Photon Counting Computed Tomography in Heart Failure Patients

Patients with severe acute or chronic heart failure are increasing worldwide. Heart failure clinicians are faced daily with the need to set up short- and long- term therapeutic strategies in line with heart failure etiology and myocardial recovery chances of each patient. Current treatment strategies for severe heart failure also include mechanical circulatory support with artificial devices (such as intraaortic balloon pump, Impella, ECMO, durable left ventricular assist device), which poses specific challenges for cardiac imaging. Through its ability to directly visualize scar and evaluate its transmural extent, cardiac magnetic resonance (CMR) offers a unique advantage over other currently available imaging techniques as a central player in viability assessment in patients with coronary disease, and represents the first line technique to investigate the chances of myocardial function recovery. CMR is also an important tool to provide diagnostic data in patients with non-ischemic heart failure. Unfortunately, CMR is not feasible in many heart failure patients (for example those on MCS therapy) due to the metallic components of the mechanical devices. In these patients, the computed tomography (CT) is the alternative imaging technique to visualize cardiac structures, diagnose complications, and assess possible indications for surgical interventions. However, CT has poorer resolution and do not offer the possibility to evaluate myocardial viability in patients with contraindication to CMR. Therefore, this issue currently represents one of the major unmet needs in the clinical management of severe heart failure patients.

Recent technological advances in the field of CT imaging have nevertheless paved the way to explore new pathways of myocardial viability assessment even in patients traditionally deemed unsuitable for CMR. The introduction of photon-counting detectors, in particular, is expected to be the next major breakthrough in clinical x-ray computed tomography (CT). Photon-counting detector (PCD)-CT will overcome several shortcomings and limitations of current CT systems: it might substantially improve and expand the applicability of CT imaging by offering intrinsic spectral capabilities, increased spatial resolution, reduced electronic noise and improved image contrast. On the basis of this physical principle PCCT has the promise to improve the actual not fully satisfactory quality of scar visualization in CT images. In particular, conventional scanners are affected by a limited contrast resolution which lead to a variable and relevant rate of false negative myocardial scar-free images depending on the assessor expertise. The constant improving of CT diagnostic field have been revolutionizing the diagnostic workflow in several cardiac disease. Late contrast enhancement CT demonstrated an adequate accuracy to detect and discriminate the etiology of both ischemic and non-ischemic causes of myocardial injury compared to actual gold standard exams in patients with a troponin-positive acute chest pain syndrome. The same technique showed good sensitivity, specificity and a high negative predictive value (95%) for the identification of myocardial scars imputed to be an anatomical substrate of ventricular tachycardia with a proper concordance with electro-anatomic mapping findings (k=0.536). Finally, this enormous potential of CT implementation with the novel PCCT will provide not only the possibility to further study myocardial viability, but also is expected to be superior to standard CT exams in details definition, reduction of electronic noise and increase of spatial resolution, with consequent specific advantages in patients with heart failure, especially those with artificial devices with metallic components, in which adverse event identification and definition (such as inflow or outflow thrombosis) is complex. Thanks to these multiple diagnostic and therapeutic advantages, in combination with the availability of the PCCT device, the use of such technique is now the preferred cardiac imaging examination for the study of cardiac anatomy and function in patients with severe heart failure and a contraindication to perform the gold standard CMR. Thus, we planned a single-center observational study to asses the performance of PCCT in the identification of myocardial scars and patterns in critically ill patients with severe heart failure.