Background-Left ventricular (LV) mechanical dyssynchrony (LVMD) has emerged as a therapeutic target using cardiac resynchronization therapy (CRT) in selected patients with chronic heart failure. Current methods used to evaluate LVMD are technically difficult and do not assess LVMD of the whole LV simultaneously. We developed and validated real-time 3D echocardiography (RT3DE) as a novel method to assess global LVMD. Methods and Results-Eighty-nine healthy volunteers and 174 unselected patients

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... eferred for routine echocardiography underwent 2D echocardiography and RT3DE. RT3DE data sets provided time-volume analysis for global and segmental LV volumes. A systolic dyssynchrony index (SDI) was derived from the dispersion of time to minimum regional volume for all 16 LV segments. Healthy subjects and patients with normal LV systolic function had highly synchronized segmental function (SDI, 3.5Ϯ1.8% and 4.5Ϯ2.4%; Pϭ0.7). SDI increased with worsening LV systolic function regardless of QRS duration (mild, 5.4Ϯ0.83%; moderate, 10.0Ϯ2%; severe LV dysfunction, 15.6Ϯ1%; P for trend Ͻ0.001). We found that 37% of patients with moderate to severe LV systolic dysfunction had significant dyssynchrony with normal QRS durations (SDI, 14.7Ϯ1.2%). Twenty-six patients underwent CRT. At long-term follow-up, responders demonstrated reverse remodeling after CRT with a significant reduction in SDI (16.9Ϯ1.1% to 6.9Ϯ1%; PϽ0.0001) and end-diastolic volume (196.6Ϯ17.3 to 132.1Ϯ13.5 mL; PϽ0.0001) associated with an increase in LV ejection fraction (17Ϯ2.2% to 31.6Ϯ2.9%; PϽ0.0001). Conclusions-RT3DE can quantify global LVMD in patients with and without QRS prolongation. RT3DE represents a novel technique to identify chronic heart failure patients who may otherwise not be considered for CRT. (Circulation. 2005;112:992-1000.)