How I do it: Endoscope-assisted in situ arterial reconstruction of the lower limb.

Arterial reconstruction with the great saphenous vein is a frequently performed vascular surgery technique for revascularization of chronic limb threatening ischemia. Surgeon variations of the procedure are common and aim to balance patency, limb salvage, complications, hospital resources, and technical feasibility. We describe a minimally invasive revascularization option using endoscope assistance for in situ great saphenous vein-arterial bypass to treat infrainguinal occlusive disease. We highlight patient selection, operating room setup, instrument details, and procedure strategies that facilitate the use of this technique. The development and refinement of minimally invasive techniques for lower extremity arterial bypass are critical to reduce wound complications and improve limb salvage outcomes in patients.

Personalized surgical planning for coronary bypass graft configurations using patient-specific computational modeling to avoid flow competition in arterial grafts.

Objectives: Flow competition between coronary artery bypass grafts (CABG) and native coronary arteries is a significant problem affecting arterial graft patency. The objectives of this study were to compare the predictive hemodynamic flow resulting from various total arterial grafting configurations and to evaluate whether the use of computational fluid dynamics (CFD) models capable of predicting flow can assist surgeons to make better decisions for individual patients by avoiding poorly functioning grafts. Methods: Sixteen cardiac surgeons declared their preferred CABG configuration using bilateral internal mammary and radial arteries for each of 5 patients who had differing degrees of severe triple vessel coronary disease. Surgeons selected both a preferred 'aortic' strategy, with at least one graft arising from the ascending aorta, and a preferred "anaortic" strategy which could be performed as a "no-aortic touch" operation. CT coronary angiograms of the 5 patients were coupled to CFD models using a novel flow solver "COMCAB." Twelve different CABG configurations were compared for each patient of which 4 were "aortic" and 8 were "anaortic." Surgeons then selected their preferred grafting configurations after being shown predictive hemodynamic metrics including functional assessment of stenoses (instantaneous wave-free ratio; fractional flow reserve), transit time flowmetry graft parameters (mean graft flow; pulsatility index) and myocardial perfusion. Results: A total of 87.5% (7/8) of "anaortic" configurations compared to 25% (1/4) of "aortic" configurations led to unsatisfactory grafts in at least 1 of the 5 patients (P = 0.038). The use of the computational models led to a significant decrease in the selection of unsatisfactory grafting configurations when surgeons employed "anaortic" (21.25% (17/80) vs. 1.25% (1/80), P < 0.001) but not "aortic" techniques (5% (4/80) vs. 0% (0/80), P = 0.64). Similarly, there was an increase in the selection of ideal configurations for "anaortic" (6.25% (5/80) vs. 28.75% (23/80), P < 0.001) but not "aortic" techniques (65% (52/80) vs. 61.25% (49/80), P = 0.74). Furthermore, surgeons who planned to use more than one unique "anaortic" configuration across all 5 patients increased (12.5% (2/16) vs. 87.5% (14/16), P<0.001). Conclusions: "COMCAB" is a promising tool to improve personalized surgical planning particularly for CABG configurations involving composite or sequential grafts which are used more frequently in anaortic operations.

A novel transit-time flow metric, diastolic resistance index, detects subcritical anastomotic stenosis in coronary artery bypass grafting.

Objective: Transit time flow measurement (TTFM) can detect critical anastomotic stenosis during coronary artery bypass grafting. However, the identification of subcritical stenosis remains challenging. We hypothesized that diastolic resistance index (DRI), a novel TTFM metric, is more effective in evaluating subcritical stenosis than the currently available TTFM metrics. DRI is used to measure changes in the diastolic versus systolic resistance of distal anastomosis. Methods: A total of 123 coronary bypass anastomoses in 35 patients were prospectively analyzed. During coronary artery bypass grafting, the mean graft flow (Qmean), pulsatility index, and diastolic filling were obtained. DRI was calculated using the intraoperative recordings of TTFM and arterial pressure. Postoperatively, stenosis of anastomoses was categorized into successful (<50%), subcritical (50%-74%), and critical (≥75%) via multidetector computed tomography scan. Results: In total, 93 (76%), 13 (10%), and 17 (14%) anastomoses were graded as successful, subcritical, and critical, respectively. DRI and diastolic filling could distinguish subcritical from successful anastomoses (P < .01 and < .01, respectively), whereas Qmean and pulsatility index could not (P = .12 and .39, respectively). The receiver operating characteristic curves were established to evaluate the diagnostic ability for detecting ≥50% stenosis. In left anterior descending artery grafting (n = 55), DRI had the highest area under the curve (0.91), followed by diastolic filling (0.87), Qmean (0.74), and pulsatility index (0.65). Conclusions: DRI and diastolic filling had a reliable diagnostic ability for detecting ≥50% stenosis during coronary artery bypass grafting. In left anterior descending artery grafting, DRI had a more satisfactory detection capability than other TTFM metrics.

