A randomized study comparing isotope and echocardiography stress testing in the screening of silent myocardial ischaemia in type 2 diabetic patients

Silent Myocardial Ischemia: From Pathophysiology to Diagnosis and Treatment

Silent myocardial ischemia (SMI), characterized by a lack of overt symptoms despite an inadequate blood supply to the myocardium, remains a challenging entity in cardiovascular medicine. The pathogenesis involves intricate interactions of vascular, neurohormonal, and metabolic factors, contributing to perfusion deficits without the characteristic chest pain. Understanding these mechanisms is pivotal for recognizing diverse clinical presentations and designing targeted interventions. Diagnostic strategies for SMI have evolved from traditional electrocardiography to advanced imaging modalities, including stress echocardiography, single-photon emission computed tomography (SPECT), positron emission tomography (PET), and cardiac magnetic resonance imaging (MRI). Treating SMI is a matter of ongoing debate, as the available evidence on the role of invasive versus medical management is controversial. This comprehensive review synthesizes current knowledge of silent myocardial ischemia, addressing its pathophysiology, diagnostic modalities, and therapeutic interventions.

Screening for Coronary Artery Disease in Patients with Diabetes

PURPOSE OF REVIEW

The study aims to describe methods for detecting subclinical coronary artery disease (CAD) and their potential implications in asymptomatic patients with diabetes.

RECENT FINDINGS

Imaging tools can assess non-invasively the presence and severity of CAD, based on myocardial ischemia, coronary artery calcium score, and coronary computed tomography coronary angiography. Subclinical CAD is common in the general population ageing 50 to 64 years with any coronary atherosclerosis present in 42.1% and obstructive CAD in 5.2%. In patients with diabetes, an even higher prevalence has been noted. The presence of myocardial ischemia, obstructive CAD, and the extent of coronary atherosclerosis provide powerful risk stratification regarding the risk of cardiovascular events. However, randomized trials evaluating systematic screening in the general population or patients with diabetes have demonstrated only moderate impact on management and no significant impact on patient outcomes. Despite providing improved risk stratification, systematic screening of CAD is not recommended in patients with diabetes.

Asymptomatic myocardial ischemia forecasts adverse events in cardiovascular magnetic resonance dobutamine stress testing of high-risk middle-aged and elderly individuals

BACKGROUND

Current guidelines for assessing the risk of experiencing a hospitalized cardiovascular (CV) event discourage stress testing of asymptomatic individuals; however, these recommendations are based on evidence gathered primarily from those aged < 60 years, and do not address the possibility of unrecognized "silent myocardial ischemia" in middle aged and older adults.

METHODS

We performed dobutamine cardiovascular magnetic resonance (CMR) stress testing in 327 consecutively recruited participants aged > 55 years without CV-related symptoms nor known coronary artery disease, but otherwise at increased risk for a future CV event due to pre-existing hypertension or diabetes mellitus for at least 5 years. After adjusting for the demographics and CV risk factors, log-rank test and Cox proportional hazards models determined the additional predictive value of the stress test results for forecasting hospitalized CV events/survival. Either stress-induced LV wall motion abnormalities or perfusion defects were used to indicate myocardial ischemia.

RESULTS

Participants averaged 68 ± 8 years in age; 39% men, 75% Caucasian. There were 38 hospitalized CV events or deaths which occurred during a mean follow-up of 58 months. Using Kaplan-Meier analyses, myocardial ischemia identified future CV events/survival (p <  0.001), but this finding was more evident in men (p <  0.001) versus women (p = 0.27). The crude hazard ratio (HR) of myocardial ischemia for CV events/survival was 3.13 (95% CI: 1.64-5.93; p < 0.001). After accounting for baseline demographics, CV risk factors, and left ventricular ejection fraction/mass, myocardial ischemia continued to be associated with CV events/survival [HR: 4.07 (95% CI: 1.95-8.73) p < 0.001].

