Cardiac resynchronization therapy (CRT) is an
established therapeutic option in symptomatic heart failure with reduced
ejection fraction and evidence of left ventricular (LV) conduction delay (QRS
width ≥120 ms), especially when typical left bundle branch block is
present. The rationale behind CRT is restoration of aberrant LV electrical
activation. As there is considerable heterogeneity of the LV electrical
activation pattern among CRT candidates, an individualized approach with
targeting of the LV lead in the region of latest electrical activation while
avoiding scar tissue may enhance CRT response. Echocardiography, electro‑anatomic
mapping, and cardiac magnetic resonance imaging with late gadolinium
enhancement are helpful to guide such targeted LV lead placement. However, an
important limitation remains the anatomy of the coronary sinus, which often
does not allow concordant LV lead placement in the optimal region. Epicardial
LV lead placement through minimal invasive surgery or endocardial LV lead
placement through transseptal punction may overcome this limitation, obviously
with an increased complication risk. Furthermore, recent pacing algorithms
suggest superiority of LV-only versus biventricular pacing in patients with
preserved atrio‑ventricular (AV) conduction and a typical LBBB pattern. Finally,
pacing from only one LV site might not overcome the wide electrical dispersion
often seen in patients with LV conduction delays. Therefore, multisite pacing
has gained significant interest to improve CRT response. The use of multiple LV
leads may potentially lead to more favorable reverse remodeling, improved
functional capacity and quality of life in CRT candidates, but adverse events and
a shorter battery span are more frequent because of the extra lead. The use of
one multipolar LV lead increases the number of pacing configurations within the
same coronary sinus side branch (within small distances from each other)
without the use of an additional lead. Small observational studies suggest that
more effective resynchronization can be achieved with this approach. Finally,
there are many reasons for non‑effective CRT delivery in carefully selected
patients with an adequately implanted device. Multidisciplinary, post‑implantation
care inside a dedicated CRT clinic ensures optimal CRT delivery, improves
response rate and should be considered standard of care.
Credits: Pieter Martens; Frederik Hendrik Verbrugge; Wilfried Mullens