Conversion to off-pump coronary bypass without increased morbidity or change in practice

Meta-computational techniques' for managing spare data: An application in off-pump heart surgery

BACKGROUND AND OBJECTIVES

This research looked at the key considerations to remember when selecting a model for working with sparse data. In the presence of sparse evidence, it proposes ideal conditions for conducting meta-analysis.

METHODS

Monte Carlo simulations were used to produce study results, and three forms of continuity correction were used in the research. Besides, meta-analytical approaches were used to measure the cumulative effect of treatment and estimate each method's efficiency. A clinical trial in off-pump surgery met the main objectives of this research. Meta-analysis methods were used to determine the outcome of postoperative risk results. After that, with a total population of 3030, Monte Carlo simulations were used to produce research data to run fixed and random-effect models with three continuity correction forms. The type of consistency adjustment used, group imbalances, statistical analysis used, and variance values between studies all affect meta-analytical methods' results.

RESULTS

MSE values for balanced groups are normally zero. While the Arc-sine variation approach does a decent job of coping with inconsistent results on the effect of treatment, it has concerns with boundary estimates of variance between tests. Furthermore, using continuity correction methods introduces bias and imprecise medication outcome calculations. The spectrum of statistical analysis, such as fixed effects and random effects, can be inferred as completely based on data in samples. The sensitivity analysis of correction decisions could increase the reliability of meta-analysis approaches by enabling researchers to analyze various effect estimation findings.

CONCLUSION

This research study can be expanded upon by identifying alternative approaches to continuity correction methods and resolving boundary estimate problems. The range of statistical analysis, such as fixed effects and random effects, can be entirely dependent on the samples' type of data. The sensitivity analysis of correction decisions could improve the efficiency of meta-analysis methods by allowing researchers to investigate a wide range of effect estimation results.

Two decades of off-pump coronary artery bypass surgery: Harefield experience

The morbidity and mortality associated with conventional coronary artery bypass grafting (CABG) attributed to invasiveness of cardiopulmonary bypass (CPB) has been well documented. Recognition of this invasiveness with a focus centered on abolishing, or at least reducing the CPB associated morbidity and mortality led to the resurgence of off-pump coronary artery bypass (OPCAB) surgery nearly two decades ago. At about the same time, OPCAB was adopted at Harefield hospital partly as an institutional drive to promote innovation and partly as a strategy to improve outcomes. What was deemed as a challenging technique initially and practiced by a single surgeon has now become a valid substitute to conventional CABG for achieving complete myocardial revascularization. This strategy now accounts for more than 50% of all coronary artery surgery operations at Harefield hospital and is systematically used to treat all coronary anatomies; achieve complete revascularization by accessing all territories subtended by main coronary arteries; and accomplish equivalent quality grafts without restriction in vascular conduit usage. This review article provides an overview of the evolution of OPCAB surgery at an institution with a well-established OPCAB program confirming that as surgeons' experience matures, OPCAB surgery permits safe and effective total myocardial revascularization in virtually all patients with multivessel coronary artery disease.

Risk Stratification in Off-Pump Coronary Artery Bypass (OPCAB) Surgery—Role of EuroSCORE II

OBJECTIVES

To evaluate the EuroSCORE II for risk stratification in patients undergoing off-pump coronary artery bypass (OPCAB) surgery.

DESIGN

A retrospective observational study.

SETTING

Two tertiary care hospitals.

PARTICIPANTS

Participants were 1,211 patients undergoing OPCAB surgery.

INTERVENTIONS

No interventions were implemented.

MEASUREMENTS AND MAIN RESULTS

The EuroSCORE II estimated the operative risk for each patient. The calibration of the scoring system was assessed using the Hosmer Lemeshow test, and the discriminative capacity was estimated with area under receiver operating characteristic curves. The incidence, patient characteristics, causes of intraoperative conversion to on-pump coronary artery bypass (ONCAB), and outcome were studied. The all-cause in-hospital mortality was 2.39%. Predicted mortality with the EuroSCORE II was 2.03±1.63. Using the Hosmer Lemeshow test, a C statistic of 8.066 (p = 0.472) was obtained, indicating satisfactory model fit. The calculated area under the receiver operating characteristic curve was 0.706 (p = 0.0002), indicating good discriminatory power. Emergency intraoperative conversion to ONCAB occurred in 6.53% of patients. The mortality in the ONCAB group was significantly higher compared with patients who underwent successful OPCAB surgery (15.18% v 1.5%, p<0.0001). On multiple regression analysis with conversion to ONCAB as the endpoint, associated factors were patients with a higher EuroSCORE II (odds ratio = 1.13, confidence interval = 1.03-1.27) and more-than-trivial mitral regurgitation (odds ratio = 1.84, confidence interval = 1.07-3.06). Net reclassification improvement of 0.714 (p<0.0001) was obtained when on-pump conversion was added to the EuroSCORE II.

