(Circulation. 1995;92:1731-1736.)
© 1995 American Heart Association, Inc.
Articles |
From the Department of Internal Medicine, Section on Cardiology, Ochsner Clinic and Alton Ochsner Medical Foundation, New Orleans, La, and Invasive Cardiology (C.J.W.), HCI Medical Center, Clydebank, Scotland.
Correspondence to Christopher J. White, MD, Director of Invasive Cardiology, HCI Medical Center, Beardmore St, Clydebank, Scotland, G81 4HX.
| Abstract |
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Methods and Results Percutaneous coronary angioscopy was performed in 55 consecutive patients with unstable angina. We observed plaque color, texture, and the incidence of intracoronary thrombus associated with the culprit lesions of these patients. The population consisted of 17 (31%) diabetic and 38 (69%) nondiabetic patients. The presence of coronary risk factors was not significantly different between the two populations. Ulcerated plaque was found in 16 of 17 (94%) diabetic patients versus 23 of 38 (60%) nondiabetic patients (P=.01). Intracoronary thrombi were seen in 16 of 17 (94%) diabetic patients versus 21 of 38 (55%) nondiabetic patients (P=.004).
Conclusions The results of the angioscopic examination show that diabetic patients with unstable angina have a higher incidence of plaque ulceration and intracoronary thrombus formation than nondiabetic patients. This increased frequency of complex lesion morphology is consistent with the disproportionately higher risk for development of acute coronary syndromes in these patients.
Key Words: diabetes mellitus angina angioscopy plaque
| Introduction |
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The cause of this difference in the diabetic population is not well understood. The increased incidence of myocardial infarction may simply reflect the higher prevalence of significant coronary artery disease. However, diabetic patients have several hematologic, rheologic, and metabolic abnormalities not present in their nondiabetic counterparts7 8 9 10 11 12 13 14 that may predispose them to plaque disruption and thrombus formation and lead to the development of unstable coronary syndromes.
To date, very few studies, all of which have been postmortem studies, have attempted to explain these differences between diabetic and nondiabetic patients. Our study is the first to analyze differences in plaque morphology between diabetic and nondiabetic patients in vivo with the use of coronary angioscopy in a cohort of unstable angina patients.
| Methods |
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Coronary Angiography and Culprit Lesion
Assessment
Coronary angiography was performed in every patient
before angioscopy and angioplasty with the use of standard catheters
and techniques. Each coronary artery was selectively viewed in
multiple projections. In cases of significant single-vessel
disease, this lesion was considered to be the culprit lesion. In cases
of multivessel disease, the culprit lesion was identified by one of the
following criteria: ST-T changes on ECGs obtained during anginal
episodes at rest in the territory of a vessel with a significant
stenosis (greater than 70%); significant segmental wall motion
abnormalities in the left ventriculogram in the distribution of a
vessel with a significant stenosis; or the presence of an
Ambrose type II eccentric lesion.16
Coronary Angioscopy Assessment
The coronary angioscopic
procedure has been
described elsewhere.17 Briefly, we used a standard
coronary angioplasty technique in which the stenotic
lesion was crossed with the 0.014-in guide wire. The angioscope
(Imagecath, Baxter Healthcare) then was advanced over the guide wire
under fluoroscopic guidance so that the distal tip marker on the
angioscope was located proximal to the target lesion but did not come
into contact with the lesion. The angioscope occlusion balloon then was
inflated with low pressure (1 to 2 atm). After balloon inflation,
warmed lactated Ringer's solution (0.5 to 1.0 mL/s) was infused
through the distal port to create a blood-free field during
viewing. Angioscopic images were recorded on videotape for
immediate review and archiving. Guiding catheter pressure, ST segment
changes, cardiac rhythm, and patient comfort were monitored
continuously during angioscopy.
Assessment of Other Clinical Variables
Other clinical
variables assessed included age, sex,
treatment received before and at admission, and time elapsed since the
patient arrived until the procedure was performed. Coronary
risk factors, including hypertension, tobacco use, and
hypercholesterolemia, also were noted. All of
the patients had at least one cholesterol test some time
during the previous 3 months. All the smokers consumed at least 10
cigarettes per day. The diagnosis of diabetes mellitus and diabetic
neuropathy were made according to established
criteria.18 19 The activity level was assessed in
each
patient with use of the New York Heart Association functional
classification.
