Emerging role of three-dimensional speckle tracking strain for accurate quantification of left ventricular dyssynchrony.

A case was 53-year-old female with dilated-phase hypertrophic cardiomyopathy. She was classified as New York Heart Association functional class III heart failure despite receiving optimal medical therapy. The electrocardiogram taken showed intraventricular conduction delay with a QRS width of 194 msec. The left ventricular (LV) end-diastolic and systolic volumes, and ejection fraction (EF) were 101 mL, 68 mL, and 32%, respectively. The patient showed no significant mechanical LV dyssynchrony as evidenced by two-dimensional (2D) speckle tracking radial strain, which is defined as the time difference between anterior-septum and posterior wall, of 105 msec (<130 msec). Three-dimensional (3D) speckle tracking radial strain was performed for more detailed LV mechanical dyssynchrony analysis. An especially important finding for 3D speckle tracking radial strain analysis was that the average time-to-peak strain of 5 septum segments at 3 different LV levels (basal-anterior-septum, basal-septum, mid-anterior-septum, mid-septum, apical-septum) was significantly shorter than that of 5 posterolateral segments at 3 different LV levels (basal-posterior, basal-lateral, mid-posterior, mid-lateral, apical-lateral). This time difference between septum and posterolateral wall was 216 msec (204 msec vs. 420 msec), which was considered to indicate significant LV mechanical dyssynchrony (≥130 msec). 12 months after cardiac resynchronization therapy (CRT), EF had improved to 47%, while end-systolic and diastolic volumes had decreased to 88 mL and 47 mL, respectively, so that the patient was classified as a responder. In conclusions, a newly developed 3D speckle tracking strain can provide a comprehensive evaluation of "true" LV mechanical dyssynchrony from pyramidal 3D data sets acquired in the same beat, thus yielding more accurate information than previously possible with the 2D speckle tracking system.