CONCLUSIONS

The EuroSCORE II has satisfactory calibration and discrimination power to predict mortality after OPCAB surgery. Intraoperative conversion to ONCAB is a major complication of OPCAB surgery. A higher EuroSCORE II also predicts higher probability of conversion to ONCAB.

Increasing Surgical Experience with Off-Pump Coronary Surgery Does Not Mitigate the Morbidity of Emergency Conversion to Cardiopulmonary Bypass

Objective

Emergency conversion during off-pump coronary artery bypass (OPCAB) confers significant morbidity. We sought to determine whether the outcomes in these patients have changed as our experience with off-pump techniques has increased.

Methods

Between January 1999 and December 2010, 4763 patients underwent coronary artery surgery. An off-pump strategy was attempted in 4415 cases (92.7%). The results of the most recent 50 patients who required emergency conversion were compared with the preceding 50 conversions and with patients who underwent either OPCAB (n = 2737) or on-pump coronary surgery (coronary artery bypass grafting) (n = 268) during the same time frame.

Results

The emergency conversion rate was 2.27% (n = 100), being 2.97% for the first 50 cases and 1.77% for the subsequent 50 patients. The two sequential groups of emergency conversions had similar indications and timing of conversion and comparable outcomes. When compared with patients who underwent OPCAB, the more recent 50 conversions had higher mortality (P = 0.002) and more frequent sternal wound infection (P = 0.036), hemorrhage requiring reoperation (P = 0.003), respiratory failure (P < 0.0001), and all-cause sepsis (P = 0.001). Compared with the on-pump group, the more recent conversions had higher mortality (P = 0.055) and a greater rate of postoperative sepsis (P = 0.002).

Conclusions

The incidence of emergency conversion during OPCAB has decreased with increasing surgical experience; however, the morbidity in these patients remains essentially unchanged. The outcomes in these patients remain worse than those in nonconverted patients. Safer bailout strategies during OPCAB are still warranted.

Predictors of Emergency Conversion to On-Pump during Off-Pump Coronary Surgery

The purpose of this study was to determine predictors and evaluate outcomes of emergency conversion to cardiopulmonary bypass during planned off-pump coronary artery bypass grafting. From January 2001 to November 2005, of 467 consecutive patients aged ≥ 60 years who underwent off-pump coronary surgery, 17 (3.6%) were converted to cardiopulmonary bypass. Those converted to an on-pump technique had significantly higher rates of postoperative cerebrovascular accident (17.6% vs 1.1%), intraaortic balloon pumping (5.9% vs 0%), and red blood cell transfusion (82.4% vs 57.3%), as well as prolonged intensive care unit stay (52.9% vs 25.2%), ventilation time (25% vs 5.3%) and hospital stay (64.7% vs 31.3%) compared to patients whose operation was completed off-pump. Multivariable logistic regression identified left ventricular ejection and left main stenosis as significantly associated with conversion. The rate of emergency conversion to cardiopulmonary bypass during planned off-pump coronary surgery was acceptable, but patients who required conversion had less favorable early outcomes than those who remained off-pump.

