Martin Fasshauer

Cardiovascular magnetic resonance feature-tracking assessment of myocardial mechanics: Intervendor agreement and considerations regarding reproducibility

Aim To assess intervendor agreement of cardiovascular magnetic resonance feature tracking (CMR-FT) and to study the impact of repeated measures on reproducibility. Materials and methods Ten healthy volunteers underwent cine imaging in short-axis orientation at rest and with dobutamine stimulation (10 and 20 μg/kg/min). All images were analysed three times using two types of software (TomTec, Unterschleissheim, Germany and Circle, cvi42, Calgary, Canada) to assess global left ventricular circumferential (Ecc) and radial (Err) strains and torsion. Differences in intra- and interobserver variability within and between software types were assessed based on single and averaged measurements (two and three repetitions with subsequent averaging of results, respectively) as determined by Bland–Altman analysis, intraclass correlation coefficients (ICC), and coefficient of variation (CoV). Results Myocardial strains and torsion significantly increased on dobutamine stimulation with both types of software (p<0.05). Resting Ecc and torsion as well as Ecc values during dobutamine stimulation were lower measured with Circle (p<0.05). Intra- and interobserver variability between software types was lowest for Ecc (ICC 0.81 [0.63–0.91], 0.87 [0.72–0.94] and CoV 12.47% and 14.3%, respectively) irrespective of the number of analysis repetitions. Err and torsion showed higher variability that markedly improved for torsion with repeated analyses and to a lesser extent for Err. On an intravendor level TomTec showed better reproducibility for Ecc and torsion and Circle for Err. Conclusions CMR-FT strain and torsion measurements are subject to considerable intervendor variability, which can be reduced using three analysis repetitions. For both vendors, Ecc qualifies as the most robust parameter with the best agreement, albeit lower Ecc values obtained using Circle, and warrants further investigation of incremental clinical merit.

Quantification of left ventricular torsion and diastolic recoil using cardiovascular magnetic resonance myocardial feature tracking.

Objectives Cardiovascular magnetic resonance feature tracking (CMR-FT) offers quantification of myocardial deformation from routine cine images. However, data using CMR-FT to quantify left ventricular (LV) torsion and diastolic recoil are not yet available. We therefore sought to evaluate the feasibility and reproducibility of CMR-FT to quantify LV torsion and peak recoil rate using an optimal anatomical approach. Methods Short-axis cine stacks were acquired at rest and during dobutamine stimulation (10 and 20 µg·kg−1·min−1) in 10 healthy volunteers. Rotational displacement was analysed for all slices. A complete 3D-LV rotational model was developed using linear interpolation between adjacent slices. Torsion was defined as the difference between apical and basal rotation, divided by slice distance. Depending on the distance between the most apical (defined as 0% LV distance) and basal (defined as 100% LV distance) slices, four different models for the calculation of torsion were examined: Model-1 (25–75%), Model-2 (0–100%), Model-3 (25–100%) and Model-4 (0–75%). Analysis included subendocardial, subepicardial and global torsion and recoil rate (mean of subendocardial and subepicardial values). Results Quantification of torsion and recoil rate was feasible in all subjects. There was no significant difference between the different models at rest. However, only Model-1 (25–75%) discriminated between rest and stress (Global Torsion: 2.7±1.5°cm−1, 3.6±2.0°cm−1, 5.1±2.2°cm−1, p<0.01; Global Recoil Rate: −30.1±11.1°cm−1s−1,−46.9±15.0°cm−1s−1,−68.9±32.3°cm−1s−1, p<0.01; for rest, 10 and 20 µg·kg−1·min−1 of dobutamine, respectively). Reproducibility was sufficient for all parameters as determined by Bland-Altman analysis, intraclass correlation coefficients and coefficient of variation. Conclusions CMR-FT based derivation of myocardial torsion and recoil rate is feasible and reproducible at rest and with dobutamine stress. Using an optimal anatomical approach measuring rotation at 25% and 75% apical and basal LV locations allows effective quantification of torsion and recoil dynamics. Application of these new measures of deformation by CMR-FT should next be explored in disease states.

Real-time phase-contrast flow MRI of the ascending aorta and superior vena cava as a function of intrathoracic pressure (Valsalva manoeuvre).

