Abstract 12700: Novel Method For Noninvasive Myocardial Work Analysis in Patients With Left Bundle Branch Block
Background: Left bundle branch block (LBBB) causes a heterogeneous work distribution in the left ventricle (LV). The aim of cardiac resynchronization therapy (CRT) is to synchronize LV contraction which in turn leads to improved pump function and reverse remodeling. Currently work analysis relies on invasive pressure measurements. In the present study we introduce a new noninvasive LV pressure (LVP) analog and validate its ability to assess regional work in combination with strain measurements by echocardiography.
Methods and Results: In patients with LBBB (n=12) and ischemic cardiomyopathy (n=6) we measured segmental strain by speckle tracking echocardiography and LVP by micromanometry. LVP traces from all patients were pooled and synchronized by identifying timing of opening and closing of the mitral and aortic valves for each of the pressure traces and stretching/compressing the traces along the time axis making valvular events coincide for all recordings. The profile of the averaged waveform could then be fitted to the relevant cardiac cycle by adjusting the duration of time intervals to match the actual valvular timing as determined by ultrasound imaging from a specific subject. Brachial cuff pressure was used to scale peak systolic pressure. Segmental work was calculated using two approaches: 1. As the area of the LVP-strain loops. 2. As the area of the LVP analog-strain loops. Work analysis using the two methods showed a good correlation (r=0.99) and agreement (mean difference ± 2SD, 3.5 ± 194 mmHgx%) (Figure 1). Figure 2. shows work loops for a septal segment in a patient with CRT on and off using the two approaches.
Conclusions: The use of a pressure analog allows for noninvasive work analysis based on echocardiographic imaging, systolic blood pressure and valvular timing. In a clinical setting this can be used to assess regional myocardial function which may serve as an important clinical tool when evaluating patients for CRT and optimizing device settings.
- © 2011 by American Heart Association, Inc.