Effect of cardiac hybrid ¹⁵O-water PET/CT imaging on downstream referral for invasive coronary angiography and revascularization rate

Lipid-Lowering Medication and Outcomes After Anatomical and Functional Imaging in Suspected Coronary Artery Disease

BACKGROUND

Anatomical and functional imaging identify different phenotypes of coronary artery disease (CAD) that may have implications for lipid-lowering medication (LLM).

OBJECTIVES

The aim of this study was to assess the associations between LLM and long-term outcomes after combined anatomical and functional imaging in patients with suspected obstructive CAD.

METHODS

Consecutive patients (n = 1,973; 41% men; median age: 63 years) underwent coronary computed tomography angiography (CTA) because of suspected CAD. Patients in whom obstructive CAD was not ruled out by CTA underwent ischemia testing by positron emission tomography. Data on LLM purchases were collected until 2 years, and the combined endpoints of death, myocardial infarction, and unstable angina pectoris were assessed at a median of 6.7 years.

RESULTS

After imaging, LLM was used by 24% of patients with no CAD, 51% of patients with nonobstructive CAD, 72% of patients with obstructive CAD on CTA without myocardial ischemia, and 91% of patients with myocardial ischemia. The use of LLM decreased during follow-up, with 77% of patients with myocardial ischemia using LLM for 2 years. The use of LLM was associated with a lower annual rate of adverse events in patients with myocardial ischemia (6.1% vs 2.8%; P = 0.032) or obstructive CAD without myocardial ischemia (2.9% vs 1.4%; P = 0.004) but not in patients with nonobstructive CAD (1.5% vs 1.4%; P = 0.89) or no CAD (0.3% vs 0.3%; P = 0.68).

CONCLUSIONS

The CAD phenotype defined by anatomical and functional imaging guides the use of LLM. The presence of myocardial ischemia and anatomical obstructive coronary lesions were associated with a long-term outcome benefit from LLM.

Clinical impact of quantitative [15O] H2O PET/CT myocardial perfusion imaging on decision-making regarding invasive management of coronary artery disease

BACKGROUND

This study was performed to determine the impact of oxygen-15-labeled water ([15O] H2O) positron emission tomography/computed tomography (PET/CT) myocardial perfusion imaging (MPI) on referral for invasive coronary angiography (ICA) and revascularization.

METHODS

This study involved 57 patients who underwent [15O] H2O PET/CT MPI for evaluation of coronary artery disease (CAD). Data of referral for ICA and revascularization, clinical symptoms, and cardiac events within 6 months after MPI were assessed. Logistic regression was used to determine the predictors for referral and revascularization. The diagnostic values of hyperemic myocardial blood flow (MBF) and coronary flow reserve (CFR) were calculated.

RESULTS

Normal and abnormal MPI findings were observed in 18 (32%) and 39 (68%) patients, respectively. The referral rate was significantly different between the normal and abnormal MPI groups (5.6% and 48.7%, respectively; P = .002). Revascularization rate of abnormal MPI group was 40.0%. There were significant differences of hyperemic MBF and CFR between patients with and without referral. Hyperemic MBF was significant predictor for referral (OR 15.24, 95% CI 3.39-68.55, P < .005) and revascularization (OR 28.57, 95% CI 3.08-265.33, P < .005).

CONCLUSION

[15O] H2O PET/CT MPI showed a clinical impact on decision-making regarding invasive procedure for management of CAD.

EANM procedural guidelines for PET/CT quantitative myocardial perfusion imaging

The use of cardiac PET, and in particular of quantitative myocardial perfusion PET, has been growing during the last years, because scanners are becoming widely available and because several studies have convincingly demonstrated the advantages of this imaging approach. Therefore, there is a need of determining the procedural modalities for performing high-quality studies and obtaining from this demanding technique the most in terms of both measurement reliability and clinical data. Although the field is rapidly evolving, with progresses in hardware and software, and the near perspective of new tracers, the EANM Cardiovascular Committee found it reasonable and useful to expose in an updated text the state of the art of quantitative myocardial perfusion PET, in order to establish an effective use of this modality and to help implementing it on a wider basis. Together with the many steps necessary for the correct execution of quantitative measurements, the importance of a multiparametric approach and of a comprehensive and clinically useful report have been stressed.

