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.     

High early patency of saphenous vein graft for coronary artery bypass harvested with surrounding tissue

BACKGROUND: Surgical trauma to the saphenous vein, used as a conduit for coronary artery bypass grafting, affects their occlusion rate. This study evaluates the early patency of saphenous vein grafts harvested with a pedicle of surrounding tissue that protects the vein from spasm and trauma. METHODS: Fifty-two patients underwent coronary artery bypass grafting with saphenous veins harvested with surrounding tissue. Forty-five patients, who received a total of 124 vein grafts and 42 left internal mammary arteries, underwent angiographic follow-up at a mean of 18 months (9 to 24 months). RESULTS: Patency for saphenous vein grafts was 95.4% and for left internal mammary arteries, it was 93.3%. Twenty-nine of 30 (96.7%) vein grafts anastomosed to arteries 2.0 mm or more, 65 of 67 (97%) grafts to 1.5 mm, and 10 of 13 (77%) anastomosed to 1-mm arteries were patent. Nineteen of 22 (86.4%) vein grafts with flow rates 20 mL/min or less, 32 of 34 (94.1%) with flow between 20 and 40 mL/min, and 50 of 51 (98%) with flow more than 40 mL/min were patent. Other registered surgical and clinical factors did not contribute to vessel occlusion. CONCLUSIONS: Early patency rate of saphenous veins harvested with surrounding tissue is very high, even in saphenous vein grafts demonstrating low blood flow. Preservation of graft endothelium using our harvesting technique may be the explanation of this success.     

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.     

Clinical results, graft patency and flow reserve capacity of multiple coronary artery bypass with bilateral or sequential internal thoracic artery grafts

Multiple coronary artery bypass grafting (CABG) was performed utilizing the internal thoracic arteries (ITA) in 87 patients ranging in age from 3 to 76 years. Bilateral ITAs were used in 67, sequential grafting was performed in 16, and the combination of both techniques was applied in 4 patients. Twelve patients had coronary arterial obstructions due to Kawasaki disease (mean age 9.7 +/- 3.3 years) and the remaining 75 patients had atherosclerotic coronary artery disease (mean age 53 +/- 10 years). Triple vessel disease and left main trunk disease occupied 85% of the patients. The number of grafts was 2 to 5 per patient with an average of 3.2 +/- 0.7 per patient. In bilateral ITA grafting, the combination of the RITA to LAD and LITA to LCX was most frequently used, and in sequential grafting, the LITA-diagonal artery-LAD was the most common use. There were no early or late mortalities in the present series. The patency rates for the RITA and LITA were 93% and 96%, respectively, and those of sequential grafting were 100% in both the proximal and distal anastomoses. The clinical outcome of multiple CABG with ITAs was quite satisfactory, and the bilateral ITAs could be used in the very wide range of patient's age from 3 to 76 years. In addition, blood flow reserve provided by bilateral ITAs was equivalent to that of the SVG alone or SVG plus ITA on the basis of the result of coronary sinus flow (CSF) measurements during exercise, and thus complete revascularization of the left ventricle could be accomplished by multiple CABG with ITAs.     

Thermographic evaluation of myocardial cooling and intraoperative control of graft patency in patients with coronary artery disease

Intraoperative thermographic evaluation of regional myocardial cooling induced by cardioplegia, in patients with coronary artery disease, was conducted in 22 cases. Pictures were obtained at the beginning of the cardiopulmonary by-pass, after general cooling and during cardioplegic infusion. Uneven myocardial cooling was observed related to the degree of coronary artery stenosis. After the distal anastomosis of the saphenous vein by-pass graft was completed, injection of cold solution in to the graft showed marked cooling of the dependent myocardium, proving the patency of the graft. In the case of internal mammary artery graft (IMA), after the anastomosis was completed, releasing the bull-dog clamp on the IMA graft, allowed a flow of relatively warm (30 degrees C) blood in the anterolateral wall of the cold (20 degrees C) heart. A warm spot appeared in the thermographic pictures, assessing the patency of the IMA graft. Thermography appears to be a useful tool during myocardial revascularization in order to assess proper myocardial cooling during cardioplegia, and to check intraoperative patency of saphenous vein graft and IMA graft. The use of a special mirror prevents interference with the surgeon's work.     

