Influence of the Preimplantation QRS Axis on Responses to Cardiac Resynchronization Therapy

QRS Axis and the Benefit of Cardiac Resynchronization Therapy in Patients with Mildly Symptomatic Heart Failure Enrolled in MADIT‐CRT

“…This study is limited by its size and retrospective nature such that a definitive statement regarding the effect of LAD within the RBBB CRT population was not possible. It is also not known what the lead positions were within this study and as previously mentioned, 18 variations in CS lead position can have a significant effect on CRT response in patients with LAD acting to further limit the study's conclusions.…”

“…Examining the relationship between CRT efficacy and LAD further, coronary sinus (CS) lead position has also been shown to play an important role. Garcia et al 18 studied 78 patients with LBBB post implant of a CRT device and noted a significant increase in CRT efficacy (improvement in functional class, reduction in LVEF of 5%, no admissions for HF and alive through follow‐up) for patients with LAD. On the surface these findings stand in contrast to ours.…”

“…With the target CS lead position in the lateral position in MADIT‐CRT and LBBB LAD patients deriving a smaller benefit from CRT‐D it seems reasonable to hypothesize that the form of dyssynchrony seen in LAD LBBB patients may best be treated with an alternative lead placement. It should also be noted that the study by Garcia et al 18 included patients with advanced HF that may have derived a greater benefit from CRT. Further randomized controlled studies examining these conclusions and hypothesis are necessary to evaluate it definitively.…”

Influence of QRS duration and axis on response to cardiac resynchronization therapy in chronic heart failure with reduced left ventricular ejection fraction: A single center study including patients with left bundle branch block

“…Response to CRT was independently evaluated using two parameters: NYHA class for SR and LVEF for ER. SR was defined as improvement in NYHA classification by ≥ 1 class [6,8]. Improvement in absolute LVEF ≥ 10% was defined as ER.…”

“…However, a significant proportion of patients treated with CRT do not achieve the desired response, emphasizing the need for better selection criteria [5]. Previous studies have recognized some simple electrocardiographic parameters, such as QRS morphology, duration and axis, as predictors of response to CRT [6][7][8]. However, the data are still sparse and inconclusive, particularly with regard to the predictive role of QRS axis in CRT candidates, and no threshold values for QRS axis have been established so far regarding positive response to CRT.…”