Shortening of paced QRS complex and clinical improvement following upgrading from apical right ventricular pacing to bifocal right ventricular or biventricular pacing in patients with permanent atrial fibrillation.

BACKGROUND Cardiac resynchronisation therapy (CRT) using biventricular pacing (BVP) has been shown to improve survival in patients with chronic heart failure (CHF). However, BVP cannot be achieved in all patients because of technical problems. In such patients, bifocal right ventricular pacing (BFP) may be an alternative. AIM To analyse the relationship between changes in paced QRS complex width and clinical responses in previously conventionally paced patients, who underwent upgrading to BFP or BVP. METHODS A total of 34 patients (26 male, eight female) aged 53.4 to 84 years (mean age 70.3) with CHF, permanent atrial fibrillation and previous right ventricular apical pacing lasting 35.4-184.2 months (mean duration 92.2 months) due to primary or post-ablation (12 patients) atrioventricular block, were included in the study. The patients were split into two subgroups: in the first (ten patients), the cardiac pacing system was changed to BFP, whereas in the second (24 patients), BVP was performed. Over a 12-month period, the following changes were studied: NYHA classification, brain natriuretic peptide levels (BNP), distance covered in a six-minute walk test (6MWT) and left ventricular ejection fraction (LVEF). The observation period was divided into two stages: the first six months after the pacing system was changed, and the six months following that. All 34 patients finished the first observation period, and 27 of them completed the second period. RESULTS Clinical improvement was observed in all the patients following the change of pacing system. The greatest clinical improvement occurred during the first stage of observation. At that time, a significant amelioration of HF, according to NYHA classification and improvement in LVEF and 6MWT were noted in both groups. Additionally, a significant improvement (reduction) of BNP level in the BVP subgroup was reported. In the second observation period, a further improvement in the LVEF value was observed in the BVP subgroup. A significant negative correlation between the relative shortening of QRS complex and relative change in LVEF was observed in the whole group, and in the BVP subgroup. CONCLUSIONS In patients with permanent AF the change of pacing site from right ventricular apex to BFP or BVP results in significant improvement in CHF symptoms. During long-term follow-up these changes are more prehounced in BVP than BFP patients. There is a correlation between shortened QRS complex duration and improvement of LVEF in BVP patients.