Ann Thorac Surg 2009;88:64-68. doi:10.1016/j.athoracsur.2009.03.042
© 2009 The Society of Thoracic Surgeons
Original Articles: Adult Cardiac
Survival of Cardiorespiratory Arrest After Coronary Artery Bypass Grafting or Aortic Valve Surgery
Dumbor L. Ngaage, MD, FRCS (C-Th)*,
Michael E. Cowen, FRCS
Department of Cardiothoracic Surgery, Cardiothoracic Centre, Castle Hill Hospital, Kingston-Upon-Hull, East Yorkshire, United Kingdom
Accepted for publication March 17, 2009.
* Address correspondence to Dr Ngaage, Department of Cardiothoracic Surgery, Castle Hill Hospital, Kingston-Upon-Hull, East Yorkshire, HU16 5JQ, United Kingdom (Email: dngaage{at}yahoo.com).
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Abstract
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Background: Study objectives were to (1) report the clinical profile of and outcome for patients who experience a cardiorespiratory arrest after coronary artery bypass grafting or aortic valve replacement, and (2) identify factors associated with improved probability of survival.
Methods: We identified 108 consecutive patients who had cardiorespiratory arrest after coronary artery bypass grafting or aortic valve replacement between April 1999 and June 2008. We studied the characteristics of arrests and survivors, and performed a multivariate logistic analysis to determine features associated with survival to hospital discharge.
Results: Cardiac arrest (n = 86) was more common than respiratory arrest (n = 13; unknown cause, n = 9). Cardiorespiratory arrest occurred with decreasing frequency from the day of surgery. Ventricular fibrillation or tachycardia was the dominant mechanism of cardiac arrest (70% versus 17% for asystole versus 13% for pulseless electrical activity), and the principal causes were postoperative myocardial infarction (n = 46; 53%) and tamponade or bleeding (n = 21; 24%). Resternotomy was performed in 45 patients (52%), cardiopulmonary bypass reinstituted in 14 (16%), and additional grafts constructed in 5 (6%). The causes of respiratory arrest were mainly pulmonary (n = 8) and neurologic (n = 5). Survival to hospital discharge was better for respiratory arrest (69%) than for cardiac arrest (50%). Older age, ejection fraction less than 0.30, and postoperative myocardial infarction decreased the probability of survival.
Conclusions: Ventricular fibrillation or tachycardia was the most common mechanism, and myocardial infarction, the predominant precipitating cause of cardiac arrest after coronary artery bypass grafting or aortic valve replacement. Despite aggressive resuscitation, outcome is poor. Young patients with good left ventricular function had a better probability of survival if they did not suffer a postoperative myocardial infarction.
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Introduction
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Cardiorespiratory arrest occurs infrequently during the early postoperative period after cardiac surgery, and portends poor prognosis. Studies report incidences between 1.4% and 2.7% [1, 2] with survival to hospital discharge of 30% to 80% [1–6]. The intensive care unit and wards with monitored beds, where cardiac patients are managed postoperatively, are better equipped to manage in-hospital cardiac arrest. Recent sternotomy in cardiac patients facilitates reopening for internal cardiac massage and correction of surgery-related causes of cardiac arrest, favorably influencing the outcome of cardiopulmonary resuscitation (CPR) [7]. Prompt institution of extracorporeal circulatory support with conventional bypass or extracorporeal membrane oxygenator have also been reported to improve prognosis [8–10]. For several reasons, however, these perceived advantages for a successful restoration of cardiorespiratory function with CPR in cardiac patients do not always translate to better survival to hospital discharge [11]. The heterogeneity of patients who experience cardiac arrest after cardiac surgery partly explains the wide variation in survival rates and limits the clinical applicability. Although most of these reports have concentrated on the techniques of CPR, data about determinants of survival to hospital discharge after cardiorespiratory arrest in cardiac patients are lacking.
In this retrospective study, we report the clinical profile and survival to hospital discharge for patients who had cardiorespiratory arrest after coronary artery bypass grafting (CABG) or aortic valve replacement (AVR), and by comparing survivors with nonsurvivors and further testing the independent associations of disparate variables, we identified favorable characteristics for surviving cardiorespiratory arrest after CABG or AVR.
