Fernanda Erthal

Clinical PET Myocardial Perfusion Imaging and Flow Quantification

Cardiac PET imaging is a powerful tool for the assessment of coronary artery disease. Many tracers with different advantages and disadvantages are available. It has several advantages over single photon emission computed tomography, including superior accuracy and lower radiation exposure. It provides powerful prognostic information, which can help to stratify patients and guide clinicians. The addition of flow quantification enables better detection of multivessel disease while providing incremental prognostic information. Flow quantification provides important physiologic information, which may be useful to individualize patient therapy. This approach is being applied in some centers, but requires standardization before it is more widely applied.

Eight-year follow-up of the Clopidogrel After Surgery for Coronary Artery Disease (CASCADE) trial

Objective In this 8 years’ follow‐up study, we evaluated the long‐term outcomes of the addition of clopidogrel to aspirin during the first year after coronary artery bypass grafting, versus aspirin plus placebo, with respect to survival, major adverse cardiac, or major cerebrovascular events, including revascularization, functional status, graft patency, and native coronary artery disease progression. Methods In the initial Clopidogrel After Surgery for Coronary Artery Disease trial, 113 patients were randomized to receive either daily clopidogrel (n = 56) or placebo (n = 57), in addition to aspirin, in a double‐blind fashion for 1 year after coronary artery bypass grafting. All patients were re‐evaluated to collect long‐term clinical data. Surviving patients with a glomerular filtration rate > 30 mL/min were asked to undergo a coronary computed tomography angiogram to evaluate the late saphenous vein graft patency and native coronary artery disease progression. Results At a median follow‐up of 7.6 years, survival rate was 85.5% ± 3.8% (P = .23 between the 2 groups). A trend toward enhanced freedom from all‐cause death or major adverse cardiac or cerebrovascular events, including revascularization, was observed in the aspirin‐clopidogrel group (P = .11). No difference in functional status or freedom from angina was observed between the 2 groups (P > .57). The long‐term patency of saphenous vein graft was 89.11% in the aspirin‐clopidogrel group versus 91.23% in the aspirin‐placebo group (P = .79). A lower incidence of moderate to severe native disease progression was observed in the aspirin‐clopidogrel group versus the aspirin‐placebo group (7 out of 122 vs 13 out of 78 coronary segments that showed progression, respectively [odds ratio, 0.3 ± 0.2; 95% confidence interval, 0.1‐0.8; P = .02]). Conclusions At 8 years’ follow‐up, the addition of clopidogrel to aspirin during the first year after coronary artery bypass grafting exhibited a lower incidence of moderate to severe progression of native coronary artery disease and a trend toward higher freedom from major adverse cardiac or cerebrovascular events, including revascularization, or death in the aspirin‐clopidogrel group. Clinical Trial Registration http://www.clinicaltrials.gov. Unique identifier: NCT00228423.

Molecular Imaging for the diagnosis of infective endocarditis: A systematic literature review and meta-analysis

BACKGROUND Infective endocarditis (IE) is a serious, potentially life-threatening condition. Currently, the modified Duke criteria is used to assist with the diagnosis of IE, but it can still remain difficult. Growing data supports the potential use of molecular imaging to assist in the diagnosis of IE. Our objective was to understand the potential utility of 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography-computed tomography (PET-CT), 67Ga citrate and radiolabeled white blood cell (WBC) scintigraphy in the diagnosis of IE. METHODS AND RESULTS A systematic review of the literature and meta-analysis on the use of all 3 modalities in IE was conducted. The literature search identified 2753 articles. A total of 14 studies met the inclusion criteria (10 for 18F-FDG, 3 for WBC and 1 for both modalities). No 67Ga citrate study met the inclusion criteria. Pooled sensitivity of 18F-FDG studies with adequate cardiac preparation for the diagnosis of IE was 81% (95% CI, 73%-86%) and pooled specificity was 85% (95% CI, 78%-91%). There was good overall accuracy with an area under the curve (AUC) of 0.897. Pooled sensitivity of WBC for the diagnosis of IE was 86% (95% CI, 77%-92%) and pooled specificity was 97% (95% CI, 92%-99%). The overall accuracy of WBC was excellent with an AUC of 0.957. CONCLUSIONS Both 18F-FDG and WBC have good sensitivity, specificity and accuracy for the diagnosis of IE. Both modalities are useful in the investigation of IE, and should be considered in cases where the diagnosis is uncertain.

