Segmental biventricular analysis of myocardial function using high temporal and spatial resolution tissue phase mapping.

OBJECTIVE Myocardial dysfunction of the right ventricle (RV) is an important indicator of RV diseases, e.g. RV infarction or pulmonary hypertension. Tissue phase mapping (TPM) has been widely used to determine function of the left ventricle (LV) by analyzing myocardial velocities. The analysis of RV motion is more complicated due to the different geometry and smaller wall thickness. The aim of this work was to adapt and optimize TPM to the demands of the RV. MATERIALS AND METHODS TPM measurements were acquired in 25 healthy volunteers using a velocity-encoded phase-contrast sequence and kt-accelerated parallel imaging in combination with optimized navigator strategy and blood saturation. Post processing was extended by a 10-segment RV model and a detailed biventricular analysis of myocardial velocities was performed. RESULTS High spatio-temporal resolution (1.0 × 1.0 × 6 mm3, 21.3 ms) and the optimized blood saturation enabled good delineation of the RV and its velocities. Global and segmental velocities, as well as time to peak velocities showed significant differences between the LV and RV. Furthermore, complex timing of the RV could be demonstrated by segmental time to peak analysis. CONCLUSION High spatio-temporal resolution TPM enables a detailed biventricular analysis of myocardial motion and might provide a reliable tool for description and detection of diseases affecting left and right ventricular function

UNFOLDed spiral SPiRIT TPM enables high spatio-temporal resolution analysis of cardiac function.

A detailed TPM analysis of cardiac function necessitates high spatio-temporal resolution which leads to prolonged scan durations. These scan times are typically too long for data acquisition within a single breath hold. Respiratory navigator-gating can compensate breathing-related motion, but causes an additional increase in measurement time and images with residual motion artifacts. The aim of this study was to combine UNFOLD with variable density spiral SPiRIT TPM to achieve an additional scan time reduction by a factor of 2 and an effective undersampling factor of 6. UNFOLDed SPiRIT TPM demonstrates good results and enables scan times within very short breath holding

A quantitative comparison of regional myocardial motion in mice, rabbits and humans using in-vivo phase contrast CMR

Abstract Background Genetically manipulated animals like mice or rabbits play an important role in the exploration of human cardiovascular diseases. It is therefore important to identify animal models that closely mimic physiological and pathological human cardiac function. Methods In-vivo phase contrast cardiovascular magnetic resonance (CMR) was used to measure regional three-directional left ventricular myocardial motion with high temporal resolution in mice (N=18), rabbits (N=8), and humans (N=20). Radial, long-axis, and rotational myocardial velocities were acquired in left ventricular basal, mid-ventricular, and apical short-axis locations. Results Regional analysis revealed different patterns of motion: 1) In humans and rabbits, the apex showed slower radial velocities compared to the base. 2) Significant differences within species were seen in the pattern of long-axis motion. Long-axis velocities during systole were fairly homogeneously distributed in mice, whereas humans showed a dominant component in the lateral wall and rabbits in the base. 3) Rotational velocities and twist showed the most distinct patterns in both temporal evolution and relative contribution of base, mid-ventricle and apex, respectively. Interestingly, a marked difference in rotational behavior during early-systole was found in mice, which exhibited clockwise rotation in all slice locations compared to counter-clockwise rotation in rabbits and humans. Conclusions Phase contrast CMR revealed subtle, but significantly different regional myocardial motion patterns in mice, rabbits and humans. This finding has to be considered when investigating myocardial motion pattern in small animal models of heart disease.</p

Spatial Correlation of Action Potential Duration and Diastolic Dysfunction in Transgenic and Drug-induced LQT2 Rabbits

Focus Issue: Sudden Cardiac DeathInternational audienceEnhanced dispersion of action potential duration (APD) is a major contributor to long-QT-(LQTS)-related arrhythmias.We aimed at investigating spatial correlations of regional heterogeneities in cardiac repolarization and mechanical function in LQTS.Female transgenic LQT2 (n=11) and wildtype (LMC) rabbits (n=9/10 without/with E4031) were subjected to phase contrast MRI to assess regional myocardial velocities. In the same rabbits' hearts, monophasic APDs were assessed in corresponding segments.In LQT2 and E4031 rabbits, APD was longer in all LV segments (p<0.01) and APD dispersion was greater than in LMC (p<0.01). In diastole, peak radial velocities (Vr) were reduced in LQT2 and E4031 compared to LMC in base and mid (cm/s, LQT2, -3.36±0.4, p<0.01, E4031, -3.24±0.6, p<0.0001, LMC, -4.42±0.5) - indicating an impaired diastolic function. Regionally heterogeneous diastolic Vr correlated with APD (LQT2, CC 0.3