Complete atrioventricular block after isolated aortic valve replacement.

BACKGROUND

Temporary atrioventricular (AV) conduction disturbances are a common complication following cardiac surgery, especially involving the aortic valve. Permanent complete AV block is a serious and rare complication. Its prevalence has been estimated at 3-6% of all patients undergoing aortic valve replacement. Identification of factors that affect the occurrence of complete AV block requiring permanent pacemaker implantation might help reduce the risk of this problem in the future.

AIM

To evaluate clinical, anatomical and surgical factors that might affect occurrence of complete AV, resulting in the need for permanent pacemaker implantation.

METHODS

In our prospective study, we analysed clinical data of consecutive 159 patients operated due to isolated aortic valve disease between February 2011 and March 2012. Patients with a pacemaker implanted before that time were excluded from the study. The main indication for surgery was aortic stenosis (n = 114, 71.7%). Infectious endocarditis was an indication in 6 (3.8%) cases. Mean patient age was 65.3 ± 11.4 years, and the proportion of males to females was 56.6%/43.4%. Overall, 135 (84.9%) patients had sinus rhythm preoperatively. All operations were performed using median sternotomy, cardiopulmonary bypass, and hypothermia at 30-32°C. A biological prosthesis was implanted in 120 (70.4%) patients. Patients who needed an additional procedure such as another valve surgery, aortic surgery or coronary artery bypass grafting were excluded from the study.

RESULTS

Permanent pacemaker implantation was required in 11 (6.9%) patients. The pacemaker was implanted after at least 7 days of complete AV block which was then considered permanent. Univariate analysis showed that permanent pacemaker implantation was associated with prolonged cardiopulmonary bypass time, prolonged aortic cross-clamp time, and the occurrence of electrolyte disturbances. Univariate logistic regression revealed that the need for permanent pacemaker implantation depended on 5 factors including prolonged cardiopulmonary bypass time, prolonged aortic cross-clamp time, larger size of the implanted valve prosthesis, endocarditis as the indication for surgery, and electrolyte disturbances. In both backward and forward stepwise multivariate regression models, two parameters, prolonged aortic cross-clamp time and the presence of electrolyte disturbances, correlated with the occurrence of complete AV block.

CONCLUSIONS

Permanent complete AV block is a serious complication after aortic valve surgery. Of all analysed clinical, anatomical and surgical factors, prolonged cardiopulmonary bypass time, prolonged aortic cross-clamp time, larger size of the implanted valve prosthesis, endocarditis as the indication for surgery, and electrolyte disturbances were found to be statistically significant predictors of permanent pacemaker implantation.