Impact of previous insulin therapy on the prognosis of diabetic patients with acute coronary syndromes

Article · October 2010with17 Reads
DOI: 10.1590/S0004-27302010000700005 · Source: PubMed
Abstract
To determine whether previous insulin treatment independently influences subsequent outcomes in diabetic patients with ACS (acute coronary syndromes). 375 diabetic patients with ACS, divided in 2 groups: Group A (n = 69)--previous insulin and Group B (n = 306)--without previous insulin. Predictors of 1-year mortality and major adverse cardiac events (MACE) were analyzed by Cox regression analysis. Group A had more previous stroke (17.4% vs. 9.2%, p = 0.047) and peripheral artery disease (13.0% vs. 3.6%, p = 0.005). They had significantly higher admission glycemia and lower LDL cholesterol. There were no significant differences in the type of ACS, in 1-year mortality (18.2% vs. 10.4%, p = 0.103) or MACE (32.1% vs. 23.0%, p = 0.146) between groups. In multivariate analysis, insulin treatment was neither an independent predictor of 1-year mortality nor of MACE. Despite the more advanced atherosclerotic disease, diabetics under insulin had similar outcomes to those without insulin. Insulin may protect diabetics from the expected poor adverse outcome of an advanced atherosclerotic disease.
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Arq Bras Endocrinol Metab. 2010;54/7
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original article
1 Cardiology Department, Coimbra
University Hospital, Portugal
2 Medical School, Universidade
de Coimbra, Portugal
Correspondence to:
Natália António
Departamento de Cardiologia,
Hospital da Universidade de
Coimbra
Praceta Mota Pinto − 3000-075 −
Coimbra, Portugal
natalia.antonio@gmail.com
Received on Mar/26/2010
Accepted on Aug/31/2010
Impact of previous insulin therapy
on the prognosis of diabetic patients
with acute coronary syndromes
Impacto da insulinoterapia prévia no prognóstico dos
pacientes diabéticos com síndromes coronárias agudas
Natália António1,2, Francisco Soares1, Carolina Lourenço1,2,
Fátima Saraiva1, Francisco Gonçalves1, Pedro Monteiro1,2,
Lino Gonçalves1,2, Mário Freitas1,2, Luís A. Providência1,2
ABSTRACT
Objective:
To determine whether previous insulin treatment independently influences subse-
quent outcomes in diabetic patients with ACS (acute coronary syndromes).
Subjects and me-
thods:
375 diabetic patients with ACS, divided in 2 groups: Group A (n = 69) – previous insulin
and Group B (n = 306) without previous insulin. Predictors of 1-year mortality and major
adverse cardiac events (MACE) were analyzed by Cox regression analysis.
Results:
Group A
had more previous stroke (17.4% vs. 9.2%, p = 0.047) and peripheral artery disease (13.0% vs.
3.6%, p = 0.005). They had significantly higher admission glycemia and lower LDL cholesterol.
There were no significant differences in the type of ACS, in 1-year mortality (18.2% vs. 10.4%,
p = 0.103) or MACE (32.1% vs. 23.0%, p = 0.146) between groups. In multivariate analysis, insulin
treatment was neither an independent predictor of 1-year mortality nor of MACE.
Conclusion:
Despite the more advanced atherosclerotic disease, diabetics under insulin had similar outco-
mes to those without insulin. Insulin may protect diabetics from the expected poor adverse
outcome of an advanced atherosclerotic disease.
Arq Bras Endocrinol Metab. 2010;54(7):612-9
Keywords
Insulin; diabetes; acute coronary syndromes; outcomes
RESUMO
Objectivo:
Avaliar se a insulinoterapia prévia influencia de forma independente o prognóstico de
diabéticos após uma síndrome coronária aguda (SCA).
Sujeitos e métodos:
375 doentes diabéti-
cos com SCA, divididos em 2 grupos: Grupo A (n = 69) – sob insulinoterapia prévia e Grupo B (n =
306) – sem insulinoterapia prévia. Os preditores de mortalidade a um ano e de eventos cardíacos
adversos maiores (MACE) foram determinados pela regressão de Cox.
