%; P <0.001) versus control (45.3±1.7%), whereas clopidogrel had no effect (42.4%±2.6%). Ticagrelor, but not clopidogrel, increased myocardial adenosine levels, increased phosphorylation of Akt, endothelial NO synthase, and extracellular-signal-regulated kinase 1/2 4 hours after reperfusion and decreased apoptosis. (2) After 4 weeks, left ventricular ejection fraction was reduced in the vehicle-treated group (44.8%±3.5%) versus sham (77.6%±0.9%). All ticagrelor treatments improved left ventricular ejection fraction, acute (69.5%±1.6%), chronic (69.2%±1.0%), and acute+chronic (76.3%±1.2%), whereas clopidogrel had no effect (37.4%±3.7%). Ticagrelor, but not clopidogrel, attenuated fibrosis and decreased collagen-III mRNA levels 4 weeks after ischemia/reperfusion. Ticagrelor, but not clopidogrel, attenuated the increase in proinflammatory tumor necrosis factor-α, interleukin-1β, and interleukin-18, and increased anti-inflammatory 15-epi-lipoxin-A 4 levels.

Conclusions—

Ticagrelor, but not clopidogrel, administered just before reperfusion protects against reperfusion injury. This acute treatment or chronic ticagrelor for 4 weeks or their combination improved heart function, whereas clopidogrel, despite achieving a similar degree of platelet inhibition, had no effect.

Signalling pathways and mechanisms of protection in pre- and postconditioning: historical perspective and lessons for the future

Ischaemic pre- and postconditioning are potent cardioprotective interventions that spare ischaemic myocardium and decrease infarct size after periods of myocardial ischaemia/reperfusion. They are dependent on complex signalling pathways involving ligands released from ischaemic myocardium, G-protein-linked receptors, membrane growth factor receptors, phospholipids, signalling kinases, NO, PKC and PKG, mitochondrial ATP-sensitive potassium channels, reactive oxygen species, TNF-α and sphingosine-1-phosphate. The final effector is probably the mitochondrial permeability transition pore and the signalling produces protection by preventing pore formation. Many investigators have worked to produce a roadmap of this signalling with the hope that it would reveal where one could intervene to therapeutically protect patients with acute myocardial infarction whose hearts are being reperfused. However, attempts to date to show efficacy of such an intervention in large clinical trials have been unsuccessful. Reasons for this inability to translate successes in the experimental laboratory to the clinical arena are evaluated in this review. It is suggested that all patients with acute coronary syndromes currently presenting to the hospital and being treated with platelet P2Y12 receptor antagonists, the current standard of care, are indeed already benefiting from protection from the conditioning pathways outlined earlier. If that proves to be the case, then future attempts to further decrease infarction will have to rely on interventions which protect by a different mechanism.

What is Wrong With Cardiac Conditioning? We May be Shooting at Moving Targets

Early recanalization of the occluded culprit coronary artery clearly reduces infarct size in both animal models and patients and improves clinical outcomes. Unfortunately, reperfusion can seldom be accomplished before some myocardium infarcts. As a result there has been an intensive search for interventions that will make the heart resistant to infarction so that reperfusion could salvage more myocardium. A number of interventions have been identified in animal models, foremost being ischemic preconditioning. It protects by activating signaling pathways that prevent lethal permeability transition pores from forming in the heart’s mitochondria at reperfusion. Such conditioning can be accomplished in a clinically relevant manner either by staccato reperfusion (ischemic postconditioning) or by pharmacological activation of the conditioning signaling pathways prior to reperfusion. Unfortunately, clinical trials of ischemic postconditioning and pharmacologic conditioning have been largely disappointing. We suggest that this may be caused by inappropriate use as models intended to mimic the clinical scenario of young healthy animals that receive none of the many drugs currently given to our patients. Patients may be resistant to some forms of conditioning because of comorbidities, for example, diabetes, or they may already be conditioned by adjunct medications, for example, P2Y12 inhibitors or opioids. Incremental technological improvements in patient care may render some approaches to cardioprotection redundant, and thus the clinical target may be continually changing, while our animal models have not kept pace. In remote conditioning, a limb is subjected to ischemia/reperfusion prior to or during coronary reperfusion. Its mechanism is not as well understood as that of ischemic preconditioning, but the results have been very encouraging. In the present article, we will review ischemic, remote, and pharmacologic conditioning and possible confounders that could interfere with their efficacy in clinical trials in 2 settings of myocardial ischemia: (1) primary angioplasty in acute myocardial infarction and (2) elective angioplasty.

