The impact of nitroglycerine and volume on gastric tube microperfusion assessed by indocyanine green fluorescence imaging.

The influence of hypervolemia and intraoperative administration of nitroglycerine on gastric tube microperfusion remains unclear The present study aimed to investigate the impact of different hemodynamic settings on gastric tube microperfusion quantified by fluorescence imaging with Indocyanine green (ICG-FI) as a promising tool for perfusion evaluation. Three groups with seven pigs each were formed using noradrenaline, nitroglycerin, and hypervolemia for hemodynamic management, respectively. ICG-FI, hemodynamic parameters, and transit-time flow measurement (TTFM) in the right gastroepiploic artery were continuously assessed. Fluorescent microspheres (FM) were administered, and the partial pressure of tissue oxygen was quantified. The administration of nitroglycerine and hypervolemia were both associated with significantly impaired microperfusion compared to the noradrenaline group quantified by ICG-FI. Even the most minor differences in microperfusion could be sufficiently predicted which, however, could not be represented by the mean arterial pressure measurement. Histopathological findings supported these results with a higher degree of epithelial damage in areas with impaired perfusion. The values measured by ICG-FI significantly correlated with the FM measurement. Using tissue oxygenation and TTFM for perfusion measurement, changes in microperfusion could not be comprehended. Our results support current clinical practice with restrictive volume and catecholamine administration in major surgery. Hypervolemia and continuous administration of nitroglycerine should be avoided.

Quantification of gastric tube perfusion following esophagectomy using fluorescence imaging with indocyanine green.

INTRODUCTION: Anastomotic leakage (AL) remains a prevalent and life-threatening complication after esophagectomy. Gastric tube perfusion assessment using indocyanine green fluorescence imaging (ICG-FI) has been published in several studies and appears to be a promising tool to reduce AL rates by changing the surgical approach, namely by an intraoperative evaluation of the anastomosis localization. METHODS: In this study, gastric tube perfusion was quantified by using ICG-FI in 20 high-risk patients undergoing esophagectomy. From a time-dependent fluorescence intensity curve, the following three parameters were evaluated: slope of fluorescence intensity (SFI), background subtracted peak fluorescence intensity (BSFI), and time to slope (TTS). RESULTS: The values between pyloric region and tip showed a similar downward trend and SFI and BSFI significantly correlated with the distance to the pyloric region. SFI and BSFI were significantly decreased at the tip of the gastric tube. The placement of anastomosis in an area with homogenous fluorescence pattern was correlated with no AL in 92.9% of cases. An inhomogeneous fluorescence pattern at anastomotic site was a risk factor for the occurrence of an AL (p < 0.05). Reduction of perfusion up to 32% using SFI and up to 23% using BSFI was not associated with AL. CONCLUSION: ICG-FI can be used to quantify the gastric tube perfusion by calculating SFI, BSFI, and TTS. The anastomosis should be created in areas with homogeneous fluorescence pattern. A reduction in blood flow of up to 32% can be accepted without causing an increased rate of insufficiency.

Intraoperative quality assessment of tissue perfusion with indocyanine green (ICG) in a porcine model of mesenteric ischemia.

BACKGROUND: Mesenteric ischemia is a severe and potentially lethal event. Assessment of intestine perfusion is eminently depending on the skills, and the experience of the surgeon. Thus, the therapy is biased by the right evaluation. Aim of this study is to determine the applicability, and the usefulness of fluorescent-imaging (FI) with indocyanine green (ICG) in a porcine model of mesenteric ischemia. Second end-point is the verification of a visual and quantitative assessment tool of the intestinal perfusion. METHODS: In 18 pigs (54,2 ±2,9kg) an occlusion of a side-branch of the mesenteric artery was performed for 3 (group I, n = 7), 6 (group II, n = 7), and 10 hours (group III, n = 4). After reperfusion a 60 minutes observation period was carried out. 3 regions of interest were defined: ischemic bowel (D1), transitional zone (D2), and non-ischemic bowel (D3). ICG-FI was performed during baseline (T0), occlusion (T1), reperfusion (T2) and after an observation period of 60 minutes (T4). RESULTS: All experiments could be finished successfully. ICG-FI was assessed using assessment of background-subtracted peak fluorescence intensity (BSFI), slope of fluorescence intensity (SFI), and a baseline adjusted ratio of both parameters. ICG-FI confirmed loss of perfusion in D1, decreased perfusion in D2, and increased perfusion in D3. After reperfusion ICG-FI increased in group 2 due to a severe tissue damage resulting in a capillary leakage. In group I ICG-FI was equal to baseline values indicating the totally reversible loss of perfusion. CONCLUSION: Using ICG-FI to estimate intestine perfusion after different durations of ischemia is viable using a porcine model of mesenteric ischemia. Even small differences in perfusion can be reliably determined by ICG-FI. Thus, ICG-FI is an encouraging method to evaluate intestine perfusion intraoperatively.

