Noninvasive assessment of intraventricular pressure difference in left ventricular dyssynchrony using vector flow mapping

Diastolic intraventricular pressure difference (IVPD) reflects left ventricular (LV) diastolic function. The relative pressure imaging (RPI) enables the noninvasive quantification of IVPD based on vector flow mapping (VFM) and visualization of regional pressure distribution. LV dyssynchrony causes deterioration of cardiac performance. However, it remains unclear how IVPD is modulated by LV dyssynchrony. LV dyssynchrony was created in ten open-chest dogs by right ventricular (RV) pacing. The other ten dogs undergoing right atrial (RA) pacing set at the similar heart rate with RV pacing were used as controls. Echocardiographic images were acquired at baseline and during pacing simultaneously with LV pressure measurement by a micromanometer. Pressure difference (ΔP) was computed between the apex and the base of the LV inflow tract during a cardiac cycle by RPI and ΔP during isovolumic relaxation time (ΔP_IRT), a parameter of diastolic suction, and that during early filling phase (ΔP_E) were measured. During RV pacing, stroke volume (SV) and ΔP_IRT decreased significantly, while ΔP_E did not change compared to the baseline. During RA pacing, SV, ΔP_IRT and ΔP_E did not change significantly. ΔP_IRT tended to correlate with –dP/dt_min and end-systolic volume, and significantly correlated with ejection fraction. IVPD during isovolumic relaxation time was decreased by LV dyssynchrony, while IVPD during early filling phase was not. A reduction of diastolic suction is observed in LV dyssynchrony and is significantly related to a decrease in SV.