Antioxidative Triplet Excitation Energy Transfer in Bacterial Reaction Center Using a Screened Range Separated Hybrid Functional.

Excess energy absorbed by photosystems (PSs) can result in photoinduced oxidative damage. Transfer of such energy within the core pigments of the reaction center in the form of triplet excitation is important in regulating and preserving the functionality of PSs. In the bacterial reaction center (BRC), the special pair (P) is understood to act as the electron donor in a photoinduced charge transfer process, triggering the charge separation process through the photoactive branch A pigments that experience a higher polarizing environment. At this work, triplet excitation energy transfer (TEET) in BRC is studied using a computational perspective to gain insights into the roles of the dielectric environment and interpigment orientations. We find in agreement with experimental observations that TEET proceeds through branch B. The TEET process toward branch B pigment is found to be significantly faster than the hypothetical process proceeding through branch A pigments with ps and ms time scales, respectively. Our calculations find that conformational differences play a major role in this branch asymmetry in TEET, where the dielectric environment asymmetry plays only a secondary role in directing the TEET to proceed through branch B. We also address TEET processes asserting the role of carotenoid as the final triplet energy acceptor and in a mutant form, where the branch pigments adjacent to P are replaced by bacteriopheophytins. The necessary electronic excitation energies and electronic state couplings are calculated by the recently developed polarization-consistent framework combining a screened range-separated hybrid functional and a polarizable continuum mode. The polarization-consistent potential energy surfaces are used to parametrize the quantum mechanical approach, implementing Fermi's golden rule expression of the TEET rate calculations.

Role of Dielectric Screening in Calculating Excited States of Solvated Azobenzene: A Benchmark Study Comparing Quantum Embedding and Polarizable Continuum Model for Representing the Solvent.

The low energy excited states of the conformational isomers of solvated azobenzene are calculated with several DFT methods accounting for the solute-solvent interaction implicitly with the polarizable continuum model or explicitly with subsystem DFT. For the latter, embedding potentials are calculated for 21 sampled snapshots of the solvent molecules. First, we find that accounting for the solvent implicitly or explicitly has little effect on the predicted cis-trans S1 excitation energy gap. Second, we find that azobenzene's S1 cis and trans energies are accurate as long as a screened range-separated hybrid exchange-correlation functional is employed. Finally, we also tested a simplified workflow whereby a single, averaged, embedding potential is used. Unfortunately, we find larger deviations against the experiment for the simplified workflow. This highlights a basic flaw in the approach, where the time scale of solvent averaging is much longer than that of the solute's electronic polarization.

Electronic Spectra of C60 Films Using Screened Range Separated Hybrid Functionals.

We study computationally the electronic spectra of C60 thin films using the recently developed density functional theory (DFT) framework combining a screened range separated hybrid (SRSH) functional with a polarizable continuum model (PCM). The SRSH-PCM approach achieves excellent correspondence between the frontier orbital's energy levels and the ionization potential and electron affinity of the molecular system at the condensed phase and consequently leads to high quality electronic excitation energies when used in time-dependent DFT calculations. Our calculated excited states reproduce the experimentally main reported spectral peaks at the 3.6-4.6 eV energy range and when addressing excitonic effects also reproduce the red-shifted spectral feature. Notably, we analyze the low-lying peak at 2.7 eV and associate it to an excitonic state.

CTRAMER: An open-source software package for correlating interfacial charge transfer rate constants with donor/acceptor geometries in organic photovoltaic materials.

In this paper, we present CTRAMER (Charge-Transfer RAtes from Molecular dynamics, Electronic structure, and Rate theory)-an open-source software package for calculating interfacial charge-transfer (CT) rate constants in organic photovoltaic (OPV) materials based on ab initio calculations and molecular dynamics simulations. The software is based on identifying representative donor/acceptor geometries within interfacial structures obtained from molecular dynamics simulation of donor/acceptor blends and calculating the corresponding Fermi's golden rule CT rate constants within the framework of the linearized-semiclassical approximation. While the methods used are well established, the integration of these state-of-the-art tools originating from different disciplines to study photoinduced CT processes with explicit treatment of the environment, in our opinion, makes this package unique and innovative. The software also provides tools for investigating other observables of interest. After outlining the features and implementation details, the usage and performance of the software are demonstrated with results from an example OPV system.

Photoinduced charge transfer in Zn(II) and Au(III)-ligated symmetric and asymmetric bacteriochlorin dyads: A computational study.

