Intra-operative conversion is a cause of masked mortality in off-pump coronary artery bypass: a meta-analysis

Two novel nomograms predict 30-day mortality after off-pump coronary artery bypass grafting

Background

With the development of surgical techniques and medical equipment, the mortality rate of off-pump coronary artery bypass grafting (CABG) has been declining year by year, but there is a lack of convenient and accurate predictive models. This study aims to use two nomograms to predict 30-day mortality after off-pump CABG.

Methods

Patients with isolated off-pump CABG from January 2016 to January 2021 were consecutively enrolled. Potential predictive factors were first screened by lasso regression, and then predictive models were constructed by multivariate logistic regression. To earlier identify high-risk patients, two nomograms were constructed for predicting mortality risk before and after surgery.

Results

A total of 1840 patients met the inclusion and exclusion criteria. The 30-day mortality was 3.97 % (73/1840) in this cohort. Multivariate logistic analysis showed that age, BMI<18.5 kg/m2, surgical time, creatinine, LVEF, history of previous stroke, and major adverse intraoperative events (including conversion to cardiopulmonary bypass or implantation of intra-aortic balloon pump) were independently associated with 30-day mortality. Model 1 contained preoperative and intraoperative variables, and the AUC was 0.836 (p < 0.001). The AUC of the K-fold validation was 0.819. Model 2 was only constructed by preoperative information. The AUC was 0.745 (p < 0.001). The AUC of the K-fold validation was 0.729. The predictive power of Model 1 was significantly higher than the SinoScore (DeLong's test p < 0.001).

Conclusions

The two novel nomograms could be conveniently and accurately used to predict the risk of 30-day mortality after isolated off-pump CABG.

Short-Term Results of Ivabradine versus Metoprolol: The Effects on Atrial Fibrillation in Patients Undergoing Off-Pump Coronary Artery Bypass Grafting

INTRODUCTION

Classic coronary artery bypass grafting (CABG) surgery involves diastolic cardiac arrest under cardiopulmonary bypass, while off-pump CABG (OPCABG) has become widespread in recent years.

METHODS

174 patients who underwent OPCABG were included in the study. Patients were divided into two groups. Group I (n=90) received ivabradine and Group M (n=84) received metoprolol before surgery until postoperative day 10. Intraoperative arrhythmias and hypotension were recorded. Postoperative atrial fibrillation (AF) and arrhythmia, mortality and morbidity rates were assessed based on the 30-day postoperative follow-up.

RESULTS

There were no significant differences in the intraoperative amount of inotropic support and red blood cell transfusion between groups (P=0.87 and P=0.31). However, the rates of intraoperative arrhythmias and hypotension were not significantly higher in Group M (P=0.317 and P=0.47). Ventricular tachycardia/ventricular fibrillation (VT/VF) was observed in 2 patients in both groups. Postoperative AF occurred in 7 patients (7.7%) in Group I and in 10 patients (11.9%) in Group M. Although there was a trend towards a higher prevalence of AF in Group M patients, this did not reach statistical significance. In addition, mortality and morbidity rates were comparable between groups.

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.

Comparison of long-term outcomes between off-pump and on-pump coronary artery bypass grafting using Japanese nationwide cardiovascular surgery database

OBJECTIVES

In Japan, off-pump coronary artery bypass (OPCAB) is more common than on-pump coronary artery bypass. Superior early results of OPCAB have been reported; however, long-term results were still unclear. Purpose of this study is to evaluate the clinical outcomes of OPCAB in Japan using Japan Adult Cardiovascular Surgery Database.

METHODS

Between 2008 and 2010, 23,633 patients who underwent isolated coronary artery bypass were reported in database. We selected the cases from the hospital with mean annual coronary surgery volume of more than 50. Among the total of 7724 cases at 41 institutions, 2150 (31.2%) on-pump coronary artery bypass (ONCAB) and 5574 (68.8%) OPCAB cases were included. Propensity score (PS) matching was performed using PS developed from patient characteristics and preoperative factors resulting in 2007 cases matched pairs. Long-term follow-up data on patients' mortality and stroke were collected.