Deleterious effects of cardiopulmonary bypass in coronary artery surgery and scientific interpretation of off-pump's logic

Cardiopulmonary bypass (CPB) has been suggested to be a cause of complex systemic inflammatory response that significantly contributes to several adverse postoperative complications. In the last few years, off-pump coronary artery bypass grafting (OPCAB) has gained widespread attention as an alternative technique to conventional on-pump coronary artery bypass grafting (ONCAB). However, a degree of uncertainty regarding the relative merits of ONCAB and OPCAB continues to be a significant issue. Surgeons supporting off-pump surgery, state that the avoidance of the CPB leads to significantly reduced myocardial ischemia-reperfusion injury, postoperative systemic inflammatory response and other biological derangements, a feature that may improve the clinical outcomes. However, perfection in perioperative care, surgical technique and methods of attenuating the untoward effects of CPB has resulted in better clinical outcome of ONCAB as well. Possible reasons of these controversial opinions are that high-quality studies have not comprehensively examined relevant patient outcomes and have enrolled a limited range of patients. Some studies may have been too small to detect clinically important differences in patient outcomes between these two modalities. We present a review of the available scientific interpretation of the literature on OPCAB with regard to safety, hemodynamic changes, inflammation, myocardial preservation and oxidative stress. We also sought to determine from different reported retrospective and randomized control studies, the initial and the long-term benefits of this approach, despite the substantial learning curve associated with OPCAB.

Effect of off-pump coronary artery bypass surgery on clinical, angiographic, neurocognitive, and quality of life outcomes: randomised controlled trial

OBJECTIVE

To compare the clinical, angiographic, neurocognitive, and quality of life outcomes of off-pump coronary artery bypass surgery with conventional coronary artery bypass grafting surgery using cardiopulmonary bypass.

DESIGN

Randomised controlled clinical trial.

SETTING

Tertiary cardiothoracic centre in Middlesex, England.

PARTICIPANTS

168 patients (27 women) requiring primary isolated coronary artery bypass grafting surgery.

INTERVENTIONS

Patients were randomised to conventional coronary artery bypass grafting surgery using cardiopulmonary bypass (n = 84) or off-pump coronary artery bypass surgery (n = 84), carried out by one surgeon. Angiographic examination was carried out at three months postoperatively. Neurocognitive tests were carried out at baseline and at six weeks and six months postoperatively.

MAIN OUTCOME MEASURES

Clinical outcome, graft patency at three months, neurocognitive function at six weeks and six months, and health related quality of life.

RESULTS

Graft patency was evaluated by angiography in 151 (89.9%) patients and was similar between the cardiopulmonary bypass and off-pump groups (risk difference - 1%, 95% confidence interval - 5% to 4%), with the off-pump group considered the treatment group. Patients in the off-pump group required fewer blood transfusions (1.7 units v 1.0 unit, P = 0.02), shorter duration of mechanical ventilation (7.7 hours v 3.9 hours, P = 0.03), and shorter hospital stay (10.8 days v 8.9 days). Scores for neurocognitive function showed a significant difference in three memory subtests at six weeks and two memory subtests at six months in favour of the off-pump group.

CONCLUSIONS

Patients who underwent off-pump coronary artery bypass surgery showed similar patency of grafts, better clinical outcome, shorter hospital stay, and better neurocognitive function than patients who underwent conventional coronary artery bypass grafting surgery using cardiopulmonary bypass.

Coronary artery bypass

Coronary artery bypass grafting as a means of myocardial revascularisation is a remarkably successful operation. Over 25,000 procedures are carried out each year in the UK with an operative mortality of the order of 2% achieved despite an ageing surgical population. Over the last decade, a remarkable increase in the number of patients treated percutaneously by angioplasty and stenting has lead to a levelling off, or even a decline, in the number of patients treated surgically. In an attempt to reduce further the operative morbidity and mortality by excluding that attributable to the extracorporeal circulation, several surgical groups have pioneered performing the procedure without the heart-lung machine (off-pump or OPCAB). Although not a new concept there has been a dramatic increase in its use, lead by the development of sophisticated and disposable devices for stabilising the heart to enable the demanding anastomotic technique required to suture vessels of 1-2 mm often containing degenerative plaque. Concerns remain about the completeness of revascularisation and about the quality of the anastomoses obtained, particularly in the right and circumflex territories which are less accessible than the anterior descending artery. Although some reduction in morbidity has been demonstrated, this has not been as marked as had been hoped. Davies and Wallwork from Papworth argue persuasively and colourfully in favour of the conventional operation and point out the difficulties in designing an appropriate, prospective, randomised,controlled clinical trial because of the apparently small differences in outcome between the two techniques. Amrani and colleagues from Harefield, leading proponents of off-pump surgery using it in virtually 100% of patients undergoing revascularisation, extensively review the comparative literature to date.

