Methods

Our study was a multicenter study and included MRI studies obtained at Oregon Health & Science University (Portland, Oregon), The Royal Brompton National Heart and Lung Hospital (London, United Kingdom), Texas Children’s Hospital (Houston, Texas), and the University of Washington (Seattle, Washington). We included patients with SVs that were of left ventricular or indeterminate type who had undergone cavopulmonary anastomosis procedures. Our controls were patients with normal hearts. The institutional review board at Oregon Health & Science University approved the study. For studies sent to us from outside institutions, patients’ identifications had been replaced by numeric codes.

The speckle-tracking program, VVI, was applied to the magnetic resonance images. VVI is commercially available for the analysis of 2-dimensional echocardiographic images, but not for magnetic resonance images. Here, the VVI analysis program used was adapted for MRI mechanical function. All magnetic resonance images were acquired using an electrocardiographically gated 1.5- or 3.0-T magnet. Depending on the center at which the images were acquired, the images were obtained with Intera 3T (Philips Medical Systems, Andover, Massachusetts) or GE Healthcare (Milwaukee, Wisconsin) systems. At 1.5 T, the cine sequences were run in steady-state free precession mode, while at 3 T, the images were acquired in conventional gradient-echo mode, without steady-state free procession mode. The gradient-echo cine loop images were converted from Digital Imaging and Communications in Medicine to Audio Video Interleave format and were analyzed using the VVI myocardial method.

Short-axis MRI sequences were used. Images were acquired at frame rates of 15 to 25 frames/s. VVI was applied to gradient cine MRI sequences close to the apex for the SV and control groups. The endocardial borders of the SVs in the subjects and the left ventricles of the controls were traced manually in end-diastole ( Figures 1 and 2 ). VVI parameters were generated for 6 radial segments, as is standard for VVI, of the ventricles. These parameters included circumferential strain, rotation, and time to peak for both. The average of each parameter was compared between the SV and control groups.

VVI tracing of MRI gradient cine of the short axis. Left ventricular endocardium of non-SV was traced using VVI and is depicted in the top image. SV endocardium was traced and is depicted in the bottom image. Rotational displacement for each of the 6 segments of the left ventricle was recorded, as well as the average value. The maximum wall delay in the non-SV endocardium was 240 ms, compared to 560 ms in the SV, indicating a wider dispersion of time to peak in the latter. Rotational displacement was also reduced in the SV endocardium compared with that of the non-SV.

VVI of a short-axis gradient magnetic resonance image in an SV heart. Rotational velocity derived from an SV in a short-axis image is shown above. Peak rotational velocity and time to peak are reported for each of the 6 segments of the ventricle, as well as the average strain rate.

Results

Cardiac magnetic resonance images of SVs after cavopulmonary anastomosis were analyzed. Thirty-eight children and adults made up this group, aged 8 to 37 years (mean 18). The control group was composed of 14 patients (mean age 22 years). The percentages of men in the SV and control groups were 60% and 50%, respectively.

MRI short-axis cines were analyzed by VVI near the apical level. For the control group, mean circumferential strain was −18.0 ± 7.3%, whereas for the SV group, mean circumferential strain was reduced to −8.9 ± 7.3% (p <0.0001; Figure 3 ). Mean dispersion of peak circumferential strain was 44.2 ± 37.1 ms in the control group and 181.6 ± 76.1 ms in the SV group ( Figure 4 ).

Comparison of average rotation and average circumferential strain (CS) between non-SV and SV groups. The average degree of rotation of single ventricle was −2.6 ± 1.24°, compared with −7.7 ± 1.38° in the non-SV (p <0.0001). The average circumferential strain was also reduced from −18.0 ± 7.3% in the non-SV group to −8.9 ± 7.3% in the SV group.

Dispersion of peak rotation and peak circumferential strain (CS) between SVs and non-SVs. The maximal segmental delay, obtained from rotation and circumferential strain, was more widely dispersed in the SV than in the non-SV. The mean rotational segmental delay was 166.5 ± 72.4 ms for the SVs, compared to 39.6 ± 22.8 ms for the non-SVs (p <0.0001). Mean circumferential strain delay was 181.6 ± 76.1 ms in the SV group, compared to 44.2 ± 37.4 ms in the non-SV group (p = 0.004).

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

1. New Set of Intravascular Ultrasound-Derived Anatomic Criteria for Defining Functionally Significant Stenoses in Small Coronary Arteries (Results from Intravascular Ultrasound Diagnostic Evaluation of Atherosclerosis in Singapore [IDEAS] Study)
2. Demographic and Cardiovascular Risk Factors Modify Association of Fasting Insulin With Incident Coronary Heart Disease and Ischemic Stroke (from the Atherosclerosis Risk In Communities Study)
3. Detection of Progressive Cardiac Dysfunction by Serial Evaluation of Circumferential Strain in Patients With Duchenne Muscular Dystrophy
4. The Metaphoric and Morphologic Heart: Symbol and Substance

Stay updated, free articles. Join our Telegram channel

Join