Journal of Thrombosis and Thrombolysis

, Volume 35, Issue 2, pp 165–174

Influence of HbA1c levels on platelet function profiles associated with tight glycemic control in patients presenting with hyperglycemia and an acute coronary syndrome

A subanalysis of the CHIPS Study (“Control deHIperglucemia y ActividadPlaquetaria en Pacientes conSíndrome Coronario Agudo”)
  • David Vivas
  • Juan C. García-Rubira
  • Esther Bernardo
  • Dominick J. Angiolillo
  • Patricia Martín
  • Alfonso Calle-Pascual
  • Iván Núñez-Gil
  • Carlos Macaya
  • Antonio Fernández-Ortiz
Article

DOI: 10.1007/s11239-012-0834-3

Cite this article as:
Vivas, D., García-Rubira, J.C., Bernardo, E. et al. J Thromb Thrombolysis (2013) 35: 165. doi:10.1007/s11239-012-0834-3

Abstract

Patients with hyperglycemia, an acute coronary syndrome and poor glycemic control have increased platelet reactivity and poor prognosis. However, it is unclear the influence of a tight glycemic control on platelet reactivity in these patients. This is a subanalysis of the CHIPS study. This trial randomized patients with hyperglycemia to undergo an intensive glucose control (target blood glucose 80–120 mg/dL), or conventional glucose control (target blood glucose <180 mg/dL). We analyzed platelet function at discharge on the subgroup of patients with poor glycemic control, defined with admission levels of HbA1c higher than 6.5 %. The primary endpoint was maximal platelet aggregation following stimuli with 20 μM ADP. We also measured aggregation following collagen, epinephrine, and thrombin receptor-activated peptide, as well as P2Y12 reactivity index and surface expression of glycoprotein IIb/IIIa and P-selectin. A total of 67 patients presented HbA1c ≥ 6.5 % (37 intensive, 30 conventional), while 42 had HbA1c < 6.5 % (20 intensive, 22 conventional). There were no differences in baseline characteristics between groups. At discharge, patients with HbA1c ≥6.5 % had significantly reduced MPA with intensive glucose control compared with conventional control (46.1 ± 22.3 vs. 60.4 ± 20.0 %; p = 0.004). Similar findings were shown with other measures of platelet function. However, glucose control strategy did not affect platelet function parameters in patients with HbA1c < 6.5 %. Intensive glucose control in patients presenting with an acute coronary syndrome and hyperglycemia results in a reduction of platelet reactivity only in the presence of elevated HbA1c levels.

Keywords

Platelets HbA1c Acute coronary syndrome 

Abbreviations

ACS

Acute coronary syndrome

ADP

Adenosine diphosphate

DM

Diabetes mellitus

HbA1c

Glycated haemoglobin

LTA

Light transmission aggregometry

TRAP

Thrombin receptor-activated peptide

Introduction

Patients with hyperglycemia and acute coronary syndrome (ACS) have a high risk of cardiovascular events [1, 2, 3]. This prognosis is particularly unfavorable in patients with poor glycemic control [4]. Although blood glucose levels are of most importance to determine glycemic control, glycated haemoglobin (HbA1c) is the established marker of long-term glycemic control of diabetes mellitus (DM) [5]. HbA1c is not only a diagnostic parameter of DM, but also a prognostic biomarker for cardiovascular disease [6, 7]. Several mechanisms may explain the higher rate of adverse outcomes in these patients, such as a greater inflammation status and higher platelet reactivity [8, 9].

Platelet activation plays a key role in the pathophysiology of ACS. Patients with hyperglycemia and DM have consistently been shown to have high platelet reactivity and worse clinical outcomes [10]. There are several studies that assessed whether insulin infusion in patients with DM and ACS resulted in a reduction of cardiovascular events, but the results have been controversial [11, 12, 13, 14]. Nevertheless, in the setting of searching mechanistic explanations to these problems, it has been recently shown that an intensive glucose control with insulin among ACS patients presenting with hyperglycemia results in a reduction in platelet reactivity [15].

This substudy tries to elucidate whether tight glycemic control with insulin infusion in patients with an ACS, hyperglycemia at admission and poor glycemic control (defined by HbA1c levels ≥ 6.5 %) resulted in a decrease in platelet reactivity compared with conventional glucose control, and if this benefit is similar in patients with better glycemic control (HbA1c < 6.5 %).

