Observer studies of image quality of denoising reduced-count cardiac single photon emission computed tomography myocardial perfusion imaging by three-dimensional Gaussian post-reconstruction filtering and deep learning

BACKGROUND

The aim of this research was to asses perfusion-defect detection-accuracy by human observers as a function of reduced-counts for 3D Gaussian post-reconstruction filtering vs deep learning (DL) denoising to determine if there was improved performance with DL.

METHODS

SPECT projection data of 156 normally interpreted patients were used for these studies. Half were altered to include hybrid perfusion defects with defect presence and location known. Ordered-subset expectation-maximization (OSEM) reconstruction was employed with the optional correction of attenuation (AC) and scatter (SC) in addition to distance-dependent resolution (RC). Count levels varied from full-counts (100%) to 6.25% of full-counts. The denoising strategies were previously optimized for defect detection using total perfusion deficit (TPD). Four medical physicist (PhD) and six physician (MD) observers rated the slices using a graphical user interface. Observer ratings were analyzed using the LABMRMC multi-reader, multi-case receiver-operating-characteristic (ROC) software to calculate and compare statistically the area-under-the-ROC-curves (AUCs).

RESULTS

For the same count-level no statistically significant increase in AUCs for DL over Gaussian denoising was determined when counts were reduced to either the 25% or 12.5% of full-counts. The average AUC for full-count OSEM with solely RC and Gaussian filtering was lower than for the strategies with AC and SC, except for a reduction to 6.25% of full-counts, thus verifying the utility of employing AC and SC with RC.

CONCLUSION

We did not find any indication that at the dose levels investigated and with the DL network employed, that DL denoising was superior in AUC to optimized 3D post-reconstruction Gaussian filtering.

The Medicare Appropriate Use Criteria Program: A Review of Recommendations for Testing in Coronary Artery Disease

BACKGROUND

Congress established the Appropriate Use Criteria (AUC) Program to reduce unnecessary advanced imaging studies. Organizations that wish to develop AUC can apply to the Centers for Medicare & Medicaid Services (CMS) to qualify as provider-led entities (PLEs) under this program. Variable methods, content, and formatting of PLE-generated AUC could lead to clinician uncertainty about whether an advanced imaging test is appropriate or not.

PURPOSE

To review AUC published by CMS-qualified PLEs focused on advanced imaging tests for coronary artery disease (CAD), a "priority clinical area" identified by CMS.

DATA SOURCES

Publicly available data from the worldwide web searched on 29 August 2022.

STUDY SELECTION

Approved AUC with recommendations related to testing for CAD.

DATA EXTRACTION

Manual review of published AUC by all authors.

DATA SYNTHESIS

Among the 17 CMS-qualified PLEs, only 7 had published AUC related to CAD. Substantial variation in the methods and formatting of these AUCs was observed. The number of clinical scenarios covered ranged from 6 to 210, and the number of advanced imaging methods covered ranged from 1 to 25. When specifically applied to clinical scenarios, many AUC offered no guidance on appropriateness; those that did conflicted with respect to appropriateness.

LIMITATION

Other CMS-identified priority clinical areas were not evaluated.

CONCLUSION

CMS-qualified AUC for imaging of CAD are heterogeneous and sometimes discrepant, creating substantial potential for uncertainty among clinicians seeking to provide their patients with appropriate imaging tests.

PRIMARY FUNDING SOURCE

No funding was received for this study.

Burnout and Well-Being Among Cardiology Fellowship Program Directors

OBJECTIVES

The third annual Cardiovascular Diseases (CV) Fellowship Program Directors (PDs) Survey sought to understand burnout and well-being among CV fellowship PDs.

BACKGROUND

Physician burnout is a common phenomenon. Data on burnout among cardiologists, specifically CV PDs, remain limited.

METHODS

The survey contained 8 questions examining satisfaction, stress, and burnout among CV fellowship PDs. Burnout was defined based on the self-reported presence of ≥1 symptom of burnout, constant feelings of burnout, or complete burnout.

