Prevalence and predictors of ischemia and outcomes in outpatients with diabetes mellitus referred for single-photon emission computed tomography myocardial perfusion imaging

Prevalence and Prognostic Importance of Abnormal Positron Emission Tomography Among Asymptomatic Patients With Diabetes Mellitus

BACKGROUND

Ischemia and reduced global myocardial blood flow reserve (MBFR) are associated with high cardiovascular risk among symptomatic patients with diabetes mellitus (DM).

OBJECTIVES

This study aimed to assess the prevalence and prognostic importance of silent ischemia and reduced MBFR among asymptomatic patients with DM.

METHODS

This study included 2,730 consecutive patients with DM, without known coronary artery disease (CAD) or cardiomyopathy, who underwent rubidium-82 rest/stress positron emission tomography (PET) myocardial perfusion imaging (MPI) from 2010 to 2016. These patients were followed up for all-cause mortality (n = 461) for a median follow-up of 3 years. Patients were considered asymptomatic if neither chest pain nor dyspnea was elicited. Rates of ischemia, reduced MBFR, and coronary microvascular dysfunction on PET were assessed in both groups. Cox regression was used to define the independent association of abnormal MPI markers with mortality.

RESULTS

One-quarter of patients with DM (23.7%; n = 647) were asymptomatic; ischemia was present in 30.5% (n = 197), reduced MBFR in 62.3% (n = 361), and coronary microvascular dysfunction in 32.7% (n = 200). In adjusted analyses, reduced MBFR (HR per 0.1 unit decrease in MBFR: 1.08 [95% CI: 1.03-1.12]; P = 0.001) and reduced ejection fraction (HR per 5% decrease: 1.10 [95% CI: 1.01-1.18]; P = 0.02) were independently prognostic of mortality among asymptomatic patients, but ischemia was not. This was comparable to DM patients with symptoms. Insulin use and older age were significant predictors of reduced MBFR among asymptomatic patients with DM.

CONCLUSIONS

In both symptomatic and asymptomatic patients with DM, impairment in MBFR is common and associated with greater mortality risk.

Economic and healthcare resource utilization assessments of PET imaging in Coronary Artery Disease diagnosis: a systematic review and discussion of opportunities for future economic evaluations

AIMS

This systematic literature review (SLR) consolidated economic and healthcare resource utilization (HCRU) evidence for positron emission tomography (PET) and single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) to inform future economic evaluations.

MATERIALS AND METHODS

An electronic search was conducted in MEDLINE, Embase, and Cochrane databases from 2012-2022. Economic and HCRU studies in adults who underwent PET- or SPECT-MPI for coronary artery disease (CAD) diagnosis were eligible. A qualitative methodological assessment of existing economic evaluations, HCRU, and downstream cardiac outcomes was completed. Exploratory meta-analyses of clinical outcomes were performed.

RESULTS

The search yielded 13,439 results, with 71 records included. Economic evaluations and comparative clinical trials were limited in number and outcome types (HCRU, downstream cardiac outcomes, and diagnostic performance) assessed. No studies included all outcome types and only one economic evaluation linked diagnostic performance to HCRU. The meta-analyses of comparative studies demonstrated significantly higher rates of early- and late-invasive coronary angiography and revascularization for PET- compared to SPECT-MPI; however, the rate of repeat testing was lower with PET-MPI. The rate of acute myocardial infarction was lower, albeit non-significant with PET- vs. SPECT-MPI.

LIMITATIONS AND CONCLUSIONS

This SLR identified economic and HCRU evaluations following PET- and SPECT-MPI for CAD diagnosis and determined that existing studies do not capture all pertinent outcome parameters or link diagnostic performance to downstream HCRU and cardiac outcomes, thus, resulting in simplified assessments of CAD burden. A limitation of this work relates to heterogeneity in study designs, patient populations, and follow-up times of existing studies. Resultingly, it was challenging to pool data in meta-analyses. Overall, this work provides a foundation for the development of comprehensive economic models for PET- and SPECT-MPI in CAD diagnosis, which should link diagnostic outcomes to HCRU and downstream cardiac events to capture the full CAD scope.

Prognostic value of coronary CT angiography and CT myocardial perfusion imaging among patients with and without Diabetes

OBJECTIVES

Whether stress CT myocardial perfusion imaging (CT-MPI) improves risk assessment in patients with diabetes mellitus (DM) remains unexplored. We aimed to evaluate the prognostic value of coronary CT angiography (CCTA) and stress CT-MPI in suspected coronary artery disease (CAD) patients with and without DM.