Validation of quantitative assessment of indocyanine green fluorescent imaging in a one-vessel model.

OBJECTIVES: Evaluation of intestinal perfusion remains subjective and depends on the surgeon´s individual experience. Intraoperative quality assessment of tissue perfusion with indocyanine green (ICG) fluorescence using a near-infrared camera system has been described in different ways and for different indications. The aim of the present study was to evaluate fluorescent imaging (FI) in the quantitative assessment of intestinal perfusion in a gastric tube model in pigs and to compare the results to results obtained with florescent microspheres (FM), the gold standard for tissue perfusion. METHODS: Seven pigs (56.0±3.0 kg), both males and females, underwent gastric tube formation after transection and ligation of the gastric arteries, except the right gastroepiploic artery, to avoid collateral blood flow. After baseline assessment (T0), hypotension (T1) was induced by propofol (Karampinis et al 2017) (< 60 mmHg). Then, propofol was paused to obtain normotension (T2, Mean arterial pressure (MAP) 60-90 mmHg). Finally, hypertension (T3, MAP>90 mmHg) was induced by norepinephrine. Measurements were performed in three regions of interest (ROIs) under standardized conditions: the fundus (D1), corpus (D2), and prepyloric area (D3). Hemodynamic parameters and transit-time flow measurement (TTFM) in the right gastroepiploic artery were continuously assessed. FI, FM and the partial pressure of tissue oxygen (TpO2) were quantified in each ROI. RESULTS: The study protocol could successfully be performed during stable hemodynamics. Flow in the gastroepiploic artery measured by transit time flow measurement (TTFM) was related to hemodynamic changes between the measurements, indicating improved blood flow with increasing MAP. The distal part of the gastric tube (D1) showed significantly (p<0.05) impaired perfusion compared to the proximal parts D3 and D2 using FM. ICG-FI also showed the highest values in D3 and the lowest values in D1 at all hemodynamic levels (T1-T3; p<0,05). CONCLUSION: Visual and quantitative assessment of gastric tube perfusion is feasible in an experimental setting using ICG-FI. This might be a promising tool for intraoperative assessment during visceral surgery in the future.

Generation of a high-resolution 3D-printed freeform collimator for VCSEL-based 3D-depth sensing.

This Letter discusses the generation of 3D-printed micro-optics to obtain the desired beam profile from a multimode vertical-cavity surface-emitting laser (VCSEL) with a significantly reduced divergence angle via the usage of high-resolution two-photon polymerization. Due to the low cost and compact packaging, the VCSEL array is a novel light source for structured-light projection. Particularly for long-distance 3D sensing applications, a greatly reduced divergence angle ensures that a good signal with a sufficiently large number of photons can be recorded, and the projected illumination spots do not overlap. Therefore, exact laser beam characterization and appropriate physical modeling are required in accurate production of an optimal collimator lens. Furthermore, elliptical beam profiles with different orientations can solve the correspondence problem and improve the post-processing speed and robustness in structured light. To generate this special type of beam profile and verify the optical design process, this Letter describes thoroughly the optical prototyping process starting from the beam characterization, the optical design to the production of the two-photon polymerized optics, and its validation. The test of the beam profile and divergence confirm a good match of the produced optics with the physical optical simulation in Zemax. The collimator transforms the input laser beam divergence angle of 324 mrad to an output angle of 20 mrad only.

[Depth Effect of Cold Atmospheric Pressure Plasma in Keratitis Therapy: A Corneal Stroma Tissue Model]. / Tiefenwirkung von kaltem Atmosphärendruckplasma in der Keratitistherapie: ein Hornhautstromagewebemodell.