Contemporary Antiplatelet Strategies in the Treatment of STEMI using Primary Percutaneous Coronary Intervention

Reperfusion therapy for patients presenting with an acute ST-segment elevation myocardial infarction (STEMI) involves primary percutaneous coronary intervention (PPCI) and concomitant oral antiplatelet and intravenous antithrombotic pharmacotherapy. There is a conflict between the desire to reduce the time between first medical contact and coronary re-canalisation and achieving effective platelet inhibition with oral antiplatelet agents. This review outlines the currently available antiplatelet treatments, and their place within the therapeutic timeline of a patient presenting with STEMI. Additionally, we focus on current challenges associated with effective antiplatelet treatment, including acute stent thrombosis (AST), the effect of morphine, platelet function assessment and concomitant anticoagulant therapy.

Outcome comparison of 600 mg versus 300 mg loading dose of clopidogrel for patients with ST-elevation myocardial infarction: a meta-analysis

BACKGROUND

A 600-mg loading dose (LD) of clopidogrel has been shown to be superior to a 300-mg LD in inhibiting platelet function. However, data for clinical superiority are limited, and there is a paucity of adequately powered randomized trials investigating this issue. This meta-analysis was performed to determine the optimal LD of clopidogrel in ST-elevation myocardial infarction patients treated with primary percutaneous coronary intervention.

METHODS

A meta-analysis of controlled trials and observational studies was performed comparing 600-mg with 300-mg LDs of clopidogrel. The primary efficacy end point was a major adverse cardiac event (MACE), and the primary safety end point was major bleeding. Data were extracted on an intention to treat basis. The X2 test was used to evaluate heterogeneity. A random effects model was used, and odds ratios (OR) were calculated using the Mantel-Haenszel method.

RESULTS

Nine studies involving 18 623 patients were included in the efficacy analysis. Mean duration of follow-up was 8 months. Four studies were eligible for the safety analysis. The MACE risk was lower with a 600-mg LD (7.0% [650/9231]) than with a 300-mg LD (9.2% [867/9392]; OR, 0.75; 95% CI, 0.63-0.91). On the other hand, there was no significant difference in the major bleeding events between the 2 groups (2.5% [89/3551] with 600 mg vs 2.3% [63/2796] with 300 mg; OR, 0.84; 95% CI, (0.60-1.16).

CONCLUSIONS

In ST-elevation myocardial infarction patients treated with primary percutaneous coronary intervention, administration of a 600-mg LD of clopidogrel is associated with a lower risk of MACE than is administration of a 300-mg LD, without increasing the risk of major bleeding.

Early high-dose rosuvastatin and cardioprotection in the protective effect of rosuvastatin and antiplatelet therapy on contrast-induced acute kidney injury and myocardial damage in patients with acute coronary syndrome (PRATO-ACS) study

BACKGROUND

There is a strong correlation between adverse clinical events and peak values of myocardial necrosis markers in non-ST-elevation acute coronary syndrome patients. In this clinical setting, high-dose statin treatment exerts acute beneficial effects against renal and myocardial damage. The aim of this report was to evaluate if, on admission, high-dose rosuvastatin can exert cardioprotective effects when administered in addition to high-dose clopidogrel.

METHODS

In the PRATO-ACS trial, 504 consecutive statin-naïve non-ST-elevation acute coronary syndrome patients scheduled for early invasive strategy and pretreated with high-dose clopidogrel were randomly assigned to rosuvastatin (40 mg on admission followed by 20 mg/d; statin group, n = 252) or no statin treatment (control group, n = 252). Serial myocardial biomarker samples were collected before and after angiography and/or percutaneous coronary intervention. The primary end point was the peak level of cardiac troponin I (cTnI) during the index event.

RESULTS

Statin-treated patients presented median cTnI peak values similar to controls (3.9 [0.6-12.8] vs 3.5 [1.2-11.9] ng/mL, respectively; P = .60]; no differences were found between the 2 groups in cTnI and creatine kinase-MB values at any time point, in either preangiography and postangiography peak values or their cumulative release. In patients submitted to percutaneous coronary intervention, periprocedural myocardial infarction occurred in 8 (4.7%) of 171 statin-treated and 7 (4.3%) of 162 control patients (P = .87).

CONCLUSION

In the PRATO-ACS trial, early high-dose rosuvastatin did not show cardioprotective effects when administered in addition to high-dose clopidogrel.