Resultados:
Verificou-se
maior proporção de acidente vascular cerebral prévio (17,4% vs. 9,2%, p = 0,047) e doença arte-
rial periférica (13,0% vs. 3,6%, p = 0,005) no Grupo A. Esses doentes apresentaram glicemia na
admissão significativamente mais elevada e LDL inferior. Não houve diferenças estatisticamente
significativas no tipo de SCA, na mortalidade (18,2% vs. 10,4%, p = 0,103) e MACE (32,1% vs.
23,0%, p = 0,146) em um ano entre os 2 grupos. Na análise multivariada, a insulinoterapia prévia
não foi preditor independente nem de mortalidade, nem de MACE em 1 ano.
Conclusão:
Apesar
da doença aterosclerótica mais avançada, os diabéticos previamente insulino-tratados têm um
prognóstico semelhante aos não insulino-tratados. A insulinoterapia crônica poderá proteger os
diabéticos da evolução desfavorável própria da doença aterosclerótica avançada.
Arq Bras Endocrinol
Metab. 2010;54(7):612-9
Descritores
Insulina; diabetes; síndromes coronárias agudas; prognóstico
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Arq Bras Endocrinol Metab. 2010;54/7
Insulin and acute coronary syndromes
INTRODUCTION
Despite signicant advances in the treatment of di-
abetic patients with Acute Coronary Syndromes
(ACS), their prognosis remains worse than that of non-
diabetics (1,2).
The risk of developing coronary artery disease
(CAD) in diabetics is two to four times greater than
that of non-diabetics, and diabetics with no history of
previous myocardial infarction (MI) have the same risk
of future cardiovascular events as non-diabetics who
have suffered a previous heart attack (3,4). These re-
sults led the “Adult Treatment Panel III of the Natio-
nal Cholesterol Education Program” to establish diabe-
tes mellitus (DM) as a CAD risk equivalent, mandating
aggressive anti-atherosclerotic treatment (5).
The metabolic abnormalities caused by DM induce
endothelial dysfunction. Among those abnormalities
chronic hyperglycemia, dyslipidemia and insulin resis-
tance appear to be the most relevant. The progression
of insulin resistance to diabetes parallels the progres-
sion of endothelial dysfunction to atherosclerosis (6).
Previous studies have shown that diabetic patients
under chronic insulin therapy have a poorer prognosis
after percutaneous coronary intervention (PCI) than
non-insulin-treated diabetics (7-9). In the context of
heart failure, prior insulin therapy also seems to be asso-
ciated with increased 1-year mortality (10). However, it
is unknown whether this represents an effect of insulin
itself or the need for insulin is only a marker of a more
advanced form of the disease.
Despite the high prevalence of diabetes in ACS pa-
tients, there are no studies in the literature addressing
the impact of prior insulin therapy on the prognosis of
diabetic patients after an ACS.
The main objectives of this work were to compa-
re demographic and clinical characteristics, therapeutic
approaches and clinical outcomes after an ACS between
diabetics previously treated with insulin and non-insu-
lin-treated diabetics, and to verify whether prior insulin
therapy independently inuences the prognosis of dia-
betic patients after an ACS.
SUBJECTS AND METHODS
Study design
This is a prospective, observational study (prospective
data collection with a retrospective analysis of results)
of 375 patients with previously known DM or newly
diagnosed DM, consecutively admitted into a single in-
tensive coronary care unit for ACS, between May 2004
and December 2006.
All patients without previously known diabetes
underwent an Oral Glucose Tolerance Test (OGTT)
on the 4th or 5th day of hospitalization. The diagnosis
of new DM was established on the 4th or 5th day of
hospitalization in patients without previously known
diabetes and fasting blood glucose levels equal to or
greater than 126 mg/dL, or whose OGTT revealed a
blood glucose level equal to or greater than 200 mg/dL
two hours after the administration of 75 grams of glu-
cose (11).
