Epicardial 10-MHz ultrasound in off-pump coronary bypass surgery: a clinical feasibility study using a minitransducer

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.

A Laser-Assisted Anastomotic Technique: Feasibility on Human Diseased Coronary Arteries

OBJECTIVE

Atherosclerotic disease might hamper the efficacy of the Excimer laser-assisted Trinity Clip anastomotic connector in coronary arteries. Therefore, its efficacy was evaluated on human diseased coronary arteries (study 1). In addition, the acute laser effects onto the coronary wall were assessed (study 2).

METHODS

Thirty-eight anastomoses were constructed on ex vivo human hearts. Atherosclerosis was histopathologically determined and subsequently related to the success of the technique (ie, connector positioning and laser punching; study 1). In addition, 20 anastomoses were constructed in an ex vivo (porcine, n = 8) and an in vivo [rabbit (n = 9) and porcine (n = 3)] model. Subsequently, the coronary was histologically studied on the presence of laser-induced damage (study 2).

RESULTS

In 13 of 38 anastomoses (study 1), the connector was malpositioned, 3 because of a severely diseased coronary wall and 10 because of an inner diameter less than the intended target range. The laser-punch success rates on coronary arteries with an early and advanced lesion were 100% (16/16) and 89% (8/9; lesions were located in the inferolateral wall), respectively. In one case, an advanced lesion (ie, fibrocalcified plaque) was located in the superolateral wall and caused a laser-punch failure. No histological signs of laser-induced damage were observed, in case of correct use (study 2).

CONCLUSIONS

This study demonstrates the feasibility of an anastomotic connector on human diseased coronary arteries and shows that lasering does not induce coronary wall damage. However, careful selection of the coronary, regarding the target inner diameter and disease status, will prevent construction failures. This connector could facilitate less invasive coronary artery bypass grafting.

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.

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.

Target Vessel Detection and Coronary Anastomosis Assessment by Intraoperative 12-MHz Ultrasound

PURPOSE

Our aim was to assess whether the left internal mammary artery, left anterior descending artery, and anastomosis could be visualized by intraoperative ultrasound for safe graft harvesting, optimal anastomotic target selection, and quality control.

DESCRIPTION

In 10 patients, the left internal mammary artery, the left anterior descending artery, and the constructed anastomosis were scanned with 12-MHz epicardial ultrasound. Anastomosis quality was assessed on ultrasound and compared with surgeon score.

EVALUATION

All left internal mammary arteries and left anterior descending arteries could be identified, and pathways could be followed on the ultrasound. Plaque and calcifications were detectable. Deviation from initial coronary anastomotic target was necessary in 2 of 10 patients. None of the constructed anastomoses needed revision. On the anastomotic scans, six anastomoses scored satisfactory and four scored good.

CONCLUSIONS

Epicardial ultrasound was able to evaluate vessel characteristics and coronary anastomosis patency. This can lead to correction of surgical technique related problems in the operating room, possibly improving graft patency. Further advancements could make epicardial ultrasound a cost effective standard for anastomotic quality control. Applying it during robotic-assisted bypass surgery could make this procedure appropriate for more patients.

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.

Detection of construction errors in ex vivo coronary artery anastomoses by 13-MHz epicardial ultrasonography

OBJECTIVE

Intraoperative detection of suboptimal coronary anastomoses allows revision before chest closure. We evaluated an epicardial 13-MHz ultrasound minitransducer as a means to detect three different coronary anastomosis construction errors.

METHODS

In total, 120 internal thoracic artery-to-coronary artery anastomoses were constructed correctly (n = 60) or incorrectly (n = 60) with one technical error: suture crossover, purse-string or deep toe stitch (n = 20 each). Anastomoses were performed on ex vivo pressure-perfused porcine (96 anastomoses) and human hearts (24 anastomoses). Two blinded observers scanned and scored the anastomoses with epicardial ultrasonography. In 24 human and 24 porcine anastomoses, angiograms were made of 24 correct and 24 incorrect anastomoses and scored by two other blinded observers. Angioscopy and cast injection served as a reference.

RESULTS

Overall, 119 of 120 anastomoses were accurately scored as correct or incorrect within a median of 67 seconds (8-381 seconds) by both observers (sensitivity 0.98, specificity 1.00, kappa 1.00 (1.00, 1.00, and 1.00 in angiography subset, respectively). One deep toe stitch that induced outflow corner stenosis was spotted by both observers but regarded as insignificant and thus inaccurately scored as correct. In 5 anastomoses, unintended irregularities were detected. By angiography, anastomoses were accurately scored with a sensitivity of 0.75 and a specificity of 0.81 ( P < .001 vs ultrasonography) and kappa of 0.54. Angioscopy and cast confirmed ultrasonographic findings and did not reveal irregularities other than detected by ultrasonography.

CONCLUSION

Ex vivo epicardial 13-MHz ultrasonography allowed rapid and accurate evaluation of coronary anastomoses and detected technical construction errors with higher sensitivity and specificity than angiography.

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.