RESULTS

Survey response rate was 57%. Most respondents were men (78%) and 54% represented university-based programs. Eighty percent reported satisfaction with their current job as PD, and 96% identified interactions with fellows as a driver of their satisfaction. Forty-five percent reported feeling a great deal of stress from their job. Stress was higher among women PDs, early-career PDs, and PDs of larger and university-based programs. Twenty-one percent reported some symptoms of burnout, and only 36% reported enjoyment without stress or burnout. Rates of enjoyment without stress or burnout were higher among men and late-career PDs, PDs of smaller programs, and PDs of community-based programs. Seventeen percent of PDs reported a high likelihood of resigning in the next year, of which the most common reason was the tasks of PDs were becoming overwhelming.

CONCLUSIONS

Most CV fellowship PDs are satisfied with their position, but stress and burnout remain common. Women PDs, early-career PDs, and PDs of larger, university-based programs demonstrate more adverse markers of well-being. Opportunities exist to support CV fellowship PDs in their critical role.

Program Directors Survey on Diversity in Cardiovascular Training Programs

BACKGROUND

Women and minorities are under-represented in cardiovascular disease (CVD) specialties. It remains unknown how characteristics of the CVD learning environment affect diversity and how program directors (PDs) approach these critical issues.

OBJECTIVES

The second annual Cardiovascular PD Survey aimed to investigate characteristics of the CVD learning environment that may affect diversity and strategies PDs use to approach these issues.

METHODS

The survey contained 20 questions examining U.S.-based CVD PD perceptions of diversity in CVD and related characteristics of the CVD fellowship learning environment.

RESULTS

In total, 58% of PDs completed the survey. Responding programs demonstrated geographic diversity. The majority were university-based or -affiliated. A total of 86% of PDs felt diversity in CVD as a field needs to increase, and 70% agreed that training programs could play a significant role in this. In total, 89% of PDs have attempted to increase diversity in fellowship recruitment. The specific strategies used were associated with PD sex and the presence of under-represented minority trainees in the program. PDs identified lack of qualified candidates and overall culture of cardiology as the 2 most significant barriers to augmenting diversity. A majority of programs have support systems in place for minority fellows or specific gender groups, including procedures to report issues of harassment or an unsafe learning environment. PDs identified shared best practices for recruitment and implicit bias training, among others, as important resources in their efforts to support diversity in CVD training.

CONCLUSIONS

Diversity is important to CVD PDs. They are striving to increase it in their programs through recruitment and strategies directed toward the fellowship learning environment. The CVD community has opportunities to standardize strategies and provide national resources to support PDs in these critical efforts.

Surveillance and Management of Troponin Elevation after Vascular Surgery

BACKGROUND

Postopertive troponin elevation may occur without typical or atypical cardiac symptoms and is associated with an increased 30-day morbidity and mortality. The objective of the study was to implement a quality improvement initiative of postoperative troponin surveillance algorithm aimed at intensifying medical management after vascular surgery.

METHODS

We conducted a single-center study of postoperative troponin surveillance after vascular surgery (n = 201) at a tertiary care, academic medical center from January to December 2016. Troponin surveillance was performed on postoperative days 1-3 after carotid endarterectomy, endovascular aortic repair, infrainguinal bypass, open abdominal aortic aneurysm repair, peripheral vascular intervention, and suprainguinal bypass, regardless of cardiac symptoms. Patients with troponin I elevation (>0.034 ng/mL) were managed with a treatment algorithm which included single or dual antiplatelet (AP) agent, high-intensity statin therapy, smoking cessation consultation, and outpatient cardiology consultation and stress testing. Patients with troponin elevation ≥1.0 ng/mL received inpatient cardiology consultation. We assessed adherence to the protocol for intensification of best medical therapy defined as high-dose statin therapy, increase in AP therapy, and smoking cessation consultation according to the established algorithm.

RESULTS

Troponin elevation was recorded in 17% (34/201) of patients and was associated with cardiac symptoms in 8 patients (24%), while 26 (76%) patients had an asymptomatic abnormal troponin on postoperative surveillance. One patient was excluded due to death immediately after SUPRA, resulting in 200 patients. Troponin elevation ≥1.0 ng/mL occurred in 11 asymptomatic patients (5.5%). Any intensification of medical therapy was instituted in 76% of patients with elevated troponin and included high-intensity statin therapy (58%), increase in AP therapy (18%), and smoking cessation consultation (66%). Once an elevated troponin level was recognized, 52% of our patients received cardiology consultation with an increased likelihood (100%) in patients with troponin ≥1 ng/mL (P < 0.001). Adherence to outpatient stress testing was 66%. Intensification of medical therapy was not significantly different between patients with abnormal troponin values, >0.034-1.0 (n = 23) versus ≥1.0 ng/mL (n = 10); statin therapy (P = 1.0), AP (P = 0.34), and smoking cessation (P = 1.0). One-year mortality was higher in patients with postoperative troponin elevation than those with normal postoperative troponin levels (12% vs. 2.4%; P = 0.03).