RESULTS

In-hospital mortality was significantly lower in OPCAB (ONCAB 1.1%, OPCAB 0.4% p = 0.01). Stroke was low in OPCAB group (ONCAB 1.7%, OPCAB 0.8%, p = 0.01). There was no statistically significant difference between OPCAB and ONCAB regarding 7-year overall survival (86.1% vs 88.1% respectively), composite outcomes (72.0% vs 73.9% respectively), or cardiac deaths (97.3% vs 97.1% respectively). Subgroup analysis (more than 75 years old) showed a worse trend in OPCAB group. Only in OPCAB group, incomplete revascularization significantly influenced 7-year survival.

CONCLUSIONS

OPCAB is associated with early prognostic benefits; however, it might be less favorable outcomes in the long term when patients are older or with incomplete revascularization.

On-pump beating heart versus conventional on-pump coronary artery bypass grafting on clinical outcomes: a meta-analysis

Background

A hybrid surgery method, on-pump beating heart coronary artery bypass graft (ON-BH CABG), is supposed to be a promising technology for coronary artery revascularization. Here, we conducted a comprehensive meta-analysis of the data derived from published studies on ON-BH CABG and conventional on-pump coronary artery bypass graft (C-CABG) to compare their short-term and long-term clinical outcomes.

Methods

We searched major electronic databases and 24 studies incorporating 6,862 patients (1,847 ON-BH CABG and 5,015 C-CABG) were included eventually, and 9 studies of them were focusing on high-risk patients.

Results

Compared with ON-BH CABG, C-CABG was associated with a higher risk in early mortality [odds ratio (OR), 1.45; 95% confidence interval (CI), 1.09 to 1.93; P=0.01], myocardial infarction (MI) (OR, 2.60; 95% CI, 1.41 to 4.78; P<0.01), low output syndrome (LOS) (OR, 2.56; 95% CI, 1.55 to 4.23; P<0.01), renal failure (OR, 1.84; 95% CI, 1.38 to 2.44; P<0.01). In contrast, there was no significant difference in long-term survival [hazard ratio (HR), 1.08; 95% CI, 0.81 to 1.43; P=0.60]. In systematic analysis of the studies in high-risk patients, ON-BH CABG showed a lower risk in terms of early mortality, intra-aortic balloon pump (IABP) usage, renal failure, hemodialysis, MI and pulmonary complication. No significant difference was observed in the long-term survival between ON-BH CABG and C-CABG.

Conclusions

With experienced and adept surgical team and mature ON-BH technology, ON-BH CABG may reduce the risk of postoperative death and complications in some patients. It might be an attractive alternative for high-risk patient populations.

Beating-heart on-pump coronary artery bypass grafting vs. off-pump coronary artery bypass grafting: a systematic review and meta-analysis

Background

Beating-heart on-pump coronary artery bypass grafting (CABG), otherwise known as BH-ONCAB, can reduce myocardial injury by preserving native coronary blood flow while maintaining hemodynamic stability by the effective support of cardiopulmonary bypass (CPB). This study aimed to identify whether BH-ONCAB confers a survival, mortality, or morbidity benefit over off-pump CABG (OPCAB).

Methods

A systematic literature review identified 18 studies incorporating 5,615 patients (1,548 BH-ONCAB and 4,067 OPCAB cases) who satisfied the inclusion criteria. Outcome measures were meta-analyzed using random-effects modeling. Between-study heterogeneity was investigated through quality assessment and risk of bias analysis.

Results

The results demonstrated comparable early mortality and long-term survival between BH-ONCAB and OPCAB coronary revascularization with no significant statistical differences. The incidences of stroke, renal failure, blood loss, and arrhythmias were significantly higher in patients who underwent BH-ONCAB than patients who underwent OPCAB. However, BH-ONCAB conferred lower rates of incomplete revascularization and greater numbers of distal anastomoses.

Conclusions

BH-ONCAB is a safe and comparable alternative to OPCAB in terms of early mortality and late survival. BH-ONCAB may confer particular advantages in preventing incomplete revascularization and allowing more distal anastomoses compared to OPCAB. However, BH-ONCAB was associated with more postoperative complications due to the use of CPB. Future work should focus on larger matched studies and multicenter randomized controlled trials to optimize our surgical revascularization strategies.

