Stress first myocardial perfusion imaging: Is it time to put to rest the “Rest First” strategy for most patients?

Abstract

While myocardial perfusion imaging (MPI) remains the most validated and extensively utilized modality in the evaluation and prognostication of coronary artery disease (CAD), it has come under unprecedented scrutiny in the past few years both due to the expansive growth of cardiac imaging and increasing concerns of patient radiation exposure over their lifetime. In one study, nuclear cardiac imaging was reported to be contributing up to 22% of radiation exposure amongst all imaging. Over the past few years, major cardiac societies such as the American College of Cardiology/American Heart Association in collaboration with many other imaging societies have taken proactive steps to guide the use of cardiac imaging. Appropriate use criteria for nuclear cardiology, echocardiography, CT/MRI, and most recently, cardiac catheterization and percutaneous coronary interventions have been published to ensure that clinicians in most instances are ‘‘doing the right test for the right patient at the right time.’’ Specifically ASNC has been a leader in this effort and has taken numerous initiatives including publication of important documents with practical importance in JNC toward educating physicians regarding the appropriate use of MPI. The recent comprehensive ASNC preferred practice statement, ‘‘Patient Centered Imaging’’ by Depuey et al outlines various MPI protocols with existing isotopes and their advantages disadvantages and best use in daily clinical practice. This document reiterates an important point which physicians practicing nuclear cardiology should embrace namely ‘‘One size does not fit all.’’ Most nuclear laboratories perform single day lowdose rest-first, followed by high-dose stress imaging. This enables higher count statistics in the stress portion enabling better images and reliable gating but comes with the disadvantage of lasting about 4 hours and delivering a cumulative radiation dose of 12-15 mSv for a standard 10/30 mCi rest-stress Tc-99m MPI scan. Some laboratories, however, have been successfully performing stress first imaging (SFI) protocol where a ‘‘normal’’ stress obviates the need for the rest portion [converting the nuclear scan essentially to a stress-only imaging (SOI)]. SFI/SOI protocols have recently been shown to be very safe and feasible as compared with a normal stress-rest scan or a normal rest-stress scan. These studies have enrolled over 16,000 patients and have demonstrated excellent comparable results both for interpretability and a very favorable prognosis extending to over 4.5 years follow up. The concept of SFI/SOI imaging is extremely attractive especially when taken in the context that over 70% of MPI studies performed in nuclear labs are interpreted as ‘‘normal’’; thus, a substantial portion of rest studies performed could be avoided and by doing so the advantages are obvious. For a nuclear physician to conclusively label a stress study normal and avoid the rest scan, the study as a whole must be ‘‘completely normal’’ including the stress perfusion images, gated imaging parameters such as ejection fraction ([50%), cavity size, and wall motion. Furthermore, stress ECG and planar images must be reviewed, and attenuation correction (AC) or prone imaging should be used if available as an adjunct for the stress study. AC enhances the confidence of the reader to call the stress portion normal as approximately 50-78% of non-attenuation-corrected images have artifacts. This constellation of findings in a SFI study eliminates the need for a rest study and makes it a SOI study. From the Heart and Vascular Institute, Henry Ford Hospital, Detroit, MI. Research grant support/speakers bureau: Astellas Pharma US Inc (KA), Lantheus Medical Imaging. Reprint requests: Karthik Ananthasubramaniam, MD, FACC, FASE, FASNC, FRCP(Glas), Heart and Vascular Institute, Henry Ford Hospital, K-14, Detroit, MI 48202; kananth1@hfhs.org. J Nucl Cardiol 2012;19:1106–9. 1071-3581/$34.00 Copyright 2012 American Society of Nuclear Cardiology. doi:10.1007/s12350-012-9623-9