ST elevation myocardial infarction: recent advances and updates

ST elevation myocardial infarction (STEMI) remains a leading cause of morbidity, mortality and disability worldwide. Statistically, a trend towards improvements in morbidity and mortality has been consistent over the years, which is attributed primarily to the modification of risk factors, healthier lifestyles, treatment advances and better management of door-to-balloon times via STEMI systems. However, a major challenge in the coming years will be the baby boomers (born between the years 1946 and 1964) coming into old age. The first baby boomers turned 65 in year 2011. As the baby boomers age in the coming years, the incidence of coronary heart disease is likely to increase, and so there will be a greater need to have major advances in the management of coronary heart disease in order to deal with this additional incidence. The scope of this article is to review recent advances in the management of STEMI and to provide an updated overview.

Meta-analysis of randomized clinical trials comparing bivalirudin versus heparin plus glycoprotein IIb/IIIa inhibitors in patients undergoing percutaneous coronary intervention and in patients with ST-segment elevation myocardial infarction

This study sought to investigate the relative safety and efficacy of bivalirudin versus heparin plus glycoprotein (GP) IIb/IIIa inhibitors in patients undergoing percutaneous coronary intervention (PCI) and in those with ST-segment elevation myocardial infarction (STEMI). The safety of bivalirudin in PCI, particularly in patients with STEMI, continues to be debated. We searched the on-line databases for randomized controlled trials of bivalirudin versus heparin plus GP IIb/IIIa inhibitors. Data on study design, inclusion and exclusion criteria, sample characteristics, and clinical outcomes at 30 days were extracted. A total of 19,856 PCI patients included in 7 randomized trials and 5,820 patients with STEMI included in 2 randomized trials were separately analyzed. At 30 days, bivalirudin use in patients undergoing PCI resulted in similar rates of death, myocardial infarction, repeat revascularization, and stent thrombosis. In patients with STEMI, bivalirudin use resulted in decreased cardiac mortality (risk ratio [RR] 0.70, 95% confidence interval [CI] 0.50 to 0.97, p=0.03) compared with heparin plus GP IIb/IIIa inhibitors but an increase in definite stent thrombosis at 30 days (RR 1.88, 95% CI 1.09 to 3.24, p=0.02) driven by an increase in acute stent thrombosis (RR 5.48, 95% CI 2.30 to 13.07, p=0.0001). Bivalirudin use was associated with a decrease in Thrombolysis In Myocardial Infarction (TIMI) major (RR 0.58, 95% CI 0.46 to 0.74, p<0.0001) and TIMI minor (RR 0.55, 95% CI 0.48 to 0.63, p<0.0001) bleeding rates in PCI patients as well as in a subgroup of patients with STEMI. In conclusion, in PCI patients anticoagulation with bivalirudin results in similar ischemic adverse events and a reduction in TIMI major and minor bleeding at 30 days compared with heparin plus GP IIb/IIIa inhibitors. In patients with STEMI, bivalirudin use is associated with a reduction in TIMI major and minor bleeding and fewer deaths from cardiac causes but an increase in acute and 30-day definite stent thrombosis.

Pharmacologic Therapy for Reducing Myocardial Infarct Size in Clinical Trials

In patients with acute ST-segment elevation myocardial infarction, early, successful, and durable reperfusion therapy optimizes the likelihood of favorable outcomes. Fibrinolysis and primary percutaneous coronary intervention improve survival compared to no reperfusion therapy in large part by reducing infarct size (IS) and preserving left ventricular ejection fraction. There is direct correlation between IS and clinical outcomes. In this article, we will review some of the more promising pharmacological agents geared toward reduction in IS, discuss the major pathways that can lead to this desirable outcome, and evaluate the results of clinical trials performed with these and other compounds.

Triple therapy greatly increases myocardial salvage during ischemia/reperfusion in the in situ rat heart

BACKGROUND

Cangrelor, a P2Y12 receptor blocker, administered just prior to reperfusion reduced but did not eliminate myocardial infarction in rabbits. Combining cangrelor with ischemic postconditioning offered no additional protection suggesting they protected by a similar mechanism. To determine if cangrelor's protection might be additive to other cardioprotective interventions we tested cangrelor in combination with ischemic preconditioning, cariporide, a sodium-hydrogen exchange blocker, and mild hypothermia.

METHODS

Open-chest rats underwent 30-min coronary occlusion/2-h reperfusion.

