Tissue characterization by T1 and T2 mapping cardiovascular magnetic resonance imaging to monitor myocardial inflammation in healing myocarditis.

AIMS: Monitoring disease activity in myocarditis is important for tailored therapeutic strategies. This study evaluated the ability of T1 and T2 mapping cardiovascular magnetic resonance (CMR) to monitor the course of myocardial inflammation in healing myocarditis. METHODS AND RESULTS: Forty-eight patients with strictly defined acute myocarditis underwent CMR at 1.5 T in the acute stage, at 3-months (n = 39), and at 12-months follow-up (FU) (n = 21). Normal values were obtained in a control group of 27 healthy subjects. The CMR protocol included standard ('Lake-Louise') sequences as well as T1 (modified Look-Locker inversion recovery sequence, MOLLI) and T2 (gradient- and spin-echo sequence, GraSE) mapping. T1, T2, and extracellular volume (ECV) maps were generated using an OsiriX plug-in. Native myocardial T1, T2, and ECV values were increased in the acute stage, but declined with healing of myocarditis. The performances of global native T1 and T2 to differentiate acute from healed myocarditis stages were significantly better compared with all other global CMR parameters with AUCs of 0.85 (95% CI, 0.76-0.94) and 0.83 (95% CI, 0.73-0.93). Furthermore, regional native T1 and T2 in myocarditis lesions provided AUCs of 0.97 (95% CI, 0.93-1.02) and 0.93 (95% CI, 0.85-1.01), which were significantly superior to any other global or regional CMR parameter. CONCLUSION: Healing of myocarditis can be monitored by native myocardial T1 and T2 measurements without the need for contrast media. Both native myocardial T1 and T2 provide an excellent performance for assessing the stage of myocarditis by CMR.

Cardiac remodeling following percutaneous mitral valve repair - initial results assessed by cardiovascular magnetic resonance imaging.

PURPOSE: Percutaneous mitral valve repair with the MitraClip device (Abbott Vascular, Redwood City, California, USA) is a novel therapeutic option in patients with mitral regurgitation. This study evaluated the feasibility of cardiac volume measurements by cardiovascular magnetic resonance imaging (CMR) to assess reverse myocardial remodeling in patients after MitraClip implantation. MATERIALS AND METHODS: 12 patients underwent CMR at baseline (BL) before and at 6 months follow-up (FU) after MitraClip implantation. Cine-CMR was performed in short- and long-axes for the assessment of left ventricular (LV), right ventricular (RV) and left atrial (LA) volumes. RESULTS: Assessment of endocardial contours was not compromised by the device-related artifact. No significant differences in observer variances were observed for LV, RV and LA volume measurements between BL and FU. LV end-diastolic (median 127 [IQR 96 - 150] vs. 112 [86 - 150] ml/m(2); p = 0.03) and LV end-systolic (82 [54 - 91] vs. 69 [48 - 99] ml/m(2); p = 0.03) volume indices decreased significantly from BL to FU. No significant differences were found for RV end-diastolic (94 [75 - 103] vs. 99 [77 - 123] ml/m(2); p = 0.91), RV end-systolic (48 [42 - 80] vs. 51 [40 - 81] ml/m(2); p = 0.48), and LA (87 [55 - 124] vs. 92 [48 - 137] ml/m(2); p = 0.20) volume indices between BL and FU. CONCLUSION: CMR enables the assessment of cardiac volumes in patients after MitraClip implantation. Our CMR findings indicate that percutaneous mitral valve repair results in reverse LV but not in RV or LA remodeling. KEY POINTS: • Volume measurements by cardiovascular magnetic resonance imaging are feasible following percutaneous mitral valve repair despite device-related artifacts.• A significant reduction of left ventricular volume was found in terms of beneficial, reverse left ventricular remodeling after 6-month follow-up.• No significant reduction was found in right ventricular or left atrial volumes after percutaneous mitral valve repair after 6-month follow-up.

Improved agreement between experienced and inexperienced observers using a standardized evaluation protocol for cardiac volumetry and infarct size measurement.

