Intraoperative graft patency verification in coronary artery surgery: modern diagnostic tools

Assessment of the Graft Quality and Patency during and after Coronary Artery Bypass Grafting

Coronary artery bypass grafting (CABG) is the gold standard procedure for multi vessels and left main coronary artery disease. The prognosis and survival outcomes of CABG surgery are highly dependent on the patency of the bypass graft. Early graft failure which can occur during or soon after CABG remains a significant issue, with reported incidences of 3-10%. Graft failure can lead to refractory angina, myocardial ischemia, arrhythmias, low cardiac output, and fatal cardiac failure, emphasizing the importance of ensuring graft patency during and after surgery to prevent such complications. Technical errors during anastomosis are among the leading causes of early graft failure. To address this issue, various modalities and techniques have been developed to evaluate graft patency during and after CABG surgery. These modalities aim to assess the quality and integrity of the graft, thus enabling surgeons to identify and address any issues before they lead to significant complications. In this review article, we aim to discuss the strengths and limitations of all available techniques and modalities, with the goal to identify the best modality for evaluating graft patency during and after CABG surgery.

The impact of the quantitative assessment procedure for coronary artery bypass graft evaluations using high-resolution near-infrared fluorescence angiography

PURPOSE

Near-infrared angiography (NIR) is used for on-site graft assessment during coronary artery bypass grafting. This study evaluated the results of a quantitative NIR assessment using a new high-resolution NIR device (h-NIR) for graft assessment.

METHODS

Forty-three patients were enrolled in our study. Internal thoracic artery (ITA) grafts anastomosed to the left anterior descending artery and examined intraoperatively using h-NIR were included. The ITA grafts were divided into 2 groups for a comparative analysis: patent grafts (P group; n = 37) and failed grafts (F group; n = 6). The graft flow was evaluated by a "quantitative NIR assessment", and the fluorescence luminance intensity (FLI) was measured. Direct observation of the graft and anastomosis with h-NIR was also performed.

RESULTS

The FLI was higher in the P group than in the F group. The receiver operating characteristic analysis revealed the following cut-off values for FLIs depending on imaging duration: 21.1% at 1 s, 35.5% at 2 s, 58.4% at 3 s, and 83.3% at 4 s. The sensitivity and specificity for detecting graft failure were 83.3% and 69.8-80.6%, respectively. Furthermore, h-NIR was also able to visualize arterial dissection in ITA grafts.

CONCLUSIONS

A quantitative NIR assessment with an h-NIR device can improve the detectability of anastomotic stenosis, and h-NIR successfully detected arterial dissection of grafts.

Transesophageal Echocardiographic Estimation of Coronary Sinus Blood Flow for Predicting Favorable Postoperative Transit Time Coronary Graft Flow Measurements: A Pilot Study

BACKGROUND

Augmentation of coronary artery flow by surgical grafting increases coronary sinus blood flow (CSBF), which can be quantified on transesophageal echocardiography (TEE). However, transit time flowmetry (TTF) technology remains the most used intraoperative technique for coronary artery graft assessment. The purpose of the present pilot study was to evaluate the predictive value of TEE-based CSBF estimation for identifying favorable TTF graft measurements.

DESIGN

Prospective observational study.

SETTING

Single university hospital.

PATIENTS

Forty patients undergoing triple vessel coronary artery bypass grafting.