Aborted off-pump coronary artery bypass patients have much worse outcomes than on-pump or successful off-pump patients

BACKGROUND

Off-pump coronary artery bypass graft (CABG) surgery is purported to reduce perioperative mortality and morbidity compared with on-pump coronary bypass graft surgery. However, the outcomes of patients for whom an off-pump strategy must be changed to an on-pump procedure during surgery have not been extensively studied.

METHODS AND RESULTS

The Merged Cardiac Registry (Health Data Research, Inc) contains 70 514 isolated CABG performed from January 1998 to March 2004 in 40 facilities. Among them, 62 634 patients begun and completed on-pump bypass (CPB); 7880 patients begun off-pump, of which 7424 (94.2%) completed off-pump coronary artery bypass (OPCAB), whereas 456 (5.8%) were converted to on-pump (CONVERT). CONVERT patients were more severely ill. The observed mortality of CONVERT, CPB, and OPCAB was 9.9%, 3.0%, and 1.6%, respectively, and the observed-to-predicted ratio was 2.77, 1.20, and 0.74, respectively. CONVERT also had more morbidity than either OPCAB or CPB. Finally, a risk model was created to identify patients who might be at risk for conversion from off-pump to on-pump CABG.

CONCLUSIONS

Patients who are intended for an off-pump strategy and then require conversion to on-pump have significantly higher operative mortality and morbidity than either completed OPCAB or CPB patients. In addition, the operative mortality and morbidity are far in excess of that predicted preoperatively. Based on these results, strong consideration should be given for a planned strategy of CPB for those patients with preoperative hemodynamic instability requiring a salvage CABG operation, left ventricular hypertrophy, or previous CABG.

Renal Function After Cardiac Surgery Off- Versus On-Pump Coronary Artery Bypass: Analysis Using the Cockroft-Gault Formula for Estimating Creatinine Clearance

BACKGROUND

Cardiopulmonary bypass (CPB) is often associated with renal dysfunction, as measured by plasma creatinine levels and hemodialysis rates. This study compared creatinine clearance (CrCl), estimated with the Cockroft and Gault formula, between patients undergoing off-pump coronary artery bypass grafting (OPCAB) versus on-pump CABG (on-CAB).

METHODS

Data of 704 consecutive patients were analyzed. Of these patients, 404 underwent OPCAB while 300 had on-CAB. Creatinine clearance, plasma creatinine levels, and clinical outcome were compared between groups. Data between patients who developed new renal impairment, compared to patients with normal postoperative renal function, were also analyzed.

RESULTS

Creatinine clearance (preoperative, 74 +/- 25 vs 78 +/- 29 mL/min; day 1, 74 +/- 26 vs 76 +/- 31 mL/min; day 4, 70 +/- 26 vs 72 +/- 29 mL/min) and creatinine levels (preoperative, 99 +/- 25 vs 95 +/- 27 micromol/L; day 1, 101 +/- 29 vs 104 +/- 35 micromol/L; day 4, 110 +/- 44 vs 113 +/- 60 micromol/L), as well as postoperative complications (stroke 1% vs 1%; hemofiltration 1.5% vs 3.7%; death 1.2% vs 2.3%), were overall similar between OPCAB and on-CAB patients. Patients with preoperative CrCl less than 50 mL/min had higher creatinine levels in the on-CAB group on day 1 (p = 0.026), although CrCl was similar between groups. Development of new CrCl less than 50 mL/min postoperatively was associated with higher rates of intraaortic balloon pump insertion, re-sternotomy, hemofiltration, intensive care and hospital stay, without difference between groups. Female sex, low body mass index, high preoperative creatinine levels, and advanced age were associated with deterioration in CrCl.

CONCLUSIONS

Currently, the rate of renal impairment is low after both OPCAB and on-CAB. No significant difference in CrCl could be demonstrated between groups. Deterioration in renal function is associated with higher rates of postoperative complications.

Comparison of off-pump and on-pump coronary artery bypass grafting in midterm results

OBJECTIVE

Off-pump coronary artery bypass grafting (OPCAB) has become a procedure of choice for surgical treatment of coronary artery disease. Although early advantages of OPCAB were confirmed in comparison with conventional on-pump coronary artery bypass grafting (CABG), late cardiac complications are still controversial. We examined midterm results of OPCAB compared with standard CABG.

