Fibrinogen and C-reactive protein on admission as markers of final infarct size after primary angioplasty for acute myocardial infarction

Association of myocardial hemorrhage and persistent microvascular obstruction with circulating inflammatory biomarkers in STEMI patients

INTRODUCTION

Myocardial hemorrhage (IMH) and persistent microvascular obstruction (MVO) are associated with impaired myocardial recovery and adverse clinical outcomes in STEMI patients. However, their relationship with circulating inflammatory biomarkers is unclear in human patients.

METHODS AND RESULTS

Twenty consecutive patients referred for primary percutaneous coronary intervention of first STEMI were included in a prospective study. Blood sampling was performed at admission, 4, 12, 24, 48 hours, 7 and 30 days after reperfusion for inflammatory biomarker (C reactive protein, fibrinogen, interleukin-6 (IL-6) and neutrophils count) assessment. At seven days, cardiovascular magnetic resonance (CMR) was performed for infarct size, MVO and IMH assessment. Median infarct size was 24.6% Interquartile range (IQR) [12.0-43.5] of LV mass and edema was 13.2% IQR [7.7-36.1] of LV mass. IL-6 reached a peak at H24 (5.6 pg/mL interquartile range (IQR) [2.5-17.5]), CRP at H48 (11.7 mg/L IQR [7.1-69.2]), fibrinogen one week after admission (4.4 g/L IQR [3.8-6.7]) and neutrophils at H12 (9.0 G/L IQR [6.5-12.7]). MVO was present in 11 patients (55% of the study population) and hemorrhage in 7 patients (35%). Patients with IMH had significantly higher IL-6, CRP, fibrinogen, and neutrophils levels compared to patients without IMH. Patients with persistent MVO had significantly higher CRP, fibrinogen and neutrophils level compared to patients without MVO, but identical IL-6 kinetics.

CONCLUSION

In human patients with acute myocardial infarction, intramyocardial hemorrhage appears to have a stronger relationship with inflammatory biomarker release compared to persistent MVO. Attenuating myocardial hemorrhage may be a novel target in future adjunctive STEMI treatments.

Acute Myocardial Infarction Biosensor: A Review From Bottom Up

Acute myocardial infarction (AMI) is a cardiovascular disease that is produced due to a deficiency of oxygen generating irreversible damage in the heart muscle. In diagnosis, electrocardiogram (ECG) investigation has been the main method but is insufficient, so approaches like the measurement of biomarkers levels in plasma or saliva have become one of the most commonly applied strategies for prognosis of AMI, as some of them are specifically related to a heart attack. Many tests are carrying on to determine biological markers changes, but usually, they present disadvantages related to time consumption and laborious work. To overcome the issues, researchers around the world have been developing different ways to enhance detection through the use of biosensors. These diagnostic devices have a biological sensing element associated to a physicochemical transducer that can be made from different materials and configurations giving place to different kinds of detection: Electrical/Electrochemical, Optical and Mechanical. In this review, the authors presents relevant investigations related to the most important biomarkers and biosensors used for their detection having in mind the nanotechnology participation in the process through the application of nanostructures as a good choice for device configuration.

Cardiac rupture complicating acute myocardial infarction: the clinical features from an observational study and animal experiment

BACKGROUND

Cardiac rupture (CR) is a fatal complication of ST-elevation myocardial infarction (STEMI) with its incidence markedly declined in the recent decades. However, clinical features of CR patients now and the effect of reperfusion therapy to CR remain unclear. We investigated the clinical features of CR in STEMI patients and the effect of reperfusion therapy to CR in mice.

METHODS

Two studies were conducted. In clinical study, data of 1456 STEMI patients admitted to the First Hospital, Xi'an Jiaotong University during 2015.12. ~ 2018.12. were analyzed. In experimental study, 83 male C57BL/6 mice were operated to induce MI. Of them, 39 mice were permanent MI (group-1), and remaining mice received reperfusion after 1 h ischemia (21 mice, group-2) or 4 h ischemia (23 mice, group-3). All operated mice were monitored up to day-10. Animals were inspected three times daily for the incidence of death and autopsy was done for all mice found died to determine the cause of death.

