Does off-pump total arterial grafting increase the incidence of intraoperative graft failure?

In-Hospital Graft Occlusion in Post-Coronary Artery Bypass Grafting Patients in the Early Postoperative Period: A Systematic Review and Meta-Analysis

Objectives: The objectives of this paper are to evaluate the incidence of early graft occlusion during hospital stays following coronary bypass surgery (CABG) and to assess the factors influencing the odds of in-hospital early graft occlusion. Methods: Reports evaluating the early in-hospital occlusion of coronary bypass grafts were identified through PubMed, Embase, and Cochrane databases. The primary endpoint was to determine the incidence of early graft occlusion following CABG before discharge and to identify and quantify the impact of demographic, clinical, and procedural risk factors on the occurrence of early graft occlusion. The meta-analysis was conducted using a random-effects inverse-variance model with the DerSimonian-Laird estimator, assessing incidence rates, risk factors, and study heterogeneity, with statistical analysis performed using Stata. Results: A total of 22 studies with 35,798 patients were included in the analysis. The overall incidence of in-hospital early graft occlusion was 5% (95% CI: 3% to 7%). In studies using symptom-driven patency assessment, the incidence of occlusion was 2%, whereas in those employing systematic graft patency assessment, it was 6%. Only the presence of a vein graft OR 2.13 (95% CI: 1.19-3.82) was significantly associated with in-hospital graft occlusion. Conclusions: The incidence of in-hospital early graft occlusion seems substantially underestimated if imaging is restricted only to symptomatic patients. Moreover, female gender, increased PI, and the presence of a composite graft could also be potential risk factors for this complication.

Influence of residual coronary flow on bypass graft flow for graft assessment using near-infrared fluorescence angiography

PURPOSE

Near-infrared fluorescence angiography (NIR) detects the attenuation of fluorescence luminance intensity (FLI) through coronary artery bypass grafts affected by anastomotic stenosis. This study investigates the influence of residual blood flow of the host coronary artery (Ho) on bypass graft (Gr) FLI using a coronary artery bypass (CABG) model.

METHODS

A mock circuit system was created using artificial vessels and artificial blood was supplied to the Gr and the Ho. We used NIR to examine the changes in FLI through the Gr.

RESULTS

The Gr FLI was significantly attenuated according to the degree of Gr stenosis. The Gr FLI did not differ significantly among all degrees of Ho stenosis. High FLI grafts included grafts with degrees of Gr stenosis ≤ 75%, regardless of the severity of Ho stenosis. Moderate and low FLI grafts had 90 or 99% Gr stenosis, regardless of the severity of Ho stenosis. Gr FLI with 99% Gr stenosis was higher in 99% Ho stenosis than in ≤ 90% Ho stenosis.

CONCLUSIONS

A high Gr FLI indicated the absence of ≥ 90% stenosis in the anastomosis and a low Gr FLI indicated severe stenosis in the anastomosis despite Ho stenosis. High Ho stenosis may prevent the attenuation of Gr FLI in severely stenosed grafts.

Techniques for intraoperative graft assessment in coronary artery bypass surgery

Early graft patency is a major determinant of morbidity and mortality following coronary artery bypass surgery. Long-term graft failure is caused by intimal hyperplasia and atherosclerosis, while early failure, especially in the first year, has been attributed, in part, to surgical error. The need for intraoperative graft evaluation is paramount to determine need for revision and ensure future functioning grafts. Transit time flowmetry (TTFM) is the most commonly used intraoperative modality, however, only about 20% of cardiac surgeons in North America use TTFM. When combined with high resolution epicardial ultrasonography, TTFM provides high diagnostic yield. Fluorescence imaging can provide excellent visualization of the coronary and graft vasculature; however, data on this subject is limited. We herein examine the literature and discuss the available techniques for graft assessment along with their limitations.

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.

Fractional flow reserve-guided coronary artery bypass grafting: can intraoperative physiologic imaging guide decision making?

OBJECTIVES

Fractional flow reserve-guided coronary artery bypass grafting is emerging in cardiac surgery, in which the nature (anatomic and functional characteristics) of the target vessel epicardial coronary artery stenosis is important in graft site selection. The nature of the stenosis might determine a different physiologic response to bypass grafting. We report our recent experience using near infrared fluorescence complex angiography and perfusion analysis to identify the nature of stenoses in the target vessel by imaging the physiologic response to grafting.