Methods

Study design and patient population

This is a post hoc assessment of the CHIPS trial (“Control de laHIperglucemia y FunciónPlaquetaria en Pacientes conSíndrome Coronario Agudo”) [15]. This was an open label, single-center, prospective, randomized trial evaluating the effects of intensive glucose control with insulin on platelet function in patients with ACS and hyperglycemia. In brief, patients were enrolled if they were admitted to the Coronary Care Unit of our hospital with a diagnosis of ACS within the preceding 24 h combined with either known DM and blood glucose at admission >120 mg/dL (6.6 mmol/L), or unknown DM with glucose level > 160 mg/dL (8.8 mmol/L) or between 120 and 160 at admission and >120 mg/dL 1 h later. ACS and DM were defined according to the current clinical guidelines [16, 17]. Exclusion criteria included patients on mechanical ventilation, unclear origin of chest pain, refusal to participate, unable to follow-up, concomitant enrollment in other studies, women of childbearing age and/or blood glucose at admission ≥ 400 mg/dL (22.2 mmol/L).

Patients were randomly allocated in a 1:1 fashion to the intensive glucose control group with a glucose target of 80–120 mg/dL (4.4–6.6 mmol/L) or to the conventional control group with a glucose target ≤180 mg/dL (10.0 mmol/L). To achieve these goals, patients on intensive group received an insulin infusion during the initial 24 h according to a predefined algorithm previously described [15]. Thereafter, patients in this group received a daily subcutaneous ultra-slow insulin administration supplemented with rapid-acting insulin for meals. Patients assigned to the conventional group received rapid-acting insulin using a sliding scale algorithm to obtain the target glucose level; in addition patients previously treated with insulin received their usual insulin dosage. All capillary glucose levels were measured by finger stick testing (Accu-Chek® Sensor, Manheim, Germany). For the purpose of this post hoc analysis, patients were startfied into 2 groups according to their levels of glycemic control as defined by levels of HbA1c. Patients with HbA1c levels ≥6.5 % and <6.5 % were defined as poor and optimal glucose control groups, respectively.

The study complied with the Declaration of Helsinki and it was approved by the Ethical Committee of the San Carlos University Hospital. All patients gave their written informed consent to participate in the study.

Platelet function testing

Blood sampling for platelet function assays were collected from an antecubital vein using a 21-gauge needle before assigned insulin treatment (baseline), 24 h after treatment and at hospital discharge. The first 3 mL of blood were discharged to avoid spontaneous platelet activation. All samples were processed within 1 h by physicians who were blinded to the glucose control group assignment. Excepting baseline, 24 h and discharge blood sampling were collected by receiving antiplatelet treatment (aspirin and clopidogrel) the day before at 12:00 am [18].

Platelet aggregation

Platelet aggregation was assessed using light transmittance aggregometry (LTA) as previously described [19]. In brief, LTA was performed in platelet-rich plasma (PRP) by the turbidimetric method in a four-channel aggregometer (Chrono-Log 490 Model, Chrono-Log Corp., Havertown, Pennsylvania) according to standard protocols. The PRP was obtained as a supernatant after centrifugation of citrated blood at 800 rpm for 10 min. and platelet-poor plasma (PPP) was obtained after a second centrifugation of samples at 2,500 rpm. for 10 min. Light transmission was adjusted to 0 % with PRP and to 100 % with PPP for each measurement. Curves were recorded during 5 min. and platelet aggregation was determined as the maximal percent change in light transmittance using PPP as a reference. ADP 5 and 20 μM were used to assess P2Y12-dependent pathway aggregation, while collagen 6 μg/mL and epinephrine 20 μM were used to assess P2Y12-independent pathway aggregation, and TRAP 25 μM to assess thrombin-dependent platelet aggregation.

Platelet P2Y12 reactivity index (PRI)

The PRI was determined through assessment of vasodilator stimulated phosphoprotein (VASP) phosphorylation according to standard protocols [20]. In brief, VASP phosphorylation was measured by quantitative flow cytometry (COULTER EPICS XL-MCL™. SYSTEM II™ Software, Coulter, Miami, Florida) using commercially available labelled monoclonal antibodies (Biocytex Inc., Marseille, France). The PRI was calculated after measuring the mean fluorescence intensity of VASP phosphorylation levels following challenge with prostaglandin E1 and prostaglandin E1 plus ADP. PGE1 increases VASP phosphorylation levels through stimulation of adenylate cyclase while ADP binding to purinergic receptors leads to inhibition of adenylate cyclase. Therefore, the addition of ADP to prostaglandin E1-stimulated platelets reduces levels of prostaglandin E1-induced VASP phosphorylation. Elevated PRI values are indicative of upregulation of the P2Y12 signaling pathway.