METHODS

A total of 334 patients with suspected CAD who underwent CCTA and stress CT-MPI from May 2020 to July 2021 were retrospectively analyzed. The endpoint was major adverse cardiovascular events (MACEs). Multivariable Cox regression analysis was used to evaluate the risk factors for MACEs, including clinical risk factors, CCTA characteristics and CT-MPI characteristics.

RESULTS

After a median follow-up of 21 months,15 patients of the DM group and 16 patients of the non-DM group experienced MACEs. Multivariate Cox stepwise regression analysis showed that abnormal perfusion myocardial segments ratio was associated with MACEs after adjusting for clinical risk factors and CCTA characteristics in all patients (HR:1.023, p < 0.001), DM group (HR:1.024, p = 0.008) and non-DM group (HR:1.028, p = 0.003). By adding CT-MPI characteristics to CCTA characteristics and clinical risk factors, the global chi-square for predicting MACEs increased from 62.24 to 78.84 in all patients (p < 0.001), from 19.18 to 27.30 in DM group (p = 0.004) and from 39.51 to 48.65 in non-DM group (p = 0.003); the increment of C-index in all patients, DM group and non-DM group were 0.018, 0.054 and 0.019, respectively.

CONCLUSION

In all patients and those with and without DM, CT-MPI has incremental prognostic value over clinical risk factors alone or combined with CCTA characteristics in predicting MACEs.

Cardiovascular Magnetic Resonance Imaging as an Adjunct to the Evaluation of Cardiovascular Involvement in Diabetes Mellitus

Diabetes mellitus (DM) is a new epidemic which has presented an immense increase in recent decades, due to the rapid increase in obesity. Cardiovascular disease (CVD) significantly reduces life expectancy and is the main cause of death in type 2 diabetes mellitus (T2DM). Strict glycemic control is a well-established method to combat microvascular CVD of type 1 diabetes mellitus (T1DM); its role against CVD of the T2DM risk has not been well documented. Therefore, the most efficient prevention is multifactorial risk factor reduction. Recently, the European Society of Cardiology published its 2019 recommendations on CVD in DM. Although all clinical points were discussed in this document, only a few comments were presented about when and how we should recommend cardiovascular (CV) imaging. Currently, CV imaging is the "must" in CV noninvasive evaluation. Alterations in CV imaging parameters can lead to early recognition of various types of CVD. In this paper, we briefly discuss the role of noninvasive imaging modalities, emphasizing the benefits of including cardiovascular magnetic resonance (CMR) in the evaluation of DM. CMR, in the same examination, can provide an assessment of tissue characterization, perfusion and function, with excellent reproducibility and without radiation or limitations, due to the body habitus. Therefore, it can play a dominant role in the prevention and risk stratification of DM. The suggested protocol for DM evaluation should include routine annual echocardiographic evaluation of all DM patients and CMR assessment of those with poorly controlled DM, microalbuminuria, heart failure, arrhythmia and recent alterations in clinical or echocardiographic evaluation.

The prevalence and predictors of inducible myocardial ischemia among patients referred for radionuclide stress testing

BACKGROUND

The frequency of inducible myocardial ischemia has declined in contemporary stress test cohorts, suggesting a need to re-evaluate its optimal use. To-date, however, a comprehensive analysis of the most potent predictors of myocardial ischemia among cardiac stress test patients has not been conducted.

METHODS

We assessed 27,615 patients referred for stress-rest SPECT myocardial perfusion imaging between January 1, 2004 and December 31, 2017. Chi-square analysis was used to ascertain the most potent predictors of ischemia.

RESULTS

Among our cohort, CAD status (presence/absence of known CAD), rest left ventricular ejection fraction (LVEF), and typical angina were the most potent predictors of ischemia. The frequency of ischemia was only 6.6% among patients with an LVEF > 55% but 38.1% for patients with LVEF < 45% (P < 0.001). The frequency of myocardial ischemia was fourfold higher among patients with known CAD vs no known CAD (28.0% vs 6.5%, P < 0.001) and approximately threefold higher among patients with typical angina vs patients with atypical symptoms (P < 0.001).

CONCLUSIONS

The frequency of myocardial ischemia varies markedly according to the common clinical parameters and is particularly high among patients with known CAD, low LVEF, and typical angina. These observations may be used to develop more cost-effective strategies for referring patients for cardiac stress testing.

