Early outcomes of emergency coronary artery bypass grafting based on institutional technique selection: a single-center retrospective cohort study

Abstract

Background

Emergency coronary artery bypass grafting (CABG) in high-risk patients remains a major perioperative challenge, and surgical strategy is often determined by clinical and anatomical factors rather than randomization. This study aimed to describe early outcomes of emergency CABG within a structured institutional technique selection framework.

Methods

This retrospective cohort study included 59 consecutive patients who underwent emergency isolated CABG between 2004 and 2007. Patients were allocated to on-pump (n = 39) or off-pump (n = 20) CABG according to a predefined institutional algorithm incorporating hemodynamic status, coronary anatomy, and comorbidities. Outcomes are presented descriptively, and between-group comparisons are interpreted in the context of inherent selection bias.

Results

Substantial baseline and procedural differences were observed between groups, reflecting structured technique selection rather than random allocation. Patients undergoing on-pump CABG had more complex coronary anatomy and higher clinical acuity, including all four cardiogenic shock cases and 92.6% of triple-vessel grafting procedures. Longer operative time, increased inotropic support, and longer hospital stay were observed in the on-pump group; CK-MB levels at 1 h were lower in the off-pump group. In-hospital mortality was low and comparable (7.7% vs. 5.0%, p = 1.000). Given the marked selection bias and limited sample size, these findings should be considered descriptive rather than comparative.

Conclusion

In this historical cohort of emergency CABG patients, both on-pump and off-pump techniques were feasible within a structured institutional selection framework. Observed differences in early outcomes likely reflect underlying patient characteristics rather than intrinsic superiority of either technique. These findings highlight the importance of individualized, algorithm-guided decision-making in emergency surgical revascularization.

Introduction

Cardiopulmonary bypass (CPB) with aortic cross-clamping and cardioplegic arrest has long been the standard approach for surgical myocardial revascularization. Although conventional on-pump CABG yields favorable outcomes in elective low-risk patients, this technique is associated with a systemic inflammatory response and potential end-organ effects related to extracorporeal circulation, particularly in high-risk patients requiring emergency intervention [1, 2, 3, 18].

High-risk individuals presenting with acute coronary syndromes, hemodynamic instability, or significantly impaired ventricular function face substantially greater perioperative risk. In these patients, the deleterious effects of CPB and cardioplegic arrest may further compromise already vulnerable myocardium. Nevertheless, emergency revascularization can offer substantial survival benefits, including restoration of blood flow to ischemic and hibernating myocardial tissue with potential improvement of LVEF [4, 5].

Off-pump CABG (OPCAB) was introduced in the 1990s with the aim of avoiding CPB-related morbidity. By maintaining the heart beating throughout the procedure, OPCAB circumvents the systemic inflammatory response associated with extracorporeal circulation. However, OPCAB presents technical challenges in multi-vessel disease, where cardiac displacement during posterior vessel exposure may cause transient hemodynamic compromise [6, 19].

The selection of technique in the emergency setting — where neither randomization nor extensive preoperative optimization is feasible — is guided by institutional experience, surgeon preference, and patient characteristics. Existing literature on this specific question is limited, with most comparative data derived from elective cohorts. To contextualize our study, we conducted a structured review of landmark trials and meta-analyses comparing on-pump and off-pump CABG, including the ROOBY trial, the CORONARY trial, and several large meta-analyses [8, 9, 10, 11, 12, 15, 16, 20]. Based on this evidence and institutional experience, we developed a patient selection algorithm guiding technique assignment.

This study was not designed to establish a causal comparison between on-pump and off-pump techniques, but rather to describe early outcomes within a structured institutional selection strategy in a high-risk emergency cohort. The study presents outcomes of 59 consecutive patients who underwent emergency isolated CABG, with specific attention to the institutional selection framework and its implications for outcome interpretation [13, 14].

