Fractional flow reserve and non-hyperemic indices:Essential tools for percutaneous coronary interventions

Hemodynamical evaluation of a coronary artery lesion is an important diagnostic step to assess its functional impact.Fractional flow reserve(FFR)received a class IA recommendation from the European Society of Cardiology for the assessment of angiographically moderate stenosis.FFR evaluation of coronary artery disease offers improvement of the therapeutic strategy,deferring unnecessary procedures for lesions with a FFR>0.8,improving patients'management and clinical outcome.Post intervention,an optimal FFR>0.9 post stenting should be reached and>0.8 post drug eluting balloons.Non-hyperemic pressure ratio measurements have been validated in previous studies with a common threshold of 0.89.They might overestimate the hemodynamic significance of some lesions but remain useful whenever hyperemic agents are contraindicated.FFR remains the gold standard reference for invasive assessment of ischemia.We illustrate this review with two cases introducing the possibility to estimate also non-invasively FFR from reconstructed 3-D angiograms by quantitative flow ratio.We conclude introducing a hybrid approach to intermediate lesions(DFR 0.85-0.95)potentially maximizing clinical decision from all measurements.

Fractional flow reserve measured via left internal mammary artery after coronary artery bypass grafting:Two case reports

BACKGROUND The fractional flow reserve(FFR)has made the treatment of coronary heart disease more precise.However,there are few reports on the measurement of FFR via the left internal mammary artery(LIMA).Herein,we described the determination of further treatments by measuring FFR via the LIMA in 2 cases after coronary artery bypass grafting(CABG).CASE SUMMARY Case 1 was a 66-year-old male who was admitted due to“chest tightness after CABG.”The patient underwent CABG 7 years prior due to coronary heart disease.Coronary artery angiography showed complete occlusion of the left anterior descending artery(LAD),and subtotal occlusion of the third segment of the right coronary artery.On arterial angiography,there was 85%stenosis at the distal end of the anastomosis of the LIMA-LAD graft.FFR via LIMA was determined at 0.75.Thus,balloon dilation was performed in Case 1.FFR after balloon dilation was 0.94.Case 2 was a 60-year-old male who was admitted due to“chest tightness after CABG.”The patient underwent CABG 6 years prior due to coronary heart disease.There was 60%segmental stenosis in the middle segment of LAD and 75%anastomotic stenosis.FFR measured via LIMA was 0.83(negative);thus the intervention was not performed.Case 2 was given drug treatments.At the 3-mo follow-up,there was no recurrence of chest tightness or shortness of breath in both cases.They are currently under continual follow-up.CONCLUSION We provided evidence that FFR measurement via grafted blood vessels,especially LIMA,after CABG is a good method to determine the intervention course.

Assessment of Coronary Flow Velocity Reserve by Noninvasive Transthoracic Doppler Echocardiography in Patients with Angiographically Normal Coronary Arteries

Summary： The measurement of coronary flow velocity reserve （CFVR） by transthoracic Doppler echocardiography （TTDE） with invasive intracoronary Doppler flow wire technique （ICD） was validated and the pathological factors which influence CFVR in patients with angiographically normal coronary arteries were analyzed. CFVR was determined successfully in left anterior descending artery （LAD） in 37 of 40 patients with angiographically normal coronary arteries （men 22, women 15, age 20-75 years, mean age 54±12 years）. Coronary flow velocity was measured in the distal LAD by TTDE with contrast enhancement at baseline and during intravenous adenosine infusion of 110 μg/ kg per min within 48 h after ICD technique. Average peak velocity at baseline （APVb）, average peak velocity during hyperemia （APVh） and CFVR determined from TTDE were correlated closely with those from ICD measurements （APVb： y= 0. 64x＋ 5. 04, r=0. 86, P〈0. 001; APVh： y=0. 63x＋14. 36, r=0.82, P〈0.001; CFVR： y=0.65xq-0.92, r=0.88, P〈0.001）. For CFVR measurements, the mean differences between TTDE and ICD methods were 0. 12±0.39. CFVR in patients with history of hypertension was significantly lower than that in patients without history of hypertension （P〈0.05）. Intravascular ultrasound （IVUS） was performed in 34 patients. Plaque formation was found in LAD by IVUS in 17 （50%） patients. No significant difference in CFVR was found between the patients without plaque formation （3. 11±0. 49） and those with plaque formation （2. 76±0.53, P=0. 056）. It is suggested that TTDE with contrast enhancement provides reliable measurement of APV and CFVR in the distal I.AD. The early stage of atherosclerosis could be detected by IVUS, which may be normal in angiography. CFVR is impaired in patients with history of hypertension compared with that in patients without history of hypertension.