Transit time flow measurement guiding the surgical treatment for anomalous origin of the right coronary artery: A case report.

Anomalous origin of a coronary artery from the opposite sinus of Valsalva (ACAOS) in symptomatic patients is a rare but serious finding whose treatment consists of a surgical correction. The surgical treatment has a level of complexity that could vary from unroofing and ostioplasty to coronary artery bypass grafting. We present our management of a 59-year-old woman presenting with chest pain and dyspnea for right ACAOS with an interarterial route. The right coronary artery (RCA) was bypassed with the right internal thoracic artery. An intraoperative transit time flowmetry (TTFM) showed a competitive flow from the native RCA. RCA proximal ligation site was identified intraoperatively, considering the best mean graft flow (MGF) and the absence of ischemic events. The patient was discharged after a week without adverse events. The 1-year follow-up was uneventful. The intraoperative use of TTFM could guide the surgeon's hand making straightforward the surgical treatment for ACAOS.

Graft flow evaluation with intraoperative transit-time flow measurement in off-pump versus on-pump coronary artery bypass grafting.

Objective: We aimed to compare transit-time flow measurement (TTFM) parameters for on-pump (ONCAB) and off-pump (OPCAB) coronary artery bypass procedures. Methods: The database of the Registry for Quality AssESsmenT with Ultrasound Imaging and TTFM in Cardiac Bypass Surgery (REQUEST) study was retrospectively reviewed. Only single grafts were included (ie, no sequential or Y/T grafts). Primary end points were mean graft flow (MGF), pulsatility index (PI), diastolic fraction (DF), and backflow (BF). Unadjusted and propensity score-matching comparisons were performed. Results: Of 1016 patients in the REQUEST registry, 846 had at least 1 graft for which TTFM was performed. Of these, 512 patients (60.6%) underwent ONCAB and 334 (39.4%) OPCAB procedures. Mean arterial pressure (MAP) during measurements was higher in the OPCAB group. After propensity score-matching, 312 well balanced pairs were left. In these matched patients, MGF was higher for the ONCAB versus the OPCAB group (32 vs 28 mL/min, respectively, for all grafts [P < .001]; 30 vs 27 mL/min for arterial grafts [P = .002]; and 35 vs 31 mL/min for venous grafts [P = .006], respectively). PI was lower in the ONCAB group (2.1 vs 2.3, for all grafts; P < .001). Diastolic fraction was slightly lower in the ONCAB group (65% vs 67.5%; P < .001). The backflow was also lower in the ONCAB group (0.6 vs 1.3; P < .001) with trends similar to MGF and PI for venous and arterial grafts. There were 21 (3.3%) revisions in the OPCAB group and 14 (2.1%) in the ONCAB group (P = .198). Conclusions: ONCAB surgery was associated with higher MGF and lower PI values, especially in venous grafts. Different TTFM cutoff values for ONCAB versus OPCAB surgery might be considered.

In vivo evaluation of a new hybrid graft using retrograde visceral perfusion for thoracoabdominal aortic repair in an animal model.