Materials and methods

Study design and population

This retrospective single-center cohort study included 59 consecutive patients who underwent emergency isolated CABG at Dr. Siyami Ersek Thoracic and Cardiovascular Surgery Education and Research Hospital (Istanbul, Turkey) between January 2004 and December 2007. The study originates from the author’s specialist surgical thesis (uzmanlık tezi) completed at the same institution in 2007; clinical data and core findings are original and unchanged from the thesis manuscript. The study was conducted in accordance with STROCSS 2025 reporting criteria [17]. At the time of data collection (2004–2007), formal ethics committee review was not a mandatory requirement for retrospective studies at this institution; all procedures were part of routine clinical care, and data were fully anonymised prior to analysis. Individual patient consent was waived accordingly. Patients with previous cardiac surgery and those requiring concomitant cardiac procedures were excluded.

Patients were allocated to on-pump CABG using hypothermic CPB with cardioplegic arrest (Group 1, n = 39) or off-pump CABG (Group 2, n = 20) per a structured institutional algorithm described below.

Technique selection algorithm

Technique assignment was not randomized but followed a deliberate institutional protocol based on clinical, hemodynamic, and anatomical criteria. This intentional selection process introduces a clinically meaningful baseline imbalance that must be considered when interpreting all comparative findings.

On-pump CABG was indicated when any of the following were present: (1) cardiogenic shock (systolic BP < 90 mmHg, cardiac index < 2.0 L/min/m², or requirement for aggressive inotropic support and/or IABP that could not be stabilized preoperatively); [22]. (2) malignant ventricular arrhythmias; (3) poor target vessel quality (diffuse calcification, small caliber, or severe atheromatous involvement on angiography); or (4) young patients under 60 years with multi-vessel disease and low overall surgical risk.

Off-pump CABG was preferred when: (1) CPB was considered particularly high-risk — including patients over 75 years, those with cerebrovascular disease, or those with renal dysfunction (serum creatinine > 3 mg/dL); (2) favorable coronary anatomy permitted an off-pump approach; or (3) hemodynamic instability was successfully controlled with pharmacologic or mechanical support prior to surgery. This framework explains the pronounced difference in triple-vessel grafting rates between groups (92.6% vs. 7.4%). The selection algorithm is summaried in Fig. 1.

Fig. 1.

Institutional technique selection algorithm and summary of early outcomes. Patients were assigned to on-pump or off-pump CABG according to structured clinical, hemodynamic, and anatomical criteria. Key outcome metrics for each group are shown. CPB = cardiopulmonary bypass; SBP = systolic blood pressure; LVEF = left ventricular ejection fraction

Preoperative assessment

Preoperative evaluation included clinical history, physical examination, 12-lead ECG, chest radiography, transthoracic echocardiography, and coronary angiography. Recorded variables included: age, sex, BMI, hypertension, diabetes mellitus, prior percutaneous coronary intervention, EuroSCORE (additive model), LVEF, hemodynamic status, and coronary anatomy. Left main coronary artery (LMCA) disease was present in 25 patients (42.4%), LAD disease in 47 (79.7%), and RCA disease in 33 (55.9%).

Surgical technique

All procedures were performed via median sternotomy. The left internal mammary artery (LIMA) was used as the primary conduit for LAD revascularization; saphenous vein grafts were used for additional targets. For on-pump cases, CPB was established using roller pump and membrane oxygenator; patients were cooled to 28 °C, which represented the institutional standard for all on-pump cases during this period, including elective procedures, and was not specific to the emergency setting. Myocardial protection was achieved with intermittent antegrade cold blood cardioplegia supplemented by topical cooling; retrograde cardioplegia was not routinely used at this institution during the study period, as the protocol relied on antegrade delivery supplemented by topical cooling to achieve adequate arrest in the setting of ongoing ischemia. For off-pump cases, mechanical stabilization used suction-based tissue stabilizers (Octopus IV, Medtronic; or Estech system). Heparin was administered to maintain ACT above 250 s.

Outcome definitions

Primary outcomes included: total operative time; mechanical ventilation duration; ICU and total hospital stay; postoperative CK-MB (measured at 1 h postoperatively by antibody inhibition method, Hitachi 704 Analyzer); inotropic support requirement; IABP use; revision for bleeding; postoperative complications; and in-hospital mortality. Follow-up was limited to the in-hospital period.