Effect of bivalirudin on myocardial microcirculation and adverse events after interventional therapy in older patients with acute coronary syndrome

BACKGROUND Bivalirudin,a direct thrombin inhibitor,is used in anticoagulation therapies as a substitute for heparin,especially during cardiovascular procedures such as percutaneous coronary intervention.AIM To explore the effect of bivalirudin on myocardial microcirculation following an intervention and its influence on adverse cardiac events in elderly patients with acute coronary syndrome(ACS).METHODS In total,165 patients diagnosed with acute myocardial at our hospital between June 2020 and June 2022 were enrolled in this study.From June 2020 to June 2022,elderly patients with ACS with complete data were selected and treated with interventional therapy.The study cohort was randomly divided into a study group(n=80,administered bivalirudin)and a control group(n=85,administered unfractionated heparin).Over a 6-mo follow-up period,differences in emergency processing times,including coronary intervention,cardiac function indicators,occurrence of cardiovascular events,and recurrence rates,were analyzed.RESULTS Significant differences were observed between the study cohorts,with the observation group showing shorter emergency process times across all stages:Emergency classification;diagnostic testing;implementation of coronary intervention;and conclusion of emergency treatment(P<0.05).Furthermore,the left ventricular ejection fraction in the observation group was significantly higher(P<0.05),and the creatine kinase-MB and New York Heart Association scores were CONCLUSION In elderly patients receiving interventional therapy for ACS,bivalirudin administration led to increased activated clotting time achievement rates,enhanced myocardial reperfusion,and reduced incidence of bleeding complications and adverse cardiac events.

Usefulness of Fractional Flow Reserve during Routine Clinical Procedures in All-Comer Coronary Artery Disease Patients

Background: Fractional flow reserve (FFR)-guided interventions, though proved to be safe, continue to be a much-underutilized modality in determining treatment strategy, and data is lacking in Indian population. Objective: We aimed to determine the use of FFR-guided PCI and assess the overall impact on treatment decisions and clinical outcomes in patients with acute coronary syndrome (ACS) or chronic coronary syndromes (CCS). Methods: In this single-center retrospective and prospective observational study, FFR had been performed for the evaluation of treatment reclassification and clinical outcomes, as per physician’s clinical practice. Results: Data was obtained for 250 subjects (mean age 60.45 ± 9.6 years) with 324 lesions. The treatment plan based on angiography alone changed in 28% of lesions post-hyperemic FFR. The initial treatment plan based on angiography vs. the final treatment plan post-FFR (>0.80) was medical management 56.5% vs. 66.0%;CABG 11.1% vs. 7.7%;and PCI 32.4% vs. 26.2%. In subjects initially assigned to medical management, 14% had changed to PCI, and for subjects initially assigned to PCI, 44% had changed to medical therapy. Receiver operating characteristics (ROC) curve analysis revealed a good correlation between a resting FFR value of <0.87 and hyperemic FFR value of <0.80. The rate of 2-year major adverse cardiovascular events (MACE) was 0.9%. Conclusion: This study supports the use of FFR in determining treatment strategy in ACS or CCS patients with low MACE. Resting FFR value of <0.87 may be an alternative to intracoronary nitroglycerine/adenosine/Nikorandil-induced FFR in predicting positive FFR particularly in hemodynamically unstable patients, and who are intolerant to hyperemic drugs.

Association of arterial stiffness with coronary flow reserve in revascularized coronary artery disease patients

