Marked regional left ventricular heterogeneity in hypertensive left ventricular hypertrophy patients: a losartan intervention for endpoint reduction in hypertension (LIFE) cardiovascular magnetic resonance and echocardiographic substudy

Abstract

Concentric hypertensive left ventricular (LV) hypertrophy is presumed to be a symmetrical process. Using MRI-derived intramyocardial strain, we sought to determine whether segmental deformation was also symmetrical, as suggested by echocardiography. High echocardiographic LV relative wall thickness in hypertensive LV hypertrophy allows preserved endocardial excursion despite depressed LV midwall shortening (MWS). Depressed MWS is an adverse prognostic indicator, but whether this is related to global or regional myocardial depression is unknown. We prospectively compared MWS derived from linear echocardiographic dimensions with MR strain(in) in septal and posterior locations in 27 subjects with ECG LV hypertrophy in the Losartan Intervention for Endpoint Reduction in Hypertension Study. Although MRI-derived mass was higher in patients than in normal control subjects (124.0+/-38.6 versus 60.5+/-13.2g/m(2); P<0.001), fractional shortening (30+/-5% versus 33+/-3%) and end-systolic stress (175+/-22 versus 146+/-28 g/cm(2)) did not differ between groups. However, mean MR(in) was decreased in patients versus normal control subjects (13.9+/-6.8% versus 22.4+/-3.5%), as was echo MWS (13.4+/-2.8% versus 18.2+/-1.4%; both P<0.001). For patients versus normal control subjects, posterior wall(in) was not different (17.8+/-7.1% versus 21.6+/-4.0%), whereas septal(in) was markedly depressed (10.1+/-6.6% versus 23.2+/-3.4%; P<0.001). Although global MWS by echocardiography or MRI is depressed in hypertensive LV hypertrophy, MRI tissue tagging demonstrates substantial regional intramyocardial strain(in) heterogeneity, with most severely depressed strain patterns in the septum. Although posterior wall 2D principal strain was inversely related to radius of curvature, septal strain was not, suggesting that factors other than afterload are responsible for pronounced myocardial strain heterogeneity in concentric hypertrophy.

Figure 1

MRI short-axis tissue tags in a normal subject illustrating normal wall thickness and high-resolution tagging. Vertices of tagging stripes at end diastole (A) and end systole (B) were tracked yielding circumferential and radial strain. Visual inspection alone reveals normal septal deformation.

Figure 2

MRI tissue-tagged images in a patient with hypertensive LVH with increased wall thickness. Visual inspection reveals diminished septal deformation between end diastole (A) and end systole (B).

Figure 3

Short-axis view depicting MRI interrogations similar to echocardiography in the parasternal-long axis. The anterior septum is between regions 1 and 2. The posterior wall is between 3 and 4. Note the midwall triangulation tiling deformation pattern used to determine strain between end diastole and end systole.

Figure 4

Bar graphs of radial (A) and circumferential (B) posterior wall strain∈ expressed as the percentage of deformation (%) in patients vs normal control subjects (P value not signifi-cant for both).

Figure 5

Bar graphs of radial (A) and circumferential (B) septal strain∈ expressed as the percentage of deformation (%) in patients vs normal control subjects (*P<0.001).

Figure 6

Circumferential strain is displayed every 20° around the LV short axis. Zero degrees corresponds with interventricular septal-anterior wall junction, progressing in a clockwise direction (observed from the apex) through 360°. Squares indicate patients; triangles, control subjects. Data are means±SEs. The anterior septum (AS; 315° to 360°) and inferolateral walls (PW; 135° to 180°) are highlighted in gray. In LVH, anteroseptal circumferential strain is markedly depressed vs the inferolateral wall, whereas the 2 regions are indistinguishable in normal control subjects. Fitting a sine function curve to the radial distribution of circumferential strain (fit comprises amplitude, mean level, and phase) revealed that the 2 curves are significantly different in their means (P<0.0001), further supporting markedly altered circumferential strain patterns in LVH despite preserved LV function. B, Short-axis schematic for the regions of interest.