Statistical analysis

Statistical analyses were performed using SPSS version 13.0. Continuous variables are expressed as mean ± standard deviation (SD). Normality was assessed visually using Q-Q plots; variables deviating from normality were analyzed with the Mann-Whitney U test, and normally distributed variables with Student’s independent t-test. Categorical variables were analyzed using chi-square or Fisher’s exact test as appropriate. Two-tailed p < 0.05 was considered statistically significant. Mean differences with 95% confidence intervals (CI) are reported for key continuous outcomes. To quantify baseline imbalance, standardized mean differences (SMD) were calculated for all Table 1 variables; SMD > 0.20 was considered a clinically meaningful difference. Given the limited sample size, no multivariable or propensity score analysis was performed. A post-hoc power calculation for the primary mortality outcome (7.7% vs. 5.0%, α = 0.05, two-sided) indicated a power of less than 10% for this comparison, confirming that all comparative analyses should be considered exploratory and hypothesis-generating only.

Table 1.

Baseline Demographic and Clinical Characteristics

Variable	On-Pump (n = 39)	Off-Pump (n = 20)	p-value
Age (years), mean ± SD	61.35 ± 11.58	64.45 ± 8.99	0.302
Male sex, n (%)	26 (66.7%)	14 (70.0%)	0.795
BMI (kg/m²), mean ± SD	26.86 ± 4.75	28.13 ± 3.77	0.304
Hypertension, n (%)	22 (56.4%)	7 (35.0%)	0.119
Diabetes mellitus, n (%)	12 (30.8%)	3 (15.0%)	0.188
Prior PCI, n (%)	7 (17.9%)	2 (10.0%)	0.421
EuroSCORE, mean ± SD	6.17 ± 2.48	6.10 ± 1.85	0.908
LVEF (%), mean ± SD	27 ± 8	28 ± 9	0.543
Cardiogenic shock on admission, n (%)	4 (10.3%)	0 (0%)	0.149
Intubated on admission, n (%)	4 (10.3%)	2 (10.0%)	1.000

BMI, body mass index; LVEF, left ventricular ejection fraction; PCI, percutaneous coronary intervention; SD, standard deviation; SMD, standardized mean difference. Fisher’s exact test used for cardiogenic shock and intubation status. SMD values (absolute): Age 0.30; Male sex 0.07; BMI 0.30; Hypertension 0.44; Diabetes mellitus 0.38; Prior PCI 0.23; EuroSCORE 0.03; LVEF 0.12; Cardiogenic shock 0.48; Intubated on admission 0.01. SMD > 0.20 indicates a potentially meaningful imbalance; values for hypertension, diabetes, prior PCI, and cardiogenic shock confirm clinically relevant group differences consistent with the structured selection algorithm

Results

Patient characteristics

A total of 59 patients underwent emergency isolated CABG: 39 (66.1%) on-pump and 20 (33.9%) off-pump. Mean age was 62.4 ± 10.8 years (range 39–84), with 40 males (67.8%). Six patients were intubated on admission and four met criteria for cardiogenic shock; all cardiogenic shock patients were assigned to on-pump CABG per protocol. Baseline characteristics are presented in Table 1. Although no statistically significant differences were observed in conventional baseline variables, clinically meaningful differences in disease severity and surgical indication were present between groups, as reflected by the structured selection criteria and standardized mean differences (SMD) shown in Table 1. These imbalances must be considered primary determinants of all between-group outcome differences.

Operative and postoperative variables

Operative and early postoperative data are summarized in Table 2. Total operative time was significantly longer in the on-pump group (250.3 ± 51.1 min vs. 201.7 ± 30.7 min; mean difference 48.6 min, 95% CI 20.9–76.3; p = 0.001). Hospital stay was significantly longer in the on-pump group (9.89 ± 5.43 days vs. 6.85 ± 2.75 days; mean difference 3.04 days, 95% CI 0.98–5.10; p = 0.004). ICU stay, mechanical ventilation duration, and chest tube drainage did not differ significantly between groups.

Table 2.

