Despite multiple advances in cardiovascular disease, the morbidity and mortality of patients with heart failure (HF) in the setting of IHD remains high. Although it is believed that most patients with symptoms of significant ischemia may benefit from revascularization, decisions regarding revascularization in those with advanced ventricular dysfunction and no significant ischemia are complex, and the applicability of current clinical trial data is often challenged by limited patient selection. Over the past three decades, information describing cardiac structure, function, perfusion, hemodynamics, and metabolism obtained from noninvasive cardiac imaging studies has been used to guide management decisions for patients with HF. Although this anatomic and physiologic information adds value to clinical care, an accepted strategy is still debated regarding the optimal testing sequence approach to efficiently identify the treatment strategy most likely to improve outcomes. Consensus on proper use of cardiac imaging studies has been hindered by absence of clinical studies that objectively compare the independent treatment-related prognostic information of each test obtained using standardized methods. Uniformity of reporting formats also needs to be improved in order to provide a clearer working scheme for clinicians.
Alternative Imaging Modalities in Ischemic Heart Failure (AIMI-HF) (Project I-A of the Imaging Modalities to Assist with Guiding Therapy and the Evaluation of Patients with Heart Failure, IMAGE-HF program) is a multicenter trial with the primary objective of comparing the effect of HF imaging strategies on the composite clinical endpoint of cardiac death, myocardial infarction (MI), resuscitated cardiac arrest and cardiac re-hospitalization (worsening heart failure, acute coronary syndrome, arrhythmia). Patients with an ischemic heart disease (IHD) etiology will follow HF imaging strategy algorithms according to the question(s) asked by the physicians (for example, is there ischemia and/or viability?), in agreement with their local clinical practices for standard and alternative imaging. Patients will be randomized to either standard imaging modalities for ischemia and/or viability (SPECT) or advanced imaging modalities, namely cardiac magnetic resonance imaging (CMR) or positron emission tomography (PET). Secondary objectives include the effect of HF imaging strategies on the incidence of revascularization procedures, left ventricular remodeling, HF symptoms and quality of life, as well as a health economic evaluation. A biomarker substudy (on renal function, left ventricular remodeling and a selected set of biomarkers), assessing mechanisms underlying specific cardiovascular events, is also planned (see Additional file 1).
Imaging in ischemic heart failure
Increasingly over the past three decades, information describing cardiac structure, function, perfusion, hemodynamics, and metabolism obtained from noninvasive cardiac imaging studies has been used to guide management decisions for patients with HF. Although this anatomic and physiologic information adds value to clinical care, an accepted imaging strategy has not evolved that tailors the testing sequence to specific presenting features of individual patients to efficiently identify the treatment strategy most likely to improve outcomes. Consensus on proper use of cardiac imaging studies has been hindered by the absence of clinical studies that objectively compare the independent treatment-related prognostic information of each test obtained using standardized methods.
Observational data has demonstrated that methods to define ischemia, viability and scar can identify high risk patients likely to benefit (or not) from revascularization [17–22].
The long-term impact of newer or alternative imaging strategies used for the revascularization decision processes has not been evaluated prospectively in HF. Revascularization has the potential to restore function to dysfunctional viable myocardium but not scar. Our group and others have shown that patients with dysfunctional but viable hibernating myocardium are at high risk for cardiac events if they do not undergo timely revascularization [20, 23].
Until recently, data from predominantly observational studies had shown that when viability is present, patients have better outcomes with revascularization [24–26]. The PET and Recovery Following Revascularization (PARR-2) trial  represents the largest randomized study to evaluate viability imaging in patients with severe LV dysfunction. Overall, there was a trend for benefit for Fluorodeoxyglucose (18F) positron emission tomgoraphy scan (FDG PET) assisted management over standard care. When the adherence to imaging recommendations was considered, there was a significant outcome benefit. A high risk subgroup demonstrated a significant mortality benefit [20, 27]. Recently, in a post-hoc analysis a significant reduction in events was observed in a subset of patients at the Ottawa site (Ottawa-FIVE) . The results suggest outcome benefits can be achieved using FDG PET in an experienced center with ready access to FDG and interactions with HF and revascularization teams.
Although PARR2 was unique as a randomized controlled trial for imaging viability, it was underpowered for the primary outcome. Larger prospective randomized studies are needed, although undertaking such studies can be challenging [16, 29, 30]. The STICH viability study  did not include a comparison to late gadolinium enhanced CMR, other modalities, nor evaluate the role of stress induced ischemia. Finally, although care was taken to standardize imaging acquisition and transfer of data, standardization was not as rigorous as has recently been achieved in the CADRE Ontario provincial registry .
Results from the STICH Viability substudy  suggest that identification of viable myocardium by single photon emission computed tomography (SPECT) or dobutamine stress echocardiography (DSE) do not add value in patients selected for surgical revascularization. The STICH Viability substudy results may be explained by a patient population that was at lower risk, with patients already acceptable for revascularization, having more single vessel disease, infrequent previous CABG, low incidence of renal dysfunction and predominantly without heart failure. For such patients, it may be argued that viability imaging is not needed. This is in contrast to sicker populations in studies such as PARR2 [20, 27], where physicians were uncertain about revascularization decisions and, therefore, needed viability assessment. Viability testing was not randomized in STICH [15, 16, 29]. The authors acknowledged the potential for selection bias . Furthermore, only 19% of patients in the substudy were considered to have nonviable myocardium, which is far less than in most previous studies [29, 32, 33]. Analyses combining DSE and SPECT results were performed. Ischemia and hibernation imaging were not reported. More advanced (or alternative) ischemia and viability imaging modalities (that is, using PET and CMR) were not evaluated.
Thus the STICH results need to be interpreted cautiously [16, 30], and the limitations along with the other observational and randomized data, justify the need for a prospective randomized trial to evaluate imaging strategies in patients with heart failure.
AIMI-HF is a large randomized controlled trial, comparing ‘advanced imaging technologies’ (PET and CMR) to standard imaging (SPECT). The findings will provide policy makers with data to support (or not) further investment in and dissemination of alternative or advanced technologies.