AIM: To investigate the association of arterial wave reflection with coronary flow reserve(CFR) in coronary artery disease(CAD) patients after successful revascularization.METHODS: We assessed 70 patients with angiographically documented CAD who had undergone recent successful revascularization. We measured(1) reactive hyperemia index(RHI) using fingertip peripheral arterial tonometry(RH-PAT Endo-PAT);(2) carotid to femoral pulse wave velocity(PWVc-Complior);(3) augmentation index(AIx), the diastolic area(DAI%) and diastolic reflection area(DRA) of the central aortic pulse wave(Arteriograph);(4) CFR using Doppler echocardiography; and(5) blood levels of lipoprotein-phospholipase A2(LpPLA2).RESULTS: After adjustment for age, sex, blood pressure parameter, lipidemic, diabetic and smoking status, we found that coronary flow reserve was independently related to AIx(b =-0.38, r = 0.009), DAI(b = 0.36, P = 0.014), DRA(b = 0.39, P = 0.005) and RT(b =-0.29,P = 0.026). Additionally, patients with CFR < 2.5 had higher PWVc(11.6 ± 2.3 vs 10.2 ± 1.4 m/s, P = 0.019), SBPc(139.1 ± 17.8 vs 125.2 ± 19.1 mm Hg, P = 0.026), AIx(38.2% ± 14.8% vs 29.4% ± 15.1%, P = 0.011) and lower RHI(1.26 ± 0.28 vs 1.50 ± 0.46, P = 0.012), DAI(44.3% ± 7.9% vs 53.9% ± 6.7%, P = 0.008), DRA(42.2 ± 9.6 vs 51.6 ± 11.4, P = 0.012) and Lp PLA2(268.1 ± 91.9 vs 199.5 ± 78.4 ng/m L, P = 0.002) compared with those with CFR ≥ 2.5. Elevated Lp PLA2 was related with reduced CFR(r =-0.33, P = 0.001), RHI(r =-0.37, P < 0.001) and DRA(r =-0.35, P = 0.001) as well as increased PWVc(r = 0.34, P = 0.012) and AIx(r = 0.34, P = 0.001). CONCLUSION: Abnormal arterial wave reflections are related with impaired coronary flow reserve despite successful revascularization in CAD patients. There is a common inflammatory link between impaired aortic wall properties, endothelial dysfunction and coronary flow impairment in CAD.

Long-term outcomes after fractional flow reserve-guided percutaneous coronary intervention in patients with severe coronary stenosis

Objective To explore the safety and efficacy of FFR-guided percutaneous coronary intervention (PCI) in vessels with severe diameter stenosis. Methods & Results Of 1090 patients undergoing fractional flow reserve (FFR) assessment from 2002 to 2009,we identified 167 patients in whom FFR was measured in at least one 70%–89% stenotic lesion. These patients were subdivided into an FFR-defer group (n = 49) if PCI was deferred (FFR > 0.80),and an FFR-perform group (n = 118) if PCI was performed (FFR ≤ 0.80). Comparatively,an additional 1176 patients undergoing PCI in at least one lesion with 70%–89% stenosis but without measurement of FFR served as a control (angiography- guided) group. Clinical outcomes were compared during a median follow-up of 49.0 months. The 5-year Kaplan-Meier estimated revascularization rates were 16% in the FFR-defer group and 33% in the FFR-perform group (P = 0.046). The incidence of major adverse cardiac events were comparable in these two groups (HR = 0.82,95% CI: 0.37–1.82,P = 0.63). The number of stents placed was significantly lower in the FFR-guided group (0.9 ± 0.8 vs. 1.4 ± 0.8,P < 0.001). Conclusions Functional revascularization for lesions with visually severe stenosis is clinically safe and associated with fewer stents use. This study suggests that extending the use of FFR to more severe coronary lesions may be reasonable.

IN PATIENTS WITH HYPERTENSIVE LEFT VENTRICULAR HYPERTROPHY AND CORONARY HEART DISEASE,CORONARY FLOW RESERVE IS SIMILARLY IMPAIRED

Coronary blood flow reserve (CFR) was assessed by transesophageal Doppler echocardiography in normal subjects (group A. n=20),hypertensive non-left ventricular hypertrophy (non-LVH)Patients (group B,n=22). hypertensive patients with LVH(group C.n=32)and coronary heart disease patients (group D. n=33) with the volume sample placed at the bifurcation of the left main and left main and left descending coronary artery. Coronary blood flow velocity (CBFV)was evaluated at rest.2 minutes after dipyridamole (0. 56mg/kg. i. v.) . and 2 minutes after aminophylline i.v. The ratio of dipyridamole to rest maximal diastolic velocity (D/R PDV) was considered the index of coronary blood flow reserve.It was found that D/R PDV was significantly less in groups C and D compared with that in groups A and B (D PDC,1.84±0. 57. 1. 57±0. 41 versus 2.59±0.70 and 2.22+0.58,respectively),with no difference in D/R PDV between groups C and D.Twenty-four out of 32 patients in group C with D/R PDV were less than 2.0 compared to 29 out of 33 patients in group D (P>0.05).Significant negative correlation was found between D/R PDV. D/R PSV and interseptal thickness. left ventricular mass index in hypertensive patients.These data show that impaired CFR in hypertensive patients with LVH is comparable to that in patients with coronary heart disease.