Coronary computed tomography angiography and [15O]H2O positron emission tomography perfusion imaging for the assessment of coronary artery disease

Determining the anatomic severity and extent of coronary artery disease (CAD) by means of coronary computed tomography angiography (CCTA) and its effect on perfusion using myocardial perfusion imaging (MPI) form the pillars of the non-invasive imaging assessment of CAD. This review will 1) focus on CCTA and [¹⁵O]H₂O positron emission tomography MPI as stand-alone imaging modalities and their combined use for detecting CAD, 2) highlight some of the lessons learned from the PACIFIC trial (Comparison of Coronary CT Angiography, SPECT, PET, and Hybrid Imaging for Diagnosis of Ischemic Heart Disease Determined by Fractional Flow Reserve (FFR) (NCT01521468)), and 3) discuss the use of [¹⁵O]H₂O PET MPI in the clinical work-up of patients with a chronic coronary total occlusion (CTO).

15O-Water PET MPI: Current Status and Future Perspectives

Myocardial perfusion imaging with 15O-water positron emission tomography (PET) is a validated tool for quantitative measurement of myocardial blood flow (MBF) and myocardial flow reserve (MFR). Current scanner and software technology enable quantification of global and regional MBF in clinical PET myocardial perfusion imaging studies. Reduced stress MBF or MFR measured by 15O-water PET accurately detects hemodynamically significant coronary artery stenosis defined by intracoronary fractional flow reserve (FFR) measurement in patients with suspected obstructive coronary artery disease (CAD). Furthermore, MBF and MFR provide prognostic information on mortality and risk of myocardial infarction. Clinical experience in some centers indicates that clinical application of 15O-water PET in evaluation of CAD is feasible and guides management decisions on revascularization. This review discusses basic concepts of measuring MBF with 15O-water PET and reviews clinical studies on its application in evaluation of obstructive CAD.

Neuroprotective effect of salvianolate lyophilized injection against cerebral ischemia in type 1 diabetic rats

BACKGROUND

Salvianolate lyophilized injection (SLI) has been clinically used in China for the treatment of acutely cerebral infarction. Clinical and experimental studies have shown that Diabetes mellitus (DM) not only increases the risk of ischemic stroke recurrence but also leads to poor outcomes and increases fatality rates after stroke. Our previous study has proved that SLI can reduce the infarct volume after stroke in type 1 diabetic rats. The aim of the study is to explore the mechanism of SLI on stroke outcome in type 1 diabetic (T1DM) rats.

METHODS

Type 1 diabetes rats model (T1DM) was induced in male Wistar rats by intraperitoneal (i.p) injection of streptozotocin (60 mg/kg) and T1DM rats were subjected to intraluminal middle cerebral artery occlusion (MCAO). The T1DM + MCAO rats were randomly divided into six groups: sham-operated, model-vehicle, positive control group (Edaravone-treating, DE 6 mg/kg) and SLI-treating group (10.5 mg/kg, 21 mg/kg and 42 mg/kg). SLI and DE were administered by tail vein injection at 3 h after MCAO, then daily for 14 days. Micro-CT scans of the brain tissue revealed vessel characteristics and distribution in the ischemia zone. Glucose uptake was analyzed by PET/CT. RAGE, MMP9 and inflammatory factors (COX-2, TNF-α and ICAM-1), HQ-1, HQO-1 and Nrf-2 expression levels in the ischemic brain tissue were analyzed by Immunofluorescence staining and Western blot at 14 days after MCAO.

RESULTS

In this study, we have demonstrated that SLI treatment significantly increased the number of brain microvasculature in ipsilateral and glucose uptake in cortex, hippocampus and penumbra in the T1DM + MCAO rats. SLI also significantly decreased the expression of RAGE, MMP9 and inflammatory factors expression, and increased the expression of HQ-1, HQO-1 and Nrf-2 in T1DM + MCAO rats.

CONCLUSION

The study showed that SLI could protect against cerebral ischemia injury in T1DM + MCAO rats and the mechanism is related to decrease inflammatory factors and activate of the Nrf2/HO-1 signaling pathway.

Myocardial perfusion imaging with PET

Noninvasive assessment of coronary artery disease remains a challenging task, with a large armamentarium of diagnostic modalities. Myocardial perfusion imaging (MPI) is widely used for this purpose whereby cardiac positron emission tomography (PET) is considered the gold standard. Next to relative radiotracer distribution, PET allows for measurement of absolute myocardial blood flow. This quantification of perfusion improves diagnostic accuracy and prognostic value. Cardiac hybrid imaging relies on the fusion of anatomical and functional imaging using coronary computed tomography angiography and MPI, respectively, and provides incremental value as compared with either stand-alone modality.