Added Prognostic Value of Plaque Burden to Computed Tomography Angiography and Myocardial Perfusion Imaging in Patients with Diabetes

BACKGROUND

We aimed to compare the added prognostic value of plaque burden to cardiac computed tomographic angiography (CCTA) anatomic assessment and single-photon emission computed tomography (SPECT) physiologic assessment in patients with diabetes undergoing both tests.

METHODS

Consecutive patients with diabetes who underwent clinically indicated CCTA and SPECT myocardial imaging for suspected coronary artery disease were included. Stenosis severity and segment involvement score (SIS) were determined from CCTA, and presence of ischemia was determined from SPECT. Patients were followed from date of imaging for major adverse cardiovascular events (MACE).

RESULTS

A total of 778 patients were included (mean age 60.6 ± 14.4 years, 55% males). After a median follow-up of 31 months, 87 (11%) patients experienced a MACE. In multivariable Cox regression models, SIS significantly predicted outcomes in models including obstructive stenosis and ischemia (hazard ratio 1.17, 95% confidence interval 1.10-1.24, P < .001; hazard ratio 1.16, 95% confidence interval 1.10-1.23, P < .001, respectively), and improved discrimination (Harrel's C 0.75, P = .006; 0.76, P = .006 in models with CCTA obstructive stenosis and SPECT ischemia, respectively). Results were consistent using subgroups of summed scores by composition of plaque (calcified vs noncalcified) and alternate definitions of obstructive stenosis.

CONCLUSION

Our results suggest that in high-risk patients with diabetes and suspected coronary disease, SIS has incremental prognostic value over ischemia by SPECT or stenosis by CCTA in predicting incident cardiovascular outcomes.

Multimodality imaging approach to left ventricular dysfunction in diabetes: an expert consensus document from the European Association of Cardiovascular Imaging

Heart failure (HF) is among the most important and frequent complications of diabetes mellitus (DM). The detection of subclinical dysfunction is a marker of HF risk and presents a potential target for reducing incident HF in DM. Left ventricular (LV) dysfunction secondary to DM is heterogeneous, with phenotypes including predominantly systolic, predominantly diastolic, and mixed dysfunction. Indeed, the pathogenesis of HF in this setting is heterogeneous. Effective management of this problem will require detailed phenotyping of the contributions of fibrosis, microcirculatory disturbance, abnormal metabolism, and sympathetic innervation, among other mechanisms. For this reason, an imaging strategy for the detection of HF risk needs to not only detect subclinical LV dysfunction (LVD) but also characterize its pathogenesis. At present, it is possible to identify individuals with DM at increased risk HF, and there is evidence that cardioprotection may be of benefit. However, there is insufficient justification for HF screening, because we need stronger evidence of the links between the detection of LVD, treatment, and improved outcome. This review discusses the options for screening for LVD, the potential means of identifying the underlying mechanisms, and the pathways to treatment.

Long-term outcomes in patients with normal coronary arteries, nonobstructive, or obstructive coronary artery disease on invasive coronary angiography

Background

Normal or near normal coronary arteries (NNCA) or nonobstructive coronary artery disease (CAD) are commonly found on invasive coronary angiography (ICA).

Hypothesis

We aimed to determine long‐term outcomes by severity of CAD in a contemporary cohort of patients undergoing ICA for evaluation for ischemic heart disease.

Methods

We assessed a consecutive cohort of 925 patients who underwent non‐emergent ICA over 24 months. Cardiac death (CD), nonfatal myocardial infarction (NFMI), late revascularization, and medication use were assessed.

Results

Follow‐up data was available in 850 patients. Of patients without heart failure, at a median of 6.0 years, there was a significant decrease in survival free from CD or NFMI, and from all cardiac events, for those with obstructive CAD compared with patients with NNCAs or nonobstructive CAD (p < .001 for both). No differences between NNCA and nonobstructive CAD patients in rates of CD or NFMI (2.0% vs. 2.1%/year, p = .58) or all cardiac events (2.4% vs. 2.9%/year, p = .84) were observed.

Conclusion

Long‐term follow‐up in a contemporary cohort of consecutive patients undergoing non‐emergent ICA for detection of CAD showed no difference in annual rates of CD or NFMI, or total cardiac events, in patients with NNCAs versus those with nonobstructive CAD, whereas patients with obstructive CAD had significantly more events. Event rates were low and similar by gender. Use of aspirin, lipid lowering therapy, and beta‐blockers increased in all subgroups after ICA. We speculate this may explain the low incidence of subsequent cardiac events, and similar event rates in patients with NNCA and nonobstructive CAD, even in patients presenting with non‐ST‐elevation MI.

