Assessment of left ventricular dyssynchrony by three-dimensional echocardiography: Prognostic value in patients undergoing cardiac resynchronization therapy

Background: Systolic dyssynchrony index (SDI) using three-dimensional echocardiography (3DE) was shown to be a reliable measure of left ventricular (LV) dyssynchrony. However. the prognostic value of SDI on long-term outcomes after cardiac resynchronization therapy (CRT) remains unknown. Methods and results: A total of 414 patients (mean age 67 +/- 10 years, 60% ischemic etiology) with 3DE evaluation before CRT implantation were included. SDI was evaluated as continuous value and in quartiles. The study endpoint was combined all-cause mortality, heart transplantation, and LV assist device implantation. At baseline, median SDI was 8.0% (IQR 5.6-11.3%). During a median follow-up of 45 months (IQR 25-59 months), the endpoint was observed in 94 (23%) patients. SDI was independently associated with the endpoint together with ischemic etiology, diabetes, and renal function (HR 0.914, P = 0.003) after adjustment for age, atrial fibrillation, hemoglobin level, NYHA functional class, and posterolateral LV lead position. Patients from the 1st, 2nd, and 3rd SDI quartiles showed similar survival and superior as compared to the 4th quartile with the lowest SDI values (<5.5%; chi 2 : 30.4, log-rank P < 0.001). From receiver operating characteristic curve analysis, the optimal SDI cut-off value associated with the endpoint was >6.8% (area under the curve 0.634). Finally, a subgroup analysis (293 patients) demonstrated that a more pronounced reduction in SDI immediately after CRT (resynchronization) was independently associated with superior survival (HR 0.461, P = 0.011) after adjustment for prognostic relevant parameters. Conclusion: SDI is independently associated with long-term prognosis after CRT and might therefore be important to optimize risk-stratification in these patients.