Evaluation of graft patency during minimally invasive coronary artery bypass grafting with Doppler flow analysis

BACKGROUND: An objective method for determining intraoperative graft patency is an essential part of minimally invasive direct coronary artery bypass. This study compares angiography and Doppler methods for graft analysis during minimally invasive direct coronary artery bypass and presents long-term outcome in a cohort of patients. METHODS: Between March and October 1997, 35 patients had elective minimally invasive direct coronary artery bypass procedures in which the left internal mammary artery was anastomosed to the left anterior descending coronary artery. Immediate graft patency was determined with intraoperative angiography using selective injection of the left internal mammary artery from a femoral approach and with Doppler flow analysis using a 1-mm, 20-MHz Doppler probe placed directly on the graft. RESULTS: There was immediate perfect patency with brisk flow in 91% of patients (32 of 35). A normal Doppler study, defined as a diastolic predominant pattern with a diastolic flow velocity of greater than 15 cm/second, was found in all patients with normal angiograms. All patients with abnormal angiograms also had abnormal Doppler flow. Thus, Doppler analysis was 100% accurate for confirming graft patency and for detecting failed grafts. All abnormal grafts were successfully revised, which allowed 100% early patency. Operative mortality was 2.8% (1 of 35) and there have been no late deaths at a follow-up of more than 2 years. One patient required angioplasty of the anastomosis (1 of 34, 2.9%), but none have required subsequent surgical intervention. CONCLUSIONS: Objective analysis of graft flow in the operating room is necessary to achieve 100% early graft patency with minimally invasive direct coronary artery bypass operations. Doppler analysis is the preferred initial method, because it is safe, accurate, and rapid.     

Comparison of the waveforms of transit-time flowmetry and intraoperative fluorescence imaging for assessing coronary artery bypass graft patency

Purpose  

An intraoperative fluorescence imaging (IFI) system, which can provide visual images, could be the common method for assessing graft patency intraoperatively. We conducted a prospective comparison of the diagnostic accuracy of both the fast Fourier transformation (FFT) analysis of transit-time flowmetry (TTFM) waveform and the IFI system to determine graft failure.     

The impact of competitive flow on distal coronary flow and on graft flow during coronary artery bypass surgery

To determine the impact of left anterior descending-competitive flow (LAD-CF) on distal coronary flow (LAD-DF) and on left internal mammary artery-graft flow (LIMA-GF), we performed a quantitative blood-flow analysis in a swine model of a LIMA-to-LAD coronary artery bypass graft (CABG). In six swine, a LIMA-to-LAD CABG was performed. LAD blood-flow was measured bilaterally to the LIMA-to-LAD anastomosis, in the LIMA and in the pulmonary artery (cardiac output, CO) along with the LIMA pulsatility index (LIMA-PI) and the left ventricular pressure (LVP). PreCABG measurements were followed by postCABG measurements at five levels of LAD-CF: 100%, 75%, 50%, 25% and 0% after gradually snaring down a snare placed proximally of the LAD-CF flow-probe. PreCABG CO and LVP remained unchanged postCABG. LAD-DF was reduced significantly postCABG (-33%, P<0.0001). Reduction of the LAD-CF (at 75%, 50%, 25% and 0%) resulted in significant increase of LIMA-GF (+38%, +63%, +113%, +225%, P<0.036 at all LAD-CF levels), reduced PI (6.8, 5.7, 4.1, 3.1, 2.5) with simultaneous increase of LAD-DF (+8%, P=NS, +8%, P=NS, +17%, P=NS, +50%, P=0.0044). Decreased LAD-CF resulted in increased LAD-DF, increased LIMA-GF and decreased LIMA-PI. To the best of our knowledge, this is the first study where blood-flow was directly and simultaneously measured in all the components of the LIMA-to-LAD anastomosis.     

Long-term left internal mammary artery graft patency for coronary artery disease associated with pseudoxanthoma elasticum

Pseudoxanthoma elasticum (PXE) is a rare, inherited connective tissue disorder with numerous systemic manifestations that include premature coronary artery disease. Coronary artery bypass grafting (CABG) is known to be beneficial in patients with PXE-related coronary artery disease. In these patients, however, the suitability of arterial conduits, including the internal mammary artery, has been controversial. We present a patient with PXE-related coronary artery disease who has had long-term patency of a left internal mammary artery (LIMA) graft after an off-pump CABG procedure in which LIMA and bilateral radial artery conduits were used.     

