Silent coronary artery disease in patients with type 2 diabetes mellitus

Evaluation of Silent Myocardial Ischemia with Single-Photon Emission Computed Tomography/Computed Tomography in Asymptomatic Subjects with Diabetes and Pre-Diabetes

Objective:

The aim of this study was to disclose the prevalence of myocardial ischemia, as detected by adenosine stress myocardial perfusion imaging (MPI) with hybrid single-photon emission computed tomography/computed tomography (SPECT/CT), in asymptomatic diabetic and pre-diabetic patients and to find out whether ischemia predicted the occurrence of adverse cardiac/cerebrovascular events (ACCE) at follow-up.

Methods:

Forty-three diabetic and thirty-five pre-diabetic asymptomatic patients without any history of coronary artery disease, underwent MPI and were followed-up for a 12.8±2.2 (8-19) months for the occurrence of ACCE. Baseline variables that would predict the presence of ischemia and the value of ischemia on MPI for predicting the occurrence of ACCE at follow-up were evaluated by logistic regression analysis.

Results:

Ischemia was detected in ten (23.3%) of the diabetic and in four (11.4%) of the pre-diabetic patients. The presence of diabetes was the only independent predictor of myocardial ischemia [odds ratio (OR): 12.31, 95% confidence interval (CI): 1.83-82.66; p<0.01]. During 12.8±2.2 (8-19) months of follow-up, ACCE was observed in five out of 78 (6.4%) patients. Patients with ischemia were significantly more likely to have ACCE during follow-up as compared to those with normal MPI scans (event rates: 21.4% vs. 3.1%, OR: 8.455 95% CI: 1.264-56.562, p=0.038).

Conclusion:

Myocardial ischemia as detected by adenosine stress SPECT/CT in a population of asymptomatic patients with diabetes mellitus or pre-diabetes appeared to predict the occurrence of ACCE at follow-up.

Myocardial dysfunction and cardiovascular disease in type 2 diabetes

Type 2 diabetes mellitus (T2DM) is strongly associated with increased risk of myocardial dysfunction and cardiovascular disease (CVD), two separate conditions which often co-exist and influence each other's course. The prevalence of myocardial dysfunction may be as high as 75% in T2DM populations but is often overlooked due to the initial asymptomatic nature of the disease, complicating co-morbidities such as coronary artery disease (CAD) and obesity, and the lack of consensus on diagnostic criteria. More sensitive echocardiographic applications are furthermore needed to improve detection of early subclinical changes in myocardial function which do not affect conventional echocardiographic parameters. The pathophysiology of the diabetic myocardial dysfunction is not fully elucidated, but involves hyperglycemia and high levels of free fatty acids. It evolves over several years and increases the risk of developing overt HF, and is suggested to at least in part account for the worse outcome seen in T2DM individuals after cardiac events. CAD and stroke are the most frequent CV manifestations among T2DM patients and relate to a large degree to the accelerated atherosclerosis driven by inflammation. Diagnosing CAD is challenging due to the lower sensitivity inherent in the diagnostic tests and there is thus a need for new biomarkers to improve prediction and detection of CAD. It seems that a multi-factorial approach (i.e. targeting several CV risk factors simultaneously) is superior to a strict glucose lowering strategy in reducing risk for macrovascular events, and recent research may even support an effect also on HF outcomes.

The report of male gender and retinopathy status improves the current consensus guidelines for the screening of myocardial ischemia in asymptomatic type 2 diabetic patients

BACKGROUND AND AIMS

American Diabetes Association (ADA), French-speaking Societies for diabetes & cardiology (ALFEDIAM-SFC) and Cardiac Radionuclide Imaging (CRI) have proposed guidelines for the screening of silent myocardial ischemia (SMI). The aim of the study was to evaluate their diagnostic values and how to improve them.

