European Journal of Cardiovascular Medicine

Compared to elective coronary artery bypass grafting, urgent CABG has a greater death rate. For cardiac surgeons, treating patients having emergency coronary artery bypass grafting presents a distinct and dangerous patient group.

Globally, acute coronary syndrome (ACS) is frequently associated with mortality, hospitalization, and morbidity [1]. It encompasses a range of clinical disorders linked to reduced blood flow to the cardiac tissue through the coronary arteries [1]. ST-elevation myocardial infarction (STEMI), non-ST-elevation myocardial infarction (NSTEMI), or unstable angina are caused by a lack of blood flow [2]. The main cause of ACS is atherosclerosis, which is often brought on by acute thrombosis brought on by a ruptured or eroded atherosclerotic plaque, either with or without concurrent vasoconstriction that results in an abrupt and severe decrease in blood flow [3].

Many patients may require urgent revascularization by percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) due to ongoing ischemia [4]. CABG offers a survival advantage compared with medical therapy for life- threatening situations as unstable angina and left ventricular (LV) dysfunction [5]. Multiple studies were conducted to compare CABG and PCI with drug-eluting stents in ACS patients [6]. Despite the ongoing progress in transcatheter procedures these studies reported that CABG significantly reduces the risk of death from any cause, myocardial infarction (MI), or stroke, compared to PCI with drug-eluting stents, especially in patients with three-vessel disease. According to the Society of Thoracic Surgeons (STS), elective CABG refers to the patient's cardiac function that has been stable in the days or weeks before the operation. The procedure could be deferred without an increased risk of compromised cardiac outcome. However, urgent CABG is performed to minimize the chance of further clinical deterioration in cases, such as congestive heart failure, acute MI, and unstable angina with intravenous nitroglycerin. Indications for CABG in ACS are still controversial.  Treatment for patients with ACS is coronary revascularization. Historically, this was achieved with coronary artery bypass grafting (CABG); however, the advent of percutaneous coronary intervention (PCI) over 30 years ago brought about an increase in PCI and a decrease in CABG during those decades by 5% per year. Today, more than 395,000 CABG procedures are performed annually in the United States. A small proportion of these procedures are performed in emergency situations, most often because of ongoing ischemia, angiographic accidents, multivessel disease, or anatomic unsuitability for PCI. Emergency CABG is associated with significantly higher adverse outcomes, including death, when compared with elective CABG.

Audit Design: Retrospective Observational Audit

Audit setting: Department of CTVS, Peerless Hospital and B K Roy Research Centre Limited, Kolkata

Audit duration: December 2022 – March 2024

Audit Size: 100 patients

Inclusion Criteria

• All patients with ACS with failed PCI attempt & need for urgent revascularization
• All patients with ACS with need for immediate revascularization but not eligible for PCI as per guidelines
• All patients with Critical CAD not eligible for ACS

Exclusion Criteria

• All patients eligible for elective CABG

Statistical Analysis:

For statistical analysis, data were initially entered into a Microsoft Excel spreadsheet and then analyzed using SPSS (version 27.0; SPSS Inc., Chicago, IL, USA) and GraphPad Prism (version 5). Numerical variables were summarized using means and standard deviations, while categorical variables were described with counts and percentages. Two-sample t-tests, which compare the means of independent or unpaired samples, were used to assess differences between groups. Paired t-tests, which account for the correlation between paired observations, offer greater power than unpaired tests. Chi-square tests (χ² tests) were employed to evaluate hypotheses where the sampling distribution of the test statistic follows a chi-squared distribution under the null hypothesis; Pearson's chi-squared test is often referred to simply as the chi-squared test. For comparisons of unpaired proportions, either the chi-square test or Fisher’s exact test was used, depending on the context. To perform t-tests, the relevant formulae for test statistics, which either exactly follow or closely approximate a t-distribution under the null hypothesis, were applied, with specific degrees of freedom indicated for each test. P-values were determined from Student's t-distribution tables. A p-value ≤ 0.05 was considered statistically significant, leading to the rejection of the null hypothesis in favour of the alternative hypothesis. 

