Mycobacterial infections following heart valve replacement

Mycobacterial infection is an uncommon but very serious complication of heart valve replacement and other forms of cardiac surgery. Tuberculosis has been a rare complication of valve replacement in the industrially developed countries owing to the low incidence of that disease in such countries. Most reported cases are associated with the insertion of human allograft valves. Valvular tuberculosis could become a more serious problem if heart valve replacement surgery is used to any extent in countries where tuberculosis is common. The majority of other mycobacterial infections occurring after heart surgery have, for unknown reasons, been due to the rapid growers M. chelonae and M. fortuitum. Porcine xenograft valves have been contaminated by M. chelonae, possibly during manufacture as this is not a natural pathogen of pigs. A minority of patients receiving valves known to be contaminated by M. chelonae subsequently developed valve disease. Mycobacterial disease following insertion of mechanical valves is a very uncommon occurrence but the prognosis is poor. There have been several outbreaks of infection of the sternotomy wound by M. chelonae and M. fortuitum and, although the prognosis is better than for mycobacterial endocarditis, treatment, especially for infections due to M. chelonae, often involves extensive debridement including removal of the entire sternum. In view of the poor response to therapy, prevention by avoidance of contamination of all surgical materials, including implanted valves, by environmental mycobacteria is of paramount importance.