The year in cardiology 2017: imaging

This Year in Cardiology 2017 review article provides a broad overview of the novelties published in non-invasive cardiovascular imaging. While it is well established that echocardiography is the imaging technique of first choice to evaluate patients with cardiovascular symptoms, other techniques (nuclear imaging, cardiovascular magnetic resonance, and computed tomography) are needed to image specific-disease characteristics or pathophysiological mechanisms that may impact on the patient's management. The evidence showing the incremental diagnostic and prognostic value of combination of imaging techniques or fusion imaging is growing exponentially. Advances in non-invasive cardiac imaging have provided important new insights in the pathophysiology of valvular heart disease and cardiomyopathies, risk stratification of patients with suspected coronary artery disease and diagnosis of implanted device- or bioprosthesis-related complications; this article provides an overview of the most relevant articles published in 2017. Advances in non-invasive cardiac imaging have provided important new insights in the pathophysiology of valvular heart disease and cardiomyopathies, risk stratification of patients with suspected coronary artery disease (CAD), and diagnosis of implanted device- or bioprosthesis-related complications. The evidence showing the incremental diagnostic and prognostic value of combination of imaging techniques or fusion imaging is growing rapidly. This Year in Cardiology 2017 review article provides a broad overview of the novelties published in non-invasive cardiovascular imaging. The role of echocardiography in the diagnosis of valvular heart disease was underscored in the OxValve Population Cohort Study which recruited 2500 patients aged 65 years and older without known valvular heart disease.1 One in two of the elderly population had newly diagnosed (predominantly mild) valvular heart disease: 34% presented aortic sclerosis, 22% mitral regurgitation, and 15% aortic regurgitation. Moderate and severe undiagnosed valvular heart disease was identified in 6.4% of patients. Interestingly, moderate and severe valvular heart disease was three times more common in patients with atrial fibrillation (AF), which could be considered as a marker of silent significant valvular heart disease. Projections based on the OxValve Population Cohort Study suggest that the number of individuals aged 65 years or more in the UK will increase from 1.5 million in 2015 to 3 million by 2046. The results of this study provide further insights in the pathophysiology and natural history of valvular heart disease and have important implications for the management of elderly patients in the current era with growing advances in transcatheter therapies. Selection of patients who may benefit from valvular intervention relies on symptoms and effects of the abnormal loading conditions on the cardiac chambers. The extent of cardiac damage caused by the abnormal valve haemodynamics is an important determinant of the morbi-mortality of patients with heart valve disease. From the Placement of Aortic Transcatheter Valves (PARTNER)-2 trials, 1661 patients with severe stenosis were classified into four stages based on the cardiac damage assessed with echocardiography: no extra-valvular cardiac damage (Stage 0, n = 47), left ventricular (LV) damage characterized by increased LV mass index (Stage 1, n = 212), left atrial (LA), or mitral damage, including LA dilation, moderate, and severe mitral regurgitation and AF (Stage 2, n = 814), pulmonary vasculature or tricuspid damage characterized by systolic pulmonary hypertension and moderate or severe tricuspid regurgitation (Stage 3, n = 413) and right ventricular damage characterized by moderate and severe right ventricular dysfunction (Stage 4, n = 145).2 One-year mortality rates after aortic valve replacement increased along with progression of cardiac damage stage: from 4.4% in stage 0 to 24.5% in Stage 4. Each increment in cardiac damage stage was independently associated with increased mortality [hazard ratio (HR) 1.46, 95% confidence interval (CI) 1.27–1.67; P < 0.0001]. Patients with symptomatic low-flow, low-gradient severe aortic stenosis may display significant cardiac damage with concentric LV hypertrophy and restrictive physiology, resembling cardiac amyloidosis. Between 6% and 12% of such patients may have transthyretin cardiac amyloidosis.3 , 4 In 151 patients with severe aortic stenosis undergoing transcatheter aortic valve implantation, technetium-99 m pyrophosphate (99mTc-PYP) cardiac scintigraphy was performed to evaluate the presence of concomitant transthyretin cardiac amyloidosis and tissue Doppler echocardiography, as well as LV global longitudinal strain (GLS) with two-dimensional speckle tracking echocardiography to assess LV systolic function.5 Sixteen percent of patients had a 99mTc-PYP scan positive for transthyretin cardiac amyloidosis. Compared to patients with isolated severe aortic stenosis, patients with concomitant transthyretin cardiac amyloidosis showed more LV hypertrophy, lower stroke volume, more advanced LV diastolic dysfunction, and reduced LV function [lower LV ejection fraction (EF), more impaired LV GLS and lower peak systolic velocity on tissue Doppler imaging, S′] (Take home figure). A value of S′ ≤6 cm/s on tissue Doppler echocardiography was strongly associated with a positive 99mTc-PYP scan. The clinical implications of these findings need to be evaluated in larger studies confirming that patients with concomitant transthyretin cardiac amyloidosis have worse prognosis after aortic valve replacement as compared to patients with isolated aortic stenosis. Transthyretin cardiac amyloidosis in patients with severe aortic stenosis. Panels A and B show the technetium-99m pyrophosphate (99mTc-PYP) cardiac scintigraphy and the left ventricular global longitudinal strain bull’s eye plot of a patient without transthyretin cardiac amyloidosis. A 99mTc-PYP cardiac scintigraphy positive for transthyretin cardiac amyloidosis shows an increased heart-to-contralateral ratio (H/CL) (panel C) and more impaired left ventricular global longitudinal strain (panel D). Panel E shows the receiver operating curves for several echocardiographic parameters of left ventricular systolic and diastolic dysfunction. The S′ measured on tissue Doppler imaging had the largest area under the curve to predict 99mTc-PYP cardiac scintigraphy positive for transthyretin cardiac amyloidosis. Reproduced with