Automatic extraction of forward stroke volume using dynamic PET/CT: a dual-tracer and dual-scanner validation in patients with heart valve disease

Background

The aim of this study was to develop and validate an automated method for extracting forward stroke volume (FSV) using indicator dilution theory directly from dynamic positron emission tomography (PET) studies for two different tracers and scanners.

Methods

35 subjects underwent a dynamic ¹¹C-acetate PET scan on a Siemens Biograph TruePoint-64 PET/CT (scanner I). In addition, 10 subjects underwent both dynamic ¹⁵O-water PET and ¹¹C-acetate PET scans on a GE Discovery-ST PET/CT (scanner II). The left ventricular (LV)-aortic time-activity curve (TAC) was extracted automatically from PET data using cluster analysis. The first-pass peak was isolated by automatic extrapolation of the downslope of the TAC. FSV was calculated as the injected dose divided by the product of heart rate and the area under the curve of the first-pass peak. Gold standard FSV was measured using phase-contrast cardiovascular magnetic resonance (CMR).

Results

FSV_PET correlated highly with FSV_CMR (r = 0.87, slope = 0.90 for scanner I, r = 0.87, slope = 1.65, and r = 0.85, slope = 1.69 for scanner II for ¹⁵O-water and ¹¹C-acetate, respectively) although a systematic bias was observed for both scanners (p < 0.001 for all). FSV based on ¹¹C-acetate and ¹⁵O-water correlated highly (r = 0.99, slope = 1.03) with no significant difference between FSV estimates (p = 0.14).

Conclusions

FSV can be obtained automatically using dynamic PET/CT and cluster analysis. Results are almost identical for ¹¹C-acetate and ¹⁵O-water. A scanner-dependent bias was observed, and a scanner calibration factor is required for multi-scanner studies. Generalization of the method to other tracers and scanners requires further validation.

Noninvasive Fractional Flow Reserve Derived from Coronary Computed Tomography Angiography for the Diagnosis of Lesion-specific Ischemia

Fractional flow reserve derived from coronary computed tomography angiography (FFR_CT) has emerged as a powerful tool for the assessment of flow-limiting coronary stenoses. To date, FFR_CT is the only noninvasive imaging modality for the depiction of lesion-specific ischemia and large prospective multicenter studies have established its high diagnostic value. The nature of FFR_CT allows the prediction of functional outcome of coronary stenting, which will expand the role of cardiac computed tomography in the evaluation and management of coronary artery disease.

Role of risk stratification by SPECT, PET, and hybrid imaging in guiding management of stable patients with ischaemic heart disease: expert panel of the EANM cardiovascular committee and EACVI

Risk stratification has become increasingly important in the management of patients with suspected or known ischaemic heart disease (IHD). Recent guidelines recommend that these patients have their care driven by risk assessment. The purpose of this position statement is to summarize current evidence on the value of cardiac single-photon emission computed tomography, positron emission tomography, and hybrid imaging in risk stratifying asymptomatic or symptomatic patients with suspected IHD, patients with stable disease, patients after coronary revascularization, heart failure patients, and specific patient population. In addition, this position statement evaluates the impact of imaging results on clinical decision-making and thereby its role in patient management. The document represents the opinion of the European Association of Nuclear Medicine (EANM) Cardiovascular Committee and of the European Association of Cardiovascular Imaging (EACVI) and intends to stimulate future research in this field.

Multimodality Imaging in Ischemic Cardiomyopathy

Cardiac multimodality (hybrid) imaging can be obtained from a variety of techniques, such as nuclear medicine with single photon emission computed tomography (SPECT) and positron emission tomography (PET), or radiology with multislice computed tomography (CT), magnetic resonance (MR) and echography. They are typically combined in a side-by-side or fusion mode in order to provide functional and morphological data to better characterise coronary artery disease, with more proven efficacy than when used separately. The gained information is then used to guide revascularisation procedures. We present an up-to-date comprehensive overview of multimodality imaging already in clinical use, as well as a combination of techniques with promising or developing applications.

Additional value of transluminal attenuation gradient in CT angiography to predict hemodynamic significance of coronary artery stenosis

OBJECTIVES

The current study evaluates the incremental value of transluminal attenuation gradient (TAG), TAG with corrected contrast opacification (CCO), and TAG with exclusion of calcified coronary segments (ExC) over coronary computed tomography angiogram (CTA) alone using fractional flow reserve (FFR) as the gold standard.

