Fumiko Sakamaki

Mechanical Dyssynchrony Assessed by Speckle Tracking Imaging as a Reliable Predictor of Acute and Chronic Response to Cardiac Resynchronization Therapy

Speckle tracking echocardiography (STE) has the potential to detect the heterogeneous initiation of active myocardial contraction, which is the primary cause of left ventricular (LV) systolic dysfunction in patients with mechanical dyssynchrony. This study was designed to assess the ability to predict response to cardiac resynchronization therapy (CRT) of STE-derived dyssynchrony parameters in comparison with invasive hemodynamic assessments. Thirty patients referred for CRT were studied. The time difference of first peak (Td-(first peak)) and the maximum peak (Td-(max peak)) on the radial strain-time curves of the earliest and the latest segments were measured as the dyssynchrony parameter. Peak positive dP/dt (dP/dt(max)) was measured as the indicator of global LV systolic performance. CRT responders were defined as patients with LV end-systolic volume reduction greater than 15% at 3 months after CRT. CRT increased the dP/dt(max) compared with the baseline study (P < .001). Percent changes in the dP/dt(max) (dP/dt(max)) were significantly correlated with Td-(first peak) (R = 0.743, P < .001), but weakly correlated with Td-(max peak) (R = 0.390, P = .03). Twenty patients (66%) were identified as chronic CRT responders. Receiver operating characteristics analysis revealed that Td-(first peak) shared a similar ability with dP/dt(max) to detect chronic responders (Td-(first peak) >167.0 ms, area under the curve [AUC] 0.945; dP/dt(max) >16.2%, AUC 0.934) compared with Td-(max peak) (>194.5 ms, AUC 0.820). STE-derived Td-(first peak) showed a reliable ability to predict the acute and chronic response to CRT as well as dP/dt(max).

Analysis of the Origin of Cardiac Wall Motion that Constitutes Myocardial Velocity-Time Curves in Patients with Left Bundle Branch Block

Septal and lateral wall myocardial velocity-time curves from tissue Doppler imaging were analyzed to determine wall motion from which the velocity originated in 34 patients with left bundle branch and systolic dysfunction (ejection fraction < 45%). Longitudinal strain rate by speckle tracking imaging was assessed to identify whether corresponding wall motion was active or passive. All lateral peak velocities during the ejection period were derived from delayed active movement. However, septal peak velocities were more numerous and complex. Septal peak velocities during pre-ejection were derived from the first active movement in 29 patients (85.2%). Septal peak velocities during the ejection period were derived from the second active movement in 20 patients, passive movement in 9 patients, and first active movement in 5 patients. Because septal peak velocities were consistent with various wall motion types, identification of the origin of septal peak velocities, including during pre-ejection, may be important in identifying LV dyssynchrony based on the propagation of first active myocardial movements.

Novel dyssynchrony evaluation by M-mode imaging in left bundle branch block and the application to predict responses for cardiac resynchronization therapy

BACKGROUND To determine an appropriate M-mode method in assessing left ventricular (LV) dyssynchrony in left bundle branch block (LBBB), and to assess feasibility of the method to predict cardiac resynchronization therapy (CRT) responses. METHODS AND RESULTS Fifty-one patients with LBBB were enrolled. Among them 31 patients underwent CRT. In addition to original septal to posterior wall motion delay (SPWMD), first peak-SPWMD was proposed as time of difference between the first septal displacement and the maximum displacement of the posterior. If an early septal point was not present, anatomical M-mode was used to visualize an early septal displacement spreading scan-area until inferoseptal wall. CRT responders were defined as LV end-systolic volume reduction (>15%) at 6 months after CRT. Twenty patients (65%) were identified as CRT responders. First peak-SPWMD in responders was significantly higher than those in nonresponders, although SPWMD did not differ between groups. Strong predicting ability of first peak-SPWMD was revealed (first peak-SPWMD: 80/90/83%; SPWMD: 35/100/58%), and area under the curve in receiver operating characteristic analysis of first peak-SPWMD (0.88) was significantly higher than that of SPWMD (0.61) (p<0.05). CONCLUSION In patients with LBBB, time differences between early septal and delayed displacement of posterolateral wall on M-mode images were the appropriate dyssynchrony parameter, and could improve the predictive ability for CRT responses.

Left bundle branch block and echocardiography in the era of CRT

Left ventricular (LV) dyssynchrony is a key pathophysiology in the era of cardiac resynchronization therapy (CRT). Left bundle branch block (LBBB) is the main substrate for CRT, and understanding the electrical pathophysiology is important in assessing the effects of CRT. Three-dimensional voltage mapping systems clearly demonstrate the typical propagation pattern characterized as propagation from the mid or apical septum to the lateral or posterior wall through the apex, which appears as a U shape. The electrical characteristics in LBBB closely associate with mechanical dyssynchrony, which is visualized as a septal flash motion. This rapid motion can be detected well by M-mode, tissue Doppler, and speckle tracking imaging. However, intraventricular discoordination between the septum and free wall is also a key to the response to CRT. We classified M-mode septum images into 10 patterns and septal strain pattern into two patterns. Through detailed analysis, we found that septal contraction contributes to intraventricular coordination. Therefore, in addition to septal flash, subsequent analysis of wall motion patterns also provides additional information about myocardial contractibility and the severity of electrical dyssynchrony. Recently, 3-dimensional speckle tracking imaging was introduced and used as a novel method to image electromechanical coupling. Because activation imaging by 3-dimensional speckle tracking can visualize similar U-shaped propagation images to those by 3-dimensional voltage mapping systems, it is hoped that this method will contribute to further research. Until now, it has not been fully understood how electrical dyssynchrony is expressed as mechanical abnormalities; therefore, continuous study will be required in the future.