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Patients and Methods
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We identified all patients who experienced cardiac or respiratory arrest after CABG or AVR from April 1, 1999, through June 30, 2008, from the cardiothoracic surgery database of our institution, and reviewed patient charts to collect the necessary data. Preoperative variables, namely demographic data, presenting symptoms, past medical and surgical history, comorbidities, and angiographic and echocardiographic findings, were collated. Operative details and postoperative complications were also retrieved. The characteristics of cardiorespiratory arrests, such as type, mechanism, cause, postoperative day of occurrence, frequency of episodes, resuscitative measures, and hospital outcome, were obtained as well. Patients operated on for infective endocarditis (n = 3) and those who had brief episodes of asystole as a result of disconnection of temporary pacing (n = 4) and responded instantly to recommencement of cardiac pacing were excluded. A total of 108 patients met the criteria and constitute the study group. The medical and ethics committee of our hospital approved this study and waived individual patient consent.
Cardiopulmonary resuscitation was conducted according to the Advanced Trauma Life Support protocol. When closed CPR did not restore cardiopulmonary function, or an anatomic defect was suspected, resternotomy was performed and further intervention with or without cardiopulmonary bypass was initiated. Transesophageal echocardiography, which is readily available in the intensive care unit, was often used to investigate the cause of arrest and to guide management during CPR. Where necessary, intraaortic balloon pump or ventricular assist device was inserted for continued hemodynamic support.
Statistical analysis was performed using the Statistical Package for the Social Sciences (SPSS) version 15.0 for Windows (SPSS Inc, Chicago, IL). Quantitative variables are reported as percentages and compared between the groups using Pearson's 
2 test, whereas qualitative variables are reported as median with the 25th and 75th percentiles as interquartile range and compared between the survivors and nonsurvivors of cardiac arrest using the Mann-Whitney U test. Patient characteristics and perioperative variables (Appendix) were screened for univariate associations with in-hospital death after CABG or AVR and a cardiorespiratory arrest, and covariates with some evidence of univariate associations (p < 0.1) were included in a backward, stepwise, multifactorial logistic regression model. A two-sided probability value of less than 0.05 was considered significant.
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Results
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Of 7,209 patients who underwent CABG or AVR during the study period, 108 (1.5%) experienced a cardiorespiratory arrest. The median age of the 108 patients was 72 years (range, 47 to 87 years). Patient characteristics are displayed in Table 1. Previous cardiac surgeries in 9 patients (8%) were CABG (n = 8) and valve surgery (n = 1). The median predicted operative risk of patients by additive European System for Cardiac Operative Risk Evaluation (EuroSCORE) was 6% (interquartile range, 4% to 8%). Operation was performed using cardiopulmonary bypass in 95% (n = 103) of patients, and the principal intraoperative myocardial preservation strategy was blood cardioplegia (n = 62; 57%); cross-clamp fibrillatory arrest was used in 41 patients (38%).
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Table 1 Clinical Characteristics of Patients Who Developed Cardiorespiratory Arrest After Coronary Artery Bypass Grafting or Aortic Valve Replacement
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Characteristics of Arrests
Cardiorespiratory arrest occurred with the highest frequency on the day of surgery and declined progressively during hospital stay (Fig 1). Cardiac arrest (n = 86; 80%) was more common than respiratory arrest (n = 13; 12%); type of arrest was unknown in 9 patients (8%). Twenty-two patients (20%) had multiple arrests.
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Fig 1. Relationship between the number of patients who experienced cardiorespiratory arrest and the postoperative day after coronary artery bypass or aortic valve replacement.
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For cardiac arrest (n = 86), postoperative ventricular tachycardia or fibrillation was the dominant mechanism (n = 60; 70%) followed by asystole (n = 15; 17%) and pulseless electrical activity (n = 11; 13%). Cardiac arrest was precipitated by postoperative myocardial infarction in the majority of patients (n = 46; 53%). Other causes were cardiac tamponade or bleeding (n = 21; 24%), complete heart block (n = 4; 5%), and hypokalemia (n = 5; 6%); in 10 patients (12%), the cause was unknown. Cardiopulmonary resuscitation included resternotomy in 45 patients (52%), reinstitution of cardiopulmonary bypass in 14 (16%), and regrafting of ischemic territories in 5 (6%). Intraaortic balloon pump was used in 39 (45%) and ventricular assist device in 2 patients (2%). Survival to hospital discharge after cardiac arrest was 50% (n = 43).