RESULTS

CR was diagnosed in 40 patients: free-wall rupture in 17, ventricular septal rupture in 20, and combined locations in 3 cases. CR presented in 19 patients at admission and diagnosed in another 21 patients during 1 ~ 14 days post-STEMI, giving an in-hospital incidence of 1.4%. The mortality of CR patients was high during hospitalization accounting for 39% of total in-hospital death. By multivariate logistic regression analysis, older age, peak CK-MB and peak hs-CRP were independent predictors of CR post-STEMI. In mice with non-reperfused MI, 17 animals (43.6%) died of CR that occurred during 3-6 days post-MI. In MI mice received early or delayed reperfusion, all mice survived to the end of experiment except one mouse died of acute heart failure.

CONCLUSION

CR remains as a major cause of in-hospital death in STEMI patients. CR patients are characterized of being elderly, having larger infarct and more server inflammation. Experimentally, reperfusion post-MI prevented CR.

Anti-inflammatory, Antithrombotic and Cardiac Remodeling Preventive Effects of Eugenol in Isoproterenol-Induced Myocardial Infarction in Wistar Rat

This study aimed to evaluate the antithrombotic, anti-inflammatory and anti-cardiac remodeling properties of eugenol in isoproterenol-induced myocardial infarction in rats. Male Wistar rats were randomly divided into four groups, control, iso [100 mg/kg body weight was injected subcutaneously into rats at an interval of 24 h for 2 days (6th and 7th day) to induce MI] and pretreated animals with clopidogrel (0.2 mg/kg) and eugenol (50 mg/kg) orally for 7 days and intoxicated with isoproterenol (Iso + Clop) and (Iso + EG) groups. Isoproterenol-induced myocardial infarcted rats showed notable changes in the ECG pattern, increase in heart weight index, deterioration in the hemodynamic function and rise in plasma level of troponin-T, CK-MB and LDH and ALT by 316, 74, 172 and 45 %, respectively, with histological myocardium necrosis and cells inflammatory infiltration. In addition, significant increases in plasma levels of inflammatory biomarkers such as fibrinogen, α1, α2, β1, β2 and γ globulins with decrease level of albumin were observed in infarcted rats as compared to normal ones. Else, the angiotensin-converting enzyme (ACE) activity in plasma, kidney and heart of the isoproterenol-induced rats was significantly increased by 34, 47 and 93 %, respectively, as compared to normal group. However, the administration of eugenol induced a clear improvement in cardiac biomarkers injury, reduced inflammatory mediators proteins, increased heart activities of superoxide dismutase and glutathione peroxidase with reduce in thiobarbituric acid-reactive substances content and inhibition of ventricular remodeling process through inhibition of ACE activity. Overall, eugenol evidences high preventive effects from cardiac remodeling process.

Impact of inflammation on adverse cardiovascular events in patients with acute coronary syndromes

AIMS

Inflammation is a key factor in the long-term outcome of acute coronary syndromes (ACS). The aim of the present study was to evaluate inflammatory markers in patients with ACS as predictors for major adverse cardiovascular events (MACE) and hard events.

METHODS

This study included 1548 patients with ACS. C-reactive protein (CRP), white blood count (WBC), and their subtypes were analyzed during hospitalization. Receiver operator characteristic (ROC) and Kaplan-Meier survival curves were used to assess the predictive value and hard events (nonfatal myocardial infarction and cardiac death) and MACE (hard events, hospitalization for cardiac causes, late revascularization and stroke) were obtained during 30 days.

RESULTS

ROC analysis of CRP and WBC to predict adverse events revealed cut-offs of 47.5 ng/l and 16.6 × 10/μl for MACE and 93.5 ng/l and 16.6 × 10/μl for hard events. The cumulative adverse event rates were significantly higher in patients with increased CRP (≥47.5 ng/l; 17 versus 4%, P < 0.001) and WBC (≥16.6 × 10/μl; 21 versus 5%, P < 0.001) for MACE and with elevated CRP (≥93.5 ng/l; 16 versus 2%, P < 0.001) and WBC (≥16.6 × 10/μl; 18 versus 2%, P < 0.001) for hard events, demonstrating highest event rates with elevation of both inflammatory markers: (28 versus 5%, P < 0.001) for MACE and (26 versus 2%, P < 0.001) for hard events. Analysis of CRP and WBC further revealed a substantial negative correlation with left ventricular function (P < 0.001). Moreover, markers of myocardial damage were significantly elevated in patients with abnormal CRP or WBC (P < 0.001).

