Long-term results after the Mustard operation - Its implications for the double switch operation -

Professor Emeritus, Department of Surgery, University of Toronto,
Toronto, Ontario, Canada
George A. Trusler

From May1963, when the first Mustard operation was done, to March of 2003, a total of 556 Mustard procedures were carried out at the University of Tronto. Most were for isolated or simple transposition（TGA）（n=365）or for TGA with ventricular septal defect（VSD）（n=73）. Survival, both early and late, is better for the isolated TGA group（78% at 40 years）compared to only 31% at 40 years for TGA, VSD.
  A protocol for arterial switch repair for TGA VSD began in 1978 and improved survival to 77% at 20 years.
  For simple TGA, after an initial learning curve, the mortality for Mustard repair decreased and, for the last 25 years, has become very low（less than 1%）. However, late complications and late mortality were sufficient to warrant a change to the arterial switch operation for simple TGA in 1987. Despite an initial higher mortality for the arterial repair, the 15 year survival for isolated TGA is similar（89% for arterial switch and 87% for Mustard）.
  Both arrhythmia and ventricular dysfunction are important late complications after Mustard's operation. Both are time dependent. Freedom from pacing after the Mustard operation is lower in the TGA/VSD group than for simple TGA（53% versus 72%）. Pacing is seldom required following the arterial switch operation.
  Baffle complications, while not uncommon, occurred with less frequency in later year of the Mustard operation and only a small group required reoperation.
  Systemic ventricular dysfunction was observed in a third of the adult patients late after Mustard's operation. Of 20 patients with severe dysfunction late after transposition repair（Mustard 17, switch 3）, five were selected for late switch conversion at age 20 to 49 years. One of these had a cardiac transplant, 3 an arterial switch and one was debanded and underwent tricuspid valve replacement. One of the switch conversions is well and the other two are only marginally improved. It appears that LV reconditioning by PA banding is more effective in younger patients. Thirteen other patients were selected for transplant and 11 received an allograft with six survivors.
  A study of functional ability following the Mustard operation in children with transposition identified that two-thirds were in functional Class 1, 12% in Class 2 and 26% in Class 3. A review of the employment status of Mustard patients over age 18 years demonstrated that 57% are unemployed, 27% have part-time employment and only 24% full time, a lower level of employment than the normal population.
  While the Mustard operation was a major advance in the management of TGA in the 1960's through to the 1980's, the arterial switch operation has now superceded it with comparable early results and improved late results. Furthermore, children with the arterial switch scored significantly higher in a quality of life assessment in the areas of global health, physical functioning, pain and general health perception.
  The remaining potential use of the Mustard procedure is in the double switch operation for congenitally corrected transposition of the great arteries. Used in conjunction with either an arterial switch operation or Rastelli, the anatomic right ventricle then serves the pulmonary circulation thereby avoiding late right ventricular dysfunction and tricuspid valve problems. Both switch operations（arterial and venous）are now associated with low mortality. Baffle complications are uncommon. The only drawback, other than the magnitude of the combined operation, will be the risk of arrhythmias including the need for pacing secondary to the Mustard procedure.