Quantitative Assessment of Coronary Flow Reserve by the Variables of Time-Intensity Curve with Myocardial Contrast Echocardiography

The reliability and reliable indexes of q ua ntitative assessment of coronary flow reserve (CFR) by using time intensity cur ve (TIC) via myocardial contrast echocardiography were investigated. The TIC var iables were obtained by employing acoustic densitometry (AD) technique before an d after acetylcholine (Ach) injection in 12 dogs. Meanwhile, the correlation be tween these variables and CFR was analyzed. Among the variables derived from TIC , peak intensity (PI), area under the curve (AUC) and descending slope (DS) were increased significantly ( P <0.05) with the increase of coronary blood flow a fter Ach injection. Conversely, time to peak (TP), half time of descent (HT) , and mean transit time (MTT) were decreased remarkably ( P <0.0001). Th e P I and AUC ratios from post to pre Ach injection were strongly associated with CFR with the correlation coefficient (r) being 0.8366 and 0.8824, respectively. It is reliable by using the variables derived from TIC with myocardial contrast echocardiography to quantitatively evaluate regional myocardial CFR. The PI an d AUC ratios from post to pre Ach injection are the reliable indexes for quan titative assessment of CFR.

A Fast-Fractional Flow Reserve Simulation Method in A Patient with Coronary Stenosis Based on Resistance Boundary Conditions

Fractional flow reserve(FFR)is the gold standard to identify individual stenosis causing myocardial ischemia in catheter laboratory.The purpose of this study is to present a fast simulation method to estimate FFR value of a coronary artery,which can evaluate the performance of vascular stenosis,based on resistance boundary conditions.A patient-specific 3-dimensional(3D)model of the left coronary system with intermediate diameter stenosis was reconstructed based on the CTA images.The resistance boundary conditions used to simulate the coronary microcirculation were computed based on anatomical reconstruction of coronary 3D model.This study was performed by coupling the 3D coronary tree model with the lumped parameter model(0D model).The flow rate and pressure of coronary tree were calculated in twenty minutes.In addition,the effect of inlet pressure and myocardial mass on FFRss values has been investigated.The results showed that the effect of myocardial mass was greater than the effect of inlet pressure on FFRss.This FFRss simulation method can quickly and accurately assess the influence of coronary stenosis in aid clinical diagnosis.

ABNORMAL CORONARY FLOW RESERVE IN PATIENTS WITH LEET VENTRICULAR HYPERTROPHY DUE TO HYPERTENSION

Obiective To measure coronary flow reserve (CFR) with angiography and computer-ass assisted technique in patients with left ventricular hypertrophy due to hypertension. Methods Coronary arterialdiameter, cross - sectional area and blood velocity of coronary flow in left anterior descending artery (LAD) andright coronary artery (RCA) were calculated with a computer in serial images of coronary angiography. Coronaryflow reserve was then measured in 22 patients with left ventricular hypertrophy due to hypertension (hypertropygroup) and 26 normal subjects (control group). Results Blood velocity and flow of both coronary arteries weresignificantly higher in hypertrophy group (LAD: n=22, RCA: n=14) than in control group (LAD: n=26, RCA:n=20) before intracoronary papaverine. However, blood velocity and flow of both coronary arteries were increasedsimilarly in both groups after intracoronary papaverine. Coronary flow reserve in hypertrophy group (LAD:CFR=2.2± 1.0, RCA： CFR= 2.9± 0.8) was significantly lower than in control group (LAD: CFR= 3.9± 2.1, RCA:CFR=5.5±2.0, all P<0.01). Conclusion The study indicates that coronary flow reserve is reduced in patientswith left ventricular hypertrophy due to hypertension which may be related to a higher coronary flow at restingstate.

Fractional Flow Reserve Measurement by Coronary Computed Tomography Angiography:A Review with Future Directions

Invasive fractional fl ow reserve(FFR)measurement is currently the gold standard for coronary intervention.FFR measurement by coronary computed tomography angiography(FFRCT)is a novel and promising imaging technology that permits noninvasive assessment of physiologically signifi cant coronary lesions.FFRCT is capable of combining the anatomic information provided by coronary computed tomography angiography with computational fl uid dynamics to compute FFR.To date,several studies have reported the diagnostic performance of FFRCT compared with invasive FFR measurement as the reference standard.Further studies are now being implemented to determine the clinical feasibility and economic implications of FFRCT techniques.This article provides an overview and discusses the available evidence as well as potential future directions of FFRCT.