Table 1: Comparison of the baseline characteristics of both groups

Table 2: comparison between the preoperative clinical angiographic, echocardiographic and risk score data of both groups

The mean age of the patients in the urgent group was 56.55 ± 12.44 (mean± s.d.). The mean age of the patients in the elective group was 61.06 ± 7.32 (mean± s.d.). The group's mean age distribution showed statistically significant differences (p=0.036). There were 14 (28) female patients and 36 (72) male patients in the urgent group. Twelve (24) and 39 (78) of the patients in the elective group were female. Sex and group associations were not statistically significant (p=0.22). Thirty-two (64) participants in the urgent group had diabetes mellitus. Twenty-eight (56) participants in the elective group had diabetes mellitus. There was no statistically significant difference between the group and having diabetes mellitus (p=0.27). 37 (74) individuals in the urgent group had hypertension. Twenty-eight (56) participants in the elective group had hypertension. The group and having hypertension were statistically significantly associated (p=0.03). Thirty-odd individuals in the Urgent group had dyslipidemia. Twelve (24) participants in the elective group had dyslipidemia. Dyslipidemia and Group exhibited a statistically significant association (p=0.001). Of the patients in the Urgent group, twelve were obese. Seventeen patients in the elective group were obese. There was no statistically significant relationship between obesity and group (p=0.41). There were twenty-two (44) smokers in the urgent group. There were thirteen (26) smokers in the elective group. There was a statistically significant correlation between smoking and group (p=0.046). A family history was present in 16 (32) participants in the urgent group. Out of the 22 patients in the elective group, 11 had a family history. There was no statistically significant correlation (p=0.181) between family history and group. Four (8) individuals in the Urgent group had impaired renal function. Renal dysfunction affected six (12) participants in the elective group. No statistically significant relationship was seen between renal impairment and group (p=0.37). 16 individuals (8 with chronic pulmonary illness) were in the urgent group. Eight individuals with chronic pulmonary illness were in the elective group. There was no statistically significant correlation (p=0.262) between chronic lung disease and group. Peripheral vascular disease was seen in ten (20) participants in the urgent group. In Elective group, 7 (14) patients had Previous peripheral vascular disease. Association of Previous peripheral vascular disease with Group was not statistically significant (p=0.245). In Urgent group, 4 (8) patients had Previous cerebrovascular accidents. In Elective group, 4 (8) patients had Previous cerebrovascular accidents. Association of Previous cerebrovascular accidents with Group was not statistically significant (p=0.511).

In Urgent group, 9 (18) patients had Unstable Angina. In Elective group, 17 (34) patients had Unstable Angina. Association of Unstable Angina with Group was statistically significant (p=0.001). In Urgent group, 22 (44) patients had Heart failure class III/IV. In Elective group, 7 (14) patients had Heart failure class III/IV. Association of Heart failure class III/IV with Group was statistically significant (p=0.002). In Urgent group, 29 (58) patients had Angina class III/IV. In Elective group, 8 (16) patients had Angina class III/IV. Association of Angina class III/IV with Group was statistically significant (p=0.001). In Urgent group, 7 (14) patients had Inotropes. Association of Inotropes with Group was statistically significant (p=0.006). In Urgent group, 35(70) patients had Vasodilators. Association of Vasodilators with Group was statistically significant (p<.001). In Urgent group, 3 (6) patients had Intra-aortic balloon pump. Association of Intra-aortic balloon pump with Group was not statistically significant (p=0.121).