Platelet GP IIb/IIIa activation and P-selectin expression

Platelet surface expression of activated GP IIb/IIIa was assessed using PAC-1 (PAC1-FITC conjugated, Becton–Dickinson, Rutherford, New Jersey) antibodies as previously described [21]. P-selectin surface expression was assessed using a phycoerythrin-conjugated anti-CD62P (0.3 mg/mL, Becton–Dickinson, San Jose, California) antibody. Both, activated GP IIb/IIIa and P-selectin expression were assessed before and after addition of ADP 10 μM, and in unstimulated platelets. Samples were analyzed within 2 h by flow cytometry using a COULTER EPICS XL-MCL™ flow cytometer SYSTEM II™ Software (Coulter, Miami, Florida). Platelet activation was expressed as the percentage of platelets positive for antibody binding.

Statistical analysis

The Kolmogorov–Smirnov test was used to analyze the normal distribution of continuous variables. Normally distributed variables are presented as mean ± standard deviation and were compared using the Student t test. Variables that did not follow a normal distribution are presented as median and interquartile range and were compared with the Mann–Whitney U test. Categorical variables are expressed as frequencies and percentages, and were compared with the χ2 test or the Fisher exact test when at least 25 % of values showed an expected cell frequency below 5. All probability values reported are 2-sided, and a value of p < 0.05 was considered to be significant. Statistical analysis was performed using SPSS version 15.0 software (SPSS Inc., Chicago, Illinois).

Results

A total of 115 patients were enrolled into the CHIPS trial. Of these, 67 patients presented HbA1c ≥ 6.5 % (37 were randomly assigned to the intensive glycemic control and 30 to the conventional control), 42 had HbA1c < 6.5 % (20 in the intensive group and 22 to the conventional), and 6 patients were unable to analyze because HbA1c values were unavailable. Table 1 shows baseline demographics, clinical characteristics, laboratory data and angiographic findings of patients with poor glycemic control, according to treatment assignment. No significant differences were observed between groups. In addition, demographic and clinical parameters of patients with HbA1c < 6.5 % did not show differences between intensive and conventional control (Table 2).
Table 1

Baseline characteristics according to treatment group. (HBA1C ≥ 6.5 %)

 

Intensive glucose control

Conventional glucose control

p value

(n = 37)

(n = 30)

Age (years), mean ± SD

66.8 ± 10.5

68.5 ± 11.9

0.54

Male, n (%)

22 (59.5)

20 (66.7)

0.54

Risk factors, n (%)

 Current smoking

13 (35.1)

7 (23.3)

0.44

 Hypertension

26 (70.3)

22 (73.3)

0.78

 Dyslipidemia

21 (56.8)

16 (53.3)

0.78

 Known DM

32 (86.5)

22 (73.3)

0.08

 Obesity (BMI > 30 kg/m2)

17 (45.9)

17 (56.7)

0.38

Medical history, n (%)

 Previous MI

13 (35.1)

9 (30.0)

0.71

 Previous PCI

8 (32.0)

4 (22.2)

0.48

 Previous stroke

1 (2.7)

0 (0.0)

0.36

 Symptomatic PVD

3 (8.1)

4 (13.3)

0.49

 Chronic kidney disease

4 (10.8)

1 (3.3)

0.25

Clinical presentation, n (%)

 STEMI

16 (43.2)

9 (30.0)

0.26

 Anterior STEMI

10 (27.0)

6 (20.0)

0.40

 Killip class ≥ 2

11 (29.7)

14 (46.7)

0.15

 GRACE score ≥ 140

20 (54.1)

18 (60.0)

0.63

Laboratory data

 Baseline glucose (mg/dL), median (IQR)

190 (162–248)

199 (159–238)

