Echocardiographic Evaluation of Mechanical Dyssynchrony
- Jianwen WangEmail Jianwen Wang
- Sherif F. Nagueh
Congestive heart failure (CHF) is the leading cause of hospitalization1 and accounts for about 300,000 deaths in the United States.2 Global lett ventricular (LV) function can be compromised by either absolute decrease of myocardial contraction or discoordinate myocardial contraction of different segments, or both. In normal hearts, ventricular electric activation and contraction occur in a highly coordinated manner. However, among patients with systolic heart failure, the prevalence of intraventricular conduction delay is 30-50%. These patients have electrical and mechanical dyssynchrony.
In patients with left bundle branch block (LBBB), LV dyssynchrony results from delayed contraction of the LV free wall, Early septal contraction leads to stretching of the lateral wall during early systole; in turn, the delayed contraction of the LV lateral wall causes the septum to stretch during late systole, The early systolic stretch of the lateral wall and the late systolic stretch of the septum lead to delayed intraventricular pressure rise (dP/dt) and reduced cardiac output. LV dyssynchrony also induces pathological changes at the molecular, cellular, and tissue levels, contributing to the increased mortality and morbidity in patients with heart failure.3
Patients with heart failure and dyssynchrony may therefore benefit from therapies aimed at restoring synchrony. This can be achieved by atrial synchronized biventricutar pacing or LV pacing only, i.e., cardiac resynchronization therapy (CRT). In this procedure, a pacing lead is inserted close to the LV free wall through the cardiac veins in addition to RV pacing lead implantation.4 Early stimulation by LV pacing leads to earlier LV lateral wall contraction and an improvement in LV dyssynchrony.4
- Published on 1 Jan 2007
- Peer Reviewed