Data Analysis
The coronary angioscopic findings were reviewed
by two
interventional cardiologists with extensive angioscopy experience who
were blinded to the clinical and angiographic status of the patients.
Atheromatous plaque was defined as raised yellow or
white material within the arterial lumen. The surface
texture of the plaque was determined to be either smooth or rough. The
presence of ulceration was defined as an atheromatous
plaque with an irregular, ragged surface (Fig 1
). We
defined thrombus as a collection of red, solid material adherent to the
luminal surface despite flushing (Fig 2
). The
angioscopic end points were differences between diabetic and
nondiabetic patients in plaque color, surface texture, presence of
ulceration, and presence of intracoronary thrombus.
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Data are expressed as mean values±1 SD. Comparisons between the groups for continuous variables were performed using a two-tailed unpaired Student's t test and for discrete variables using Fisher's exact test. A value of P<.05 was considered significant.
| Results |
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The mean duration of diabetes mellitus was 8.2±8.9 years (range, 2
months to 35 years). Four (23%) patients had diabetic
neuropathy (one patient had peripheral, two
patients had peripheral and autonomic, and one patient had
autonomic neuropathy; see Table 3
). The four
patients with diabetic neuropathy had had diabetes mellitus
for more than 18 years.
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The prevalence of coronary artery disease (more than 50%
diameter stenosis) and culprit lesion location are described in
Table 4
. Diabetic patients had a higher prevalence of
three-vessel disease (47% versus 31%) and lower prevalence of
single-vessel disease (18% versus 32%) than nondiabetic patients,
although these differences were not statistically significant. Although
the culprit lesion was more frequently located in a saphenous vein
graft in diabetic patients, this difference was not significant (35%
versus 19%, P=.18).
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The angioscopic characteristics of both groups are described in Table
5
. Yellow plaque was found in 88% of diabetic patients
and 84% of nondiabetic patients. Roughness of the plaque surface was
somewhat more frequent in diabetic patients than in nondiabetic
patients (88% versus 68%), but this difference was not statistically
significant. Plaque ulceration was found in 16 of 17 (94%) diabetic
patients compared with 23 of 38 (60%) nondiabetic patients
(P=.01). Intracoronary thrombi were seen in 16
of 17 (94%) diabetic patients versus 21 of 38 (55%) nondiabetic
patients (P=.004).
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| Discussion |
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Whether or not coronary atherosclerosis is more diffuse in diabetic patients is controversial.4 28 In the autopsy study of Waller and coworkers,4 the diabetic patients had more severe stenoses, but there was no difference in other arterial segments when compared with nondiabetic patients. However, in another autopsy study by Crall and Roberts,29 more extensive and diffuse coronary artery disease was found in diabetic patients.
Incidence of Myocardial Infarction
The relative risk of
myocardial infarction is 50% greater in
diabetic men and 150% greater in diabetic women, and myocardial
infarction may be the cause of death in up to 30% of diabetic
patients.5 6 The cause of this increased incidence of
myocardial infarction among diabetic patients is not clear. In part, it
may be a reflection of the higher prevalence of coronary artery
disease in this population. Nevertheless, diabetic patients have
significant abnormalities in their hematologic, rheologic, and
metabolic systems that may increase their risk for
myocardial infarction.
