Analysis of three-chamber view conventional and tagged cine MRI in patients with suspected hypertrophic cardiomyopathy

Abstract

Objectives: To investigate the potential value of adding a tagged three-chamber (3Ch) cine to clinical hypertrophic cardiomyopathy (HCM) magnetic resonance imaging (MRI) protocols, including to help distinguish HCM patients with regionally impaired cardiac function.

Methods: Forty-eight HCM patients, five patients with "septal knuckle" (SK), and 20 healthy volunteers underwent MRI at 1.5T; a tagged 3Ch cine was added to the protocol. Regional strain, myocardial wall thickness, and mitral valve leaflet lengths were measured in the 3Ch view.

Results: In HCM, we found a reduced tangential strain with decreased diastolic relaxation in both hypertrophied (p = 0.003) and remote segments (p = 0.035). Strain in the basal septum correlated with the length of the coaptation zone + residual leaflet (r = 0.48, p < 0.001). In the basal free wall, patients with SK had faster relaxation compared to HCM patients with septal hypertrophy.

Discussion: The 3Ch tagged MRI sequence provides useful information for the examination of suspected HCM patients, with minimal additional time cost. Local wall function is closely associated with morphological changes of the mitral apparatus measured in the same plane and may provide insights into mechanisms of obstruction. The additional strain information may be helpful when analyzing local myocardial wall motion patterns in the presence of SK.

Keywords: Hypertrophic cardiomyopathy; Myocardial strain; Tagged MRI.

Fig. 1

a Schematic diagram of MV and SAM leading to LVOT obstruction in HCM [8]; b schematic 3Ch view of the heart. MV mitral valve, SAM systolic anterior motion, LVOT left-ventricular outflow tract. Note that protrusion of the residual leaflet can cause narrowing of the LVOT (effective LVOT)

Fig. 2

The tangential and radial strain directions projected onto the 3Ch view of the heart in the apical lateral wall at end-diastole (middle) and end-systole (right). The green arrows represent the wall-based (principal) coordinate system axes (T tangential, R radial). The black box represents the effects of motion-induced changes over the cardiac cycle in a local wall-based coordinate system. The initial black square oriented along the wall-based system (and inscribed in a unit circle) will be displaced, rotate, and become both stretched and sheared due to the motion, as illustrated by the black parallelogram (inscribed in a final ellipse) at end-systole. The dashed red box represents the effects of motion in a coordinate system based on the local principal strain directions. The dashed red square initially oriented along the principal strain directions (and inscribed in the same unit circle) is transformed into a rectangle by the motion, which will lie along the axes of the final circumscribing ellipse

Fig. 3

The 3Ch view at end-diastole (with tags still visible in the blood), with heart wall divided into 7 segments tracked throughout the cardiac cycle. Segment 1: basal septum; 2: midventricular septum; 3: apical septum; 4: apex; 5: apical free wall; 6: midventricular free wall; and 7: basal free wall. RV right ventricle, LV left ventricle, LA left atrium, Ao aorta

Fig. 4

Manual MV segmentation in the 3Ch view in representative HCM patients with and without LVOT obstruction. a closed leaflets and combined coaptation zone (CZ) + residual leaflet (RL) during systole. b same patient as (a), with open leaflets during diastole. c, d HCM with LVOT obstruction. e, f HCM without LVOT obstruction. Red: anterior leaflet; Green: posterior leaflet; Yellow: CZ + RL; Blue: effective LVOT width (distance between the anteriorly displaced combined CZ and basal septal bulge in case of LVOT obstruction, or smallest LVOT diameter without obstruction). Note that for the patients without obstruction, the posterior leaflet is either shorter or the coaptation zone is positioned further away from the LVOT, leading to absence of LVOT obstruction even in the presence of SAM (E)

Fig. 5

Tangential strain for base, mid, and apical segments of the septum (1, 2, and 3) and the free wall (7, 6, and 5), respectively, and the true apex [4]. The y axis in the graphs shows the fractional tangential strain, and the x axis shows time as fraction of the cardiac cycle

Fig. 6

LVOT distance as a function of basal septum wall thickness in HCM patients with and without LVOT obstruction (a); basal septal wall thickness as a function of age (b); principal strain components (P1 and P2) of the basal septum as functions of the basal septal thickness (c, d)

Fig. 7

Average tangential strain normalized to max systolic strain in the septal segments (basal, midventricular, and apical). The x axes show time as fraction of the cardiac cycle. The HCM segments show a slower relaxation compared to normal segments in the mid-diastolic phase, at 0.5 fractional time into the cardiac cycle. We note that, while the values of the normalized strain are in the range [0,1], the standard deviation for the entire patient subgroup overreaches this interval, due to differences in the absolute maximum strain of each patient

Fig. 8

Minimum principal strain shown as a color overlay at end-systole for a normal volunteer (left), septal knuckle (SK, middle), and HCM (right). The color bar indicates the strain; blue: negative strain; red: positive strain. Note that the patient with SK has near-normal septal strain compared to the patient with HCM