METHODS

In 167 patients who underwent consecutive multivessel coronary artery bypass grafting cases (63% off-pump coronary artery bypass grafting) with traditional anatomy-based revascularization, we imaged and analyzed 359 grafts (53% arterial). This platform provides angiographic data of both the target vessel epicardial coronary artery and graft simultaneously (to assess the imaged competitive flow); and because a change in fluorescence intensity is proportional to the change in blood flow and perfusion, the quantified change (if any) in regional myocardial perfusion surrounding the grafted target vessel epicardial coronary artery.

RESULTS

The patient outcomes in our series were excellent. All 359 grafts were widely patent by angiography, and 24% of the arterial and 22% of the saphenous vein grafts showed no regional myocardial perfusion change in response to bypass grafting. In 165 in situ internal mammary artery grafts to the left anterior descending artery (>70% stenosis), 40 had no change in regional myocardial perfusion, and 32 of the 40 had competitive flow imaged.

CONCLUSIONS

An important number of angiographically patent bypass grafts demonstrated no change in regional myocardial perfusion, suggesting anatomic, but nonfunctional, stenoses in those target vessel epicardial coronary arteries. In in situ arterial grafts, imaged competitive flow is associated with nonfunctional stenoses in the target vessel epicardial coronary artery. Imaging these physiologic responses to target vessel revascularization might be useful in the emerging fractional flow reserve-guided era.

Detection of sentinel lymph nodes in patients with endometrial cancer undergoing robotic-assisted staging: a comparison of colorimetric and fluorescence imaging

OBJECTIVE

To retrospectively compare results from lymphatic mapping of pelvic sentinel lymph nodes (SLN) using fluorescence near-infrared (NIR) imaging of indocyanine green (ICG) and colorimetric imaging of isosulfan blue (ISB) dyes in women with endometrial cancer (EC) undergoing robotic-assisted lymphadenectomy (RAL). A secondary aim was to investigate the ability of SLN biopsies to increase the detection of metastatic disease.

METHODS

Thirty-five patients underwent RAL with hysterectomy. One mL ISB was injected submucosally in four quadrants of the cervix, followed by 0.5 mL ICG [1.25mg/mL] immediately prior to placement of a uterine manipulator. Retroperitoneal spaces were dissected for colorimetric detection of lymphatic pathways. The da Vinci(®) camera was switched to fluorescence imaging and results recorded. SLN were removed for permanent analysis with ultra-sectioning, H&E, and IHC staining. Hysterectomy with RAL was completed.

RESULTS

Twenty-seven (77%) and 34 (97%) of patients had bilateral pelvic or aortic SLN detected by colorimetric and fluorescence, respectively (p=0.03). Considering each hemi-pelvis separately, 15/70 (21.4%) had "weak" uptake of ISB in SLN confirmed positive with fluorescence imaging. Using both methods, bilateral detection was 100%. Ten (28.6%) patients had lymph node (LN) metastasis, and 9 of these had SLN metastasis (90% sensitivity, one false negative SLN biopsy). Seven of nine (78%) SLN metastases were ISB positive and 100% were ICG positive. Twenty-five had normal LN, all with negative SLN biopsies (100% specificity). Four (40%) with LN metastasis were detected only by IHC and ultra-sectioning of SLN.

CONCLUSIONS

Fluorescence imaging with ICG detected bilateral SLN and SLN metastasis more often than ISB, and the combination resulted in 100% bilateral detection of SLN. Ultra-sectioning/IHC of SLN increased the detection of lymph node metastasis.

Near infrared fluorescence imaging with ICG in TECAB surgery using the da Vinci Si surgical system in a canine model

BACKGROUND

This study assessed the clinical utility of near-infrared fluorescence imaging using indocyanine green in off-pump beating heart total endoscopic and robotic-assisted coronary artery bypass using the fluorescence imaging system for the da Vinci Si on a canine model for vessel identification, graft patency, and correlation of graft patency with ultrasound transit-time flow measurement probe.