METHODS

Between July 1997 and April 2002, 736 consecutive patients who underwent isolated CABG were retrospectively reviewed. The OPCAB group (Group I) comprised 357 patients (49%), and the on-pump CABG group (Group II) 379 patients (51%). Their preoperative, intraoperative, and follow-up data were analyzed.

RESULTS

The mean number of distal anastomoses and the early graft patency were not greatly different between the two groups. The actuarial survival rate at 3 years was not significantly different between Group I (98.3%) and Group II (98.2%) (p = 0.71). The frequency of cardiac events was 4.2%/patient-year in Group I and 2.6%/patient-year in Group II (p = 0.12). The actuarial event free rates were not different between the two groups (p = 0.61). The cardiac event free rates at 3 years were significantly (p = 0.011) higher in patients with complete revascularization (96.7%) than without complete revascularization in Group I (69.2%) and in Group II (92.7% versus 85.9%, p = 0.026).

CONCLUSIONS

Midterm clinical outcome in OPCAB is as good as conventional on-pump CABG. Incomplete revascularization caused cardiac events more frequently than complete revascularization both in OPCAB and on-pump CABG in the intermediate follow-up.

Conversion in off-pump coronary artery bypass grafting: an analysis of predictors and outcomes

BACKGROUND

The incidence, predictive factors, and outcomes related to conversion from off-pump coronary artery bypass (OPCAB) to on-pump coronary artery bypass grafting (ONCAB) have not been well defined. We sought to determine the incidence of conversion, predictive factors, and any associated adverse consequences.

METHODS

From January 2000 through June 2002, 1,644 patients underwent nonemergent OPCAB with 61 patients requiring conversion from OPCAB to ONCAB. These groups were retrospectively compared by univariate and multivariate regression analysis. The converted group was then computer matched 1:3, to a cohort of ONCAB patients to determine differences in outcomes.

RESULTS

The overall conversion rate was 3.71%. Converted patients compared with a computer-matched ONCAB patients had a higher incidence of operative mortality (18.0% versus 2.7%, p < 0.001). Urgently converted patients had a higher incidence of postoperative cardiac arrest (25% versus 1.1%, p < 0.001), multisystem organ failure (10.7% versus 0.6%, p < 0.001), vascular complications (7.1% versus 1.1%, p = 0.03), and perioperative myocardial infarction (10.7% versus 1.1%, p = 0.02). Predictive factors for conversion were surgeon early in OPCAB experience (odds ratio [OR] 4.4), previous CABG (OR 2.8), and congestive heart failure (OR 2.0). The need for urgent-emergent conversion was highly predictive for operative mortality (OR 7.3) compared with elective conversion.

CONCLUSIONS

Patients undergoing urgent-emergent but not elective conversion from OPCAB to ONCAB had a significantly higher risk of mortality and morbidity compared with patients whose procedure was initially ONCAB. Variables predictive of conversion included previous CABG, congestive heart failure, and surgeons early in OPCAB experience.

Off-Pump Coronary Artery Bypass (OPCAB) surgery reduces risk-stratified morbidity and mortality: a United Kingdom Multi-Center Comparative Analysis of Early Clinical Outcome

OBJECTIVE

Off-Pump Coronary Artery Bypass (OPCAB) surgery is gaining more popularity worldwide. The aim of this United Kingdom (UK) multi-center study was to assess the early clinical outcome of the OPCAB technique and perform a risk-stratified comparison with the conventional Coronary Artery Bypass Grafting (CABG) using the Cardio-Pulmonary Bypass (CPB) technique.

METHODS

Data were collected on 5,163 CPB patients from the database of the National Heart and Lung institute, Imperial College, University of London, and on 2,223 OPCAB patients from eight UK cardiac surgical centers, which run established OPCAB surgery programs. All patients had undergone primary isolated CABG for multi-vessel disease through a midline sternotomy approach, between January 1997 and April 2001. Postoperative morbidity and mortality were compared between the CPB and OPCAB patients after adjusting for case-mix. The mortality of the OPCAB patients was also compared, using risk stratification, to the mortality figures reported by the Society of Cardiothoracic Surgeons of Great Britain and Ireland (SCTS) based on 28,018 patients in the national database who were operated on between January 1996 and December 1999.

