Review ArticleUtility of nuclear cardiovascular imaging in the cardiac intensive care unit
Introduction
The contemporary Cardiac Intensive Care Unit (CICU) has evolved into a complex unit that admits a heterogeneous mix of patients with a wide range of acute cardiovascular diseases often complicated by multi-organ failure.1 Although electrocardiography (ECG) and echocardiography are well-established as the first-line diagnostic modalities for assessing patients in the CICU, nuclear cardiology imaging when appropriate 2,3 has emerged as a useful adjunctive diagnostic modality in the management of these complex patients. The diagnostic versatility of nuclear imaging, along with relatively short acquisition time, minimal need for patient cooperation, independence of renal and hepatic function, and the lack of interference with cardiac devices make this a useful and safe imaging modality in the CICU. (Figure 1) 4, 5, 6, 7, 8 In addition to the utility of nuclear myocardial perfusion and viability imaging in the ischemic heart, advances in molecular imaging have enabled clinicians to accurately diagnose and promptly initiate therapies, often without the need for cardiac biopsy, for inflammatory and infiltrative cardiomyopathies such as cardiac amyloidosis and sarcoidosis. These are now considered common clinical entities that enter the differential diagnosis of patients in the CICU. The utility of such advances has extended to the management of patients with suspected infective endocarditis and inflammatory aortopathies. The following is a review on the modern uses of nuclear cardiology imaging in the management of critically ill patients admitted to the CICU.
Section snippets
Nuclear myocardial perfusion, metabolic imaging and ischemic heart disease in the CICU
Ischemic heart disease (IHD) is highly prevalent in the CICU with a wide range of clinical presentations including acute coronary syndromes (ACS), ventricular tachycardia (VT) and cardiogenic shock, or a combination of them.9 The decision to revascularize patients with multi-vessel coronary artery disease (CAD) including total occlusions, and severely depressed LVEF is often challenging. In such scenarios, the following questions commonly arise: (1) Is the current presentation driven by
Nuclear imaging in the management of ventricular tachycardia in the CICU
Ventricular tachycardia (VT) is frequently encountered in the CICU, often complicating heart failure exacerbations, cardiogenic shock or acute coronary syndromes. Although IHD is the most common cause of VT, the causes and underlying VT mechanism are diverse.33 Monomorphic VT is typically associated to structural heart disease with underlying myocardial scarring, while polymorphic VT and ventricular fibrillation (VF) are rather associated to myocardial ischemia, myocarditis, profound
Nuclear imaging in the evaluation of advanced atrioventricular block in the CICU
High-degree atrioventricular block (AVB) when associated to hemodynamic instability or unstable escape rhythm mandates admission to the CICU with the implantation of a temporary pacemaker.39 The causes of high-degree AVB are diverse including progression of degenerative conduction disease, acute coronary syndrome, myocarditis, sarcoidosis, medication-induced among others.40 Beyond the implantation of temporary pacemaker if clinically indicated, the ultimate management of these patients in the
Nuclear imaging in the assessment of cardiomyopathy of unknown etiology in the CICU
A large proportion of patients are admitted to the CICU for medical optimization of cardiogenic shock or low output state. The identification of reversible causes and drivers of decompensation is of utmost relevance in order to guide short- and long-term therapeutics. In this setting, MPI is particularly helpful as ischemia is often the precipitating factor. On other occasions, it can help determine when patients have reached end stage ischemic cardiomyopathy with large burden of scar and thus
Nuclear imaging in the management of infective endocarditis and aortitis in the CICU
Infective endocarditis (IE) is commonly encountered in the CICU, particularly when there is associated valve destruction with hemodynamic decompensation or septic shock. IE is a clinical diagnosis guided by the Duke criteria,42 nevertheless often the diagnosis remains elusive or non-definitive after the initial clinical evaluation.
Cardiac/whole body F18-FDG PET/CT imaging following the same dietary preparation as for sarcoid protocol is of adjunctive diagnostic and prognostic value in the
Conclusion
As the contemporary CICU continues to evolve into more complex units caring for sicker patients, the role of nuclear cardiovascular imaging will continue to grow. The versatility, safety and accuracy of radionuclide imaging of cardiovascular perfusion, function, metabolism, and inflammation uniquely elucidate pathophysiologic mechanisms of cardiac disease and direct timely, appropriate and effective medical, revascularization and immunosuppressive therapies to optimize patient-centered care and
Disclosures
Aldo L. Schenone, Erika Hutt, Paul Cremer, and Wael A. Jaber have nothing to disclose.
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All editorial decisions for this article, including selection of reviewers and the final decision, were made by guest editor Saurabh Malhotra, MD, MPH.