In Urgent group, 21 (42) patients had Left main. In Elective group, 4 (8) patients had Left main. Association of Left main with Group was statistically significant (p<.001). In Urgent group, 26 (52) patients had Left main equivalent n. In Elective group, 16 (32) patients had Left main equivalent n. Association of Left main equivalent n with Group was not statistically significant (p=0.068). In Elective group, 2 (4) patients had Single vessel disease n. Association of Single vessel disease n with Group was not statistically significant (p=0.25). In Urgent group, 8 (16) patients had Double vessel disease n. In Elective group, 5 (10) patients had Double vessel disease n. In Urgent group, 42 (84) patients had Triple vessel disease. In Elective group, 43 (86) patients had Triple vessel disease. A family history was present in 16 (32) participants in the urgent group. Out of the 22 patients in the elective group, 11 had a family history. There was no statistically significant correlation (p=0.181) between family history and group. 4 (8) individuals in the Urgent group had impaired renal function. Renal dysfunction affected six (12) participants in the elective group. No statistically significant relationship was seen between renal impairment and group (p=0.37). 16 individuals (8 with chronic pulmonary illness) were in the urgent group. Eight individuals with chronic pulmonary illness were in the elective group. There was no statistically significant correlation (p=0.262) between chronic lung disease and group. Peripheral vascular disease was seen in 10 (20) participants in the urgent group.

In Urgent group, the mean Cardiac Index (mean± s.d.) of patients was 2.55 ± .31. In Elective group, the mean Cardiac Index (mean± s.d.) of patients was 3.06 ± .21. Distribution of mean Cardiac Index with group was statistically significant (p<.001). In Urgent group, the mean Cardiac Output (mean± s.d.) of patients was 4.51 ± .75. In Elective group, the mean Fresh frozen plasma units (mean± s.d.) of patients was 4.92 ± 3.54. Distribution of mean Fresh frozen plasma units with group was statistically significant (p<.001). In Urgent group, the mean Platelet units (mean± s.d.) of patients was 4.96 ± 3.44. In Elective group, the mean Platelet units (mean± s.d.) of patients was 3.74 ± 3.79. Distribution of mean Platelet units with group was not statistically significant (p=0.091). In Urgent group, the mean Drainage ml (mean± s.d.) of patients was 1451.4 ± 587.0. Association of Atrial Fibrillation with Group was not statistically significant (p=0.5). In Urgent group, 13 (26) patients had Superficial wound infection. In Elective group, 7 (14) patients had Superficial wound infection. Association of Superficial wound infection with Group was not statistically significant (p=0.105). In Urgent group, 7 (14) patients had Deep sternal wound infection. In Elective group, 3 (6) patients had Deep sternal wound infection. Association of Deep sternal wound infection with Group was not statistically significant (p=0.159). In Urgent group, 5 (10) patients had Rewiring. In Elective group, 2 (4) patients had Rewiring. Association of Deep sternal wound infection with Group was not statistically significant (p=0.5). In Urgent group, 4 (8) patients had Exploration for bleeding. In Elective group, 1 (2) patient had Exploration for bleeding. Association of Exploration for bleeding with Group was not statistically significant (p=0.181). In Urgent group, 8 (16) patients had Prolonged ventilation. In Elective group, 1 (2) patient had Prolonged ventilation. Association of Prolonged ventilation with Group was statistically significant (p=0.011). In Urgent group, 2 (4) patients had Pneumonia. In Elective group, 1 (2) patient had Pneumonia. Association of Pneumonia with Group was not statistically significant (p=0.5). In Urgent group, 1 (2) patient had acute respiratory distress syndrome. Association of Acute respiratory distress syndrome with Group was not statistically significant (p=0.5). In Urgent group, 5 (10) patients had Pleural effusion. In Elective group, 7 (14) patients had Renal impairment. Association of Renal impairment with Group was not statistically significant (p=1). In Urgent group, 4 (8) patients had Dialysis. In Elective group, 1 (2) patient had Dialysis. Association of Dialysis with Group was not statistically significant (p=0.181). In Urgent group, 5 (10) patients had Readmission. In Elective group, 2 (4) patients had Readmission. Association of Readmission with Group was not statistically significant (p=0.218).

In contrast to the elective CABG group, we observed in our study that urgent CABG patients were younger and smoked and had much higher rates of dyslipidemia. Sex, diabetes mellitus, renal impairment, and chronic lung disease rates, however, were similar in both groups. However, Herlitz et al. [7] found that patients in the urgent group were younger and more likely to have chronic pulmonary illness, diabetes, hypertension, and renal impairment. Weiss et al. [8] examined data from 40159 patients who had CABG while they were hospitalized and came to the same conclusions.