RESULTS

Morbidity and mortality were significantly lower in the OPCAB patients compared with the CPB patients and the UK national database of CABG patients, over the same period of time, after adjusting for case-mix.

CONCLUSIONS

This study demonstrates that risk stratified morbidity and mortality are significantly lower in OPCAB patients than CPB patients and patients in the UK national database.

Coronary artery bypass grafting without cardiopulmonary bypass: a five-year experience

The current drive to practice less invasive surgery is changing surgical practice towards safer and simpler procedures. The practice of coronary artery bypass grafting (CABG) on a beating heart without cardiopulmonary bypass (CPB), off-pump CABG or OPCAB, has been gaining great attention as an alternative approach to conventional CABG. Since the first adoption of OPCAB in 1997 at our department, 181 patients have undergone OPCAB. OPCAB was indicated for patients who were possibly at risk for CPB, i.e., those who were elderly, who had a history of cerebrovascular disease, whose ascending aorta was severely atherosclerotic with calcification, whose respiratory function was compromised, or whose renal function was compromised. A patient with a concomitant malignant neoplastic disorder was also a candidate for OPCAB because of the possible deleterious effect of CPB on the immune system. More recently, when the coronary anatomy was suitable for OPCAB, even in younger or less risky patients, OPCAB was indicated. The OPCAB procedure was performed through a median sternotomy in 146 patients (80.6%), a left thoracotomy in 27 (14.9%), a subxiphoid approach in 6 and a combined one in 2. One hundred and eleven patients (61.3%) received 1 or 2 grafts (Group I) and 70 (38.7%) received 3 or more grafts (Group II). The number of grafted vessels in Group II patients was 3 to 5 with a mean of 3.44. The mean operative time was 163 minutes in Group I and 209.5 minutes in Group II. The frequency of the use of arterial grafts such as LITA, RITA and RA was significantly higher in Group II than in Group I. Death occurred in 3 patients with acute coronary syndrome who had to undergo urgent surgery. Angiographic examination was performed within 3 months, postoperatively, in 98 patients (54.1%) revealing the overall patency rate of each graft: LITA82/83 (98.8%), RITA 33/33 (100%), GEA 15/16 (93.8%), RA 20/20 (100%), and SVG 15/16 (93.8%). We conclude that, in light of our 5-year experience, off-pump CABG on a beating heart can be safely and effectively performed, with acceptable angiographic results even in patients with multi-vessel coronary disease requiring multiple revascularization. This procedure enables us to perform successful coronary bypass surgery for those who otherwise would not have been candidates for conventional CABG.

Complications related to off-pump bypass grafting

Surgical myocardial revascularization is a technique undergoing critical reevaluation in an attempt to reduce operative morbidity and mortality. As the age and number of comorbidities in the surgical population presenting for bypass increases, improved strategies to lessen operative risk have evolved. The use of off-pump bypass grafting to avoid the detrimental effects of extracorporeal circulation demonstrates great promise in reducing operative complications. However, with new techniques come new challenges. Avoidance of the cardiopulmonary bypass circuit has been linked to the development of a hypercoagulable state postoperatively. Complications related to the unique management of the ascending aorta and target vessels during the performance of beating heart surgery are also being reported. Moreover, despite increasing experience in a number of centers, hemodynamic collapse does occur during off-pump bypass, thereby requiring rapid institution of cardiopulmonary bypass. Continued scientific investigation and research should provide the tools to manage the unique obstacles encountered with off-pump coronary artery bypass.

Mitral annulus distortion during beating heart surgery: a potential cause for hemodynamic disturbance--a three-dimensional echocardiography reconstruction study

BACKGROUND

Positioning for access to the coronary arteries leads to hemodynamic instability during off-pump cardiac surgery. External changes have been well described, but a description of the intracardiac structures in humans has not been described.

METHODS

With multiplane intraoperative echocardiography, the mitral annulus at end diastole was reconstructed in the different positions and correlated with hemodynamic changes in the right heart and left atrium.

RESULTS

Significant distortion of the mitral annulus with enlargement of the left atrium and pulmonary veins was demonstrated, which correlated with high left atrial pressures.

CONCLUSIONS

Mitral valve distortion can significantly contribute to hemodynamic instability during positioning for off-pump cardiac surgery.