Takuya Omuro1, Takeshi Maruo2, Sachika Eguchi1, Yohei Yamanouchi1, Akiko Kurihara1, Hidefumi Chikuji1, Satoki Fujii2, Kazushige Kadota2, Kazuaki Mitsudo2
Kurashiki Central Hospital Department of Laboratory Medicine1, Department of Cardiology2

Background: Left ventricular (LV) dyscoordination were reported as a useful index for predicting the response to cardiac resynchronization therapy. However, it has not been clear that which factors influence on the dyscoordination in patients with electrical dyssynchrony. Thus, we evaluated the degree of LV dyscoordination in patients with right ventricular (RV) pacing by speckle tracking strain rate (SR) analysis.

Methods: Echocardiography was performed in 81 consecutive patients with RV pacing. As a dyssynchrony index, the time difference between 1st peak of LV septum and that of posterior wall (IVS-PW delay) was measured by M-mode at the mid-LV level. We used off-line software EchoPAC (GE Ultrasound) for SR analysis and measured radial SR at mid-LV short axis view. The dyscoordination index (DI) was defined as the ratio of average myocardial thinning (negative SR) to thickening (positive SR) of 6 segments during the ejection period (Figure).

Results: Twenty-seven patients were LV ejection fraction (LVEF) <50% (lowEF) and 54 patients were >50% (highEF). Mean value of IVS-PW delay was 301±73ms, and there was no significant difference between IVS-PW delay of lowEF group and that of highEF group (304±50ms vs. 299±83ms, N.S.). DI of lowEF was significantly higher than that of highEF (28±23% vs. 8±10% , p<0.001). DI correlated with the LV end-systolic volume (r=0.536, p<0.001), QRS width (r=0.228, p=0.049) and LVEF (r=-0.625, p< 0.001). In multivariate analysis, the independent predictor of DI was LVEF (p < 0.001).

Conclusions: Dyssynchrony in patients with RV pacing was constantly high regardless of LVEF, while dyscoordination was enhanced by reduced LVEF. Reduced LV contractility with electrical dyssynchrony increased the dyscoordination and might cause a vicious circle of LV pump failure.