We proceeded to the analysis of a database with
standardized records made during the patient’s hos-
pitalization, which includes: demographic, clinical,
electrocardiographic and laboratorial data, medication
(previous, at admission and at discharge), type of ACS,
in-hospital complications(including ventricular brilla-
tion, cardiogenic shock, cardiac arrest, recurrent MI
and acute pulmonary edema), length of hospital stay
and patient destination after discharge.
These patients underwent a one year follow-up. The
occurrence of unplanned revascularization, re-infarc-
tion, cerebrovascular accident (CVA) and death from
any cause was recorded.
We also analyzed the combined endpoint of cardio-
vascular death, myocardial nonfatal re-hospitalization
for UA or MI and unplanned PCI during the rst year
– MACE (Major Adverse Cardiac Events).
The study population was divided into two groups
according to the previous use (Group A, n = 69) or not
(Group B, n = 306) of insulin.
This investigation conforms to the principles outli-
ned in the Declaration of Helsinki, was approved by the
Ethical Committee of Clinical Research of the Coimbra
University Hospital, and written informed consent was
obtained from all patients.
Statistical analysis
Continuous variables are presented as mean ± stan-
dard deviation (SD). Student’s t test or Mann-Whitney
test were used for comparison of the two subgroups,
according to whether the variables had normal distri-
bution or not, respectively. Categorical variables are
expressed as frequencies and percentages and were
analyzed by c2 test or Fisher’s exact test. A p value
< 0.05 was considered statistically signicant.
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Arq Bras Endocrinol Metab. 2010;54/7
Insulin and acute coronary syndromes
Multivariate analysis using the Cox regression model
was performed to assess the independent effect of prior
insulin therapy in the incidence of MACE and morta-
lity at one year.Predetermined (in univariate analysis)
or clinically relevant variables were entered into these
multivariable regression models. The impact of prior
insulin therapy on one-year survival and MACE-free
survival was evaluated by Kaplan-Meier analysis.
RESULTS
General characterization of the study population
Of the 375 patients included in the study, 252 (67.2%)
were male, and the mean age was 70.0 ± 10.0 years.
Regarding the type of ACS, 55 patients (14.7%) had Uns-
table Angina (UA), 205 (54.7%) non ST segment eleva-
tion myocardial infarction (NSTEMI) and 115 (30.6%)
ST segment elevation myocardial infarction (STEMI).
Regarding cardiovascular risk factors, 84.8% of pa-
tients had a history of hypertension, 84.7% hyperlipi-
demia and 10.2% had smoking habits.With respect to
past medical history, 23.5% of patients had prior MI,
and history of heart failure and of stroke or transientis-
chemic attack (TIA) was present in 2.5% and 10.7%,
respectively. Newly diagnosed diabetes was found in
30% of all patients.
Regarding the electrocardiographic and hemody-
namic data on admission, 78.0% of patients presented
with Killip class I, 86.1% were in sinus rhythm (SR)
and 11.5% in atrial brillation (AF) in the rst elec-
trocardiogram (ECG) performedafter hospital admis-
sion, and 2.7% of patients had left bundle branch block
(LBBB). The mean blood glucose level at admission
was 137.0 ± 65 mg/dL.
Comparison of previously insulin-treated and
non-insulin-treated diabetics
Concerning the comparison between the two groups,
previously insulin-treated diabetics had a higher preva-
lence of peripheral arterial disease (PAD), previous MI
and prior stroke or TIA(Table 1). Regarding previous
cardiovascular treatment, insulin-treated diabetics were
more frequently treated with aspirin (55.1 vs. 35.6%, p
= 0.003), angiotensin-converting enzyme (ACE) inhi-
bitors (55.1 vs. 41.2%, p = 0.036), β-blockers (29.0 vs.