Role of microvascular dysfunction in left ventricular dysfunction in type 2 diabetes mellitus

BACKGROUND

Although microvascular disease (mVD) has been linked to poor cardiovascular outcomes in diabetes mellitus, the contribution of mVD to diabetic cardiomyopathy (DC) is unexplored. We investigated whether LV systolic and diastolic dysfunction is associated with mVD in T2DM.

METHODS

We recruited 32 asymptomatic patients with T2DM (age 71 ± 4 years, 31% females) from a community-based population. All underwent a comprehensive echocardiogram at baseline including assessment of global longitudinal strain (GLS) and diastolic function. Adenosine stress perfusion on cardiac magnetic resonance imaging (CMR) was performed in all patients. Coronary sinus flow (CSF) was measured offline at rest and peak stress with coronary flow reserve (CFR) calculated as the ratio of global stress and rest CSF.

RESULTS

Resting CSF was reduced in 15 (47%) compared to 4 (13%) with adenosine-stress (p = 0.023). Overall, CFR was observed to be reduced in the cohort (2.38 [IQR 2.20]). Abnormal CFR was not associated with diabetes duration of ≥10 years or poor glycaemic control. CFR was not associated with abnormal GLS (OR 1.04 [95% CI 0.49, 2.20], p = 0.93). However, a modest negative correlation was observed with e' and CFR (r = -0.49, p = 0.004).

CONCLUSION

This pilot study did not show correlation between subclinical systolic dysfunction and a novel MRI biomarker of microvascular disease. However, there was a weak correlation with myocardial relaxation. Confirmation of these findings in larger studies is indicated.

Safety measures and clinical outcome of Nuclear Cardiology Department during Covid-19 lockdown pandemic: Northern Italy experience

BACKGROUND

The Covid-19 pandemic led to a complete renewal of clinical activities of Italian hospitals. During the lockdown, all hospitals in Italy had to suspend non-urgent clinical activities. The prolonged suspension of elective activities could have caused a series of problems.

METHODS

A new ad hoc protocol was designed. Single-day fast-imaging protocol with regadenoson-stress 99mTc-tetrofosmin imaging was preferred. Patients were contacted by phone 4 days before the test and answered to a questionnaire which will be repeated on the day of the exam. Body temperature <37.5 degrees C and no Covid-19 symptoms were necessary to enter the unit. Patients wore surgical mask and gloves. Social distancing was maintained throughout the examination. Healthcare professionals wore a personal protective equipment.

RESULTS

A total of 46 patients were studied from April 7 to May 15, 2020, before the publication of the recommendations from ASNC and SNMMI. None of the patients experienced complications. Follow-up of patients discharged was carried by phone. No Covid-19 infection symptoms were reported. On May 18, 2020 all the healthcare providers of nuclear cardiology department underwent serological testing IgG and IgM and none were positive.

CONCLUSION

Strict ad hoc hygiene protocol for Covid-19 pandemic avoids diagnostic-therapeutic delay and lengthening of waiting lists. Our experience confirms that pursuing WHO recommendations and recent indication of ASNC and SNMMI is safe for both health providers and patients. Moreover, the incidence of significant inducible ischemia rises when correct stratification of patients is performed.

Prognostic value of SPECT myocardial perfusion entropy in high-risk type 2 diabetic patients

PURPOSE

Risk stratification of patients with type 2 diabetes mellitus (T2D) remains suboptimal. We hypothesized that myocardial perfusion entropy (MPE) quantified from SPECT myocardial perfusion images may provide incremental prognostic value in T2D patients independently from myocardial ischemia.

METHODS

T2D patients with very high and high cardiovascular risk were prospectively included (n = 166, 65 ± 12 years). Stress perfusion defect was quantified by visual evaluation of SPECT MPI. SPECT MPI was also used for the quantification of rest and stress MPE. The primary end point was major adverse cardiac events (MACEs) defined as cardiac death, myocardial infarction (MI), and myocardial revascularization > 3 months after SPECT.