Effect of Hospital and Surgeon Procedure Volumes on the Incidence of Intraoperative Conversion During Off-Pump Coronary Artery Bypass Grafting

Intraoperative conversion to cardiopulmonary bypass with its subsequent high mortality is a major concern associated with off-pump coronary artery bypass grafting (OPCAB). The impact of procedure volume on the incidence of intraoperative conversion, however, is poorly defined. This study therefore evaluated the effect of procedure volume on the incidence of conversion in OPCAB using nationwide data. We analyzed 31,361 patients who underwent primary, nonemergent, isolated OPCAB during 2013-2016 reported in the Japan Cardiovascular Surgery Database. Hospitals (n = 548) and surgeons (n = 1315) were divided into tertile categories (low-, medium-, and high volumes) based on the total number of isolated coronary artery bypass grafting (CABG). Hierarchical logistic regression analysis, including 22 preoperative factors and hospital and surgeon CABG volumes, was used to assess the relation between procedure volume and the risk of conversion due to bleeding/hemodynamic instability. There were 797 (2.5%) intraoperative conversions due to bleeding/hemodynamic instability. Risk-adjusted odds ratios for conversion were significantly lower in some combined hospital/surgeon CABG volume categories than in the reference category. Hospital/surgeon volumes and their odds ratio (95% confidence interval) were as follows: low/low 1.00 (reference); medium/low 0.62 (0.39-0.96); high/low 0.47 (0.27-0.81); high/high 0.58 (0.38-0.89). There was a lower risk of conversion in medium- and high-volume than low-volume hospitals, especially among low-volume surgeons. Procedure volume is associated with the incidence of conversion during OPCAB. Among low-volume surgeons, hospital CABG volume significantly reduces conversion in a volume-dependent manner. These findings will be useful for safety training of OPCAB surgeons.

On-pump beating-heart coronary artery bypass grafting in high-risk patients: A systematic review and meta-analysis

BACKGROUND

Operative technique for surgical myocardial revascularization in high-risk patients remains an argument of debate. On-pump coronary artery bypass graft (CABG) with cardioplegic arrest and off-pump CABG have intrinsic limitations. The hybrid approach of on-pump beating-heart CABG (OPBHC) has been proposed over the years with conflicting results. This systematic review and meta-analysis intends to summarize the contemporary literature.

METHODS

A literature search was conducted through major electronic databases. The systematic review provided a total of 279 articles, of those 17 studies were included in the present study.

RESULTS

Compared with on-pump CABG, OPBHC patients showed a preoperative higher risk profile but had reduced early mortality (risk ratio [RR], 0.59, 95% CI, 0.36-0.97) and reduced postoperative stroke (RR, 0.60, 95% CI, 0.39-0.91). Also, interesting trends towards reduced postoperative intra-aortic balloon pump use (RR, 0.56, 95% CI, 0.31-1.01) and myocardial infarction (RR, 0.48, 95% CI, 0.22-1.07) were observed. Baseline characteristics and postoperative complications were similar between OPBHC and off-pump CABG, but limited data are available. The risk of incomplete revascularization in OPBHC is lower than off-pump CABG (RR, 0.53, 95% CI, 0.33-0.87) but higher than conventional on-pump CABG (RR, 1.71, 95% CI, 1.23-2.39).

CONCLUSION

OPBHC is an effective technique to perform surgical revascularization in high-risk patients as preventing haemodynamic deterioration and guaranteeing adequate end-organ perfusion. OPBHC represents an alternative technique to on-pump and off-pump CABG, in those cases in which complications deriving from cardioplegic arrest or manipulation of the heart are more likely. For these reasons, OPBHC might be useful in patients with recent myocardial infarction or with left ventricular dysfunction.

Conversion during off-pump coronary artery bypass graft surgery: A case-control study

Objectives:

Off pump coronary artery bypass (OPCAB) surgery is carried out as an alternative to conventional coronary artery bypass grafting using cardiopulmonary bypass (CPB). At times ‘conversion’ to CPB may be required to bail out a situation resulting from acute decompensation of the heart. It is reported that such conversion carries significant mortality risk. Since we conduct coronary revascularization by OPCAB technique as the preferred technique, we conducted this study with an aim to identify the markers of adverse outcome during conversion in Indian patients.

Design:

Case control retrospective study.

Setting:

Tertiary referral center.