PURPOSE: To study the agreement between experienced and inexperienced observers before and after training using a standardized evaluation protocol for cardiac magnetic resonance imaging (CMR) measurements of left ventricular (LV) volumes, mass and infarct size. MATERIALS AND METHODS: First, 10 CMR studies from patients with myocardial infarction were analyzed by 2 experienced and 4 inexperienced observers in respect to end-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), LV mass and infarct size. Subsequently, the inexperienced observers were trained using a standardized evaluation protocol. Thereafter, all observers analyzed another 10 CMR studies. RESULTS: Before training the relative difference between experienced and inexperienced observers was -4.3±8.2% for EDV, -13.3±14.2% for ESV, 5.9±8.2% for EF, -12.2±10.9% for LV mass and -27.0±29.0% for infarct size in gram. After training, agreement significantly improved to 0.2±8.8% for EDV (p<0.05), -2.1±10.9 for ESV (p<0.01), 1.5±6.9% for EF (p<0.05), and -3.6±17.1% for infarct size (p<0.0001), but no improvement was seen for LV mass (-11.2±7.9, p=0.64). A slice based analysis showed, that the variable inclusion of the most basal and apical slices were mainly responsible for the low agreement of the measurements before training. CONCLUSION: Training using a standardized evaluation protocol significantly improved the agreement between experienced and inexperienced observers for important CMR parameters. The proposed evaluation protocol can be used for training to improve the reproducibility of CMR measurements.

Quantification of mechanical ventricular dyssynchrony: direct comparison of velocity-encoded and cine magnetic resonance imaging.

PURPOSE: The preoperative assessment of mechanical dyssynchrony can help to improve patient selection in candidates for cardiac resynchronization therapy (CRT). The present study compared the performance of velocity-encoded (VENC) MRI to cine-magnetic resonance imaging (MRI) for quantifying mechanical ventricular dyssynchrony. MATERIALS AND METHODS: VENC-MRI and cine-MRI were performed in 20 patients with heart failure NYHA class III and reduced ejection fraction (median: 24 %, interquartile range: 18 - 28 %) before CRT device implantation. The interventricular mechanical delay (IVMD) was assessed by VENC-MRI as the temporal difference between the onset of aortic and pulmonary flow. Intraventricular dyssynchrony was quantified by cine-MRI, using the standard deviation of time to maximal wall thickening in sixteen left ventricular segments (SDt-16). The response to CRT was assessed in a six-month follow-up. RESULTS: 14 patients (70 %) clinically responded to CRT. A similar accuracy was found to predict the response to CRT by measurements of the IVMD and SDt-16 (75 vs. 70 %; p = ns). The time needed for data analysis was significantly shorter for the IVMD at 1.69 min (interquartile range: 1.66 - 1.88 min) compared to 9.63 min (interquartile range: 8.92 - 11.63 min) for the SDt-16 (p < 0.0001). CONCLUSION: Measurements of the IVMD by VENC-MRI and the SDt-16 by cine-MRI provide a similar accuracy to identify clinical responders to CRT. However, data analysis of the IVMD is significantly less time-consuming compared to data analysis of the SDt-16.

Intraindividual comparison of contrast-enhanced MRI and unenhanced SSFP sequences of stenotic and non-stenotic pulmonary artery diameters.

PURPOSE: To evaluate the agreement of pulmonary artery diameters assessed with 3D contrast-enhanced MR angiography (CE-MRA) and a 2D balanced steady-state-free precession sequence (bSSFP) in non-stenotic and stenotic pulmonary arteries (PA). METHODS AND MATERIALS: 44 right and left PAs (30 non-stenotic and 14 stenotic) were examined in 23 consecutive patients by performing CE-MRA as well as bSSFP. Two independent readers determined the transverse diameters of the PA. RESULTS: No significant difference in diameter measurements was found between CE-MRA and bSSFP (p = 0.8608 for the stenotic and p = 0.6208 for the non-stenotic PA). Bland-Altman analysis revealed good agreement between CE-MRA and bSSFP for both the non-stenotic (mean bias, 0.07 cm; with 95 % limits of agreement, ± 0.34 cm) and the stenotic (mean bias, 0.05 cm; with 95 % limits of agreement, ± 0.30 cm) PA. CONCLUSION: bSSFP allows rapid and accurate determination of PA diameters without the use of ionizing radiation and the risk of contrast media-associated side-effects.

Delayed-enhancement magnetic resonance imaging in patients with clinically suspected stress cardiomyopathy (Tako-tsubo).