RESULTS

Forty-four MACEs were observed during a 4.6-year median follow-up. Significant differences in stress MPE were observed between patients with and without MACEs (4.19 ± 0.46 vs. 3.93 ± 0.40; P ≤ .01). By Kaplan-Meier analysis, the risk of MACEs was significantly higher in patients with higher stress MPE (log-rank P ≤ 01). Stress MPE and stress perfusion defect (SSS ≥ 4) were significantly associated with the risk of MACEs (hazard ratio 2.77 and 2.06, respectively, P < .05 for both) after adjustment for clinical and imaging risk predictors as identified from preliminary univariate analysis. MPE demonstrated incremental prognostic value over clinical risk factors, stress test EKG and SSS as evidenced by nested models showing improved Akaike information criterion (AIC), reclassification (global continuous net reclassification improvement [NRI]: 63), global integrated discrimination improvement (IDI: 6%), and discrimination (change in c-statistic: 0.66 vs 0.74).

CONCLUSIONS

Stress MPE provided independent and incremental prognostic information for the prediction of MACEs in diabetic patients.

TRIAL REGISTRATION NUMBER

NCT02316054 (12/12/2014).

Whole-heart, ungated, free-breathing, cardiac-phase-resolved myocardial perfusion MRI by using Continuous Radial Interleaved simultaneous Multi-slice acquisitions at sPoiled steady-state (CRIMP)

PURPOSE

To develop a whole-heart, free-breathing, non-electrocardiograph (ECG)-gated, cardiac-phase-resolved myocardial perfusion MRI framework (CRIMP; Continuous Radial Interleaved simultaneous Multi-slice acquisitions at sPoiled steady-state) and test its quantification feasibility.

METHODS

CRIMP used interleaved radial simultaneous multi-slice (SMS) slice groups to cover the whole heart in 9 or 12 short-axis slices. The sequence continuously acquired data without magnetization preparation, ECG gating or breath-holding, and captured multiple cardiac phases. Images were reconstructed by a motion-compensated patch-based locally low-rank reconstruction. Bloch simulations were performed to study the signal-to-noise ratio/contrast-to-noise ratio (SNR/CNR) for CRIMP and to study the steady-state signal under motion. Seven patients were scanned with CRIMP at stress and rest to develop the sequence. One human and two dogs were scanned at rest with a dual-bolus method to test the quantification feasibility of CRIMP. The dual-bolus scans were performed using both CRIMP and an ungated radial SMS saturation recovery (SMS-SR) sequence with injection dose = 0.075 mmol/kg to compare the sequences in terms of SNR, cardiac phase resolution and quantitative myocardial blood flow (MBF).

RESULTS

Perfusion images with multiple cardiac phases in all image slices with a temporal resolution of 72 ms/frame were obtained. Simulations and in-vivo acquisitions showed CRIMP kept the inner slices in steady-state regardless of motion. CRIMP outperformed SMS-SR in slice coverage (9 over 6), SNR (mean 20% improvement), and provided cardiac phase resolution. CRIMP and SMS-SR sequences provided comparable MBF values (rest systolic CRIMP = 0.58 ± 0.07, SMS-SR = 0.61 ± 0.16).

CONCLUSION

CRIMP allows for whole-heart, cardiac-phase-resolved myocardial perfusion images without ECG-gating or breath-holding. The sequence can provide MBF if an accurate arterial input function is obtained separately.

Microalbuminuria (Moderate Albumin Excretion) and its relationship with Silent myocardial ischemia in treatment naïve type II diabetic patients

Objective

To determine the frequency of microalbuminuria (MAU) or Moderate Albumin Excretion (MAE) in treatment naïve type II diabetic patients and to compare the frequency of silent myocardial ischemia in treatment naive Type-II diabetic patients with and without microalbuminuria.

Methods

It was a cross sectional survey conducted in the outpatient Department, Jinnah Hospital Lahore, from 30th May 2015 to 29th November 2015. There were 227 patients, (consecutive treatment naïve type II diabetic patients), presenting to outpatient department were enrolled in the study. MAU/MAE, silent myocardial ischemia and effect modifiers like HbA1C > 7%, smoking pack years and dyslipidemia was determined. MAU/MAE was determined by urinary albumin excretion rate of 30-300 mg/24 hours and included patients underwent exercise tolerance test to diagnose silent myocardial ischemia.

Results

Out of total 165 patients (72.7%) were male and remaining 62 patients (27.3%) were female. The 54 patients (23.8%) had MAU/MAE. The 44 patients (19.4%) had silent myocardial infarction. When we cross tabulated microalbuminuria with silent myocardial infarction, result were significant. Out of 54 patients with MAU/MAE, 16 cases had silent myocardial infarction.

