 In particular sinus node dysfunction, atrial arrhythmias, ventricular arrhythmias including sudden cardiac arrhythmic death, heart failure due to anatomically right ventricular failure or venous obstruction at the level of the baffle or caval anatomy have been described.The high chance of developing arrhythmias results in up to 25% of patients who have undergone a Senning or Mustard procedure having a pacemaker by adulthood.Long term studies have disclosed that although from the functional capacity (NYHA Class) standpoint the Senning and the Mustard operation are similar, there is a higher risk of sinus node disease and arrhythmias with the latter.