Respiratory arrest was primarily attributable to pulmonary causes (n = 8) such as adult respiratory distress syndrome and exacerbation of chronic obstructive pulmonary disease, and neurologic causes (n = 4) such as stroke and narcosis, especially soon after extubation. Survival to hospital discharge after respiratory arrest was 69% (n = 9).
The morbidity in survivors of cardiorespiratory arrest, shown in Table 2, is characterized by acceptable incidences of mechanical and infective sternal wound complications, but a prolonged hospital stay, up to 113 days (median, 10 days). Neurologic dysfunction was observed in 9 patients (17%), but only 1 (2%) was discharged with neurologic deficit. Renal replacement therapy was required in 3 patients (6%).
Features Associated With Survival of Cardiorespiratory Arrest After Coronary Artery Bypass Grafting or Aortic Valve Replacement
The clinical characteristics and operative outcome are compared between survivors and nonsurvivors of cardiorespiratory arrest in Table 3. Significant differences between the two groups included younger age, lower prevalence of preoperative stroke, lower predicted operative risk, and lower incidence of postoperative myocardial infarction among survivors.
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Table 3 Differences in Clinical Characteristics Between Survivors and Nonsurvivors of Cardiorespiratory After Coronary Artery Bypass Grafting or Aortic Valve Surgery
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The overall survival to hospital discharge after cardiorespiratory arrest after CABG or AVR was 50% (n = 54), and the majority of the patients died of cardiac causes (n = 37; 69%). Other causes of death were respiratory (n = 5; 9%), neurologic (n = 3; 6%), and multiorgan failure (n = 2; 4%). Postoperative myocardial infarction (odds ratio [OR], 4.75; 95% confidence interval [CI], 2.12 to 10.71; p < 0.0001), ejection fraction less than 0.30 (OR, 2.34; 95% CI, 1.07 to 5.13; p = 0.03), age (OR, 1.05; 95% CI, 1.00 to 1.10; p = 0.05), respiratory arrest (OR, 0.67; 95% CI, 0.55 to 0.86; p = 0.06), cardiopulmonary bypass duration (OR, 1.01; 95% CI, 1.00 to 1.02; p = 0.06); previous stroke (OR, 2.84; 95% CI, 0.83 to 9.70; p = 0.08), and body mass index (OR, 0.94; 95% CI, 0.86 to 1.02; p = 0.09) exhibited univariate associations with in-hospital mortality. However, the risk factors for in-hospital mortality after CABG or AVR and cardiac arrest by multivariate analysis were postoperative myocardial infarction (OR, 6.97; 95% CI, 2.55 to 19.07; p < 0.0001), ejection fraction less than 0.30 (OR, 5.77; 95% CI, 1.55 to 21.42; p = 0.009), age in years (OR, 1.08; 95% CI, 1.02 to 1.15; p = 0.01), and cardiopulmonary bypass duration in minutes (OR, 1.02; 95% CI, 1.01 to 1.04; p = 0.006).
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Comment
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This study shows that cardiorespiratory arrest is not common after CABG or AVR, tends to occur most frequently within 24 hours of surgery, and is associated with high morbidity and mortality. Cardiac arrest had a slightly worse outcome compared with respiratory arrest. Our finding of a 50% survival to hospital discharge after cardiac arrest is consistent with most other studies [1, 2, 5, 6], that report survival rates between 30% and 56% despite aggressive resuscitation with reinstitution of cardiopulmonary bypass, intraaortic balloon pump, and left ventricular assist device. There are very few studies reporting better survival. A small study by Anthi and associates [3] reported a survival of 79% in a select group of 29 young and stable patients who had adequate cardiac output and were receiving minimal inotropic support yet unexpectedly experienced cardiac arrest on the day of surgery. El-Banayosy and colleagues [4] also reported a survival of 70% in 113 patients who experienced cardiac arrest after cardiac surgery. These studies, however, were limited to early postoperative cardiac arrests, mostly in the setting of the intensive care unit. Close continuous monitoring characteristic of early postoperative management after cardiac surgery enables detection of pre-arrest conditions and facilitates a quick response. In general CPR is more often successful for arrests in the intensive care [12, 13] compared with ward arrests [14, 15]. Our study has the advantage of investigating arrests throughout the patients' hospitalization and is therefore better applicable in contemporary practice.