Objectives: The SPIDER technique for hybrid thoracoabdominal aortic aneurysm repair can avoid thoracotomy and extracorporeal circulation. To improve technical feasibility and safety, the new Thoracoflo graft, consisting of a proximal stent graft connected to a 7-branched abdominal prosthesis, was evaluated in a pig model for technical feasibility testing, before implantation in humans. Methods: Retroperitoneal exposure of the infradiaphragmatic aorta, including visceral and renal arteries, was performed in 7 pigs (75-85 kg). One iliac branch was temporarily attached to the distal aorta to maintain retrograde visceral and antegrade iliac perfusion after deployment of the thoracic stent graft segment (SPIDER technique). The proximal stent-grafted segment was deployed in the thoracic aorta via direct aortic puncture over the wire without fluoroscopy. The graft was deaired before flow via the iliac side branch to the visceral and iliac arteries was established. Visceral, renal, and lumbar arteries were subsequently sutured to the corresponding side branches of the graft. Technical feasibility, operating and clamping time, blood flow, and tissue perfusion in the related organs were evaluated before implantation and after 3 and 6 hours using transit-time flow measurement and fluorescent microspheres. Final angiography or postprocedural computed tomography angiography were performed. Results: Over-the-wire graft deployment was successful in 6 animals without hemodynamic alteration (P = n.s.). In 1 pig, the proximal stent graft section migrated as the guidewire was not removed, as recommended, before release of the proximal fixation wire. Angiography and computed tomography scan confirmed successful graft implantation and transit-time flow measurement confirmed good visceral and iliac blood flow. Fluorescent microspheres confirmed good spinal cord perfusion. Conclusions: Over-the-wire implantation of the Thoracoflo graft using the SPIDER technique is feasible in a pig model. No fluoroscopy was required. For safe implantation, it is mandatory to follow the single steps of implantation.

The use of intraoperative transit time flow measurement can reduce postoperative myocardial injury.

OBJECTIVE: This study investigates the relationship between the use of transit time flow measurement (TTFM) and postoperative myocardial injury in off-pump coronary artery bypass grafting (OPCABG). METHODS: In this retrospective study, we collected basic data from patients hospitalized for OPCABG in the Department of Cardiothoracic Surgery, Changzhou Second People's Hospital Affiliated with Nanjing Medical University. According to the academic research consortium (ARC)-2 definition of significant myocardial injury, we used cardiac troponin I >2380 ng/L as a criterion for significant postoperative myocardial injury. We use logistic regression and forest plots to assess the association of TTFM use with myocardial injury outcomes. RESULTS: One hundred and forty-six patients were included in this study. The overall median age of these patients was 65.05 years, and 32 (21.92%) experienced a postoperative myocardial injury. TTFM was independently associated with the incidence of postoperative myocardial injury (odds ratio = 0.34 [95% confidence interval = 0.15-0.78]; p = .01), and we found similar trends in regression analyses across subgroups of sex, age, number of bridging vessels, hypertension, diabetes mellitus, BMI, and percutaneous coronary revascularization. One hundred and six patients were followed for 1-year vessel permeability, and seven patients (6.6%) were occluded. CONCLUSIONS: The use of TTFM is independently associated with a reduced incidence of postoperative myocardial lesions during off-pump coronary bypass surgery. The TTFM procedure in OPCABG deserves to be actively promoted to reduce the incidence of postoperative myocardial injury.

Transit time flow measurement and outcome in coronary artery bypass grafting for surgeon and trainee.

BACKGROUND: Trainees need to operate under appropriate supervision to become competent. Transit time flow measurement (TTFM) is useful in detecting intraoperative graft failures during coronary artery bypass grafting (CABG). This study aims to compare the intra- and postoperative outcomes, including TTFM, of isolated CABG performed by a single consultant versus trainees and to determine the relationship between the pulsatility index (PI) and postoperative outcomes. METHODS: This retrospective study included 155 isolated CABG cases. Intraoperative outcomes included duration of cardiopulmonary bypass (CPB) and aortic cross-clamp and TTFM for arterial and venous grafts. Postoperative outcomes included common postoperative complications and mortality. The odds ratios of postoperative complications and mortality for arterial and venous grafts with PI ≤3 relative to grafts with PI >3 were determined with multiple logistic regression. RESULTS: The duration of CPB and aortic cross-clamp was significantly shorter in the consultant's group. TTFM for both arterial and venous grafts were similar and no significant differences in postoperative complications and mortality were detected between the two groups. Patients with arterial grafts with PI ≤3 were less likely to require an intra-aortic balloon pump (IABP) or be ventilated for a prolonged period. No significant differences in postoperative outcomes and mortality were detected between venous grafts with PI ≤3 and PI >3. CONCLUSIONS: Trainees can achieve good results in isolated CABG with appropriate case selection. Patients with arterial grafts with PI ≤3 have better postoperative outcomes.

Beyond patency: Functional assessment of adequacy using internal mammary artery grafting to the left anterior descending artery.