METHODS AND RESULTS

731 consecutive type 2 diabetic patients with ≥1 additional risk factor were screened between 1992 and 2006 for SMI by stress myocardial scintigraphy and for silent coronary artery disease (CAD) by coronary angiography. A total of 215 (29.4%) patients had SMI, and 79 of them had CAD. ADA (Odds Ratio 1.7 [95% Confidence Interval: 1.2-2.5]; p < 0.05), ALFEDIAM-SFC (OR 1.5 [1.0-2.5], p < 0.05) and CRI criteria (OR 2.0 [1.4-2.8], p < 0.01) predicted SMI. Considering the presence of male gender and retinopathy added to the prediction of SMI allowed by ADA criteria (c statistic: area under the curve AROC 0.651 [0.605-0.697] versus 0.582 [0.534-0.630]), p < 0.01 and ALFEDIAM-SFC criteria (AROC 0.672 [0.620-0.719] versus 0.620 [0.571-0.670], p < 0.05). CRI prediction of SMI was improved by considering the presence of macroproteinuria and retinopathy (AROC 0.621 [0.575-0.667] versus 0.594 [0.548-0.641], p < 0.01). Severe retinopathy (OR 3.4 [1.2-9.4], p < 0.05), smoking habits (OR 2.1 [1.1-4.2], p < 0.05) and triglyceride levels (OR 1.3 [1.0-1.6], p < 0.05) were independent predictors of CAD in the patients with SMI.

CONCLUSION

Current guidelines criteria are able to predict SMI but prediction may be improved by considering male gender and the presence of retinopathy. CAD is more frequent in the patients with SMI who are current smokers, have severe retinopathy and higher triglyceride levels.

Osteoprotegerin, leptin and IL-6: association with silent myocardial ischemia in type 2 diabetes mellitus

BACKGROUND

Diabetic patients often exhibit severe, asymptomatic coronary artery disease (CAD). The relationship between osteoprotegerin (OPG), inflammatory markers and silent myocardial ischemia remains to be elucidated.

METHODS

We recruited 45 type 2 diabetic patients and 33 healthy controls and assessed them for silent myocardial ischemia (SMI) by myocardial perfusion imaging. Patient blood was tested for OPG, IL-6 and leptin concentrations.

RESULTS

OPG, leptin and IL-6 levels were found significantly elevated in diabetic patients (p < 0.001, p < 0.01, p < 0.05). Based on our classification of presence/absence of SMI in our diabetic group, we found that there was a significant association between SMI and the biomarkers IL-6 (p < 0.001), leptin (p < 0.001) and OPG (p < 0.05). In multivariate regression analyses, OPG was found to be significantly related to diabetes mellitus and to SMI. Age, sex and smoking increased the association between OPG and SMI.

CONCLUSION

High OPG, leptin and IL-6 levels are associated with the presence and severity of SMI in type 2 diabetic patients.

Waist circumference and metabolic syndrome: the risk for silent coronary artery disease in males

BACKGROUND

Waist circumference (WC) is a component used to define metabolic syndrome. However, its role as an independent predictor of silent coronary artery disease (CAD), above its contribution to metabolic syndrome, remains unknown.

METHODS

Male veterans without known CAD, undergoing cardiac stress testing for indications other than typical angina or its equivalent, were evaluated for the presence of silent CAD. High WC and metabolic syndrome were defined per the revised National Cholesterol Education Program (NCEP-R) and the International Diabetes Federation (IDF) criteria.

RESULTS

Data on 1,071 patients (age 61±11 years) were analyzed retrospectively. On multivariable logistic regression analysis [odds ratio (OR), 95% confidence interval (CI), P value), a WC ≥94 cm (1.42, 1.04-1.93; P=0.026), metabolic syndrome by NCEP-R (1.73, 1.29-2.33; P<0.0001), and metabolic syndrome by IDF (1.57, 1.17-2.11; P=0.003) were independent predictors of silent CAD. When comparing patients meeting criteria for metabolic syndrome defined by either NCEP-R or IDF, the prevalence of silent CAD was not statistically different (P=0.86). The prevalence of silent CAD associated with a high WC was not inferior to that seen between silent CAD and metabolic syndrome as defined by either criterion. Last, among patients with metabolic syndrome defined by NCEP-R, those with a high WC as a defining component of metabolic syndrome had a higher prevalence of silent CAD (30% vs. 20%; P=0.026).

CONCLUSION

A WC ≥94 cm in males is independently associated with an increased prevalence of silent CAD. In patients with metabolic syndrome, this prevalence is increased by the presence of high WC.

