Validation of thoracic aortic dimensions on ECG-triggered SSFP as alternative to contrast-enhanced MRA.

OBJECTIVES: Assessment of thoracic aortic dimensions with non-ECG-triggered contrast-enhanced magnetic resonance angiography (CE-MRA) is accompanied with motion artefacts and requires gadolinium. To avoid both motion artefacts and gadolinium administration, we evaluated the similarity and reproducibility of dimensions measured on ECG-triggered, balanced steady-state free precession (SSFP) MRA as alternative to CE-MRA. METHODS: All patients, with varying medical conditions, referred for thoracic aortic examination between September 2016 and March 2018, who underwent non-ECG-triggered CE-MRA and SSFP-MRA (1.5 T) were retrospectively included (n = 30). Aortic dimensions were measured after double-oblique multiplanar reconstruction by two observers at nine landmarks predefined by literature guidelines. Image quality was scored at the sinus of Valsalva, mid-ascending aorta and mid-descending aorta by semi-automatically assessing the vessel sharpness. RESULTS: Aortic dimensions showed high agreement between non-ECG-triggered CE-MRA and SSFP-MRA (r = 0.99, p < 0.05) without overestimation or underestimation of aortic dimensions in SSFP-MRA (mean difference, 0.1 mm; limits of agreement, - 1.9 mm and 1.9 mm). Intra- and inter-observer variabilities were significantly smaller with SSFP-MRA for the sinus of Valsalva and sinotubular junction. Image quality of the sinus of Valsalva was significantly better with SSFP-MRA, as fewer images were of impaired quality (3/30) than in CE-MRA (21/30). Reproducibility of dimensions was significantly better in images scored as good quality compared to impaired quality in both sequences. CONCLUSIONS: Thoracic aortic dimensions measured on SSFP-MRA and non-ECG-triggered CE-MRA were similar. As expected, SSFP-MRA showed better reproducibility close to the aortic root because of lesser motion artefacts, making it a feasible non-contrast imaging alternative. KEY POINTS: • SSFP-MRA provides similar dimensions as non-ECG-triggered CE-MRA. • Intra- and inter-observer reproducibilities improve for the sinus of Valsalva and sinotubular junction with SSFP-MRA. • ECG-triggered SSFP-MRA shows better image quality for landmarks close to the aortic root in the absence of cardiac motion.

Correction to: Cardiovascular magnetic resonance native T2 and T2* quantitative values for cardiomyopathies and heart transplantations: a systematic review and meta-analysis.

An amendment to this paper has been published and can be accessed via the original article.

Cardiovascular magnetic resonance native T2 and T2* quantitative values for cardiomyopathies and heart transplantations: a systematic review and meta-analysis.

BACKGROUND: The clinical application of cardiovascular magnetic resonance (CMR) T2 and T2* mapping is currently limited as ranges for healthy and cardiac diseases are poorly defined. In this meta-analysis we aimed to determine the weighted mean of T2 and T2* mapping values in patients with myocardial infarction (MI), heart transplantation, non-ischemic cardiomyopathies (NICM) and hypertension, and the standardized mean difference (SMD) of each population with healthy controls. Additionally, the variation of mapping outcomes between studies was investigated. METHODS: The PRISMA guidelines were followed after literature searches on PubMed and Embase. Studies reporting CMR T2 or T2* values measured in patients were included. The SMD was calculated using a random effects model and a meta-regression analysis was performed for populations with sufficient published data. RESULTS: One hundred fifty-four studies, including 13,804 patient and 4392 control measurements, were included. T2 values were higher in patients with MI, heart transplantation, sarcoidosis, systemic lupus erythematosus, amyloidosis, hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM) and myocarditis (SMD of 2.17, 1.05, 0.87, 1.39, 1.62, 1.95, 1.90 and 1.33, respectively, P <  0.01) compared with controls. T2 values in iron overload patients (SMD = - 0.54, P = 0.30) and Anderson-Fabry disease patients (SMD = 0.52, P = 0.17) did both not differ from controls. T2* values were lower in patients with MI and iron overload (SMD of - 1.99 and - 2.39, respectively, P <  0.01) compared with controls. T2* values in HCM patients (SMD = - 0.61, P = 0.22), DCM patients (SMD = - 0.54, P = 0.06) and hypertension patients (SMD = - 1.46, P = 0.10) did not differ from controls. Multiple CMR acquisition and patient demographic factors were assessed as significant covariates, thereby influencing the mapping outcomes and causing variation between studies. CONCLUSIONS: The clinical utility of T2 and T2* mapping to distinguish affected myocardium in patients with cardiomyopathies or heart transplantation from healthy myocardium seemed to be confirmed based on this meta-analysis. Nevertheless, variation of mapping values between studies complicates comparison with external values and therefore require local healthy reference values to clinically interpret quantitative values. Furthermore, disease differentiation seems limited, since changes in T2 and T2* values of most cardiomyopathies are similar.

Transmural variation of myocardial attenuation and its potential effect on contrast-mediated estimates of regional myocardial perfusion.

Promising technical developments suggest that it may be feasible to use contrast echocardiography to estimate regional myocardial perfusion. Although the optimal approach has not yet been determined, the use of a nonlinear (harmonic) response of the contrast agent is common to several recent advances. The purpose of this article is to delineate the relation between the anisotropic (angle-dependent) ultrasonic attenuation of the myocardium through which the sound wave has propagated and the regional, nonlinear response of the contrast agent. Apparent perfusion will be modulated by this regionally varying, path-dependent attenuation, which is determined by the local angle between the propagating sound wave and the myofiber orientation. We illustrate the potential magnitude of the effect of myocardial anisotropy for the apical 4-chamber view by examining propagation along the septum and the lateral wall. We present experimentally measured values of the attenuation of excised sheep myocardium, showing statistically significant differences in the attenuation in the mid wall compared with that in symmetrical zones to the left and right of the mid wall, reflecting the well-known myofiber orientations in these 3 regions. The nonlinear (harmonic) response of a contrast agent depends on the local pressure amplitude, which for a given mechanical index is determined by the attenuation accumulated along the path to the point where the regional perfusion is estimated.

Transmural variation of myocardial attenuation measured with a clinical imager.

The objective of this study was to quantify the transmural variation in attenuation for the septal and lateral walls of the heart. Our approach was to utilize a commercially available ultrasonic imaging system to acquire images of excised sections of eight sheep hearts with an orientation similar to that encountered in the apical four-chamber view. The measured values (mean +/-SE) of the slope of attenuation for the transmural regions of the septum are: 1.40 +/-0.11, 0.99 +/-0.09, and 1.85 +/-0.16 (dB/cm/MHz) for the left subendocardial, midmyocardial, and right subendocardial zones, respectively. The analogous data from the lateral wall are: 1.42 +/-0.11, 0.83 +/-0.07, and 1.20 +/- 0.16 (dB/cm/MHz) for the subendocardial, midmyocardial, and subepicardial zones, respectively. These data demonstrate that ultrasonic attenuation associated with the septum and the lateral wall, when imaged in a manner similar to that of the apical four-chamber view, is anisotropic.