Participants:

We conducted three thousand two hundred OPAB surgeries in the period between 2013 to16. Ninety patients (3.1%) required conversion to complete the revascularization (Con version group). Twice the number of patients who underwent OPCAB surgery without conver sion were chosen as controls (Control group).

Intervention:

OPCAB surgery

Results:

Mortality in the conversion group was 5.56% in contrast to 0.06% in the controls (P = 0.01). The conversion group had higher left ventricular end diastolic pressure, incidence of endarterectomy, and intra-aortic balloon counter pulsation requirement. Female gender was also predictive of conversion. The total chest drain, duration of ventilation, ICU stay and hospital stay were also higher in the conversion group. Conversion was associated with 9.47 times the odds for mortality.

Conclusion:

Conversion during OPCAB is associated with significantly increased mortality. Female gender, increased left ventricular end diastolic pressure and preoperative requirement of Intra-aortic balloon are markers of increased risk of mortality when converted.

Conversion from Off to On-Pump Coronary Artery Bypass Grafting. Is it Avoidable?

Background

With the emergence of new technologies to stabilize the heart off-pump coronary artery bypass grafting (OPCAB), there is an increasing trend that is being observed throughout the world. In certain circumstances, OPCAB needs to be converted to on-pump CABG (ONCAB). In this study, we aim to identify certain risk factors mandating conversions and their associated short-term outcomes.

Methods

After approval from the institutional ethical review committee and exemption from informed consent, retrospective data of 100 patients meeting the inclusion criteria who underwent OPCAB operations at our institution from August 2018 to July 2019 were included. Preoperative, intraoperative, and postoperative variables were recorded and compared in conversion and non-conversion groups. This study was conducted at the National Institute of Cardiovascular Diseases, Karachi, Pakistan.

Results

A total of 100 patients were included in this study, out of which 82% (82) were male, with age ranging between 18 and 77 years with a mean age of 56.34 ± 8.3 years. In nine of the cases, OPCAB was emergently converted to ONCAB due to arrhythmias. In nine (9%) cases, off-pump CABG was emergently converted to on-pump CABG (ONCAB). Emergent conversion was due to arrhythmias in five cases, due to hypotension during OM graft in two cases, and due to hypotension during ramus graft for the remaining two cases. The emergent conversion was significantly associated with higher New York Heart Association (NYHA) functional classification and comorbid conditions such as chronic obstructive pulmonary disease (COPD).

Conclusion

Emergency conversion from off-pump to OPCAB is the most catastrophic event causing higher morbidity and mortality. Conversion rate was observed to be 9% with arrhythmias being the common cause and patients with higher NYHA status and COPD at baseline were found to be at increased risk of emergency conversion. Considering our results in patients with diagnosed COPD and higher NYHA status, the decision for off-pump CABG should be wisely taken carefully weighing the risks and benefits.

Conversion after off-pump coronary artery bypass grafting: the CORONARY trial experience

Objectives

Emergent and late conversions form OFF-to-ON pump coronary artery bypass grafting (CABG) have been associated with worse outcomes, however, it remains unclear as to which risk factors are associated with conversion and how to prevent them.

Methods

Among 4718 patients who randomly underwent off- or on-pump CABG, the incidence of off-pump to on-pump cross-over, or 'OFF-to-ON conversion', was 7.9% (186/2356). The primary outcome was a composite of death, stroke, myocardial infarction, or new renal failure requiring dialysis. We assessed the risk factors and outcomes of converted patients.

Results

Emergent OFF-to-ON conversions, defined as conversions for hypotension or ischaemia, were required for 3.2% of patients ( n  = 75), while most elective conversions were due to small or intramuscular coronaries ( n  = 83). OFF-to-ON converted patients required increased surgery time, blood transfusions, intensive care unit stay, and presented a higher incidence at 1 year of the composite outcome compared with non-converted off-pump patients (all P < 0.01), especially if the conversion was emergent. Conversely, elective conversions outcomes were no different compared with non-converted off-pump patients ( P  = 0.35). Independent predictors of emergent conversions included higher heart rate or chronic atrial fibrillation, urgent surgery, more grafts planned and surgeon experience with off-pump CABG.