METHODS

Beating heart total endoscopic robotic-assisted coronary artery bypass was performed on eight canine using indocyanine green and fluorescence imaging to identify the internal mammary artery prior to harvesting, the coronary vessel anatomy, and the patency of the beating heart total endoscopic coronary artery bypass anastomosis. Three to four injections of indocyanine green with a dose of 1.25 mg to 2.5 mg were administered per animal. Transit-time flow was measured in each of the dogs.

RESULTS

High definition 3D images were obtained. The camera working distance, indocyanine green dosage, internal mammary artery visualization, coronary artery visualization, patency by indocyanine green injection, and patency by transit-time flow were recorded. Six cases were completed successfully, and all demonstrated correlation between indocyanine green measurements of flow, and the transit-time flow measurement.

CONCLUSION

Use of near-infrared fluorescence with indocyanine green was feasible in our study, and would be of great benefit during total endoscopic robotic-assisted coronary artery bypass using the fluorescence imaging-capable da Vinci Si system to help identify the internal mammary artery, delineate the coronary anatomy, and also determine patency of the anastomoses. This procedure correlated well with transit-time flow measurement.

Fluorescent angiography

Fluorescent angiography is a simple and effective real-time tool for measurement of tissue perfusion both in and out of the operating room. It has multiple uses including: (1) identifying perforating vessels during flap planning; (2) locating primary and secondary angiosomes within a prepared flap; (3) as an aid in decision making for tissue debridement and flap creation; (4) intraoperative evaluation of microanastomoses; (5) postoperative flap monitoring, and (6) documentation of perfusion. The technology is easy to use in the hands of the operating surgeon and is safe for the patient, as it requires no radiation exposure.

Sentinel node biopsy in breast cancer using infrared laser system first experience with PDE camera

BACKGROUND

Sentinel node biopsy (SNB) is a gold standard in staging of early breast cancer. Nowadays, routine mapping of lymphatic tract is based on two tracers: human albumin with radioactive technetium, with or without blue dye. Recent years have seen a search for new tracers to examine sentinel node as well as lymphatic network. One of them is indocyanine green (ICG) visible in infrared light.

AIM

The aim of this study is to evaluate clinical usage of ICG in comparison with standard tracer, i.e. nanocoll, in SNB of breast cancer patients.

MATERIALS AND METHODS

In the 1st Department of Surgical Oncology and General Surgery, Greater Poland Cancer Centre, Poznań, 13 female breast cancer patients have benn operated since September 2010. All these patients had sentinel node biopsy with nanocoll (human albumin with radioactive technetium), and with indocyanine green. The feasibility of this new method was assessed in comparison with the standard nanocoll.

RESULTS

A lymphatic network between the place of injection of ICG and sentinel node was seen in infrared light. An area where a sentinel node was possibly located was confirmed by gamma probe. Sensitivity of this method was 100%.

CONCLUSION

SNB using ICG is a new, promising diagnostics technique. This procedure is not without drawbacks; nevertheless it opens new horizons in lymphatic network diagnostics.

Near-Infrared Fluorescence Imaging in Humans with Indocyanine Green: A Review and Update

Near-infrared (NIR) fluorescence imaging clinical studies have been reported in the literature with six different devices that employ various doses of indocyanine green (ICG) as a non-specific contrast agent. To date, clinical applications range from (i) angiography, intraoperative assessment of vessel patency, and tumor/metastasis delineation following intravenous administration of ICG, and (ii) imaging lymphatic architecture and function following subcutaneous and intradermal ICG administration. In the latter case, NIR fluorescence imaging may enable new discoveries associated with lymphatic function due to (i) a unique niche that is not met by any other conventional imaging technology and (ii) its exquisite sensitivity enabling high spatial and temporal resolution. Herein, we (i) review the basics of clinical NIR fluorescence imaging, (ii) survey the literature on clinical application of investigational devices using ICG fluorescent contrast, (iii) provide an update of non-invasive dynamic lymphatic imaging conducted with our FDPM device, and finally, (iv) comment on the future NIR fluorescence imaging for non-invasive and intraoperative use given recent demonstrations showing capabilities for imaging following microdose administration of contrast agent.

