Abstract
Introduction
Endoscopic vein harvest is the technique of choice in North America, where it constitutes 80% of conduit harvest for coronary artery bypass grafting. The UK has much lower rates, despite demonstrable perioperative benefits. Concerns about patency and long-term survival are often cited as reasons for poor uptake and evidence in the literature thus far has only addressed mid-term outcomes. We sought to identify the long-term survival of patients undergoing endoscopic vein harvest compared with a contemporaneous cohort of open vein harvest.
Materials and methods
This was a retrospective cohort study of all consecutive patients undergoing isolated coronary artery bypass grafting at a single institution between 2007 and 2017. All-cause long-term mortality was compared using Kaplan–Meier curves and log-rank analysis.
Results
A total of 7,527 patients undergoing coronary artery bypass grafting (1,029 receiving endoscopic vein harvest) were studied. The groups were well matched for preoperative characteristics, except that there were more patients with triple-vessel disease and good left-ventricular function in the endoscopic vein harvest group. There was no statistically significant difference in the long-term survival (p = 0.23). At five years (median follow-up), survival was 86.1% (95% confidence interval 85.3–87.0) in the open vein harvest group compared with 85.5% (95% confidence interval 82.8–88.2) in the endoscopic vein harvest group.
Discussion and conclusion
Endoscopic vein harvest does not affect long-term survival in an unselected population. The contraindications for minimally invasive vein harvest in coronary artery bypass grafting are increasingly diminishing.
Keywords: Coronary artery bypass, Minimally invasive surgical procedure, Survival analysis
Introduction
The incision required to harvest a full length of long saphenous vein for coronary artery bypass grafting is the longest surgical wound in use. Surgical site infections complicate 9% of such incisions,1 together with persistent sensory discomfort (pain, numbness or paraesthesia) in 57%,2 reduced mobility both perioperatively,3 and up to one month in 18% of cases.4 Over 25% of patients cite the saphenectomy wound as a source of lower satisfaction with their overall revascularisation in a national pilot patient-related outcomes measure survey.
Despite the availability of endoscopic vein harvest, introduced nearly two decades ago,5 across the UK there has been slow movement away from traditional open vein harvest methods. The results of a subgroup analysis from the PREVENT IV trial suggested reduced early graft patency in conduits harvested by endoscopic methods,6 and many units responded by cautiously withdrawing their programmes. Subsequent studies, included in a large 2013 meta-analysis have since demonstrated no mid-term effect of endoscopic vein harvest on survival or revascularisation rates at 22 months.7 There are presently no studies on the long-term outcomes following endoscopic vein harvest.
We sought to identify the long-term survival of patients who had undergone endoscopic vein harvest at our institution, compared with a contemporaneous cohort of patients who had received open vein harvest.
Materials and methods
We undertook a retrospective review of a prospectively collected database from August 2007 to August 2016. The start date was selected to coincide with the beginning of our endoscopic vein harvest programme. All data had been ratified by the Society of Cardiothoracic Surgeons of Great Britain and Ireland for national audit purposes. Long-term mortality data were obtained as a patient information request from the Office of National Statistics records as all-cause mortality.
The design was a cohort study of consecutive patients undergoing coronary artery bypass grafting at a single centre. The institutional review board waived the need for patient consent. Inclusion criteria were isolated coronary artery bypass grafting in adult patients who received any non-mammary conduit, including those having off-pump, urgent or emergent surgery and total arterial revascularisation. Patients undergoing concomitant procedures including valve replacements, aortovascular surgery or atrial fibrillation ablation procedures were excluded.
Clinical assessment and surgical planning
All patients presented for surgical revascularisation following angiographic assessment of the coronary arteries. Choice of targets, conduit and precise surgical technique were decided by the operating surgeon depending on availability, clinical assessment and resource availability.
Ultrasound examination of the veins to determine suitability for endoscopic vein harvest was undertaken after induction of anaesthesia. Criteria for endoscopic vein harvest included vein diameter 2–4mm and no evidence of intraluminal thrombus on standard and Doppler views.
