Abstract
The aim of this study was to evaluate the left ventricular mechanical dyssynchrony (LVMD) and left ventricular dysfunction of patients in AAI, DDD and VVI pacing modes using real-time three-dimensional echocardiography (RT3DE) and tissue Doppler imaging (TDI). The results from the RT3DE and TDI were subsequently compared. Twenty patients with sick sinus syndrome (SSS) who had undergone the implantation of a dual-chamber pacemaker were enrolled in this study and the pacemakers were programmed to AAI, DDD and VVI modes, sequentially. The RT3DE and TDI parameters were obtained following pacing for 24 h in each mode. With RT3DE, we measured the systolic dyssynchrony indices, including Tmsv(16)-SD%, Tmsv(12)-SD%, Tmsv(6)-SD%, Tmsv(16)-Dif%, Tmsv(12)-Dif% and Tmsv(6)-Dif%, left ventricular end-diastolic volume (LVEDV), left ventricular end-systolic volume (LVESV) and left ventricular ejection fraction (LVEF), respectively. With TDI, we measured the standard deviation and the maximal difference in time from the QRS onset to the peak systolic velocity for 12 left ventricular myocardial segments, i.e. Ts-SD and Ts-Dif, respectively. The results showed that the Tmsv(16)-SD% and Ts-SD in the AAI mode were significantly lower than those in the DDD and VVI modes (P<0.05); however, there were no significant differences between the DDD and VVI modes (P>0.05). The LVEF in the AAI, DDD and VVI modes was 63.1±8.9, 58.6±11.2 and 57.9±7.6%, respectively (P>0.05). There were negative correlations between the LVEF and Tmsv(16)-SD% (r, -0.651; P<0.001) and Ts-SD (r, -0.649; P<0.0001). A moderate correlation (r, 0.698; P<0.0001) was observed between Tmsv(16)-SD% and Ts-SD. The concordance rate between Tmsv(16)-SD% and Ts-SD for detecting LVMD was 76%. This study showed that DDD and VVI pacing modes induced significant LVMD and a reduction in LVEF, unlike the AAI pacing mode. RT3DE and TDI were capable of objectively evaluating LVMD; however, each method had certain faults. At present, there is a lack of a uniform standard for assessing LVMD; therefore, the use of a variety of techniques and indices is necessary in order to comprehensively evaluate LVMD in patients with different cardiac pacing modes.