The excited-state properties and photoinduced charge-transfer (CT) kinetics in a series of symmetrical and asymmetrical Zn- and Au-ligated meso-meso-connected bacteriochlorin (BChl) complexes are studied computationally. BChl derivatives, which are excellent near-IR absorbing chromophores, are found to play a central role in bacterial photosynthetic reaction centers but are rarely used in artificial solar energy harvesting systems. The optical properties of chemically linked BChl complexes can be tuned by varying the linking group and involving different ligated metal ions. We investigate charge transfer in BChl dyads that are either directly linked or through a phenylene ring (1,4-phenylene) and which are ligating Zn or Au ions. The directly linked dyads with a nearly perpendicular arrangement of the BChl units bear markedly different properties than phenylene linked dyads. In addition, we find that the dielectric dependence of the intramolecular CT rate is very strong in neutral Zn-ligated dyads, whereas cationic Au-ligated dyads show negligible dielectric dependence of the CT rate. Rate constants of the photo induced CT process are calculated at the semiclassical Marcus level and are compared to fully quantum mechanical Fermi's golden rule based values. The rates are calculated using a screened range separated hybrid functional that offers a consistent framework for addressing environment polarization. We study solvated systems in two solvents of a low and a high scalar dielectric constant.

On the Interplay between Electronic Structure and Polarizable Force Fields When Calculating Solution-Phase Charge-Transfer Rates.

We present a comprehensive analysis of the interplay between the choice of an electronic structure method and the effect of using polarizable force fields vs. nonpolarizable force fields when calculating solution-phase charge-transfer (CT) rates. The analysis is based on an integrative approach that combines inputs from electronic structure calculations and molecular dynamics simulations and is performed in the context of the carotenoid-porphyrin-C60 molecular triad dissolved in an explicit tetrahydrofuran (THF) liquid solvent. Marcus theory rate constants are calculated for the multiple CT processes that occur in this system based on either polarizable or nonpolarizable force fields, parameterized using density functional theory (DFT) with either the B3LYP or the Baer-Neuhauser-Livshits (BNL) density functionals. We find that the effect of switching from nonpolarizable to polarizable force fields on the CT rates is strongly dependent on the choice of the density functional. More specifically, the rate constants obtained using polarizable and nonpolarizable force fields differ significantly when B3LYP is used, while much smaller changes are observed when BNL is used. It is shown that this behavior can be traced back to the tendency of B3LYP to overstabilize CT states, thereby pushing the underlying electronic transitions to the deep inverted region, where even small changes in the force fields can lead to significant changes in the CT rate constants. Our results demonstrate the importance of combining polarizable force fields with an electronic structure method that can accurately capture the energies of excited CT states when calculating charge-transfer rates.

How Well Does a Solvated Octa-acid Capsule Shield the Embedded Chromophore? A Computational Analysis Based on an Anisotropic Dielectric Continuum Model.

The optical properties of chromophores embedded in a water-solvated dimer of octa-acid that forms a molecular-shaped capsule are investigated. In particular, we address the anisotropic dielectric environment that appears to blue-shift excitation energies compared to the free aqueous chromophores. Recently we reported that using an effective scalar dielectric constant ε ≈ 3 appears to reproduce the measured spectra of the embedded coumarins, suggesting that the capsule provides a significant, albeit not perfect, screening of the aqueous dielectric environment. Here, we report absorption energies using a theoretical treatment that includes continuum solvation affected by an anisotropic dielectric function reflecting the high-dielectric environment outside of the capsule and the low-dielectric region within. We report time-dependent density functional theory calculations using a range-separated functional with the Poisson boundary conditions that model the anisotropic dielectric environment. Our calculations find that the anisotropic environment due to the water-solvated hydrophobic capsule is equivalent to a homogeneous effective dielectric constant of ≈3. The calculated values also appear to reproduce measured absorption of the embedded coumarin, where we study the effect of the hydrophobic capsule on the excited state.

On the Role of the Special Pair in Photosystems as a Charge Transfer Rectifier.