Evaluation of sentinel node biopsy by combined fluorescent and dye method and lymph flow for breast cancer

BACKGROUND

Conservative breast resection with subsequent sentinel lymph node biopsy (SNB) is an increasingly popular initial approach for the treatment of breast cancer due to decreased invasiveness. SNB is a shorter procedure with fewer side effects than more substantial surgical procedures, but it sometimes fails to identify metastatic disease. Therefore, a highly sensitive and convenient method is needed to identify sentinel lymph nodes (SLN) with a high probability of containing disease in SNB. We compared the combination of radioisotope or dye with a fluorescence compound to analyze lymph flow to identify targets for SNB.

MATERIALS AND METHODS

We examined patients with breast cancer lacking metastases in the axillary lymph node (ALN). Two methods for targeted SNB were developed: (1) Indocyanine Green (ICG) and Patent blue were injected into the skin overlying the tumor and sub-areolar region just before the surgical procedure. (2) ICG and radiocolloid were injected into the skin overlying the tumor and sub-areolar region. The draining fluorescent lymphatic duct was visualized using a Photodynamic Eye (PDE). We removed the SLNs that were identified by the dye and fluorescence imaging methods. Method 1 was applied to 113 patients undergoing SNB, and 29 patients were treated with Method 2. In our study, patients were grouped by lymph flow into two types: Type C demonstrated convergence to one lymph duct. Type S demonstrated separate lymph ducts.

RESULTS

Using the fluorescence imaging method, 99.3% of SLNs were identified, and 3.8 SLNs per patient were seen. The SLN identification rates for Patent blue dye and radiocolloid were 92.9% and 100%, respectively, while 1.9 and 2.0 SLNs per patient, respectively, were seen with these methods. We classified two types of lymph flow based on the pattern of lymphatic drainage. Type C converged to a single lymph duct, while Type S drained to separate ducts. Type S lymph drainage was seen in 29/142 patients (20.4%), and Type C drainage was found in 113/141 patients (79.6%). Of the patients with Type S drainage, there were 4.1 SLNs per patient, but only 3.4 SLNs per patient were seen in individuals with Type C drainage. Forty cases had metastases found in the ALNs, and five of these cases were dye-negative and fluorescence-positive. Among these cases, the average number of SLNs identified was one.

CONCLUSION

The combination of fluorescence with a visible dye is a highly sensitive method for SLN identification. When SNB is guided by only the dye method, there is a risk of missing appropriate SLNs in patients with Type S lymph drainage or weak dye staining. The use of a fluorescence method together with dye could increase sensitivity of detection in these cases. Furthermore, fluorescent methods are ideal for hospitals that cannot use conventional radioactive measures.

New device for intraoperative graft assessment: HyperEye charge-coupled device camera system

PURPOSE

Our institution developed a new color chargecoupled device (CCD) camera system (HyperEye system) for intraoperative indocyanine green (ICG) angiography. The device consists of a combination of custommade optical filters and an ultra-high-sensitive CCD image sensor with non-Bayer color filter array (i.e., HyperEye technology), which can detect simultaneously color and near-infrared (NIR) rays from 380 to 1200 nm. Here, we demonstrate intraoperative graft assessment using the HyperEye system.

METHODS

We investigated the intraoperative graft patency using both the HyperEye system and transittime flowmetry (TFM) in 51 patients between April 2007 and April 2009 while ICG dye was injected through a central venous catheter. Each patient signed a consent form before the surgery.

RESULTS

We obtained intraoperative graft flows and images in 189 anastomoses of 153 grafts. Both the HyperEye system and TFM indicated the patency of the grafts in 129 grafts. Both the HyperEye system and TFM detected the abnormality of the graft in seven grafts. For the competitive flows, the HyperEye system captured to-and-fro flow fluorescence and TFM detected the retrograde waveform in 16 grafts. On the other hand, although TFM indicated the patency of the graft, the HyperEye system suspected nonoccluded graft failure in seven grafts. In contrast, although TFM detected a mean flow of <10 ml/min, the HyperEye system captured the patent perfusion fluorescence in four grafts.

CONCLUSION

The HyperEye system can visualize any structural and functional failures. Our findings suggest that this device could become a useful tool for intraoperative graft assessment.

On-pump versus off-pump coronary-artery bypass surgery

BACKGROUND

Coronary-artery bypass grafting (CABG) has traditionally been performed with the use of cardiopulmonary bypass (on-pump CABG). CABG without cardiopulmonary bypass (off-pump CABG) might reduce the number of complications related to the heart-lung machine.