permission from Castano et al. 3 AS, aortic stenosis; ATTR-CA, transthyretin cardiac amyloidosis; AUC, area under the curve; CI, confidence interval; Decel, deceleration; H/CL, heart-to-contralateral ratio; LS, longitudinal strain; MCF, myocardial contraction fraction; VMR, voltage-mass ratio. The role of three-dimensional transoesophageal echocardiography to better characterize the mitral valve anatomy and dynamics in mitral regurgitation was highlighted in several publications. For example, Kagiyama et al.6 demonstrated the presence of insufficient remodelling of the mitral leaflets assessed with three-dimensional transoesophageal echocardiography in 28 AF patients with moderate and severe mitral regurgitation compared to 56 AF patients without mitral regurgitation. The ratio between the total leaflet area and the mitral annulus area was significantly smaller among patients with moderate and severe mitral regurgitation than in patients without (1.29 ± 0.10 vs. 1.65 ± 0.24, P < 0.001) indicating insufficient growth (remodelling) of the mitral leaflets to compensate for the dilation of the mitral annulus in AF (which then resulted in significant mitral regurgitation). Furthermore, van Wijngaarden et al. 7 demonstrated the different dynamics of the mitral valve annulus on three-dimensional transoesophageal echocardiography in patients with severe mitral regurgitation due to fibroelastic deficiency, Barlow’s disease, and secondary mitral regurgitation. The mitral annulus dimensions were largest in patients with Barlow’s disease whereas no differences were observed between patients with fibroelastic deficiency and patients with secondary mitral regurgitation. Along the cardiac cycle, the mitral annulus remained flat and less dynamic (the annulus height to the commissural width ratio was 18.24 ± 4.9 at early systole, 18.24 ± 4.7 at mid-systole, and 17.67 ± 4.4 at late systole, P = 0.083) in patients with secondary mitral regurgitation whereas patients with fibroelastic deficiency and Barlow’s disease had more pronounced saddle-shaped mitral annulus which became significantly flatter at late systole (the annulus height to commissural width ratio changed from 21.99 ± 4.83 to 17.39 ± 4.2 in fibroelastic deficiency patients and from 23.89 ± 4.05 to 15.36 ± 4.2 in Barlow’s disease patients; P < 0.001 for all). These findings suggest that mitral annulus mechanics are important pathophysiological determinants of the mitral valve dysfunction. Standardization of novel echocardiographic techniques is key for implementation in routine clinical practice. Left ventricular GLS measurement has better inter-observer agreement than LVEF for follow-up of LV systolic function by multiple observers.8 In contrast, assessment of regional LV longitudinal strain has shown higher inter-vendor variability.9 Differences in image quality, tracking algorithms, and noise reduction by temporal and spatial smoothing across the various vendors may explain the high variability in regional strain measurements. Reproducible measurements of LV GLS and regional strain are important when echocardiographic follow-up is needed. In patients undergoing cancer treatment, early detection of cardiac dysfunction is the key to implement cardioprotective strategies to prevent irreversible cardiotoxicity. Left ventricular strain and strain rate measurements are more sensitive markers of LV systolic dysfunction than LVEF, which may enable earlier detection of cardiac damage. How these measures relate to ventricular-arterial coupling in this particular subgroup of patients was evaluated by Narayan et al. 10 Of 135 patients with breast cancer receiving doxorubicin and trastuzumab, 15% developed cancer therapeutics-related cardiotoxicity over a median follow-up of 1.9 years. The ratio between effective arterial elastance and the end-systolic elastance (measure of ventricular-arterial coupling) and LV circumferential strain at baseline showed the largest area under the curve (AUC) to predict the occurrence of cancer therapeutics-related cardiotoxicity (0.703 and 0.655, respectively). However, these areas under the curve indicate the modest discriminatory ability to identify the patients who will develop cardiotoxicity. Randomized clinical trials would be ideal to determine the external validity of these findings. Nuclear imaging provides unique, additional information to that provided by other imaging techniques. However, nuclear imaging involves ionizing radiation. In a recent consensus document by the three major European professional associations in the field of cardiac imaging, the best practices (technology, radiotracers, and data acquisition) to achieve the lowest radiation were summarized.11 In the field of nuclear cardiology, the use of new cadmium–zinc–telluride gamma cameras (that provide increased signal detection efficiency) and digital positron emission tomography (PET) detector technology based on silicon photomultipliers have resulted in a significant decrease in patient radiation burden (comparable to natural radiation exposure) without major impact on image quality and diagnostic accuracy. Both nuclear perfusion imaging and coronary computed tomography angiography (CCTA) provide important prognostic information. The association between atherosclerotic plaque features on CCTA and the presence of myocardial ischaemia on 99mTc-tetrofosmin stress/rest single photon emission computed tomography (SPECT) was evaluated in 184 patients with single vessel CAD.12 Total plaque volume and burden, and specifically for non-calcified, low-density non-calcified and calcified plaques, remodelling index, contrast density difference, lesion length, and diameter stenosis were significantly larger in those coronary arteries supplying ischaemic territories on myocardial perfusion imaging as compared with arteries supplying non-ischaemic territories. However, on multivariable analysis, non-calcified plaques (odds ratio 2.6), low-density non-calcified plaques (odds ratio 3.9) and contrast density difference (odds ratio 2.7) were significantly associated with ischaemia, whereas the degree of stenosis was not. The study demonstrated that other plaque characteristics than only coronary luminal narrowing are major determinants of myocardial ischaemia. These results provide interesting support for the concept that ischaemia reflects not only luminal narrowing but also relates to vulnerable plaques. Cardiac sarcoidosis remains one of the major diagnostic challenges in cardiology. 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