Silent myocardial infarction in women with type II diabetes mellitus and microalbuminuria

Introduction:

The aim of this study was to investigate whether asymptomatic women with diabetes mellitus (DM) without previous history of ischemic heart disease (IHD) and normal electrocardiogram (ECG) have suffered silent myocardial infarction (MI).

Methods:

The study population consisted of 64-years old women with DM and albuminuria (n = 15) and aged- and body mass index-matched controls (n = 16). The patients were selected after screening of 240 women with previously known or unknown DM. The individuals with previous history of IHD and ECG suggesting the presence of IHD were excluded. All subjects were investigated with magnetic resonance imaging (MRI).

Results:

MRI investigation has revealed the presence of subendocardial MI in the two DM women (13%). No MI was detected in the control group. MR coronary angiography detected the presence of significant stenosis in the proximal segment of left anterior descending (LAD) coronary artery in one DM woman. This patient developed unstable angina 1 week after the MRI investigation. The conventional angiography has confirmed the presence of significant stenosis in LAD demanding invasive revascularization by percutaneous coronary angioplasty. No difference was found in indices of left ventricular (LV) systolic function while diastolic function was disturbed in the DM group. There was a tendency for increased LV mass in the DM group. No difference was found in the LV volumes.

Conclusion:

Clinically significant proportion of the women with DM and albuminuria without previous history of IHD have had silent MI. MRI screening of these high risk female patient is valuable diagnostic tool which may increase diagnostic accuracy and improve prognosis in DM patients with IHD.

Myocardial perfusion scintigraphy in asymptomatic diabetic patients: a critical review

The increasing prevalence of diabetes mellitus and the associated high cardiovascular risk has made the non-invasive identification of silent coronary heart disease in diabetic individuals an important issue. This strategy could identify higher risk asymptomatic patients with diabetes mellitus in whom coronary revascularization may improve the outcome beyond that achieved by currently recommended medical management. Stress myocardial perfusion imaging has been shown to be effective in detecting coronary heart disease and predicting adverse cardiac events in asymptomatic diabetic patients. However, the clinical utility of myocardial perfusion scintigraphy is debated intensively due to the paucity of prospective and outcome based evidence. The controversy stems from several observational studies, epidemiologic data and cost-effectiveness analyses. Thus, although several authors and professional organizations advocate the use of stress imaging for screening higher risk asymptomatic diabetic patients, others are cautious in recommending any kind of stress testing in that population. This review is based on a broad survey of the literature and discusses the potential role of stress myocardial perfusion scintigraphy in screening asymptomatic diabetic subjects for coronary heart disease in the current era and in relation with other non-invasive screening tools.

Incidence and predictors of silent myocardial infarction in type 2 diabetes and the effect of fenofibrate: an analysis from the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study

AIMS

To determine the incidence and predictors of, and effects of fenofibrate on silent myocardial infarction (MI) in a large contemporary cohort of patients with type 2 diabetes in the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study.

METHODS AND RESULTS

Routine electrocardiograms taken throughout the study were assessed by Minnesota-code criteria for the presence of new Q-waves without clinical presentation and analysed with blinding to treatment allocation and clinical outcome. Of all MIs, 36.8% were silent. Being male, older age, longer diabetes duration, prior cardiovascular disease (CVD), neuropathy, higher HbA(1c), albuminuria, high serum creatinine, and insulin use all significantly predicted risk of clinical or silent MI. Fenofibrate reduced MI (clinical or silent) by 19% [hazard ratio (HR) 0.81, 95% confidence interval (CI) 0.69-0.94; P = 0.006], non-fatal clinical MI by 24% (P = 0.01), and silent MI by 16% (P = 0.16). Among those having silent MI, fenofibrate reduced subsequent clinical CVD events by 78% (HR 0.22, 95% CI 0.08-0.65; P = 0.003).

CONCLUSION

Silent and clinical MI have similar risk factors and increase the risk of future CVD events. Fenofibrate reduces the risk of a first MI and substantially reduces the risk of further clinical CVD events after silent MI, supporting its use in type 2 diabetes.

Detecting occult coronary artery disease followed by early coronary artery bypass surgery in patients with diabetic retinopathy: report from a diabetic retinocoronary clinic

OBJECTIVES

We hypothesized that a large number of patients with diabetic retinopathy who could benefit greatly from early coronary artery bypass grafting would not be identified.