METHODS

We randomly assigned 2203 patients scheduled for urgent or elective CABG to either on-pump or off-pump procedures. The primary short-term end point was a composite of death or complications (reoperation, new mechanical support, cardiac arrest, coma, stroke, or renal failure) before discharge or within 30 days after surgery. The primary long-term end point was a composite of death from any cause, a repeat revascularization procedure, or a nonfatal myocardial infarction within 1 year after surgery. Secondary end points included the completeness of revascularization, graft patency at 1 year, neuropsychological outcomes, and the use of major resources.

RESULTS

There was no significant difference between off-pump and on-pump CABG in the rate of the 30-day composite outcome (7.0% and 5.6%, respectively; P=0.19). The rate of the 1-year composite outcome was higher for off-pump than for on-pump CABG (9.9% vs. 7.4%, P=0.04). The proportion of patients with fewer grafts completed than originally planned was higher with off-pump CABG than with on-pump CABG (17.8% vs. 11.1%, P<0.001). Follow-up angiograms in 1371 patients who underwent 4093 grafts revealed that the overall rate of graft patency was lower in the off-pump group than in the on-pump group (82.6% vs. 87.8%, P<0.01). There were no treatment-based differences in neuropsychological outcomes or short-term use of major resources.

CONCLUSIONS

At 1 year of follow-up, patients in the off-pump group had worse composite outcomes and poorer graft patency than did patients in the on-pump group. No significant differences between the techniques were found in neuropsychological outcomes or use of major resources. (ClinicalTrials.gov number, NCT00032630.).

Intraoperative fluorescence imaging system for on-site assessment of off-pump coronary artery bypass graft

OBJECTIVES

The aim of this study was to evaluate the intraoperative fluorescence imaging (IFI) system in the real-time assessment of graft patency during off-pump coronary artery bypass graft.

BACKGROUND

Intraoperative fluorescence imaging is an intraoperative angiography-like imaging modality using fluorescent indocyanine green excited with laser light. Recently, assessment of graft patency using the IFI system was introduced into clinical use. The feasibility and efficacy of IFI technology in off-pump coronary artery bypass graft has not been systematically compared with other conventional diagnostic modalities.

METHODS

Patients undergoing off-pump coronary artery bypass graft received IFI analysis, intraoperative transit time flowmetry, and postoperative X-ray angiography. In off-line IFI analysis, the graft washout was classified based on the number of heartbeats required for indocyanine green washout: fast washout (<or=15 beats) and slow washout (>15 beats).

RESULTS

A total of 507 grafts in 137 patients received IFI analysis. Of all the IFI analyses, 379 (75%) grafts were visualized clearly up to the distal anastomosis. With regard to anastomosis location, anterior location was associated with a higher percentage of fully analyzable images (90%). More than 80% of images were analyzable, irrespective of graft type. Six grafts with acceptable transit time flowmetry results were diagnosed with graft failure by IFI, which required on-site graft revision. All revised grafts' patency was confirmed by post-operative X-ray angiography. Conversely, 21 grafts with unsatisfactory transit time flowmetry results demonstrated acceptable patency with IFI. Graft revision was considered unnecessary in these grafts, and 20 grafts (95%) were patent by post-operative X-ray angiography. Compared with slow washout, fast washout was associated with a higher preoperative ejection fraction, use of internal mammary artery grafts, and anterior anastomosis location.

CONCLUSIONS

The IFI system enables on-site assessment of graft patency, providing both morphologic and functional information. This technique may help reduce procedure-related, early graft failures in off-pump bypass patients.