Hematologic, Rheologic, and Metabolic
Abnormalities
Platelet aggregation, an essential step in occlusive
thrombus formation, is enhanced in diabetic
patients.9 10 11 12 13 14 30 31
Furthermore, platelet
consumption is higher in diabetic patients, and
ß-thromboglobulin and platelet factor 4, two
platelet-specific proteins thought to reflect in vivo
platelet activation, are elevated in these
patients.7 30 Plasma fibrinogen levels also are
increased
in diabetic patients30 32 and have been shown to
correlate
with myocardial infarction and sudden death in this
population.9
There are other conditions in diabetic patients that may increase their risk of a cardiac event. Procoagulant factors such as factor VIII and factor VIII ristocetin cofactor antigen and fibrinopeptide A, which reflect in vivo thrombosis, are elevated in diabetic patients.7 9 30 33 Endogenous fibrinolysis also has been found to be decreased in diabetic patients,30 32 33 whereas endothelial damage in patients with diabetes results in deficient production of prostacyclin.30 34 35 36
Rheologic abnormalities include high levels of plasma proteins, which increase red cell aggregation and lead to decreased red cell deformability.7 8 Diabetic patients also have elevated plasma and whole blood viscosity, which increase shear forces, thereby increasing the likelihood of plaque rupture.8 37
Among the multiple biochemical abnormalities produced by diabetes mellitus is the formation of protein-linked advanced glycosylation end products such as low-density lipoproteins.38 39 40 High levels of advanced glycosylation end products have been found within the atherosclerotic plaque in diabetic patients.41 Advanced glycosylation end products also may induce an inflammatory reaction by promoting cytokine release and monocyte chemotaxis.42 Previous studies have shown that atherosclerotic plaques rich in lipid-laden macrophages and extracellular lipids are more prone to rupture.43 In addition, inflammation may play a role in destabilizing the fibrous cap tissue of the atherosclerotic plaque and thus enhance the risk of rupture and thrombosis.44
Enhanced Development of Complex Plaques in Diabetics
In the
present study, the overall incidence of plaque
ulceration (71%) and intracoronary thrombi (67%) are in
agreement with previous angioscopic and postmortem studies in unstable
angina patients.45 46 47 48
When we divided the population
between diabetic and nondiabetic patients, we found a significantly
increased incidence of both plaque ulceration (94%) and thrombosis
(94%) in diabetic patients as compared with 60% and 55%,
respectively, for nondiabetic patients (Table 5
).
To our knowledge, no comparative information exists regarding the in vivo differences in plaque morphology of unstable angina patients with or without diabetes mellitus. However, there does appear to be an association between diabetes mellitus and coronary ischemic syndromes in which the development of complex plaque morphology is very frequently implicated.49 50
In a postmortem study of 168 patients with sudden ischemic death, Davies et al51 found that patients with diabetes or hypertension or both appeared to have a greater number of fissured atherosclerotic plaques than persons without diabetes. Jacoby and Nesto52 suggested that diabetes is associated with an increased tendency for both atherosclerotic plaque formation and intraluminal thrombosis, which may increase the propensity to develop myocardial infarction. Several studies have determined that the major factor precipitating coronary thrombosis is plaque rupture,53 54 55 56 which is more common in diabetic and hypertensive patients.51
Comparability of Groups
In the present study, the clinical
characteristics and
coronary risk factors were comparable between the two groups.
Although not statistically significant, the culprit lesion was located
in a saphenous vein graft more frequently in diabetic patients than in
nondiabetic patients. It is unlikely, however, that this small
difference explains the significantly higher incidence of thrombosis
and ulceration found in diabetic patients, since there is evidence in
the literature suggesting no differences regarding frequency of complex
plaque morphology during unstable angina between native
coronary arteries and saphenous vein
grafts.46 47 48 57 58 59
Finally, although our two populations were homogeneous in terms of their premorbid activity level and unstable angina classification, it is possible that some of our diabetic patients may have presented at a more advanced stage of coronary ischemia than the nondiabetic patients. Diabetic patients may have a blunted awareness of ischemic chest pain or may become aware of their symptoms later in the course of myocardial ischemia, which could lead to an increased incidence of complex plaque morphology at the time of their initial presentation.60
Conclusions
The present study is the first to report a
significant
difference in the incidence of complex plaque morphology between
diabetic and nondiabetic patients with unstable angina. The overall
incidence of plaque ulceration and thrombus formation was similar to
previous studies, but when we divided the population between diabetic
and nondiabetic patients, we found a significantly increased incidence
of both plaque ulceration and intracoronary thrombus in
diabetic patients. It is possible that the metabolic,
hematologic, and rheologic abnormalities present in diabetic
patients may predispose their atherosclerotic plaque to be less stable,
more prone to disruption and ulceration, and to develop
intracoronary thrombus. This would increase the likelihood
that these patients would progress toward more severe stages of acute
coronary ischemia. This increased incidence of plaque
ulceration and thrombus formation is consistent with the
disproportionately higher incidence of acute coronary syndromes
in diabetic patients.
| Acknowledgments |
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Received January 25, 1995; revision received April 3, 1995; accepted May 3, 1995.
| References |
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