The incidence of microbial keratitis has been increasing and is now 28 cases/100,000 inhabitants; this may be due to the more frequent use of contact lenses. Keratitis can lead to visual impairment and in severe cases with endophthalmitis to enucleation of the affected eye. As microorganisms are becoming more resistant to antibiotic therapy, there is a need for new therapeutic strategies. Cold atmospheric pressure plasma has already been successfully used to disinfect surfaces. This study investigates the efficacy of cold atmospheric pressure plasma against Escherichia coli in a depth-resolved corneal stroma tissue model.

[In Vitro Study of Subablative Er : YAG Laser and Diode Laser Therapy vs. Thermal Cautery in Microbial Keratitis]. / In-vitro-Studie mit subablativem Er:YAG-Laser und Diodenlaser vs. Thermokauter zur Therapie der mikrobiellen Keratitis.

BACKGROUND: In microbial keratitis, thermal cautery leads to thermal necrosis associated with germ reduction. Subablative heating of the cornea using an Er : YAG laser or diode laser is an alternative option. Thermal effects and reproducibility of both procedures were investigated. MATERIAL AND METHODS: Thermal effects were monitored with an infrared imaging system. Temperature of stromal tissue of enucleated porcine eyes was measured. Effects of thermal injury were rated by microscopic photography and histopathologic examination. Reduction of living bacteria was visualized by laser scanning microscopy and fluorescent stain on stromal tissue models containing E. coli bacteria. RESULTS: Corneal samples showed thermal damage depths of 110 - 250 µm after thermal cautery at contact times of 1 - 3 s. Superficial temperature ranged from 70 to 80 °C. Thickness of thermal necrosis after laser irradiation was between 50 and 270 µm. Temperature ranged from 60 to 120 °C. Laser scanning microscopy of a stromal tissue model, comprising Escherichia coli bacteria in soft agar, showed a mortification of bacteria over 40% up to 100 µm depth after treatment for 25 s. Treatment with diode laser showed an even better effect: more than 60% of bacteria were dead up to 250 µm depth and more than 50% up to 450 µm depth in the stromal tissue model. CONCLUSIONS: All procedures are able to induce high temperatures in tissue to achieve effective germ reduction in corneal stroma. Effect and reproducibility of the thermal cautery procedure depends on the surgeon's experience. Energy dose and thermal effect can be calculated for the Er : YAG and diode laser procedure to affect the infected stromal layer selectively.

Qualitative angiographic and quantitative myocardial perfusion assessment using fluorescent cardiac imaging during graded coronary artery bypass stenosis.

Intraoperative graft assessment in coronary artery bypass (CAB) grafting is important to avoid early graft failure. This study aimed to evaluate the accuracy of fluorescent cardiac imaging (FCI) for intraoperative qualitative angiographic and quantitative myocardial perfusion assessment during graded CAB stenosis compared to coronary angiography (CA). After CAB grafting to the left anterior descending coronary artery, graded distal bypass stenoses were created in ten pigs by 25, 50, 75, and 100% flow reduction assessed by transit-time flow measurement (TTFM). Visual angiographic assessment was performed by FCI and CA during baseline and graded bypass stenoses. Altered myocardial perfusion was assessed by quantitative intraoperative fluorescence intensity (QIFI) derived from FCI and correlated to TTFM. Patent bypass grafts and graft occlusion were visualized successfully by FCI and CA, while discrimination between various graded bypass stenosis was possible in 73.3%. The degree of CAB stenosis was overestimated in 16.7% and underestimated in 10.0% by FCI compared to CA. Graded CAB stenosis reduced regional myocardial perfusion quantified by decreased QIFI value (p < 0.001). Mean QIFI value was 76.8 (95% CI 67.2-86.3) during baseline, 55.6 (95% CI 45.3-65.9) during 25% flow-reduction, 30.6 (95% CI 22.3-39.0) during 50% flow-reduction, 20.3 (95% CI 15.4-25.3) during 75% flow-reduction, and 0 during CAB occlusion (p < 0.001) with a significant correlation to TTFM (r = 0.955; p < 0.0001). Solely visual assessment of CAB quality using FCI is limited as compared to CA. Additional QIFI assessment identified graded CAB stenosis and occlusion with a significant correlation to TTFM.