Preliminary experience for the evaluation of the intraoperative graft patency with real color charge-coupled device camera system: an advanced device for simultaneous capturing of color and near-infrared images during coronary artery bypass graft

We developed a new color charge-coupled device (CCD) camera for the intraoperative indocyanine green (ICG) angiography. This device consists of a combination of custom-made optical filters and an ultra-high sensitive CCD image sensor, which can detect simultaneously color and near-infrared (NIR) rays from 380 to 1200 nm. We showed a comparison between our system and other devices for the preliminary experience. We routinely performed both transit-time flowmetry (TFM) and color images for intraoperative assessment, thallium-scintigraphy for the early postoperative assessment, and then angiography after 1-year surgery. We also obtained intraoperative graft flows and images in 116 grafts. Although TFM indicated a graft patency, the CCD camera suspected perfusion failures in four grafts. Also the analysis of the ICG fluorescence intensity showed the significant hypoperfusion at the perfusion territory distal to the anastomosis (graft vs. perfusion territory; 230+/-26 vs. 156+/-13 a.u, P=0.02). When the CCD camera suspected a graft failure, CCD camera and angiography showed a comparable graft failure. The unique device that visualized ICG-enhanced structures against a background of natural myocardial color improved the visibility of abnormality in flow and perfusion. Our findings show that this device may become a standard intraoperative graft and perfusion assessment tool in coronary artery bypass graft (CABG).

Intraoperative identification of sentinel lymph nodes by near-infrared fluorescence imaging in patients with breast cancer

We present a novel method for sentinel lymph node (SLN) identification by fluorescence imaging that provides a high detection rate and a low false-negativity rate. Twenty-five breast cancer patients with tumors less than 3 cm in diameter were enrolled. A combination of indocyanine green and indigo carmine was injected subdermally in the areola. Subcutaneous lymphatic channels draining from the areola to the axilla were immediately showed by fluorescence imaging. After incising the axillary skin near the point of disappearance of the fluorescence, the SLN was dissected under fluorescence guidance. In all patients, the lymphatic channels and SLN were successfully visualized. The mean number of fluorescent SLN and blue-dyed SLN were 5.5 and 2.3. Eight patients were found to have lymph node metastases pathologically. All of them were recognized by fluorescence imaging. This method is feasible and safe for intraoperative detection of SLN allowing real-time observation without any need for training.

Using an automated emboli detection device in a porcine cardiopulmonary bypass (CPB) model: feasibility and considerations

The significant risk of cerebral embolism during cardiopulmonary bypass (CPB) makes monitoring of embolic events advisable already when developing new operation and coagulation management strategies for example in CPB animal models. The present study therefore evaluated in a porcine CPB model the feasibility of bilateral epicarotid Doppler signal recording and the quality of manual or automatic emboli detection. A total of 42 recordings (e.g. right carotid artery (n = 20), left carotid artery (n = 22)) were evaluated. The frequency of emboli counts was comparable for both carotid arteries. Automatic emboli detection, however, found significantly more embolic events per pig than did post-hoc manual off-line analysis of the recordings (172 +/- 217 vs. 13 +/-10). None of the brains, however, showed any emboli or infarction area either in cross-examination or in histological evaluation. In conclusion, the present study showed the feasibility of using an epicarotid Doppler device for bilateral emboli detection in a porcine CPB model. Automatic on-line emboli detection, however, reported more embolic events than did post hoc, off-line manual analysis. Possible reasons for this discrepancy are discussed.

Fluorescent cardiac imaging: a novel intraoperative method for quantitative assessment of myocardial perfusion during graded coronary artery stenosis

BACKGROUND

The purpose of the present study was to examine whether the effect of coronary stenoses of variable severity on myocardial perfusion can be quantitatively assessed in vivo by analysis of fluorescent cardiac imaging (FCI) compared with the gold standard, the fluorescent microsphere method. FCI is a novel technology to visualize coronary vessels and myocardial perfusion intraoperatively using the indocyanine green dye with an infrared-sensitive imaging device.

METHODS AND RESULTS

Graded stenoses and total vessel occlusion of the left anterior descending coronary artery were created in 11 open-chest pigs. Stenoses were graded to reduce resting left anterior descending coronary artery flow by 25%, 50%, 75%, and 100% of baseline flow measured by transit-time flowmeter. FCI images were analyzed with a digital image processing system. The impairment of myocardial perfusion was quantified by background-subtracted peak fluorescence intensity and slope of fluorescence intensity obtained with FCI and compared with myocardial blood flow assessed by fluorescent microsphere. All stenoses resulted in an impairment of myocardial perfusion visualized by FCI. Occlusion of the left anterior descending coronary artery resulted in a total perfusion defect (no fluorescence intensity) of the corresponding anterior myocardial wall. During graded stenosis and total vessel occlusion, normalized background-subtracted peak fluorescence intensity and slope of fluorescence intensity decreased significantly (P<0.0001). Both background-subtracted peak fluorescence intensity (r=0.92, P<0.0001) and slope of fluorescence intensity (r=0.93, P<0.0001) analyzed by FCI demonstrated good linear correlation with fluorescent microsphere-derived myocardial blood flow.

