Imaging the left ventricle: diagnostic and prognostic implications in cardiomyopathies

For the podcast associated with this article, please visit https://academic.oup.com/eurheartj/pages/Podcasts. Imaging of the cardiac chambers was of immense importance for the progress of cardiology. It started with angiography after the Second World War, was vastly expanded with the introduction of echocardiography in the 1970s, and further advanced with the development of magnetic resonance imaging (MRI) and computed tomography (CT). In their Review ‘The Year in Cardiology 2018: imaging’, Jeroen J. Bax from Leiden University Medical Center in The Netherlands, and colleagues1 discuss the most recent progress of cardiac imaging and remind us that strain imaging echocardiography has provided important insights into various cardiac conditions, and the evidence demonstrating its incremental prognostic value over the left ventricular ejection fraction, particularly in patients with mitral regurgitation, is growing.2 Similarly, tissue characterization with late gadolinium enhancement and T1 mapping using MRI has provided novel diagnostic algorithms and improved risk stratification in cardiomyopathies. In addition, assessment of coronary artery disease with CT is changing from assessing lesion severity3,4 to plaque characterization, and even myocardial perfusion and coronary fractional flow reserve5,6 and prediction of outcomes.7 The prognostic value of coronary flow reserve as determined by positron emission tomography (PET) has been established in large-scale studies. Technological advances in fusion imaging, such as PET combined with CT or MRI, allow for simultaneous characterization of anatomical tissue changes with functional alterations.8,9 Left ventricular filling is an important part of the cardiac cycle. Of note, the ratio of early mitral inflow velocity to the global diastolic strain rate (E/e'sr) is a predictor of events. In their article entitled ‘Ratio of transmitral early filling velocity to early diastolic strain rate predicts long-term risk of cardiovascular morbidity and mortality in the general population’, Mats Christian Højbjerg Lassen and colleagues from Gentofte University Hospital in Hellerup, Denmark measured E/e'sr in 1238 participants derived from the general population.10 During a median of 11 years, 11.3% had a cardiac event. The global diastolic strain rate was associated with an adverse outcome, with a hazard ratio of 1.17 per 10 cm increase. After multivariable adjustment, the global diastolic strain rate remained an independent predictor, with a hazard ratio of 1.08. Global longitudinal strain modified the relationship between the global diastolic strain rate and outcome. After multivariable adjustment, the global diastolic strain rate was a stronger predictor in those with good systolic function as determined by global longitudinal strain >18%, when compared with those with reduced systolic function. The global diastolic strain rate provided incremental information, with a C-index of 0.839 beyond the SCORE risk chart. Thus, in the general population, the global diastolic strain rate provides independent and incremental prognostic information regarding cardiovascular morbidity and mortality. Additionally, the global diastolic strain rate is a stronger predictor of cardiac events than E/e'. These novel findings are put into context in a thought-provoking Editorial by Thor Edvardsen from the Oslo University Hospital in Norway.11 Non-ischaemic cardiomyopathies are an important cause of heart failure and death. Cardiac MRI detects myocardial scar and fibrosis using late gadolinium enhancement. In their article ‘Prevalence and prognosis of ischaemic and non-ischaemic myocardial fibrosis in older adults’, Andrew E. Arai and colleagues from the National Institutes of Health in Bethesda, Maryland, USA determined myocardial fibrosis in a community-based sample of 900 older adults.12 Late gadolinium enhancement divided subjects into four groups: (i) myocardial infarction; (ii) major non-ischaemic fibrosis; (iii) minor non-ischaemic fibrosis; and (iv) no late enhancement. Over the course of 5.8 years, 115 deaths and 77 hospitalizations for heart failure occurred. After adjustment, major non-ischaemic fibrosis remained independently associated with death and heart failure, with a hazard ratio of 3.2, while myocardial infarction and minor non-ischaemic enhancement did not (Figure 1). Thus, major non-ischaemic patterns of myocardial fibrosis portend worse prognosis in