The present study shows that the principal causes of cardiac arrest after CABG or AVR were morphologic complications such as postoperative myocardial infarction and cardiac tamponade or bleeding, and not biochemical derangements such as hypokalemia. This lends credence to the argument [13, 16] in support of prompt reopening, which allows for internal cardiac massage (to improve organ perfusion), correction of mechanical defects, and provision of mechanical hemodynamic support when necessary. This approach does not appear to significantly increase the incidence of sternal wound complications as this study and other series [10] have shown. Among the precipitating causes of cardiac arrest, postoperative myocardial infarction had the worst prognosis. In the setting of recent cardiac surgery, further compromise of cardiac function owing to loss of viable myocardium substantially diminishes the probability of survival, and was the strongest distinguishing feature between survivors and nonsurvivors.
During CPR it is sometimes difficult to determine how far to escalate resuscitation and when to call off the procedure. The identification of subsets of patients with a good prospect of successful outcome would facilitate effective and efficient resuscitation. The present study suggests that successful CPR is more likely for respiratory arrests, and cardiac arrest not associated with postoperative myocardial infarction, in younger patients with good ejection fraction and low predicted operative risk. In general, elderly patients do not do well after cardiorespiratory arrest. Elshove-Bolk and colleagues [17] reported a survival to hospital discharge of 17% for resuscitation of nonsurgical elderly patients who experienced a cardiorespiratory arrest. As a result, the elderly are more likely to have a do-not-resuscitate order [1] and a less aggressive CPR than young patients. Although some reports have shown that success of resuscitation is age-related and questioned the rationale of CPR in the elderly, others have found no difference in survival to discharge between elderly and young patients [1], and cost and quality-of-life analyses have shown CPR to be effective in octogenarians [18].
The sample size precluded the stratification by age to identify age groups with the worse prognosis, so even though advancing age was a risk factor for in-hospital death, resuscitation should not be perfunctory for a specific group of patients especially as the average age of cardiac patients continues to rise. Other study limitations include the lack of data about the promptness of CPR, and criteria and timing of resternotomy and internal cardiac massage; variables that are better studied prospectively.
Cardiorespiratory arrest occurs with declining frequency from the day of CABG or AVR. Ventricular fibrillation or tachycardia is the predominant mechanism, and postoperative myocardial infarction, the most common cause of cardiac arrest. Despite aggressive closed and open CPR with mechanical cardiac support, we observed a 50% survival to hospital discharge for cardiac arrest. Young patients with good left ventricular function and with low operative risk had a higher probability of surviving a cardiac arrest after surgery, especially if they had not experienced a myocardial infarction postoperatively. Respiratory arrest had a relatively better outcome. Prospective studies are needed to determine optimal resuscitation algorithms for the postoperative cardiac patient.
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Appendix
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Categorical Variables
- Sex (male, female)
- Previous cardiac surgery (yes, no)
- Ejection fraction (>0.50, 0.30–0.50, <0.30)
- Type of surgery (CABG, AVR, CABG+AVR)
- Priority of surgery (elective, urgent, emergency)
- Type of arrest (cardiac, respiratory)
- Mechanism of cardiac arrest (ventricular fibrillation or tachycardia, asystole, pulseless electrical activity)
- Cause of arrest (postoperative myocardial infarction, cardiac tamponade, complete heart block)
- Multiple arrests (yes, no)
- Resternotomy (yes, no)
- Re-institution of cardiopulmonary bypass (yes, no)
- Intra-aortic balloon pump/ventricular assist device
- Regrafting
- Postoperative myocardial infarction
Continuous Variables
- Age (years)
- Duration of cardiopulmonary bypass (minutes)
- Duration of aortic cross-clamp (minutes)
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References
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- el-Banayosy A, Brehm C, Kizner L, et al. Cardiopulmonary resuscitation after cardiac surgery: a two-year study J Cardiothorac Vasc Anesth 1998;12:390-392.[Medline]
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Abstract
Introduction
