How to measure Post Repair Prv/iv Pressure ?
In the operating room, after coining of1 bypass and before removing cannulae the RV and LV pressures are measured. The pressures are measured using a large needle passed through right ventricle across the septum to LV. It is then withdrawn and RV and pressure taken. Alternately RV pressure measured by the needle is compared to the aortic pressure. Ideally the Prv/iv ratio should be less than 0.7. If a transannular patch has not been used and ratio is above 0.7, bypass is re-established and transannular patch is sutured in. In spite of that if ratio is above 0.8 pressures are taken at different levels in RV outflow, to localize the site of obstruction. It is then dealt with by extending the patch. Transoesophageal echo is also useful in localizing the site of obstruction. In spite of all measures if the pressure is still high it is accepted and patients RV pressure monitored in ICU. Over a period of hours the pressure may fall to acceptable levels. When the RV pressure is suprasystemic, bypass is re-established the ventricular septal patch is fenestrated leaving a 3-4 mm-sized VSD.
In infants the operation is at times carried out under deep hypothernlia and circulatomy arrest. The advantage is that there are only few cannulae coming in the way of the surgeon when the heal is so small.