18.3%, p = 0.046), nitrates (29.0 vs. 16.3%, p = 0.015)
and diuretics (39.1 vs. 25.5%, p = 0.023). However,
there were no signicant differences in the proportion
of patients receiving statins between the two groups
(36.2 vs. 28.8, p = 0.222).There were 18.8% patients
in the insulin-treated group and 39.9% in the non-in-
sulin-treated group on oral antidiabetics (p = 0.001).
There were no statistically signicant differences regar-
ding the type of ACS between the two groups (Table 1).
Table 1. Comparison of baseline characteristics between diabetics
previously under insulin and non-insulin-treated diabetics
Previous
insulin
No previous
insulin p
Total number of patients 69 306
Demographic data
Male gender (%) 47/69 (68.1) 205/306 (67.0) 0.858
Mean age (years) (SD) 69.0 ± 10.0 70.0 ± 10.0 0.306
Type of ACS (%)
STEMI 17/69 (24.6) 98/306 (32.0) 0.229
NSTEMI 41/69 (59.4) 164/306 (53.6) 0.380
UA 11/69 (15.9) 44/306 (14.4) 0.740
Cardiovascular risk factors
Hypertension (%) 57/67 (85.1) 250/295 (84.7) 0.946
Dyslipidemia (%) 57/67 (85.1) 248/293 (84.6) 0.929
Smoking (%) 6/68 (8.8) 32/306 (10.5) 0.687
Stress (%) 14/68 (20.6) 43/306 (14.1) 0.175
Family History of CAD (%) 10/68 (14.7) 33/306 (10.8) 0.359
BMI (Kg/m2) 29.9 ± 6.9 28.5 ± 5.0 0.154
Cardiovascular history (%)
Prior myocardial infarction 22/57 (38.6) 53/262 (20.2) 0.003
Prior PCI 12/62 (19.4) 33/295 (11.2) 0.078
CABG 8/67 (11.9) 17/293 (5.8) 0.105
Previous heart failure 1/25 (4.0) 3/136 (2.2) 0.494
Prior stroke 12/69 (17.4) 28/304 (9.2) 0.047
PVD 9/69 (13.0) 11/304 (3.6) 0.005
STEMI: ST elevation myocardial infarction; NSTEMI: non-ST elevation myocardial infarction;
UA: unstable angina; BMI: body mass index; PCI: percutaneous coronary intervention; CABG:
coronary artery bypass graft; PVD: peripheral vascular disease.
For the hemodynamic parameters, the previously
insulin-treated diabetics were less often in Killip class
I at admission, presented more frequently LBBB and
tended to have a lower left ventricular ejection fraction
(LVEF) (Table 2).
Concerning laboratory parameters, diabetics in the
insulin-treated group had signicantly lower total and
LDL cholesterol. In these patients we found signi-
cantly higher admission glycemia, fasting glycemia and
glycosylated hemoglobin (HbA1c), signicantly lower
levels of hemoglobin and a trend toward worse glome-
rular ltration rate (GFR - calculated using Cockroft-
Gault formula)(Table 2).