Initial experience with a new quantitative assessment tool for fluorescent imaging in peripheral artery disease.

BACKGROUND: Perioperative evaluation in peripheral artery disease (PAD) by common vascular diagnostic tools is limited by open wounds, medial calcinosis or an altered collateral supply of the foot. Indocyanine green fluorescent imaging (ICG-FI) has recently been introduced as an alternative tool, but so far a standardized quantitative assessment of tissue perfusion in vascular surgery has not been performed for this purpose. The aim of this feasibility study was to investigate a new software for quantitative assessment of tissue perfusion in patients with PAD using indocyanine green fluorescent imaging (ICG-FI) before and after peripheral bypass grafting. PATIENTS AND METHODS: Indocyanine green fluorescent imaging was performed in seven patients using the SPY Elite system before and after peripheral bypass grafting for PAD (Rutherford III-VI). Visual and quantitative evaluation of tissue perfusion was assessed in an area of low perfusion (ALP) and high perfusion (AHP), each by three independent investigators. Data assessment was performed offline using a specially customized software package (Institute for Laser Technology, University Ulm, GmbH). Slope of fluorescent intensity (SFI) was measured as time-intensity curves. Values were compared to ankle-brachial index (ABI), slope of oscillation (SOO), and time to peak (TTP) obtained from photoplethysmography (PPG). RESULTS: All measurements before and after surgery were successfully performed, showing that ABI, TTP, and SOO increased significantly compared to preoperative values, all being statistically significant (P < 0.05), except for TTP (p = 0.061). Further, SFI increased significantly in both ALP and AHP (P < 0.05) and correlated considerably with ABI, TTP, and SOO (P < 0.05). CONCLUSIONS: In addition to ABI and slope of oscillation (SOO), the ICG-FI technique allows visual assessment in combination with quantitative assessment of tissue perfusion in patients with PAD. Ratios related to different perfusion patterns and SFI seem to be useful tools to reduce factors disturbing ICG-FI measurements.

Distinction of non-ischemia inducing versus ischemia inducing coronary stenosis by fluorescent cardiac imaging.

Intraoperative fluorescent cardiac imaging (FCI) can quantitatively assess myocardial perfusion abnormalities produced by graded flow-limiting coronary stenosis (FLS), but there are no data to distinguish FLS from non flow-limiting stenosis (NFLS) to determine their functional significance. The aim of the study was to evaluate whether non-ischemia inducing NFLS can be quantified and differentiated from FLS by FCI technology. Data are compared to gold standard fluorescent microspheres (FM). 11 domestic pigs of either sex underwent sternotomy. Left anterior descending coronary artery blood-flow was recorded by transit-time flow measurements. After baseline and Adenosine-induced hyperemia, two stenosis of low severity (50 and 90 % NFLS) were produced, followed by FLS (50 %) and total vessel occlusion. Time-dependent fluorescence intensity curves were recorded by FCI. Slope of fluorescence intensity (SFI) and background-subtracted peak fluorescence (BSFI) intensity were calculated and data compared to myocardial blood flow measurements using FM. All NFLS and FLS reduced myocardial perfusion as quantified by FCI showing decreased normalized BSFI and SFI (P < 0.001). Box-plot analysis showed significant difference between NFLS (50 and 90 %) and FLS (50 %) assessed by BSFI (P < 0.001) and SFI (P < 0.001). In each animal, a linear correlation between FM-derived myocardial blood flow and FCI-derived BSFI (r = 0.936, P < 0.001) or SFI (r = 0.942, P < 0.001) was observed during baseline, hyperemia, graded NFLS, and FLS. Both, BSFI (r = 0.789, P < 0.001) and SFI (r = 0.802, P < 0.001) significantly correlated with transit-time flow measurements. FCI quantitative technology is capable of distinguishing between non-ischemia inducing NFLS and ischemia inducing FLS showing a good correlation compared to fluorescent microspheres.

A phase IIA dose-finding study of PVP-hypericin fluorescence cystoscopy for detection of nonmuscle-invasive bladder cancer.