an older community-based cohort. Whether gender differences matter in this context13 and whether removal of myocardial scar will become a new therapeutic target remains to be seen.2 These provocative results are further discussed in an interesting Editorial by Dudley J. Pennell from the Royal Brompton Hospital in London, UK.14 Inverse propensity adjusted prognosis of ischaemic and non-ischaemicmyocardial fibrosis (from Shanbhag SM, Greve AM, Aspelund T, Schelbert EB, Cao JJ, Danielsen R, Thorgeirsson G, Sigurðsson S, Eiríksdóttir G, Harris TB, Launer LJ, Guðnason V, Arai AE. Prevalence and prognosis of ischaemic and non-ischaemicmyocardial fibrosis in older adults. See pages 529–538). In patients with non-ischaemic cardiomyopathy, a mortality benefit of an implantable cardioverter-defibrillator (ICD) in primary prevention is questionable.15,16 Left ventricular scar identified by MRI is associated with a high risk of malignant arrhythmia in non-ischaemic cardiomyopathies and may allow for better risk stratification. In their article ‘Reduction in mortality from implantable cardioverter-defibrillators in non-ischaemic cardiomyopathy patients is dependent on the presence of left ventricular scar’, Andrew J. Taylor and colleagues from the Alfred Heart Centre and Baker IDI Heart and Diabetes Research Institute in Melbourne, Australia investigated the impact of left ventricular scar on the mortality benefit of an ICD in 452 heart failure patients with non-ischaemic cardiomyopathies.17 After 38 months, there was no difference in MAGGIC score between those who did and those who did not receive a primary prevention ICD. In patients without left ventricular scar, ICDs were not associated with improved mortality, while, in those with scar, an ICD was independently associated with reduced mortality, with an impressive hazard ratio of 0.45 (Figure 2). Thus, in non-ischaemic cardiomyopathies, an ICD in primary prevention is only associated with reduced mortality in those with left ventricular scar. This may enable better risk stratification of such patients. The clinical implications and these findings for current guidelines are outlined in an Editorial by Frank Pelosi from the University of Michigan in Ann Arbor, Michigan, USA.18 Propensity-matched cohort—effect of implantable cardioverter-defibrillator on survival in scar negative (A and B) and scar positive (C and D) patients. There was no difference in overall (A) and cardiovascular (B) mortality in the patients without left ventricle scar based on presence of implantable cardioverter-defibrillator. In patients with left ventricle scar, implantable cardioverter-defibrillator implantation was associated with lower all cause (C) and cardiovascular (D) mortality. CV, cardiovascular; HR, hazard ratio; ICD, implantable cardioverter-defibrillator (from Gutman SJ, Costello BT, Papapostolou S, Voskoboinik A, Iles L, Ja J, Hare JL, Ellims A, Kistler PM, Marwick TH, Taylor AJ. Reduction inmortality from implantable cardioverter-defibrillators in non-ischaemic cardiomyopathy patients is dependent on the presence of left ventricular scar. See pages 542–550). Lately, different imaging modalities have been increasingly combined for the diagnosis of valvular19,20 and coronary artery disease,21 aortic dissection,22 as well as in patients with endocarditis23 or pericarditis.24 This is addressed in a Current Opinion entitled ‘Multimodality imaging in cardiology: a statement on behalf of the Task Force on Multimodality Imaging of the European Association of Cardiovascular Imaging’ by Kevin Fox from the Imperial College Healthcare NHS Trust in London, UK25 on behalf of the European Association of Cardiovascular Imaging (EACVI) Task Force on Multimodality Imaging who provide insights on the progression of multimodality imaging to improve patient care. Best clinical care will need an appropriate use of one or more imaging modalities. The EACVI is committed to enhancing the multimodality approach through education and research. This issue is complemented by two Discussion Forum articles. Jacek J. Gajek and colleagues from the Wroclaw Medical University in Poland comment on a Cardiovacular Flashlight manuscript entitled ‘Intermittent PQ prolongation between two premature ventricular complexes: what is the mechanism?’ by Firat Duru and colleagues from the University Hospital Zürich in Switzerland.26,27 Duru and colleagues respond to it in a response.28 The editors hope that readers of this issue of the European Heart Journal will find it of interest.