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Arq Bras Endocrinol Metab. 2010;54/7
Table 2. Hemodynamic, electrocardiographic and laboratorial data
Global population Previous insulin No previous insulin p
Hemodynamic data
Heart rate, bpm (SD) 80.0 ± 16.0 81.0 ± 18.0 80.0 ± 16.9 0.569
Systolic blood pressure (mmHg) (SD) 143.0 ± 26.0 145.0 ± 29.0 142.0 ± 26.0 0.485
Diastolic blood pressure (mmHg) (SD) 75.0 ± 14.0 72.0 ± 14.4 75.0 ± 14.0 0.101
Killip Class I at admission (%) 287/368 (78.0) 43/67 (64.2) 244/301 (81.1) 0.003
Killip Class II at admission (%) 70/368 (19.0) 20/67 (29.9) 50/301 (16.6) 0.013
Killip Class III at admission (%) 7/368 (1.9) 3/67 (4.5) 4/301 (1.3) 0.117
Killip Class IV at admission (%) 4/368 (1.1) 1/67 (1.5) 3/301 (1.0) 0.554
LVEF (%) (SD) 50.0 ± 11.0 48.0 ± 12.0 50.0 ± 11.0 0.145
Electrocardiographic data (%)
Synusal rhythm 321/373 (86.1) 59/69 (85.5) 262/304 (86.2) 0.883
Atrial fibrillation 43/373 (11.5) 9/69 (13.0) 34/30 (11.2) 0.662
LBBB 10/373 (2.7) 5/69 (7.2) 5/304 (1.6) 0.022
Laboratorial parameters
Peak TI (mg/L) (SD) 11.0 ± 29.4 10.5 ± 28.4 11.1 ± 30.8 0.764
Peak CK-MB mass (mg/L) (SD) 36.7 ± 110.8 36.0 ± 111.6 37.0 ± 108.0 0.863
Triglycerides (mg/dL) (SD) 175.4 ± 93.0 142.0 ± 72.0 148.0 ± 104.0 0.663
Total cholesterol (mg/dL) (SD) 181.0 ± 64.0 165.0 ± 61.0 183.0 ± 66.0 0.017
LDL cholesterol (mg/dL) (SD) 124.0 ± 46.0 108.0 ± 52.0 126.0 ± 45.0 0.003
HDL cholesterol (mg/dL) (SD) 41.0 ± 11.0 40.0 ± 10.0 42.0 ± 11.0 0.230
Apoprotein B (mg/dL) (SD) 99.0 ± 35.8 91.0 ± 38.5 100.0 ± 35.2 0.077
GFR (mL/min) (SD) 61.7 ± 21.9 56.8 ± 23.7 62.8 ± 21.4 0.083
Admission glycemia (mg/dL) (SD) 169.0 ± 73.0 218.0 ± 108.0 164.0 ± 64.0 < 0.001
Fasting glycemia (mg/dL) (SD) 153.0 ± 58.3 181.0 ± 92.0 146.0 ± 51.0 < 0.001
HbA1c (%) (SD) 6.5 ± 2.0 8.1 ± 2.7 6.4 ± 1.5 0.007
Baseline hemoglobin (g/dL) (SD) 13.6 ± 1.9 13.0 ± 2.2 13.7 ± 1.8 0.016
LVEF: left ventricular ejection fraction; LBBB: left bundle-branch block; TI: troponin I; GFR: glomerular filtration rate; HbA1c: glycosylated hemoglobin.
Therapeutic approach
Patients underwent an invasive strategy in 53.6% of ca-
ses, with PCI in 117 patients (31.2% of global popula-
tion).In 72 patients (19.2% of the total population and
62.6% of patients with STEMI), primary angioplasty
was performed. Of the 201 patients who underwent
coronary angiography, 29 (14.4%) had anatomically
normal coronary arteries.Diabetic patients under chro-
nic insulin therapy were less frequently submitted to an
early invasive approach compared to patients receiving
oral antidiabetics or without any prior antidiabetic the-
rapy (36.2% vs. 57.5%, p = 0.001)(Table 3).
Regarding coronary anatomy, diabetic patients
under previous insulin therapy showed more often
three-vessel disease and left anterior descending artery
lesions, but these differences were not statistically sig-
nicant(Table 3).
Concerning medical treatment in the rst 24 hours
of hospitalization, most patients in the general popu-
lation were treated with aspirin (95.7%), β-blockers
(76.5%), ACEI (94.1%), statins (98.1%) and low mo-
lecular weight heparin (LMWH) (97.1%). In 41.6% of
cases there was the need for diuretics in the rst 24
hours of hospitalization. There were no statistically
signicant differences in the use of these drugs among
insulin-treated and non-insulin-treated patients, with
the exception of diuretics, which were used more fre-
quently in the insulin-treated group (59.4% vs. 37.6%,
p = 0.001).