0.62

 Hematocrit (%), mean ± SD

38.3 ± 5.7

39.6 ± 5.9

0.33

 Platelet count (1,000/mm3), mean ± SD

218.8 ± 77.0

212.8 ± 47.5

0.69

 Creatinine clearance (mL/min)a, mean ± SD

79.6 ± 35.6

81.3 ± 31.1

0.83

 Peak CK (UI/L), median (IQR)

521 (227–1143)

456 (143–919)

0.45

 Peak troponin I (ng/mL), median (IQR)

18.1 (2.3–41.1)

13.1 (2.8–28.2)

0.79

Angiographic characteristics, n (%)

 Coronary angiography

36 (97.3)

29 (96.7)

0.87

 Number of narrowed (≥50 %) coronary arteries, mean ± SD

1.8 ± 0.9

1.9 ± 0.8

0.51

 Left anterior descending

19 (52.8)

17 (58.6)

0.54

 Left circumflex

19 (52.8)

16 (55.2)

0.85

 Right coronary

15 (41.7)

17 (51.6)

0.17

 Multivessel disease

19 (52.8)

18 (62.1)

0.45

 No significant coronary narrowing

3 (8.3)

0 (0.0)

0.11

BMI body mass index, CAD coronary artery disease, CK creatinine kinase, DM diabetes mellitus, GRACE global registry of acute cardiac events, HbA1c glycated hemoglobin A1c, IQR interquartile range, MI myocardial infarction, PCI percutaneous coronary intervention, PVD peripheral vascular disease, STEMI ST elevation myocardial infarction

aAssessed by de Crockcroft & Gault formula [22]

Table 2

Baseline characteristics according to treatment group. (HBA1C < 6.5 %)

 

Intensive glucose control

Conventional glucose control

p value

(n = 20)

(n = 22)

Age (years), mean ± SD

66.5 ± 14.6

67.0 ± 13.1

0.53

Male, n (%)

14 (70.0)

14 (63.6)

0.75

Risk factors, n (%)

 Current smoking

6 (30.0)

8 (36.4)

0.81

 Hypertension

12 (60.0)

17 (77.3)

0.32

 Dyslipidemia

8 (40.0)

10 (45.5)

0.76

 Known DM

5 (25.0)

8 (36.4)

0.51

 Obesity (BMI > 30 kg/m2)

3 (15.0)

5 (22.7)

0.70

Medical history, n (%)

 Previous MI

1 (5.0)

3 (13.6)

0.24

 Previous PCI

1 (5.0)

2 (9.1)

0.77

 Previous stroke

1 (5.0)

0 (0.0)

0.47

 Symptomatic PVD

3 (15.0)

3 (13.6)

0.90

 Chronic kidney disease

1 (5.0)

2 (9.1)

0.60

Clinical presentation, n (%)

 STEMI

13 (65.0)

11 (50.0)

0.18

 Anterior STEMI

15 (25.0)

2 (9.1)

0.10

 Killip class ≥ 2

6 (30.0)

5 (22.7)

0.73

 GRACE score ≥ 140

15 (75.0)

13 (59.1)

0.22

Laboratory data

 Baseline glucose (mg/dL), median(IQR)

159 (133–189)

152 (128–178)

0.54

 Hematocrit (%), mean ± SD

39.9 ± 6.0

37.1 ± 6.7

0.76

 Platelet count (1,000/mm3), mean ± SD

213.1 ± 103.3

246.0 ± 60.3

0.45

 Creatinine clearance (mL/min)a, mean ± SD

71.2 ± 30.9

72.4 ± 36.1

0.66

 Peak CK (UI/L), median(IQR)

826 (401–1250)

740 (386–1,104)

0.19

 Peak troponin I (ng/mL), median(IQR)

26.0 (4.6–48.7)

22.9 (3.8–41.6)

0.31

Angiographic characteristics, n (%)

 Coronary angiography

20 (100.0)

21 (95.5)

0.72

 Number of narrowed (≥50 %) coronary arteries, mean ± SD

1.6 ± 0.6

1.5 ± 0.6

0.94

 Left anterior descending

11 (55.0)

14 (63.6)

0.29

 Left circumflex

8 (40.0)

11 (50.0)

0.32

 Right coronary

11 (55.0)

13 (59.0)

0.68

 Multivessel disease

10 (50.0)

12 (54.5)

0.80

 No significant coronary narrowing

3 (15.0)

1 (4.5)

