A technique for evaluating competitive flow for intraoperative decision making in coronary artery surgery

Intraoperative transit time flow measurements during off-pump coronary artery bypass surgery: The impact of coronary stenosis on competitive flow

Background

Combining preoperative angiography findings with intraoperative transit time flow measurements (TTFM) may improve patency of coronary artery bypass grafts. Nevertheless, graft flow might be impaired by native coronary flow based on the severity of stenoses, with inferior long‐term outcomes. This study investigates the impact of left anterior descending artery (LAD) stenosis on competitive flow measured in left internal mammary artery (LIMA) grafts during off‐pump coronary artery bypass grafting.

Methods

Fifty patients were included in this prospective single‐center cohort study. LAD stenosis was assessed with quantitative coronary analysis (QCA) and stratified into three groups based on its severity. TTFM of LIMA grafts were performed with LAD open and temporarily occluded. Change in mean graft flow after LAD snaring was the primary endpoint. Secondary endpoints included further TTFM parameters, clinical outcomes, and competitive flow index (CFI), defined as the ratio of mean graft flow with open or closed LAD.

Results

Mean LAD stenosis as objectified with QCA was 58 ± 15%. Mean LIMA graft flow increased from 20 ml/min with open LAD to 30 ml/min with snared LAD (p < .001). TTFM cut‐off values for graft patency improved in 26%–42% of patients after LAD occlusion. Median CFI was 0.66 (IQR: 0.56–0.82). Postoperative myocardial infarction occurred in 2.0% of patients, 120‐day mortality was 0%, and 2‐year mortality was 6.0%.

Conclusions

Routine snaring of the LAD with CFI calculation during coronary artery bypass grafting is useful to detect significant competitive flow in LIMA grafts, potentially preventing unnecessary intraoperative graft revisions.

Competitive Coronary Flow between the Native Left Anterior Descending Artery and Left Internal Mammary Artery Graft: Is It a Surrogate Angiographic Marker of Over-or-Unnecessary Revascularization Decision in Daily Practice?

Overdiagnosis and overtreatment are often thought of as relatively recent phenomena in modern medicine, influenced by a contemporary combination of technology, specialization, payment models, marketing, and supply-related demand. Several investigators have reported discrepancies between the angiographic and functional severity of coronary angiographic stenosis. However, the visual anatomic assessment of the coronary lesion severity continues in daily practice. We evaluated the consecutive all coronary angiograms performed between January 2015 and December 2015 and examined only patients who had previous coronary artery bypass grafting (CABG) to analyze the cases with regard to presence of the competitive flow (CF) between the native left anterior descending coronary artery (LAD) and left internal mammary artery (LIMA) graft. A total of 8,248 diagnostic coronary angiographies were performed between January 2015 and December 2015 at our facility. Of these, 886 coronary angiographies of CABG patients were detected. Whereas LIMA graft occlusion detected in 19 patient (2.1%), the LIMA-LAD CF rate was found in 86 (9.7%) CABG patients. The angiographic severity of the LAD stenosis in CF group evaluated as mild in 20 (25%), moderate in 61 (70%), and severe coronary artery disease in 4 (5%) patients. Our results showed that there is 9.7% rate of LIMA-LAD CF. Therefore, some unnecessary coronary stenting or CABG procedures might have been performed due to limited use of functional testing for clinical decision making. The functional angiography should play a more prominent role in catheterization laboratories as recommended by current revascularization guidelines to prevent overdiagnosis, misdiagnosis, or incorrect treatment decisions.

On the relationship between competitive flow and FFT analysis of the flow waves in the left internal mammary artery graft in the process of CABG

BACKGROUND

During coronary artery bypass grafting (CABG), the ratio of powers of the fundamental frequency and its first harmonic (F0/H1) in fast Fourier transformation (FFT) analysis of the graft's flow waves has been used in the field of evaluation of the patency in anastomosis. But there is no report about using the FFT method to evaluate the magnitude of competitive flow. This study is aiming at exploring the relationship between competitive flow and FFT analysis of the flow waves in left internal mammary artery (LIMA) graft, and finding a new method to evaluate the magnitude of competitive flow.