The role of nuclear cardiac imaging in risk stratification of sudden cardiac death

Sudden cardiac death (SCD) represents a significant portion of all cardiac deaths. Current guidelines focus mainly on left ventricular ejection fraction (LVEF) as the main criterion for SCD risk stratification and management. However, LVEF alone lacks both sensitivity and specificity in stratifying patients. Recent research has provided interesting data which supports a greater role for advanced cardiac imaging in risk stratification and patient management. In this article, we will focus on nuclear cardiac imaging, including left ventricular function assessment, myocardial perfusion imaging, myocardial blood flow quantification, metabolic imaging, and neurohormonal imaging. We will discuss how these can be used to better understand SCD and better stratify patient with both ischemic and non-ischemic cardiomyopathy.

Real-time cardiac magnetic resonance cine imaging with sparse sampling and iterative reconstruction for left-ventricular measures: Comparison with gold-standard segmented steady-state free precession.

BACKGROUND Segmented cine imaging with a steady-state free-precession sequence (Cine-SSFP) is currently the gold standard technique for measuring ventricular volumes and mass, but due to multi breath-hold (BH) requirements, it is prone to misalignment of consecutive slices, time consuming and dependent on respiratory capacity. Real-time cine avoids those limitations, but poor spatial and temporal resolution of conventional sequences has prevented its routine application. We sought to examine the accuracy and feasibility of a newly developed real-time sequence with aggressive under-sampling of k-space using sparse sampling and iterative reconstruction (Cine-RT). METHODS Stacks of short-axis cines were acquired covering both ventricles in a 1.5T system using gold standard Cine-SSFP and Cine-RT. Acquisition parameters for Cine-SSFP were: acquisition matrix of 224×196, temporal resolution of 39ms, retrospective gating, with an average of 8 heartbeats per slice and 1-2 slices/BH. For Cine-RT: acquisition matrix of 224×196, sparse sampling net acceleration factor of 11.3, temporal resolution of 41ms, prospective gating, real-time acquisition of 1 heart-beat/slice and all slices in one BH. LV contours were drawn at end diastole and systole to derive LV volumes and mass. RESULTS Forty-one consecutive patients (15 male; 41±17years) in sinus rhythm were successfully included. All images from Cine-SSFP and Cine-RT were considered to have excellent quality. Cine-RT-derived LV volumes and mass were slightly underestimated but strongly correlated with gold standard Cine-SSFP. Inter- and intra-observer analysis presented similar results between both sequences. CONCLUSIONS Cine-RT featuring sparse sampling and iterative reconstruction can achieve spatial and temporal resolution equivalent to Cine-SSFP, providing excellent image quality, with similar precision measurements and highly correlated and only slightly underestimated volume and mass values.

Appropriate Use Criteria for Cardiac Computed Tomography: Does Computed Tomography Have Incremental Value in All Appropriate Use Criteria Categories?

