Visual LV motion and invasive LVdP/dtmax for selection and optimisation of cardiac resynchronisation therapy.

Echocardiography shows that multiphasic septal movement and a septal to lateral apical systolic left ventricular (LV) motion have a high predictive value for dyssynchrony and the response to cardiac resynchronisation therapy (CRT). Presence of dyssynchrony is also the major marker for CRT response in the presence of scar tissue, provided the interventricular (V-V) pacing interval is optimalised. For atrioventricular (AV) interval optimisation, the velocity-time integral of the transmitral flow has an excellent correlation with invasive LVdP/dt(max). In acute haemodynamic measurements, LVdP/dt(max) shows strongly the effect of AV and V-V optimisation. It also illustrates that the haemodynamic effect of LV pacing when associated with intrinsic conduction over the right bundle is equal to or better than biventricular pacing. We found that once AV and V-V interval were optimised, QRS morphology could be used as a template for optimal therapy. Automated continuous optimisation of the pacing intervals will be the big challenge for the future. (Neth Heart J 2008;16(Suppl1):S32-S35.).

Assessment of ventricular mechanical dyssynchrony by short-axis MRI.

Nowadays, patients with symptomatic heart failure and intraventricular conduction delay can be treated with a cardiac resynchronization therapy. Electrical dyssynchrony is typically adopted to represent myocardial dyssynchrony, to be compensated by cardiac resynchronization therapy. One third of the patients, however, does not respond to the therapy. Therefore, imaging modalities aimed at the mechanical dyssynchrony estimation have been recently proposed to improve patient selection criteria. This paper presents a novel fully-automated method for regional mechanical left-ventricular dyssynchrony quantification in short-axis magnetic resonance imaging. The endocardial movement is described by time-displacement curves with respect to an automatically-determined reference point. These curves are analyzed for the estimation of the regional contraction timings. Four methods are proposed and tested for the contraction timing estimation. They were evaluated in two groups of subjects with and without left bundle branch block. The standard deviation of the contraction timings showed a significant increase for left bundle branch block patients with all the methods. However, a novel method based on phase spectrum analysis shows a better specificity and sensitivity. This method may therefore provide a valuable prognostic indicator for heart failure patients with dyssynchronous ventricular contraction, adding new possibilities for regional timing analysis.

Contrast ultrasound methods for left-ventricle ejection fraction measurements.

The left-ventricle ejection fraction is an important cardiac-efficiency measure that is regularly used in cardiology. Standard estimations are based on time-consuming geometrical analysis and modelling, which requires experienced cardiologists. Alternative methods are very invasive due to the need for cardiac catheterization. In this paper we present and study a minimally-invasive indicator dilution technique for ejection fraction quantification that has recently been developed. It is based on a peripheral injection of an ultrasound contrast agent bolus. Left-atrium and left-ventricle acoustic intensities are recorded versus time by transthoracic echocardiography during contrast bolus passage. The measured curves are corrected for attenuation distortion, filtered to suppress the measurement noise, and processed by an adaptive Wiener deconvolution algorithm for the estimation of the left-ventricle impulse response. The estimated impulse response is interpolated by a mono-compartment exponential model for the ejection fraction assessment. An adaptive search of the interval for the model fitting is also included. The feasibility of the method is tested on 52 measurements in patients with left-ventricle ejection fractions between 10% and 80%. The results are promising and show a 0.83 correlation coefficient with echographic biplane ejection fraction measurements.