Single injection, double acquisition: a double-edged sword?

Abstract

In the clinical arena detection of myocardial viability is currently based on the use of nuclear techniques, which show preserved tracer uptake and metabolism in viable myocardium [1, 2]. Assessment of myocardial viability and ischemia continues to be an issue in patients with coronary artery disease and left ventricular dysfunction, in particular in patients following a myocardial infarction [3]. Nuclear imaging has long played an important role in this field. Especially PET imaging using 18F-fluorodeoxyglucose (FDG-PET) has been regarded as the metabolic gold standard of tissue viability, which has been supported by a wide clinical experience [4]. Viability assessment using SPECT techniques has gained more wide-spread clinical acceptance than PET, because it is more widely available at lower cost [5]. Moreover, technical advances in SPECT technology such as gated SPECT imaging further improve the diagnostic accuracy of the test [6–9]. During the past decade progress in the field of myocardial perfusion imaging has resulted in a myriad of choices for perfusion imaging protocols, including choices in types of stressor, imaging modality, perfusion tracer, method of analysis, and a wide range of choices of imaging protocols [10–12]. More recently, the peculiar contribution of gated SPECT in the assessment of myocardial ischemia and viability has been demonstrated, with the potential to evaluate in a single myocardial perfusion study the presence of preserved tracer uptake and the amount of contractile reserve through the acquisition of gated SPECT during inotropic stimulation with dobutamine [13–16]. In 1999, Everaert et al. did already study changes in global and regional left ventricular function in response to dobutamine infusion assessed in 10 healthy volunteers using sequential gated SPECT myocardial perfusion acquisitions [13]. The authors concluded that changes in wall thickness induced by infusion of low-dose dobutamine can be assessed by sequential gated SPECT myocardial perfusion studies. Based on this study it was suggested that the stress gated SPECT protocol proposed in their study might be helpful to distinguish viable from scar tissue in patients with coronary artery disease by demonstrating a preserved inotropic response in hypoperfused myocardium. In 2000, Narula et al. evaluated dual-isotope, gated SPECT imaging combined with low and high dose dobutamine as a single test for the characterization of various types of altered myocardial dysfunction [14]. They studied 54 patients with ischemic cardiomyopathy using rest and 4 h-redistribution thallium-201 imaging and dobutamine technetium-99m sestamibi SPECT and showed that this new imaging technique allowed the characterization of dysfunctional myocardium as stunned, hibernating, remodeled and E. E. van der Wall (&) Y. G. America A. J. Scholte J. J. Bax Department of Cardiology, Leiden University Medical Center, P.O. Box 9600, Leiden, The Netherlands e-mail: e.e.van_der_wall@lumc.nl