Abstract
Cardiac resynchronisation therapy (CRT) can profoundly improve outcome in selected patients with heart failure; however, response is difficult to predict and can be absent in up to one in three patients. There has been a substantial amount of interest in the echocardiographic assessment of left ventricular dyssynchrony, with the ultimate aim of reliably identifying patients who will respond to CRT. The measurement of myocardial deformation (strain) has conventionally been assessed using tissue Doppler imaging (TDI), which is limited by its angle dependence and ability to measure in a single plane. Two-dimensional speckle-tracking echocardiography is a technique that provides measurements of strain in three planes, by tracking patterns of ultrasound interference (‘speckles’) in the myocardial wall throughout the cardiac cycle. Since its initial use over 15 years ago, it has emerged as a tool that provides more robust, reproducible and sensitive markers of dyssynchrony than TDI. This article reviews the use of two-dimensional and three-dimensional speckle-tracking echocardiography in the assessment of dyssynchrony, including the identification of echocardiographic parameters that may hold predictive potential for the response to CRT. It also reviews the application of these techniques in guiding optimal LV lead placement pre-implant, with promising results in clinical improvement post-CRT.
Highlights
Heart failure can be defined as the inability of the heart to deliver oxygen to meet the metabolic requirements of the body, due to an abnormality in the cardiac structure or function (1)
In patients with sinus rhythm, Cardiac resynchronisation therapy (CRT) aims to restore atrioventricular (AV) synchrony. It has made a substantial improvement in the clinical outcomes in appropriately selected patients with heart failure (2) and is recommended in cases of drug-refractory New York Heart Association class II–IV symptomatic heart failure, an ejection fraction < 35% and ECG evidence of left bundle branch block (LBBB) (3)
Speckle-tracking echocardiography has built on this potential, and when radial strain data are used for guiding lead placement, improvements have been observed in left ventricle (LV) ejection fraction (28), LV reverse remodelling, all-cause mortality and heart failure hospitalisations, compared with discordant lead placement (37, 56)
Summary
Heart failure can be defined as the inability of the heart to deliver oxygen to meet the metabolic requirements of the body, due to an abnormality in the cardiac structure or function (1). In patients with sinus rhythm, CRT aims to restore atrioventricular (AV) synchrony. It has made a substantial improvement in the clinical outcomes (including hospitalisation and mortality) in appropriately selected patients with heart failure (2) and is recommended in cases of drug-refractory New York Heart Association class II–IV symptomatic heart failure, an ejection fraction < 35% and ECG evidence of left bundle branch block (LBBB) (3). Numerous echocardiographic indices of dyssynchrony have been evaluated, based on M-mode, pulsed Doppler and tissue Doppler (TDI) methods (6). They have yielded mixed results in their ability to predict CRT response, with observational studies demonstrating a link between the presence of dyssynchrony and an improvement post-CRT; larger trials show poor technique agreement and reproducibility (7, 8).
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