METHODS

Patients with diabetic retinopathy receiving ophthalmologic care as outpatients in our hospital in whom coronary artery disease was not previously suspected were referred randomly to the diabetic retinocoronary clinic and were asked to participate in diagnostic tests, including an exercise treadmill test and exercise thallium scintigraphy or coronary computed tomography. Patients who had type 1 diabetes mellitus, required hemodialysis, or both were excluded from this study. A definitive diagnosis of coronary artery disease was confirmed by means of coronary angiography.

RESULTS

Of 214 patients with diabetic retinopathy, 55 (25.7%) were confirmed as having significant stenotic coronary artery disease. Patients with angiographically confirmed coronary disease were older than those with negative results on diagnostic tests (62.2 + or - 9.8 vs 57.9 + or - 10.3 years, P = .01). Fifteen had 1-vessel disease, 17 had 2-vessel disease, 14 had 3-vessel disease, 1 had left main trunk plus 1-vessel disease, 2 had left main trunk plus 2-vessel disease, and 5 had left main trunk plus 3-vessel disease. Eight patients had left main trunk disease, and 18 patients with non-left main trunk disease had proximal left anterior descending coronary artery (LAD) disease. Forty-two patients showed indications of coronary revascularization (coronary artery bypass grafting in 17 and percutaneous coronary intervention in 25). During the entire follow-up (287.6 + or - 183.2 days) of 39 patients undergoing coronary revascularization, all were alive without myocardial infarction, but 8 experienced vitreous hemorrhage.

CONCLUSIONS

Approximately 25% of patients with diabetic retinopathy receiving ophthalmologic care as outpatients have a significant stenotic coronary artery disease. Of the total diabetic population, a large number of patients with diabetic retinopathy who show strong indications for early coronary artery bypass grafting might well go unrecognized.

A comparative evaluation of Tl-201 and Tc-99m sestamibi myocardial perfusion spect imaging in diabetic patients

AIM

Myocardial perfusion scintigraphy (MPS) is an effective tool for early diagnosis of coronary artery disease (CAD) in type II diabetes mellitus (DM). The purpose of this study was to review the comparative findings of Tc-99m MIBI and Tl-201 MPS in defining normal and abnormal myocardial segments, type and extent of the perfusion defects with reference to coronary angiography findings in diabetic patients.

METHODS

Thirty patients with type II DM who had abnormal Tc-99m MIBI MPS findings and underwent coronary angiography were included this study (20 male, 10 female; mean age was 64 +/- 11 years). Those patients were also investigated with Tl-201 MPS thereafter. All scintigraphic images were evaluated semiquantitatively using a 20-segments myocardial model. The perfusion of myocardial segments, reversibility and severity of defects based on defect score were compared using the MIBI and Tl-201 images in relation to coronary angiography. Diffuse slow-washout of Tl-201 was also noted.

RESULTS

A total of 600 myocardial segments were comparatively analyzed. Diagnostic concordance between both tracers in defining normal and abnormal perfusion on a segmental basis was 88% (kappa = 0.71). The percentage of normal, reversible and non-reversible segments in the Tc-99m MIBI and Tl-201 study were 67-61%, 11-20% and 22-19% respectively. While the number of irreversible defects were similar for both tracers, more number of reversible defects were identified by Tl-201 MPS than Tc-99m MIBI (65 vs. 123, p = 0.001). No significant difference between the defect scores of both tracers was found.

CONCLUSION

MPS using both tracers offered agreement in defining or excluding perfusion abnormalities in a major part of the data. However, Tl-201 MPS yielded better detection rate of myocardial ischemia than Tc-99m MIBI MPS in diabetic patients.

Reviewing myocardial silent ischemia: specific patient subgroups

Silent myocardial ischemia (SMI) is a relatively common, yet poorly understood, clinical entity. The most accurate means of detecting SMI and the precise treatment endpoints remain unclear. However, the presence of SMI correlates with the likelihood of future adverse cardiac events. Evidence suggests that patients at high risk of severe cardiac ischemia, even with the absence of symptoms, derive the greatest benefit from an aggressive diagnostic and therapeutic approach. This paper is giving a detailed review of SMI in regards to specific patient subgroups, i.e. populations with diabetes mellitus, hypertension, elderly patients, post-revascularization patients, women, the suggested screening procedures for each subgroup, as well as the emersion of new markers for the selection of high-risk patients for screening.