CONCLUSIONS

Among asymptomatic middle-aged individuals with risk factors for a sentinel CV event, the presence of myocardial ischemia during dobutamine CMR testing forecasted a future hospitalized CV event or death. Further studies are needed in middle aged and older individuals to more accurately characterize the prevalence, significance, and management of asymptomatic myocardial ischemia.

TRIAL REGISTRATION

( ClinicalTrials.gov identifier): NCT00542503 and was retrospectively registered on October 11th, 2007.

Identification of coronary heart disease in asymptomatic individuals with diabetes mellitus: to screen or not to screen

Coronary heart disease (CHD) is highly prevalent in patients with diabetes mellitus (DM), and remains the single most common cause of death among this population. Regrettably, a significant percentage of diabetics fail to perceive the classic symptoms associated with myocardial ischemia. Among asymptomatic diabetics, the prevalence of abnormal cardiac testing appears to be high, ranging between 10% and 62%, and mortality is significantly higher in those with abnormal scans. Hence, the potential use of screening for CHD detection among asymptomatic DM individuals is appealing and has been recommended in certain circumstances. However, it was not until recently, that this question was addressed in clinical trials. Two studies randomized a total of 2,023 asymptomatic diabetics to screening or not using cardiac imaging with a mean follow up of 4.4 ± 1.4 years. In combination, both trials showed lower than expected annual event rates, and failed to reduce major cardiovascular events in the screened group compared to the standard of care alone. The results of these trials do not currently support the use of screening tools for CHD detection in asymptomatic DM individuals. However, these studies have important limitations, and potential explanations for their negative results that are discussed in this manuscript.

Silent myocardial ischemia detected by single photon emission computed tomography (SPECT) and risk of cardiac events among asymptomatic patients with type 2 diabetes: a meta-analysis of prospective studies

OBJECTIVE

To assess the value of detecting silent myocardial ischemia (SMI) by single photon emission computed tomography (SPECT) in predicting risk of cardiac events among patients with type 2 diabetes mellitus (T2DM) who do not have overt cardiac symptoms.

MATERIALS AND METHODS

Electronic databases (PubMed, Cochrane Library, EMBASE, and others) and original article references were systematically searched through February 1, 2013. A fixed-effects model was applied to pooled data to estimate relative risks (RR) and 95% confidence intervals (CI).

RESULTS

Ten prospective studies with follow-up ranging from 1 to 6 years were identified. Among the total of 1360 asymptomatic patients with T2DM screened by SPECT, the cumulative prevalence rate of SMI was 26.1%. Patients with SMI were at increased risk of experiencing endpoints relative to patients without SMI: RR (95% CI) for cardiac death, 4.60 (1.78-11.84); non-fatal cardiac events, 3.48 (2.30-5.28); total cardiac events, 3.48 (2.59-4.68); and all-cause mortality, 2.20 (1.14-4.25). The risk of cardiac death and non-fatal cardiac events increased with increasing severity of SPECT-detected abnormalities.

CONCLUSIONS

SMI detected by SPECT is associated with increased risk of cardiac death, all-cause mortality, and non-fatal cardiac events in T2DM patients without overt cardiac symptoms. Advanced intervention procedures including intensive drug management should be implemented to reduce the risk of cardiac events for SMI-positive T2DM patients.

Relationship between silent myocardial ischemia and coronary artery disease risk factors

BACKGROUND

The association between silent myocardial ischemia (SMI) and coronary artery disease (CAD) risk factors in asymptomatic patients with no prior history of CAD referred for stress myocardial perfusion imaging (MPI) is unknown.

METHODS

We retrospectively evaluated patients who underwent MPI over a 3.4-year period to identify those who did not have chest pain, dyspnea, or known CAD. The presence of risk factors was categorized as none, 1-2, 3-4, and ≥5. MPI was performed using a rest thallium-201/stress Tc-99m sestamibi protocol, and read using a standard five-point perfusion score (0 = normal to 4 = absent) and a 17-segment left ventricular model. Summed stress score and summed rest score were derived as the sum of individual segmental scores at stress and rest, respectively. SMI was diagnosed if the summed differences score (SDS) was ≥2. Prognostically significant ischemia was defined by a SDS ≥ 8.