At the time of hospital discharge, the most prescri-
bed drugs were, in descending order, statins (95.5%),
ACE inhibitors (89.1%), aspirin (87.7%) and β-blockers
(76.5%), with no statistically signicant differences be-
tween the two groups.
Insulin and acute coronary syndromes
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Arq Bras Endocrinol Metab. 2010;54/7
Table 3. Catherization lab data
Global population Previous insulin No previous insulin p
Catheterization during hospitalization (%) 201/375 (53.6) 25/69 (36.2) 176/306 (57.5) 0.001
Normal coronaries (%) 29/201 (14.4) 1/25 (4.0) 28/176 (15.9) 0.137
3-vessel disease (%) 62/201 (30.8) 9/25 (36.0) 53/176 (30.1) 0.551
2-vessel disease (%) 39/201 (19.4) 4/25 (16.0) 35/176 (19.9) 0.791
1-vessel disease (%) 68/201 (33.8) 11/25 (44.0) 57/176 (32.4) 0.251
Left main disease (%) 9/201 (4.5) 0/25 (0.0) 9/176 (5.1) 0.605
LAD disease (%) 134/201 (66.7) 20/25 (80.0) 114/176 (64.8) 0.131
Complete revascularization (%) 73/172 (42.4) 10/24 (41.7) 63/148 (42.6) 0.934
Non-revascularizable (%) 55/172 (32) 8/24 (33.3) 47/148 (31.8) 0.878
LAD: left anterior descending coronary artery.
In-hospital outcomes
The mean hospital length of stay was 6.0 ± 3.0 days
with no statistically signicant differences between the
two groups (5.0 ± 3.0 days in the insulin-treated vs. 6.0
± 3.0 days in thenon-insulin-treated group, p = 0.700).
The pre-specied in-hospital complications rate was
7.9% and the in-hospital mortality rate 6.4%. There was
no statistically signicant differences in in-hospital com-
plications or in-hospital mortality rates among insulin-
treated and non-insulin-treated patients (10.1% vs. 7.3%,
p = 0.360 and 10.1% vs.5.6%, p = 0.174, respectively).
Post-discharge outcomes – 1 year follow-up
The overall 1-year mortality rate was 11.7% and that of
MACE 24.5%, without statistically signicant differen-
ces between the two groups (18.2% vs. 10.4%, p = 0.103
No Previous Insulin
Previous Insulin Therapy
Censored
Censored
and 32.1% vs. 23.0%, p = 0.146, respectively). The sur-
vival curves showed similar evolution of the two diabetic
groups during the 1-year follow-up(Figures 1 and 2).
In the Cox regression, the independent predictors
of overall 1-year mortality were Killip class on admis-
sion > I, total cholesterol > 230 mg/dL and heart rate
on admission > 101 bpm(Table 4).
Regarding independent predictors of MACE occur-
rence during the rst year after the ACS, the multiva-
riate analysis identied the following predictors: LDL
cholesterol > 113 mg/dL, total cholesterol > 180 mg/dL
and GFR < 64 mL/min. By contrast, female gender
was associated with a reduction of 64% in relative risk
of 1-year MACE (Table 5).
Prior insulin therapy was not found to be neither
an independent predictor of overall mortality nor of
MACE, over one year.
p = 0.105
Follow-up (days)
Cumulative Survival
1.0
0.8
0.6
0.4
0.2
0.0
0 100 200 300 400
Figure 1. Cumulative survival curves.
Insulin and acute coronary syndromes
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Arq Bras Endocrinol Metab. 2010;54/7
No Previous Insulin
Previous Insulin Therapy
Censored
Censored
p = 0.135
Follow-up (days)
MACE-free survival
1.0
0.8
0.6
0.4
0.2
0.0
0 100 200 300 400
Figure 2. MACE-free survival curves.
Table 4. Independent predictors of 1-year mortality
HR CI 95% p
HR > 101 bpm 9.24 3.76 – 22.70 < 0.001
Killip class on admission > I 3.71 1.69 – 8.14 0.001
Total cholesterol > 230 mg/dL 3.45 1.53 – 7.75 0.003
Previous insulin therapy 1.75 0.69 – 4.42 0.235
HR: heart rate; bpm: beats per minute.