CONCLUSIONS

The impairment of myocardial perfusion in response to increased coronary stenosis severity and total vessel occlusion can be quantitatively assessed by FCI and correlates well with results obtained by fluorescent microsphere.

Intraoperative Imaging Techniques to Assess Coronary Artery Bypass Graft Patency

Graft patency verification is increasingly recognized as an important component of coronary artery bypass grafting. Intuitively, eliminating intraoperative graft failure should reduce cardiac mortality and morbidity in the short term and improve clinical outcome in the long term. Although conventional angiography remains the gold standard technique for assessing graft patency, it is rarely available in the operating room and consequently several other less invasive approaches have been advocated. This article reviews the two currently most commonly used modalities for graft patency assessment, intraoperative fluorescence imaging and transit-time flowmetry, and discusses their value and limitations. Both techniques can reliably detect otherwise unsuspected occluded grafts and this is crucial for internal thoracic arteries because of their prognostic significance. Although neither technology can consistently identify more minor, non-occlusive abnormalities, the intraoperative fluorescence imaging technique seems to be more sensitive and less susceptible to "false positive" images.

Localization and quantification of platelet-rich thrombi in large blood vessels with near-infrared fluorescence imaging

BACKGROUND

Imaging of thrombus formation in vivo has been limited by the inability to directly visualize and measure thrombi in large blood vessels in real time. Near-infrared light, with its superior tissue penetration and reduced scatter, could potentially solve this problem.

METHODS AND RESULTS

Platelets were labeled with the near-infrared fluorophore IR-786. Optimal total fluorescence yield occurred at 6 attomoles of IR-786 per platelet. IR-786-labeled platelets were tested for their ability to detect thrombus formation in large animal model systems relevant to common human vascular procedures. Invisible near-infrared light did not distort the surgical field in any way, and even after optimization of per-platelet fluorescent yield, platelets remained fully functional. Intravenous infusion of just 3.6x10(10) labeled platelets into a 35-kg Yorkshire pig permitted thrombus visualization, with a signal-to-background ratio > or = 2, for at least 2 hours in coronary, carotid, and femoral vessels. Platelet-rich, actively growing clots were monitored in real time and quantified with respect to size and kinetics after injury to vessels, cutaneous incisions, intravascular stent insertion, or introduction of embolic coils. Similarly, formed clots were monitored in real time during thrombolysis with streptokinase and heparin. Vessel patency was assessed independently with a second near-infrared fluorescent blood pool agent.

CONCLUSIONS

IR-786-labeled platelets provide sensitive, specific, and real-time visualization of thrombi in thick-walled blood vessels. In addition to immediate application in cardiac, transplant, and vascular surgery, the mechanisms that underlie thrombus formation in large blood vessels can now be investigated.

Meta-analysis of randomized trials comparing off-pump with on-pump coronary artery bypass graft patency

BACKGROUND

Off-pump coronary artery bypass graft surgery (OPCAB) is increasingly becoming a widely used technique and challenges conventional on-pump coronary artery bypass grafting as the standard surgical therapy for coronary artery disease. Little information, however, is available concerning postoperative performance of bypass grafts done with this new technique. The aim of this study is to assess differences in graft patency between OPCAB and coronary artery bypass grafting by meta-analysis of data published in randomized trials.

METHODS

A literature search for the period beginning January 1990 until December 2004 supplemented with manual bibliographic review was performed for all peer-reviewed English-language publications. A systematic overview (meta-analysis) of randomized trials was conducted to assess differences between OPCAB and coronary artery bypass grafting in graft occlusion rates.