Operative and Postoperative Variables

Variable	On-Pump (n = 39)	Off-Pump (n = 20)	p-value
Total operative time (min), mean ± SD	250.3 ± 51.1	201.7 ± 30.7	0.001**
CPB time (min), mean ± SD	119.7 ± 42.1	N/A	—
Aortic cross-clamp time (min), mean ± SD	79.3 ± 31.6	N/A	—
Mechanical ventilation (hours), mean ± SD	11.46 ± 5.08	13.00 ± 12.12	0.617
ICU stay (days), mean ± SD	2.02 ± 1.67	1.60 ± 1.39	0.304
Hospital stay (days), mean ± SD	9.89 ± 5.43	6.85 ± 2.75	0.004**
Chest tube drainage (mL), mean ± SD	947.4 ± 314.3	1095.0 ± 514.3	0.177

CPB, cardiopulmonary bypass; ICU, intensive care unit; SD, standard deviation. CPB and cross-clamp times applicable to on-pump group only. **p < 0.01

Graft Distribution

Graft distribution is shown in Table 3; Fig. 2. Complete revascularization was defined as grafting of all angiographically significant stenoses (> 70% luminal narrowing) in vessels with diameter ≥ 1.5 mm that were deemed technically graftable. Triple-vessel grafting was performed in 25 on-pump patients (64.1% of the on-pump group) and only 2 off-pump patients (10.0% of the off-pump group), a highly significant difference (p < 0.001) that reflects the institutional selection algorithm. RCA grafting was more frequent in the on-pump group (66.7% vs. 35.0%; p = 0.020). Complete revascularization was achieved in 89.7% of on-pump and 85.0% of off-pump patients (p = 0.679).

Table 3.

Graft Distribution and Coronary Target Vessels

Variable	On-Pump (n = 39)	Off-Pump (n = 20)	p-value
Number of grafts (overall)			0.001**
Single (1 graft)	5 (12.8%)	8 (40.0%)
Double (2 grafts)	8 (20.5%)	10 (50.0%)
Triple (3 grafts)	25 (64.1%)	2 (10.0%)
Quadruple (4 grafts)	1 (2.6%)	0 (0%)
Target vessel — LMCA	19 (48.7%)	6 (30.0%)	0.168
Target vessel — LAD	31 (79.5%)	16 (80.0%)	0.963
Target vessel — RCA	26 (66.7%)	7 (35.0%)	0.020*
Target vessel — Circumflex	14 (35.9%)	5 (25.0%)	0.396
Complete revascularization, n (%)	35 (89.7%)	17 (85.0%)	0.679
Incomplete revascularization, n (%)	4 (10.3%)	3 (15.0%)	0.679

LMCA, left main coronary artery; LAD, left anterior descending artery; RCA, right coronary artery; CX, circumflex artery. Percentages represent proportions within each group (column percentages). Chi-square test used; Fisher’s exact for cells with expected count < 5. *p < 0.05, **p < 0.01

Fig. 2.

Descriptive presentation of early postoperative outcomes in on-pump and off-pump CABG groups. Panel A: continuous operative and recovery variables (mean ± SD). Panel B: perioperative CK-MB levels. Panel C: incidence of clinical events. *p < 0.05; **p < 0.01. CK-MB = creatine kinase myocardial band; SD = standard deviation; CABG = coronary artery bypass grafting

Postoperative outcomes

Postoperative outcomes are presented in Table 4; Fig. 3. Postoperative CK-MB at 1 h was significantly higher in the on-pump group (38.94 ± 18.52 vs. 28.15 ± 15.57 U/L; mean difference 10.79 U/L, 95% CI 1.05–20.53; p = 0.030). Preoperative CK-MB levels did not differ (p = 0.547), indicating comparable baseline myocardial injury. Inotropic support was required more frequently in the on-pump group (51.3% vs. 15.0%; p = 0.007). In-hospital mortality was 3/39 (7.7%) in the on-pump group and 1/20 (5.0%) in the off-pump group (p = 1.000).

Table 4.

