**5. Application of ICG angiography in CABG**

Since the first report of intraoperative ICG coronary angiography by Rubens et al. and Detter et al. in 2002, usefulness of this modality have been reported by several investigators (Table 1) [5, 12, 16, 17, 20-22]. Reuthebuch and Taggart showed the clinical utility of the SPY system for assessment of the quality of bypass grafts of usage from experience [20, 21]. Takahashi et.al. described the verification of ICG angiography with using the SPY imaging system [16].

TTF (MediStim AS, Oslo, Norway) has been used as well in CABG for intraoperative assess‐ mentofcoronarygraft[23].Thetimeforultrasoundbeamtotravelfromonecrystalacrossavessel to another crystal is called as transit time. In TTF, the graft flow is assessed by three parameters: meangraftflow,pulsatilityindex,anddiastolicfillingpercentage.Desaietal.researchedtheutility of two intraoperative assessments of graft, TTF and ICG graft angiography [24]. A total of 139 graftswerereviewedandthesensitivityandspecificityofICGangiographytodetectgreaterthan 50% stenosis or occlusion were 83.3% and 100%, respectively. When TTF shows an unusual data, however, imaging modality may be helpful for making treatment strategy.



Reprinted from Surgery Today, 2011; 41:1467-1474, Yamamoto M et. al. Assessing Intraoperative Blood Flow in Cardiovascular Surgery., copyright (2011)

**Table 1.** Reported clinical studies on the indocyanine green imaging system in coronary artery bypass grafting

We have assessed coronary grafts by means of HEMS since 2007 and have classified the flow pattern as follows [12].


**Figure 5.** HEMS in use during cardiac surgery. A: The imaging head is draped by a sterile cover and placed at 30 to 50

Since the first report of intraoperative ICG coronary angiography by Rubens et al. and Detter et al. in 2002, usefulness of this modality have been reported by several investigators (Table 1) [5, 12, 16, 17, 20-22]. Reuthebuch and Taggart showed the clinical utility of the SPY system for assessment of the quality of bypass grafts of usage from experience [20, 21]. Takahashi et.al. described the verification of ICG angiography with using the SPY imaging system [16].

TTF (MediStim AS, Oslo, Norway) has been used as well in CABG for intraoperative assess‐ mentofcoronarygraft[23].Thetimeforultrasoundbeamtotravelfromonecrystalacrossavessel to another crystal is called as transit time. In TTF, the graft flow is assessed by three parameters: meangraftflow,pulsatilityindex,anddiastolicfillingpercentage.Desaietal.researchedtheutility of two intraoperative assessments of graft, TTF and ICG graft angiography [24]. A total of 139 graftswerereviewedandthesensitivityandspecificityofICGangiographytodetectgreaterthan 50% stenosis or occlusion were 83.3% and 100%, respectively. When TTF shows an unusual data,

however, imaging modality may be helpful for making treatment strategy.

cm above the targets. B: ICG solution is injected via a central venous catheter.

86 Artery Bypass

**5. Application of ICG angiography in CABG**

Delay: delayed graft enhancement compared to other grafts (Fig 6B)

Occlusion: no enhancement of the graft (Fig 6C)

The results of HEMS assessment were compared with fluoroscopic CAG one year after CABG and have found that the former accurately predicted the outcomes of grafts (Figure.6D-F). [12]. Thus, visualization of graft flow is helpful for surgeons to make decisions of revision in the operating room.

Visualization of myocardial perfusion is another feature of HEMS. Figure 6C shows an obstructed anastomosis in the left internal thoracic arterial graft, causing perfusion defect in the anterior wall around the anastomosis, whereas myocardium in the diagonal region is well opacified. Detter et. al. reported that myocardial perfusion can be quantitatively assessed by ICG angiography with digital image processing system [25].

**Figure 6.** HEMS assessment of coronary arterial grafts. Coronary arterial bypass grafts images created by HEMS (A-C) and fluoroscopic angiography (D-F). Arrows indicate coronary anastomoses, arrow heads indicate occluded point of graft. A: Smooth opacification of graft and distal coronary artery. B: Delayed graft flow. C: Absence of fluorescence in the left anterior descending artery (LAD) despite of opacification of left internal thoracic artery (LITA) graft. There was perfusion defect in the anterior myocardial wall (circled dot line), while myocardial perfusion in the diagonal region is apparent. D-F: Fluoroscopic coronary angiography corresponding to A to C, respectively.

**Figure 7.** HEMS assessment of graft in peripheral arterial surgery. Visual image and ICG angiogram in ePTFE graft (A,B) and saphenous vein graft (C, D). Opacification is poor in PTFE graft. PTFE: polytetrafluoroethylene. SV: saphenous vein.

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Figure 8 compares the intraoperative HEMS image and postoperative CT angiogram in a case of arterial revascularization. The blood flow through the anastomosis was smooth (Figure 8A) and there was no stenosis at the anastomosis by CTA (Figure 8B). Figure 9 demonstrates the data of a case who underwent bypass grafting to the posterior peroneal artery (PTA) with a saphenous vein graft [19]. HEMS revealed an inadequate blood flow in the PTA distal to the anastomosis (Figure 9A), although TTF showed fairly acceptable graft flow (7 mL/min of mean flow: Figure 9B). Based on the HEMS findings, an additional bypass to the PTA was placed with a saphenous vein graft. HEMS following additional grafting showed smooth flow in the graft as well as in the PTA distal to the anastomosis (Figure 9C). The TTF assessment showed doubled graft flow (15 mL/min, Figure 9D). Since the TTF data can be largely affected by hemodynamic condition as well as peripheral perfusion area, it is not easy to make reliable

TTF criteria. HEMS may be helpful for making a decision in such instances.

Arrow heads show native peripheral arteries.