0.14

BMI body mass index, CAD coronary artery disease, CK creatinine kinase, DM diabetes mellitus, GRACE global registry of acute cardiac events, HbA1c glycated hemoglobin A1c, IQR interquartile range, MI myocardial infarction, PCI percutaneous coronary intervention, PVD peripheral vascular disease, STEMI ST elevation myocardial infarction

aAssessed by de Crockcroft & Gault formula [22]

In-hospital management and adverse outcomes of patients with HbA1c ≥ 6.5 % are described in Table 3. Patients treated with intensive glycemic control showed a significant reduction of glucose levels at 24 h and at discharge (p < 0.001 for both). Hypoglycemic episodes were more frequent with the intensive than the conventional control (35.1 vs. 3.3 %, p < 0.001), but with no differences in episodes of severe hypoglycemia. These findings were similar in patients with HbA1c < 6.5 % (Table 4).
Table 3

In-hospital management and adverse outcomes according to treatment group. (HBA1C ≥ 6.5 %)

 

Intensive glucose control

Conventional glucose control

p value

(n = 37)

(n = 30)

Blood glucose at 24 h (mg/dL), median(IQR)

112 (86–148)

160 (122–214)

<0.001

Hypoglycemia < 60 mg/dL, n (%)

13 (35.1)

1 (3.3)

<0.001

Severe hypoglycemia < 40 mg/dL, n (%)

2 (5.4)

0 (0.0)

0.18

Blood glucose at discharge (mg/dL), median (IQR)

108 (92–138)

149 (116–220)

<0.001

Coronary revascularization procedures, n (%)

 PCI with drug-eluting stent

18 (48.6)

14 (46.7)

0.81

 PCI with bare-metal stent

6 (16.2)

5 (16.7)

0.93

 Fibrinolysis

3 (8.1)

3 (10.0)

0.57

 CABG

2 (5.4)

4 (13.3)

0.27

 No revascularization

8 (22.2)

7 (23.3)

0.92

Drug therapy during hospitalization, n (%)

 Aspirin

36 (97.3)

28 (93.3)

0.41

 Clopidogrel

 

  600 mg loading dose

13 (35.1)

9 (30.0)

0.66

  300 mg loading dose

15 (40.5)

12 (40.0)

0.96

  No loading dose

9 (24.3)

9 (30.0)

0.60

  75 mg maintenance dose

30 (81.1)

24 (80.0)

0.91

 GP IIb/IIIa inhibitors

22 (59.5)

18 (60.0)

0.52

 Unfractioned heparin

27 (45.8)

20 (66.7)

0.54

 Enoxaparin

19 (51.4)

18 (60.0)

0.36

 Beta-blockers

30 (81.1)

24 (80.0)

0.91

 ACE inhibitors/ARB

30 (81.1)

27 (90.0)

0.50

 Statins

36 (97.3)

28 (93.3)

0.32

Adverse in-hospital outcomes, n (%)

 Death

2 (5.4)

3 (10.0)

0.40

 Re-infarction

1 (2.7)

1 (3.3)

0.86

 Repeated target-vessel revascularization

0 (0.0)

2 (6.6)

0.32

 Cardiogenic shock

1 (2.7)

3 (10.0)

0.16

 Complete AV block

2 (5.4)

2 (6.6)

0.78

 Major bleedinga

1 (2.7)

2 (6.6)

0.50

 Minor bleedinga

2 (5.4)

3 (10.0)

0.46

 Days in CCU, median(IQR)

2 (2–3)

2 (2–3)

0.60

 Days in hospital, median(IQR)

7 (6–10)

7 (6–11)

0.92

ACE angiotensin-converting enzyme, ARB angiotensin receptor blocker, AV auriculo-ventricular; CABG coronary artery bypass graft, CCU coronary care unit, GP glycoprotein, IQR interquartile range, PCI percutaneous coronary intervention

aAccording to the TIMI classification [23]

Table 4

In-hospital management and adverse outcomes according to treatment group. (HBA1C < 6.5 %)

 

Intensive glucose control

Conventional glucose control

p value

(n = 20)

(n = 22)

Blood glucose at 24 h (mg/dL), median(IQR)

109 (75–132)

138 (108–149)

<0.001

Hypoglycemia < 60 mg/dL, n (%)

8 (40.0)

0 (0.0)

<0.001

Severe hypoglycemia < 40 mg/dL, n (%)

0 (0.0)

0 (0.0)

N.A.