CONCLUSIONS

Routine postoperative troponin surveillance results in intensification of statin therapy in patients with asymptomatic troponin elevation. Further study is needed to determine if this approach reduces long-term cardiovascular morbidity and mortality.

How to achieve patient-centered testing: role of the protocol nurse

INTRODUCTION

Patient-centered cardiac testing is predicated on choosing the right test for the right patient. We studied the effects of changing from script-driven scheduling to nurse-driven protocoling of stress tests.

METHODS AND RESULTS

A protocol nurse reviewed records before scheduling and communicated with patients and ordering providers if needed. We found that instituting nurse protocolling of all non-imaging (ETT) and nuclear (MPI) stress tests (N = 3071) resulted in protocol changes in 37% of our patients, and reduced the proportion of tests that could not be performed as scheduled by 56% and cancelations by 71% (P < 0.001 for each). These changes were sustained over two successive 6-month periods following a baseline observation period of 6 months. For MPI, the most frequent nurse interventions were re-protocoling as stress-first MPI (12% of tests), changing test location for clinical reasons (13%), changing stress modality (7%), and care coordination (5%).

CONCLUSIONS

Changing from script-driven scheduling to protocol nursing contributed measurably to patient-centered testing.

Procoagulant activity in stored units of red blood cells

The procoagulant activity (PA) of stored units of red blood cells (RBC) increases over time, which is related to the expression/exposure of tissue factor (TF). However, there is a discrepancy between the TF measured and changes in PA observed, suggesting that other blood components contribute to this activity. Our goal was to evaluate changes in PA of stored RBCs and to determine possible contributors to it. RBC units from 4 healthy donors were prepared and stored at 4 °C. On selected days, RBC aliquots were reconstituted with autologous plasma and tested in the thromboelastography assay. Corresponding supernatants were tested in a clotting assay. For all donors, the clotting time (CT) of reconstituted RBC units decreased from ∼3000-4000s on day 1 to ∼1000-1600s on day 30, with the most dramatic changes occurring between days 1 and 5. Anti-TF antibody slightly prolonged the CT. The concentration of TF did not change significantly over time and was within the range of 0.3-2.3 pM. Bovine lactadherin (LTD) prolonged the CT of the RBC (by 2.4-3.4-fold in days 3-5 and by 1.3-1.8-fold at day 30). Anti-TF antibody together with LTD had a cumulative effect on the CT prolongation. CT of supernatants responded to both anti-TF and anti-FXIa antibodies. Three contributors to the PA of stored RBC were identified, i.e. FXIa in solution and phosphatidylserine and TF exposed on blood cells and microparticles. Failure of LTD and antibodies to completely eliminate PA suggests that other components of blood could contribute to it.

Pharmacodynamic effects during the transition between cangrelor and ticagrelor

OBJECTIVES

This study sought to determine pharmacodynamic effects during transition from intravenous cangrelor to oral ticagrelor and from oral ticagrelor to intravenous cangrelor.

BACKGROUND

Cangrelor is an intravenous antagonist of P2Y12 and its use will require transition to and from oral agents.

METHODS

Patients (n = 12) with stable coronary artery disease who were taking aspirin 81 mg daily were recruited. On study day 1, they received a bolus plus 2-h infusion of cangrelor plus a 180-mg dose of ticagrelor at either 0.5 h (n = 6) or 1.25 h (n = 6). Pharmacodynamic effects (light transmission platelet aggregation in response to 20 and 5 μmol/l adenosine diphosphate, VerifyNow, P2Y12 assay (Accumetrics, San Diego, California), vasodilator-stimulated phosphoprotein index, and flow cytometry) were assessed during and after the cangrelor infusion. Patients took 90 mg of ticagrelor twice daily for either 6 (n = 6) or 7 (n = 6) doses. On study day 5, pharmacodynamic effects were assessed before and during a bolus plus 2-h infusion of cangrelor.