Vein harvest techniques
Open vein harvest was performed predominantly by experienced practitioners and surgical trainees under supervision. At the beginning of our experience, a single surgeon alone (author JZ) was performing endoscopic vein harvest; after four years, a surgical care practitioner (author SP) was also trained who then undertook training of other surgical care practitioners. Criteria for completion and certification of training were a minimum of 20 cases consecutive harvest with no complications, conversions or macroscopic vein injury. Endoscopic harvest was performed concurrently with sternotomy and mammary harvest. Two systems were used in parallel, according to operator preference: VirtuoSaph (Terumo Europe NV, Leuven, Belgium) or VASOVIEW (MAQUET Holding BV & Co. KG, Rastatt, Germany).
Following a 2cm ultrasound-guided cutdown at the level of the knee, the long saphenous vein was identified and dissected free. Prior to further manipulation, heparin 2,500 iu was administered systemically to prevent thrombosis during harvest. The conical dissecting tool of the endoscopic vein harvest equipment was used to create a tunnel around the saphenous vein with CO2 insufflation at 2 litres/minute to assist with visualisation. After the saphenous vein was dissected free of the fat anteriorly, posteriorly and laterally, branches were also freed distally. The dissecting rod was then replaced with a harvesting tool to ligate branches prior to removal. A stab incision at the cranial limit of the harvest (always 4–5cm from the saphenofemoral junction) allowed introduction of Roberts forceps and proximal control. The length of the vein was then debranched using the cutting diathermy device, ensuring maximal length of each branch was attained. If multiple lengths of conduit were required, two harvests from each thigh were preferred, although the vein in the lower leg was sometimes also required as a contiguous endoscopic harvest. Only when sufficient length of vein had been scrutinised for quality (calibre, absence of varicosities and no side-branch avulsions) was full dose heparin for cardiopulmonary bypass administered.
Analysis
Data were analysed using R version 3.3.3 for Mac. Demographic data were analysed using the Wilcoxon signed rank test for continuous variables and chi-square for categorical data.
The primary end point of this study was long-term mortality as assessed by the Kaplan–Meier survival curves and log-rank analysis. Patients were grouped according to intention to treat.
Secondary endpoints were inpatient mortality, intensive care unit stay, 12-hour postoperative blood loss, donor blood usage and total hospital stay.
Results
A total of 21,080 patients were identified as having had coronary artery bypass grafting at our institution. Following data cleaning and exclusion of all patients with concomitant surgery, 16,309 patients were available for data analysis. We excluded patients who had received open vein harvest in the time period prior to the endoscopic vein harvest programme starting so that the open harvest cohort was not historically disadvantaged. Some 7,527 patients remained in the dataset for analysis, of whom 1,029 had received endoscopic vein harvest.
Demographics
Preoperative patient characteristics are shown in Table 1. Differences in patient body habitus were statistically although not clinically significant. There was a higher proportion of grade IV angina and dyspnoea in the open vein harvest groups, but patients were otherwise well matched. More patients who had endoscopic vein harvest had triple-vessel coronary disease, but more of those with open vein harvest had impaired left ventricular function.
Table 1.
Preoperative patient characteristics
| Characteristic | OVH (n = 7,527) | EVH (n = 1,029) | p-value |
|---|---|---|---|
| Median age, years [IQR] | 68 [60, 74] | 68 [60, 75] | 0.874 |
