Introduction The aim of this study was to observe the incidence of CRT nonresponse in our center and investigate the possible reasons to lead to CRT nonresponse.
Methods 112 patients with CRT implantation were included in this study. There were 33 with ischaemic heart disease and 79 with non-ischaemic heart disease, 23 patients with permanent atrial fibrillation, 59 in NYHA class III and 53 in class IV. Patients were followed up more than 1 year. CRT response was defined as the improvement in NYHA class of ≥1 grade and 6-min walk test (6-MWT) of ≥25% and/or the increase of left ventricular ejection fraction (LVEF) of ≥15%.
Results The all mortality was 11.61%, the reasons of death were due to heart failure aggravation in 3 patients, sudden death in 4, acute myocardial infarction in 2 and noncardiac death in 4. 82 patients had a positive CRT response, but the other 30 patients (26.79%) were nonresponse to CRT including 9 patients (8.04%) with no improvement in NYHA class, 6-MWT and LVEF. 21 patients (18.75%) with no improvement in LVEF but with significant improvement in NYHA class and 6-MWT. Among nonresponders 3 patients died for heart failure aggravation. The basal data before CRT implantation were comparable between CRT response group and nonresponse group (p>0.05). The age, gender, narrow QRS duration before CRT and increased QRS duration after CRT did not impacted in CRT response (p>0.05). Permanent atrial fibrillation (AF) did not lead to CRT nonresponse, among them the incidence of nonresponse was not more than in patients without AF (17.39% vs 25.84%, p>0.05). There was also no relation between different RV pacing leads position and the incidence of CRT nonresponse (27.06% in RV apex leads vs 25.93% in RV septum, p>0.05). There were 6 patients with right bundle branch block (RBBB), 5 of them had nonrespons to CRT (83.33%, p<0.01). The patients with non-ischaemic heart disease had higher incidence than patients with ischaemic heart disease (32.05% vs 14.71%, p<0.05). LV lead positions can impact CRT response. The incidence of CRT nonresponse was 23.08% in lateral marginal, 22.22% in posterolateral vein, 38.10% in middle cardiac vein and 75% in great cardiac vein (p<0.01).
Conclusions The incidence of CRT nonresponse was higher in patients with non-ischaemic heart disease than with ischaemic heart disease since coronary angioplasty had been completed in the criminal vessels. Although QRS duration was obviously wider in RBBB, the incidence of CRT nonresponse was still significant increase. LV pacing lead positions was the crucial factor to response of CRT.