Reply to Fluorescein Dye-Assisted Identification of Multiple VSDs.

Abstract

We would like to thank Drs Mathew and Baiju for keenly reading our article and for critically analyzing our technique. We would like to address each point one by one. First, with regard to the use of epicardial echocardiography as opposed to transesophageal echocardiography (TEE), we have also used epicardial echocardiography in our initial cases to confirm the adequate closure of ventricular septal defects (VSDs). However, after the availability of neonatal TEE probe at our institute, we have stopped doing epicardial echocardiography. In our experience, we don’t think TEE is inferior to epicardial echocardiography and we are satisfied with it. Regarding staining of fibrous tissue, we completely agree with the authors that prolonged exposure to high concentration of dye stains the fibrous tissue such as chordae and atrioventricular valve cusps. Therefore, in our article we have recommended the use of only a very small dose of dye, and a suction device is kept in both the left atrium and the right ventricle (RV) to prevent prolonged stay of fluorescein dye in the cardiac chambers. We have also mentioned in our article that the aortic root should be kept open while filling the left ventricle (LV) to prevent air embolism into the coronary arteries and leak of dye through iatrogenic coronary–cameral fistula in patients requiring RV muscle bundle resection. Regarding the use of a bulb syringe rather than a feeding tube, in our experience, we did not encounter any case of fatal intramyocardial injection. But, as there is always a risk of this complication, we always keep the tip of the feeding tube in the mid-LV cavity and fix the feeding tube in place with a prolene stitch to the interatrial septum to prevent its migration as explained in our article. We think the choice of either bulb syringe or plunger syringe depends upon the surgeon’s preference, and we are comfortable using the syringe with feeding tube as it provides more freedom to the surgeon’s hand and the operative field is not cluttered. Regarding detection of residual VSDs, our technique can be used for picking up of any VSD (additional or residual, postmyocardial infarction ventricular septal rupture, or iatrogenic VSD following ventricular muscle resection) and at any location. Regarding reliance on measurement of oxygen saturation step-up to diagnose residual shunting, in our study we routinely measured oxygen saturations and calculated the stepup, if present. But now, after our study, we have realized that if there is no significant residual VSD on saline injection, then there is no need to check oxygen saturation stepup and we have stopped this practice and we agree with the authors. Finally, regarding the use of bubble contrast injection into the left atrium and a brisk appearance of bubble contrast into the RV and pulmonary artery, we have used this method in a few of our earlier patients. We realized, this technique can pick up only moderate to large VSDs; small VSDs can still be missed. Moreover, this technique has disadvantage similar to earlier techniques i.e. patient must be weaned off from cardiopulmonary bypass (CPB) in order to ascertain the presence of any residual shunting. Further, closure of residual or additional VSD thus identified, requires the recommencement of CPB and predisposes the patient to its complications.