Table 5. Independent predictors of MACE during the first year after
the ACS
HR CI 95% p
LDL cholesterol > 113 mg/dL 2.36 1.27 – 4.38 0.007
GFR < 64 mL/min 2.02 1.18 – 3.48 0.011
Total cholesterol > 180 mg/dL 1.83 1.05 – 3.20 0.034
Female gender 0.36 0.19 – 0.70 0.003
Previous insulin therapy 1.64 0.86 – 3.10 0.132
Age > 80 years 2.04 0.98 – 4.24 0.057
ACS: acute coronary syndrome; GFR: glomerular filtration rate.
DISCUSSION
After an ACS, diabetic patients have a considerably po-
orer prognosis in the short and long term than their
non-diabetic counterparts (3,4,12). The “Euro He-
art Survey on Diabetes and the Heart” showed that
either previously known DM or newly diagnosed DM
are associated with a particularly high risk of death and
cardiovascular events during the rst year of clinical
follow-up (13). On the other hand, hyperglycemia on
admission has been associated with decreased survi-
val after an ACS, either in diabetics or non-diabetics
(14,15). Recently, it has been demonstrated that per-
sistent hyperglycemia during hospitalization for ACS
was a better predictor of in-hospital mortality than
admission glycemia (16). However, is not completely
clear whether this decreased survival is related to the
development of hyperglycemia in response to stress or
whether it is related to a worse prior metabolic control
(15,17).
Besides the well-known benet of insulin in the
metabolic control of diabetic patients, some resear-
chers also propose the existence of a cardioprotective
action. Recent studies have shown that insulin exerts
anti-inammatory and anti-atherogenic effects and im-
proves endothelial function (18-21).
In the past decade it has become evident that the
endothelium is not a simple barrier. Nowadays, the en-
dothelium is viewed as a complex organ, with autocrine
and paracrine function, constituting a rst line physio-
logical defense against atherosclerosis (6).
The metabolic abnormalities of diabetes are associa-
ted with endothelial dysfunction.Diabetes induces oxi-
dative and inammatory stress, vasoconstrictor respon-
ses, thrombotic phenomena and pro-apoptotic effects
on endothelial cells (22).
Insulin and acute coronary syndromes
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Arq Bras Endocrinol Metab. 2010;54/7
Insulin appears to exert multiple benecial effects
on endothelial cells, platelet and leukocyte function,
which could be potentially cardioprotective and anti-
atherosclerotic (23-25).
Several mechanisms have been proposed to explain
the benecial effect of insulin on endothelial function:
1) reduction of serum glucose, triglycerides and free
fatty acids (which have been associated with endothelial
dysfunction) (26,27), 2) endothelium-independent va-
sodilatation(which seems to increase signicantly with
insulin therapy), 3) reduction of oxidative stress (28),
4) stimulation of nitric oxide production in endothelial
cells (29) and 5) stimulation of endothelial progenitor
cells via the activation of the receptor for insulin growth
factor type 1 (IGF-1).In turn, endothelial progenitor
cells have the ability to improve function of injured ves-
sels by stimulating re-endothelialization and neovascu-
larization (29).
However, there are some studies that suggest op-
posite effects, stating that insulin therapy is associated
with increased vascular resistance, ventricular hypertro-
phy and endothelial dysfunction (1,10).
In this work it was found that prior insulin therapy
did not independently increase the overall mortality or
the incidence of major adverse cardiac events in the rst
year after an ACS.
In our diabetic population there was a high rate of
adherence to the pharmacological therapy approach ad-
vocated in acute coronary syndromes. In fact, the use
of the generality of the drugs recommended in the con-
text of ACS was far superior compared to international
multicenter studies (13,30).
An early invasive strategy was used in most patients,
but less frequently in diabetics under prior insulin the-
rapy. One possible explanation for this is that some
insulin-treated diabetics had previously known severe,
diffuse, non-revascularizable CAD.