OBJECTIVE Real-time phase-contrast flow MRI at high spatiotemporal resolution was applied to simultaneously evaluate haemodynamic functions in the ascending aorta (AA) and superior vena cava (SVC) during elevated intrathoracic pressure (Valsalva manoeuvre). METHODS Real-time phase-contrast flow MRI at 3 T was based on highly undersampled radial gradient-echo acquisitions and phase-sensitive image reconstructions by regularized non-linear inversion. Dynamic alterations of flow parameters were obtained for 19 subjects at 40-ms temporal resolution, 1.33-mm in-plane resolution and 6-mm section thickness. Real-time measurements were performed during normal breathing (10 s), increased intrathoracic pressure (10 s) and recovery (20 s). RESULTS Real-time measurements were technically successful in all volunteers. During the Valsalva manoeuvre (late strain) and relative to values during normal breathing, the mean peak flow velocity and flow volume decreased significantly in both vessels (p < 0.001) followed by a return to normal parameters within the first 10 s of recovery in the AA. By contrast, flow in the SVC presented with a brief (1-2 heartbeats) but strong overshoot of both the peak velocity and blood volume immediately after pressure release followed by rapid normalization. CONCLUSION Real-time phase-contrast flow MRI may assess cardiac haemodynamics non-invasively, in multiple vessels, across the entire luminal area and at high temporal and spatial resolution. ADVANCES IN KNOWLEDGE Future clinical applications of this technique promise new insights into haemodynamic alterations associated with pre-clinical congestive heart failure or diastolic dysfunction, especially in cases where echocardiography is technically compromised.

Real-time phase-contrast flow MRI of haemodynamic changes in the ascending aorta and superior vena cava during Mueller manoeuvre.

AIM To evaluate the potential of real-time phase-contrast flow magnetic resonance imaging (MRI) at 40 ms resolution for the simultaneous determination of blood flow in the ascending aorta (AA) and superior vena cava (SVC) in response to reduced intrathoracic pressure (Mueller manoeuvre). MATERIALS AND METHODS Through-plane flow was assessed in 20 healthy young subjects using real-time phase-contrast MRI based on highly undersampled radial fast low-angle shot (FLASH) with image reconstruction by regularized non-linear inversion. Haemodynamic alterations (three repetitions per subject = 60 events) were evaluated during normal breathing (10 s), inhalation with nearly closed epiglottis (10 s), and recovery (20 s). RESULTS Relative to normal breathing and despite interindividual differences, reduced intrathoracic pressure by at least 30 mmHg significantly decreased the initial peak mean velocity (averaged across the lumen) in the AA by -24 ± 9% and increased the velocity in the SVC by +28 ± 25% (p < 0.0001, n = 23 successful events). Respective changes in flow volume per heartbeat were -25 ± 9% in the AA and +49 ± 44% in the SVC (p < 0.0001, n = 23). Flow parameters returned to baseline during sustained pressure reduction, while the heart rate was elevated by 10% (p < 0.0001) after the start (n = 24) and end (n = 17) of the manoeuvre. CONCLUSIONS Real-time flow MRI during low intrathoracic pressure non-invasively revealed quantitative haemodynamic adjustments in both the AA and SVC.

Noninvasive estimation of pulmonary outflow tract obstruction: a comparative study of phase contrast CMR and Doppler echocardiography versus cardiac catheterization.

maximal PCMR gradients and mean Doppler gradients revealed best agreement (maximal PCMR: bias = +1.8 mmHg, r = 0.90, p = 0.14; mean Doppler: bias = -2.3 mmHg, r = 0.87, p = 0.17). Mean PCMR gradients underestimated, while maximal Doppler gradients systematically overestimated catheter PPG (mean PCMR: bias = -7.7 mmHg, r = 0.90, p < 0.001; maximal Doppler: bias = +13.9 mmHg, r = 0.88, p < 0.001). Conclusions

Absence of DNA double strand breaks in human peripheral blood mononuclear cells after magnetic resonance imaging assessed by γH2AX flow cytometry: a prospective blinded trial

Background Magnetic Resonance Imaging (MRI) is regarded as a non harming and non invasive imaging modality with superb tissue contrast and almost no side effects. Compared to other cross-sectional imaging modalities MRI does not use ionizing radiation. Recently however, strong magnetic fields as applied in clinical MRI scanners have been suspected to induce DNA double strand breaks in human lymphocytes.

Non-invasive estimation of pulmonary outflow tract obstruction: A comparative study of cardiovascular phase contrast magnetic resonance and Doppler echocardiography versus cardiac catheterization