Conclusions

Emergent OFF-to-ON conversion is associated with worse outcomes compared with elective conversion or no conversion. In the presence of risk factors for emergent conversion, an early and elective conversion approach is a judicious strategy.

Intraoperative conversion to on-pump coronary artery bypass grafting is independently associated with higher mortality in patients undergoing off-pump coronary artery bypass grafting: A propensity-matched analysis

Context:

One of the main limitations of off-pump coronary artery bypass grafting (OPCAB) is the occasional need for intraoperative conversion (IOC) to on-pump coronary artery bypass grafting. IOC is associated with a significantly increased risk of mortality and postoperative morbidity. The impact of IOC on outcome cannot be assessed by a randomized control design.

Aims:

The objective of this study was to analyze the incidence, risk factors, and impact of IOC on the outcome in patients undergoing OPCAB.

Settings and Design:

Three tertiary care level hospitals; retrospective observational study.

Subjects and Methods:

This retrospective observational study included 1971 consecutive patients undergoing OPCAB from January 2012 to October 2015 at three tertiary care level hospitals by four surgeons. The incidence, patient characteristics, cause of IOC, and its impact on outcome were studied.

Statistical Analysis Used:

The cohort was divided into two groups according to IOC. Univariate logistic regression was performed to describe the predictors of IOC. Variables that were found to be significant in univariate analysis were introduced into multivariate model, and adjusted odds ratio (OR) was calculated. To further assess the independent effect of IOC on mortality, propensity score matching with a 5:1 ratio of non-IOC to IOC was performed.

Results:

The overall all-cause in-hospital mortality was 2.6%. IOC was needed in 128 (6.49%) patients. The mortality in the IOC group was significantly higher than non-IOC group (21 of 128 [16.4%] vs. 31 of 1843 [1.7%], P = 0.0001). The most common cause for IOC was hemodynamic disturbances during grafting to the obtuse marginal artery (51/128; 40%). On multivariate logistic regression analysis, left main disease, pulmonary hypertension, and mitral regurgitation independently predicted IOC. We obtained a propensity-matched sample of 692 patients (No IOC 570; IOC 122), and IOC had OR of 16.26 (confidence interval 6.3–41; P < 0.0001) for mortality in matched population.

Conclusions:

Emergency IOC increases odds for mortality by 16-fold. Hence, identification of patients at higher risk of IOC may improve the outcome.

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.

On-pump with beating heart or cardioplegic arrest for emergency conversion to cardiopulmonary bypass during off-pump coronary artery bypass

BACKGROUND AND OBJECTIVES

Intraoperative conversion, especially under emergent circumstances during off-pump coronary artery bypass (OPCAB), is associated with a significantly higher rate of hospital mortality. This study compared the clinical early outcomes of patients emergently converting to cardiopulmonary bypass (CPB) with or without cardioplegic arrest and evaluated the efficacy of an on-pump beating heart technique for these critically ill patients.

DESIGN AND SETTING

A retrospective study of patients treated at The First Affiliated Hospital of China Medical University over an 8-year period (2005 to 2013).

PATIENTS AND METHODS

Between January 2005 and September 2013, 104 patients were emergently converted to CPB during OPCAB. In the first 55 patients (53%), the cardioplegic arrest was performed. In the most recent 49 patients (47%), the on-pump beating heart procedure was used without cardioplegic arrest.

RESULTS

There were no significant differences in their baseline clinical characteristics, number of anastomoses performed per patient, and reasons for conversions (P > .05). A significant reduction occurred in the observed mortality between the cardioplegic arrest group and the on-pump beating heart group (25.6% vs 6.1%, P=.008). A statistical difference was found between the cardioplegic arrest group and the on-pump beating heart group in the time of CPB, peak cardiac troponin I, duration of inotropic support, time to extubation, intensive care unit stay, postoperative hospital stay, incidence of new intra-aortic balloon pump support, and pulmonary complications (P < .05). The incidence of blood requirements, postoperative myocardial infarction, new-onset atrial fibrillation, hemodialysis, stroke, infective complications, and resurgery for bleeding were lower in on-pump beating heart group, but the difference did not reach statistical significance (P > .05).

CONCLUSION

The on-pump beating heart technique is the preferred method of emergency conversion to CPB during OPCAB. It has lower postoperative mortality and morbidity than the cardioplegic arrest.