PURPOSE: To determine the optimum dosage and instillation time for water-soluble polyvinylpyrrolidone (PVP)-hypericin for photodynamic diagnosis of bladder cancer and to monitor its use in regard to patient safety. PATIENTS AND METHODS: Forty patients with a cystoscopically suspected bladder neoplasm were enrolled in this prospective phase IIA study. Different combinations of PVP-hypericin dosage (225 µg and 75 µg and instillation time (120, 60, 30, 15 min) were used to evaluate the optimal conditions. After a run-in cohort of five patients to validate the test method, each group comprised seven patients. All intravesical lesions were documented, and their fluorescence characteristics were recorded. Dose finding was the primary, safety the secondary end point. RESULTS: Fluorescence intensities for the first two groups (225 µg PVP-hypericin for 120 and 60 min, respectively) were not different. For group three (225 µg for 30 min), both specific fluorescence and background noise were reduced. A shorter instillation time (225 µg for 15 min) or lower dose (75 µg for 30 min) was considered insufficient for lesion identification. A dose of 225 µg PVP-hypericin instilled for 30 minutes was determined as appropriate for the detection of lesions. Of the total 93 identified lesions, 62 were detected with both white light and fluorescence, 25 were seen with blue light only, and six with white light only. It was possible to identify additionally two carcinoma in situ, eight pTa, and one pT1 lesions with PVP-hypericin and blue light. PVP-hypericin was safe and well tolerated. CONCLUSION: The optimum combination of dosage of PVP-hypericin and its instillation time was established and will be used to determine sensitivity and specificity of PVP-hypericin cystoscopy in a larger multicenter phase IIB study. The preliminary data of this study hint to a higher sensitivity of hypericin-assisted fluorescence cystoscopy.

Hemodynamic impact of transseptal access to the ascending aorta in a porcine model.

PURPOSE: To evaluate the hemodynamic impact of transseptal sheath access to the ascending aorta using increasing sheath diameters. METHODS: Transseptal puncture was performed in 6 pigs (62±9 kg) facilitating guidewire passage across the left heart to the descending aorta to establish transseptal through-and-through access into the ascending aorta. Hemodynamic parameters were evaluated during 6- to 16-F sheath deployments and after sheath retraction according to a standardized protocol. Fluorescent microspheres were injected for quantitative assessment of myocardial and cerebral perfusion and left-right shunting volume. RESULTS: Cardiac output, heart rate, and central venous pressure (CVP) were stable throughout the study in all animals. The ratio between pulmonary artery pressure and mean arterial pressure was significantly higher during sheath deployment compared to after retraction (p<0.01), indicating transient mitral valve insufficiency. The ratio between left atrial pressure and CVP was significantly higher with the sheath in place (p<0.01), signaling transient left-right shunting; the hemodynamic alteration disappeared after sheath retraction. Myocardial perfusion (p=0.224), cerebral perfusion (p=0.209), and left-right shunting volume (p=0.111) were not significantly affected by the transseptal access. CONCLUSION: Transseptal access to the ascending aorta in a porcine model is feasible without persisting hemodynamic impairment or severe influence on myocardial or cerebral perfusion even with up to 16-F sheaths. Potential adverse effects need to be addressed before clinical use of this alternative access to the ascending aorta, aortic arch, and its side branches.

Myeloperoxidase deficiency preserves vasomotor function in humans.

AIMS: Observational studies have suggested a mechanistic link between the leucocyte-derived enzyme myeloperoxidase (MPO) and vasomotor function. Here, we tested whether MPO is systemically affecting vascular tone in humans. METHODS AND RESULTS: A total of 12 135 patients were screened for leucocyte peroxidase activity. We identified 15 individuals with low MPO expression and activity (MPO(low)), who were matched with 30 participants exhibiting normal MPO protein content and activity (control). Nicotine-dependent activation of leucocytes caused attenuation of endothelial nitric oxide (NO) bioavailability in the control group (P < 0.01), but not in MPO(low) individuals (P = 0.12); here the MPO burden of leucocytes correlated with the degree of vasomotor dysfunction (P = 0.008). To directly test the vasoactive properties of free circulating MPO, the enzyme was injected into the left atrium of anaesthetized, open-chest pigs. Myeloperoxidase plasma levels peaked within minutes and rapidly declined thereafter, reflecting vascular binding of MPO. Blood flow in the left anterior descending artery and the internal mammary artery (IMA) as well as myocardial perfusion decreased following MPO injection when compared with albumin-treated animals (P < 0.001). Isolated IMA-rings from animals subjected to MPO revealed markedly diminished relaxation in response to acetylcholine (P < 0.01) and nitroglycerine as opposed to controls (P < 0.001). CONCLUSION: Myeloperoxidase elicits profound effects on vascular tone of conductance and resistance vessels in vivo. These findings not only call for revisiting the biological functions of leucocytes as systemic and mobile effectors of vascular tone, but also identify MPO as a critical systemic regulator of vasomotion in humans and thus a potential therapeutic target.