| Male (%) | 5923 (78.7) | 814 (79.1) | 0.791 |
| Height/cm, median [IQR] | 171 [165, 177] | 171 [165, 178] | 0.37 |
| Weight/kg, median [IQR] | 81 [71, 91] | 82 [71, 94] | 0.004 |
| Body surface area/m2, median [IQR] | 1.93 [1.79, 2.06] | 1.95 [1.80, 2.08] | 0.008 |
| Body mass index/kg.m-2, median [IQR] | 27.68 [24.97, 30.69] | 27.85 [25.33, 31.42] | 0.007 |
| EuroSCORE [IQR] | 17.0 [15.0, 19.0] | 17.0 [15.0, 19.0] | 0.096 |
| CCS grade IV (%) | 519 (6.9) | 48 (4.7) | 0.006 |
| NYHA class IV (%) | 254 (3.4) | 24 (2.4) | 0.019 |
| Previous myocardial infarction (%) | 3662 (48.7) | 504 (49.0) | 0.097 |
| Interval myocardial infarction (%): | 0.806 | ||
| < 6 hours | 27 (0.4) | 2 (0.2) | |
| 6–24 hours | 28 (0.4) | 6 (0.6) | |
| 1–30 days | 1527 (20.3) | 201 (19.7) | |
| 31–90 days | 521 (6.9) | 75 (7.3) | |
| > 90 days | 1557 (20.7) | 217 (21.3) | |
| Previous PCI (%) | 937 (12.5) | 145 (14.2) | 0.128 |
| Diabetes (%): | 0.187 | ||
| Non-insulin dependent | 1016 (13.5) | 133 (13.0) | |
| Insulin dependent | 428 (5.7) | 69 (6.8) | |
| Smoking history (%): | 0.1 | ||
| Ex-smoker | 4416 (58.7) | 563 (55.2) | |
| Current smoker | 774 (10.3) | 113 (11.1) | |
| Hypertension (%) | 5113 (71.5) | 727 (73.0) | 0.333 |
| Renal impairment (%): | 0.566 | ||
| Chronic | 58 (0.8) | 5 (0.5) | |
| Dialysis dependent | 37 (0.5) | 7 (0.7) | |
| Pulmonary disease (%) | 1119 (14.9) | 148 (14.5) | 0.783 |
| Neurological disease (%): | 0.288 | ||
| CVA full recovery | 209 (2.8) | 36 (3.5) | |
| CVA with residual deficit | 505 (6.7) | 61 (6.0) | |
| Neurological dysfunction (%) | 248 (3.3) | 31 (3.0) | 0.728 |
| Peripheral vascular disease (%) | 1168 (15.5) | 177 (17.3) | 0.15 |
| Sinus rhythm (%) | 6733 (89.5) | 929 (91.0) | 0.324 |
| Triple-vessel disease (%) | 5126 (68.1) | 735 (71.5) | < 0.001 |
| Left main stem disease (%) | 1759 (23.4) | 257 (25.0) | 0.518 |
| LVEF (%) | 0.044 | ||
| Poor (< 30%) | 349 (4.6) | 33 (3.2) | |
| Fair (30–49%) | 1384 (18.4) | 174 (16.9) | |
| Good (> 49%) | 5790 (77.0) | 822 (79.9) | |
| Shock (%) | 58 (0.8) | 3 (0.3) | 0.13 |
CCS, Canadian Cardiovascular Society; CVA, cerebrovascular accident; EVH, endoscopic vein harvesting; IQR, interquartile range; LVEF, left ventricular ejection fraction; NYHA, New York Heart Association; OVH, open vein harvesting PCI, percutaneous coronary intervention;
Surgery and outcomes
Surgical data are presented in Table 2 and demonstrates a higher number of grafts performed in patients undergoing endoscopic vein harvest (mean 3.8 ± 0.8 vs 3.7 ± 1.0, p <0.001) associated with a longer cross-clamp time (median 66 vs 50 minutes, p < 0.001). There was no difference in operative urgency between the two groups.
Table 2.
Intraoperative data
| OVH (n = 7527) | EVH (n = 1029) | p-value | |
|---|---|---|---|
| Grafts (n): | |||
| Median [IQR] | 4.0 [3.0, 4.0] | 4.0 [3.0, 4.0] | < 0.001 |
| Mean (SD) | 3.66 (0.95) | 3.81 (0.79) | < 0.001 |
| Bypass, median minutes [IQR] | 84.0 [55.0, 116.0] | 83.0 [66.75, 107.0] | 0.27 |
| Cross-clamp, median minutes [IQR] | 50.0 [24.0, 78.0] | 66.0 [50.0, 85.0] | < 0.001 |
| Urgency (%): | 0.351 | ||
| Elective | 5438 (72.2) | 759 (73.8) | |
| Urgent | 1956 (26.0) | 258 (25.1) | |
| Salvage | 11 (0.1) | 0 (0.0) | |
| Emergency | 122 (1.6) | 12 (1.2) | |
| OPCAB (%) | 1365 (18.1) | 76 (7.4) | < 0.001 |
EVH, endoscopic vein harvesting; IQR, interquartile range; OPCAB, off-pump coronary artery bypass; OVH, open vein harvesting; SD, standard deviation.
Long-term survival
Follow-up was available up to 10.5 years (median 4.8 years), with no statistically significant difference in the long-term survival between the two groups (Fig 1). Median survival at five years was 86.1% (95% confidence interval, CI, 85.3–87.0) in the open vein harvest group and 85.5% (95% CI 82.8–88.2) in the endoscopic vein harvest group.