Purpose: Cardiac imaging expenditures have come under scrutiny, and a focus on appropriate use criteria (AUC) has arisen to ensure cost-effective resource utilization. Although AUC has been developed by clinical experts, it has not undergone rigorous quality assurance testing to ensure that inappropriate indications for testing yield little clinical benefit. The objective of the study was to evaluate the potential incremental prognostic value of coronary computed tomographic angiography (CCTA) in the different AUC categories. Materials and Methods: Consecutive patients enrolled into a cardiac CT Registry were collated. Patient indications were reviewed and based on the 2010 AUC (appropriate, uncertain, and inappropriate). Patients were followed-up for death, myocardial infarction (MI), and late revascularization, with the primary composite endpoint being cardiac death, nonfatal MI, and late revascularization. The prognostic value of CCTA over clinical variables in each of the AUC categories was assessed. Results: Indications for CCTA were appropriate, uncertain, and inappropriate in 1284 (66.5%), 312 (16.2%), and 334 (17.3%) patients, respectively. Rates of all-cause of death, cardiac death, nonfatal MI, and late revascularization were similar across patients with appropriate, uncertain, and inappropriate indications for CCTA. Moreover, in each AUC category, CCTA had incremental prognostic value over a routine clinical risk score (National Cholesterol Education Program) with hazard ratios of 9.98, 7.39, and 5.61. Conclusions: CCTA has incremental prognostic value in all AUC categories, even when the reason for the study was deemed “inappropriate.” This suggests that CCTA may still have clinical value in “inappropriate” indications and that further quality assurance AUC studies are needed.

False-positive stress PET–CT imaging in a patient with interstitial injection

An 83-year-old male with 2-year history of central chest tightness with exertion presented to our nuclear cardiology center for dipyridamole rubidium-82 positron emission (Rb PET) computed tomography (CT). His risk factors included poorly controlled type 2 diabetes, dyslipidemia, and hypertension. Past clinical investigation showed normal echocardiogram and normal singlephoton emission computed tomography myocardial perfusion imaging (MPI) two and four years ago, respectively. Patient underwent a dipyridamole Rb PET-CT (Discovery 690, GEHC) MPI study to assess for ischemia. Low-dose CT for attenuation correction (AC) was performed before the PET scans. The right antecubital vein was used for tracer injection both at rest and during stress phases. Cardiac-gated rest/stress images were reconstructed from the list-mode data using routine ECG triggers. Initial analysis of the stress perfusion images demonstrated a completely reversible moderate-size defect from base to mid-anterior wall suggestive of an area of ischemia in the left anterior descending artery, although unusual in its location in that it spared the anteroapical wall and apex (Figure 1a). Review of the fused Rb PET-CT images confirmed that the AC alignment was correct but showed an area of intense focal uptake in the right axillary region (i.e., right axillary lymph node), which was more prominent in the stress images (Figure 2, yellow arrows). A complete absence of physiological background activity in the transaxial planes adjacent to this hotspot was suggestive of an artifact consistent with overcorrection of the scatter background. After repeating the image reconstruction with an upper limit applied to the scale of the scatter correction, normal tracer uptake was observed in all myocardial segments (Figure 1b). This ‘scatter limit’ setting is a retrospective reconstruction option on the current Discovery PET-CT scanners (GE HealthCare, Waukesha, WI). This case demonstrates the importance of reviewing all acquired data including fused PET-CT images, and to be suspicious of artifacts when nonphysiological distribution of tracer uptake is observed. Scatter correction for 3D PET typically requires the estimation of a scale factor for accurate subtraction of the calculated scatter projections. This estimate can be biased in cases when there is substantial tracer activity outside the scanner field of view or outside the body contour, creating inconsistency in the true vs. calculated scatter background. The reporting physician should be cognizant of the presence of such artifacts as it can lead to misinterpretation of the PET study, and impact upon patient management.

Quantification of Myocardial Blood Flow with CZT SPECT Imaging: Is It Ready for Clinical Use?