The changing costs and benefits of screening for asymptomatic coronary heart disease in patients with diabetes

Aggressive medical therapy can be justified in most patients with diabetes, but there may be some higher-risk asymptomatic patients who could benefit from revascularization and/or medical therapy for myocardial ischemia. Silent myocardial ischemia (SMI) might be used to identify these high-risk individuals. In this Review we define SMI as objective evidence of ischemia from any noninvasive test occurring in an asymptomatic patient. We outline what is known about asymptomatic coronary heart disease (CHD) in diabetes and how this relates to SMI. We examine how SMI predicts angiographic CHD and CHD events, and we describe the changing role of CHD screening as reflected by various guidelines. We identify the recent research suggesting that there may be substantial numbers of high-risk asymptomatic patients who have diabetes with undiagnosed CHD and who could benefit from more-active intervention; however, with the recent advances in medical therapy, and the uncertain benefits of screening, current guidelines strongly discourage this practice, except in limited clinical situations, such as before major surgery. Carefully conducted clinical trails using state-of-the-art investigations and therapy in well-characterized patients with diabetes are urgently required to inform physicians on when and how to intervene.

Silent myocardial ischemia is associated with autonomic neuropathy and other cardiovascular risk factors in type 1 and type 2 diabetic subjects, especially in those with microalbuminuria

The prevalence of silent myocardial ischemia (SMI) seems to be above average in diabetic subjects. As routine screening is costly, identifying high-risk populations is mandatory. This study aimed to estimate the prevalence of SMI in diabetic subjects and in controls and to define the diabetic population at risk. We studied 353 asymptomatic caucasian subjects (217 with diabetes and 136 controls matched by age, sex, and cardiovascular risk factors) with normal resting ECG. The diabetic group included 39 type 1 and 178 type 2 diabetics (age 57 +/- 11 yr, 162 males/55 females). Subjects performed the Treadmill Test (TT) and, when abnormal, underwent single-photon emission computed tomography (SPECT) with exercise testing or dipyridamole injection. Coronary angiography was performed if the SPECT was suggestive of ischemia. TT was positive in 16 (8.5%) diabetics: 3 with type 1 and 13 with type 2. No controls had positive TT. SPECT was performed in 13 subjects and was positive in 10; angiography was performed in 7 and identified significant lesions in all cases. Patients with SMI were older and had a higher prevalence of autonomic neuropathy, hypertension, and dyslipidemia than those without. Microalbuminuria was also higher in the SMI group (613 +/- 211 vs 72 +/- 245 mg/d; p < 0.05). We conclude that diabetic patients aged over 60 with autonomic neuropathy and other cardiovascular risk factors should be screened for the presence of SMI especially if they have increased microalbuminuria.

The prevalence of silent ischemia in Turkish patients with type 2 diabetes mellitus

Cardiovascular disease (CVD) is the major cause of death in patients with type 2 diabetes mellitus. However, the diagnosis of CVD is delayed due to concealment of antecedent symptoms by factors such as autonomic neuropathy. In this study, we aimed to investigate the frequency of silent ischemia by using exercise electrocardiogram (ECG). The present study included 500 Turkish patients with type 2 diabetes (male/female: 222/278), who showed no evidence of CAD and angina pectoris or no sign(s) of ischemic changes in resting ECGs. All patients underwent treadmill exercise test according to Bruce protocol, and 62 cases (12.4%) exhibited abnormal changes. These patients identified by exercise ECG consisted of 28 males (28/222, [12.6%]) and 34 females (34/278, [12.2%]) and were then examined by coronary angiography. CAD was diagnosed in 53 individuals by coronary angiography. The abnormalities of exercise test are associated with the age of the patients or the duration of diabetes (p < 0.05). There is no significant difference in the severity of coronary disease or in the prevalence of silent ischemia between male and female patients. However, among the patients identified by exercise ECG females have higher body mass index than males, suggesting that obesity may represent the risk factor of CAD in women with type 2 diabetes.