Blood glucose at discharge (mg/dL), median (IQR)

100 (72–126)

136 (98–148)

<0.001

Coronary revascularization procedures, n (%)

 PCI with drug-eluting stent

7 (35.0)

9 (41.0)

0.68

 PCI with bare-metal stent

4 (20.0)

4 (18.2)

0.91

 Fibrinolysis

4 (20.0)

2 (9.1)

0.14

 CABG

1 (5.0)

2 (9.1)

0.77

 No revascularization

4 (20.0)

4 (18.2)

0.83

Drug therapy during hospitalization, n (%)

 Aspirin

20 (100.0)

21 (95.5)

0.72

 Clopidogrel

   

  600 mg loading dose

12 (60.0)

13 (59.1)

0.87

  300 mg loading dose

4 (20.0)

5 (22.7)

0.76

  No loading dose

3 (15.0)

4 (18.2)

0.88

  75 mg maintenance dose

17 (85.0)

18 (81.8)

0.52

 GP IIb/IIIa inhibitors

11 (55.0)

10 (45.5)

0.30

 Unfractioned heparin

6 (30.0)

3 (13.6)

0.08

 Enoxaparin

11 (55.0)

10 (45.5)

0.30

 Beta-blockers

14 (70.0)

18 (81.8)

0.34

 ACE inhibitors/ARB

17 (85.0)

18 (81.8)

0.92

 Statins

20 (100.0)

21 (95.5)

0.72

Adverse in-hospital outcomes, n (%)

 Death

0 (0.0)

0 (0.0)

N.A.

 Re-infarction

1 (5.0)

2 (9.1)

0.77

 Repeated target-vessel revascularization

1 (5.0)

1 (4.5)

0.86

 Cardiogenic shock

0 (0.0)

2 (9.1)

0.54

 Complete AV block

0 (0.0)

1 (4.5)

0.46

 Major bleedinga

0 (0.0)

0 (0.0)

N.A.

 Minor bleedinga

1 (5.0)

2 (9.1)

0.77

 Days in CCU, median (IQR)

2 (2–3)

2 (2–3)

0.60

 Days in hospital, median (IQR)

7 (6–11)

7 (6–11)

0.91

ACE angiotensin-converting enzyme, ARB angiotensin receptor blocker, AV auriculo-ventricular; CABG coronary artery bypass graft, CCU coronary care unit, GP glycoprotein, IQR interquartile range, PCI percutaneous coronary intervention, N.A. non applicable

aAccording to the TIMI classification [23]

Concerning direct comparison between poor versus optimal previous glucose control groups, there were no significant differences, excepting previous DM and glucose levels, more frequents in HbA1c ≥ 6.5 % group (Supplementary Tables 1 and 2).

Table 5 summarizes platelet function profiles according to HbA1c levels. No differences in platelet reactivity were found at baseline, and at 24 h of randomization in both groups. The primary endpoint of maximal platelet aggregation (MPA) after ADP 20 μM stimuli was significantly reduced at hospital discharge in patients with poor glycemic control randomized to intensive treatment, compared with conventional therapy (46.1 ± 22.3 vs. 60.4 ± 20.0 %, p = 0.004). Platelet reactivity was better maintained at discharge in both P2Y12-dependent and—independent aggregation pathways, and was it also observed in platelet activation assessed with the PRI, GP IIb/IIIa surface activation and P-selectin expression (Fig. 1). However, patients with HbA1c < 6.5 % did not shown a better maintaining in the primary endpoint (52.1 ± 14.5 vs. 57.3 ± 12.8 %; p = 0.27) or in any of the other pharmacodynamics parameters at hospital discharge (Fig. 2).
Table 5

Platelet function profiles at baseline and at 24 h after randomization

 

HbA1c < 6.5 %

HbA1c ≥ 6.5 %

Baseline

24 HR

Baseline

24 HR

IG

CG

p value

IG

CG

p value

IG

CG

p value

IG

CG

p

value

(n = 20)

(n = 22)

(n = 20)

(n = 22)

(n = 37)

(n = 30)

(n = 37)

(n = 30)

Platelet aggregation (%)

