Myocardial Tissue Characterization in Heart Failure with Preserved Ejection Fraction: From Histopathology and Cardiac Magnetic Resonance Findings to Therapeutic Targets

Heart failure with preserved ejection fraction (HFpEF) is a complex clinical syndrome responsible for high mortality and morbidity rates. It has an ever growing social and economic impact and a deeper knowledge of molecular and pathophysiological basis is essential for the ideal management of HFpEF patients. The association between HFpEF and traditional cardiovascular risk factors is known. However, myocardial alterations, as well as pathophysiological mechanisms involved are not completely defined. Under the definition of HFpEF there is a wide spectrum of different myocardial structural alterations. Myocardial hypertrophy and fibrosis, coronary microvascular dysfunction, oxidative stress and inflammation are only some of the main pathological detectable processes. Furthermore, there is a lack of effective pharmacological targets to improve HFpEF patients’ outcomes and risk factors control is the primary and unique approach to treat those patients. Myocardial tissue characterization, through invasive and non-invasive techniques, such as endomyocardial biopsy and cardiac magnetic resonance respectively, may represent the starting point to understand the genetic, molecular and pathophysiological mechanisms underlying this complex syndrome. The correlation between histopathological findings and imaging aspects may be the future challenge for the earlier and large-scale HFpEF diagnosis, in order to plan a specific and effective treatment able to modify the disease’s natural course.

Takotsubo Syndrome—Is There a Need for CMR?

Purpose of Review Takotsubo syndrome (TTS) is a transient but severe myocardial dysfunction that has been known for decades and is still to be fully understood regarding its clinical presentations and pathophysiological mechanisms. Cardiac magnetic resonance (CMR) imaging plays a key role in the comprehensive analysis of patients with TTS in acute and follow-up examinations. In this review, we focus on the major advantages and latest evolutions of CMR in diagnosis and prognostication of TTS and discuss future perspectives and needs in the field of research and cardiovascular imaging in TTS. Recent Findings Specific CMR criteria for TTS diagnosis at the time of acute presentation are established. In addition to identifying the typical regional wall motion abnormalities, CMR allows for precise quantification of right ventricular and left ventricular (LV) function, the assessment of additional abnormalities/complications (e.g. pericardial and/or pleural effusion, LV thrombi), and most importantly myocardial tissue characterization (myocardial oedema, inflammation, necrosis/fibrosis). Summary CMR enables a comprehensive assessment of the entire spectrum of functional and structural changes that occur in patients with TTS and may have also a prognostic impact. CMR can distinguish between TTS and other important differential diagnoses (myocarditis, myocardial infarction) with direct consequences on medical therapy.

Diagnostic Role of Cardiovascular Magnetic Resonance Imaging in Dilated Cardiomyopathy

Aims The purpose of the study was to compare the accuracy of cardiac magnetic resonance (CMR) with echocardiography for the evaluation of ventricular dysfunction in patients of dilated cardiomyopathy (DCM). Further, we evaluated the potential of CMR for myocardial tissue characterization. Design Prospective observational. Materials and Methods A total of 30 patients with suspected DCM prospectively underwent cardiac magnetic resonance (MR) using a 1.5 Tesla MR scanner, with appropriate phased-array body coils. Dynamic sequences after injection of 0.1 mmol/kg of body weight of gadolinium-based intravenous contrast (Magnevist) were acquired for each patient, after which delayed images were obtained at an interval of 12 to 15 minutes. Myocardial tagging was performed in all patients for assessment of wall motion abnormalities. Each MR examination was interpreted with two radiologists for chamber dimensions and ventricular dysfunction as well as morphologic characteristics with disagreement resolved by consensus. All patients included in the study were taken up for MR evaluation after cardiological evaluation through echocardiography and the results for both the studies were compared. Data were analyzed through standard statistical methods. Conclusion CMR is a comprehensive diagnostic tool, which can estimate the ventricular function more precisely than echocardiography. CMR reliably differentiates between ischemic and nonischemic etiologies of DCM based on patterns of late gadolinium enhancement (LGE) and based on the presence or absence of LGE, which helps to estimate the degree of myocardial fibrosis. Thereby it can be a useful tool in establishing risk stratification, predicting prognosis, and thus instituting appropriate therapy in DCM patients.

Imaging myocardial ischemia: from emerging techniques to state-of-the-art

The widespread clinical use of cardiovascular imaging inspires constant improvement in imaging technology and post-processing applications. Recent advances in hardware and software have brought about important developments in the assessment of myocardial ischemia such as the rapid evaluation of cardiac volumes and function, ability for detection of subtle myocardial changes, and the combination of anatomic and functional assessment of a coronary artery stenosis via a single modality, which was previously not possible in a noninvasive fashion. These milestones indicate the start of a new era, a paradigm shift that broadens the role of noninvasive imaging. The thematic series Myocardial tissue characterization in ischemic heart disease introduces a set of narrative review and original articles by world renowned authors demonstrating such novel advancements and the state-of-the-art techniques in cardiac imaging.

Value CMR: Towards a Comprehensive, Rapid, Cost-Effective Cardiovascular Magnetic Resonance Imaging

CMR is considered the gold standard for measuring heart function, including cardiac volumes and mass. Further, in a single CMR exam, information about cardiac function, structure, tissue composition, and blood flow could be obtained. Nevertheless, CMR is underutilized due to long scanning times, the need for multiple breath-holds, use of a contrast agent, and relatively higher cost compared to echocardiography.In this study, we propose a rapid CMR exam based on recent developments in imaging sequences. The proposed exam is both rapid and provides comprehensive cardiovascular information without the need for a contrast agent or multiple breath-holds. The developed exam includes advanced sequences for evaluating global and regional cardiac functions, myocardial tissue characterization, and flow hemodynamics in the heart, valves, and large vessels. Time-consuming conventional sequences have been replaced by advanced sequences, which resulted in reducing scan time from > 1 hour with conventional CMR exam to <20 minutes with the proposed rapid CMR exam. Specifically, conventional two-dimensional (2D) cine and phase-contrast (PC) sequences have been replaced by optimized three-dimensional (3D)-cine and four-dimensional (4D)-flow sequences, respectively. Compared to 2D cine imaging that requires 12-16 separate breath-holds, the implemented 3D-cine sequence allows for whole heart coverage in 1-2 breath-holds; thus, reducing scan time by 80-90%. Similarly, compared to 2D PC flow imaging that requires multiple breath-holds and the presence of an experienced cardiac operator for precise prescription of the imaging planes, the implemented 4D-flow sequence allows for whole-chest coverage in ∼10-minute, free-breathing acquisition without the need for a navigator echo, which makes scan time independent of the patient’s breathing pattern. Furthermore, conventional myocardial tagging has been replaced by the fast strain-encoding (SENC) sequence, which reduces scan time from one slice per breath-hold to only one slice per heartbeat (∼1 second). Finally, T1 and T2 mapping sequences are included in this proposed exam, which allow for myocardial tissue characterization without the need for contrast. The proposed rapid exam has been tested on volunteers and measurements showed good agreement with those from conventional sequences despite the significant reduction in scan time.In conclusion, we propose a rapid, contrast-free, and comprehensive cardiovascular exam that does not require repeated breath-holds or a cardiac experienced operator to run the exam, which would result in improving cost effectiveness of CMR and increasing its adoption in clinical practice.