Conclusion

The frequency of microalbuminuria/ Moderate Albumin Excretion in treatment naïve type II diabetic patients was high and associated with the frequency of silent myocardial ischemia in treatment naïve type II diabetic patients with and without MAU MAU/MAE.

Non-Invasive Imaging in Diabetic Cardiomyopathy

There is increasing recognition of a specific diabetic cardiomyopathy beyond ischemic cardiomyopathy, which leads to structural and functional myocardial abnormalities. The aim of this review is to summarize the recent literature on diagnostic findings and prognostic significance of non-invasive imaging including echocardiography, nuclear imaging, computed tomography and cardiovascular magnetic resonance in diabetic cardiomyopathy.

Delayed Galectin-3-Mediated Reprogramming of Microglia After Stroke is Protective

Galectin-3 (Gal-3), a β-galactoside-binding lectin, has recently emerged as a molecule with immunoregulatory functions. We investigated the effects of Gal-3 on microglia morphology, migration, and secretory profile under physiological conditions and in the context of ischemic injury. We show that in the control conditions, exposure to recombinant Gal-3 increases microglial ramification and motility in vitro and in vivo via an IL-4-dependent mechanism. Importantly, after stroke, Gal-3 exerted marked immune-modulatory properties. Delivery of Gal-3 at 24 h after middle cerebral artery occlusion (MCAO) was associated with an increase in Ym1-positive microglia and decrease in iNOS. Analysis of cytokine profiles at the protein level revealed downregulation of pro-inflammatory cytokines and a marked upregulation of the anti-inflammatory cytokine, IL-4, 24 h after i.c.v. injection of Gal-3. Importantly, the observed shift in cytokines in microglia was associated with a significant decrease in the infarct size. Taken together, our results suggest that when delivered well after ischemic injury, Gal-3 might fine tune innate immunity and induce a therapeutic shift in microglia polarization.

Clinical Characteristics, Sex Differences, and Outcomes in Patients With Normal or Near-Normal Coronary Arteries, Non-Obstructive or Obstructive Coronary Artery Disease

Background

Normal or near‐normal coronary arteries (NNCAs) or nonobstructive coronary artery disease (CAD) are found on invasive coronary angiography in ≈55% of patients. Some attribute this to frequent referral of low‐risk patients. We sought to identify the referral indications, pretest risk, key clinical characteristics, sex, and outcomes in patients with NNCAs and nonobstructive CAD versus obstructive CAD on nonemergent invasive coronary angiography.

Methods and Results

Over 24 months, 925 consecutive patients were classified as having NNCAs (≤20% stenosis), nonobstructive CAD (21–49% stenosis), or obstructive CAD (≥50% stenosis). Outcomes included cardiac death, nonfatal myocardial infarction, and late revasclarization. NNCAs were found in 285 patients (31.0%), nonobstructive CAD in 125 (13.5%), and obstructive CAD in 513 (55.5%). NNCAs or nonobstructive CAD was found in 40.5% with stress ischemia, 27.9% after a non‐ST‐elevation myocardial infarction, and in 55.5% with stable or unstable angina. More women than men (53.5% versus 37.2%; P<0.001) had NNCAs or nonobstructive CAD across all referral indications. Pretest risk was high and ICA appropriate in 75.5% and 99.2% of patients, respectively. Annual rates of cardiac death or nonfatal myocardial infarction were 1.0%, 1.1%, and 6.7%, respectively, for patients with NNCAs, nonobstructive CAD, and obstructive CAD (P<0.001). No sex differences in outcomes were observed with either NNCAs, nonobstructive CAD, or obstructive CAD (P=0.84).

Conclusions

Many (44.5%) patients undergoing nonemergent invasive coronary angiography have NNCAs or nonobstructive CAD despite high pretest risk, including ischemia and troponin elevation. Although women had more NNCAs or nonobstructive CAD, there were no differences in event rates by sex. Patients with NNCAs and nonobstructive CAD had very low event rates.

Integrating Biomarkers and Imaging for Cardiovascular Disease Risk Assessment in Diabetes

Cardiovascular disease (CVD) risk assessment has changed substantially in recent years. While older guidelines considered diabetes a coronary disease risk equivalent, more recent guidelines recommend risk stratification on the basis of global risk scoring to target intensity of therapy. While patients with diabetes as a whole are at greater risk for CVD events, these patients may also benefit from risk stratification based on circulating biomarkers like high-sensitivity C-reactive protein, high-sensitivity cardiac troponin T, and N-terminal pro-B-type natriuretic peptide, as well as newer imaging modalities (coronary artery calcium, carotid intima-media thickness, and myocardial perfusion imaging). The addition of these CVD risk assessment modalities could play an important role for deciding how aggressive a physician should be with pharmacological therapy. Here, we discuss many of the current recommendations of CVD risk assessment in patients with diabetes including newer modalities for CVD risk assessment.

