Explain the Techniques of Operation used in post myocardial infarction ventricular septal defect?
Techniques of Operation : If the patient's condition is stable cardiac catheterisation, coronary angiography and left ventriculography are done. Otherwise patients are taken up based on echo and doppler studies. Pre-operative intra aortic balloon pump (IABP) and pulmonary arterial pressure monitoring (Swan-Ganz catheter) will be of great help. Operation can be safely postponed if there is:
1) Adequate cardiac output with no evidence of cardiogenic shock.
2) Absence of pulmonary oedema and pulmonary venous hypertension.
3) Absence of fluid retention on treatment with diuretics and digitalis.
4) Good renal function.
Patient should be under close observation during this period and urgent operation undertaken if there is deterioration. Haemodynamically compromised patients are taken up for surgery with a Swan
Ganz pulmonary arterial catheter in situ and on intra aortic balloon pumps (IABP). At times the surgeon may have to put the patient on cardiopulmonaty bypass under local anaesthesia using femoral arterial and venous cannulae before' anaesthesia. This helps to overcome haemodynamic collapse at the time of induction of anaesthesia.
Initial steps of the operation are the same as described for coronary artery bypass grafting. Saphenous vein is harvested during median stelnotomy and preparation for cardiopulmonaty bypass. Ascending aorta and superior and inferior vena cavae are cannulated and snares passed around both vena cavae preparatory to total cardio pulmonary bypass. Antegrade and retrograde cardioplegia through aortic root and coronary sinus are given for good myocardial protection.