MEASUREMENTS AND MAIN RESULTS

CSBF was assessed on TEE examination before and after revascularization, estimating the percentage increase in CSBF (∆CSBF). Postoperative TTF graft measurements were averaged to compute mean diastolic filling (DF) and pulsatility index (PI). Subjects were grouped based on favorable (PI ≤ 3, DF ≥ 50%) and unfavorable (PI > 3, DF < 50%) parameters. The group with PI ≤ 3 (n = 32) had significantly higher ∆CSBF compared with the group with PI > 3 (n = 8) (38.22% ± 12.05%, 13.75% ± 3.37%, p < 0.001). ∆CSBF was higher in the DF ≥ 50% group (n = 35) (36.40 ± 12.99) in contrast to DF < 50% group (n = 5) (11.80 ± 2.59%). A strong negative and significantly positive correlation was observed between ∆CSBF with PI, DF (r = -0.903, 0.571, respectively, p < 0.001). A ∆CSBF ≥15.5% was found to predict a mean PI ≤ 3 and DF ≥ 50% with sensitivity and specificity of 100% and 62.5% for PI and 100% and 100% for DF. A ∆CSBF ≥19% demonstrated a sensitivity and specificity of 100% and 100%, 100% and 91.4% for prediction of PI ≤ 3 and DF ≥ 50%, respectively.

CONCLUSION

TEE-based demonstration of an augmented CSBF can ensure favorable TTF graft parameters, guiding the adequacy of surgical revascularization.

Evaluation of graft anastomosis using time-intensity curves and quantitative near-infrared fluorescence angiography during peripheral arterial bypass grafting

Near-infrared fluorescence angiography (NIR) visualizes blood perfusion using the fluorescence property of indocyanine green (ICG). This study aimed to retrospectively determine the usefulness of a quantitative analysis using NIR to predict the patency of peripheral arterial bypass grafts by measuring their fluorescence luminance intensities (FLIs).Thirteen grafts in 11 patients who underwent peripheral arterial bypass grafting were divided into a patent graft group (n = 7) and a failed graft group (n = 6). The changes in the FLIs of ICG opacification through the graft and distal host artery were retrospectively analyzed using stored NIR data. The time-intensity curves (TICs) of ICG opacification through the graft (Q_graft) and distal host artery (Q_distal) were measured. Two parameters, Δ(Q_graft - Q_distal) and integral(Q_graft - Q_distal), were also analyzed.Although not significant, decreases in Q_graft were observed in the failed graft groups. The Q_distal of the failed graft group was significantly attenuated as compared with that of the patent graft group. Δ(Q_graft - Q_distal) increased only in the failed graft group, which indicates widening of the gap in FLI. Integral(Q_graft - Q_distal) was higher in the failed graft group, as it reflects the accumulation of ICG opacification.The TICs were influenced by anastomotic stenosis in the distal site of the host arteries. Our results indicate that the comparison of Δ(Q_graft - Q_distal) and integral (Q_graft - Q_distal) quantitatively analyzed using NIR can potentially predict anastomotic stenosis.

A Case of Anastomotic Stenosis of a Peripheral Arterial Bypass Graft Undetected in Indocyanine Green Angiography

We report the case of a 75-year-old man who underwent right femoral-popliteal bypass surgery. Anastomotic stenosis was overlooked in indocyanine green (ICG) angiography due to opacification on the bypass graft. X-ray angiography revealed slit-shaped stenosis in the distal graft anastomosis that required revision. Although blood flow may be maintained despite of anastomotic stenosis, small decreases in blood flow cannot be detected in ICG angiography. We describe and discuss the pitfalls of qualitative graft assessment using ICG angiography, and compare ICG fluorescence luminance intensity between primary and revised grafts.

Influence of coronary territory on flow profiles of saphenous vein grafts

Background

Differing perfusion of the left and right ventricular coronary territory may influence flow-profiles of saphenous vein grafts (SVGs). We compared flow parameters, measured by transit-time flowmetry (TTFM), in left- and right-sided SVGs during coronary artery by-pass grafting (CABG).

Methods

Routine TTFM measurements were obtained in 167 SVGs to the left territory (55%) and 134 SVGs to the right territory (total of 301 SVGs in 207 patients). The four standard TTFM parameters, [mean graft flow (MGF), pulsatility index (PI), percentage diastolic filling (%DF), and percentage backward flow (%BF)] were compared. Differences in flow parameters were also examined according to surgical technique (on- vs. off-pump).

