Fewer grafts performed in off-pump bypass surgery: patient selection or incomplete revascularization?

Experience, exposure, and attitudes regarding off-pump coronary artery bypass grafting techniques in US cardiothoracic surgical residents: Results of a survey

Background

We sought to determine the current level of exposure to and interest in off-pump coronary artery bypass and beating heart surgery techniques regarding cardiothoracic surgical residents in the United States.

Methods

An email survey consisting of 6 questions was sent to all cardiothoracic surgery residents of approved cardiothoracic training programs in the United States. The survey was emailed using the Qualtrics XM cloud-based survey platform. When the email responses were received, the answers to the survey questions were tabulated by the Qualtrics software and the resident's institution and year of graduation from their residency was noted.

Results

Of 400 surveys sent, we received 99 responses for a response rate of 25%. A total of 78% of cardiothoracic surgery residents reported that they are at programs that do off-pump coronary artery bypass or beating heart surgery infrequently, noting that these cases are done in less than 5% of the coronary artery bypass graftings to which they are exposed. A total of 51% responded that they do not feel comfortable with off-pump coronary artery bypass grafting under any circumstances. A total of 49% reported some comfort with the technique with most of these respondents noting that they would do off-pump coronary artery bypass or beating heart surgery on a selective basis if the clinical situation arose and 4% plan to do off-pump coronary artery bypass routinely. Exposure to off-pump coronary artery bypass and beating heart surgery significantly correlated with future adoption of the technique by the cardiothoracic surgery residents. Cardiothoracic surgery residents in the lowest, middle, and highest terciles of exposure to off-pump coronary artery bypass and beating heart surgery plan to use these techniques 31%, 86%, and 75%, respectively, in selective cases when they are in independent practice.

Conclusions

Over half of graduating cardiothoracic surgery residents do not feel comfortable with off-pump coronary artery bypass or beating heart surgery techniques. Exposure to these techniques in training correlates with comfort level and plans to use them in independent practice.

Off-Pump Coronary Artery Bypass Grafting; is it Still Relevant?

Off-pump Coronary Artery Bypass Grafting (OPCAB) experienced a resurgence in the 1980s -2000s and developed steadily with improvement of the instrumentation and techniques. However questions about graft patency and long-term survival of OPCAB patients still exist. This review attempts to explore the current relevance of OPCAB.

Risk-adjusted analysis of long-term outcomes after on- versus off-pump coronary artery bypass grafting

OBJECTIVES

Recent data suggested that off-pump coronary artery bypass (OPCAB) may carry a higher risk for mortality in the long term when compared to on-pump coronary artery bypass (ONCAB). We, therefore, compared long-term survival and morbidity in patients undergoing ONCAB versus OPCAB in a large single-centre cohort.

METHODS

A total of 8981 patients undergoing isolated elective/urgent coronary artery bypass grafting between January 2009 and December 2019 were analysed. Patients were stratified into 2 groups (OPCAB n = 6649/ONCAB n = 2332). The primary end point was all-cause mortality. Secondary endpoints included repeat revascularization, stroke and myocardial infarction. To adjust for potential selection bias, 1:1 nearest neighbour propensity score (PS) matching was performed resulting in 1857 matched pairs. Moreover, sensitivity analysis was applied in the entire study cohort using multivariable- and PS-adjusted Cox regression analysis.

RESULTS

In the PS-matched cohort, 10-year mortality was similar between study groups [OPCAB 36.4% vs ONCAB 35.8%: hazard ratio (HR) 0.99, 95% confidence interval (CI) 0.87-1.12; P = 0.84]. While 10-year outcomes of secondary endpoints did not differ significantly, risk of stroke (OPCAB 1.50% vs ONCAB 2.8%: HR 0.51, 95% CI 0.32-0.83; P = 0.006) and mortality (OPCAB 3.1% vs ONCAB 4.8%: HR 0.65, 95% CI 0.47-0.91; P = 0.011) at 1 year was lower in the OPCAB group. In the multivariable- and the PS-adjusted model, mortality at 10 years was not significantly different (OPCAB 34.1% vs ONCAB 35.7%: HR 0.97, 95% CI 0.87-1.08; P = 0.59 and HR 1.01, 95% CI 0.90-1.13; P = 0.91, respectively).