CONCLUSION

Inflammatory markers such as CRP and WBC alone and, particularly, in combination are strong and independent predictors of outcome in patients with ACS.

Biomarkers of chronic inflammatory state in uremia and cardiovascular disease

Cardiovascular disease is the leading cause of death in the general population; traditional risk factors seem inadequate to explain completely the remarkable prevalence of cardiovascular mortality and morbidity observed in the uremic population. A role for chronic inflammation has been well established in the development of atherosclerotic disease, and, on the basis of these observations, atherosclerosis might be considered an inflammatory disease. Inflammation has been implicated in the etiology of coronary artery disease in the general population, and traditional inflammatory biomarkers such as C-reactive protein (CRP) and interleukin-6 (IL-6) have been shown to predict cardiovascular events in both symptomatic and asymptomatic individuals as well as those in the uremic population. Later on, new nontraditional markers were related to the risk of cardiovascular morbidity and mortality in general and in uremic population. As a consequence of the expanding research base and availability of assays, the number of inflammatory marker tests ordered by clinicians for cardiovascular disease (CVD) risk prediction has grown rapidly and several commercial assays have become available. So, up to now we can consider that several new nontraditional markers as CD40-CD40 ligand system and pentraxin-3 seem to be significant features of cardiovascular disease in general and in ESRD population.

Prognostic impact of baseline high-sensitivity C-reactive protein in patients with acute myocardial infarction undergoing percutaneous coronary intervention based on body mass index

BACKGROUND AND OBJECTIVES

Serum high sensitivity C-reactive protein (hs-CRP) is a marker of inflammation and may lead to the development of atherosclerosis, adversely affecting mortality. The aim of this study was to evaluate the relationship between baseline hs-CRP level and 12-month clinical outcomes in patients with acute myocardial infarction (AMI) undergoing percutaneous coronary intervention (PCI) according to their body mass index (BMI) status.

SUBJECTS AND METHODS

Using data from the Korea Acute Myocardial Infarction Registry from November 2005 to September 2008, a total of 8174 consecutive AMI patients were studied. Cox proportional hazard model revealed that higher baseline levels of hs-CRP was associated with 12-month all-cause mortality (p=0.045). To further understand this association, patients were divided into 3 groups based on their body mass index: 1) overweight/obese, 2) normal weight, and 3) underweight patients. Then each group was stratified into quartiles based on their hs-CRP.

RESULTS

In overweight/obese patients, Cox model showed significant association of hs-CRP with 12-month mortality when adjusted for age and gender (p<0.001), however, after adjustment with multiple covariates, mortality was highest in the 4th quartile {HR 2.382, (1.079-5.259), p=0.032} though statistically insignificant (p=0.172). We observed no significant association of serum hs-CRP with 12-month mortality in normal weight (p=0.681) and underweight (p=0.760) patients.

CONCLUSION

Higher baseline hs-CRP level (≥4.08 mg/dL) in overweight/obese AMI patients showed significant association with 12-month all-cause mortality independent of other prognostic markers.

Predicting the no-reflow phenomenon following successful percutaneous coronary intervention

In the setting of acute myocardial infarction, early and adequate reopening of an infarct-related artery is not necessarily followed by a complete restoration of myocardial perfusion. This condition is usually defined as ‘no-reflow’. The pathophysiology of no-reflow is multifactorial since extravascular compression, microvascular vasoconstriction, embolization during percutaneous coronary intervention, and platelet and neutrophil aggregates are involved. In the clinical arena, angiographic findings and easily available clinical parameters can predict the risk of no-reflow. More recently, several studies have demonstrated that biomarkers, especially those related to the pathogenetic components of no-reflow, could also have a prognostic role in the prediction and in the full understanding of the multiple mechanisms of this phenomenon. Thus, in this article, we investigate the role of several biomarkers on admission in predicting the occurrence of no-reflow following successful percutaneous coronary intervention.