RESULTS

During cangrelor infusion, extensive inhibition of platelet function reflected by limited residual platelet reactivity was apparent. After cangrelor was stopped, the antiplatelet effects of ticagrelor were preserved despite a modest increase in platelet reactivity.

CONCLUSIONS

Ticagrelor given before or during infusion of cangrelor did not attenuate the pharmacodynamic effects of cangrelor. The pharmacodynamic effects of ticagrelor were preserved when ticagrelor was given during infusion of cangrelor. Consistent with the reversible binding of ticagrelor, this oral P2Y12 antagonist can be administered before, during, or after treatment with cangrelor.

Feasibility of stress only rubidium-82 PET myocardial perfusion imaging

BACKGROUND

Stress only SPECT myocardial perfusion imaging (MPI) is a validated strategy to streamline cardiac diagnostic imaging. The potential use of Rb82 PET stress only MPI has not been investigated.

METHODS AND RESULTS

Stress images from 200 Rb82 PET-MPI were reviewed by two blinded readers and categorized as not requiring additional rest images (normal) or requiring additional images (abnormal or equivocal). No additional images were deemed necessary for 95 (48%) and 99 (50%) by the two blinded readers. The stress only interpretation was compared to the previous read of the complete rest-stress study. The rate of detecting a normal result with stress only reading was 76%-79% with a negative predictive value of 94%-95%. Clinical predictors of a normal stress only PET-MPI included lower age, the absence of CAD, and female gender, but not body mass index. Blinded reads of 50 additional consecutive PET-MPI from patients with selected clinical predictors (age <65 years, no known CAD) were then performed. Of these, 40 (80%) were normal by previous rest-stress reading, and 34 (68%) were categorized as not requiring additional images after stress only reading. PET stress only imaging would have resulted in a mean reduction of radiation exposure of 2.4 mSv per study according to a published radiation estimate.

CONCLUSION

Stress only Rb82 PET-MPI is a feasible strategy to reduce resource utilization and radiation exposure associated with MPI. This strategy would be most applicable to patients with a lower pretest likelihood.

Reduction in treatment times through formalized data feedback: results from a prospective multicenter study of ST-segment elevation myocardial infarction

OBJECTIVES

This study sought to evaluate the effect of systematic data analysis and standardized feedback on treatment times and outcome in a prospective multicenter trial.

BACKGROUND

Formalized data feedback may reduce treatment times in ST-segment elevation myocardial infarction (STEMI).

METHODS

Over a 15-month period, 1,183 patients presenting with STEMI were enrolled. Six primary percutaneous coronary intervention hospitals in Germany and 29 associated nonpercutaneous coronary intervention hospitals participated. Data from patient contact to balloon inflation were collected and analyzed. Pre-defined quality indicators, including the percentage of patients with pre-announced STEMI, direct handoff in the catheterization laboratory, contact-to-balloon time <90 min, door-to-balloon time <60 min, and door-to-balloon time <30 min were discussed with staff on a quarterly basis.

RESULTS

Median door-to-balloon time decreased from 71 to 58 min and contact-to-balloon time from 129 to 103 min between the first and the fifth quarter (p < 0.05 for both). Contributing were shorter stays in the emergency department, more direct handoffs from ambulances to the catheterization laboratory (from 22% to 38%, p < 0.05), and a slight increase in the number of patients transported directly to the percutaneous coronary intervention facility (primary transport). One-year mortality was reduced in the total group of patients and in the subgroup of patients with primary transport (p < 0.05). The sharpest fall in mortality was observed in patients with primary transport and TIMI (Thrombolysis In Myocardial Infarction) risk score ≥ 3 (n = 521) with a decrease in 30-day mortality from 23.1% to 13.3% (p < 0.05) and in 1-year mortality from 25.6% to 16.7% (p < 0.05).

CONCLUSIONS

Formalized data feedback is associated with a reduction in treatment times for STEMI and with an improved prognosis, which is most pronounced in high-risk patients. (Feedback Intervention and Treatment Times in ST-Elevation Myocardial Infarction [FITT-STEMI]; NCT00794001).