Thermal effects of white light illumination during microsurgery: clinical pilot study on the application safety of surgical microscopes.

Modern operating microscopes offer high power illumination to ensure optimal visualization, but can also cause thermal damage. The aim of our study is to quantify the thermal effects in vivo and discuss conditions for safe use. In a pilot study on volunteers, we measured the temperature at the skin surface during microscope illumination, including the influence of anaesthesia and the effects of staining, draping, or moistening of the skin. Irradiation within the limit given by safety regulations (200 mW/cm(2)) results in skin surface temperature of 43 degrees C. Higher intensities (forearm 335 mW/cm(2), back 250 mW/cm(2)) are tolerated, resulting in reversible hyperaemia. At a very high illumination intensity (750 mW/cm(2)), pain occurs within 30 s at temperatures of 46 degrees C+/-1 degrees C (hand and forearm), and 43 degrees C+/-2 degrees C (back), respectively. Anaesthesia has no distinct effect on the temperature, whereas staining and drapes result in much higher temperatures (>100 degrees C). Moistening at practicable flow rates can reduce temperature efficiently when combined with a light absorbing and water absorbent drape. In conclusion, surgeons must be aware that surgical microscope illumination without protective means can cause skin temperatures to rise much above pain threshold, which in our study serves as a (conservative) benchmark for potential damage.

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.

Near-infrared fluorescence coronary angiography: a new noninvasive technology for intraoperative graft patency control.

BACKGROUND: Intraoperative graft patency verification is of major clinical importance for quality control after coronary artery bypass grafting (CABG), especially if surgery is performed on the beating heart. This is one of the first reports of fluorescence coronary angiography (FCA) using the dye indocyanine green (ICG), a noninvasive technology for direct visualization of coronary arteries, bypass grafts, and myocardial perfusion. METHODS: Twenty-three domestic pigs (weight, 45-72 kg) underwent FCA of the left anterior descending coronary artery (LAD). In the first group (n = 6 pigs), FCA was used to visualize the native coronary vessels and myocardial perfusion. In the second group (n = 8 pigs), 14 stenoses of various degrees and 4 total vessel occlusions were created by snares on different segments of the LAD, and FCA was used to visualize the effects of these obstructions. In the third group (n = 9 pigs), a coronary bypass procedure on the beating heart was performed by a left internal mammary artery or a human saphenous vein graft to the LAD, and FCA was used to visualize graft patency. Three pigs were removed from the study because of ventricular fibrillation. ICG was intravenously applied, and the heart was illuminated with near-infrared light emitted by laser diodes. The fluorescence emission was detected by an adapted charge-coupled device camera system. The images were displayed in real time on a high-resolution monitor. Subsequently, images obtained with FCA were compared to those obtained with coronary angiography (n = 10 pigs). RESULTS: In all cases, high-quality FCA images of coronary arteries and myocardial perfusion were obtained. All stenoses resulted in an impairment of the myocardial perfusion visualized by FCA. Occlusion of the LAD or the diagonal branch resulted in a total perfusion defect of the corresponding anterior myocardial wall with immediate reperfusion after releasing the snare. In 5 cases a patent bypass graft with an apparent homogenous perfusion of the corresponding myocardium was detectable. In one procedure, FCA images indicated total occlusion of the bypass graft and a total perfusion deficit in the distal LAD region. Correlation between FCA and coronary angiography in detection of stenoses and graft patency was excellent. CONCLUSION: With the fluorescence technique using ICG, visualization of blood flow in coronary vessels and bypass grafts, as well as of myocardial perfusion, is feasible. FCA is a highly sensitive and reproducible method and an excellent technique for intraoperative quality control in CABG.