 ADP 5 μM

18.4 ± 21.3

28.8 ± 24.9

0.15

19.1 ± 13.2

26.2 ± 19.9

0.20

16.6 ± 25.9

18.8 ± 22.7

0.21

13.5 ± 16.5

15.6 ± 15.3

0.61

 ADP 20 μM

33.4 ± 24.9

40.9 ± 30.8

0.38

38.9 ± 18.7

39.5 ± 23.2

0.93

35.3 ± 30.2

27.8 ± 28.8

0.33

24.4 ± 23.2

25.4 ± 21.2

0.86

 Collagen 6 μg/ml

20.6 ± 30.8

31.9 ± 34.1

0.28

18.3 ± 20.4

30.9 ± 26.5

0.11

29.2 ± 30.7

25.5 ± 27.0

0.62

18.8 ± 20.8

21.9 ± 23.2

0.58

 Epinephrine 20 μM

14.1 ± 20.4

21.5 ± 23.7

0.31

21.5 ± 15.0

22.8 ± 20.3

0.83

21.5 ± 23.7

18.9 ± 23.1

0.66

10.8 ± 14.5

17.0 ± 15.6

0.12

 TRAP 25 μM

48.5 ± 22.2

50.2 ± 31.2

0.83

47.8 ± 22.8

55.7 ± 20.3

0.28

49.9 ± 28.7

38.6 ± 29.2

0.13

39.4 ± 25.1

42.8 ± 27.1

0.64

Platelet activation (%)

 PRI

69.1 ± 19.9

58.9 ± 22.5

0.13

56.3 ± 24.6

58.3 ± 24.9

0.81

61.1 ± 25.1

66.2 ± 19.2

0.35

56.4 ± 26.7

55.6 ± 27.8

0.88

 P-selectin expression (before addition of ADP 10 μM)

29.5 ± 24.7

31.0 ± 29.8

0.50

26.0 ± 21.4

29.9 ± 24.2

0.68

31.0 ± 29.4

27.3 ± 26.4

0.59

21.1 ± 20.2

23.7 ± 20.2

0.56

 GP IIb/IIIa (PAC-1) expression (before addition of ADP 10 μM)

53.0 ± 20.6

49.6 ± 21.9

0.61

37.7 ± 23.7

48.8 ± 19.1

0.23

42.2 ± 22.8

43.2 ± 25.4

0.86

31.7 ± 16.1

38.3 ± 23.4

0.21

 P-selectin expression (after addition of ADP 10 μM)

30.0 ± 25.1

35.0 ± 37.0

0.33

39.2 ± 22.3

48.5 ± 31.4

0.14

44.9 ± 33.4

43.3 ± 28.4

0.83

34.6 ± 27.8

41.6 ± 28.4

0.34

 GP IIb/IIIa (PAC-1) expression (after addition of ADP 10 μM)

65.4 ± 19.9

64.1 ± 19.2

0.83

50.9 ± 21.7

63.9 ± 16.8

0.06

55.6 ± 24.7

56.0 ± 24.7

0.95

45.9 ± 20.7

51.3 ± 24.4

0.36

IG intensive group, CG conventional group. ADP adenosin diphosphate, GP glycoprotein, PRI platelet P2Y12 reactivity index, TRAP thrombin receptor-activated peptide

Data are presented as mean ± SD

Fig. 1

Platelet reactivity in patients with poor glycemic control (HbA1c ≥ 6.5 %) treated with insulin infusion, compared with conventional treatment, at hospital discharge. Data are presented as mean ± SD

Fig. 2

Platelet reactivity in patients with poor glycemic control (HbA1c < 6.5 %) treated with insulin infusion, compared with conventional treatment, at hospital discharge. Data are presented as mean ± SD

Discussion

The present results confirm the importance of maintaining a correct glycometabolic status in patients suffering an ACS. In patients with poor glycemic control admitted with an ACS, an intensive treatment with insulin resulted in a better maintaining of platelet reactivity at discharge. Despite good adherence to guidelines concerning pharmacological therapies and invasive procedures, patients with poor glycemic control present higher mortality rate, stent thrombosis and bleeding risk than patients with better glycemic control [24]. This poor glycemic control has been classically defined by the increase of glucose levels, but there are some studies that recently showed that admission value of HbA1c levels are prognostic factor associated with mortality in patients with an ACS [25].