Platelet-white blood cell (WBC) interaction, WBC apoptosis, and procoagulant activity in stored red blood cells

BACKGROUND

Nonleukoreduced units of red blood cells (RBCs) contain activated platelets (PLTs) that interact with white blood cells (WBCs) and may promote inflammation and thrombosis in the recipient. The aim of this study was to characterize PLT-WBC interactions (PLT-WBC aggregates [PLAs]), WBC apoptosis, WBC death, and the development of procoagulant activity in RBCs during storage.

STUDY DESIGN AND METHODS

RBCs were prepared from volunteer donor blood and stored. Samples were analyzed with flow cytometry between Days 1 and 15 to measure PLT-monocyte aggregate (PMA) and PLT-neutrophil aggregate (PNA) formation, WBC apoptosis (annexin V binding), and cell death (binding of 7-aminoactinomycin D). Procoagulant activity in the supernatant of four RBC preparations was assessed between Days 1 and 39 using a clotting assay with and without the addition of an inhibitory anti-tissue factor (TF) antibody, αTF-5.

RESULTS

PLA formation was extensive and maximal on Day 3 of storage (PNA, 23 ± 13%; PMA, 93 ± 4%; n = 6). Apoptosis was progressive throughout storage, with 95 ± 4% of neutrophils and 73 ± 19% of monocytes binding annexin V on Day 15. Cell death became measurable after apoptosis. Procoagulant activity was observed in all RBCs but with varying temporal patterns. It was partially TF dependent and removed with high-speed centrifugation, suggestive of an association with microparticles.

CONCLUSION

The activation of PLTs during the storage of RBCs induces PLA formation that precedes WBC apoptosis and death. Procoagulant activity, likely associated with microparticles derived from apoptotic WBCs, may contribute to adverse effects of stored, nonleukoreduced RBCs.

[Optimizing systems of care for patients with acute myocardial infarction. STEMI networks, telemetry ECG, and standardized quality improvement with systematic data feedback]

Rapid revascularization of the infarct-related artery importantly affects prognosis in the treatment of acute ST elevation myocardial infarction (STEMI). Treatment results can be improved significantly when a STEMI-specific structure of care is created and when systematic quality improvement measures are implemented. The necessary structural measures include establishing or participating in myocardial infarction networks. When local hospitals collaborate in a network, it becomes feasible to offer round-the-clock primary coronary intervention to patients of those participating hospitals that do not have a catheterization laboratory on site. Another important structural step is to acquire and install prehospital twelve-lead ECG systems capable of remote telemetric transmission. This provides a solid basis for diagnosing STEMI with speed and accuracy and can prove to be highly effective in anchoring the chain of alert and treatment. As a consequence, two important goals can be realized: (1) intentionally bypassing the non-interventional hospital, and (2) systematically bypassing the emergency room of the interventional center. Both of these measures entail important time savings. An efficient instrument for improving treatment times is the implementation of a standardized quality improvement process with formalized data collection and analysis as well as with systematic data feedback to all systems and individuals involved in the early phase of treating STEMI patients within the hospital network including the emergency medical responder systems. The positive effect of such data feedback on treatment quality is contingent on the perception by all those involved that the data obtained for each patient are absolutely valid. Thus, those data need to be verifiable and an independent monitoring process should be created.Furthermore, the systematic use of standardized risk scores should be promoted in an effort to compare and adjust patient risk when analyzing network data. It is critically important that all appropriate patients-including those with a high risk of mortality--have access to rapid interventional treatment. Only when the individual risk of treated patients is taken into account will it be possible to compare quality of care and mortality rates. In general, the comparison between different hospitals, systems and regions is highly problematic and not feasible without considering local factors. It harbors the danger of inducing changes in practice in order to compete rather than in order to advance patient care, and thus it may be counterproductive when such a comparison leads to the implication that treatment may have been inferior. Therefore, the comparison of results (e.g., treatment times and mortality rates) should be undertaken as much as possible within an established system, with the use of a "before and after" design. Quality, then, will be defined as a documented consistent effort to improve results, and this approach will be distinctly productive. It is of fundamental importance that the involved hospitals, physicians and emergency staff perceive themselves as a team. The structures and processes outlined above can and should be applied broadly. The necessary resources will need to be provided through political and societal consensus. The multicenter FITT-STEMI project ("Feedback Intervention and Treatment Times in ST-Elevation Myocardial Infarction") is currently pursuing such an approach.