CONCLUSIONS

Data do not provide evidence that elective/urgent OPCAB is associated with significantly higher risks of mortality, repeat revascularization, or myocardial infarction during late follow-up when compared to ONCAB. Patients undergoing OPCAB may benefit from reduced risks of stroke and mortality within the first year postoperatively.

Analysis of Myocardial Ischemia Parameters after Coronary Artery Bypass Grafting with Minimal Extracorporeal Circulation and a Novel Microplegia versus Off-Pump Coronary Artery Bypass Grafting

Background

To compare the performance of our institutionally refined microplegia protocol in conjunction with minimal extracorporeal circulation system (MiECC) with off-pump coronary artery bypass grafting (OPCAB).

Methods

We conducted a single center study including patients undergoing isolated CABG surgery performed either off-pump or on-pump using our refined microplegia protocol in conjunction with MiECC. We used propensity modelling to calculate the inverse probability of treatment weights (IPTW). Primary endpoints were peak values of high-sensitivity cardiac troponin T (hs-cTnT) during hospitalization, and respective first values on the first postoperative day. Endpoint analysis was adjusted for intraoperative variables.

Results

After IPTW, we could include 278 patients into our analyses, 153 of which had received OPCAB and 125 of which had received microplegia. Standardized differences indicated that treatment groups were comparable after IPTW. The multivariable quantile regression yielded a nonsignificant median increase of first hs-cTnT by 39 ng/L (95% CI -8 to 87 ng/L, p = 0.11), and of peak hs-cTnT by 35 ng/L (CI -13 to 84, p = 0.11), and of peak hs-cTnT by 35 ng/L (CI -13 to 84, p = 0.11), and of peak hs-cTnT by 35 ng/L (CI -13 to 84, p = 0.11), and of peak hs-cTnT by 35 ng/L (CI -13 to 84.

Conclusion

The use of our institutionally refined microplegia in conjunction with MiECC was associated with similar results with regard to ischemic injury, expressed in hs-cTnT compared to OPCAB. MACCE was seen equally frequent. ICU discharge was earlier if microplegia was used.

On-pump versus off-pump coronary artery bypass graft surgery: what do the evidence show?

The main purpose of the off-pump coronary artery bypass surgery is to reduce morbidity and mortality due cardiopulmonary bypass. However, even though many studies have shown that off-pump coronary artery bypass is feasible and provides hospital morbidity and mortality similar to the on-pump coronary artery bypass graft surgery, probably better in some aspects, its long-term results have been questioned, since some trials have shown reduced survival with off-pump coronary artery bypass. It is likely that incomplete revascularization and/or poor graft patency with off-pump coronary artery bypass probably are responsible for such unfavorable outcome.

Off-pump coronary artery bypass grafting: Misperceptions and misconceptions

Coronary artery bypass grafting (CABG) continues to be one of the most commonly performed cardiac surgical procedures worldwide. Conventional CABG performed on cardiopulmonary bypass termed on-pump CABG is regarded as the gold standard. However, on-pump CABG results in several physiologic derangements including but not limited to thrombocytopenia, activation of complement factors, immune suppression, and inflammatory responses leading to organ dysfunction. Furthermore, manipulating an atherosclerotic ascending aorta during cannulation and cross-clamping can predispose to embolization and stroke risk. Recognition of these detrimental effects of on-pump CABG resulted in resurgence of off-pump CABG nearly two decades ago. Off-pump CABG since its resurgence has been a subject of intensive scrutiny and speculation. Despite numerous retrospective nonrandomized studies, prospective randomized trials, and meta-analyses validating the safety and efficacy of off-pump CABG, opponents of the technique have persistently demanded abandonment of off-pump CABG. Several misconceptions and misperceptions are used as an excuse for such demands. This review article examines published scientific evidence to evaluate these misperceptions and misconceptions about off-pump CABG.