INTRODUCTION: Arterial graft physiology influences the long-term outcome of coronary artery bypass grafting (CABG). We studied factors that can affect the overall resistance to flow using internal mammary artery grafting to the left anterior descending artery. METHODS: This was a prospective, nonrandomized observational study of 100 consecutive patients who underwent elective on-pump isolated or combined valve surgery and CABG. Coronary stenoses were assessed using conventional and quantitative coronary angiography assessment. The flow and pulsatility index (PI) of the grafts were assessed by transit-time flowmetry during cardioplegic arrest and at the end of the operation. Fractional polynomials were used to explore linearity, followed by multivariable regression analysis. RESULTS: Univariate analysis demonstrated higher flows at the end of the operation in patients who had higher flows with the cross-clamp on (P < .001), in males (P = .004), in patients with a low PI at the end of the operation (P = .04), and in patients with a larger size of the recipient artery (P = .005). Multivariable regression analysis showed that the graft flow at the end of the operation was significantly associated with the mean flow with the cross-clamp on (P < .001), sex (P = .003), and PI at the end of the operation (P = .003). Concomitant valve surgery did not influence flows. Male patients had 18 mL/min higher flow. CONCLUSIONS: The graft flow at the end of the operation can be determined by the flow with the cross-clamp on, the PI with the cross-clamp off and coronary artery. We reported differences in the graft flows between sexes, and for first the time, we introduced the concepts of "adequate flow" and "resistance-to-forward-flow" for patent coronary grafts.

Influence of coronary territory on flow profiles of saphenous vein grafts.

BACKGROUND: Differing perfusion of the left and right ventricular coronary territory may influence flow-profiles of saphenous vein grafts (SVGs). We compared flow parameters, measured by transit-time flowmetry (TTFM), in left- and right-sided SVGs during coronary artery by-pass grafting (CABG). METHODS: Routine TTFM measurements were obtained in 167 SVGs to the left territory (55%) and 134 SVGs to the right territory (total of 301 SVGs in 207 patients). The four standard TTFM parameters, [mean graft flow (MGF), pulsatility index (PI), percentage diastolic filling (%DF), and percentage backward flow (%BF)] were compared. Differences in flow parameters were also examined according to surgical technique (on- vs. off-pump). RESULTS: No significant difference between coronary territories was found for MGF, PI and %BF. However, a higher %DF was noted in left-sided SVGs in the overall cohort as well as in the on-pump (both p < 0.001) and the off-pump cohorts (p = 0.07). Further, a significantly higher %BF was found in SVGs performed off-pump to the left territory (1.2 ± 2.5 vs. 2.3 ± 3.0, p = 0.023). In a multivariate regression analysis, anastomosing a SVG to the left territory was weakly associated with higher PI (OR = 0.36, p = 0.026) and strongly associated with higher %DF (OR = 5.1, p < 0.001). No significant association was found for MGF, PI, %DF or %BF in either the on-pump nor the off-pump cohorts. CONCLUSIONS: Although statistically significant, the established differences in TTFM parameters between left- and right-sided vein grafts were small and unlikely to be of clinical relevance.

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.

Maximal blood flow acceleration analysis in the early diastolic phase for aortocoronary artery bypass grafts: a new transit-time flow measurement predictor of graft failure following coronary artery bypass grafting.

PURPOSE: Maximal graft flow acceleration (max df/dt) determined using transit-time flowmetry (TTFM) in the diastolic phase was assessed as a potential predictor of graft failure for aortocoronary artery (AC) bypass grafts in coronary artery bypass patients. METHODS: Max df/dt was retrospectively measured in 114 aortocoronary artery bypass grafts. TTFM data were fitted to a 9-polynomial curve, which was derived from the first-derivative curve, to measure max df/dt (9-polynomial max df/dt). Abnormal TTFM was defined as a mean flow of <15 ml/min, a pulsatility index of >5 or a diastolic filling ratio of <50 %. Postoperative assessments were routinely performed by coronary artery angiography (CAG) at 1 year after surgery. RESULTS: Using TTFM, 68 grafts were normal, 4 of which were failing on CAG, and 46 grafts were abnormal, 21 of which were failing on CAG. 9-polynomial max df/dt was significantly lower in abnormal TTFM/failing by the CAG group compared with abnormal TTFM/patent by the CAG group (1.08 ± 0.89 vs. 2.05 ± 1.51 ml/s(2), respectively; P < 0.01, Mann-Whitney U test, Holm adjustment). CONCLUSIONS: TTFM 9-polynomial max df/dt in the early diastolic phase may be a promising predictor of future graft failure for AC bypass grafts, particularly in abnormal TTFM grafts.

