P823Analysis of right ventricular mechanics by 2D speckle tracking echocardiography in patients with hypertrophic obstructive cardiomyopathy


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Abstract

Background: Hypertrophic obstructive cardiomyopathy (HOCM) is a condition mainly characterized by hypertrophy of the left ventricle and the interventricular septum. Measurement of myocardial strain (S) and systolic strain rate (SRs) by speckle tracking echocardiography (STE) is a non-invasive technique that can be used to evaluate myocardial mechanics.The right ventricle (RV) has rarely been evaluated by STE in patients with HOCM.The aim of this research project was to assess the longitudinal S and SRs of the RV in patients with HOCM and determine its usefulnessas a clinical tool to diagnose RV involvement.Methods: 30 HOCM patients vs. healthy controls were defined as the study group. Subjects with an implantable cardioverter-defibrillator (ICD), arrhythmia or poor RV image quality were excluded from the study.Echocardiography imaging was performed by a staff cardiac sonographer at the Mayo Clinic Echocardiography laboratory using a standardized protocol. Images were obtained at a mean frame rate of 40 ± 12 Hz in the patient group and 57 ± 22 Hz in the control group.Cine-loop clips were selected from long axis apical 4-chamber views. These images were exported and then analyzed with Syngo Velocity Vector Imaging software (VVI). The process consisted of a manual single frame tracing of the RV at end systole by a point-click approach. The tracing extended from the basal septum to the basal free wall. Based upon the shifting of the traced points, the software automatically calculated the strain and strain rate of the basal, mid and apical regions of the septal and free wall of the RV. Statistical Analysis:Data is presented as mean ± SD. The means and standard deviation (SD) for each variable were calculated. A t-Test was performed in order to assess the differences between both study groups. Receiver Operating Characteristic curves (ROC) and areas under the curve (AUC), Sensitivity (Sens) and specificity (Spe) were calculated for each variable in order to assess their diagnostic performance for HOCM.Results: Average age of HCOM patients was 58±12 Global RV strain was -15%±5 vs -20%±3 for controls. AUC for global RV strain was 0.84 (Sens 92%, Spe 73%) and 0.89 for systolic strain rate (Sens 85%, Spe 90%), AUC of S and SRs of the basal free wall was 0.86 with a P value of <.0001 vs. controls. After adjusting for LV basal inferoseptum strain it remained significant with an AUC of 0.94 and a Sens 86% and Spe 92% respectively with a P value of <.0001.Conclusions: To our knowledge this is the first study to prove that RV free wall mechanics measured by strain and strain rate are compromised in patients with HOCM.

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