The special pair, a bacteriochlorophyll a (BChl) dimer found at the core of bacterial reaction centers, is known to play a key role in the functionality of photosystems as a precursor to the photosynthesis process. In this paper, we analyze the inherent affinity of the special pair to rectify the intrapair photo-induced charge transfer (CT). In particular, we show that the molecular environment affects the nuclear geometry, resulting in symmetry breaking between the two possible intrapair CT processes. To this end, we study the relationships of the intrapair CT and the molecular geometry with respect to the effective dielectric constant provided by the molecular environment. We identify the special pair structural feature that breaks the symmetry between the two molecules, leading to CT rectification. Excited state energies, oscillator strengths, and electronic coupling values are obtained via time-dependent density functional theory, employing a recently developed framework based on a screened range-separated hybrid functional within a polarizable continuum model (SRSH-PCM). We analyze the rectification capability of the special pair by calculating the CT rates using a first-principles-based Fermi's golden rule approach.

Explaining Spectral Asymmetries and Excitonic Characters of the Core Pigment Pairs in the Bacterial Reaction Center Using a Screened Range-Separated Hybrid Functional.

Spectral peaks of the special pair (P) and adjacent pigments in the bacterial reaction center (BRC) are investigated computationally. We employ a novel framework based on a polarization-consistent treatment of the dielectric environment, combining the polarizable continuum model (PCM) with time-dependent screened range-separated hybrid (SRSH) density functional theory. Our calculations quantitatively reproduce recently measured spectral peak splits between P excitonic states and spectral asymmetries within the pairs of excited states of the adjacent bacteriochlorophyll a (BChl) and bacteriopheophytin a (BPhe) pigments. For the special pair, a splitting energy between the absorptive state and a blue-shifted semidark state of 0.07 eV is found in close agreement with the measured value. The spectral asymmetries within the pseudosymmetric pairs of BChl and BPhe pigments are interpreted to result from locally different effective dielectric environments in the A and the B branch, where the latter are exposed to a lesser polarizing environment. We base our analysis on X-ray-resolved structures and where the effect of neighboring pigments on the electronic structure is addressed through an effective dielectric environment. We show that the spectral trends are only reproduced using a polarization-consistent framework based on a screened range-separated hybrid functional, whereas B3LYP-PCM energies fail to provide the correct trends.

Clinical usefulness of epicardial adipose tissue in patients with high-intermediate pre-test probability for coronary artery disease.

BACKGROUND: Epicardial adipose tissue (EAT) is thought to be associated with the extension and severity of coronary artery disease (CAD), and echocardiographic measurement of EAT thickness is considered to be a possible cardiovascular risk indica-tor. The European Society of Cardiology Task Force recommends further non-invasive testing in patients with an intermediate pre-test probability (PTP) for the diagnosis of CAD. AIM: We sought to evaluate the clinical usefulness of performing EAT measurements in patients with a high-intermediate PTP. METHODS: Patients referred to an outpatient clinic with stable chest pain symptoms, with PTP for CAD between 66% and 85%, were included in the study. Echocardiographic measurement of the EAT was identified as the echo-free space between the outer wall of the myocardium and the visceral layer of the pericardium. Single-photon emission computed tomography (SPECT) was performed in all patients. The diagnosis of CAD was based on the presence of reversible perfusion defects on SPECT. RESULTS: A total of 126 patients (76 men, 60.3%) with a mean age of 65.3 ± 9.1 years were recruited. The EAT thickness was 7.3 ± 0.7 mm in patients with positive SPECT and 6.2 ± 0.6 mm in patients with negative SPECT (p < 0.001). Multivariable analysis revealed higher rates of positive SPECT in patients with higher EAT (odds ratio [OR] 9.80; 95% confidence interval [CI] 3.72-25.79; p < 0.001), and receiver operating characteristic curve analysis showed that the greatest specificity was obtained when the cut-off value of EAT thickness was 6.75 mm (sensitivity 76%; specificity 74%). CONCLUSIONS: In patients with high-intermediate PTP, EAT is a useful measurement that may assist in risk stratification.

Predictive values of D-dimer assay, GRACE scores and TIMI scores for adverse outcome in patients with non-ST-segment elevation myocardial infarction.