Aim To compare estimated pressure gradients from routine follow-up cardiovascular phase-contrast magnetic resonance (PC-MR) with those from Doppler echocardiography and invasive catheterization in patients with congenital heart disease (CHD) and pulmonary outflow tract obstruction. Methods In 75 patients with pulmonary outflow tract obstruction maximal and mean PC-MR gradients were compared to maximal and mean Doppler gradients. Additionally, in a subgroup of 31 patients maximal and mean PC-MR and Doppler pressure gradients were compared to catheter peak-to-peak pressure gradients (PPG). Results Maximal and mean PC-MR gradients underestimated pulmonary outflow tract obstruction as compared to Doppler (max gradient: bias = + 8.4 mm Hg (+ 47.6%), r = 0.89, p < 0.001; mean gradient: + 4.3 mm Hg (+ 49.0%), r = 0.88, p < 0.001). However, in comparison to catheter PPG, maximal PC-MR gradients (bias = + 1.8 mm Hg (+ 8.8%), r = 0.90, p = 0.14) and mean Doppler gradients (bias = − 2.3 mm Hg (− 11.2%), r = 0.87, p = 0.17) revealed best agreement. Mean PC-MR gradients underestimated (bias = − 7.7 mm Hg (− 55.6%), r = 0.90, p < 0.001) while maximal Doppler gradients systematically overestimated catheter PPG (bias = + 13.9 mm Hg (+ 56.5%), r = 0.88, p < 0.001). Conclusions Estimated maximal PC-MR pressure gradients from routine CHD follow-up agree well with invasively assessed peak-to-peak pressure gradients. Estimated maximal Doppler pressure gradients tend to overestimate, while Doppler mean gradients agree better with catheter PPG. Therefore, our data provide reasonable arguments to either apply maximal PC-MR gradients or mean Doppler gradients to non-invasively evaluate the severity of pulmonary outflow tract obstruction in the follow-up of CHD.

Cardiac MRI underlines the role of BNP and hematologic parameters as heart failure markers in patients with Ebstein's anomaly of the tricuspid valve

Background Ebstein’s anomaly of the tricuspid valve involves a congenitally displaced and dysplastic tricuspid valve (TV). The displacement of the TV towards the apex results in an enlarged right atrium (RA) with an atrialzied portion of the right ventricle (aRV) and an enlarged functional right ventricle (fRV). Brain natriuretic peptide (BNP) is a heart failure marker. Its role in Ebstein’s anomaly has not been evaluated in conjunction with cardiac MRI (CMR) parameters. Hematologic parameters (hemoglobin (Hb), hematocrite (Hct)) are upregulated in states of pulmonary hypo perfusion as in congenital cyanotic heart disease. Intermittent Pulmonary hypo perfusion may be a an indicator of right heart failure in patients with Ebstein’s anomaly, but has not been studied so far. The aim of the present study was to correlate CMR functional parameters and severity of disease with BNP and hematologic parameters in patients with Ebstein’ sa nomaly. Methods 26 patients with non-corrected Ebstein’ sa nomaly were studied prospectively. Laboratory parameters (BNP, Hb, Hct), CMR data (RA, aRV, fRV, left atrial (LA) and left ventricular (LV) volumes and functional parameters like ejection fraction (EF), stroke volume (SV) and others) as well as exercise capacity (maximal oxygen uptake (VO2 max.), CO2 equivalent (VE/VCO2), maximum heart rate (max. HR) using a cycle ergometer) were all measured on the same day for an individual patient. Results

Cardiovascular magnetic resonance myocardial feature tracking for the measurement of myocardial twist and untwist at rest and during dobutamine stress in healthy volunteers.

Background CMR feature tracking (CMR-FT) is a method of assessing strain from routinely acquired steady- state free precession (SSFP) cine images similar to echocardiographic speckle tracking. However, its application to determine myocardial twist and untwist has never previously been explored. We sought to determine the feasibility of measuring twist and untwist from routine cine images in healthy volunteers at rest and during inotropic stimulation.

Real time cardiac MRI and its clinical usefulness in arrhythmias and wall motion abnormalities

Background Analysis of cardiac function in patients with arrhythmias is very limited or nearly impossible in ECG synchronized cine acquisitions with balanced SSFP. A real-time method at 1.5 T with SSFP contrast was used to show that this method is superior for image quality and analysis of ventricular function in a subset of patients with atrial fibrillation and AV-Block. Methods Radial gradient-echo sequences with fully balanced SSFP gradients and at least 15-fold undersampling (real-time SSFP, RT) and conventional ECG-synchronized cine SSFP CMR (Cine) was used on a 1.5 T scanner system. Patients who had permanent arrhythmias (most often atrial fibrillation, AA; n = 8) or wall motion abnormalities (WMA; n = 3) were scanned in the standard views and compared to patients in sinus rhythm (SR;n = 21) without wall motion abnormalities. Image reconstruction of RT was performed offline by regularized nonlinear inversion. Quality (IQ) of scan was detected using an image quality score (ranging from 0 = no diagnostic quality to 1 = reduced diagnostic quality, 2 = many artifacts, 3 = some artifacts, and 4 = optimal diagnostic quality). Cardiac function was analyzed using a semiautomatic contour detection (Q mass, Medis, NL) applied to 5 consecutive baets in RT and Cine avering data of 10-12 beats. All analysis was done by two blinded observers (3 and 8 years experience of CMR evaluation). Results IQ was comparable for Cine and RT SSFP in patients with WMA or patients in sinus rhythm without WMA given in Table 1. However, IQ was significantly better