RESULTS

Cangrelor, administered as a bolus (60 μg/kg) 10 min before reperfusion and continued as an infusion (6 μg/kg/min) for the duration of the experiment, decreased infarction from 45.3 % of risk zone in control hearts to 25.0 %. Combining cangrelor and ischemic preconditioning offered no additional protection. Mild hypothermia (32-33 °C) instituted by peritoneal lavage with cold saline just prior to coronary occlusion resulted in 25.2 % infarction, and combining cangrelor and hypothermia nearly halved infarction to 14.1 % of risk zone. Cariporide (0.5 mg/kg) just prior to occlusion resulted in 27.2 % infarction and 15.8 % when combined with cangrelor. Combining cangrelor, hypothermia and cariporide further halved infarction to only 6.3 %. We also tested another P2Y12 inhibitor ticagrelor which is chemically similar to cangrelor. Ticagrelor (20 mg/kg) fed 1 h prior to surgery reduced infarct size by an amount similar to that obtained with cangrelor (25.6 % infarction), and this protective effect was abolished by chelerythrine and wortmannin, thus implicating participation of PKC and PI3-kinase, resp., in signaling.

CONCLUSIONS

Cardioprotection from a P2Y12 receptor antagonist can be combined with at least 2 other strategies to magnify the protection. Combining multiple interventions that use different cardioprotective mechanisms could provide powerful protection against infarction in patients with acute coronary thrombosis.

The randomized physiologic assessment of thrombus aspiration in patients with acute ST-segment elevation myocardial infarction trial (PATA STEMI): study rationale and design

INTRODUCTION

Routine thrombus aspiration is proposed to be superior to conventional primary percutaneous coronary intervention (PCI) in terms of improved myocardial perfusion, in patients with ST-segment elevation acute myocardial infarction (STEMI). However, myocardial perfusion after thrombus aspiration has not been evaluated by a quantitative, invasive method. We intend to determine whether manual thrombus aspiration in the infarct-related coronary artery increases myocardial perfusion assessed by index of microcirculatory resistance (IMR) compared with conventional primary PCI.

STUDY DESIGN

PATA STEMI is a single-center, prospective, randomized trial with a planned inclusion of 128 patients with the first STEMI. Prior to coronary angiography, patients are randomly assigned to thrombus aspiration using the Eliminate aspiration catheter (Terumo Medical Supply, Japan) or to conventional primary PCI. After completion of primary PCI, IMR is determined both in infarct-related artery and in noninfarct-related arteries without critical stenoses. The primary end-point is a group mean value of IMR after thrombus aspiration compared with conventional primary PCI. Secondary end-points are myocardial perfusion grade, resolution of ST-segment elevation, enzymatic estimation of infarct size, left ventricular remodeling assessed by echocardiographic indices, and major adverse cardiac events rate at 1, 6, and 12 months.

CONCLUSION

If manual thrombus aspiration significantly reduces microcirculatory resistance, thereby improving myocardial perfusion, it may become the routine strategy in primary PCI.

Current state of clinical translation of cardioprotective agents for acute myocardial infarction

There is continued interest in the concept of limiting myocardial infarct size with adjunctive agents administered along with reperfusion injury; however, there remains considerable controversy in the literature. The purpose of this article is to review the medical literature on clinical trials performed during the past 3 years that have attempted to reduce myocardial infarct size by administration of adjunctive therapies along with reperfusion therapy. A PubMed-driven literature search revealed a host of clinical trials focusing on the following prominent types of therapies: endogenous conditioning (postconditioning and remote ischemic conditioning); rapid cooling; pharmacological therapy (cyclosporine, abciximab, clopidogrel, tirofiban, erythropoietin, thrombus aspiration, adenosine, glucose-insulin-potassium, statins, antidiabetic agents, FX06, iron chelation, and ranolazine). Although there remains some controversy, quite a few of these studies showed that adjunctive therapy further reduced myocardial infarct size when coupled with reperfusion. Antiplatelet agents are emerging as some of the newest agents that seem to have cardioprotective capabilities. Postconditioning has become a bit more controversial in the clinical literature; remote conditioning, early and rapid cooling, adenosine, and ranolazine are intriguing therapies deserving of larger studies. Certain agents and maneuvers, such as erythropoietin, protein kinase C δ inhibitors, iron chelation, and intra-aortic balloon counterpulsation, perhaps should be retired. The correct adjunctive therapy administered along with reperfusion has the capability of further reducing myocardial injury during ST-segment-elevation myocardial infarction.