PURPOSE: To determine the predictive values of D-dimer assay, Global Registry of Acute Coronary Events (GRACE) and Thrombolysis in Myocardial Infarction (TIMI) risk scores for adverse outcome in patients with non-ST-segment elevation myocardial infarction (NSTEMI). PATIENTS AND METHODS: A total of 234 patients (mean age: 57.2±11.7 years, 75.2% were males) hospitalized with NSTEMI were included. Data on D-dimer assay, GRACE and TIMI risk scores were recorded. Logistic regression analysis was conducted to determine the risk factors predicting increased mortality. RESULTS: Median D-dimer levels were 349.5 (48.0-7,210.0) ng/mL, the average TIMI score was 3.2±1.2 and the GRACE score was 90.4±27.6 with high GRACE scores (>118) in 17.5% of patients. The GRACE score was correlated positively with both the D-dimer assay (r=0.215, P=0.01) and TIMI scores (r=0.504, P=0.000). Multivariate logistic regression analysis revealed that higher creatinine levels (odds ratio =18.465, 95% confidence interval: 1.059-322.084, P=0.046) constituted the only significant predictor of increased mortality risk with no predictive values for age, D-dimer assay, ejection fraction, glucose, hemoglobin A1c, sodium, albumin or total cholesterol levels for mortality. CONCLUSION: Serum creatinine levels constituted the sole independent determinant of mortality risk, with no significant values for D-dimer assay, GRACE or TIMI scores for predicting the risk of mortality in NSTEMI patients.

Safety of Early Discharge After Primary Percutaneous Coronary Intervention.

In contrast to ST-elevation myocardial infarction treatment, there is no clear definition for when and which patient to discharge. Our study's main goal was to test the hypothesis that an early discharge strategy (within 48 to 56 hours) in patients with successful primary percutaneous coronary intervention (PPCI) is as safe as in patients who stay longer. The Early Discharge after Primary Percutaneous Coronary Intervention trial was designed in a prospective, randomized, multicenter fashion and registered with http://clinicaltrials.gov (NCT01860079). Of 900 patients with ST-elevation myocardial infarction, the study randomized 769 eligible patients to the early or the standard discharge group. The study's primary outcomes were all-cause mortality and readmission at 30 days. We considered assessment of functional status and health-related quality of life to be secondary outcomes. The early discharge group had significantly shorter length of hospital stay compared with the standard discharge group (45.99 ± 9.12 vs 114.87 ± 63.53 hours; p <0.0001). Neither all-cause mortality nor readmissions were different between the 2 study groups (p = 0.684 and p = 0.061, respectively). Quality-of-life measures were not statistically different between the 2 study groups. Our study reveals that discharge within 48 to 56 hours after successful PPCI is feasible, safe, and does not increase the 30-day readmission rate. Moreover, the patients perceived health status at 30 days did not differ with early discharge.

Cardiac Computed Tomography versus Echocardiography in the Assessment of Stenotic Rheumatic Mitral Valve.

PURPOSE: There are different clinical cardiac applications of dual source computed tomography (DSCT). Here, we aimed to compare the DSCT with the transthoracic echocardiography (TTE) for evaluating the Wilkins score and planimetric mitral valve area (MVA) of a rheumatic stenotic mitral valve. MATERIALS AND METHODS: We prospectively evaluated mitral valvular structure and function in 31 patients with known mitral stenosis undergoing electrocardiogram-gated, second-generation DSCT, in our heart center for different indications. Mitral valve was evaluated using Wilkins score, and also, the planimetric MVA was assessed. RESULTS: We found a significant difference between MVAs determined by DSCT (average 1.42 ± 0.44 cm2) and MVAs determined by TTE (average 1.35 ± 0.43 cm2 ; difference 0.07 ± 0.16 cm2; P = 0.018). Linear regression analysis revealed a good correlation between the two techniques (r = 0.934; P < 0.0001). The limits of agreement for DSCT and TTE in the Bland-Altman analysis were ±0.31 cm2 . DSCT using TTE as the reference enabled good discrimination between mild and moderate-to-severe stenosis and had an area under the ROC curve of 0.967 (CI 0.912-1.023; P < 0.0001). Wilkins scores obtained by DSCT (7.51 ± 1.17, range 5-10) and TTE (8.16 ± 1.27, range 6-10) had a moderate correlation (r = 0.686; P < 0.0001). CONCLUSION: We found that planimetric MVA measurements assessed by DSCT were closely correlated with MVA calculations by TTE. The moderate correlation was observed for the Wilkins score.

The assessment of relationship between fragmented QRS complex and left ventricular wall motion score index in patients with ST elevation myocardial infarction who underwent primary percutaneous coronary intervention.