Postoperative Clinical Outcomes

Variable	On-Pump (n = 39)	Off-Pump (n = 20)	p-value
Preoperative CK-MB (U/L), mean ± SD	34.84 ± 26.42	30.65 ± 22.56	0.547
Postoperative CK-MB at 1 h (U/L), mean ± SD	38.94 ± 18.52	28.15 ± 15.57	0.030*
Inotropic support required, n (%)	20 (51.3%)	3 (15.0%)	0.007**
IABP use, n (%)	4 (10.3%)	2 (10.0%)	1.000
Revision for bleeding, n (%)	6 (15.4%)	1 (5.0%)	0.404
Any postoperative complication, n (%)	12 (30.8%)	4 (20.0%)	0.378
Arrhythmia, n (%)	6 (15.4%)	2 (10.0%)	0.706
Renal dysfunction, n (%)	3 (7.7%)	1 (5.0%)	1.000
Sternal wound complication, n (%)	2 (5.1%)	1 (5.0%)	1.000
Gastrointestinal complication, n (%)	1 (2.6%)	0 (0%)	1.000
In-hospital mortality, n (%)	3 (7.7%)	1 (5.0%)	1.000

CK-MB, creatine kinase myocardial band; IABP, intra-aortic balloon pump. Fisher’s exact test used for all categorical comparisons. *p < 0.05, **p < 0.01

Fig. 3.

Graft number distribution (Panel A) and target vessel rates by group (Panel B). Panel A: stacked bar chart showing proportional graft number distribution within each group. Panel B: percentage of patients in each group undergoing grafting to each target vessel. LMCA = left main coronary artery; LAD = left anterior descending artery; RCA = right coronary artery; CX = circumflex artery. *p < 0.05

Discussion

This retrospective cohort study describes early outcomes of on-pump and off-pump CABG in 59 high-risk emergency patients treated within a structured institutional selection framework. The main finding is that both techniques can be performed with acceptable early outcomes in the emergency setting, with in-hospital mortality of 7.7% (on-pump) and 5.0% (off-pump) — a non-significant difference (p = 1.000) consistent with the prior literature on emergency revascularization [1, 2, 21]. Critically, the observed differences between groups are most likely driven by baseline risk imbalance rather than technique-related effects, and no causal inference can be drawn regarding superiority of either surgical approach.

The differences observed between the groups are most likely driven by the baseline clinical characteristics that guided technique selection, rather than by any intrinsic effect of the surgical approach itself. Critically, the on-pump group contained all four cardiogenic shock cases, a substantially higher proportion of triple-vessel disease (64.1% vs. 10.0%), and more RCA involvement — characteristics that independently predict worse outcomes regardless of technique. This structured selection bias must be acknowledged as the primary determinant of the between-group differences observed, and the findings should not be interpreted as evidence of superiority of one technique over the other.

The higher rate of inotropic support in the on-pump group (51.3% vs. 15.0%; p = 0.007) is consistent with the more severely compromised cardiac function in patients selected for on-pump technique, including all four cardiogenic shock cases. This difference should not be interpreted as a technique effect; it is entirely consistent with the baseline risk imbalance inherent to the selection algorithm. Similarly, elevated postoperative CK-MB in the on-pump group (38.94 vs. 28.15 U/L; p = 0.030), despite comparable preoperative levels, may reflect both greater operative complexity and the more severe underlying myocardial status of patients assigned to on-pump CABG, rather than a direct consequence of cardiopulmonary bypass per se. Furthermore, CK-MB measurement at a single early postoperative time point (1 h) reflects historical practice and should be interpreted with caution in light of contemporary biomarker standards, which rely on serial troponin measurements.

The shorter hospital stay in the off-pump group (6.85 vs. 9.89 days; p = 0.004) cannot be interpreted as evidence of faster recovery attributable to off-pump surgery alone. Given the profound differences in patient severity and operative indication between groups, this finding is entirely consistent with the baseline risk imbalance rather than a technique advantage. The absence of long-term follow-up in the present study also precludes conclusions regarding graft patency or survival — domains where arterial graft selection and on-pump surgery may confer advantages in complex multi-vessel disease [7, 8, 9].