The fact that there were no statistically signicant
differences in the type of ACS or in the levels of bio-
chemical markers of myocardial necrosis between the
two groups, suggests that prior antidiabetic therapy
does not inuence the type of ACS or the extent of
myocardial necrosis.
The higher prevalence of PAD and of prior stroke/
TIA in the insulin-treated group probably reects a
more advanced form of atherosclerosis, involving mul-
tiple arterial territories.However, despite this and the
lower use of an invasive strategy, the overall mortality
and the occurrence of MACE during the rst year after
the ACS in insulin-treated patients were similar to that
of non-insulin-treated patients.Therefore, prior insulin
therapy did not independently increase the overall mor-
tality or the incidence of major adverse cardiac events in
the rst year after the ACS.
CONCLUSIONS
This work suggests that the worst prognosis of insulin-
treated diabetics reported in other studies is not an inde-
pendent effect of insulin and probably it can be explai-
ned by demographic, clinical or therapeutic differences.
Moreover, it is possible that insulin therapy protects
diabetic patients from the diabetics patients from the
expected poor adverse outcome of an advanced athe-
rosclerotic disease.It would therefore be important to
conduct prospective studies to evaluate the effects of
insulin on endothelial function, seeking to understand
the pathophysiological mechanisms involved and to
investigate the real impact of insulin therapy in CAD
progression.
Study limitations
The size of the cohort and the number of clinical events
upon which we base our conclusions are, by compari-
son to the data accumulated in acute coronary syndro-
mes and diabetes, relatively small. However, our cohort
was unselected in terms of cardiovascular risk factors,
age, gender and treatment and is in fact a real popula-
tion seen in standard clinical practice.
We recognize that one important limitation of this
study is the lack of information about diabetes dura-
tion, which may be signicantly longer in previously
insulin-treated diabetics and could be associated to a
more diffuse atherosclerotic disease.
Acknowledgement: Statistical analysis was performed by the Na-
tional Center for Data Collection in Cardiology (CNCDC), a
body of the Portuguese Society of Cardiology.
Disclosure: no potential conict of interest relevant to this article
was reported.
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Insulin and acute coronary syndromes
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  • [Show abstract] [Hide abstract] ABSTRACT: Objective: Type 2 diabetes mellitus is a clear prognostic marker for increased cardiovascular morbidity and mortality after acute myocardial infarction (AMI). We compared diabetes patients based on therapy used (no pharmacotherapy, those prescribed oral antihyperglycemic agents and those prescribed insulin) on the composite risk of recurrent AMI, congestive heart failure and mortality among elderly patients with AMI. Methods: Using administrative data, we identified patients, aged 65 years and older, with an incident AMI hospitalization in British Columbia and the Calgary Health Region between April 1, 1995, and March 31, 2002, for a retrospective cohort study. Cox proportional hazard models were constructed to compare time to reach the composite outcome in the treatment groups. Results: Among 22 499 patients with AMI, 5158 patients had diabetes. Women comprised 43.2% of the diabetes cohort. For the composite outcome, there was a stepwise increase in the occurrence based on medication use: no diabetes (23.55 events per 100 person-years); diabetes but no treatment (31.70 per 100 person-years); oral agents only (36.34 per 100 person-years) and insulin therapy (49.43 per 100 person-years). After adjustment, relative to patients without diabetes, no treatment (hazard ratio 1.37, 95% confidence interval, 1.22 to 1.53), oral agents only (hazard ratio 1.43, 95% confidence interval, 1.31 to 1.56) and insulin therapy (hazard ratio 1.65, 95% confidence interval, 1.48 to 1.84) were all associated with an increased risk of the outcome developing. Conclusions: Diabetes conferred a significant risk increase in a combination of cardiovascular events after AMI. The risk existed even for diabetes patients not prescribed therapy and showed a progressive trend as the intensity of treatment advanced toward insulin.
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