Retrograde Flow from the LAD into the LIMA with no Antegrade Flow Can Easily be Missed

Abstract

A 58-year-old anesthesia technician in our hospital was diagnosed as a case of triple-vessel coronary artery disease needing three grafts. He was taken to the operating room where a plan of grafting the LAD with a LIMA, a proximal and distal obtuse marginals with veins grafts was pursued. The LIMA flow was noticed to be sluggish after harvesting, and papaverin was injected into it with a moderately good response. A size 1 mm probe was then passed down the LIMA to release any proximal spasm. The flow increased dramatically after this manuever. The LIMA to LAD anastomosis was done using off-pump technique, which is practiced in more than 90% of CABGs in our center. After the completion of anastomosis, a transit time flowmetry probe was used to measure the flow in the graft, unfortunately, the flow was 0 mL/min with abnormal systolic peak in the flow curve and a pulsatility index of more than 30. Pulsatility index should not be more than 6 if there is a reasonable antigrade flow in the graft.Accordingly, a decision was made to open the graft through a proximal branch and then to pass a probe to check the anastomosis. Once the artery was opened, a huge flow of blood was observed, and a size 2.0-mm probe was passed easily across the anastomosis. A bulldog was then put across the LIMA between the anastomosis and the open brranch, and to our surprise there was no antigrade flow at all. The artery was examined fully and a very proximal hematoma was observed around the artery. The LIMA was transected distal to the hematoma and anastomosed as a free graft to the ascending aorte. Transit time flowmetry was repeated with very good diastolic flow and wave pattern and with a pulsatility index of only 1.7 DiscussionEarly detection of inadequate LIMA flow to LAD is essential as we know the importance of this particular graft in short-and long-term prognosis of patients. Strong retrograde flow can obviously mimic adequate LIMA antigrade flow in some cases, giving a false palpable pulse in the LIMA after completion of anastomosis.ECG is obviously expected to be normal as long as there are no anastomosis problems and accordingly cannot be used to guarantee adequate mammary flow.1 Transit time flowmetry seems to be an adequate and reliable tool in evaluating adequate intraoperative graft flow.2,3 It gives the surgeon three different parameters which collectively can indicate abnormal flow in graft. A pulsatility index greater than 6 and a peaked systolic rather than a diastolic flow curve coupled with a low flow clearly indicate an abnormal graft flow. 4,5 Unfortunately, and in a case such as ours, the absence of such a diagnostic facility means that the patient would have to come back within a short period with early recurrent angina. We have revised five grafts over the last two years for different technical error, and they were all detected using the transmit time flowmetry. We strongly recommend the use of this technique in all CABG cases, especially those which are done using the off-pump technique. Mohammed Fouda, MD