Emergency CABG represents a particularly challenging clinical scenario. A recent systematic review and meta-analysis of emergency CABG outcomes [21] reported in-hospital mortality rates of 5–15%, consistent with the present cohort. The absence of a significant mortality difference between groups, despite substantially greater baseline complexity in the on-pump group, underscores the importance of structured patient selection and institutional expertise in achieving acceptable outcomes with both techniques [23].

This study contributes a transparent, real-world description of emergency CABG decision-making within a structured institutional selection framework. The findings demonstrate that both on-pump and off-pump techniques are feasible under algorithm-guided selection, and that structured criteria can achieve acceptable outcomes in this challenging high-risk population. The dataset, while historical, provides a well-documented account of institutional practice during a period predating modern stabilizer technology and trial-informed selection, offering a reference point for the evolution of emergency revascularization decision-making.

This study has several important limitations. First, the retrospective and non-randomized design with structured technique selection introduces meaningful confounding that cannot be fully adjusted for given the sample size constraints. Second, the cohort of 59 patients limits statistical power, particularly for low-frequency binary outcomes; all binary comparisons should be considered exploratory. Third, CK-MB was measured at a single early postoperative time point (1 h), which may not capture the full myocardial injury profile. Fourth, the study covers a period approximately 20 years ago; findings may not fully reflect outcomes achievable with contemporary techniques. Fifth, no long-term follow-up data were collected; all outcome data are limited to the in-hospital period. Sixth, the study originates from the author’s specialist surgical thesis; clinical data and core findings are unchanged from the original thesis. Accordingly, these findings should be interpreted as reflecting real-world, algorithm-based clinical decision-making rather than a direct comparison of the inherent superiority of the two techniques.

Conclusion

In this historical cohort of high-risk patients undergoing emergency CABG, both on-pump and off-pump techniques were feasible and associated with acceptable early outcomes within a structured institutional selection framework. This study should be interpreted as a descriptive analysis of real-world, algorithm-based clinical decision-making rather than a comparative effectiveness study. Apparent differences in early outcomes — including operative time, inotropic support, CK-MB levels, and hospital stay — are likely attributable to patient selection rather than intrinsic procedural advantages of either technique. On-pump CABG was used in patients requiring more extensive multi-vessel revascularization and in those with hemodynamic instability or complex coronary anatomy. In-hospital mortality did not differ significantly between groups. Individualized, algorithm-guided technique selection — accounting for hemodynamics, anatomy, and institutional expertise — appears to be the most clinically appropriate approach in the emergency setting. Prospective randomized trials with long-term follow-up are needed to definitively establish the comparative merits of each technique in emergency CABG.

Author contributions

The sole author was responsible for study conception, design, data collection, statistical analysis, manuscript drafting, and final approval.

Funding

This research received no external funding.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval

This study is based on retrospective clinical data collected between 2004 and 2007. At the time of data collection, formal ethics committee approval was not routinely required for retrospective clinical studies at the institution. The study was conducted in accordance with the principles of the Declaration of Helsinki. All data were fully anonymized prior to analysis, and no patient-identifiable information was used. Given the retrospective design and anonymized data, the requirement for individual informed consent was waived.

AI Assistance Disclosure

All scientific content, clinical data, statistical analyses, interpretations, and conclusions are solely the author’s own work.

Author's Note on publication history

This manuscript is based on the author's specialist surgical thesis (uzmanlık tezi), completed at Dr. Siyami Ersek Thoracic and Cardiovascular Surgery Education and Research Hospital in 2007. At the time of completion, prevailing academic appointment criteria in Turkey did not require or incentivize the publication of residency theses in peer-reviewed journals; consequently, this work remained unpublished for an extended period. The clinical data and core findings are original and unchanged from the thesis. For the present submission, the manuscript has been updated in accordance with current reporting standards (STROCSS 2025), and the reference list has been supplemented with recent landmark trials, systematic reviews, and meta-analyses published between 2019 and 2024 to contextualize the original findings within the current evidence base.

Competing interests

The authors declare no competing interests.