LAUSR

The ‘‘Guidelines in Review’’ series in this issue of the Journal of Nuclear Cardiology focuses on the comparison of the AHA/ACC and ESC guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. In spite of the fact that the AHA/ACC guidelines were published in 2006 (to be updated in the near future) and the ESC guidelines in 2015, there are relatively minor differences between their recommendations. This is true even after incorporating recommendations on sudden death prevention from more recent AHA/ACC guidelines on heart failure, implantable electronic devices, and congenital heart disease. The most substantive difference between the two guidelines relates to implantation of a primary prevention implantable cardiac defibrillator (ICD). Both the AHA/ ACC and ESC guidelines recommend consideration of an ICD in patients without other life-limiting comorbidities having ischemic and nonischemic class II and III congestive heart failures and a left ventricular ejection fraction (LVEF) less than or equal to 35%. This recommendation is based on several well-designed randomized clinical trials. The AHA/ACC guidelines also continue to recommend that primary prevention ICD therapy be considered in patients with functional class I congestive heart failure and a LVEF less than or equal to 30%. The latter recommendation is based on a single study, the MADIT II trial. Both guidelines are consonant in underscoring the importance of evaluating patients for underlying coronary artery disease. What is most notable from an imaging standpoint is that despite a difference of almost a decade in the publication of these two sets of guidelines, there has been no real evolution of methods for risk stratification beyond the assessment of LVEF. LVEF in itself has no pathophysiological basis for arrhythmogenesis (for ICD implantation) or ‘dyssynchrony’ (for resynchronization therapy). It is a simple ratio of end-systolic and end-diastolic volumes. While LVEF remains the ‘‘gold standard’’ to define the risk of sudden cardiac arrest (SCA) among patients with cardiomyopathy, there is a general lack of specifics on how it should actually be quantified in any of the guidelines, and many clinical decisions are still based on the subjective echocardiographic assessment of ventricular function. It needs to be emphasized that the clinical trials that form the basis of these guidelines allowed LVEF to be assessed from any imaging modality. This is a significant limitation of contemporary management, as it is well known that there are substantial variations in LVEF estimates between modalities. Studies have shown overestimation or underestimation of LVEF by invasive ventriculography and echocardiography, when using magnetic resonance imaging (MRI) as the gold standard. Similar differences have also been reported comparing LVEF measurements by cardiac MRI vs Reprint requests: Saurabh Malhotra, MD, MPH, FASNC, Departments of Medicine, Biomedical Engineering and Physiology & Biophysics, the VA WNY Health Care System and the Clinical and Translational Science Institute at the University at Buffalo, Buffalo, NY, [email protected] J Nucl Cardiol 2017;24:1904–8. 1071-3581/$34.00 Copyright 2017 American Society of Nuclear Cardiology.