[Non-surgical ventricular training before arterial switch. Focus on an animal model in lambs]

One of the conditions for successful anatomical correction of transposition of the great arteries (arterial switch) or of double discordance (double switch) is the ability of the subpulmonary left ventricle to adapt to the systemic circulation when restored to its subaortic position. A balloon catheter designed for training the subpulmonary ventricle by progressive occlusion of the main pulmonary artery (NuMed) was implanted in six lambs aged 45 days and inflated progressively to obtain the maximum tolerated right ventricular pressure. Six controls were instrumented without balloon inflation. The experiment lasted 5 days. Progressive inflation of the balloon to a right ventricular pressure70% of the systemic (carotid) pressure led to bradycardia with venous desaturation and acidosis which regressed when the balloon was deflated. In one animal, progressive adjustment enabled a right ventricular pressure of 75% of the systemic pressure to be obtained throughout the last day of the study. No significant right ventricular hypertrophy was obtained. The value of this technique is in assessing the afterload reserve of the tested ventricle before surgical banding of the pulmonary artery, the first step to anatomical correction for restoration of concordance of double discordance or of transposition of the great arteries previously treated by a Senning or Mustard procedure.