Cardiac MRI shows promise for left ventricular noncompaction staging

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Left ventricular noncompaction syndrome, a cardiomyopathy characterized by deep trabeculations in the ventricular wall, is typically diagnosed by echocardiography. However, according to research published this month in the American Journal of Roentgenology, echocardiography may not visualize the apical region optimally, leading to underestimation of the degree of the disease.
 
“Recent cardiac MRI reports suggest a ratio of noncompacted myocardium to compacted myocardium of >2.3 yields the highest sensitivity (86 percent) and specificity (99 percent) in diagnosis,” the authors wrote.
 
Researchers from the department of radiology’s cardiac MR-PET-CT program at Massachusetts General Hospital and Harvard Medical School in Boston conducted a retrospective blinded study of 19 patients with cardiac MRI. Nine patients presented with a diagnosis of left ventricular noncompaction on the basis of clinical and echocardiographic findings. A cohort of 10 control subjects with normal global and regional left ventricular function also underwent cardiac MRI for comparative purposes.
 
“The hypothesis of the current study was that cardiac MRI may detect trabecular delayed hyperenhancement in a series of patient with left ventricular noncompaction and that the amount and degree of trabecular delayed hyperenhancement might be useful in quantifying the clinical stage of the disease,” the authors wrote.
 
All patients in the study had a cardiac MRI performed on a 1.5-Tesla system using an eight-element phased-array cardiac coil for signal reception. The scientists obtained left ventricular function with cine images using a steady-state free precession technique in two-chamber, four-chamber, and short-axis planes.
 
After baseline imaging was performed, a delayed hyperenhancement MRI was conducted using an inversion recovery prepared gated fast gradient-echo pulse sequence, 10 to 12 minutes after a bolus injection of gadopentetate dimeglumine. According to the authors, delayed hyperenhancement images were acquired to optimally show normal myocardium and trabeculae and regions of delayed hyperenhancement with the myocardium and trabeculae with the proper selection of varying inversion time (T1) values. (See Figure 1)

  
Figure 1*  
  
Figure 2*  
  
Figure 3*
The images were interpreted by a cardiac radiologist who was blinded to the diagnosis and clinical severity of the cases. To determine left ventricular noncompaction, segmental analysis was evaluated, although the apex segment was excluded because it is normally thin and may lead to false-positive interpretations, the authors noted.

Cine short-axis images were evaluated using Simpson’s method for calculation of ejection fraction, end-diastolic volume, end-systolic volume, and myocardial mass. Ventricular wall motion abnormalities were defined, and regional wall motion was scored on a 5-point scale. In addition, the distribution of noncompacted to compacted myocardium was quantitatively analyzed. (See Figure 2)

The researchers measured the degree of trabecular delayed hyperenhancement by placing a region of interest in the trabeculae and a second region of interest in the middle myocardium of the corresponding myocardial segment at the same ventricular level. This process was conducted for each of 16 cardiac segments, and a ratio of trabecular to myocardial signal was calculated.

“We defined trabecular delayed hyperenhancement as present when the ratio of trabecular to corresponding myocardial signal intensity was ≥ 3<,” the authors wrote. (See Figure 3)

The scientists reported that for severity of left ventricular noncompaction, there were statistically significant differences in the anterior, anterolateral, and inferolateral segments among all clinical stage groups at the mid level and for all segments at the apical level. They found that for the extent of left ventricular noncompaction, there were statistically significant differences in the anterior, anterolateral, inferolateral, and inferior segments among all clinical stage groups at the mid level and for all segments at the apical level.  

They noted that there were statistically significant differences among all clinical stage groups at the mid level in the inferior segment and the anterior, lateral, and septal segment at the apical level for the degree of trabecular delayed hyperenhancement. Their research uncovered statistically significant differences among all clinical stage groups at the basal level in the anterior and inferolateral segments, inferior segment at the mid level, and all segments at the apical level for the amount of trabecular delayed hyperenhancement.
 
The correlation analysis of the team’s data found that the amount and degree of trabecular delayed hyperenhancement and the extent of left ventricular noncompaction correlated significantly with ejection fraction. They stated that regional wall motion abnormalities correlated significantly with the severity and extent of left ventricular noncompaction at the mid level; as well as with the amount and degree of trabecular delayed hyperenhancement at the mid and apical levels.
 
“For the amount of trabecular delayed hyperenhancement at the apical ventricular level, significant differences were found among the moderate and severe clinical stage groups and all other clinical stage groups compared with no significant differences in extent or severity of left ventricular noncompaction,” the authors wrote.
 
The researchers noted that their study was limited by the small number of patients and that left ventricular noncompaction is a rare cardiomyopathy that has yet to be comprehensively classified. They suggested that cardiac MRI studies with a larger number of patients with left ventricular noncompaction are needed to elucidate further the relationship between the syndrome and ventricular dysfunction.
 
However, on the basis of their findings, the authors believe that cardiac MRI can be useful in staging the disease.
 
“Evaluating the extent and severity of left ventricular noncompaction and trabecular delayed hyperenhancement may improve the ability of the clinician to predict the clinical stage of the disease,” they wrote.


*Cardiac MRI in 44-year-old woman with left ventricular noncompaction and severe clinical disease. See also Figures S1D and S1E, cine loops, in supplemental data online at www.ajronline.org.

Figure 1: Two-chamber steady-state free precession (SSFP) cine image shows left ventricular noncompaction (arrows) at mid and apical levels.

Figure 2: Delayed contrast-enhanced two-chamber image shows trabecular hyperenhancement (straight arrow). Note that even in segments with normal compacted-to-noncompacted myocardium ratio, there is trabecular hyperenhancement (curved arrow).

Figure 3: Delayed contrast-enhanced short-axis image shows characteristic dot-like pattern of hyperenhancement within thickened trabeculae (arrows).

Images and captions by permission of the American Roentgen Ray Society.