Figure 1.
Kaplan-Meier survival curves for open (blue) and endoscopic vein harvest (EVH; red). Shading on curves is 95% confidence intervals and density plots at bottom of graph show censored data.
Secondary outcome measures
A summary of in-hospital outcomes is given in Table 3. There were no statistically significant differences that were also clinically significant.
Table 3.
Postoperative outcomes
| OVH (n = 7527) | EVH (n = 1029) | p-value | |
|---|---|---|---|
| Ventilation time (%): | 0.219 | ||
| < 12 hours | 6767 (90.0) | 927 (90.8) | |
| < 24 hours | 544 (7.2) | 70 (6.9) | |
| > 24 hours | 141 (1.9) | 21 (2.1) | |
| Arrhythmias (%): | 0.082 | ||
| Atrial fibrillation | 1967 (26.2) | 234 (22.9) | |
| Cardiac arrest | 47 (0.6) | 7 (0.7) | |
| Pacemaker | 108 (1.4) | 10 (1.0) | |
| Pulmonary complications (%) | 960 (12.7) | 146 (14.3) | 0.143 |
| Gastrointestinal complication (%) | 161 (2.2) | 27 (2.7) | 0.689 |
| IABP (%) | 143 (1.9) | 15 (1.5) | 0.583 |
| Stroke (%) | 100 (1.3) | 11 (1.1) | 0.606 |
| Inotropic support (%) | 859 (11.4) | 96 (9.4) | 0.062 |
| Acute kidney injury (%) | 336 (4.5) | 50 (4.9) | 0.59 |
| Renal replacement therapy (%) | 113 (1.5) | 24 (2.4) | 0.059 |
| Discharge destination (%): | 0.27 | ||
| Dead | 129 (1.7) | 20 (2.0) | |
| Home | 6861 (91.2) | 928 (90.9) | |
| Convalescence | 214 (2.8) | 38 (3.7) | |
| Other hospital | 315 (4.2) | 35 (3.4) | |
| 12-hour EBL/mL, median [IQR] | 510.0 [360.0, 740.0] | 480.0 [340.0, 680.0] | < 0.001 |
| Donor blood, units, median [IQR] | 0.0 [0.0, 0.0] | 0.0 [0.0, 0.0] | 0.072 |
| Platelets/unit, median [IQR] | 1.0 [1.0, 1.0] | 1.0 [1.0, 1.0] | 0.002 |
| Multi-organ failure (%) | 92 (1.2) | 15 (1.5) | 0.608 |
| In-hospital survival (%) | 7397 (98.3) | 1009 (98.1) | 0.688 |
| Intensive care stay, median [IQR] | 1.0 [1.0, 1.0] | 1.0 [1.0, 1.0] | 0.476 |
| Hospital stay/days, median [IQR] | 6.0 [5.0, 9.0] | 6.0 [5.0, 8.0] | 0.581 |
EBL, estimated blood loss; EVH, endoscopic vein harvesting; IABP, intra-aortic balloon pump; IQR, interquartile range; OVH, open vein harvesting.
Discussion
After Lopes et al raised concerns about the longevity of endoscopically harvested vein conduit using data from the PREVENT IV trial,6 a rebuttal was promptly published from a subgroup of the ROOBY trial.8 Nonetheless, the National Institute for Health and Care Excellence (NICE) examined the available evidence and restricted the practice of endoscopic vein harvest, and issued guidelines recommending that patients were consented for and counselled against the potential issues with endoscopic vein harvest graft patency until further substantial evidence was available to refute the findings of the PREVENT IV subgroup analysis.6,9 We reviewed our initial experience and showed no early survival impact of endoscopic vein harvest, which helped us continue to offer this option to our patients with a close audit of early outcomes.10
We subsequently contributed our patients towards a propensity matched study of 533 patients who had endoscopic vein harvest from the UK National Cardiac Audit Database.11 An equivalent study from the Society of Thoracic Surgeons database of 122,899 patients was also published within three years.12 Both these series found no difference in rates of myocardial infarction, revascularisation or death at three years, and reported a reduced risk of perioperative leg wound infections with endoscopic vein harvest (hazard ratio 0.83, 95% CI 0.77–0.89, p < 0.001).