RESULTS

Among 1,354 asymptomatic patients, SMI was present in 97 (7.2%) and prognostically significant in 60 (4.4%). The prevalence, but not severity, of SMI increased with increasing CAD risk factors--0 for none, 4.1% for 1-2, 8.8% for 3-4, and 12% for those with ≥5 CAD risk factors (P value for trend = .001), in patients <74 years of age. Of the 59 (4.4%) patients who underwent coronary angiography, only 31 (2%) had significant anatomical CAD.

CONCLUSIONS

The prevalence of SMI and prognostically significant ischemia is low in asymptomatic patients without known CAD, and is related to the number of CAD risk factors in patients younger than 74 years of age.

Clinical review: Screening for coronary artery disease in type 2 diabetes

CLINICAL CONTEXT

Sensitive tools are available to diagnose occult ischemic and atherosclerotic coronary disease, yet screening for coronary artery disease (CAD) has not been shown to reduce cardiac events in patients with type 2 diabetes mellitus (T2DM). Professional guidelines are inconsistent regarding CAD screening recommendations, but it is suggested that those at highest risk (10-yr risk ≥20%) for cardiac events may benefit.

EVIDENCE ACQUISITION

We reviewed bibliographies of professional CAD screening guidelines, review articles, and clinical trials published within the last 10 yr, although we have included relevant older studies. We excluded studies that did not focus on T2DM or explicitly analyze that subgroup.

EVIDENCE SYNTHESIS

Although screening for coronary ischemia or atherosclerosis does provide incremental prognostic information in patients with T2DM and previously undiagnosed CAD, this has not been found to significantly impact outcomes. This appears to result from comparable efficacy of revascularization and optimal medical therapy in stable CAD. Limited evidence supports the hypothesis that those with more severe CAD (three-vessel, left main, proximal left anterior descending) amenable to bypass surgery may be potential beneficiaries of screening. However, the low prevalence of such candidates in the asymptomatic population, continuing advances with percutaneous intervention, and the lack of prospective trials makes such a recommendation currently unsupportable.

CONCLUSIONS

Findings to date do not support widespread screening for CAD in patients with T2DM. A future strategy identifying those at highest risk as screening candidates may ultimately be effective, but the optimal method for selecting those subjects or subsequent treatment is unknown.

Cardiac iodine-123 metaiodobenzylguanidine (123I-MIBG) scintigraphy parameter predicts cardiac and cerebrovascular events in type 2 diabetic patients without structural heart disease

BACKGROUND

Cardiac iodine-123 metaiodobenzylguanidine ((123)I-MIBG) scintigraphy is an established method of assessment of cardiovascular sympathetic function. The aim of the present study was to investigate the long-term cardiovascular predictive value of cardiac (123)I-MIBG scintigraphy parameters in Japanese type 2 diabetic patients without structural heart disease.

METHODS AND RESULTS

Cardiac (123)I-MIBG scintigraphy in 108 patients with type 2 diabetes who did not have structural heart disease, was evaluated. The washout rate (WR) was considered enhanced if it was ≥40%. Accurate follow-up information for 4.6 years was obtained in 54 enhanced WR patients (27 male; mean age, 61 ± 11 years) and in 54 sex- and age-matched preserved WR patients (27 male; mean age, 61 ± 10 years). Major adverse cardiac and cerebrovascular events (MACCE) were investigated. During follow-up, 10 enhanced WR patients developed MACCE including cardiac death, coronary revascularization, stroke, and congestive heart failure, while MACCE occurred in only 3 male patients. The Kaplan-Meier curves indicated that enhanced WR patients had higher incidence of MACCE than those with preserved WR (P<0.05). Cox proportional hazards regression analysis showed that age and enhanced WR were independently associated with the incidence of MACCE (hazard ratio, 4.06; 95% confidence interval: 1.194-18.76, P = 0.0237).

CONCLUSIONS

Abnormal WR of cardiac (123)I-MIBG scintigraphy at baseline has long-term cardiovascular predictive value in Japanese patients with type 2 diabetes without structural heart disease.