Echocardiography, dyssynchrony, and the response to cardiac resynchronization therapy

Abstract

Biventricular pacing or cardiac resynchronization therapy (CRT) has been a considerable advance in the therapy of chronic heart failure. However, it is clear that not all patients benefit either in terms of symptoms or cardiac function, and some may be worsened by CRT. In this review, we consider the arguments, both clinical and economical, in favour of improved selection of patients for CRT other than those in current guidelines. It also seems clear that the fundamental mechanism of CRT is correction of dyssynchrony, and we review the various methodologies available to detect dyssynchrony. Other factors are probably also important in determining outcomes such as lead position, the extent and form of myocardial damage, optimizing pacemaker performance, and clinical expertise. The potential costs of inappropriate CRT implantation are high to our patients and to the health economy, and it behooves the cardiology community to develop better selection criteria. The current guidelines can and should be improved.

Figure 1

A patient fulfilling the criteria for cardiac resynchronization therapy with significant systolic dyssynchrony by tissue Doppler imaging. The measured baseline dyssynchrony index from three apical views was 52.6 ms (normal cut-off value is 33 ms) (A) and LV end-systolic volume decreased from 131 (B) to 67 mL (C) after CRT (reduced by 49%).

Figure 1

A patient fulfilling the criteria for cardiac resynchronization therapy with significant systolic dyssynchrony by tissue Doppler imaging. The measured baseline dyssynchrony index from three apical views was 52.6 ms (normal cut-off value is 33 ms) (A) and LV end-systolic volume decreased from 131 (B) to 67 mL (C) after CRT (reduced by 49%).

Figure 2

A patient fulfilling the criteria for cardiac resynchronization therapy but without systolic dyssynchrony by tissue Doppler imaging. The measured baseline dyssynchrony index from three apical views was 18.8 ms (normal cut-off value is 33 ms) (A) and LV end-systolic volume decreased only from 94 (B) to 90 mL (C) after CRT (reduced by 4%).

Figure 2

A patient fulfilling the criteria for cardiac resynchronization therapy but without systolic dyssynchrony by tissue Doppler imaging. The measured baseline dyssynchrony index from three apical views was 18.8 ms (normal cut-off value is 33 ms) (A) and LV end-systolic volume decreased only from 94 (B) to 90 mL (C) after CRT (reduced by 4%).

Figure 3

An echocardiographic mid-ventricular short-axis view used for speckle-tracking radial strain. The right panel shows time strain curves from six representative segments in a patient with left bundle branch block before cardiac resynchronization therapy. The yellow line is the anterospetum, which demonstrates early peak strain (arrow), and the purple line is the posterior wall, which demonstrates delayed peak strain (arrow), consistent with significant dyssynchrony.

Figure 4

An echocardiographic image from a patient with left bundle branch block of three-dimensional speckle tracking strain acquired from a pyramid of data with colour coding of peak strain as orange–yellow. The right panel shows 16 corresponding time-strain curves from standard left ventricular segments demonstrating septal curves with early activation, and free-wall curves with late activation, consistent with significant mechanical dyssynchrony.

Figure 5

A heart failure patient had dyssynchrony measured by real-time 3D echocardiography before (A) and after (B) receiving cardiac resynchronization therapy (CRT). Before CRT, there was variation in the time to minimal regional volume (arrows), and parametric imaging confirms paradoxical movement over inferior septum and posterior wall. These changes were normalized after CRT.

Figure 6

A heart failure patient with normal QRS duration and significant systolic dyssynchrony by tissue Doppler imaging. The measured baseline dyssynchrony index from three apical views was 43.1 ms (normal cut-off value is 33 ms) (A) and LV end-systolic volume decreased from 106 (B) to 62 mL (C) after cardiac resynchronization therapy (reduced by 41%).

Figure 6

A heart failure patient with normal QRS duration and significant systolic dyssynchrony by tissue Doppler imaging. The measured baseline dyssynchrony index from three apical views was 43.1 ms (normal cut-off value is 33 ms) (A) and LV end-systolic volume decreased from 106 (B) to 62 mL (C) after cardiac resynchronization therapy (reduced by 41%).