An exploratory study on coronary sinus lead tip three-dimensional trajectory changes in cardiac resynchronization therapy.

BACKGROUND: Prediction of response to cardiac resynchronization therapy (CRT) is still an unsolved major issue. The interface between left ventricular mechanics, coronary sinus (CS) lead, and pacing delivery has been little investigated. OBJECTIVE: To investigate CS lead tip movements at baseline and during biventricular pacing (BiV) in the hypothesis that they could provide some insights into left ventricular mechanical behavior in CRT. METHODS: Three-dimensional reconstruction of CS lead tip trajectory throughout the cardiac cycle using a novel fluoroscopy-based method was performed in 22 patients with chronic heart failure (19 men; mean age 70 ± 10 years). Three trajectories were computed: before (T-1) and immediately after (T0) BiV start-up and after 6 months (T1). CRT response was the echocardiographic end-systolic volume reduction ≥15% at T1. Metrics describing trajectory at T0, T-1, and T1 were compared between 9 responders (R) and 13 nonresponders (NR). RESULTS: At T-1 trajectories demonstrated heterogeneous shapes and metrics, but at T0 the variations in the ratio between the two main axes (S1/S2) and in the eccentricity were statistically different between R and NR, pointing out a trajectory's change toward a significantly more circular shape at BiV start-up in R. Remarkably, R and NR could be completely separated by means of the percent variation in S1/S2 from T-1 to T0 (R: 47.5% [31.5% to 54.1%] vs. NR: -25.6% [-67% to -6.5%]). This single marker computed at T0 would have predicted CRT response at T1. CONCLUSIONS: Preliminary data showed that CS lead tip trajectory changes induced by BiV were related to mechanical resynchronization.