Cardiovascular magnetic resonance: at the heart of 21st Century imaging
Cardiovascular magnetic resonance (CMR) provides an exquisite anatomical and functional assessment of the heart and vascular system and does so without the use of ionizing radiation. Through the development of an array of specialised and complementary imaging sequences, clinical CMR has now become a “one-stop shop” for diagnostic and prognostic imaging to answer a wide range of clinical questions. Common indications for CMR include but are not limited to; coronary artery disease (using gadolinium contrast imaging for myocardial perfusion and myocardial viability), valvular heart disease (using phase contrast imaging for quantification of stenoses or regurgitation), cardiomyopathy and inherited (being the gold standard for quantification of ventricular volumes, mass and ejection fraction), congenital heart disease (unparalleled anatomical and flow quantification of shunts, conduits and anatomical communications), inflammatory heart disease and many others. This series of Cardiovascular Diagnosis and Therapy focuses the contemporary use of advanced CMR techniques in heart failure and left ventricular (LV) hypertrophy. It highlights not only the current state of the art CMR for clinical imaging but also the current and future tissue characterisation and multinuclear capabilities that define CMR as unique in the field of cardiac imaging.
Obesity is a global pandemic and not only causes LV hypertrophy and heart failure but can also severely limit the quality of ultrasound imaging. This series begins with an original article from Dr. Rayner et al., demonstrating that obesity related ventricular remodelling is exacerbated in dilated and hypertrophic cardiomyopathy (Rayner et al.). This highlights both the importance of obesity as a modifiable risk factor in established cardiac disease, and also the capability of CMR to provide an accurate and reproducible volumetric assessment of the heart irrespective of the degree of chest wall adiposity.
One of the leading clinical indications for CMR is to determine the cause of undiagnosed LV hypertrophy. Drs. Lewis and Rider continue the edition with a review on the use of CMR in the assessment of undifferentiated LV hypertrophy, highlighting the typical structural, tissue characteristic, late gadolinium, T1 and T2 characteristics that typify, and allow the separation of, the common causes of LV hypertrophy, namely; amyloid, hypertrophic cardiomyopathy, cardiac sarcoidosis, Fabry disease and hypertensive heart disease (Lewis et al.).
Beyond anatomical and functional imaging, CMR can probe the metabolic mechanisms that underlie many cardiovascular diseases. In this series, Dr. Watson has reviewed the changes in cardiac metabolism that can be imaged with the unique multinuclear capabilities of CMR and magnetic resonance spectroscopy (Watson et al.). The article highlights the use of 1H-MRS for the determination of cardiac fat and creatine content, 31P-MRS for interrogation of cardiac high energy phosphate metabolism, 2H-MRS for glucose metabolism, 23Na imaging for myocardial viability, 17O-MRS for oxygen consumption, and also introduces the state-of-the-art technique of hyperpolarized 13C-MRS to image cardiac carbohydrate metabolism and tricarboxylic acid cycle metabolites.
Myocarditis due to viral aetiologies is a relatively common cause of acute chest pain syndromes in younger and middle-aged patients and often has a benign prognosis, though this and other forms of myocarditis also cause serious sequelae, including heart failure, arrhythmia and death. The series continues with a review on the use of CMR and specifically parametric T1 and T2 mapping for the detection of myocardial inflammation, and also the potential for future strategies including hyperpolarised 1-[13C] lactate imaging as a readout for macrophage activity (Lewis et al.). These techniques are likely to have future applications to better understand the role of immune cells in the development of cardiovascular diseases.
Cardio-oncology is another rapidly growing sub-speciality within cardiology. Contemporary cancer therapy has resulted in significant survival gains for many patients. However, many current and emerging cancer therapies have an associated risk of cardiotoxicity, either acutely or later in life. Dr. Burrage continues this series with a review on the role for CMR as means to identify those at risk of cardiotoxicity, to precisely monitor cardiac function during cancer therapy and as a means of monitoring long term cancer survivors (Burrage et al.).
With both a range of exciting preclinical discoveries and recent clinical trial data supporting the use of metabolically active drugs as novel therapies for heart failure, imaging myocardial energy metabolism has become a priority. Dr. Peterzan shifts the focus of this series back to metabolism with a historical, current era and future perspectives review on the investigation of myocardial energetics in cardiac disease using 31P magnetic resonance spectroscopy (Peterzan et al.).
This series concludes with two short perspective pieces considering the expanding roles for CMR internationally in both clinical and research settings. The first is by Dr. Nikolaidou who presents the arguments for and against “Should Everyone have an MRI in Heart Failure?” (Nikolaidou et al.). The second by Dr. Hundertmark discusses “Should CMR be the default imaging modality in clinical trials for heart failure?” (Hundertmark et al.).
Contemporary CMR is a powerful and versatile tool for the diagnosis and management of patients with cardiovascular diseases. It provides an unparalleled assessment of cardiac function and myocardial morphology and has unique abilities to probe tissue characteristic and myocardial metabolism. This special series highlights the many current and future benefits of CMR to optimise the diagnosis and management of patients with LV hypertrophy and heart failure.
Acknowledgments
Funding: None.
Footnote
Provenance and Peer Review: This article was commissioned by the editorial office, Cardiovascular Diagnosis and Therapy for the series “The Use of Advanced Cardiac MRI in Heart Failure and Cardiac Hypertrophy”. The article did not undergo external peer review.
Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/cdt-20-577). The series “The Use of Advanced Cardiac MRI in Heart Failure and Cardiac Hypertrophy” was commissioned by the editorial office without any funding or sponsorship. AJML and OJR served as the unpaid Guest Editors of the series. AJML reports other from Bayer, other from Boehringer Ingelheim, outside the submitted work. The authors have no other conflicts of interest to declare.
Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.
