Six of the 105 patients (6%) exhibited diffuse involution of the graft (string sign). These cases were analyzed individually.
Case 1
A 60-year-old male patient who had participated in CABG 4 years previously (LIMA-LAD, SVGA-RCA) underwent repeated coronary angiography because of chest pain and a positive stress test. The angiography revealed an unligated thick side-branch of the left mammary artery with a high run-off, which probably contributed to the string sign of the main branch of the mammary graft (Figure 1). The possibility of an intervention for the occlusion of the side-branch arose, but the significance of the original LAD lesion was questionable, and the patient later became free of angina due to aggressive medical therapy.
Case 2
A 62-year-old male, who had undergone bilateral mammary bypass grafting on the LAD and the right coronary artery (RCA) 4 years earlier. Coronary angiography showed an almost occluded LIMA graft (string sign) (Figure 2A) with 50-60% stenosis on the proximal part of the LAD (Figure 2B). The anatomosis of the right IMA graft displayed a high-grade stenosis. The previous myocardial scintigraphy revealed a reversible perfusion defect on the inferior wall, while pressure wire measurement on the LAD proved that the lesion of the LAD was not associated with a significant pressure gradient even during vasodilatation (FFR = 0.83) (Figure 3), suggesting sufficient remaining (competitive) flow in the native LAD. A stent was implanted in the right IMA-RCA anastomosis, after which the patient's symptoms improved.
Case 3
A 61-year-old man after an inferior myocardial infarction underwent surgical revascularization involving a LIMA graft on the LAD and a venous graft on the aberrant left circumflex artery (LCx) from the right Valsalva sinus. One year later, the repeated coronary angiography detected string sign of the LIMA graft (Figure 4.) and total occlusion of the venous graft. Despite the 57% diameter stenosis of the LAD lesion (Figure 5.), pressure wire measurement excluded a hemodynamically significant lesion in this coronary artery. The aberrant LCx lesion was treated percutaneously by stent implantation.
Case 4
Five years after the bypass operation (LIMA-LAD, SVGA-1st obtuse marginal branch (OM), -RCA), a 65-year-male patient was recatheterized because of the recurrence of angina-like symptoms. The venous grafts were occluded, while the LIMA graft was widely patent, with an intermediate lesion in the run-off under the anastomosis of the LIMA. A total arterial revascularization redo operation was decided on, and radial grafts were applied on the LAD, OM and RCA. After 3 years repeated coronary angiography revealed the string sign of the previously patent LIMA graft because the competitive flow of the new radial graft supplied the LAD more intensively than the previous LIMA graft (Figure 6).
Case 5
Three years after the bypass surgery (LIMA-LAD, SVGA-1st diagonal, -1st OM and -RCA), a 75-year-old man underwent recatheterization because of angina-like symptoms. Coronary angiography showed the string sign of the LIMA graft, while the venous grafts were patent (Figure 7). The originally severe lesion demonstrated such a degree of regression that the flow in the LAD improved to a normal level, resulting in competition of the LIMA graft.
Case 6
A 56-year-old male patient had presented with unstable angina 3 years previously. Angiography revealed three-vessel disease with occlusion of the RCA and the LCx. In the middle region of the LAD, there was a tight lesion, and the orifice of the diagonal branch exhibited a mild lesion. The patient underwent bypass grafting: the LCx and the RCA received radial artery grafts, while the diagonal branch and the LAD were sequentially grafted by the LIMA. The patient made a good recovery from surgery, and was free of symptoms for more than 2 years. The index admission of the patient was necessary because of recurrence of the angina. The repeated angiography demonstrated patent radial grafts to the RCA and the LCx, but the LIMA graft was occluded proximally and did not fill the diagonal branch. Only the short distal part of the LIMA graft was open, connecting the proximal part of the LAD to the distal segment through the diagonal branch (Figure 8). It was decided to perform an intervention on the LAD lesion with stent implantation in order to improve the flow in the distal LAD.