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Cardiac resynchronisation therapy (CRT) is a routine treatment option for adult patients with chronic left ventricular (LV) failure due to idiopathic or ischaemic dilated cardiomyopathy associated with electromechanical dyssynchrony. Initial studies showed acute haemodynamic efficacy and subsequent controlled randomised trials confirmed reverse LV remodelling, functional improvement, decrease in heart failure hospitalisation, and decreased overall mortality. In both European1 and North American2 guidelines CRT is a class I (level of evidence A) therapy for patients with an LV ejection fraction ⩽35% and QRS ⩾120 ms who remain symptomatic (New York Heart Association (NYHA) functional class III–IV) despite optimal medical treatment. Smaller retrospective series, including two multi-centre surveys,3 4 have meanwhile shown a benefit of CRT in patients with congenital heart disease both for the acute manipulation of cardiac output after surgery for congenital heart defects, and for the management of chronic systemic ventricular failure. This review will summarise the use of temporary and permanent CRT on the background of the heterogeneity of this population in terms of age, structure and causes of electromechanical dyssynchrony, and give some practical hints for CRT application.
PATHOPHYSIOLOGY OF ELECTROMECHANICAL DYSSYNCHRONY
Electromechanical dyssynchrony causes a sequence of events which may result in pathological ventricular remodelling and eventually failure. These have been documented in animal experiments and confirmed subsequently in the clinical setting. Wymen et al5 studied mechanical LV deformation by segmental circumferential strain in dogs paced from the right ventricular (RV) apex. They found early contraction close to the pacing site with accompanying stretch of the remote segments, followed by subsequent contraction of late activated segments along with relaxation and stretch of the early activated sites. The group of Prinzen et al was able to show the consequences of dyssynchronous activation on local myocardial work with decrease in the early sites contracting with a low local …
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