Intraoperative echocardiographic imaging of coronary arteries and graft anastomoses during coronary artery bypass grafting without cardiopulmonary bypass

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.

An Experimental Study of the Effects of IABP on Coronary Artery Bypass Graft Flow Waveform

Purpose: Graft evaluation after coronary artery bypass grafting (CABG) is still not sufficient. This study analyzed the flow waveform of coronary arteries and grafts during intra-aortic balloon pumping (IABP) assist.

Methods: Subjects were eight pigs that underwent off-pump CABG. Using transit-time flow measurement (TTFM) and occluder, blood flow waveforms were recorded while changing the degree of stenosis of Seg.6 and the left internal thoracic artery (LITA) and analyzed by percentage of reverse flow component to the total blood flow (R/T) and the ratio of diastolic blood flow of IABP operative and IABP inoperative (D1/D0).

Result: Reverse flow of the LITA was reduced when stenosis of Seg.6 increased and R/T decreased. The average diastolic blood flow of Seg.8 and the LITA increased with IABP on showing a D1/D0 of 1 or more. R/T of the LITA increased when stenosis of Seg.6 was fixed and increasing the degree of LITA stenosis. D1/D0 increased up to a 75% LITA stenosis and is decreased in more severe stenosis.

Conclusion: R/T is significantly higher in the antagonist or stenosis during IABP assist and was able to confirm the effectiveness of the graft as a functional assessment of graft. D1/D0 is useful as an indicator of the effectiveness of IABP on coronary blood flow.

Avoiding coronary injury in congenital heart surgery by laser-assisted indocyanine green dye imaging

Many patients with congenital heart disease require a staged surgical approach to achieve optimum circulation. During repeat operations, coronary anatomy can be difficult to ascertain because of epicardial scarring or underlying anomalous coronary anatomy. Uncertainty about coronary artery location increases the risk of reoperation. Having real-time data of coronary anatomy improves intraoperative decision making and enhances patient safety. We describe four patients undergoing reoperation with the aid of laser-assisted indocyanine green dye imaging to provide real-time data about coronary artery anatomy intraoperatively, thus helping the surgeon to prevent coronary artery injury.

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.

The role of intraoperative indocyanine green fluorescence angiography in pediatric cardiac surgery

PURPOSE

In surgical reconstructions for congenital heart defects, vessel and anastomotic site patency is critical to success. Indocyanine green fluorescence angiography offers potential for a reliable and rapid method of intraoperative assessment. We sought to determine its feasibility in congenital heart surgery.

DESCRIPTION

Patients undergoing the following repairs were eligible for imaging: (1) coronary artery reimplantation, (2) coarctation, (3) palliative shunts, and (4) pulmonary artery reconstruction.

EVALUATION

Adequate postoperative images were obtained in 18 of 30 (60%) patients. Image adequacy was highest for Blalock-Taussig shunts (100%), coarctation repairs (86%), coronary reimplantations (66%), lowest for the hemi-Fontan (0%), Fontan (40%), and pulmonary artery reconstructions (33%). All adequate images showed vessel or anastomotic site patency, which corresponded to the subsequent postoperative echocardiograms and cineangiograms. There were no adverse events or mortalities.

CONCLUSIONS

Indocyanine green fluorescence imaging may provide an additional intraoperative imaging modality. Ultimately, the surgical procedure may be assessed and revised, if necessary, prior to leaving the operating room. This potentially will reduce the need for subsequent postoperative interventions, along with their associated morbidity and mortality.

Detection of coronary arteries and evaluation of anastomoses with a commercially available 15-MHz, broadband, linear array transducer

BACKGROUND

In coronary artery bypass surgery the detection of the target vessels can be difficult due to their intramural location, coverage by adipose tissue, calcification, or fibrous tissue formation. Their identification is especially critical during off-pump coronary artery bypass (OPCAB) and minimally invasive direct coronary artery bypass (MIDCAB) surgeries. Our objectives were to identify whether (1) the epimyocardial use of the broadband linear array transducer CL15-7 allows a clear and rapid identification of the target artery during on-pump coronary bypass (CPB), OPCAB and MIDCAB surgeries; and (2) if this transducer is helpful in investigating the anastomotic morphology with 2D and color flow Doppler.