Prognostic Usefulness of Cardiac Stress Test Modalities in Patients With Type 2 Diabetes Mellitus Who Underwent Myocardial Perfusion Scintigraphy (from the Basel Asymptomatic High-Risk Diabetics' Outcome Trial)

Our study aimed to assess predictors of the stress test technique used and to evaluate the impact of exercise level achieved on risk stratification in patients with asymptomatic type 2 diabetes without a previous coronary artery disease. Little is known whether co-morbidities of these patients predict the stress technique and whether physical performance provides risk stratification: 400 patients underwent clinical evaluation and myocardial perfusion scintigraphy (MPS) using physical or pharmacological stress. Physical patients were divided into 2 groups: achieving <6 and ≥6 METs, respectively. The mean follow-up time was 2 years. Major cardiac events (MACEs) included myocardial infarction and/or cardiac death. Independent predictors of pharmacological stress were a body mass index of >30 kg/m² (hazard ratio 1.076, 95% confidence interval 1.027 to 1.127, p = 0.002) and a peripheral arterial disease (hazard ratio 2.888, 95% confidence interval 1.446 to 5.769, p = 0.003). Pharmacological patients had more MACE than physical patients (3.2% vs 1.0%, p = 0.03). Patients achieving <6 METs had a similar MACE rate as pharmacological patients (3.0% vs 3.2%, p = not significant) and more MACE than patients achieving ≥6 METs (3.0% vs 0.4%, p = 0.01). In patients achieving <6 METs and in pharmacological patients, MPS added an incremental prognostic value to pretest information (p values for global chi-square 0.012 and 0.04, respectively). In high-risk asymptomatic diabetic patients, co-morbidities were predictive of the stress technique used. Pharmacological patients had more MACE, similar to those unable to achieve 6 METs. MPS provided an incremental prognostic value in pharmacological patients and in patients with <6METs. In contrast, patients who were able to achieve ≥6 METs were at low risk and do not need further risk stratification.

Value of Exercise ECG for Risk Stratification in Suspected or Known CAD in the Era of Advanced Imaging Technologies

Exercise stress electrocardiography (ExECG) is underutilized as the initial test modality in patients with interpretable electrocardiograms who are able to exercise. Although stress myocardial imaging techniques provide valuable diagnostic and prognostic information, variables derived from ExECG can yield substantial data for risk stratification, either supplementary to imaging variables or without concurrent imaging. In addition to exercise-induced ischemic ST-segment depression, such markers as ST-segment elevation in lead aVR, abnormal heart rate recovery post-exercise, failure to achieve target heart rate, and poor exercise capacity improve risk stratification of ExECG. For example, patients achieving ≥10 metabolic equivalents on ExECG have a very low prevalence of inducible ischemia and an excellent prognosis. In contrast, cardiac imaging techniques add diagnostic and prognostic value in higher-risk populations (e.g., poor functional capacity, diabetes, or chronic kidney disease). Optimal test selection for symptomatic patients with suspected coronary artery disease requires a patient-centered approach factoring in the risk/benefit ratio and cost-effectiveness.

Dobutamine stress myocardial perfusion imaging: 8-year outcomes in patients with diabetes mellitus

AIMS

Many studies have examined the prognostic value of myocardial perfusion imaging (MPI) using single-photon emission computed tomography (SPECT) for the prediction of short- to medium-term outcomes. However, the long-term prognostic value of MPI in patients with diabetes mellitus remains unclear. Therefore, this study assessed the long-term prognostic value of MPI in a high-risk cohort of patients with diabetes mellitus.

METHODS AND RESULTS

A high-risk cohort of 207 patients with diabetes mellitus who were unable to undergo exercise testing underwent dobutamine stress MPI. Follow-up was successful in 206 patients; 12 patients were excluded due to early revascularization. The current data are based on the remaining 194 patients. Follow-up end points were all-cause mortality, cardiac mortality, and nonfatal myocardial infarction. The Kaplan-Meier survival curves were constructed, and univariable and multivariable analyses were performed to identify predictors of long-term outcome. During a mean follow-up of 8.1 ± 5.9 years, 134 (69%) patients died of which 68 (35%) died due to cardiac causes. Nonfatal myocardial infarction occurred in 24 patients (12%), and late (>60 days) coronary revascularization was performed in 61 (13%) patients. Survival analysis showed that MPI provided optimal risk stratification up to 4 years after testing. After that period, the outcome was comparable in patients with normal and abnormal MPI. Multivariable analyses showed that MPI provided incremental prognostic value up to 4 years after testing.

