Left Ventricular Outflow Tract Obstruction in Hypertrophic Cardiomyopathy: The Utility of Myocardial Strain Based on Cardiac MR Tissue Tracking

Abstract

Background: Myocardial strain for assessment of hypertrophic cardiomyopathy (HCM) is of importance and may play a role in identifying obstruction in HCM patients.

Purpose: To evaluate the utility of myocardial strain for detecting left ventricular (LV) outflow tract (LVOT) obstruction in HCM patients based on magnetic resonance tissue tracking.

Study type: Retrospective.

Population: In all, 44 adult HCM patients with LVOT obstruction and 108 adult HCM patients without LVOT obstruction.

Field strength/sequence: 1.5 T; Steady-state free-precession cine sequence; phase-sensitive inversion-prepared segmented gradient echo sequence for late gadolinium enhancement (LGE) imaging.

Assessment: Strain parameters including the local and global levels of LV myocardium and the subtraction (Sub) of myocardial strain variables between interventricular septal segments (IVSS) and noninterventricular septal segments (NIVSS) were measured for differentiating HCM with obstruction from nonobstruction. Average and maximum LV wall thickness (Average and Maximum LVWT) were also analyzed.

Statistical tests: Univariate and multivariate logistic regression analysis, area under the receiver operating characteristic (ROC) curve (AUC), intraclass correlation coefficient.

Results: In multivariate analysis, Average LVWT, Maximum LVWT, and the subtraction of radial peak strain (Sub Radial PS) between NIVSS and IVSS were independently associated with LVOT obstruction. The AUCs were 0.731, 0.840, and 0.890 for Average LVWT, Maximum LVWT, and Sub Radial PS, respectively. Sub Radial PS (cutoff value: 8.1%) demonstrated the highest sensitivity of 75.0% and a high specificity of 87.9% for identifying LVOT; Maximum LVWT (cutoff value: 22.9 mm) showed good sensitivity (72.7%) and specificity (83.3%). Combining Maximum LVWT >22.9 mm and Sub Radial PS > 8.1% achieved a better diagnostic performance (specificity 95.4%, sensitivity 70.5%).

Data conclusion: Combining Maximum LVWT >22.9 mm and Sub Radial PS >8.1% holds promise for objectively evaluating LVOT obstruction in HCM patients with very high specificity and acceptable sensitivity.

Level of evidence: 3 TECHNICAL EFFICACY STAGE: 2.

Keywords: hypertrophic cardiomyopathy; left ventricular outflow tract obstruction; strain.