PURPOSE: To compare the ability of delayed-enhancement magnetic resonance imaging (DE-MRI) and other MRI and clinical parameters to identify diseases mimicking stress cardiomyopathy (SCM). MATERIALS AND METHODS: The study included 14 consecutive patients fulfilling the American Heart Association (AHA) criteria for SCM with acute left ventricular dysfunction in the absence of coronary artery disease, triggered by psychological stress. The MRI protocol consisted of cine, T 2-weighted, first-pass-perfusion (FPP) and DE-MRI. RESULTS: Six patients with DE were classified as mimicking SCM (non-SCM) and 8 patients without DE as SCM. FPP defects were found in 4 patients with non-SCM and in none with SCM (p < 0.05). Myocardial edema was found in 5 patients with non-SCM and in 2 patients with SCM (p = ns). No significant differences in clinical findings such as ECG, cardiac markers and echocardiographic recovery of left ventricular function were found between patients with non-SCM and SCM. CONCLUSION: Non-SCM defined by DE-MRI is a frequent finding in patients fulfilling the AHA criteria for SCM. Clinical findings seem to be of limited value to differentiate between non-SCM and SCM.

Assessment of left ventricular function parameters with a new three-dimensional shape model.

PURPOSE: To evaluate a 3D model of the left ventricle (LV) which allows calculation of LV function parameters on the basis of both short axis (SA) and long axis (LA) cine acquisitions. Comparison with the conventional Simpson's rule method in a volunteer and patient collective. MATERIALS AND METHODS: Cine imaging was performed with a prospectively triggered SSFP sequence: trueFISP: TR 3.6 msec, TE 1.8 msec, bFFE: TR 3.0 msec, TE 1.4 msec, flip angle 60 degrees , resolution 1.37 x 1.37 mm, slice thickness 8 mm, gap 2 mm in SA orientation from apex to basis and in radial LA orientation (spacing 15 degrees) in 11 volunteers and 27 patients with mitral valve insufficiency. Five different volume computations were compared: Simpson's rule based on all SA slices (M0), 3D shape model based on all SA slices (M1a), 3D shape model based on 3 SA slices (M1b), 3D shape model based on all SA and LA slices (M2a), and 3D shape model based on 3 SA slices and 1 LA slice (M2b). RESULTS: M 0 and M 1a give similar results (r: 0.99, b: 0.98). M 2a produces larger volumes than M 0 (b: 0.85) due to the inclusion of the LA contours. M 1b effectively reproduces the volumes computed with M 0 (r: 0.99, b: 1.02). M 2b effectively reproduces the volumes computed with M 2a (r: 0.99, b: 0.94). M 2b and M 0 give similar results in the patient collective (r: 0.99, b: 0.97). CONCLUSION: The proposed 3D shape model allows merging of information acquired in different orientations and thus the combination of SA and LA contours with better coverage of the left ventricle. It provides a suitable fit with a reduced number of segmented contours.

Assessment of myocardial viability in ischemic heart disease by cardiac magnetic resonance imaging.

Assessment of myocardial viability aims at differentiating between viable and non-viable myocardium. The proof of dysfunctional but viable myocardium is crucial to predict outcome of revascularization after acute (AMI) and chronic myocardial infarction (CMI). Cardiac magnetic resonance imaging (CMRI) offers different options to detect viable myocardium: Measurements of end-diastolic wall thickness by cine-CMRI can be used to depict chronically scarred myocardium, but fails to detect acute myocardial necrosis. Low-dose dobutamine stimulation (LDDS) cine-CMRI analyses the contractile reserve of dysfunctional but viable myocardium under pharmacologic stimulus to identify viable myocardium in AMI and CMI with high specificity. Sensitivity of LDDS cine-CMRI is superior to LDDS echocardiography but reduced in patients with severely impaired left ventricular (LV) function. The delayed-enhancement (DE) technique directly visualises non-viable myocardium due to an altered contrast-media distribution in necrotic and fibrotic tissue. DE-CMRI identifies non-viable myocardium with high spatial resolution independently from LV function. The transmural extent of contrast enhancement in DE-CMRI is used to predict functional recovery after revascularization in AMI and CMI. Furthermore, the amount and pattern of contrast enhancement in DE-CMRI provide important prognostic information in both entities. Recent studies demonstrated the superiority of DE-CMRI compared to single photon emission tomography (SPECT) and positron emission tomography (PET) to assess myocardial viability. Therefore, DE-CMRI is currently recognised as the standard of reference for assessment of myocardial viability. The technical background, clinical application and accuracy of the different CMRI techniques to assess myocardial viability in AMI and CMI are discussed in this work.