METHODS

At first, establishing the CABG multiscale models of different stenosis in left anterior descending artery (LAD) to get different magnitude of competitive flows. Then, calculating the models by ANSYS-CFX and getting the flow waves in LIMA. Finally, analyzing the flow waves by FFT method and comparing the FFT results with the magnitude of competitive flow.

RESULTS

There is no relationship between competitive flow and F0/H1. As for F0/H2 and F0/H3, they both increase with the reduction of the stenosis in LAD. But the increase of F0/H3 is not obviously enough and it can't identify the significant competitive flow clearly, so it can't be used as the evaluation index. It is found that F0/H2 increases obviously with the increase of the competitive flow and can identify the significant competitive flow.

CONCLUSION

The FFT method can be used in the evaluation of competitive flow and the F0/H2 is the ideal index. High F0/H2 refers to the significant competitive flow. This method can be used during CABG to avoid the risk of competitive flow.

A tool for training in decision making for emergency general surgery--explicit training is possible through facilitation

BACKGROUND

Emergency general surgery is increasingly recognized as an area for improvement within the National Health Service in the United Kingdom. Our aim was to test the feasibility of a tool we developed in assessing and facilitating surgical decision making by trainees in the emergency setting.

METHODS

A decision-making tool based on common decisions in surgery was designed and incorporated prospectively into patient clerking. The 10 decisions available to surgeons were divided into 3 major headings: discharge decisions, observation decisions, and operative decisions. "Ideal decisions" were derived from the final diagnosis on discharge by 2 independent clinicians and compared with initial decisions made by surgeons. We analyzed the data with a view to validate the tool using 2 methods. Firstly, we looked at the percentage of correct decisions made by different grades of surgeon, and secondly, we analyzed the trends in deviations from ideal decisions.

RESULTS

The decision-making tool was completed for 136 emergent surgical admissions over 2 months. Interns made less "ideal" decisions compared with residents (45% vs 56%, respectively; p = 0.10, Fisher exact test) and attending surgeons (45% vs 70%, respectively; p = 0.0001). Interns made more "admit and observe or investigate" decisions compared with residents (63% vs 55%, respectively; p = 0.27) and attending surgeons (63% vs 51%, respectively; p = 0.01), who were more likely to decide to operate on or discharge patients. A repeat study over the subsequent 2-month period has shown comparable findings in proportion of ideal decisions for each grade of surgeon.

CONCLUSIONS

There are significant differences in the proportion of "ideal decisions" and types of decisions between interns and attending surgeons suggesting a learning curve and potential for using this tool in decision-making training. The tool inherently facilitates discussion over decisions made by making these explicit. Repeating the study revealed an internal consistency.

Harmonic scalpel versus electrocautery for harvest of radial artery conduits: reduced risk of spasm and intimal injury on optical coherence tomography

OBJECTIVE

Vasospasm is the primary obstacle to widespread adoption of the radial artery as a conduit in coronary artery bypass grafting. We used optical coherence tomography, a catheter-based intravascular imaging modality, to measure the degree of radial artery spasm induced by means of harvest with electrocautery or a harmonic scalpel in patients undergoing coronary artery bypass grafting.

METHODS

Radial arteries were harvested from 44 consecutive patients with a harmonic scalpel (n = 15) or electrocautery (n = 29). Vessels were imaged before harvesting and after removal from the arm, with saphenous vein tracts serving as internal controls. Optical coherence tomographic findings for the degree of harvesting-induced injury were validated against histologic measures.

RESULTS

Optical coherence tomographic measures of endovascular dimensions and injury correlated strongly with histologic findings. Mean luminal volume, a measure of vasospasm, decreased significantly less after harvesting with a harmonic scalpel (9% +/- 7%) than with electrocautery (35% +/- 6%, P = .015). Completely intact intima was present in 11 (73%) of 15 radial arteries harvested with a harmonic scalpel (73%) compared with 9 of 29 arteries harvested by means of electrocautery (31%, P = .011). Intraoperative flow measurements and patency rates at 5 days postoperatively were not significantly different among groups.

CONCLUSIONS

Optical coherence tomography provides a level of speed and accuracy for quantifying endothelial injury and vasospasm that has not been described for any other modality, suggesting potential as an intraoperative quality assurance tool. Our optical coherence tomographic findings suggest that the harmonic scalpel induces less spasm and intimal injury compared with electrocautery.