Experience of perioperative myocardial infarction with graft patency following coronary artery bypass graft surgery

Coronary artery bypass graft surgery, with current operative mortality rates of one to three percent, is now an accepted treatment for coronary artery disease. However, perioperative myocardial infarction (PMI) is not a rare complication of this procedure, and the precise mechanism of its occurrence is not well elucidated. We experienced a case of 70-year-old man who had transmural hemorrhagic PMI in the distribution of the grafted vessel and died due to low output syndrome in spite of vigorous treatment. All five grafts were found to be well patent at autopsy. In this case, the cause of PMI was supposed to be inadequate intraoperative myocardial protection and reperfusion injury.     

Intraoperative transit-time flowmetry in patients undergoing coronary surgery to determine relationships between graft flow and patency and prior coronary interventions and flow demand: a retrospective study

Background

The aim of this study was to delineate impacts of percutaneous coronary intervention (PCI), flow demand, and status of myocardium on graft flow.

Methods

We retrospectively assessed 736 individual coronary artery bypass grafts that had been created as the sole bypass graft for a vascular region in 405 patients. The grafts comprised 334 internal thoracic artery (ITA) to left anterior descending (LAD), 129 ITA and 65 saphenous vein grafts (SVG) to left circumflex (LCX), and 142 gastroepiploic artery (GEA) and 66 SVG to right coronary artery (RCA). Minimal luminal diameter, size of revascularized area, history of myocardial infarction, and PCI in the relevant area were examined to determine whether these factors are associated with flow insufficiency (FI), which was defined as ≤ 20 mL/min.

Results

FI developed in 123/736 grafts (16.7%) and correlated significantly with stenosis in the distal portion (23.0% vs. 12.8%, p?=?0.0003). Prior myocardial infarction significantly correlated with FI in GEA–RCA (p?=?0.002) and ITA–LCX grafts (p?=?0.04). There was a history of PCI to the LAD (PCI group) in 54 ITA to LAD bypass grafts (16.2%), whereas the remaining 280 had no history of PCI to the LAD (no-PCI group). Graft flow was significantly greater in the no-PCI than in the PCI group (53?±?29 vs. 42?±?27; p?=?0.006). The incidences of FI and graft failure were significantly higher in the PCI than the no-PCI group (22.2%, vs. 8.2%; p?=?0.003; 9.2% vs. 1.8%; p?=?0.003, respectively).

Conclusions

Prior PCI has a negative impact on graft flow. The influences of small revascularized area, myocardial infarction, and PCI are greater, necessitating consideration of factors associated with flow demand or microvasculature when planning revascularization.

     

Skeletonized right gastroepiploic artery for coronary artery bypass grafting; evaluation of intraoperative graft flow and postoperative angiographic result

We evaluated the efficacy of using the skeletonized right gastroepiploic artery (RGEA) in coronary artery bypass grafting (CABG). The RGEA was harvested either as a pedicle (group P, n = 14) or in a skeletonized fashion using a Harmonic Scalpel (group S, n = 14). The free flow of the RGEA was too small to be measured in some cases in group P. On the other hand, the free flow of the RGEA could be measured in all cases in group S, and that value obtained was comparable to the free flow of the left internal thoracic artery. The skeletonization of the RGEA also allowed us to directly visualize this vessel, and thus helped us to evaluate the quality of this artery. Postoperatively, all RGEAs were patent in both groups. The RGEA diameters on the postoperative angiography showed the RGEAs in group S to have a wider caliber, however, the differences in the values for each group did not reach statistic significance. Neither the operation time nor the postoperative hospital stay were substantially lengthened due to the skeletonization of the RGEA. In conclusion, the skeletonization of the RGEA using a Harmonic Scalpel is safe and effective modality which enables surgeons to directly visualize arteries in order to determine their quality and thereby making it easier to perform sequential bypass grafting. The method also demonstrated an excellent quality of the patent graft on postoperative angiography. We therefore consider the skeletonization of the RGEA to be a very useful method for harvesting the RGEA in CABG.