Brian G. Abbott

Single photon-emission computed tomography

The current document is an update of an earlier version of single photon emission tomography (SPECT) guidelines that was developed by the American Society of Nuclear Cardiology. Although that document was only published a few years ago, there have been significant advances in camera technology, imaging protocols, and reconstruction algorithms that prompted the need for a revised document. This publication is designed to provide imaging guidelines for physicians and technologists who are qualified to practice nuclear cardiology. While the information supplied in this document has been carefully reviewed by experts in the field, the document should not be considered medical advice or a professional service. We are cognizant that SPECT technology is evolving rapidly and that these recommendations may need further revision in the near future. Hence, the imaging guidelines described in this publication should not be used in clinical studies until they have been reviewed and approved by qualified physicians and technologists from their own particular institutions. 2. INSTRUMENTATION QUALITY ASSURANCE AND PERFORMANCE

Failure to Improve Left Ventricular Function After Coronary Revascularization for Ischemic Cardiomyopathy Is Not Associated With Worse Outcome

Background-Preoperative identification of viable myocardium in patients with ischemic cardiomyopathy is considered important because CABG can result in recovery of left ventricular (LV) function. However, the hypothesis that lack of improvement of LV function after CABG is associated with poorer patient outcome is untested. Methods and Results-Outcome was compared in patients with ischemic LV dysfunction (LVEF </=0.30) with and without improvement in LVEF after CABG. Of 135 consecutive patients, 128 (95%) survived CABG and 104 (77%) had pre- and post-CABG LVEF assessment. Of these 104 patients, 68 (65%) had >0.05 increase in LVEF (group A) and 36 (35%) had no significant change, or </=0.05 decrease in LVEF (group B) compared with pre-CABG LVEF. No significant differences existed in age, gender, comorbidities, baseline symptoms, baseline LVEF, or intraoperative variables between groups A and B. Group A increased LVEF from 0.24+/-0.05 to 0.39+/-0.1 (P<0.005). In Group B, LVEF did not change significantly postoperatively, 0.24+/-0.05 to 0.23+/-0.06 (P=NS). Postoperative improvement in angina and heart failure scores were similar between the 2 groups. Survival free of cardiac death was similar for both groups (93% in group A and 94% in group B, P=NS) at a mean follow-up of 32+/-23 months. Conclusions-Lack of improvement of global LVEF after CABG is not associated with poorer outcome compared with that of patients with improved LVEF, presumably because effective revascularization of ischemic myocardium, even without improvement in ventricular function, protects against future infarction and death.

The role of radionuclide myocardial perfusion imaging for asymptomatic individuals.

Radionuclide myocardial perfusion imaging (RMPI) has served as a clinical mainstay in the management of patients with known or suspected coronary artery disease (CAD) for more than two decades. RMPI provides information beyond the mere detection of disease, delineating the extent, severity, and location of perfusion abnormalities. These data also have important prognostic implications and assist in providing reassurance to the clinician and patient or suggest the need for additional therapies. However, the role of RMPI among asymptomatic patients is less defined than among those with active symptoms. Furthermore, in keeping with the recent emphasis on improved resource utilization, costcontainment, and reduction of radiation exposure, the American Society of Nuclear Cardiology (ASNC) has commissioned a review of evidence for the use of RMPI specifically for asymptomatic individuals in an attempt to provide guidance for clinicians. The notation of symptomatic status remains a challenge since this designation is largely given to patient exhibiting chest pain suggestive of myocardial ischemia. Other symptoms such as dyspnea or syncope are often assigned to those without symptoms (i.e., no chest pain). For these patients with atypical presentations, the symptom burden places them at an elevated risk and may require additional assessment even though they may not have chest pain. Additionally, ischemic-type abnormalities on a resting electrocardiogram (ECG) connote an increased risk of cardiac events. The most recent Appropriate Use Criteria for Cardiac Radionuclide Imaging document discriminates between asymptomatic patients and those with an ischemic equivalent, the latter including chest pain, anginal equivalents, or an abnormal ECG. The goal of this Information Statement is to define instances when the additional evaluation of asymptomatic patients may offer useful clinical information. In contrast, the elimination of the use of RMPI in patient groups where no benefit may be garnered serves as an important means to reduce radiation exposure.

The emerging role of the selective A2A agonist in pharmacologic stress testing

Since its inception almost 50 years ago, the technique of myocardial perfusion imaging has evolved substantially. From pyrophosphate to Tl-201 to technetium-based radiotracers, from static planar imaging to gated SPECT with attenuation correction, the field of nuclear cardiology has matured with these significant technical advances. Similarly, the use of pharmacologic stressors as an alternative to exercise has also been in a state of evolution, from dipyridamole and dobutamine to adenosine, to a novel agent recently approved and available for use. This review will highlight recent developments in pharmacologic stress myocardial perfusion imaging focusing on the clinical application of the selective adenosine A2A receptor agonists.