The influence of platelet activating factor on the effects of platelet agonists and antiplatelet agents in vitro

We assessed the effect of the intercellular mediator of inflammation, platelet activating factor (PAF), on platelet function. The interaction between PAF and the platelet agonists ADP, thrombin and convulxin was analyzed in vitro in whole blood with the use of flow cytometry and was further characterized with the use of receptor antagonists to PAF (ABT-491), P2Y1 (MRS-2179), and P2Y12 (cangrelor) as well as a monoclonal anti-PSGL-1 antibody (anti-CD162). Low concentrations of PAF (0.1 nM) synergistically augmented platelet activation induced by other agonists (P < 0.01). Augmentation by PAF was receptor mediated and did not require platelet-leukocyte interaction. With >99% inhibition of P2Y receptor-mediated platelet activation, greater than additive activation was still observed with the combination of ADP plus PAF. Accordingly, PAF synergistically augments platelet activation in response to ADP and thrombin, and the extent of inhibition exerted by P2Y receptor antagonists is decreased in the presence of PAF.

Contact-to-balloon time and door-to-balloon time after initiation of a formalized data feedback in patients with acute ST-elevation myocardial infarction

For many patients with ST-segment elevation myocardial infarctions (STEMIs), the time from presentation to percutaneous coronary intervention exceeds established goals. This study was conducted to examine the effects of formalized data assessment and systematic feedback on treatment times. All patients with STEMIs treated with percutaneous coronary intervention in a semi-rural 3-hospital network from January 1, 2006, to December 31, 2006, were prospectively analyzed (n = 114). Patients presenting during the first 3-month period (January 1, 2006, to March 31, 2006) were included as the reference group (n = 33). Time points from initial contact with the medical system to revascularization were assessed, analyzed, and presented in an interactive session to hospital and emergency services staff members. Data from patients with STEMIs presenting during the next 3 quarters were presented in the same manner (n = 28, 25, and 28). The median contact-to-balloon time was 113 minutes in the reference quarter, decreasing to 83, 66, and 74 minutes in the intervention groups (p <0.0001), whereas the median door-to-balloon time decreased from 54 minutes in the reference group to 35, 31, and 26 minutes in the intervention groups (p <0.0001). The proportion of patients with contact-to-balloon times <90 minutes increased from 21% to 79% (p <0.0001). There were significant reductions in the durations of initial treatment on location and in the emergency room and in puncture-to-balloon-time in the catheterization laboratory, and more patients were transported directly to the catheterization laboratory, bypassing the emergency room (from 23% in the reference quarter to 76% in the last intervention quarter, p <0.0001). In conclusion, formalized data feedback leads to marked reduction in revascularization times in patients with STEMIs.

The effects of bivalirudin compared with those of unfractionated heparin plus eptifibatide on inflammation and thrombin generation and activity during coronary intervention

OBJECTIVE

To characterize effects of bivalirudin compared with unfractionated heparin plus eptifibatide on inflammation, and thrombin generation and activity after percutaneous coronary intervention.

METHODS

We measured the concentration in blood of fibrinopeptide A, prothrombin fragment 1+2, soluble CD40 ligand, interleukin 1 receptor antagonist, interleukin 6, and high sensitivity C-reactive protein in 63 patients treated with aspirin and clopidogrel and undergoing elective percutaneous coronary intervention, who were randomized to treatment with either bivalirudin (n=34) or unfractionated heparin plus eptifibatide (n=29).

RESULTS

Neither generation nor activity of thrombin increased 10 min after percutaneous coronary intervention in patients randomized to bivalirudin or unfractionated heparin plus eptifibatide. However, prothrombin fragment 1+2 increased modestly and comparably in both groups after 1 day. Inflammation, reflected by concentrations of interleukin 6 and high sensitivity C-reactive protein in blood, increased similarly 1 day after percutaneous coronary intervention in patients treated with either regimen. In a subset of patients (n=12 in each group) from whom blood was obtained 30 days after percutaneous coronary intervention, the concentration of high sensitivity C-reactive protein was lower in those who had been treated with bivalirudin (by 3.5 mg/l, P=0.002).