BACKGROUND

TAG is defined as the contrast opacification gradient along the length of a coronary artery on a coronary CTA. Preliminary data suggest that TAG provides additional functional information. Interpretation of TAG is hampered by multiple heartbeat acquisition algorithms and coronary calcifications. Two correction models have been proposed based on either dephasing of contrast delivery by relating coronary density to corresponding descending aortic opacification (TAG-CCO) or excluding calcified coronary segments (TAG-ExC).

METHODS

Eighty-five patients with intermediate probability of coronary artery disease were prospectively included. All patients underwent step-and-shoot 256-slice coronary CTA. TAG, TAG-CCO, and TAG-ExC analyses were performed followed by invasive coronary angiography in conjunction with FFR measurements of all major coronary branches.

RESULTS

Thirty-four patients (40%) were diagnosed with hemodynamically-significant coronary artery disease (i.e., FFR ≤0.80). On a per-vessel basis (n = 253), 59 lesions (23%) were graded as hemodynamically significant, and the diagnostic accuracy of coronary CTA (diameter stenosis ≥50%) was 95%, 75%, 98%, and 54% for sensitivity, specificity, negative predictive value, and positive predictive value, respectively. TAG and TAG-ExC did not discriminate between vessels with or without hemodynamically significant lesions (-13.5 ± 17.1 HU [Hounsfield units] × 10 mm(-1) vs. -11.6 ± 13.3 HU × 10 mm(-1), p = 0.36; and 13.1 ± 15.9 HU × 10 mm(-1) vs. -11.4 ± 11.7 HU × 10 mm(-1), p = 0.77, respectively). TAG-CCO was lower in vessels with a hemodynamically-significant lesion (-0.050 ± 0.051 10 mm(-1) vs. -0.036 ± 0.034 10 mm(-1), p = 0.03) and TAG-ExC resulted in a slight improvement of the net reclassification index (0.021, p < 0.05).

CONCLUSIONS

TAG did not provide incremental diagnostic value over 256-slice coronary CTA alone in assessing the hemodynamic consequences of a coronary stenosis. Correction for temporal nonuniformity of contrast delivery or exclusion of calcified coronary segments slightly enhanced the results.

Role of CT angiography for detection of coronary atherosclerosis

As laparoscopic surgery is replacing open surgery, similarly computed tomography angiography is replacing invasive conventional cardiac angiography. In the last century, marvelous efforts in research have improved strategies for cure, diagnosis and prevention of fatal human diseases; however, coronary artery disease, as the most prevalent cause of mortality and morbidity in the world, has remained a great challenge. Due to advancements in technology and research, it has become more simple and robust to diagnose and treat coronary artery disease (CAD) with minimal or no intervention, promising to not only diagnosis at an early stage but potential prevention altogether. While most with obvious CAD can be diagnosed easily and quickly with ECG, those identified as 'low risk' require more extensive testing to diagnose or rule out CAD. For example in emergency departments, low-risk patients with chest pain are diagnosed solely depending on history, ECG and blood testing for biomarkers. This approach has resulted in either delayed or miss-diagnosis of Acute coronary syndrome. To prevent this, many emergency departments now use protocols for low-risk heart patients that include cardiac stress tests and/or CT heart imaging. This review provides an overview of the current literature on the value of Computed tomography angiography and discusses how prognostic information obtained with Computed tomography angiography can be used to further integrate the technique into clinical practice.

Diagnosing coronary artery disease with hybrid PET/CT: it takes two to tango

The noninvasive diagnosis of coronary artery disease (CAD) is a challenging task. Although a large armamentarium of imaging modalities is available to evaluate the functional consequences of the extent and severity of CAD, cardiac perfusion positron emission tomography (PET) is considered the gold standard for this purpose. Alternatively, noninvasive anatomical imaging of coronary atherosclerosis with coronary computed tomography angiography (CCTA) has recently been successfully implemented in clinical practice. Although each of these diagnostic approaches has its own merits and caveats, functional and morphological imaging techniques provide fundamentally different insights into the disease process and should be considered to be complementary rather than overlapping. Hybrid imaging with PET/CT offers the possibility to evaluate both aspects nearly simultaneously, and studies have demonstrated that such a comprehensive assessment results in superior diagnostic accuracy, better prognostication, and helps in guiding clinical patient management. The aim of this review is to discuss the value of stand-alone CCTA and PET in CAD, and to summarize the available data on the surplus value of hybrid PET/CT including its strengths and limitations.