The assessment of diastolic blood flow field related energy loss of left ventricle in patients with right heart dual-chamber pacing using ultrasonic vector flow mapping

Objective To assess the changes of diastolic blood flow field and energy loss of left intra-ventricular flow in patients with heart dual-chamber pacing using ultrasonic vector flow mapping(VFM), and to explore the clinical value of VFM technology for the assessment of left ventricular diastolic function in patients with cardiac pacing. Methods After routine echocardiographic exam for 51 patients with dual-chamber pacing as pacemaker group and 73 volunteers as control group, the color Doppler flow imagings from standard dynamic apical two, three and four-chamber views for 3 completed cardiac cycles were acquired in VFM mode, and were imported to DAS-RSI workstation subsequently. The off-line measurement of diastolic left intra-ventricular flow for prescription parameter, such as energy loss, vortex area and vortex intensity, was performed. The left intra-ventricular parameters of two groups were compared for difference, and the correlationship between parameters at isovolumetric, early, mid and late diastolic phases was analyzed with SPSS 17.0 statistical software. Results 1) The energy losses of pacemaker group compared with the those of control group were significantly higher at isovolumetric, early, and late diastolic phases(Z=-6.689, -5.683, -3.014, -4.418, P<0.001), and at mild-diastole, energy loss was reduced mildly(Z=-3.014, P<0.05). 2) Vortical intensity of pacemaker group was significantly greater than that of the control group in isovolumic, early and late diastolic phases (t=2.388, 2.988, 3.153, P<0.05) separately, there was not statistically vertical intensity differences in mid-diastole between the two groups and no significant vortical area difference between the two groups. 3) There was no correlationship in the two groups for all the phases between energy loss and vertical area or intensity. For each phases, vortical area of the control group was correlated with vortical intensity(r=0.396-0.809, P=0.003-0.000). Only isovolumic vortical area was correlated with the vortex intensity in pacemaker group (r=0.807, P=0.000). Conclusions The dual-chamber pacing of right ventricle and right atrium could induce a significant energy loss of left intra-ventricular fluid and obvious abnormal distribution of eddies during diastole. The disappearence of correlationship between vertical area and intensity in cardiac pacemaker group during left diastole might lead to more turbulance flow and energy loss of left ventricle during right dual chamber pacing. Key words: Echocardiography; Ventricular function, left; Cardiac pacing, artificial; Vector flow mapping