CONCLUSION

The early effects on inflammation and thrombin generation and activity are similar after treatment with bivalirudin alone compared with unfractionated heparin plus eptifibatide in patients treated with aspirin and clopidogrel who are undergoing percutaneous coronary intervention for symptoms of stable angina. The decreased concentration of high sensitivity C-reactive protein seen 30 days after percutaneous coronary intervention in those treated with bivalirudin is consistent with greater attenuation of inflammation that may have contributed to the trend toward reduced mortality 1 year later in those treated with bivalirudin in REPLACE-2.

Increased ability of tirofiban to maintain its inhibitory effects on the binding of fibrinogen to platelets in blood from patients with and without diabetes mellitus

OBJECTIVES

Both tirofiban and eptifibatide release rapidly from glycoprotein IIb-IIIa but have different dissociation constants (KD of tirofiban=15 nmol/l, of eptifibatide=120 nmol/l). Binding of fibrinogen to glycoprotein IIb-IIIa is biphasic, forming an initial reversible complex (KD=155-180 nmol/l) and a second more stable complex (KD=20-70 nmol/l). Diabetes is known to alter platelet function. To determine the influence of affinity on inhibitory effects in blood from patients with (n=20) and without (n=20) diabetes mellitus, we characterized the extent of inhibition as a function of time.

METHODS

Blood was added to reaction tubes containing tirofiban 100 ng/ml or eptifibatide 1.7 microg/ml (concentrations previously defined to be optimal) plus a platelet agonist (1 micromol/l adenosine diphosphate or 25 micromol/l thrombin receptor agonist peptide), and fluorochrome-labeled fibrinogen before analysis by flow cytometry.

RESULTS

The extent of inhibition early on (30 s to 3 min) was similar (>85%) with either agent in blood from those with and without diabetes mellitus, whereas the extent of inhibition 10-15 min later was maintained more effectively with tirofiban than with eptifibatide (difference in slope P<0.01). After 15 min, the extent of inhibition in response to adenosine diphosphate in those with diabetes mellitus was 95+/-6% for tirofiban and 70+/-15% for eptifibatide (P<0.001); in those without diabetes mellitus, it was 91+/-9% for tirofiban and 73+/-19% for eptifibatide (P<0.001).

CONCLUSION

For glycoprotein IIb-IIIa antagonists with a rapid rate of release, the biphasic binding of fibrinogen influences to a similar extent their ability to maintain inhibitory effects in blood from patients with and without diabetes mellitus.

Increased expression of platelet P-selectin and formation of platelet–leukocyte aggregates in blood from patients treated with unfractionated heparin plus eptifibatide compared with bivalirudin

INTRODUCTION

Platelet-leukocyte aggregates have been implicated in atherogenesis. This study was designed to determine the influence in vivo of a direct thrombin inhibitor, bivalirudin, compared with unfractionated heparin (UFH) plus the GP IIb-IIIa inhibitor eptifibatide (E) on platelet reactivity, the formation of platelet-leukocyte aggregates, and leukocyte activation.

MATERIALS AND METHODS

Blood was taken before and after percutaneous coronary intervention (PCI) from 60 patients randomized to UFH+E (n=26) or bivalirudin (n=34). Platelet function and the formation in vivo of platelet-monocyte aggregates (PMA) and platelet-neutrophil aggregates (PNA) were assessed with the use of flow cytometry. Myeloperoxidase (MPO) elaborated during leukocyte activation was measured by ELISA.

RESULTS

Compared with those treated with bivalirudin, patients treated with UFH+E exhibited a 45% decrease in the capacity of platelets to bind fibrinogen (p=0.006) but a 2-fold increase in platelet surface expression of P-selectin (p=0.04) in samples taken from the coronary ostium before PCI. Platelet-leukocyte aggregation in vivo was greater (PMA=2-fold, p=0.04; PNA=3-fold, p=0.006) with UFH+E as was the concentration in blood of MPO (1.5-fold, p=0.007).

CONCLUSIONS

Increased platelet surface expression of P-selectin, augmented platelet-leukocyte aggregation in vivo, and consequent activation of leukocytes was seen before PCI in blood from patients treated with UFH+E compared with bivalirudin. Benefits associated with decreased platelet aggregation when PCI is performed with UFH plus GP IIb-IIIa inhibition may be partially offset by increased platelet-leukocyte aggregation.