These studies were included in a large meta-analysis of randomised and observational studies (137,831 endoscopic vein harvest) by Sastry et al in 2013.7 The median follow-up of trials included in the meta-analysis was 22.5 months and demonstrated no increased risk of death in the endoscopic vein harvest group in that time period. Although there was a trend towards increased revascularisation in the endoscopic vein harvest group in that period (standardised risk ratio 1.16, 95% CI 0.99–1.36, p = 0.06), it did not reach statistical significance. In 2014, NICE revised their original position to state that the evidence for the safety and efficacy of endoscopic vein harvest was now adequate to support use of the procedure.13
During the interim period between successive NICE guidelines, patients at our institution were specifically informed when consenting for endoscopic vein harvest of the potential increase in vein graft failure. Our anecdotal experience was that many patients still preferred a less invasive method regardless of potential long-term sequelae. This has also been seen with patient preferences for percutaneous intervention over cardiac surgery, even in multivessel disease when facing mortality risks twice that of surgery or repeat revascularisation requirements that are three times higher.14
To date, this is the largest cohort of long-term outcomes from endoscopic vein harvest in the literature. A Danish group has published the long-term results of their randomised controlled trial, with a median follow-up of 6.3 years, but had only 66 patients in the endoscopic vein harvest group.15 They also found no difference in long-term survival, angina recurrence or myocardial infarction, but were able to demonstrate reduced patency in a sample of the endoscopic vein harvest group at computed tomography coronary angiography.
It is well recognised that in the perioperative period, patients with open saphenectomy harvest wounds have substantially higher pain scores compared with those with endoscopic incisions.7 These lead to reduced patient-reported mobility in the perioperative period.16 A significant difference in pain scores on mobilisation between open vein harvest and endoscopic vein harvest groups may persist up to six weeks.17
There are clear benefits to endoscopic vein harvesting in the perioperative and early recovery phases. Initial concerns about increased early graft failure have been addressed and there appear to be no contraindications to endoscopic vein harvest with respect to long-term survival. For harvest of both long saphenous vein and radial arteries, there is level 1, class A evidence supporting the use of endoscopic vein harvest.18 It is unclear, therefore, why this minimally invasive strategy has not gained popularity in the UK as it has done in North America, where endoscopic vein harvest accounts for 80% of conduit harvest. Mounting evidence in its favour has been overlooked, perhaps because of the investment required in infrastructure and training. The corollary to this is that endoscopic vein harvest may be overall more cost effective than open vein harvest by virtue of capital costs offset by savings in-hospital stay and readmissions with leg wound problems.19 With such strong evidence to support endoscopic vein harvest, and diminishing reasons to resist, it seems increasingly difficult to justify not adopting the technique as the gold standard in the UK.
Limitations
This was a single-centre study with all the limitations of a retrospective cohort design, somewhat mitigated by the availability of prospectively collected data. In our experience, as is seen in other areas of surgery, patient preference for minimal access approaches would make an adequately powered randomised controlled trial very difficult to recruit into. Barnard and Keenan made recommendations for such a trial at the time of the patency controversy and following the NICE edict.20 If studies were not prompted in that climate, it seems unlikely that any large prospective randomised trials on endoscopic vein harvest will be forthcoming in the current era.
We did not perform formal angiography to assess vein graft patency in this study. This pragmatic design will not, therefore, have identified whether grafts had occluded. However, vein graft failure is not associated with increases in angina, myocardial infarction or mortality, and the significance of isolated, asymptomatic graft failure is not known. Grafts to non-significant stenoses are known to occlude due to competitive flow and over-revascularisation itself has been shown to be detrimental.21 Despite the concerns over graft patency among clinicians, our experience is that patients are more concerned about freedom from angina and long-term survival.
Additional questions about the impact of confounders such as the learning curve and differences between endoscopic vein harvesting equipment manufacturers were beyond the scope of the data collected for this paper. A comparison of off-pump and on-pump outcomes from this unit during the same time period was published elsewhere.22
Conclusions
Saphenous vein harvested endoscopically for use as a conduit in coronary artery bypass grafting is of sufficient quality to maintain long-term survival comparable to open vein harvest. The results of large, multicentre national registries will be of importance in the coming years to demonstrate the ongoing longevity of conduits harvested using minimally invasive techniques.
Acknowledgements
We thank Cathy Malpas for her assistance in collecting data for the study.
References
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