Regional Patterns of Dyssynchrony: Lateral Wall Delay Is Desirable but Not Essential for Left Ventricular Remodeling in Biventricular Pacing

BACKGROUND: Tissue synchronization imaging (TSI), a parametric imaging technique based on tissue velocity imaging, often demonstrates patterns other than lateral delay in patients evaluated for cardiac resynchronization therapy (CRT). The prevalence of these patterns and their response to CRT has not been well described. We hypothesized that regional patterns of dyssynchrony might correlate with the extent of reverse remodeling. METHODS: A consecutive series of 32 patients underwent echocardiographic study prior to CRT implant and 3 months postimplant. TSI was used to color-code the time-to-peak positive systolic velocity at six basal and six mid-LV segments. Each patient was assigned to one of four groups based on the predominant location of greatest delay (≥ 2 segments): (1) posterolateral delay, (2) septal delay, (3) no dyssynchrony, or (4) other. RESULTS: Patients were classified as follows: posterolateral delay in 44% of patients (n = 14), septal delay in 28% (n = 9), no dyssynchrony in 16% (n = 5), and other pattern in 13% (n = 4). At 3-month follow-up, the group with the lateral delay pattern was associated with the greatest decrease in left ventricular end-systolic volume (LVESV) and the largest improvement in left ventricular ejection fraction (LVEF) (-45 mL and +9.3%, respectively, P < 0.05). The LVESV in the other three groups changed as follows: -24 mL (septal), -28 mL (no dyssynchrony), and -15 mL (other). Similar trends were observed for LVEF and left ventricular end-diastolic volume. CONCLUSIONS: Despite the presence of wide QRS and a left bundle branch block, the most delayed segment is not always the posterolateral wall. Posterolateral delay is associated with the best response to CRT, while other patterns respond at a lower magnitude.