Upon doing a univariate analysis of the surgical and postoperative data, we found that the mortality group had higher CPB and total operative times than the survival group. This might be explained by the low cardiac output condition and the four patients in our research who were unable to wean off of their bypass or get back on it. Additionally, we harvested the internal mammary artery in a few individuals following the development of CPB. Furthermore, hemostasis took longer than expected, although there was no difference in the ischemia duration between the two groups when it came to the quantity of grafts. As a result, we discovered that a longer CPB duration was linked to early death (p =.004).

Prospective research was carried out by Glaser et al. to determine if gender influences the results of early invasive treatment. 1114 patients were allocated to the group using the early invasive method. Compared to enrolled males, females made up one-third of the patient population, were often older, and had higher blood pressure. In the early invasive group, almost 17% of recruited women had fatal consequences. Their findings, however, did not reveal a statistically significant difference in the mortality and MI rates at six months between the two genders [9].

Preoperative EF was significantly lower in the urgent group, compared to the elective group. This can be attributed to the preoperative critical ischemia and the fact that most patients in the urgent group had STEMI; some of these patients needed preoperative inotropic support and IABP insertion. Abd-Alaal et al. [10] reported similar results when he studied emergency, urgent and elective surgical revascularization after MI in 278 patients.

In our study, the longer ventilation time in the mortality group can be explained by the finding that the mortality rate was highest in patients with low cardiac output state on Inotropes and IABP. Moreover, the longer ICU stay in the same group can be attributed to the development of major complication as renal impairment, pneumonia, arrhythmia and perioperative MI.

According to Lazar et al. [11], infections, strokes, MI, respiratory failure, and arrhythmias (particularly atrial fibrillation) are the most frequent reasons for extended hospital stays.

We found that the mortality group had substantially lower cardiac output and cardiac index than the survival group by univariate analysis of postoperative cardiac index and cardiac output in connection to mortality. This was to be expected, as in our study, low cardiac output status accounted for 50% of deaths.

Our findings confirm that low preoperative EF is an independent risk factor of mortality. Although female sex, preoperative higher NYHA class, left main disease and preoperative use of IABP had significant associations with increased mortality in the univariate analysis, they were not proven as independent risk factors for mortality in the multivariate analysis.

The DANAMI trial was the first study to show a significant benefit of revascularization in patients with suspected acute myocardial infarction. This study reported that the invasive strategy (CABG) in patients with inducible ischemia after MI was associated with a reduction in recurrent infarction and admissions for unstable angina, as well as a reduction in the severity of angina. They concluded that invasive treatment results in a reduction in the incidence of re-infarction, fewer admissions due to unstable angina, less severity of stable angina, and less anti-ischemic treatment, compared with conservative treatment in post-MI patients with inducible ischemia [12].

A meta-analysis by Bavry et al. reported that after two years of follow-up, the rate of mortality in the early invasive group (4.9%) was less than the conservative group (6.5%). Moreover, their data suggest that revascularization may be the key determinant and not the timeliness of invasive therapy in improving late clinical outcomes [13]. The FRISC-II trial demon- strated that at the long term, the benefit of revascularization seems to outweigh any early adverse effects. In this trial, mortality and MI were both significantly decreased at one year from early invasive therapy despite a small excess in early MI [14].

It is worth mentioning that the timing of surgery is one of several factors that affect CABG outcomes. Other perioperative variables include body mass index [15], complexity of coronary lesions, and perioperative hemoglobin and glycemic control [16].

In conclusion, the outcomes of urgent coronary artery bypass grafting (CABG) can vary depending on several factors, including the patient's preoperative condition, the urgency of the surgery, and the presence of comorbidities. While urgent CABG is associated with higher risks compared to elective procedures, it often leads to significant improvements in cardiac function, symptom relief, and survival in patients with severe coronary artery disease. The success of the procedure largely depends on timely intervention, the expertise of the surgical team, and effective postoperative care. Despite the inherent risks, urgent CABG remains a crucial life-saving intervention for patients with acute coronary syndromes. 

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