Off-pump coronary artery bypass grafting--the current state

The optimal strategy for coronary revascularization remains controversial. Currently, most surgical revascularizations are performed with the use of cardiopulmonary bypass (ONCAB), yet over the past 20 years off-pump coronary artery bypass grafting (OPCAB) has been increasingly used because of the increased awareness of the deleterious effects of cardiopulmonary bypass (CPB) and aortic manipulation. Small, prospective, randomized controlled trials have lacked sufficient sample size to demonstrate differences in early and long-term outcomes. Larger observational studies that are better powered to statistically compare outcomes have shown more favorable in-hospital outcomes and equivalent long-term outcomes with OPCAB and ONCAB. The benefits of OPCAB techniques may be more apparent for patients at high risk for complications associated with CPB and aortic manipulation. Recent studies have demonstrated improved outcomes in higher-risk patients undergoing OPCAB, as well as improved neurological outcomes. The purpose of this review is to outline the recent literature comparing OPCAB with ONCAB, and to demonstrate efficacy of OPCAB as a useful technique for coronary revascularization.

Complete revascularization is compromised in off-pump coronary artery bypass grafting

OBJECTIVE

Patients who undergo off-pump coronary artery bypass grafting (OPCAB) commonly receive fewer bypass grafts and are more often incompletely revascularized compared with those receiving conventional coronary artery bypass (CCAB) recipients. Because this can compromise survival, we sought to determine whether patients undergoing OPCAB are incompletely revascularized and whether this affects long-term survival and freedom from cardiac events.

METHODS

OPCAB cases (n = 411) performed from January 1, 1997 to June 30, 2003 were considered for inclusion and matching with 874 randomly selected, contemporary CCAB cases. After propensity matching, 308 OPCAB cases and 308 CCAB cases were included in the final analysis. We compared the number of bypass grafts and the completeness of revascularization by coronary territory. Survival and readmission for cardiac causes were monitored for up to 10 years postoperatively, with a median follow-up period of 5.9 years.

RESULTS

On average, the patients undergoing OPCAB received significantly fewer distal anastomoses than did those undergoing CCAB (mean ± standard deviation, 2.6 ± 0.9 vs 3.0 ± 1.0, P < .0001). The circumflex territory was the most likely territory to be ungrafted during OPCAB in patients with angiographically significant obstruction (P = .0006). The frequency of complete revascularization was significantly different between the 2 groups (OPCAB, 79.2% vs CCAB, 88.3%; P = .0.002). The OPCAB group had a significantly greater rate of total arterial grafting (OPCAB, 66.6% vs CCAB, 49.7%; P = .0001). No difference was seen in 8-year survival or freedom from cardiac cause hospital readmission between the 2 groups.

CONCLUSIONS

Despite receiving fewer distal anastomoses and the decreased frequency of complete revascularization, OPCAB and CCAB techniques produced comparable results.

Impact of incomplete surgical revascularization on survival

Complete revascularization is considered superior to incomplete revascularization (IR), with better long-term survival and a lower rate of reintervention. However, it has yet to be established whether this difference is due directly to IR as a surgical strategy or whether this approach is merely a marker of more severe coronary disease and more rapid progression. We believe that IR is a prognostic marker for a more complex coronary pathology, and adverse effects are probably due to the preoperative condition of the patient. In fact, although IR may negatively affect long-term outcomes, it may be, when wisely chosen, the ideal treatment strategy in selected high-risk patients. IR can derive from a surgical strategy of target vessel revascularization, where the impact of surgery is minimized to reduce perioperative mortality and morbidity, aiming to achieve the best feasible safe revascularization.