Left ventricular function and C-reactive protein levels in acute myocardial infarction

To examine left ventricular (LV) function in patients after acute myocardial infarction (AMI) and assess its relation to C-reactive protein (CRP) as a measure of the early inflammatory response. We measured the CRP levels early after AMI and correlated them with the early structural and functional cardiac alterations. From November 2002 to December 2007, we prospectively enrolled community subjects who had experienced an AMI, as defined by standardized criteria, measured the CRP level, and obtained an echocardiogram. The study consisted of 514 patients (mean age 67 +/- 15 years, 59% men). CRP was measured early after symptom onset (median 6.1 hours; twenty-fifth to seventy-fifth percentile 2.2 to 11.1). The median CRP level was 4.8 mg/L (twenty-fifth to seventy-fifth percentile 1.8 to 24). The echocardiograms were obtained at a median of 1 day after AMI. The wall motion score index, LV ejection fraction, and LV diameter were similar across the CRP tertiles (all p >0.05). Greater CRP levels were associated with the presence of moderate or severe diastolic dysfunction (p = 0.002) and moderate or severe mitral regurgitation (p <0.001). The association with moderate or severe mitral regurgitation was independent of the clinical characteristics and ST-segment elevation status. In conclusion, at the initial phase of AMI, CRP elevation was associated with the presence and severity of mitral regurgitation and diastolic dysfunction. This suggests that inflammation is related to the ventricular remodeling processes, independently of LV systolic function.

Prognostic value of C-reactive protein and cardiac troponin I in primary percutaneous interventions for ST-elevation myocardial infarction

BACKGROUND

The rise in cardiac troponin I after ST-elevation myocardial infarction treated by primary percutaneous coronary interventions (PCIs) is predictive of infarct size and left ventricular ejection fraction (LVEF). However, the comparative value of C-reactive protein (CRP) and troponin I for infarct size evaluation and the respective relationships between these biomarkers and mortality have not been investigated.

METHODS

We studied 87 patients who underwent primary PCI for ST-elevation myocardial infarction. Concentrations of troponin I and CRP were measured before and for 72 hours after PCI. Infarct size was measured by the cumulative release of alpha-hydroxybutyrate deshydrogenase during the 72 hours after PCI (QHBDH72) and by delayed radionuclide LVEF (at 4.6 +/- 1.7 weeks).

RESULTS

Concentrations of CRP at peak and at 24, 48 and 72 hours, and of troponin I at 6 and 72 hours, correlated with QHBDH72 and LVEF. In single variable analysis, at a mean follow-up of 42 +/- 8 months, Killip score of 3 to 4, CRP at baseline and at 48 hours, and troponin I at 6 and 72 hours were related to mortality. By multiple variable analysis, Killip score (OR 9.9, CI 1.6-58.8) and troponin I at 72 hours (OR 9.43, CI 2.1-43.5) were the only independent predictors of mortality.

CONCLUSIONS

Plasma concentrations of CRP and troponin I after PCI were related to infarct size and mortality. However, Killip class and troponin I at 72 hours were the only independent predictors of mortality at long-term follow-up.

Baseline systemic inflammatory status and no-reflow phenomenon after percutaneous coronary angioplasty for acute myocardial infarction

BACKGROUND

Systemic inflammation is involved in several pathological cardiovascular processes. However, whether it plays a role in the no-reflow phenomenon occurring in patients with acute myocardial infarction (AMI) after percutaneous coronary intervention (PCI) is unknown.

METHODS

We studies 60 consecutive patients (59.5+/-12 years, 82% males) with a first ST-segment elevation AMI, treated by primary or rescue PCI within 6 h of symptom onset. Angiographic indexes of no-reflow, evaluated at the end of the procedure, included coronary TIMI flow grading, corrected TIMI frame count (c-TFC) and myocardial blush grade (MBG). ECG indexes of no-reflow included the lack of ST segment resolution (defined as a reduction <50% of the measured ST-segment elevation at 90 min, compared to the admission ECG), as analyzed both in the single lead with the maximal ST elevation and in all leads showing ST elevation on admission. Patients were divided into two groups according to baseline high-sensitivity C-reactive protein (CRP) serum levels measured on admission: high CRP group (CRP>5 mg/L) and low CRP group (CRP<5 mg/L).

RESULTS

A similar prevalence of final TIMI flow<3 and MBG<3 was observed in patients with high and low CRP serum levels (30% vs. 12%, p=0.1, and 50% vs. 53%, p=1.0, respectively), and c-TFC was also similar in the two groups (26+/-4.5 vs. 24+/-6, p=0.5). Accordingly, the prevalence of lack of ST-segment resolution in the two groups was similar, both by the single-lead method (25% vs. 25%, p=1.0) and the multiple-lead method (29% vs. 19%, p=0.4).

