Case Report: Navigating the flow-dependent interaction between the left internal mammary artery graft and the left anterior descending artery: when deliberate graft occlusion comes into play.

BACKGROUND: The left internal mammary artery (LIMA) graft constitutes the optimal conduit for bypassing the left anterior descending (LAD) artery. Despite its overall excellent long-term patency, the LIMA graft may fail, most commonly because of competitive flow. In case of a failed LIMA graft, a percutaneous coronary intervention (PCI) of the LAD artery may be required to ensure better outcomes. However, persistent competitive flow from an anatomically patent but functionally occluded LIMA graft after a successful PCI of the LAD artery may adversely affect clinical outcomes by predisposing to in-stent restenosis (ISR) and stent thrombosis. CASE SUMMARY: Herein, we present the case of a patient with unstable angina and a failed LIMA graft exhibiting the "string phenomenon" because of competitive flow, necessitating a PCI of a high-grade stenosis in the LAD artery. Reverse LIMA graft flow, which is an indicator of severe competitive flow, was observed immediately after the PCI and during follow-up angiography, which also revealed an ISR of the LAD artery. Stent failure was attributed to the persisting competitive flow and was managed with drug-coated balloon angioplasty. In order to nullify any future deleterious effects of the competitive flow, we applied the "condom technique" to sacrifice the dysfunctional LIMA graft. The first attempt to apply this technique was complicated by the dislodgment of the remnant balloon from the assembly and migration into the distal LAD artery; however, the second attempt was successful in achieving graft occlusion. The patient was discharged home in good condition and remained free of angina or any cardiovascular events at a 6-month follow-up. An angiogram performed seven months after the drug-coated balloon angioplasty for ISR and occlusion of the LIMA graft showed preserved patency of the LAD artery. CONCLUSION: Deliberate occlusion of a dysfunctional LIMA graft following a PCI of the LAD artery may help reduce the risk of future episodes of stent failure. Choosing to sacrifice the graft using the "condom technique" is feasible, safe, and effective, provided all steps of the technique are thoroughly reviewed and optimally performed.