Application of Quantitative Tissue Velocity Imaging to Evaluate Left Ventricular Early Diastolic Dysfunction in Dogs With Heart Failure Due to Rapid Ventricular Pacing

Abstract

The authors assessed the capability of quantitative tissue velocity imaging (QTVI) to detect left ventricular (LV) early diastolic dysfunction (LVEDDY) in a canine model. Rapid ventricular pacing (RVP) at 240 beats/min was maintained in 14 dogs for 2 weeks. Echocardiography, cardiac catheterization, and endomyocardial biopsies were performed at baseline, during pacing, and at 2 weeks. QTVI, conventional echocardiographic, and LV pressure and pathologic indices were measured, and correlations were analyzed during the progressive development of diastolic dysfunction produced by RVP. Receiver operating characteristic (ROC) curves of QTVI parameters were analyzed to identify predictors of LVEDDY. The onset of LVEDDY occurred 24 hours after RVP initiation. Most of the QTVI indices were altered at 12 or 24 hours after RVP onset. New parameters were identified, including time-R and time-E', which are the times from aortic valve closure to peak isovolumetric relaxation (R) and peak early diastolic velocity (E'), respectively, as well as the ratios of peak myocardial systolic velocity (S') and peak E' to R (S'/R and E'/R, respectively), which significantly changed during RVP. These parameters were correlated with LV -dp/dt(max) or LV end-diastolic pressure, but time-R, time-E', and S'/R were not correlated with heart rate. In addition, using ROC analysis, time-R had the largest area under the curve to predict LVEDDY after RVP. QTVI is a sensitive and specific quantitative method that can be used for the early detection of LVEDDY under tachycardic conditions. The novel indices described here, including time-R, time-E', and S'/R, can serve as effective, noninvasive, possibly heart rate independent LVEDDY markers.