Off-pump or minimized on-pump coronary surgery--initial experience with Circulating Endothelial Cells (CEC) as a supersensitive marker of tissue damage

BACKGROUND

Off-pump-coronary-artery-bypass-grafting (OPCAB) and minimized-extracorporeal-circulation (Mini-HLM) have been proposed to avoid harmful effects of cardiopulmonary-bypass (CPB). Controversies exist whether OPCAB is still superior in perioperative outcome. Circulating endothelial cells (CEC) are sensitive markers of endothelial damage and are significantly elevated in conventional-CPB-procedures as compared to Mini-HLM-revascularisation. Therefore, CEC might be of specific value in evaluating effectiveness of Mini-HLM and OPCAB as currently applied less-invasive coronary procedures.

METHODS

76 coronary patients were randomly assigned either to OPCAB (n = 34) or to Mini-HLM (ROCsafe™, Terumo Inc., n = 42) procedures. Perioperative data, clinical and serological outcome and measurements of CEC-release and parameters of endothelial function (v.Willebrand-Factor, soluble-thrombomodulin) perioperatively (pre-operative-baseline, post-Mini-HLM/release of OPCAB-stabilizer, 6 h, 12 h, 24 h and 5 days postoperatively) were obtained and compared by ANOVA models including repeated-measures-analysis.

RESULTS

Mean graft-number was 3.06 ± 0.72 in Mini-HLM-patients and 1.89 ± 0.74 in OPCAB-patients (p < 0.001). However, ventilation-, ICU- and total-hospital duration were comparable between groups as well as chest-tube-drainage, transfusion requirements, hemodynamics and catecholaminergic support (p > 0.05). CEC-release did not differ between groups (p = 0.274) and was generally within normal limits, Troponin-T levels where not significanty different (p = 0.108). No myocardial infarctions, strokes or deaths occurred, neuron specific enolase (NSE) did not show any differences between groups (p = 0.194).

CONCLUSION

Conceptional advantages of minimized CPB systems (ROCsafe™) result in morbidity and mortality comparable with OPCAB procedures. Mini-HLM therefore minimizes CPB-related systemic and organ injury as demonstrated by low CEC-values which indicates intact endothelial integrity. Furthermore, Mini-HLM combines OPCAB-benefits with low morbidity in high-risk patients while facilitating more complete revascularization in complex patients.

Miniaturized extracorporeal circulation vs. off-pump coronary artery bypass grafting: What the evidence shows?

Recognition of the potentially deleterious effects of esxtracorporeal circulation led to off-pump coronary artery surgery (OPCAB) experiencing a surge in popularity in the initial decade after its conception. However, OPCAB has its own limitations and technical difficulties, such as coronary access, increased left ventricular size and reduced function, which may lead to the potential for suboptimal revascularization. As an alternative technique, miniaturized extracorporeal circulation (mECC) may provide a more controlled operative field in which the heart may be manipulated whilst minimizing the inflammatory, coagulopathic and haemodilutional effects of cardiopulmonary bypass. In this review, we outline the proposed benefits of the mECC system, discuss the pitfalls associated with mECC, and directly compare mECC to ‘off-pump’ coronary surgery for a variety of clinical and non-clinical outcomes.

Have improvements in myocardial protection influenced a surgeon's choice of coronary artery bypass surgery?

The aim of this study is to determine whether improvements in myocardial protection strategy have influenced the surgeon's choice of coronary artery bypass surgery. Between February 2002 and April 2009, a total of 662 patients underwent coronary artery bypass surgery under the provision of a single consultant surgeon. Operative mortality was defined as in-hospital death and comparison was made based on both the observed and expected mortalities as derived from the logistic EuroSCORE. Of the 662 patients who underwent cardiac surgery, 155 had off-pump whilst 507 had conventional coronary artery bypass surgery. The observed mortalities improved over the years in line with the improvements in myocardial protection strategy despite the increasing risk as predicted by the logistic EuroSCORE, with a reduction in the ratio of observed to expected mortalities of 1.2 in the off-pump group to 0.4 in the conventional group who had better myocardial protection. This has lead to a change in practice being predominantly off-pump at the beginning to that of conventional surgery in the later part of the study. As the case mix of patients gets worse with the increasing severity of multi-vessel disease and poor ventricular function, myocardial protection becomes crucial to the surgeon's preoperative assessment.