P2Y12 receptor gene polymorphism and antiplatelet effect of clopidogrel in patients with coronary artery disease after coronary stenting

Platelets have a central role in the pathophysiology of thrombosis. Adenosine diphosphate (ADP) plays a pivotal role as an agonist of platelet activation. Genetic polymorphisms of the P2Y12 ADP receptor might influence the activation of this receptor by ADP or the response of patients to platelet inhibitors. The present study was conducted on a total number of 80 participants, 40 patients were diagnosed with acute coronary syndrome and 40 sex and aged-matched healthy volunteers were included as controls. Platelet aggregation was assessed (before and 1 week after clopidogrel administration) and genotyping of the T744C genetic polymorphism of P2Y12 receptor gene was carried out using the restriction fragment length polymorphism polymerase chain reaction (PCR-RFLP) method. Platelet aggregation of the patients had a range of 54-183% before clopidogrel administration and had a range of 4-113% after its administration. Genotyping of the candidate gene revealed that 72.5% of the patients had a wild allele (TT), whereas 27.5% had a C allele (heterozygous CT, homozygous CC). On the contrary, 97.5% of controls had a wild allele (TT), whereas 2.5% had a C allele (heterozygous CT, homozygous CC). Our study elicited an association between the T744C polymorphism of the P2Y12 ADP receptor gene and platelet reactivity. Carrying the C allele at this position is associated with an increased platelet activation response to ADP.

Long-term safety of drug-eluting stents

Stent implantation in coronary stenosis has revolutionized the treatment of coronary artery disease. The introduction of antirestenotic drug coatings further improved their efficacy in reducing target vessel revascularizations. With increasing use of drug-eluting stents (DES), stent thrombosis (ST) rose as potentially fatal major complication. Initially, the incidence of ST late after stent implantation seemed to be similar for DES and bare metal stents until several studies proved otherwise in first-generation DES. Since then, the design and components of DES have been changed and new polymers, drugs and different combinations of platelet inhibitors have been introduced to further improve the safety of DES. In this review, the authors focus on the relationship between DES, lesion anatomy, implantation technique and pharmacology to avoid the occurrence of ST. Furthermore, the relationship between dual antiplatelet therapy, bleeding rate and its significant impact on patient outcome is discussed. Finally, some promising future concepts are highlighted.

Synergistic effect of thrombus aspiration and abciximab in primary percutaneous coronary intervention

BACKGROUND

Previous studies failed to assess the individual prognostic role of thrombus aspiration (TA) or abciximab in primary percutaneous coronary intervention (pPCI), due their prevalent combined use.

METHODS AND RESULTS

A total of 644 consecutive ST-segment elevation myocardial infarction patients treated with pPCI were included in this retrospective registry from January 2006 to December 2008. Patients were divided in: (a) Group 1, with conventional pPCI; (b) Group 2, with pPCI and abciximab; (c) Group 3, with pPCI and TA; (d) Group 4, with pPCI and abciximab plus TA. Primary end point was the composite of major adverse cardiovascular events (MACEs, defined as overall mortality, myocardial infarction, target vessel revascularization, and major bleedings) at 1 year. Baseline clinical and angiographic characteristics were not different among the groups, with the exception of a younger age in group 4. The two groups of patients treated with TA (group 3 and 4) received more frequently direct stenting (P < 0.001 vs. group 1 for both), presented higher rate of end-procedural TIMI flow grade 3 (P < 0.001 vs. group 1 for both), and lower rate of no-reflow (P = 0.016 and P < 0.001 vs. group 1, respectively). Patients of group 2 presented a borderline nonsignificant trend toward higher rate of end-procedural TIMI flow grade 3 (P = 0.083 vs. group 1). MACEs at 1 year were 43 (29%) in group 1 versus 25 (22%) in group 2 versus 24 (19%) in group 3 versus 32 (13%) in group 4 (log-rank P = 0.001). At the multivariate Cox regression analysis, combined TA plus abciximab in group 4 [hazard ratio (HR): 0.48, confidence interval (CI) 95% 0.28-0.84, P = 0.01] and a higher left ventricular ejection fraction (HR: 0.97, CI 95% 0.95-0.98, P < 0.001) were significantly associated with lower MACE rate.

CONCLUSIONS

The combination of pharmacologic and mechanic antithrombotic treatment during pPCI was associated with better 1-year clinical outcome.