METHODS

Thirty-two patients without a visually identifiable left anterior descending artery (LAD) were included in the study and epimyocardial ultrasonography was performed. Stabilization of the beating heart was used in 19 patients; in 13 patients, the surgery was carried out with CPB on the arrested heart. Two-dimensional ultrasound alone, or in combination with color Doppler, was used to identify the affected vessel as well as a suitable anastomosis site. Pulsed wave Doppler had to be used occasionally to differentiate between artery and vein. Patency of the anastomoses was established with color Doppler immediately after reinitiating blood flow. An evaluation of the distal graft diameter, its length, and the quality of the anastomosis was made with 2D and color Doppler. Transit-time Doppler flow was used to confirm patency.

RESULTS

The LAD could be identified ultrasonographically in all 32 patients at a depth of 3 to 15 mm. The right coronary artery (RCA) was located at a depth of 3 to 10 mm in the 5 patients where this vessel was to be bypassed. The coronary arteries located on the lateral or posterior aspect of the heart could not be reached due to the shape and rigidity of the transducer handle. The intended anastomosis sites of the LAD and RCA were identified with ultrasound according to their topography and morphology. In all cases the vessel could be dissected and bypassed without undue damage or bleeding. In one OPCAB patient, the LAD was identified in close proximity to the overlying vein along the whole of the anterior wall. This resulted in conversion to CPB, thus facilitating secure exposure of the LAD. The ultrasonographic visibility of the left internal mammary artery to LAD and saphenous vein graft to RCA anastomoses was excellent, and patency correlated well with the transit time flow measurements.

CONCLUSION

The CL15-7 transducer gives excellent near field visibility of the LAD and RCA. This is extremely valuable for the safe dissection of these vessels, especially during off-pump coronary surgery. The anatomical morphology of the anastomoses can be identified but, due to the shape of the transducer handle, only the coronary arteries on the anterior surface of the heart can be evaluated. A flexible, rather than a rigid, hockey stick-shaped handle would eliminate this problem. Training is essential to obtain reliable results.

Epicardial Ultrasonography: A Potential Method for Intraoperative Quality Assessment of Coronary Bypass Anastomoses?

BACKGROUND

Intraoperative quality assessment in coronary artery bypass surgery confirms graft patency and enables revision of failing grafts. The aim of this study was to evaluate graft quality intraoperatively by epicardial ultrasonography and to compare this technique with transit time flow measurements and intraoperative angiography, and to evaluate the ability of these methods to predict long-term patency as described by follow-up angiography.

METHODS

Thirty-nine patients with mean age of 66 years (SD 9.5) who underwent off-pump coronary artery bypass surgery with internal mammary artery graft to the left anterior descending coronary artery were included. Epicardial ultrasonography and transit time flow measurement were performed after completion of the anastomoses, and coronary angiography after closure of the chest. Follow-up angiography was carried out after 156 days (SD 50).

RESULTS

Diameter measurements obtained by epicardial ultrasonography correlated poorly with the same diameter measurements obtained by angiography. Epicardial ultrasonography revealed 5 abnormal grafts (13%), transit time flow measurements none, and intraoperative angiography 9 (23%). At follow-up angiography, 4 grafts (11%) were pathologic. Epicardial ultrasonography and transit time flow measurements indicated no need for graft revision; intraoperative angiography suggested need for revision in 3 cases.

CONCLUSIONS

Epicardial ultrasonography could be a useful method for intraoperative assessment of graft anastomosis quality, but needs to demonstrate its ability to predict grafts in need of revision. Angiography must be considered the gold standard in intraoperative imaging.

Ultrasound Mini-Transducer with Malleable Handle for Coronary Artery Surgery

PURPOSE

A 13 MHz epicardial ultrasound mini-transducer (15 x 9 x 6 mm) with a custom made malleable handling tool was evaluated to assess the coronary artery and anastomosis on all sides of the heart.

DESCRIPTION

On indication, in 8 patients undergoing coronary artery bypass surgery on the arrested heart, 8 coronary arteries as well as 27 coronary anastomoses were scanned.

EVALUATION

The malleable handle was easily adjusted, and all sides of the heart were accessible for scanning with the mini-transducer. Based on intraoperative scanning, the anastomotic site was altered (n = 4), an additional coronary artery was grafted (n = 2), and the left anterior descending coronary artery was identified after incorrect conventional selection of the diagonal branch (n = 1). No anastomosis construction errors were detected. In one anastomosis, a calcified plaque was seen in the outflow corner.