Results

No significant difference between coronary territories was found for MGF, PI and %BF. However, a higher %DF was noted in left-sided SVGs in the overall cohort as well as in the on-pump (both p < 0.001) and the off-pump cohorts (p = 0.07). Further, a significantly higher %BF was found in SVGs performed off-pump to the left territory (1.2 ± 2.5 vs. 2.3 ± 3.0, p = 0.023). In a multivariate regression analysis, anastomosing a SVG to the left territory was weakly associated with higher PI (OR = 0.36, p = 0.026) and strongly associated with higher %DF (OR = 5.1, p < 0.001). No significant association was found for MGF, PI, %DF or %BF in either the on-pump nor the off-pump cohorts.

Conclusions

Although statistically significant, the established differences in TTFM parameters between left- and right-sided vein grafts were small and unlikely to be of clinical relevance.

Does Diabetes Have an Influence on Regional Deformation Parameters in Patients with Normal Systolic Function during Off-Pump Coronary Artery Bypass Grafting?

OBJECTIVES

The aim of this study was to assess the recovery of regional myocardial function of the left-ventricular septal wall and the septal site of the mitral valve (MV) annulus by tissue Doppler imaging (TDI).

METHODS

In 63 (32 diabetic and 31 control) patients having off-pump coronary artery bypass grafting (OPCABG), including the left internal mammary artery (LIMA) and the left anterior descending coronary artery (LAD), TDI measurements were performed before operation (baseline), 5 min after LIMA-LAD revascularization (early reperfusion) and after completion of all anastomoses (after revascularization).

RESULTS

Compared to the patients with diabetes, the controls had higher peak systolic velocities of the mid septal segments in the early reperfusion measurement (p = 0.002). After revascularization, values of peak systolic strain at the basal (-10.13 vs. -13.36%, p = 0.044) and mid septal segments (-8.25 vs. -12.69%, p = 0.009) were decreased in the diabetic patients compared to the controls. There was no difference between the groups with respect to the velocities acquired at the septal site of the MV annulus.

CONCLUSIONS

This study demonstrates an insufficient recovery of regional myocardial function in patients with type II diabetes undergoing OPCABG.

Intraoperative graft assessment during coronary artery bypass surgery

Coronary artery bypass grafting (CABG) is an established revascularization method for treating multivessel coronary artery disease. The goal of CABG is to achieve complete revascularization with a durable, patent graft without reintervention. However, early graft failure, including that associated with technical errors, has been reported. This makes intraoperative verification of graft patency one of the most important ways in which surgeons can reduce the rate of early graft failure. Conventional angiography is considered the gold standard for graft assessment. However, because it is invasive and inconvenient, several alternatives to intraoperative graft assessment have become available that help reduce early graft failure by allowing revision of the anastomosis intraoperatively. The aim of this article is to review the advantages and disadvantages of several intraoperative graft assessment methods for CABG.

Assessing intraoperative blood flow in cardiovascular surgery

Off-pump coronary arterial bypass grafting and new surgical apparatus and techniques have decreased the mortality rate associated with this procedure to approximately 1.5%. If we could detect problems in the constructed coronary anastomoses by an alternative imaging system to coronary angiography during surgery, decisions to revise the surgical procedure could be made without hesitation. Meanwhile, the intraoperative direct evaluation of intestinal blood flow during abdominal aortic aneurysmal surgery is required to prevent ischemic colitis, which is a devastating complication. Indocyanine green (ICG) has recently improved ophthalmic angiography and the navigation systems of oncological surgery. The fluorescence illumination of ICG with a near-infrared light is captured on camera. In coronary arterial surgery, the ICG imaging system is also becoming increasingly useful. A new ICG imaging system, the HyperEye Medical System (HEMS), provides a clear view of the blood flow and ischemic area with color visualization. Furthermore, its combination with a quantitative blood flow assessment tool such as transit time flow measurement could improve the accuracy of intraoperative examination. In this review, we evaluate the current strategies of assessing blood flow intraoperatively with an ICG imaging system in cardiovascular surgery.