Nuclear Cardiology in the Evaluation of Acute Chest Pain in the Emergency Department

Only a minority of patients presenting to the emergency department (ED) with acute chest pain will eventually be diagnosed with an acute coronary syndrome. The majority will have an electrocardiogram that is normal or nondiagnostic for acute myocardial ischemia or infarction. Typically, these patients are admitted to exclude myocardial infarction despite a very low incidence of coronary artery disease. However, missed myocardial infarctions in patients who are inadvertently sent home from the ED have significant adverse outcomes and associated legal consequences. This leads to a liberal policy to admit patients with chest pain, presenting a substantial burden in terms of cost and resources. Many centers have developed chest pain centers, using a wide range of diagnostic modalities to deal with this dilemma. We discuss the methods currently available to exclude myocardial ischemia and infarction in the ED, focusing on the use of myocardial perfusion imaging as both an adjunct and an alternative to routine testing. We review the available literature centering on the ED evaluation of acute chest pain and then propose an algorithm for the practical use of nuclear cardiology in this setting.

Myocardial perfusion imaging in women for the evaluation of stable ischemic heart disease—state-of-the-evidence and clinical recommendations

This document from the American Society of Nuclear Cardiology represents an updated consensus statement on the evidence base of stress myocardial perfusion imaging (MPI), emphasizing new developments in single-photon emission tomography (SPECT) and positron emission tomography (PET) in the clinical evaluation of women presenting with symptoms of stable ischemic heart disease (SIHD). The clinical evaluation of symptomatic women is challenging due to their varying clinical presentation, clinical risk factor burden, high degree of comorbidity, and increased risk of major ischemic heart disease events. Evidence is substantial that both SPECT and PET MPI effectively risk stratify women with SIHD. The addition of coronary flow reserve (CFR) with PET improves risk detection, including for women with nonobstructive coronary artery disease and coronary microvascular dysfunction. With the advent of PET with computed tomography (CT), multiparametric imaging approaches may enable integration of MPI and CFR with CT visualization of anatomical atherosclerotic plaque to uniquely identify at-risk women. Radiation dose-reduction strategies, including the use of ultra-low-dose protocols involving stress-only imaging, solid-state detector SPECT, and PET, should be uniformly applied whenever possible to all women undergoing MPI. Appropriate candidate selection for stress MPI and for post-MPI indications for guideline-directed medical therapy and/or invasive coronary angiography are discussed in this statement. The critical need for randomized and comparative trial data in female patients is also emphasized.

Radiation Safety in Children with Congenital and Acquired Heart Disease: A Scientific Position Statement on Multimodality Dose Optimization from the Image Gently Alliance

There is a need for consensus recommendations for ionizing radiation dose optimization during multimodality medical imaging in children with congenital and acquired heart disease (CAHD). These children often have complex diseases and may be exposed to a relatively high cumulative burden of ionizing radiation from medical imaging procedures, including cardiac computed tomography, nuclear cardiology studies, and fluoroscopically guided diagnostic and interventional catheterization and electrophysiology procedures. Although these imaging procedures are all essential to the care of children with CAHD and have contributed to meaningfully improved outcomes in these patients, exposure to ionizing radiation is associated with potential risks, including an increased lifetime attributable risk of cancer. The goal of these recommendations is to encourage informed imaging to achieve appropriate study quality at the lowest achievable dose. Other strategies to improve care include a patient-centered approach to imaging, emphasizing education and informed decision making and programmatic approaches to ensure appropriate dose monitoring. Looking ahead, there is a need for standardization of dose metrics across imaging modalities, so as to encourage comparative effectiveness studies across the spectrum of CAHD in children.

The vasodilator stress ECG: Should depression cause anxiety?