OBJECTIVES: Fragmented QRS (fQRS) has been found to be associated with high mortality and arrhythmic events in acute coronary syndromes. Regional systolic function using wall motion score index (WMSI) is an alternative to left ventricular ejection fraction (LVEF) for the assessment of left ventricular systolic function. The aim of this study was to investigate the relation between the presence of fQRS on admission electrocardiogram (ECG) and WMSI in ST elevation myocardial infarction (STEMI) underwent primary coronary intervention (PCI). The in-hospital and long-term prognostic significance of persistent fQRS was also evaluated. METHODS: In this retrospective study, 542 patients with a diagnose of STEMI underwent primary PCI were included. Study patients were divided into two groups according to the presence (n = 153) or absence (n = 389) of a fQRS on admission ECG. RESULTS: WMSI was found to be significantly higher in fQRS(+) group compared to the fQRS(-) group (P < 0.001). In multivariete analysis, WMSI was found to be an independent predictor of fQRS, and fQRS was inversely associated with LVEF. The in-hospital reinfarction (P = 0.003), MACE (P = 0.024), intraaortic balloon pump use (P = 0.014), and advanced heart failure (P < 0.001) were found to be significantly more frequent in the fQRS(+) group. The presence of fQRS on admission was found to be associated with an increase in long-term cardiovascular mortality (P = 0.028), and long-term all-cause mortality (P = 0.022). CONCLUSION: WMSI was significantly related with the presence of the fQRS, which reflects the linking between impairment of regional left ventricular systolic function and the presence of severe myocardial injury in STEMI.

Aspirin resistance in patients undergoing hemodialysis and effect of hemodialysis on aspirin resistance.

The aim of this study was to evaluate the prevalence of aspirin resistance (AR) in patients undergoing hemodialysis (HD) and to assess the effect of HD on the results of the Multiplate test. A total of 54 patients undergoing HD were included in this study. Blood samples were taken just before and after the HD session. To determine AR, we used Multiplate test. Platelet aggregation values of the study population were 363.01 ± 225.69 aggregation unit (AU) × minutes before and 375.33 ± 254.05 AU × minutes after the HD (P = .597). There was strong correlation between the values before and after HD (R = .755, P < .0001). The AR status was changed in 9 (16.6%) patients after HD. Agreement of AR status before and after HD was substantial (κ coefficient = .667, P < .0001). The prevalence of AR in patients undergoing HD seems higher than in most of the studied populations, and this study has shown that the AR statuses of a significant number of patients undergoing HD change after an HD session.

Aspirin resistance in patients with impaired renal functions.

BACKGROUND: Cardiovascular diseases (CVD) are the leading cause of death in patients with chronic kidney diseases (CKD). Aspirin resistance (AR) worsens prognosis in CVD. AIM: The aim of this study was to detect AR prevalence in this patient group. METHODS: The 203 patients (mean age 61.84 ± 11.51 years, 128 [63.1%] male) with stable coronary artery disease included in the study were grouped into four study groups according to their estimated glomerular filtration rate (eGFR) values. Multiplate test was used to determine AR. Platelet aggregation results were presented as aggregation unit (AU) × min and values over 300 AU × min were accepted as AR. RESULTS: 61 (30.04%) patients in the whole study population were found to have AR. Differences were detected between AR ratios and multiplate values of the patient groups (p = 0.006 and p = 0.002). AR ratio was highest in patient group 4 (eGFR < 30 mL/min/1.73 m²) and/or on chronic haemodialysis therapy, whereas there was little difference among the other three groups. In multivariate analysis, while AR status was independently related to female sex (OR = 2.31,CI 1.14-4.65, p = 0.019) and mean platelet volume (MPV) (OR = 1.68, CI 1.21-2.33, p = 0.002), multiplate test results were independently related to MPV (b = 0.265, p < 0.0001) and eGFR (b = -0.165, p = 0.025). CONCLUSIONS: The AR ratio was found to be high in severe CKD patients, especially haemodialysis patients, but not in mild and moderate CKD patients. This increased AR ratio in severe CKD patients may affect the prognosis in patients who already have an increased risk for cardiovascular complications.

[Relation of heart-type fatty acid-binding protein with the degree and extent of atherosclerosis in patients with non-ST elevation acute coronary syndrome]. / ST segment yükselmesiz akut koroner sendromlu hastalarda kalp tipi yag asidi baglayici proteinin koroner arter hastaliginin yayginlik ve ciddiyeti ile iliskisi.