CONCLUSION

In this study we failed to demonstrate any significant association between CRP serum levels on admission and coronary no-reflow, as assessed by both angiographic and ECG parameters in AMI patients treated by successful primary or rescue PCI within 6 h of chest pain onset.

Association of C-reactive protein and myocardial perfusion in patients with ST-elevation acute myocardial infarction

This study sought to evaluate the relation between C-reactive protein (CRP) on admission of patients with acute myocardial infarction (AMI) and myocardial perfusion as defined by postintervention angiographic myocardial blush grade (MBG) and their impact on subsequent mortality. The patient population comprised 191 consecutive patients with AMI undergoing PTCA within 12h of symptom onset on a native vessel. Patients were divided based on the CRP level on admission (Rolf Greiner BioChemica, Germany, cutpoint for the assay CRP: 5mg/l) into a group with elevated CRP (>or=5mg/l) and a group with normal CRP. Angiographic myocardial blush grade (MBG) after revascularization of the infarct-related artery was determined to evaluate myocardial reperfusion. Revascularization of the infarct-related artery was successful in 176 (92.6%) patients. The frequency of impaired perfusion (MBG 0-2) was higher in the elevated CRP group than in the normal CRP group (74.5% versus 59.7%, respectively, p=0.046). Elevated CRP on admission was an independent predictor of impaired myocardial perfusion (MBG 0-2, OR 1.92, 95% CI 1.02-4.01, p=0.042) in addition to age >70 years. Elevated CRP (OR 2.64, 95% CI 1.26-5.53, p=0.009) and MBG 0-2 (OR 4.58; 95% 1.73-12.20, p=0.002) were independent predictors of mortality during a 22.4+/-15.3 months follow-up in addition to heart rate on admission >100 beats/min (OR 3.07; 95% CI 1.30-7.25, p=0.009). In sequential Cox models, the predictive power of clinical data and MBG for mortality (model chi-squared 18.3) was strengthened by the inclusion of CRP levels (model chi-squared 24.3). In conclusion, there is a relation between elevated admission CRP and impaired reperfusion in the myocardium subtended to the infarct-related artery. The combination of clinical data, myocardial reperfusion levels after primary angioplasty for AMI and admission CRP increases the predictive value for subsequent survival.

Usefulness of high-sensitivity IL-6 measurement for clinical characterization of patients with coronary artery disease

Interleukin 6 (IL-6) may represent an early marker of inflammatory activation and may be useful to ameliorate risk stratification in patients with ischemic heart disease. The aim of this study was to verify the performance characteristics of an ultrasensitive immunoassay (Biosource International, Camarillo, CA) for high-sensitivity (hs)-IL-6 measurement in comparison with hs-R&D Systems (Abingdon, United Kingdom) and Immulite System (Diagnostic Products Corporation [DPC], Los Angeles, CA) methods in patients with ischemic heart disease. In addition, hs-C-reactive protein (hs-CRP) concentrations were measured, to evaluate the correlation with hs-IL-6 levels. We measured IL-6 and CRP serum levels in 39 patients with ischemic heart disease and in 12 controls. Out of the 39 patients studied, 13 were affected by unstable angina, 13 by post-acute myocardial infarction (AMI) unstable angina, and 13 by stable angina. The imprecision profile and functional sensitivity were performed measuring 9 different serum pools in 10 runs. The Biosource method had the best performance characteristics as compared to the others. Mean IL-6 level was higher in patients with unstable and post-AMI unstable angina with respect to controls. CRP levels were elevated in patients with post-AMI. In the whole population a high significant linear regression was observed between Biosource hs-IL-6 and hs-CRP serum levels. The Biosource method for IL-6 measurement is characterized by a high functional sensitivity that allows a better stratification of patients with ischemic heart disease.