Non-invasive Assessment of Coronary Flow Velocity Reserve: A New Method Using Transthoracic Doppler Echocardiography

Summary: Transthoracic Doppler echocardiography (TTDE) allows noninvasive flow measurement in the distal left anterior descending artery (LAD). The feasibility of detecting coronary flow by contrast-enhanced TTDE with second harmonic technique was assessed, the coronary flow velocity reserve (CFVR) was evaluated in comparison to intracoronary Doppler flow (ICD) analysis and the CFVR after PTCA in LAD was investigated. In 77 (96 %) of 80 patients, CFVR was successfully determined with intravenous adenosine infusion. Doppler signal quality was evaluated in the first 46 patients by use of intravenous Levovist infusion and second harmonic technique. The Doppler flow was not visible in 1 patient only. CFVR determined from TTDE (2.77±0.65) was correlated closely with those from ICD (2.88±0.78) measurements (y=0.73x+0.67, r=0.87, P<0.001). In conclusion, TTDE is a feasible method and provides reliable data on CFVR which can be used for follow-up after PTCA.

Fractional Flow Reserve-guided Percutaneous Coronary Intervention:Standing the Test of Time

Percutaneous coronary intervention(PCI)improves symptoms and prognosis in ischemia-inducing,functionally signifi cant,coronary lesions.Use of fractional flow reserve allows physicians to investigate the ischemia-inducing potential of a specifi c lesion and can be used to guide coronary revascularization,especially in multivessel coronary artery disease.Fractional flow reserve-guided PCI has been extensively investigated.Results show that deferral of stenting in non-signifi cant lesions is safe,whereas deferral of stenting in functionally signifi cant lesions worsens outcome.FFR-guided PCI improves outcome in multivessel disease over angiography-guided PCI.Until recently,there was little known about the long-term outcome of FFR-guided revascularization and its validity in acute coronary syndromes.This review aims to address the new evidence regarding long-term appropriateness of FFR-guided PCI,the need for hyperemia to evaluate functional severity,and the use of FFR in acute coronary syndromes.

ASSESSMENT OF CORONARY FLOW RESERVE IN PATIENTS WITH ANGINA PECTORIS

Coronary flow reserve was assessed by a computer-assisted method after intracoronary injection of papaverine in patients with angina pectoris. Compared with control group (n=26), patients with coronary artery disease (n=45) had decreased proximal diameter, cross-sectional area, blood velocity, flow and flow reserve of the left anterior descending and right coronary arteries. The blood velocity, flow and flow reserve of these two coronary arteries were lower in patients with syndrome X (n=16), but proximal diameter and cross-sectional area were similar. The study indicates that coronary flow reserve is reduced in patients with coronary artery disearse and syndrome X,which may be related to abnormal changes at different levels of the coronary vasculature.

Usefulness of coronary flow reserve measured by transthoracic coronary Doppler ultrasound in the elderly

The left anterior descending （LAD） coronary artery is the main vessel of human coronary circulation, and life-threa- tening consequences are seen when flow in this area is im- paired, Noninvasive measurement of coronary flow re- serve （CFR）, defined as the ratio of maximal to baseline coronary blood flow, has been repeatedly shown to be a feasible technique by ultrasound transthoracic Doppler （TTD） both in the LAD and, with some limitations, in the posterior descending （PD） coronary artery.

Comparison of Fractional Flow Reserve-Guided Revascularization Strategies in Isolated Proximal Left Anterior Descending Coronary Artery Disease

The data about FFR-guided revascularization in isolated proximal LAD disease are limited and studies comparing long-term outcomes of FFR-guided PCI versus FFR-guided CABG in single-vessel proximal LAD disease are lacking. We aimed to assess the 4-year long-term safety and effectiveness of fractional flow reserve (FFR)-guided percutaneous coronary intervention (PCI) and FFR-guided coronary artery bypass graft surgery (CABG) for the treatment of proximal left anterior descending (LAD) lesions. The study included 129 patients with functionally significant (FFR ≤ 0.80) isolated proximal LAD stenosis (PCI, 88 patients vs. CABG, 41). Clinical endpoints were assessed by Kaplan-Meier method and compared by the log-rank test. At a mean follow-up time of 47 ± 12 months, a higher incidence of myocardial infarction in the PCI group (PCI: 32% vs. CABG: 15%;p = 0.003) and a higher incidence of stroke in the CABG group (CABG: 3 (7%) vs. PCI 0 (0%);p = 0.031) were observed. However, there were no significant differences in the primary composite endpoint, death and target vessel revascularization between PCI and CABG groups. The PCI and CABG in isolated proximal LAD lesions yielded similar long-term outcomes regarding the primary composite clinical endpoints. However, stroke was more frequent in the CABG group than in the PCI group.