RESULTS

Literature search yielded five comparable randomized studies, for a total of 872 and 998 grafts performed during OPCAB and coronary artery bypass grafting procedures, respectively. Meta-analysis of these studies showed an increased risk of graft occlusion in the OPCAB group of patients, both when all the studies were analyzed together (odds ratio, 1.51; 95% confidence intervals, 1.15 to 1.99; p = 0.003), and when low-quality (odds ratio, 1.46; 95% confidence intervals, 1.05 to 2.03; p = 0.02) and high-quality (odds ratio, 1.65; 95% confidence intervals, 0.99 to 2.75; p = 0.05) studies were analyzed separately.

CONCLUSIONS

Cumulative analysis of the few prospective randomized studies currently available in the literature documents a reduction in postoperative patency of coronary artery bypass grafts performed during OPCAB procedures. The risk of reduced graft patency needs to be considered when choosing OPCAB as tailored strategy for selected patients.

A comparison of transit-time flowmetry and intraoperative fluorescence imaging for assessing coronary artery bypass graft patency

BACKGROUND

Intraoperative graft patency assessment during coronary artery bypass grafting enables detection and immediate correction of graft failure. Currently transit-time flowmetry is used to assess graft patency on the basis of mean graft flow and derived values, such as the pulsatility index. Intraoperative fluorescence imaging, based on the fluorescence of indocyanine green dye, provides direct visual images to confirm graft patency.

METHODS

We performed a prospective observational study to assess intraoperative graft patency in patients undergoing coronary artery bypass grafting, by using an intraoperative fluorescence imaging system (SPY) and transit-time flowmetry (BF 2004). Poor flow with the intraoperative fluorescence imaging system was defined if there was an absence of fluorescence or if it did not appear within 15 seconds in the graft. A persistent mean graft flow value less than 5 mL/min and a pulsatility index greater than 5 with transit-time flowmetry were considered unacceptable and prompted graft revision.

RESULTS

We assessed the intraoperative patency of 266 grafts in 100 coronary artery bypass grafting patients. Intraoperative fluorescence imaging and transit-time flowmetry confirmed adequate flow in 241 (91%) grafts in 75 patients (75%). Transient poor flow was detected with both intraoperative fluorescence imaging and transit-time flowmetry in 7 (2.6%) grafts in 7 (7%) patients. This subsequently proved to be adequate on repeat testing and hence did not necessitate graft revision. Both intraoperative fluorescence imaging and transit-time flowmetry confirmed persistent poor flow in 8 (3%) grafts in 8 (8%) patients that necessitated graft revision. However, in a further 10 (3.8%) grafts in 10 (10%) patients, transit-time flowmetry indicated persistently poor flows on the basis of mean graft flow and pulsatility index values, whereas the intraoperative fluorescence imaging system demonstrated satisfactory flow. These grafts were not revised.

CONCLUSIONS

In most patients, both intraoperative fluorescence imaging and transit-time flowmetry are useful to confirm intraoperative graft patency. However, in a small proportion of patients (10%), graft patency assessment with transit-time flowmetry alone might prompt unnecessary graft revision.

Bypassing the Pump

Improvements in techniques in coronary revascularization over the past decade have led to a revival of interest in off-pump coronary artery surgery. A fifth of coronary revascularization procedures are now performed off-pump. Randomized trials comparing off-pump surgery with conventional coronary artery bypass grafting using cardiopulmonary bypass (CPB) mainly included low-risk patients and were therefore underpowered to detect a difference in mortality. Current evidence, however, suggests a significant reduction in morbidity with off-pump surgery. The avoidance of CPB and the elimination of any aortic manipulation may significantly reduce the risk of stroke. Those benefits are likely to be most marked in older, sicker patients, who represent an increasing proportion of the surgical population.

Digital tools to facilitate intraoperative coronary artery bypass graft patency assessment

Intraoperative graft failure is an important cause of cardiac mortality and morbidity. Hence, verification of graft patency should be one of the most important aspects of coronary artery bypass grafting. Although several techniques have been advocated to assess intraoperative graft patency, there is no unanimously accepted method. Intraoperative fluorescence imaging is a novel technique based on the fluorescence of indocyanine green dye, which provides real-time visual images of graft flow in the operating room. Transit-time flowmetry is based on the ultrasound principle and provides mean graft flow and derived values such as pulsatility index. This article describes the usefulness and limitations of various techniques in general and summarizes the current knowledge with the use of these two techniques in the setting of intraoperative coronary artery bypass graft patency assessment.