CONCLUSIONS

The epicardial ultrasound mini-transducer with its malleable handle allowed successful visualization and assessment of the coronary arteries and anastomoses on all sides of the heart. Ultrasound information greatly aided in intraoperative decision making that resulted in anastomotic site changes and prevented grafting of the wrong vessel.

Endoscopic localization and assessment of coronary arteries by 13 MHz epicardial ultrasound

BACKGROUND

In totally endoscopic coronary artery bypass grafting the target coronary artery is difficult to locate and assess. We explored the capacity of a high-frequency epicardial ultrasound mini-transducer (Aloka, Tokyo, Japan) to endoscopically locate and assess the left anterior descending (LAD), third obtuse marginal (OM3), and right posterior descending (RDP) coronary arteries.

METHODS

In eight pigs, the LAD, OM3, and RDP were endoscopically exposed. The mini-transducer was manipulated by the "da Vinci" telemanipulation system (Intuitive Surgical, Inc, Mountain View, CA) over the unstabilized and stabilized epicardium to identify the target artery, obtain a scout scan, and both transverse and longitudinal images.

RESULTS

In both unstabilized and stabilized conditions, the LAD and RDP were identified within a median of 29 seconds. In stabilized conditions, assessment was complete in 112 seconds (92 to 205) (median with range) for the LAD and 140 seconds (54 to 197) for the RDP. Stabilization of the OM3 was required for identification (16 [5 to 60]) and assessment (111 [82 to 225]). Overall identification was correct in 23 of 24 arteries. The OM branches and RDP became fully exposed endoscopically with stroke volume (SV) and mean arterial pressure (MAP) remaining at 67% +/- 11% (mean +/- standard error of the mean) and 70% +/- 5% of baseline values, respectively. Scanning itself did not augment the decrease in SV and MAP significantly.

CONCLUSIONS

After proper endoscopic exposure and stabilization, robot-assisted epicardial ultrasound scanning enabled endoscopic identification and assessment of major coronary arteries within a median of 169 seconds per artery. Exposure, stabilization, and scanning were accompanied by an acceptable drop in stroke volume and mean arterial pressure.

Preliminary experience with a novel intraoperative fluorescence imaging technique to evaluate the patency of bypass grafts in total arterial revascularization

BACKGROUND

Early graft failure is a common cause of cardiac morbidity and mortality after coronary artery bypass grafting (CABG), and there is particular concern about graft patency in off-pump CABG. We describe our preliminary experience with a novel imaging technique (the SPY system), based on fluorescence of Indocyanine Green when exposed to near infrared light, for the intraoperative assessment of coronary graft patency.

METHODS

Graft patency was assessed in patients undergoing off-pump and on-pump total arterial revascularization. The imaging technique requires injection of a 1-mL bolus of Indocyanine Green into the central venous line, followed by imaging with the SPY system.

RESULTS

We assessed intraoperative graft patency in 213 conduits in 84 patients (mean, 2.54 grafts per patient), of which, 65 (77%) were done off-pump. It took approximately 3 minutes to image each graft. Skeletonized conduits provided better visualization than pedicled ones. Fluorescence, confirming graft patency, was observed in all but four (1.9%) conduits in 4 (5%) patients. In these latter cases, graft revision was necessitated.

CONCLUSIONS

Fluorescence imaging of coronary grafts using the SPY is a uniquely simple, safe, noninvasive, and reproducible technique for intraoperative confirmation of graft patency. In 4 patients, it necessitated revision of the initial intraoperative procedure. Quantification of graft flow would enhance the value of the system.

Ultrasonic evaluation of graft anastomoses during coronary artery bypass grafting without cardiopulmonary bypass

Performance of the graft-to-coronary anastomosis in coronary artery bypass grafting without cardiopulmonary bypass is more difficult than conventional coronary artery bypass grafting. We report a new method that uses high-frequency epicardial echocardiography to detect technical errors and inadequacies in graft anastomoses. This method improves the operative outcome and enables detection of septal perforator branches and deeply embedded coronary arteries during coronary artery bypass grafting without cardiopulmonary bypass.

Power Doppler imaging for detection of harvest injury of internal mammary artery

Harvest injury of the internal mammary artery can lead to early thrombosis, which may be difficult to differentiate from atherosclerosis or harvest spasm in some cases. We describe the efficacy of intraoperative evaluation of the internal mammary artery by power Doppler imaging during off-pump or minimally invasive direct coronary artery bypass grafting.