Body Temperature – A Marker of Infarct Size in the Era of Early Reperfusion

We measured body temperature in 40 consecutive patients treated for a first ST elevation acute myocardial infarction (AMI) with primary percutaneous coronary interventions. Left ventricular function was assessed by echocardiography, and blood samples were drawn for highly sensitive C-reactive protein (hs-CRP), white blood cell (WBC) count, fibrinogen, creatine kinase (CK), and cardiac troponin I levels (cTnI). The median (25th, 75th quartiles) peak 24-hour temperature was 37.4 degrees C (36.9 degrees C, 37.6 degrees C). Variables significantly associated with peak 24-hour temperature were CK (p = 0.01, r = 0.42), wall motion index (p = 0.01, r = 0.41), hs-CRP (p = 0.01, r = 0.41), and cTnI (p = 0.03, r = 0.35). There was no significant correlation between peak 24-hour temperature and WBC count (p = 0.39, r = 0.14) and fibrinogen (p = 0.12, r = 0.21). Thus, peak 24-hour body temperature after ST elevation AMI probably reflects infarct size rather than a nonspecific inflammatory response.

White Blood Cell Count and C-reactive Protein Predict Short-term Prognosis in Acute Myocardial Infarction

An elevated white blood cell (WBC) count and C-reactive protein (CRP) concentration are associated with acute myocardial infarction (AMI) and long-term mortality in patients with coronary artery disease. Their relationship with short-term prognosis following AMI is less clear, however. We investigated the relationship between WBC count and CRP concentration, obtained at the time of admission, and the development of subsequent ischaemic coronary events (SICE) within 30 days of AMI in 177 patients. After adjustment for confounding factors, CRP concentration was found to be a strong independent predictor for SICE within 30 days in patients with AMI. WBC count was not found to be an independent predictor, but there was a strong correlation between high WBC counts and the onset of SICE within 30 days in patients with AMI. We conclude that CRP concentration and WBC count could be used to predict the short-term prognosis of patients with AMI.

Admission C-reactive protein levels and 30-day mortality in patients with acute myocardial infarction

BACKGROUND

Elevated C-reactive protein levels are associated with an increased risk of subsequent cardiovascular events in patients with unstable angina. However, limited information is available concerning the value of C-reactive protein levels in patients with acute myocardial infarction.

METHODS

We prospectively studied 448 consecutive patients (mean [+/- SD] age, 60 +/- 12 years) with acute myocardial infarction. Serum C-reactive protein levels were measured within 12 to 24 hours of symptom onset, and divided into tertiles. Infarct size was determined by echocardiographic examination that was performed on day 2 or 3. Patients were followed for 30 days for mortality and subsequent cardiac events.

RESULTS

At 30 days, 4 deaths (3%) occurred in patients in the lowest C-reactive protein tertile, 15 (10%) in patients in the middle tertile (P = 0.02 vs. the lowest tertile), and 33 (22%) in patients in the highest tertile (P <0.001 vs. the lowest tertile). In a multivariate analysis, C-reactive protein in the upper tertile was associated with 30-day mortality (relative risk = 3.0; 95% confidence interval [CI]: 1.3 to 7.2; P = 0.01) and the development of heart failure (odds ratio = 2.6; 95% CI: 1.5 to 4.6; P = 0.0006). C-reactive protein levels were not associated with the development of postinfarction angina, recurrent myocardial infarction, or the need for revascularization.

CONCLUSION

Plasma C-reactive protein level obtained within 12 to 24 hours of symptom onset is an independent marker of 30-day mortality and the development of heart failure in patients with acute myocardial infarction. These findings suggest that C-reactive protein levels may be related to inflammatory processes associated with infarct expansion and postinfarction ventricular remodeling.

Thrombolytic therapy reduces red blood cell aggregation in plasma without affecting intrinsic aggregability

Red blood cell (RBC) aggregation may contribute to occlusion of the coronary microcirculation during myocardial infarction. We studied the effect of thrombolytic therapy on RBC aggregation in patients with acute myocardial infarction (AMI). Compared with patients with myocardial infarction who did not receive thrombolytic therapy, those treated with systemic thrombolysis exhibited significantly reduced RBC aggregation, reduced plasma fibrinogen levels and increased plasma D-dimer levels. Using measurement of RBC aggregation in a standardized dextran-500 solution, reduction in RBC aggregation after thrombolysis was shown to be plasma dependent. Thrombolytic therapy had no direct effect on intrinsic RBC aggregability in patients with AMI. We conclude that thrombolytic therapy has rheologic consequences that may contribute to its overall efficacy. Inhibition of RBC aggregation by thrombolytic therapy may result from the degradation of fibrinogen, a key factor in the formation of RBC aggregates, and from the generation of fibrinogen degradation products capable of disaggregating RBCs.