Purpose of ReviewMyocardial blood flow (MBF) quantification with positron emission tomography (PET) is well validated and has established diagnostic and prognostic value for patient management. New cardiac dedicated solid-state single-photon emission tomography (SPECT) cameras using cadmium-zinc-telluride (CZT) crystals have better temporal and spatial resolution and increased count sensitivity than conventional SPECT systems and can measure MBF. We review recent validation studies using CZT technology for measurement of MBF and assess its readiness for clinical application.Recent FindingsOne preclinical study showed the accuracy of MBF measured using the CZT technology and conventional radiotracers versus microsphere data. Clinical studies have demonstrated the feasibility in patients and excellent correlations with coronary angiography and flow-wire studies, and PET imaging.SummaryMeasurement of MBF is possible with SPECT CZT systems and has been validated. Further studies are necessary to confirm the incremental value of MBF measurements with SPECT CZT to standard relative perfusion imaging for diagnostic accuracy and risk stratification.

The Journey of International Fellows: Have you been to America?

At the recent meetings of ASNC in Washington DC and ICNC in Madrid Spain, I was reminded of the power of networking: a chance to share with colleagues, learn the latest approaches, new evidence and developments, reassurance that we all have similar challenges and also the camaraderie, much of which stems from our days as fellows. This year I was particularly struck and moved by seeing past fellows (our program and others) who have succeeded and are now on the podium, writing papers, directing labs, even editing journals! This gave me to reflect on the journey of fellowship to investigator particularly for those of us from outside the US. Why is having ‘Been to America’ or now-a-days ‘Been to North America’ or ‘Been to Europe’ such a right of passage? Why do we engage and value this international exchange? The majority of new knowledge in cardiovascular care has emerged from academic centers particularly in the so-called ‘developed world.’ Research requires resources. These resources include funding, infrastructure, human capacity, skill, and time. Societies must carry a view that it is a long-term investment whose benefits may not be realized for years to come. In Jared Diamond’s book ‘‘Guns, Germs and Steel,’’ he identifies that there are regions in the world with more ‘cargo’ that reflect many environmental forces beyond our control. He also notes that innovation is driven in part by necessity and in part by curiosity. Societies with limited resources must focus more on immediate essentials and are less likely to lead advancements. At the same time, societies where mutual exchange occurs can accelerate advancement for each other. Finally, he points out that while resources may vary, intelligence and curiosity are ubiquitous. If resources are provided, advances can occur anywhere. When we enable international fellowship, we enable an exchange that will augment advances in medicine (and all fields) and patient care in our own countries and around the world. So what of the current environment for fellows wanting to pursue academic careers at home or abroad? A recent survey by the American College of Cardiology (ACC) suggested that 7-10% of early career cardiologists are ‘academic.’ Among the top reasons for an academic career path were the academic environment, desire to teach, desire to do research, and the ability to ‘‘do greater good.’’ The most important contributing factors to success were onsite mentoring, institutional resources, institutional commitment, and connections with collaborators. The mentor influence, researchoriented programs, and research protected time have direct impact on academic career choice and success. The most important challenge, on the other hand, for stable academic careers, not surprisingly, is diminishing research funds from government, NGOs, and industry. As per the quote that leads this editorial, it takes a team to train a fellow. This team includes the immediate team of the site institution but also the community team in the field as a whole. As such not only do we have an obligation locally but also globally to create vehicles for fellows success through mentoring, creating opportunities for presentation and publication and advocating for increased funding and support for young investigators careers which is clearly an investment in our future. But we must not forget the personal sacrifice that fellows make when they move to new cities, environments, and countries. How many of us from abroad have disaster stories of our transitions from our home countries to the USA for fellowship? For myself, we faced too many perils en route to mention, almost comical now in retrospect, but nerve-wracking at the time and Reprint requests: Rob Beanlands, MD, Division of Cardiology, Department of Medicine, National Cardiac PET Centre, University of Ottawa Heart Institute, Ottawa, Canada; rbeanlands@ottawaheart.ca J Nucl Cardiol 2015;22:1161–2. 1071-3581/

Myocardial Viability: From PARR-2 to IMAGE HF - Current Evidence and Future Directions

34.00 Copyright 2015 American Society of Nuclear Cardiology.