Patients with coronary artery disease on dual antiplatelet treatment (aspirin and clopidogrel) and DM present platelet dysfunction, especially in insulin-treated DM [8]. Moreover, a worse metabolic control of DM is related with a reduction of sensitivity of platelets to aspirin, and with aspirin-resistance [26, 27]. This concern is of most importance, since there are a significant amount of patients with undiagnosed DM presented with an ACS and hyperglycemia at admission [28]. As previously described, an intensive treatment with insulin in patients with and ACS and hyperglycemia, results in a reduction of platelet function, compared with conventional treatment in both DM and non-DM patients [15]. In this substudy, we demonstrated that a tight glycemic control with insulin resulted in a significant reduction in platelet aggregation and activation, compared with a conventional control. Of note, these results were not confirmed in the subgroup of patients with HbA1c < 6.5 %. Although some studies showed that poor glucose control was associated to differences in responsiveness to antiplatelet therapy, an intensive insulin therapy could contribute to reduce platelet reactivity, compared with conventional management [20].

These results reinforce the importance of a more aggressive treatment in patients with worse metabolic profile. In fact, recent reports have stated that patients with poor glycemic control could benefit of more aggressive treatments, such as new antiplatelets drugs. Thus, prasugrel and ticagrelor, more potent ADP P2Y12 receptor antagonists than clopidogrel, have been developed [29]. Both drugs have shown a significant reduction of cardiovascular outcomes (death, myocardial infarction and stroke), compared to clopidogrel, in patients with an ACS and HbA1c ≥ 6 % [24, 30].

Interestingly, the reduction of platelet function was demonstrated with multiple tests, which means that the benefit of an intensive insulin therapy was not only in P2Y12-ADP dependent pathways, but also for independent aggregation pathways. It has been hypothesized in the literature that insulin could modulate platelet activation through its receptor, IRS-1, but further research are needed [31]. Moreover, this platelet function reduction showed in our study could result in a better prognosis for these patients. Angiolillo et al. [10] showed that patients with DM and coronary artery disease and higher platelet reactivity despite treatment with aspirin and clopidogrel, presented more frequent cardiovascular events than patients with better residual platelet function. In this way, Geisler et al. [32] showed that residual platelet aggregation was associated with a higher rate of early stent thrombosis in patients undergoing coronary interventions. Our study was not designed to find differences in cardiovascular outcomes; however, it could provide an explanation of the mechanisms why an intensive insulin therapy could improve the prognosis of these patients.

This substudy presents some limitations. Although this was a randomized trial, it was a unicenter study. The use of Gp IIb/IIIa inhibitors in more than a half of patients with poor glycemic control, according to current guidelines, limits the fact of founding differences at 24 h of randomization [16, 17]. Moreover, and after post hoc power calculation, the study lacked of a sample size and power enough to detect differences between poor and better glycemic control groups (the latter smaller than the poor control group), specifically in adverse outcomes such as hypoglycemic events. We have observed elevated spontaneous P-selectin expression in unstimulated platelets due to real clinical drawing sample conditions but the results are consistent with those obtained in stimulated platelet with ADP as agonist. Nevertheless, and despite these limitations, the consistency of the statistical analysis reinforce the value of the results obtained.

Conclusions

An intensive glucose control in patients presented with an acute coronary syndrome, hyperglycemia, and previous poor glycemic control results in a reduction and a better maintaining of platelet reactivity at discharge. This effect was not observed in patients with better glycemic control.

Acknowledgments

This study was funded by a non-restricted grant from the Fundación Investigación y Desarrollo Area Cardiovascular FIC (Madrid, Spain CIF G-81563801).

Conflict of interest

There are no relationship to disclosure between authors and the industry related to the present work.

Supplementary material

11239_2012_834_MOESM1_ESM.doc (58 kb)
Supplementary material 1 (DOC 58 kb)
11239_2012_834_MOESM2_ESM.doc (54 kb)
Supplementary material 2 (DOC 54 kb)

Copyright information

© Springer Science+Business Media New York 2012

Authors and Affiliations

  • David Vivas
    • 1
  • Juan C. García-Rubira
    • 1
  • Esther Bernardo
    • 1
  • Dominick J. Angiolillo
    • 1
  • Patricia Martín
    • 1
  • Alfonso Calle-Pascual
    • 1
  • Iván Núñez-Gil
    • 1
  • Carlos Macaya
    • 1
  • Antonio Fernández-Ortiz
    • 1
  1. 1.Cardiovascular InstituteSan Carlos University HospitalMadridSpain

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