For more than a century, the resting electrocardiogram (ECG) has endured as the cornerstone in the diagnosis of cardiac disease. The information provided from the modern day version of Einthoven’s string galvanometer remains at times more useful than other more sophisticated technology, as evidenced by its central role in the management of acute chest pain, with the decision to pursue a reperfusion strategy based almost exclusively on the presence of diagnostic ECG findings. The ECG also provides us with important information regarding the potential presence of coronary artery disease (CAD) and ischemia when interpreted during exercise and pharmacologic stress testing. While a very sensitive instrument, it suffers from a lack of specificity and consequent false positive results. As newer modalities to assess myocardial ischemia with imaging have evolved, diagnostic accuracy has increased, and many studies have demonstrated that imaging adds both incremental diagnostic and prognostic information to that predicted by the clinical data and ECG alone. Ischemic ECG changes during exercise stress testing have been demonstrated to provide additional prognostic information in the setting of perfusion abnormalities, but considered as ‘‘false-positive’’ when perfusion images are normal. Similar to exercise stress, stress ECG changes during pharmacologic stress can also be important. However, the diagnostic and prognostic significance of vasodilatorinduced ischemic ECG changes in the setting of normal perfusion is less certain, as previous studies of this unique finding have demonstrated discordant results. In this issue of the Journal of Nuclear Cardiology, Azemi et al from Hartford Hospital and the University of Connecticut, School of Medicine provide us with further insight into the clinical implications of ischemic ECG changes during vasodilator stress. In a retrospective analysis of more than 5,000 patients undergoing pharmacologic stress myocardial perfusion imaging (MPI) with either dipyridamole or adenosine over a 14-year period, the authors identified a diagnostic cohort of 622 patients with no prior history of myocardial infarction (MI) or coronary artery bypass surgery (CABG) and no baseline ECG abnormalities who underwent coronary angiography within 90 days of MPI. Another 3,566 patients with no history of prior MI or CABG and without baseline ECG abnormalities who underwent vasodilator stress served as a prognostic cohort, with a mean follow-up of two and half years evaluating for cardiac death and nonfatal MI. The presence of STsegment depression during vasodilator stress ECG changes was associated with an increased incidence of significant CAD in patients with concomitant perfusion abnormalities, but not in patients with normal perfusion images. When evaluating all patients in the study, ischemic ECG changes were not predictive of outcome, regardless of the MPI result. The authors conclude that the presence of ECG changes with vasodilator stress is of minimal diagnostic or prognostic significance. This study adds to a growing body of literature that has focused on furthering our understanding of the role of the stress ECG during vasodilator stress. Previous reports have varied in terms of inclusion criteria, and patient selection with respect to MI or CABG, exclusion of baseline ECG abnormalities, and the type of vasodilator stress agent(s) used. Table 1 summarizes the present study findings along with prior studies which have evaluated this observation with respect to associated impact on outcomes. One notable difference is that studies that included patients with known CAD, prior MI, and/or revascularization tended to find a higher adverse cardiac event rate during follow-up. Interestingly, while discordant in other aspects, a recurrent and rather provocative theme in all these studies is the much higher incidence of ST-segment depression with normal MPI in women than in men. Almost every study evaluating the significance of vasodilator stress ECG changes in association with normal MPI has found that that C80% of the patients with this finding were women. As noted by the authors, the high rate of CAD (30%-40%) found on catheterization in the diagnostic cohort was likely driven by referral bias, in that patients referred for angiography with normal perfusion were From the Rhode Island Hospital, Brown University, Providence, RI. Reprint requests: Brian G. Abbott, MD, FACC, FASNC, FAHA, Rhode Island Hospital, Brown University, Providence, RI; babbott@lifespan.org. J Nucl Cardiol 2012;19:13–5. 1071-3581/

Noninvasive cardiac imaging in the evaluation of suspected acute coronary syndromes.

34.00 Copyright 2011 American Society of Nuclear Cardiology. doi:10.1007/s12350-011-9478-5

Contemporary Cardiac SPECT Imaging—Innovations and Best Practices: An Information Statement from the American Society of Nuclear Cardiology

Optimal management of patients presenting with chest pain to the emergency department is a major challenge, both in terms of a diagnostic dilemma and consumption of resources. The triage of such patients can be aided vastly by the appropriate use of noninvasive imaging. Noninvasive imaging modalities such as echocardiogram, radionuclide perfusion studies, positron emission tomography, cardiac magnetic resonance imaging and computed tomography have all been demonstrated to have favorable diagnostic and prognostic value, with an enhanced sensitivity to detect acute ischemia. A normal noninvasive evaluation in the appropriate clinical setting presents a strong argument against acute ischemia as an etiology of the chest pain. Randomized trials of both rest and stress imaging in the emergency department have confirmed a reduction in unnecessary hospitalizations and cost savings without compromising the safety of the patient. Cardiac magnetic resonance and computed tomography would provide an insight into subendocardial ischemia, the detection of which has previously been difficult, using single-photon emission tomography and echocardiography. In this review, novel hot-spot imaging modalities are discussed including infarct-avid imaging agents and ischemia-avid imaging agents, thus elucidating the pathophysiology of reperfusion-induced cell death. These agents represent work in evolution and are likely to be used routinely in the future as understanding of coronary syndromes and coronary artery disease becomes clearer.