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The major randomised trials that established the benefit of cardiac resynchronisation therapy (CRT) in congestive heart failure (CHF) all involved right and left ventricular pacing. Right ventricular (RV) pacing was used empirically with little relevance to haemodynamic benefit. The best site for left ventricular (LV) pacing via the coronary venous system is the mid-portion of the lateral or posterolateral wall in patients with LV septal–posterior wall mechanical dyssynchrony. It is thought that the widest separation of RV and LV leads produces the best CRT result. LV stimulation should be applied at the site of latest activation or latest contraction for the greatest haemodynamic response. The site producing the narrowest QRS complex during biventricular (BiV) pacing is of little value in determining the best LV pacing site to correct mechanical dyssynchrony. Placement of the LV lead is highly dependent on coronary venous anatomy, lead stability, pacing thresholds and the absence of phrenic nerve stimulation. In patients with ischaemic cardiomyopathy, a scar at the targeted site may cause failure of LV capture. The combination of the individually determined best RV site plus the individually determined best LV site may not necessarily provide the best arrangement for BiV pacing. The optimal combination for BiV pacing cannot be precisely determined at present.
RV PACING SITE
The optimal site for RV pacing in a CRT system remains controversial. The widely publicised adverse long-term effects of RV apical pacing for the treatment of bradycardia has created a shift of lead implantation to the RV outflow tract or septum, a practice based on faith rather than data. Yet, the RV apex still remains popular for implantable cardioverter-defibrillator (ICD) leads, supported by the prevailing belief that the apex guarantees the best lead stability and better defibrillation thresholds despite the documented equal performance of ICD leads implanted in the RV outflow tract …