Graft flow assessment using a transit time flow meter in fractional flow reserve-guided coronary artery bypass surgery.

OBJECTIVE: To evaluate the relationship between preoperative severity of coronary stenosis occurring with fractional flow reserve (FFR), and the intraoperative bypass graft flow pattern. METHODS: In all, 72 patients were enrolled in this retrospective study. The FFR value of the left anterior descending artery was evaluated, and data on "in situ" bypass grafting from the internal thoracic artery to the left anterior descending artery were assessed. Patients were divided into 3 groups according to preoperative FFR values (Group S: FFR < 0.70; group M: 0.70 ≤ FFR < 0.75; and group N: FFR ≥ 0.75). RESULTS: In groups S, M, and N, respectively, mean graft flow was 24.7 ± 10.6 mL/minute, 19.2 ± 14.0 mL/minute, and 16.0 ± 9.7 mL mL/minute; pulsatility index was 2.35 ± 0.6, 3.02 ± 1.1, and 5.51 ± 8.20; and number of patients with systolic reverse flow was 3 (6.8%), 5 (35.7%), and 4 (28.6%). Significant differences were observed in graft flow (P = .009), pulsatility index (P = .038), and proportion of systolic reverse flow (P = .023) among the 3 groups. In all patients, graft patency was confirmed with intraoperative fluorescence imaging; postoperative graft patency was confirmed with multislice computed tomography or coronary angiography in 69 patients (follow-up interval: 213 days). Early graft failure occurred in 1 patient. CONCLUSIONS: As coronary stenosis severity increased, graft flow increased, pulsatility index decreased, and proportion of patients with systolic reverse flow increased. In mild coronary artery stenosis, the chance of flow competition between the native coronary artery and the bypass graft increased.

The feasibility and applications of non-invasive cardiac output monitoring, thromboelastography and transit-time flow measurement in living-related renal transplantation surgery: results of a prospective pilot observational study.

INTRODUCTION: Delayed graft function (DGF) remains a significant and detrimental postoperative phenomenon following living-related renal allograft transplantation, with a published incidence of up to 15%. Early therapeutic vasodilatory interventions have been shown to improve DGF, and modifications to immunosuppressive regimens may subsequently lessen its impact. This pilot study assesses the potential applicability of perioperative non-invasive cardiac output monitoring (NICOM), transit-time flow monitoring (TTFM) of the transplant renal artery and pre-/perioperative thromboelastography (TEG) in the early prediction of DGF and perioperative complications. METHODS: Ten consecutive living-related renal allograft recipients were studied. Non-invasive cardiac output monitoring commenced immediately following induction of anaesthesia and was maintained throughout the perioperative period. Doppler-based TTFM was performed during natural haemostatic pauses in the transplant surgery: immediately following graft reperfusion and following ureteric implantation. Central venous blood sampling for TEG was performed following induction of anaesthesia and during abdominal closure. RESULTS: A single incidence of DGF was seen within the studied cohort and one intra-operative (thrombotic) complication noted. NICOM confirmed a predictable trend of increased cardiac index (CI) following allograft reperfusion (mean CI - clamped: 3.17 ± 0.29 L/min/m(2), post-reperfusion: 3.50 ± 0.35 L/min/m(2); P < 0.05) mediated by a significant reduction in total peripheral resistance. Reduced TTFM at the point of allograft reperfusion (227 ml/min c.f. mean; 411 ml/min (95% CI: 358 to 465)) was identified in a subject who experienced intra-operative transplant renal artery thrombosis. TEG data exhibited significant reductions in clot lysis (LY30 (%): pre-op: 1.0 (0.29 to 1.71), post reperfusion 0.33 (0.15 to 0.80); P = 0.02) and a trend towards increased clot initiation following allograft reperfusion. CONCLUSIONS: Reduced renal arterial blood flow (falling without the 95% CI of the mean), was able to accurately predict anastomotic complications within this pilot study. TEG data suggest the emergence of a prothrombotic state, of uncertain clinical significance, following allograft reperfusion. Abrogation of characteristic haemodynamic trends, as determined by NICOM, following allograft reperfusion may permit prediction of individuals at risk of DGF. The findings of this pilot study mandate a larger definitive trial to determine the clinical applications and predictive value of these technologies.