Quantitative flow ratio and intravascular ultrasound guided percutaneous coronary intervention of left anterior descending lesion concomitant with severe coronary myocardial bridge

Severe coronary stenosis concomitant with congenital coronary myocardial bridge(MB)is a tough scenario for cardiologist to perform revascularization,for which the complication rates including in-stent restenosis,stent fracture,stent thrombosis and even coronary perforation are still high.[1,2]Meanwhile,the necessity of revascularization in such patients is worth prudent evaluation.Cardiac imaging modalities are crucial and helpful in making revascularized decisions and strategies.Herein,we report a case using quantitative flow ratio(QFR)and intravascular ultrasound(IVUS)to facilitate accurate revascularization in a patient with both severe coronary stenosis and deep coronary MB.

RELATIONS OF ENDOTHELIAL FUNCTION AND BLOOD FLOW IN BRACHIAL ARTERY AND CORONARY ARTERY

Objective:To determine the relations between endothelium-dependent vasodilator function and blood flow in the brachial and coronary arteries in patients with suspected coronary artery disease.Methods:Twenty-eight patients with suspected coronary artery disease underwent brachial artery endothelial function test by using high-resolution B-mode ultrasound before coronary angiography(CAG)and coronary flow reserve(CFR)test by using intracoronary Doppler technique.The correlation of coronary artery dilatation induced by an increase in blood flow after intracoronary adenosine infusion and brachial artery flow-mediated dilatation(FMD) following reactive hyperemia was evaluated.The relation between the change of brachial artery blood flow and CFR was also studied.Results:There was a positive correlation between brachial FMD and percent change of coronary diameter after adenosine infusion(12.50%±9.35% vs 11.38%±7.55%,r=0.425,P=0.02).There was also a weak negative relation between brachial flow change following reactive hy-peremia and CFR(r=-0.397,P=0.04).Conclusion:There is a correlation between the coronary endo-thelial function and the CFR by ultrasonic determination of brachial flow changes following reactive hyperemia.

Correlation between intracoronary thrombus components and coronary blood flow after percutaneous coronary intervention for acute myocardial infarction at different onset time

BACKGROUND Acute myocardial infarction(AMI)is a leading cause of mortality.Early reperfusion to restore blood flow is crucial to successful treatment.In the current reperfusion regimen,an increasing number of patients have benefited from direct percutaneous coronary intervention(PCI).In order to understand whether there is a correlation between the components of coronary thrombosis and the absence of reflow or slow blood flow after coronary stent implantation in direct PCI,we collected data on direct PCI cases in our hospital between January 2016 and November 2018.AIM To investigate the correlation between intracoronary thrombus components and coronary blood flow after stent implantation in direct PCI in AMI.METHODS We enrolled 154 patients(85 male and 69 female,aged 36–81 years)with direct PCI who underwent thrombus catheter aspiration within<3,3–6 or 6–12 h of onset of AMI between January 2016 and November 2018.The thrombus was removed for pathological examination under a microscope.The patients of the three groups according to the onset time of AMI were further divided into those with a white or red thrombus.The thrombolysis in myocardial infarction(TIMI)blood flow after stent implantation was recorded based on digital subtraction angiography during PCI.The number of patients with no-reflow and slow blood flow in each group was counted.Statistical analysis was performed based on data such as onset time,TIMI blood flow.RESULTS There were significant differences in thrombus components between the patients with acute ST-segment elevation myocardial infarction and non-ST-segment elevation myocardial infarction(P<0.01).In the group with PCI<3 h after onset of AMI,there was no significant difference in the incidence of no-reflow and slow-flow between the white and red thrombus groups.In the groups with PCI 3-6 and 6-12 h after onset of AMI,there was a significant difference in the incidence of no-reflow and slow-flow between the white and red thrombus groups(P<0.01).There was a significant correlation between the onset time of AMI and the occurrences of no-reflow and slow blood flow during PCI(P<0.01).CONCLUSION In direct PCI,the onset time of AMI and color of coronary thrombus are often used to predict whether there will be no reflow or slow blood flow after stent implantation.