Intraoperative detection of intimal lipid in the radial artery predicts degree of postoperative spasm

BACKGROUND

The radial artery's (RA) tendency to spasm when used as a bypass graft may relate to features of the RA itself. We imaged RA conduits before and after CABG in order to characterize intimal abnormalities that might relate to the risk of spasm.

METHODS

RA conduits from thirty-two CABG patients were imaged intraoperatively using catheter-based optical coherence tomography (OCT) and again on day 5 using 64-channel MDCT angiography. The change in luminal diameter between timepoints was measured in the proximal, mid and distal RA. "Spasm" was defined as focal or diffuse luminal narrowing to a diameter less than the target coronary. Lipid content in the RA was quantified by the degree of light attenuation on the OCT image.

RESULTS

Postoperative spasm was diagnosed in 18 of 32 (56%) RA grafts with the distal RA showing the most severe change versus the mid and proximal portions (-24.1+/-43.2% vs. -15.3+/-40.7%, -9.0+/-42.5% change in diameter respectively, p<0.01). The degree of attenuation of the OCT signal produced by the RA was strongly correlated with % diameter change (R=0.64, p=0.0005) and was significantly more pronounced in grafts with spasm versus no spasm (-1.97+/-0.61mm(-1) vs. -0.81+/-0.57mm(-1), p<0.0001). Histology confirmed lipid deposits in areas of RA with strong attenuation.

CONCLUSIONS

RA conduits otherwise considered acceptable for bypass grafting were often found by OCT imaging to have a substantial amount of lipid, which in turn strongly relates to the risk of postoperative spasm. Screening conduits based on characteristics of intimal quality may improve results following RA grafting.

Optical coherence tomography imaging as a quality assurance tool for evaluating endoscopic harvest of the radial artery

BACKGROUND

Concerns about intimal disruption and spasm have limited enthusiasm for endoscopic radial artery harvest (ERAH), although the risk of these problems after this procedure remains uncertain. Radial artery conduits were screened intraoperatively before and after ERAH vs open harvest using catheter-based high-resolution optical coherence tomography (OCT) imaging.

METHODS

Twenty-four cadavers and 60 coronary artery bypass graft (CABG) patients scheduled to receive a RA graft underwent OCT imaging before (in situ) and after (ex vivo) open harvest or ERAH. Spasm was quantified by the percentage change in luminal volume between images. Intimal disruption was classified as minor or severe depending on whether the defect was confined to branch ostia or involved the luminal surface. Histology was used to confirm OCT findings.

RESULTS

Luminal volume significantly declined after harvest in all RAs from CABG patients, but there was no difference between groups: -43% +/- 29% vs -35% +/- 38% change after ERAH (n = 21) vs open harvest (n = 39; p = 0.342). Significantly more intimal injury was noted after ERAH vs open harvest (34/41 vs 9/43, intimal tears/total evaluated RAs, p < 0.0001). Most intimal injury was minor: only 2 tears involved the luminal surface of the RA (both after ERAH). Serial imaging in cadavers revealed that 86% of ostial tears occur in ERAH during the initial blunt dissection step using the endoscope.

CONCLUSIONS

Although branch injury is a pitfall of ERAH, OCT imaging documented that the quality of RA procured is acceptable and comparable with open harvest. Catheter-based OCT provides an important quality assurance tool for RA harvest.

How do surgeons make intraoperative decisions?

Surgeons' intraoperative decision making is a key element of clinical practice, yet has received scant attention in the surgical literature. In recent years, serial changes in the configuration of surgical training in the UK have reduced the time spent by trainees in the operating theatre. The opportunity to replace this lost experience with active teaching of decision making is important, but there seem to have been very few studies that have directly examined the cognitive skills underlying surgical decision making during operations. From the available evidence in surgery, and drawing from research in other safety-critical occupations, four decision-making strategies that surgeons may use are discussed: intuitive (recognition-primed), rule based, option comparison and creative. Surgeons' decision-making processes should be studied to provide a better evidence base for the training of cognitive skills for the intraoperative environment.