Augmentation of inhibitory effects of glycoprotein IIb-IIIa antagonists in patients with diabetes

BACKGROUND

Patients with diabetes mellitus and acute coronary syndromes (ACS) derive enhanced benefit from treatment with glycoprotein (GP) IIb-IIIa inhibitors. To determine mechanisms potentially responsible we characterized the binding of fibrinogen to platelets from patients with and without diabetes in the presence and absence of GP IIb-IIIa antagonists.

METHODS

GP IIb-IIIa antagonists (tirofiban, eptifibatide, and abciximab) were added in vitro to blood from patients with and without diabetes. Binding of fibrinogen to activated GP IIb-IIIa was assessed with the use of flow cytometry. The kinetics of binding of I(125)-abciximab and I(125)-fibrinogen to washed platelets from subjects with and without diabetes mellitus were determined. Glycation of platelet membrane proteins was measured with the fructosamine assay.

RESULTS

In the presence of GP IIb-IIIa antagonists, activation-induced binding of fibrinogen to platelets was reduced to a greater extent (p<0.02) in blood from patients with diabetes. The greater inhibition in blood from patients with diabetes was seen with pharmacologic concentrations of tirofiban (50 ng/ml, by 27%), eptifibatide (1.5 microg/ml, by 24%), and abciximab (2 mg/ml, by 12%). Whereas the binding of I(125)-abciximab was similar to platelets from patients with diabetes and those without, the rate of binding of I(125)-fibrinogen was decreased with platelets from patients with diabetes. Binding after 5 min was reduced by 46% in those with diabetes (p<0.05). Platelet membrane proteins from patients with diabetes were glycated to a greater extent compared with those without diabetes.

CONCLUSION

GP IIb-IIIa antagonists inhibit platelet activation to a greater extent in blood from patients with diabetes. The decreased rate of binding of fibrinogen early after activation of platelets appears to be a consequence of glycation and may promote inhibition by GP IIb-IIIa antagonists.

Relation of augmented platelet reactivity to the magnitude of distribution of atherosclerosis

The extent of luminal involvement of atherosclerotic vascular disease and platelet reactivity portend subsequent cardiovascular events. This study was designed to determine whether platelet reactivity correlates with the extent of the territorial distribution of vascular disease. Blood was obtained from 130 patients who had known atherosclerotic vascular disease categorized as being in > or =1 of the following territories: coronary artery disease (CAD; n = 89), cerebrovascular disease (n = 36), and peripheral arterial disease (n = 61). Platelet reactivity, i.e., the activation of platelets in response to a low concentration of adenosine diphosphate (0.2 micromol/L), was measured using flow cytometry. Patients with vascular disease in >1 territory compared with those with disease in only 1 territory had greater platelet reactivity with respect to P-selectin expression (p = 0.01). The percentages of platelets expressing P-selectin (mean +/- SD) were 6.4 +/- 4.2 in patients who had involvement of 1 territory (n = 88), 10.0 +/- 6.8 in those who had involvement of 2 territories (n = 28), and 10.1 +/- 9.9 in those who had involvement of 3 territories (n = 14). Patients who had CAD and diabetes mellitus had greater P-selectin expression than did those who had CAD without diabetes (p <0.02 for interaction). Thus, platelet reactivity is greater in patients who have more extensive territorial distribution of atherosclerotic vascular disease and in those who have CAD and diabetes mellitus. Accordingly, patients who have more widely distributed vascular disease are likely to derive particular benefit from antiplatelet regimens that suppress platelet function to a greater extent.

Effects of increased concentrations of glucose on platelet reactivity in healthy subjects and in patients with and without diabetes mellitus

Hyperglycemia has been linked to adverse outcomes after myocardial infarction. We characterized the effect of selected concentrations of glucose or mannitol on platelet function in whole blood samples from healthy volunteers and from patients with and without diabetes mellitus. Activation of platelet glycoprotein IIb/IIIa and P-selectin expression was increased similarly after addition of isosmotic concentrations of glucose and mannitol, suggesting that increased osmolarity associated with hyperglycemia increases platelet reactivity.