Objectives Animal model of left bundle branch block (LBBB) is very important for basic study about cardiac resynchronisation therapy (CRT). But the preparation of LBBB model was difficult. This study was to explore the effect of radiofrequency catheter ablation of left bundle potential (LBP) on cardiac conduction and mechanical function in canines and evaluate the preparation method of LBBB model by RF catheter ablation.
Methods LBP was mapped and ablated by radiofrequency catheter in the left ventricular endocardium in 10 canines. The influence of LBP ablation on cardiac conduction and whether canine LBBB model was successfully created or not were observed. To assess the systolic and diastolic function of left ventricle, echocardiography was performed before and after LBBB model was successfully created.
Results After LBP ablation, LBBB was successfully created in 8 (80%) canines. Atrial and ventricular amplitude ratio (A/V) was less than 1:10 at successful ablation site and the interval of LBP to local ventricular potential (LBP-V) was 17.1 ± 3.2 msec, range from 12 to 22 msec. The QRS duration increased from 52.8 ± 4.8 ms to 100.5 ± 11.1 ms (P < 0.001) after LBBB created in these 8 canines, but there were no significant changes in PR intervals, AH and HV intervals after LBP ablation. In the remain 2 canines, a similar LBP potential was identified with LBP-V 30 and 32 msec, but complete AV block was produced during or after RF energy application. In 8 LBBB canines, echocardiography showed that systolic and diastolic functions were all decreased, includingleft ventricular ejection fraction and aortic blood flow velocity time integral reducing (P < 0.05), E/A lowering to < 1, E wave deceleration time and isovolumetric relaxation time prolonging (P < 0.05). Significant prolongation of septal-to-posterior wall motion delay and the increased difference of pre-ejection time (P < 0.001) implied intraventricular and interventricular desynchronisation after LBBB.
Conclusions Radiofrequency catheter ablation of LBP can made a high success rate of LBBB model in canine, but the risk of complete AV block exists. Immediately after isolated LBBB model was created, intraventricular and interventricular desynchronisation and left ventricular electrical activation delay occurred, which resulted in decreased cardiac systolic and diastolic functions.