OBJECTIVES: The relationship between markers of myocardial ischemia and severity of coronary artery disease (CAD) has been investigated in several studies. In this study, we examined the relationship between severity of CAD and heart-type fatty acid-binding protein (H-FABP), a new marker of ischemia in patients with non-ST-segment elevation acute coronary syndrome (ACS). STUDY DESIGN: This prospective study comprised 49 patients who were referred to the emergency room with a diagnosis of non-ST elevation myocardial infarction. Troponins, creatine kinase-MB, lactate dehydrogenase, and aspartate aminotransferase levels were measured quantitatively, while blood H-FABP levels were measured qualitatively in the 4th-8th hour from the onset of symptoms. All patients underwent coronary angiography within 72 hours after admission. Clinical and coronary angiographic characteristics of patients with positive and negative values of H-FABP were compared. Gensini and SYNTAX scores were used to determine the severity of CAD. RESULTS: There were no statistically significant differences in mean age, gender distribution, risk factors for CAD, ischemic changes on ECG, or Gensini and SYNTAX scores between the H-FABP-negative and -positive groups (p>0.05). The duration of chest pain in the H-FABP-positive group was significantly longer than in the negative group (p<0.001). Troponin, CK-MB, and AST levels as well as thrombolysis in myocardial infarction (TIMI) risk scores were found to be significantly higher in the H-FABP-positive group (p<0.05). CONCLUSION: H-FABP is a useful marker for the diagnosis and risk evaluation of patients with non-ST elevation ACS. However, it is insufficient in evaluating the severity of CAD.

Electrophysiological evaluation of atrioventricular conduction disturbances in transcatheter aortic valve implantation with Edwards SAPIEN prosthesis.

AIMS: Permanent pacemaker requirement is a known complication after transcatheter aortic valve implantation (TAVI). The aim of the present study was to analyze the effects of Edwards SAPIEN prosthesis implantation on atrioventricular conduction. METHODS: The study included 28 patients who underwent TAVI due to severe aortic valve stenosis. An electrophysiological study was performed in the catheterization room immediately before the initial balloon valvuloplasty and immediately after Edwards SAPIEN prosthesis implantation. RESULTS: His-ventricle interval was significantly prolonged postprocedure (55.9 ± 11.5 ms) vs preprocedure (47.3 ± 7.8 ms) (P<.001). The antegrade Wenckebach point was observed to be significantly prolonged postprocedure (354.4 ± 41.3 ms) vs preprocedure (333.7 ± 45.4 ms) (P=.001). Despite atrial-His interval prolongation, it was not statistically significant. After the procedure, we observed significant conduction disturbances in 3 patients (10.7%). These conduction problems recovered before discharge. One of the patients (3.6%) with right bundle branch block + left anterior fascicular block required permanent pacemaker implantation. At postprocedure electrocardiogram, QRS duration increased, QRS axis shifted to the left, and both of the values became normal before discharge. The patient's echocardiographic and clinical parameters were improved during follow-up. CONCLUSION: The effect of Edwards SAPIEN on the conduction system was mostly infranodal and temporary. The physical properties of the Edwards SAPIEN prosthesis may explain this observation. This complication may be lessened if the frame height characteristics can be improved.

Impact of clopidogrel resistance on ST-segment resolution and no-reflow in acute myocardial infarction with ST-elevation patients treated with a primary percutaneous coronary intervention.

INTRODUCTION: A rapid restoration of epicardial coronary flow in acute myocardial infarction is crucial for saving jeopardized myocardium. The no-reflow phenomenon is one of the major problems in a primary percutaneous coronary intervention (PCI) and may be defined as an outcome of different pathological pathways. Our aim was to evaluate clopidogrel resistance in patients who underwent primary PCI and the relationship with the no-reflow phenomenon. MATERIALS AND METHODS: A total of 127 patients (mean age 54.0 ± 11.4 years, 83.7% men) were assessed for this purpose. No-reflow was defined as less than 50% ST-segment resolution on ECG. RESULT: No-reflow was significantly frequent in patients with clopidogrel resistance (25.3 vs. 57.1%, P=0.006). Univariate analysis and multivariate analysis showed that clopidogrel resistance and anterior myocardial infarction were only independent predictors of no-reflow phenomenon in patients treated with a primary PCI during acute myocardial infarction. CONCLUSION: Our study showed that clopidogrel resistance may be one of the responsible mechanisms for the no-reflow phenomenon. Assessment of simple ECG after a primary PCI may help clinicians to determine patients with a poor prognosis.