Study patients
This study consisted of 74 consecutive patients who underwent de novo CRT implantation between January 2015 and July 2019. In addition, 8 patients with CRT upgrades from pacemaker or implantable cardioverter defibrillation (ICD) systems, which were guided by Inner-Cath only, were investigated. All patients received de novo CRT implantation or upgrade to CRT systems according to guideline indications (17) that included patients with NYHA classes II-III or IV despite optimal medical treatment, LV ejection fraction (LVEF) ≦ 35% and QRS duration ≧120ms, or LVEF <50% and expected high frequency right ventricular (RV) pacing. The patients with de novo CRT implantation were divided into two groups based on the type of guiding catheter used initially for LV lead placement (LV-LP), namely, 7Fr Inner-Cath (Inner-Cath group, N=42) and 9 or 10Fr Outer-Cath (Outer-Cath group, N=32). Outer-cath was selected as a first-line method in the first 32 patients. Inner-cath was selected as a first-line method in the latter 42 patients. This study was a non-randomized retrospective observational study. The research protocol had been approved by the local Research Ethics Committee. Informed consent was obtained in the form of opt-out.