Echocardiography and cardiac resynchronisation therapy, friends or foes?

Abstract

Echocardiography is used in cardiac resynchronisation therapy (CRT) to assess cardiac function, and in particular left ventricular (LV) volumetric status, and prediction of response. Despite its widespread applicability, LV volumes determined by echocardiography have inherent measurement errors, interobserver and intraobserver variability, and discrepancies with the gold standard magnetic resonance imaging. Echocardiographic predictors of CRT response are based on mechanical dyssynchrony. However, parameters are mainly tested in single-centre studies or lack feasibility. Speckle tracking echocardiography can guide LV lead placement, improving volumetric response and clinical outcome by guiding lead positioning towards the latest contracting segment. Results on optimisation of CRT device settings using echocardiographic indices have so far been rather disappointing, as results suffer from noise. Defining response by echocardiography seems valid, although re-assessment after 6 months is advisable, as patients can show both continuous improvement as well as deterioration after the initial response. Three-dimensional echocardiography is interesting for future implications, as it can determine volume, dyssynchrony and viability in a single recording, although image quality needs to be adequate. Deformation patterns from the septum and the derived parameters are promising, although validation in a multicentre trial is required. We conclude that echocardiography has a pivotal role in CRT, although clinicians should know its shortcomings.

Keywords: 3D echocardiography; Cardiac resynchronisation therapy; Deformation imaging; Dyssynchrony; Echocardiography; Follow-up; Interobserver variability; Optimisation; Response; Septal strain; Speckle tracking echocardiography; Volume.

Fig. 1

The application of echocardiography in CRT. Echocardiography is mainly used to asses cardiac function and select patients by volumetric and subsequent ejection fraction assessment. Response is defined by determining change in volumetric status after a period of CRT and reverse remodeling. Dyssynchrony parameters based on Doppler measurements and/or strain analysis can further improve patient selection. Doppler measurements can also optimise CRT settings (i.e. atrio- and interventricular delays), while strain analysis can support LV lead optimisation strategies

Fig. 2

Central illustration. Role of echocardiography in CRT. Echocardiography can be used to select patients by volume and subsequent ejection fraction assessment and by dyssynchrony parameters based on Doppler and/or strain analysis. Doppler can also optimise CRT settings, while strain analysis could support LV lead optimisation strategies

Fig. 3

Schematic representation of apical rocking and septal flash. Schematic representation of the left ventricle in echocardiographic apical four-chamber view, showing both septal flash and apical rocking due to LBBB-induced mechanical dyssynchrony. a Early septal contraction stretches the lateral wall and rocks the apex to the left, while the septum thickens and moves inwards. b Late lateral wall contraction stretches the septum and rocks the apex to the right. c Relaxation of the lateral wall with continuing septal contraction, while the apex moves to its original position

Fig. 4

Example of echocardiographic data obtained from a responder to CRT. Apical four-chamber view, colour Doppler, septal strain and pulsed-wave Doppler acquisition of a responder to CRT, before, and 6 and 12 months after implantation. Note the continuous decrease in LV volume, decrease in mitral regurgitation, improvement in septal strain and decrease in IVMD over time. These data suggest a continuous process of reverse remodelling. Septal strain: yellow, light blue and green lines represent basal, mid and apical inferoseptal segmental strain, respectively. The three curves represent the segments illustrated in baseline echocardiogram in the upper left panel. The white dashed curve represents the average septal strain. SRSsept is marked red, as all rebound stretch after initial shortening, during systole. IVMD is represented by pulsed-wave Doppler signals of the left and right ventricular outflow tract. EDV end-diastolic volume, ESV end-systolic volume, EF ejection fraction, ΔESV change in ESV compared with baseline, SRS systolic rebound stretch, LVPEP left ventricular pre-ejection period, RVPEP right-ventricular pre-ejection period, IVMD interventricular mechanical delay. Volumes are derived by biplane Simpson’s method