CONCLUSION

In high-risk patients with diabetes mellitus, dobutamine MPI provides incremental prognostic information in addition to clinical data for a 4-year period after testing.

Cardiovascular risk stratification in diabetic patients following stress single-photon emission-computed tomography myocardial perfusion imaging: the impact of achieved exercise level

BACKGROUND

Previous studies have demonstrated that diabetic patients undergoing exercise stress single-photon emission-computed tomography (SPECT) myocardial perfusion imaging (MPI) have significantly lower cardiac events when compared to the diabetic patients undergoing pharmacologic stress SPECT MPI across all perfusion categories. However, there are limited data on the level of exercise achieved during exercise SPECT MPI among diabetic patients and its impact on cardiovascular outcomes.

METHODS

We retrospectively analyzed 14,849 consecutive patients (3,654 diabetics and 11,195 non-diabetics) undergoing exercise stress, combined exercise and pharmacologic stress, and pharmacologic stress SPECT MPI from 1996 to 2005 at a single tertiary care center. Diabetic and non-diabetic patients were categorized into 3 groups based on the metabolic equivalents (METs) achieved: ≥5 METs, <5 METs, and pharmacologic stress groups. All studies were interpreted using the 17-segment ASNC model. The presence, extent, severity of perfusion defects were calculated using the summed stress score (SSS), and patients were classified into normal (SSS < 4), mildly abnormal (SSS 4-8), and moderate-severely abnormal (SSS > 8) categories. Annualized event rates (AER) for the composite end point of non-fatal myocardial infarction and cardiac death were calculated over a mean follow-up period of 2.4 ± 1.4 years with a maximum of 6 years.

RESULTS

In moderate-severe perfusion abnormality (SSS > 8) category, diabetic patients who were able to achieve ≥5 METs had significantly lower AER compared to diabetic patients who were unable to achieve ≥5 METs (3% vs 5.5%, P = .04), and non-diabetic patients unable to achieve ≥5 METs (3% vs 4.8%, P < .001). Diabetic patients who achieved a high workload of ≥10 METs had a very low AER of 0.9%. Diabetic patients, who attempted exercise but were unable to achieve ≥5 METs, still had significantly lower AER than diabetics undergoing pharmacologic stress MPI across all perfusion categories [1.5% vs 3.2%, P = .006 (SSS < 4); 2.5% vs 4.9%, P = .032 (SSS 4-8); 5.5% vs 10.3%, P = .003 (SSS > 8)]. After adjustment for cardiovascular risk factors, the percentage decrease in cardiac event rate for every 1-MET increment in exercise capacity was 10% in the overall cohort, 12% in diabetic group, and 8% in non-diabetic group.

CONCLUSIONS

Despite significant perfusion defects, diabetic patients who achieve ≥5 METs during stress SPECT MPI have significantly reduced risk for future cardiac events. Diabetic patients who achieve ≥10 METs have a very low annualized event rate. These findings support that exercise capacity obtained during SPECT MPI is a surrogate for outcomes among diabetic patients undergoing nuclear stress testing.

Assessing the prognostic implications of myocardial perfusion studies: identification of patients at risk vs patients who may benefit from intervention?

Stress myocardial perfusion imaging (MPI) has a well-established role in improving risk stratification. Recent analyses, compared with older data, suggest that the yield of stress MPI has decreased. In part, this trend relates to testing patients with heterogeneous, but improved, risk factor modification. In this setting, positron emission tomography with myocardial flow reserve enhances risk stratification as it reflects the end result of atherosclerosis. Recent studies have also emphasized the clinical impact of incremental risk stratification by assessing net reclassification improvement (NRI). Previous retrospective studies have favored an ischemic threshold to select patients that benefit from revascularization, but this finding has not been corroborated in randomized trials. However, no large randomized trial has directly tested a strategy of revascularization for patients with at least a moderate amount of ischemia at risk. Unfortunately, even when faced with a significantly abnormal MPI result, subsequent action is too often absent.