Assessment of ventricular dyssynchrony: global or regional function?

Abstract

A common cliche states that if you stand still every 10 years, you will find yourself in the forefront of fashion. Thus it seems with the analysis of ventricular function. It has been recognized for many years that incoordinate or non-uniform contraction reduces global left ventricular (LV) function. Wiggers demonstrated in 1922 that stimulation from a ventricular focus rather than supraventricular produced a reduced pulse pressure, prolonged isometric contraction, and systolic ejection time in normal hearts. Although regional wall motion abnormalities were recognized early in ischaemic heart disease, it was also demonstrated later that it occurs in dilated or hypertrophic cardiomyopathy.1 However, the realization that asynchronous wall motion due to delayed activation such as in the presence of a left bundle branch block profoundly affected global function did not take place until more recently.2 Developments in cardiac imaging have allowed us to appreciate how common delayed activation and dyssynchronous mechanical contraction are and the degree to which they affect overall ventricular efficiency. Even in the normal heart, there is some degree of dyssynchrony;3 and the normal QRS duration reduces with sympathetic stimulation, implying greater synchrony so that some of the improvement in ‘contractility’ is actually due to a reduction in asynchrony. In the original studies on contractility, the possibility of incoordination was never considered. In disease states, asynchronous activation has marked deleterious effects on ventricular pump function due to both inter- and intra-ventricular asynchrony, leading to prolonged contraction, reduced ejection time, delayed and prolonged relaxation, and reduced diastolic filling time. Lack of coordination between the two papillary muscles also creates mitral regurgitation, and the overall result is LV remodelling with increasing ventricular cavity volumes and a … *Corresponding author. Tel: +44 178255234; fax: +44 1782713071. E-mail address : john.sanderson{at}uhns.nhs.uk