Quantification of Left Ventricular Systolic Dyssynchrony by Real-Time Three-Dimensional Echocardiography

Objective: To assess real-time 3-dimensional echocardiography (RT3DE)-derived left ventricular (LV) systolic dyssynchrony parameters: (1) normal values, (2) characteristics in patients with heart failure (HF) and a wide or narrow QRS complex, (3) interobserver and intraobserver variability with current state of the art RT3DE hardware and software technology, and (4) incremental value in patients with HF who receive cardiac resynchronization therapy (CRT). Methods: The study involved 84 patients with HF (mean age 54 ± 15 years, 50 men) and 60 healthy volunteers (mean age 41 ± 15 years, 36 men). Semiautomated LV endocardial border tracking was used to calculate regional time-to-minimum systolic volume and to generate parametric maps and the systolic dyssynchrony index (SDI), defined as the standard deviation of time-to-minimum systolic volume of the 16 LV segments expressed in percentage of R-R duration. Results: The volume rate of the RT3DE datasets in patients with HF was 31 ± 9 Hz (range 15-42 Hz). The normal value of the SDI was 4.1% ± 2.2% (range <1.0%-8.9%). Patients with HF had a larger SDI (13.4% ± 8.1%, P < .001). There was only a weak correlation (r2 = 0.07, P < .05) between the QRS duration and the SDI. Interobserver interclass correlation and variability of the SDI depended on image quality (good: 0.993 and 9%, moderate: 0.907 and 16%, respectively). Interobserver agreement for the identification of the most delayed LV segment depended on image quality (good: 90%, moderate: 76%). Thirty-nine patients underwent CRT. At the 12-month follow-up, LV volumetric responders had a significant reduction in the SDI (16.3% ± 3.3% to 7.7% ± 2.4%, P < .001). Conclusion: With state of the art technology, RT3DE allows reproducible assessment of LV systolic dyssynchrony, which may be useful to identify potential responders to CRT.

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