JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY
VOL. 65, NO. 16, 2015
ª 2015 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION
PUBLISHED BY ELSEVIER INC.
ISSN 0735-1097/$36.00
http://dx.doi.org/10.1016/j.jacc.2015.02.053
EDITORIAL COMMENT
Impact of Type 1 and 2 Diabetes Mellitus
on Long-Term Outcomes After CABG*
David P. Taggart, MD, PHD
I
t is well-established both that the prevalence of
dependent DM and 6,581 patients with no DM
diabetes mellitus (DM) is rising rapidly in the
(p < 0.0001) (5). Furthermore, freedom from cardiac-
developed world and that its presence is a signif-
related death was similar for patients with non–
icant risk factor for cardiovascular disease and death
insulin-dependent DM and non-DM patients up to
(1). Over the last decade, it also has become increas-
6 years (p ¼ 0.08) after surgery and was, counterin-
ingly clear that for patients with diabetes who require
tuitively, significantly lower thereafter (p ¼ 0.004).
coronary artery revascularization, in addition to
optimal medical therapy, that the results of coronary
SEE PAGE 1644
artery bypass grafting (CABG) are superior to percuta-
In this issue of the Journal, Holzmann et al. (6)
neous coronary intervention in terms of significant
address the impact of the presence of type 1 or type
reductions in mortality, myocardial infarction, and
2 DM on long-term outcomes after CABG. Type 1 DM
the need for repeat interventions but at the cost of a
was defined as onset ay age <30 years and treated
slightly increased risk of stroke (2,3).
only with insulin, whereas type 2 DM was defined as
Currently, at least one-quarter of patients under-
treatment only with diet or oral hypoglycemic agents
going CABG in developed countries have diabetes,
alone, or in patients age $40 years at onset and
with a far higher incidence in Asian countries. How-
treated either with insulin alone or additionally with
ever, most previous studies addressing the impact of
oral hypoglycemic agents. Using 4 national Swedish
diabetes on outcomes after CABG have only consid-
Registries, in which individual patients have a unique
ered its absolute presence or absence without classi-
personal identity number, the authors followed the
fication as to whether it was type 1 or type 2 DM. And
outcome of primary isolated CABG in >39,000 pa-
what little information does exist has presented a
tients, between 2003 and 2013, of whom 725 (1.8%)
conflicting picture. One study reported that although
had type 1 DM and 8,208 had type 2 DM (21%). The
DM was a predictor of early death after CABG in 767
underlying premise for investigating potential dif-
patients with DM (of whom only 22% were insulin
ferences in outcomes is the differing pathophysiology
dependent) compared with 2,593 non-DM patients,
of type 1 and type 2 DM. Although the former is an
operated on between 1988 and 1999, DM had no
autoimmune disease that destroys insulin-producing
adverse impact on subsequent 5-year survival (4). By
cells in the pancreas and has a relatively early age of
contrast, a single center study of 9,125 survivors of
onset, the latter tends to occur in older patients and is
isolated CABG surgery between 1992 and 2002
characterized by insulin resistance and obesity.
reported lower cardiac-specific survival at 5 and
And indeed, there were striking differences in
10 years in 735 patients with insulin-dependent DM,
baseline characteristics in the 2 populations with DM.
in comparison to 1,809 patients with noninsulin-
In contrast to patients with type 2 DM, those with
type 1 DM were younger by around 8 years, had a
much greater duration of DM (41 years vs. 10 years),
were more likely to be female (42% vs. 23%) and had a
*Editorials published in the Journal of the American College of Cardiology
reflect the views of the authors and do not necessarily represent the
views of JACC or the American College of Cardiology.
From the Department of Cardiac Surgery, Oxford University Hospitals
higher incidence of end-stage renal failure (15% vs.
2.7%), peripheral vascular disease (24% vs. 13%), and
heart failure (16.4% vs. 13%). But importantly, there
Trust, Oxford, United Kingdom. Dr. Taggert has reported that he has no
were no significant clinical differences in body mass
relationships relevant to the contents of this paper to disclose.
index, prior PCI, myocardial infarction, stroke, and
1654
Taggart
JACC VOL. 65, NO. 16, 2015
APRIL 28, 2015:1653–4
Long-Term CABG Outcomes in Diabetes
atrial fibrillation. Overall, left ventricular ejection
of type 1 and type 2 DM on long-term outcomes
fraction defined as good (>50%), moderate (30% to
after CABG. The other obvious strengths of the cur-
50%) or impaired (<30%) was fairly similar amongst
rent study are the use of contemporary national reg-
the 3 groups. Glycemic control was also poorer in
isters that provide virtually complete cover of a
type 1 DM, with consistently higher levels of hemo-
country and with relatively little missing data. As
globin A1c. In terms of surgical risk, the 3 groups
such, the results could be confidently applied to pa-
were similar, with mean Euro scores of around 4.
The key findings of this registry were that patients
tients with DM undergoing CABG in similar developed
healthcare systems. And the main message of the
with type 1 DM had an approximate 2-fold increase in
study is that the “low-hanging fruit” is the need to
the risk of death at a mean follow-up of almost 6
focus on both the increased incidence of cardiovas-
years, whereas the mortality risk in those with type 2
cular and noncardiovascular deaths in patients with
DM was similar to that of the nondiabetic general
type 1 DM.
population. This translated into clinically important
Although the authors are to be congratulated on an
differences in age-adjusted 10-year survival being
excellent and comprehensive analysis of their na-
around 80% for those without DM or type 2 DM but
tional databases, there are 2 caveats. The first is that
only around 40% for those with type 1 DM. For pa-
there appears to be no effort to compare outcomes in
tients with type 1 DM, there was a significant increase
patients with DM and multivessel coronary artery
in the hazard ratio for both cardiovascular and non-
disease who received stents rather than surgery.
cardiovascular deaths in comparison to type 2 DM,
The second is the relatively poor quality of CABG
but not for repeat revascularization.
in a society with an advanced healthcare system.
In comparison to non-DM patients, for type 1 DM,
Although around 95% of patients received a single
the adjusted hazard ratio for death according to sex
internal mammary artery, fewer than 5% of patients
was relatively similar between men and women (1.8
received a second arterial graft despite strong cir-
vs. 2.17), whereas for type 2 DM, the respective figures
cumstantial evidence to support such a policy and
were 1.09 and 1.18. Similar findings were observed for
particularly in patients with DM (7).
the risk of death and MACE being approximately
double for type 1 DM in comparison to non-DM
REPRINT REQUESTS AND CORRESPONDENCE: Dr.
patients that was also similar to the type 2 DM
David P. Taggart, Department of Cardiac Surgery,
population.
Oxford University Hospitals Trust, Headley Way,
The current study is easily the most definitive
in terms of size to address the issue of the impact
Headington, Oxford OX3 9DU, United Kingdom.
E-mail: [email protected].
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KEY WORDS isolated CABG, major adverse
coronary event, prognosis, revascularization